O. Hamdaoui - Academia.edu (original) (raw)

Papers by O. Hamdaoui

Potato peel (PP) was used as a biosorbent to remove malachite green (MG) from aqueous solution un... more Potato peel (PP) was used as a biosorbent to remove malachite green (MG) from aqueous solution under various operating conditions. The effect of the experimental parameters such as initial dye concentration, biosorbent dose, initial pH, stirring speed, temperature, ionic strength and biosorbent particle size was investigated through a number of batch sorption experiments. The sorption kinetic uptake for MG by PP at various initial dye concentrations was analyzed by non-linear method using pseudo-first, pseudo-second and pseudo-nth order models. It was found that the pseudo-nth order kinetic model was the best applicable model to describe the sorption kinetic data and the order n of sorption reaction was calculated in the range from 0.71 to 2.71. Three sorption isotherms namely the Langmuir, Freundlich and Redlich-Peterson isotherms in their non-linear forms were applied to the biosorption equilibrium data. Both the Langmuir and Redlich-Peterson models were found to fit the sorption isotherm data well, but the Redlich-Peterson model was better. Thermodynamic parameters show that the sorption process of MG is endothermic and more effective process at high temperatures. The results revealed that PP is very effective for the biosorption of MG from aqueous solutions.

The dynamic adsorption of methylene blue (MB) by melon peel (MP) was studied in packed bed column... more The dynamic adsorption of methylene blue (MB) by melon peel (MP) was studied in packed bed columns. The values of column parameters were predicted as a function of flow rate and initial dye concentration. On evaluating the breakthrough curves, the adsorption isotherms of MB by MP were experimentally determined in batch conditions. The Langmuir model was found to fit the adsorption isotherm data well with a maximum adsorption capacity of 333.33 mg/g at 25˚C. A series of column tests using MP as a low-cost adsorbent were performed to determine the breakthrough curves with varying initial dye concentrations and flow rates. High bed height, low flow rate and high initial dye concentration were found to be the better conditions for maximum dye adsorption. To predict the breakthrough curves and to determine the characteristic parameters of the column useful for process design, four kinetic models namely Bohart and Adams, Clark, Wolborska, and Yoon and Nelson were applied to experimental data. All models were found suitable for describing the whole, or a definite part of the dynamic behavior of the column, with respect to flow rate and initial dye concentration. The initial segment of the breakthrough curve was not well fitted by the Wolborska model, while the whole breakthrough curve was well predicted by the Bohart and Adams, Clark, and the Yoon and Nelson models. The findings revealed that MP has a high adsorption potential, and it could be used to treat dye-containing effluents.

Ultrasonics Sonochemistry, 2015

A number of literature reports showed that argon provides a more sonochemical activity than polya... more A number of literature reports showed that argon provides a more sonochemical activity than polyatomic gases because of its higher polytropic ratio; whereas several recent studies showed that polyatomic gases, such as O₂, can compensate the lower bubble temperature by the self decomposition in the bubble. In this work, we show for the first time a numerical interpretation of these controversial reported effects. Computer simulations of chemical reactions inside a collapsing acoustic bubble in water saturated by different gases (Ar, O₂, air and N₂) have been performed for different frequencies (213-1100 kHz). In all cases, OH radical is the main powerful oxidant created in the bubble. Unexpectedly, the order of saturating gases toward the production rate of OH radical was strongly frequency dependent. The rate of production decreases in the order of Ar>O₂>air>N₂ for frequencies above 515 kHz, and Ar starts to lose progressively its first order to the following gases with a gradually decreasing of frequency below 515 kHz up to a final order of O₂>air∼N₂>Ar at 213 kHz. The analysis of chemical kinetic results showed a surprising aspect: in some cases, there exists an optimum bubble temperature during collapse at which the chemical yield is much higher than that of the maximum bubble temperature achieved in the bubble. On the basis of this, we have concluded that the lower sonochemical activity induced by Ar for frequencies below 515 kHz is mainly due to the forte consumption of radicals inside a bubble prior the complete collapse being reached.

Desalination and Water Treatment, 2014

Ultrasonics Sonochemistry, 2015

Knowledge of the number of active bubbles in acoustic cavitation field is very important for the ... more Knowledge of the number of active bubbles in acoustic cavitation field is very important for the prediction of the performance of ultrasonic reactors toward most chemical processes induced by ultrasound. The literature in this field is scarce, probably due to the complicated nature of the phenomena. We introduce here a relatively simple semi-empirical method for predicting the number of active bubbles in an acoustic cavitation field. By coupling the bubble dynamics in an acoustical field with chemical kinetics occurring in the bubble during oscillation, the amount of the radical species OH and HO2 and molecular H2O2 released by a single bubble was estimated. Knowing that the H2O2 measured experimentally during sonication of water comes from the recombination of hydroxyl (OH) and perhydroxyl (HO2) radicals in the liquid phase and assuming that in sonochemistry applications, the cavitation is transient and the bubble fragments at the first collapse, the number of bubbles formed per unit time per unit volume is then easily determined using material balances for H2O2, OH and HO2 in the liquid phase. The effect of ultrasonic frequency on the number of active bubbles was examined. It was shown that increasing ultrasonic frequency leads to a substantial increase in the number of bubbles formed in the reactor.

Ultrasonics Sonochemistry, 2015

Central events of ultrasonic action are the bubbles of cavitation that can be considered as power... more Central events of ultrasonic action are the bubbles of cavitation that can be considered as powered microreactors within which high-energy chemistry occurs. This work presents the results of a comprehensive numerical assessment of frequency and saturating gases effects on single bubble sonochemistry. Computer simulations of chemical reactions occurring inside a bubble oscillating in liquid water irradiated by an ultrasonic wave have been performed for a wide range of ultrasonic frequencies (213-1100 kHz) under different saturating gases (O 2 , air, N 2 and H 2 ). For O 2 and H 2 bubbles, reactions mechanism consisting in 25 reversible chemical reactions were proposed for studying the internal bubble-chemistry whereas 73 reversible reactions were taken into account for air and N 2 bubbles. The numerical simulations have indicated that radicals such as Å OH, H Å , HO 2 Å and O are created in the bubble during the strong collapse. In all cases, hydroxyl radical ( Å OH) is the main oxidant created in the bubble. The production rate of the oxidants decreases as the driving ultrasonic frequency increases. The production rate of Å OH radical followed the order O 2 > air > N 2 > H 2 and the order becomes more remarkable at higher ultrasonic frequencies. The effect of ultrasonic frequency on single bubble sonochemistry was attributed to its significant impact on the cavitation process whereas the effects of gases were attributed to the nature of the chemistry produced in the bubble at the strong collapse. It was concluded that, in addition to the gas solubility, the nature of the internal bubble chemistry is another parameter of a paramount importance that controls the overall sonochemical activity in aqueous solutions.

Journal of Industrial and Engineering Chemistry, 2014

Energy Procedia, 2012

A new, low-cost, available sorbent, cedar cone (CC), was tested for its ability to remove basic d... more A new, low-cost, available sorbent, cedar cone (CC), was tested for its ability to remove basic dye Rhodamine B (RhB) from aqueous solutions. Sorption kinetics of RhB from aqueous solution on CC were studied in a batch process. In order to understand the mechanisms of RhB sorption by CC, the models of Weber and Morris and Boyd were applied. It was found that For the intraparticle diffusion model the sorption of RhB by the CC is divided into three stages: (i) the instantaneous sorption or external surface sorption, (ii) the gradual sorption stage where intraparticle diffusion is the rate limiting and (iii) the final equilibrium stage where intraparticle diffusion starts to slow down due to the extremely low sorbate concentrations left in the solutions. The effects of operating conditions such as ionic strength, contact time and solution pH were studied. The results obtained show the ability of cedar cone for the elimination of RhB in aqueous solution. The ionic strength has no effect on the kinetics of sorption. The maximum sorption (4.55 mg g -1 ) was obtained at pH equal to 3. The contact time was estimated for 360 min. The sorption isotherms of RhB by the CC at different temperatures were studied. It was found that the isotherms showed the shape of type L, which means that there is no strong competition between the solvent and sorbate to occupy the sorption sites.

Ultrasonics Sonochemistry, 2009

This work describes the results of investigations carried out to examine the adsorption kinetics ... more This work describes the results of investigations carried out to examine the adsorption kinetics of 4-chlorophenol (4-CP) from aqueous solution containing tert-butyl alcohol (10%, v/v) onto granular activated carbon (GAC) in the presence of ultrasound of different high frequencies (516, 800 and 1660 kHz) and acoustic powers (15.2, 21.5, 31.1 and 38.3 W). The main objective of this study is to describe the mechanism of ultrasound-assisted adsorption rather than the enhancement of adsorption capacity. Sonochemical degradation of 4-CP was studied in the absence and presence of tert-butyl alcohol. The sonolysis of 4-CP is effectively inhibited by the addition of tert-butyl alcohol (10%, v/v) and very little 4-CP degradation occurs, indicating that little or no pyrolysis of the compound occurs. Without addition of tert-butyl alcohol, after 300 min and at 1660 kHz, the removal of 4-CP in the presence of ultrasound for an acoustic power of 38.3 W was nearly total (99%), but in the conventional method only 60% was eliminated. In this case, the removal of 4-CP by GAC in the ultrasound-assisted technique is due to both adsorption and ultrasonic degradation, but the removal by simple stirring is only due to adsorption, which makes a direct comparison unacceptable. In order to distinguish sonochemical degradation and adsorption of 4-CP onto GAC and to make an exact and practical comparison of the adsorption in the absence and presence of ultrasound, kinetic adsorption experiments were conducted using aqueous solution containing 10% (v/v) tert-butyl alcohol. The obtained results show that both adsorption rate and adsorbed amount were significantly enhanced and improved in the presence of ultrasound for all the studied frequencies and powers. The enhancement of adsorption is favored by increasing ultrasonic power. Adsorption kinetic data were modeled using the liquid-film mass transfer equation and intraparticle diffusion model. The values of the intraparticle diffusion coefficient obtained in the presence of ultrasound are greater than that obtained in the absence of ultrasound. In the initial period of adsorption, where external mass transfer is assumed to predominate, liquid-film mass transfer coefficients significantly increased by the assistance of ultrasound. These results indicate that ultrasound enhances the mass transport in the pores as well as across the boundary layer. This effect increased with increasing ultrasonic power for the three studied frequencies.

Ultrasonics Sonochemistry, 2009

In this work, the influence of CCl 4 on the sonochemical decolorization of anthraquinonic dye Aci... more In this work, the influence of CCl 4 on the sonochemical decolorization of anthraquinonic dye Acid Blue 25 (AB25) in aqueous medium was investigated using high frequency ultrasound (1700 kHz). This frequency, reputed ineffective, was tested in order to introduce the ultrasound waves with high frequency in the field of degradation or removal of dyes from wastewater, due to its limited use in this field, and to increase the application of high frequency ultrasound wave in the field of environmental protection. The effects of various parameters such as the concentration of CCl 4 , frequency (22.5 and 1700 kHz), solution pH, temperature and tert-butyl alcohol adding on the decolorization rate of AB25 was studied. The obtained results clearly demonstrated the significant intensification of AB25 decolorization in the presence of CCl 4 . The enhancement effect of CCl 4 increased by decreasing temperature and by increasing the CCl 4 concentration. The pH has a significant influence on the bleaching of dye both in the absence and presence of CCl 4 . The three investigated dosimeter methods (KI oxidation, Fricke reaction and H 2 O 2 production) well corroborate the improvement of the sonochemical effects in the presence of CCl 4 . The best sonochemical decolorization rate of AB25 in aqueous solution both in the absence and presence of CCl 4 is observed to occur at 1700 kHz compared to 22.5 kHz. The sonochemical oxidation of CCl 4 generates oxidizing species in the liquid phase that are highly beneficial for oxidation of hydrophilic and non-volatile pollutant, such as dyes, because they are less susceptible to free radical attack due to lower stability of the generated free radicals.

Ultrasonics Sonochemistry, 2008

The degradation of 4-chlorophenol (4-CP) in aqueous media by 516 kHz ultrasonic irradiation was i... more The degradation of 4-chlorophenol (4-CP) in aqueous media by 516 kHz ultrasonic irradiation was investigated in order to clarify the degradation mechanism. The degradation of concentrated 4-CP solution by means of ultrasound, UV irradiation and their combined application was also studied. The obtained results indicate that Å OH radical are the primary reactive species responsible for 4-CP ultrasonic degradation. Very little 4-CP degradation occurs if the sonolysis is carried out in the presence of the Å OH radical scavenger tert-butyl alcohol, also indicating that little or no pyrolysis of the compound occurs. The dominant degradation mechanism is the reaction of substrate with Å OH radicals at the gas bubble-liquid interface rather than high temperature direct pyrolysis in ultrasonic cavities. This mechanism can explain the lower degradation rate of the ionic form of 4-CP that is partly due to the rapid dissociation of Å OH radicals in alkaline solutions. The sonochemical destruction of concentrated 4-CP aqueous solution is obtained with low rate. Coupling photolysis with ultrasound irradiation results in increased efficiency compared to the individual processes operating at common conditions. Interestingly, the photosonochemical decomposition rate constant is greater than the additive rate constants of the two processes. This may be the result of three different oxidative processes direct photochemical action, high frequency sonochemistry and reaction with ozone produced by UV irradiation of air, dissolved in liquid phase because of the geyser effect of ultrasound streaming. Additionally, the photodecomposition, at 254 nm, of hydrogen peroxide produced by ultrasound generating Å OH radical can partly explain the destruction enhancement.

Ultrasonics Sonochemistry, 2014

Formation of highly reactive species such as Å OH, H Å , HO 2 Å and H 2 O 2 due to transient coll... more Formation of highly reactive species such as Å OH, H Å , HO 2 Å and H 2 O 2 due to transient collapse of cavitation bubbles is the primary mechanism of sonochemical reaction. The crucial parameters influencing the formation of radicals are the temperature and pressure achieved in the bubble during the strong collapse. Experimental determinations estimated a temperature of about 5000 K and pressure of several hundreds of MPa within the collapsing bubble. In this theoretical investigation, computer simulations of chemical reactions occurring in an O 2 -bubble oscillating in water irradiated by an ultrasonic wave have been performed for diverse combinations of various parameters such as ultrasound frequency (20-1000 kHz), acoustic amplitude (up to 0.3 MPa), static pressure (0.03-0.3 MPa) and liquid temperature (283-333 K). The aim of this series of computations is to correlate the production of Å OH radicals to the temperature and pressure achieved in the bubble during the strong collapse. The employed model combines the dynamic of bubble collapse in acoustical field with the chemical kinetics of single bubble. The results of the numerical simulations revealed that the main oxidant created in an O 2 bubble is Å OH radical. The computer simulations clearly showed the existence of an optimum bubble temperature of about 5200 ± 200 K and pressure of about 250 ± 20 MPa. The predicted value of the bubble temperature for the production of Å OH radicals is in excellent agreement with that furnished by the experiments. The existence of an optimum bubble temperature and pressure in collapsing bubbles results from the competitions between the reactions of production and those of consumption of Å OH radicals at high temperatures.

Ultrasonics Sonochemistry, 2013

Numerical simulation of chemical reactions inside an isolated spherical bubble of oxygen has been... more Numerical simulation of chemical reactions inside an isolated spherical bubble of oxygen has been performed for various ambient bubble radii at different frequencies and acoustic amplitudes to study the effects of these two parameters on the range of ambient radius for an active bubble in sonochemical reactions. The employed model combines the dynamic of bubble collapse with the chemical kinetics of single cavitation bubble. Results from this model were compared with some experimental results presented in the literature and good apparent trends between them were observed. The numerical calculations of this study showed that there always exists an optimal ambient bubble radius at which the production of oxidizing species at the end of the bubble collapse attained their upper limit. It was shown that the range of ambient radius for an active bubble increased with increasing acoustic amplitude and decreased with increasing ultrasound frequency. The optimal ambient radius decreased with increasing frequency. Analysis of curves showing optimal ambient radius versus acoustic amplitude for different ultrasonic frequencies indicated that for 200 and 300 kHz, the optimal ambient radius increased linearly with increasing acoustic amplitude up to 3 atm. However, slight minima of optimal radius were observed for the curves obtained at 500 and 1000 kHz.

Ultrasonics Sonochemistry, 2012

Sonochemical oxidation has been investigated as a viable advanced oxidation process (AOP) for the... more Sonochemical oxidation has been investigated as a viable advanced oxidation process (AOP) for the destruction of various pollutants in water. Ultrasonic irradiation generates Å OH radicals that can recombine, react with other gaseous species present in the cavity, or diffuse out of the bubble into the bulk liquid medium where they are able to react with solute molecules. The extent of degradation of an organic dye such as malachite green (MG) is limited by the quantity of hydroxyl radicals diffused from cavitation bubbles. In this work, the effect of bromide ions on sonolytic degradation of MG was investigated. The obtained results clearly demonstrated the considerable enhancement of sonochemical destruction of MG in the presence of bromide. No significant differences were observed in the presence of chloride and sulfate, excluding the salting-out effect. Positive effect of bromide ions, which increases with increasing bromide level and decreasing MG concentration, is due to the generation of dibromine radical anion (Br ÅÀ 2 ) formed by reaction of Br À with Å OH radicals followed by rapid complexation with another anion. The generated Br ÅÀ 2 radicals, reactive but less than Å OH, are likely able to migrate far from the cavitation bubbles towards the solution bulk and are suitable for degradation of an organic dye such as MG. Additionally, Br ÅÀ 2 radicals undergo radical-radical recombination at a lesser extent than hydroxyl radicals and would be more available than Å OH for substrate degradation, both at the bubble surface and in the solution bulk. This effect compensates for the lower reactivity of Br ÅÀ 2 compared to Å OH toward organic substrate. Addition of bromide to natural and sea waters induces a slight positive effect on MG degradation. In the absence of bromide, ultrasonic treatment for the removal of MG was promoted in complex matrices such as natural and sea waters.

Ultrasonics Sonochemistry, 2011

The sonolytic degradation of endocrine disrupting compound 4-cumylphenol (4-CyP) in aqueous solut... more The sonolytic degradation of endocrine disrupting compound 4-cumylphenol (4-CyP) in aqueous solution was investigated. The influence of operating parameters for sonication process such as 4-CyP initial concentration, frequency, power, pH, temperature and saturating gas was examined. The extent of degradation was inversely proportional to the initial substrate concentration. The rate of 4-CyP degradation was frequency dependent. The degradation rate increased proportionally with increasing ultrasonic power from 20 to 100 W and temperature in the range of 20-50°C. The most favorable degradation pH was acidic media. Destruction in the presence of saturating gas follows the order: argon > air > nitrogen. The 4-CyP degradation was inhibited in the presence of nitrogen gas owing to the free radical scavenging effect in vapor phase within the bubbles of cavitation. The ultrasonic degradation of 4-CyP was clearly promoted in the presence of bromide anions and the promoting effect on degradation increased with increasing bromide concentration. At low 4-CyP concentration (0.05 mg L À1 ), bicarbonate ion drastically enhanced the rate of 4-CyP degradation. Experiments conducted using pure and natural water demonstrated that the sonolytic treatment was more efficient in the natural water compared to pure water.

Ultrasonics Sonochemistry, 2003

The aim of this work is the evaluation of the effects of ultrasound on p-chlorophenol adsorption-... more The aim of this work is the evaluation of the effects of ultrasound on p-chlorophenol adsorption-desorption on granular activated carbon. Adsorption equilibrium experiments and batch kinetics studies were carried out in the presence and the absence of ultrasound at 21 kHz. Results indicate that the adsorption of p-chlorophenol determined in the presence of ultrasound is lower than the adsorption observed in the absence of ultrasound. Desorption of p-chlorophenol from activated carbon with and without the application of ultrasound was studied. The desorption rates were favoured by increased ultrasound intensity. This rise is more noticeable as temperature increases. The addition of ethanol or NaOH to the system causes an enhancement of the amount of p-chlorophenol desorbed, especially in the presence of ultrasound. A synergetic enhancement of the desorption rate was observed when ultrasonic irradiation was coupled with ethanol chemical regeneration.

Ultrasonics Sonochemistry, 2008

The dead needles of Aleppo pine (Pinus halepensis) were tested as a possible sorbent for the remo... more The dead needles of Aleppo pine (Pinus halepensis) were tested as a possible sorbent for the removal of malachite green from aqueous solutions in the absence and presence of ultrasound. Batch process was employed for sorption kinetic and equilibrium studies. Sorption experiments indicated that the sorption capacity was dependent of operating variables. Both the rate and the amount of malachite green sorption are markedly increased in the presence of the ultrasonic field. The dye removal with the assistance of ultrasound was enhanced with the increase of sorbate initial concentration and temperature, and with the decrease of sorbent dosage and ionic strength. The combination of stirring and ultrasound leads to an improvement of the removal of dye. The sorption kinetics was controlled by the intraparticle diffusion. The intraparticle diffusion coefficient increased 1.7 times in the presence of ultrasound and up to 3.6 times in the combined process. The sorption capacity, estimated according to the Freundlich model, indicates that ultrasound enhanced the sorption properties of the sorbent. The effect of ultrasound on the improvement of dye sorption is due to a variety of physical and mechanical effects as well as to thermal properties. The combination of ultrasound and stirring for the sorption process was shown to be of interest for the treatment of wastewaters contaminated with malachite green.

Ultrasonics Sonochemistry, 2010

The aim of this work was to study the emulsification assisted by ultrasonic probe (22.5 kHz) and ... more The aim of this work was to study the emulsification assisted by ultrasonic probe (22.5 kHz) and investigate the removal of copper(II) ions from aqueous solution using water-in-oil-in-water (W/O/W) emulsion liquid membrane process (ELM). The membrane was prepared by dissolving the extractant bis(2-ethylhexyl)phosphoric acid (D2EHPA) and the hydrophobic surfactant sorbitan monooleate (Span 80) in hexane (diluent). The internal phase consisted of an aqueous solution of sulfuric acid. Effects of operating parameters such as emulsification time, ultrasonic power, probe position, stirring speed, carrier (D2EHPA) and surfactant (Span 80) concentrations volume ratios of organic phase to internal striping phase and of external aqueous phase to membrane (W/O) phase, internal phase concentration and choice of diluent on the membrane stability were studied. With ultrasound, the W/O emulsion lifetime were much higher than those reported previously by mechanical agitation. The effect of carrier and Cu(II) initial concentration on the extraction kinetics was also investigated. Nearly all of the Cu(II) ions present in the continuous phase was extracted within a few minutes. Additionally, the influence of H 2 SO 4 concentration on the stripping efficiency was examined.

Ultrasonics, 2014

In this work, energy analysis of an oscillating isolated spherical bubble in water irradiated by ... more In this work, energy analysis of an oscillating isolated spherical bubble in water irradiated by an ultrasonic wave has been theoretically studied for various conditions of acoustic amplitude, ultrasound frequency, static pressure and liquid temperature in order to explain the effects of these key parameters on both sonochemistry and sonoluminescence. The Keller-Miksis equation for the temporal variation of the bubble radius in compressible and viscous medium has been employed as a dynamics model. The numerical calculations showed that the rate of energy accumulation, dE/dt, increased linearly with increasing acoustic amplitude in the range of 1.5-3.0 atm and decreased sharply with increasing frequency in the range 200-1000 kHz. There exists an optimal static pressure at which the power w is highest. This optimum shifts toward a higher value as the acoustic amplitude increases. The energy of the bubble slightly increases with the increase in liquid temperature from 10 to 60°C. The results of this study should be a helpful means to explain a variety of experimental observations conducted in the field of sonochemistry and sonoluminescence concerning the effects of operational parameters.

The Journal of Physical Chemistry A, 2007

In the present study, the sorption of cadmium from aqueous phase by wheat bran was investigated w... more In the present study, the sorption of cadmium from aqueous phase by wheat bran was investigated with and without the assistance of ultrasound. Kinetic data and sorption equilibrium isotherms were carried out in batch conditions. The influence of different operating parameters such as ultrasonic power, cadmium initial concentration, sorbent mass, temperature, and the combination of ultrasound and mechanical stirring on the kinetics of cadmium removal was studied. The obtained results show that the ultrasonic irradiation significantly enhances and improves the efficiency of the removal of cadmium, especially in the combined method. The sorption kinetic data were found to be well-represented by the pseudo-second-order rate equation, both in the absence and presence of ultrasound as well as in the combined process (stirring and ultrasonication). Ultrasonic power played a key role in the removal of cadmium. Equilibrium isotherm results could be well described by the Langmuir model both with and without the assistance of ultrasound. The effect of temperature on the sorption isotherms of cadmium in the absence and presence of ultrasound has been also studied and the thermodynamic parameters ∆G°, ∆H°, and ∆S°were determined. The monolayer sorption capacities were 51.81, 35.09, and 22.78 mg g -1 for experiments conducted by the combined process, in the presence of ultrasound, and in passive conditions, respectively. The combination ultrasound-stirring for the sorption process was shown to be of interest for the treatment of wastewaters contaminated with cadmium.

Potato peel (PP) was used as a biosorbent to remove malachite green (MG) from aqueous solution un... more Potato peel (PP) was used as a biosorbent to remove malachite green (MG) from aqueous solution under various operating conditions. The effect of the experimental parameters such as initial dye concentration, biosorbent dose, initial pH, stirring speed, temperature, ionic strength and biosorbent particle size was investigated through a number of batch sorption experiments. The sorption kinetic uptake for MG by PP at various initial dye concentrations was analyzed by non-linear method using pseudo-first, pseudo-second and pseudo-nth order models. It was found that the pseudo-nth order kinetic model was the best applicable model to describe the sorption kinetic data and the order n of sorption reaction was calculated in the range from 0.71 to 2.71. Three sorption isotherms namely the Langmuir, Freundlich and Redlich-Peterson isotherms in their non-linear forms were applied to the biosorption equilibrium data. Both the Langmuir and Redlich-Peterson models were found to fit the sorption isotherm data well, but the Redlich-Peterson model was better. Thermodynamic parameters show that the sorption process of MG is endothermic and more effective process at high temperatures. The results revealed that PP is very effective for the biosorption of MG from aqueous solutions.

The dynamic adsorption of methylene blue (MB) by melon peel (MP) was studied in packed bed column... more The dynamic adsorption of methylene blue (MB) by melon peel (MP) was studied in packed bed columns. The values of column parameters were predicted as a function of flow rate and initial dye concentration. On evaluating the breakthrough curves, the adsorption isotherms of MB by MP were experimentally determined in batch conditions. The Langmuir model was found to fit the adsorption isotherm data well with a maximum adsorption capacity of 333.33 mg/g at 25˚C. A series of column tests using MP as a low-cost adsorbent were performed to determine the breakthrough curves with varying initial dye concentrations and flow rates. High bed height, low flow rate and high initial dye concentration were found to be the better conditions for maximum dye adsorption. To predict the breakthrough curves and to determine the characteristic parameters of the column useful for process design, four kinetic models namely Bohart and Adams, Clark, Wolborska, and Yoon and Nelson were applied to experimental data. All models were found suitable for describing the whole, or a definite part of the dynamic behavior of the column, with respect to flow rate and initial dye concentration. The initial segment of the breakthrough curve was not well fitted by the Wolborska model, while the whole breakthrough curve was well predicted by the Bohart and Adams, Clark, and the Yoon and Nelson models. The findings revealed that MP has a high adsorption potential, and it could be used to treat dye-containing effluents.

Ultrasonics Sonochemistry, 2015

A number of literature reports showed that argon provides a more sonochemical activity than polya... more A number of literature reports showed that argon provides a more sonochemical activity than polyatomic gases because of its higher polytropic ratio; whereas several recent studies showed that polyatomic gases, such as O₂, can compensate the lower bubble temperature by the self decomposition in the bubble. In this work, we show for the first time a numerical interpretation of these controversial reported effects. Computer simulations of chemical reactions inside a collapsing acoustic bubble in water saturated by different gases (Ar, O₂, air and N₂) have been performed for different frequencies (213-1100 kHz). In all cases, OH radical is the main powerful oxidant created in the bubble. Unexpectedly, the order of saturating gases toward the production rate of OH radical was strongly frequency dependent. The rate of production decreases in the order of Ar>O₂>air>N₂ for frequencies above 515 kHz, and Ar starts to lose progressively its first order to the following gases with a gradually decreasing of frequency below 515 kHz up to a final order of O₂>air∼N₂>Ar at 213 kHz. The analysis of chemical kinetic results showed a surprising aspect: in some cases, there exists an optimum bubble temperature during collapse at which the chemical yield is much higher than that of the maximum bubble temperature achieved in the bubble. On the basis of this, we have concluded that the lower sonochemical activity induced by Ar for frequencies below 515 kHz is mainly due to the forte consumption of radicals inside a bubble prior the complete collapse being reached.

Desalination and Water Treatment, 2014

Ultrasonics Sonochemistry, 2015

Knowledge of the number of active bubbles in acoustic cavitation field is very important for the ... more Knowledge of the number of active bubbles in acoustic cavitation field is very important for the prediction of the performance of ultrasonic reactors toward most chemical processes induced by ultrasound. The literature in this field is scarce, probably due to the complicated nature of the phenomena. We introduce here a relatively simple semi-empirical method for predicting the number of active bubbles in an acoustic cavitation field. By coupling the bubble dynamics in an acoustical field with chemical kinetics occurring in the bubble during oscillation, the amount of the radical species OH and HO2 and molecular H2O2 released by a single bubble was estimated. Knowing that the H2O2 measured experimentally during sonication of water comes from the recombination of hydroxyl (OH) and perhydroxyl (HO2) radicals in the liquid phase and assuming that in sonochemistry applications, the cavitation is transient and the bubble fragments at the first collapse, the number of bubbles formed per unit time per unit volume is then easily determined using material balances for H2O2, OH and HO2 in the liquid phase. The effect of ultrasonic frequency on the number of active bubbles was examined. It was shown that increasing ultrasonic frequency leads to a substantial increase in the number of bubbles formed in the reactor.

Ultrasonics Sonochemistry, 2015

Central events of ultrasonic action are the bubbles of cavitation that can be considered as power... more Central events of ultrasonic action are the bubbles of cavitation that can be considered as powered microreactors within which high-energy chemistry occurs. This work presents the results of a comprehensive numerical assessment of frequency and saturating gases effects on single bubble sonochemistry. Computer simulations of chemical reactions occurring inside a bubble oscillating in liquid water irradiated by an ultrasonic wave have been performed for a wide range of ultrasonic frequencies (213-1100 kHz) under different saturating gases (O 2 , air, N 2 and H 2 ). For O 2 and H 2 bubbles, reactions mechanism consisting in 25 reversible chemical reactions were proposed for studying the internal bubble-chemistry whereas 73 reversible reactions were taken into account for air and N 2 bubbles. The numerical simulations have indicated that radicals such as Å OH, H Å , HO 2 Å and O are created in the bubble during the strong collapse. In all cases, hydroxyl radical ( Å OH) is the main oxidant created in the bubble. The production rate of the oxidants decreases as the driving ultrasonic frequency increases. The production rate of Å OH radical followed the order O 2 > air > N 2 > H 2 and the order becomes more remarkable at higher ultrasonic frequencies. The effect of ultrasonic frequency on single bubble sonochemistry was attributed to its significant impact on the cavitation process whereas the effects of gases were attributed to the nature of the chemistry produced in the bubble at the strong collapse. It was concluded that, in addition to the gas solubility, the nature of the internal bubble chemistry is another parameter of a paramount importance that controls the overall sonochemical activity in aqueous solutions.

Journal of Industrial and Engineering Chemistry, 2014

Energy Procedia, 2012

A new, low-cost, available sorbent, cedar cone (CC), was tested for its ability to remove basic d... more A new, low-cost, available sorbent, cedar cone (CC), was tested for its ability to remove basic dye Rhodamine B (RhB) from aqueous solutions. Sorption kinetics of RhB from aqueous solution on CC were studied in a batch process. In order to understand the mechanisms of RhB sorption by CC, the models of Weber and Morris and Boyd were applied. It was found that For the intraparticle diffusion model the sorption of RhB by the CC is divided into three stages: (i) the instantaneous sorption or external surface sorption, (ii) the gradual sorption stage where intraparticle diffusion is the rate limiting and (iii) the final equilibrium stage where intraparticle diffusion starts to slow down due to the extremely low sorbate concentrations left in the solutions. The effects of operating conditions such as ionic strength, contact time and solution pH were studied. The results obtained show the ability of cedar cone for the elimination of RhB in aqueous solution. The ionic strength has no effect on the kinetics of sorption. The maximum sorption (4.55 mg g -1 ) was obtained at pH equal to 3. The contact time was estimated for 360 min. The sorption isotherms of RhB by the CC at different temperatures were studied. It was found that the isotherms showed the shape of type L, which means that there is no strong competition between the solvent and sorbate to occupy the sorption sites.

Ultrasonics Sonochemistry, 2009

This work describes the results of investigations carried out to examine the adsorption kinetics ... more This work describes the results of investigations carried out to examine the adsorption kinetics of 4-chlorophenol (4-CP) from aqueous solution containing tert-butyl alcohol (10%, v/v) onto granular activated carbon (GAC) in the presence of ultrasound of different high frequencies (516, 800 and 1660 kHz) and acoustic powers (15.2, 21.5, 31.1 and 38.3 W). The main objective of this study is to describe the mechanism of ultrasound-assisted adsorption rather than the enhancement of adsorption capacity. Sonochemical degradation of 4-CP was studied in the absence and presence of tert-butyl alcohol. The sonolysis of 4-CP is effectively inhibited by the addition of tert-butyl alcohol (10%, v/v) and very little 4-CP degradation occurs, indicating that little or no pyrolysis of the compound occurs. Without addition of tert-butyl alcohol, after 300 min and at 1660 kHz, the removal of 4-CP in the presence of ultrasound for an acoustic power of 38.3 W was nearly total (99%), but in the conventional method only 60% was eliminated. In this case, the removal of 4-CP by GAC in the ultrasound-assisted technique is due to both adsorption and ultrasonic degradation, but the removal by simple stirring is only due to adsorption, which makes a direct comparison unacceptable. In order to distinguish sonochemical degradation and adsorption of 4-CP onto GAC and to make an exact and practical comparison of the adsorption in the absence and presence of ultrasound, kinetic adsorption experiments were conducted using aqueous solution containing 10% (v/v) tert-butyl alcohol. The obtained results show that both adsorption rate and adsorbed amount were significantly enhanced and improved in the presence of ultrasound for all the studied frequencies and powers. The enhancement of adsorption is favored by increasing ultrasonic power. Adsorption kinetic data were modeled using the liquid-film mass transfer equation and intraparticle diffusion model. The values of the intraparticle diffusion coefficient obtained in the presence of ultrasound are greater than that obtained in the absence of ultrasound. In the initial period of adsorption, where external mass transfer is assumed to predominate, liquid-film mass transfer coefficients significantly increased by the assistance of ultrasound. These results indicate that ultrasound enhances the mass transport in the pores as well as across the boundary layer. This effect increased with increasing ultrasonic power for the three studied frequencies.

Ultrasonics Sonochemistry, 2009

In this work, the influence of CCl 4 on the sonochemical decolorization of anthraquinonic dye Aci... more In this work, the influence of CCl 4 on the sonochemical decolorization of anthraquinonic dye Acid Blue 25 (AB25) in aqueous medium was investigated using high frequency ultrasound (1700 kHz). This frequency, reputed ineffective, was tested in order to introduce the ultrasound waves with high frequency in the field of degradation or removal of dyes from wastewater, due to its limited use in this field, and to increase the application of high frequency ultrasound wave in the field of environmental protection. The effects of various parameters such as the concentration of CCl 4 , frequency (22.5 and 1700 kHz), solution pH, temperature and tert-butyl alcohol adding on the decolorization rate of AB25 was studied. The obtained results clearly demonstrated the significant intensification of AB25 decolorization in the presence of CCl 4 . The enhancement effect of CCl 4 increased by decreasing temperature and by increasing the CCl 4 concentration. The pH has a significant influence on the bleaching of dye both in the absence and presence of CCl 4 . The three investigated dosimeter methods (KI oxidation, Fricke reaction and H 2 O 2 production) well corroborate the improvement of the sonochemical effects in the presence of CCl 4 . The best sonochemical decolorization rate of AB25 in aqueous solution both in the absence and presence of CCl 4 is observed to occur at 1700 kHz compared to 22.5 kHz. The sonochemical oxidation of CCl 4 generates oxidizing species in the liquid phase that are highly beneficial for oxidation of hydrophilic and non-volatile pollutant, such as dyes, because they are less susceptible to free radical attack due to lower stability of the generated free radicals.

Ultrasonics Sonochemistry, 2008

The degradation of 4-chlorophenol (4-CP) in aqueous media by 516 kHz ultrasonic irradiation was i... more The degradation of 4-chlorophenol (4-CP) in aqueous media by 516 kHz ultrasonic irradiation was investigated in order to clarify the degradation mechanism. The degradation of concentrated 4-CP solution by means of ultrasound, UV irradiation and their combined application was also studied. The obtained results indicate that Å OH radical are the primary reactive species responsible for 4-CP ultrasonic degradation. Very little 4-CP degradation occurs if the sonolysis is carried out in the presence of the Å OH radical scavenger tert-butyl alcohol, also indicating that little or no pyrolysis of the compound occurs. The dominant degradation mechanism is the reaction of substrate with Å OH radicals at the gas bubble-liquid interface rather than high temperature direct pyrolysis in ultrasonic cavities. This mechanism can explain the lower degradation rate of the ionic form of 4-CP that is partly due to the rapid dissociation of Å OH radicals in alkaline solutions. The sonochemical destruction of concentrated 4-CP aqueous solution is obtained with low rate. Coupling photolysis with ultrasound irradiation results in increased efficiency compared to the individual processes operating at common conditions. Interestingly, the photosonochemical decomposition rate constant is greater than the additive rate constants of the two processes. This may be the result of three different oxidative processes direct photochemical action, high frequency sonochemistry and reaction with ozone produced by UV irradiation of air, dissolved in liquid phase because of the geyser effect of ultrasound streaming. Additionally, the photodecomposition, at 254 nm, of hydrogen peroxide produced by ultrasound generating Å OH radical can partly explain the destruction enhancement.

Ultrasonics Sonochemistry, 2014

Formation of highly reactive species such as Å OH, H Å , HO 2 Å and H 2 O 2 due to transient coll... more Formation of highly reactive species such as Å OH, H Å , HO 2 Å and H 2 O 2 due to transient collapse of cavitation bubbles is the primary mechanism of sonochemical reaction. The crucial parameters influencing the formation of radicals are the temperature and pressure achieved in the bubble during the strong collapse. Experimental determinations estimated a temperature of about 5000 K and pressure of several hundreds of MPa within the collapsing bubble. In this theoretical investigation, computer simulations of chemical reactions occurring in an O 2 -bubble oscillating in water irradiated by an ultrasonic wave have been performed for diverse combinations of various parameters such as ultrasound frequency (20-1000 kHz), acoustic amplitude (up to 0.3 MPa), static pressure (0.03-0.3 MPa) and liquid temperature (283-333 K). The aim of this series of computations is to correlate the production of Å OH radicals to the temperature and pressure achieved in the bubble during the strong collapse. The employed model combines the dynamic of bubble collapse in acoustical field with the chemical kinetics of single bubble. The results of the numerical simulations revealed that the main oxidant created in an O 2 bubble is Å OH radical. The computer simulations clearly showed the existence of an optimum bubble temperature of about 5200 ± 200 K and pressure of about 250 ± 20 MPa. The predicted value of the bubble temperature for the production of Å OH radicals is in excellent agreement with that furnished by the experiments. The existence of an optimum bubble temperature and pressure in collapsing bubbles results from the competitions between the reactions of production and those of consumption of Å OH radicals at high temperatures.

Ultrasonics Sonochemistry, 2013

Numerical simulation of chemical reactions inside an isolated spherical bubble of oxygen has been... more Numerical simulation of chemical reactions inside an isolated spherical bubble of oxygen has been performed for various ambient bubble radii at different frequencies and acoustic amplitudes to study the effects of these two parameters on the range of ambient radius for an active bubble in sonochemical reactions. The employed model combines the dynamic of bubble collapse with the chemical kinetics of single cavitation bubble. Results from this model were compared with some experimental results presented in the literature and good apparent trends between them were observed. The numerical calculations of this study showed that there always exists an optimal ambient bubble radius at which the production of oxidizing species at the end of the bubble collapse attained their upper limit. It was shown that the range of ambient radius for an active bubble increased with increasing acoustic amplitude and decreased with increasing ultrasound frequency. The optimal ambient radius decreased with increasing frequency. Analysis of curves showing optimal ambient radius versus acoustic amplitude for different ultrasonic frequencies indicated that for 200 and 300 kHz, the optimal ambient radius increased linearly with increasing acoustic amplitude up to 3 atm. However, slight minima of optimal radius were observed for the curves obtained at 500 and 1000 kHz.

Ultrasonics Sonochemistry, 2012

Sonochemical oxidation has been investigated as a viable advanced oxidation process (AOP) for the... more Sonochemical oxidation has been investigated as a viable advanced oxidation process (AOP) for the destruction of various pollutants in water. Ultrasonic irradiation generates Å OH radicals that can recombine, react with other gaseous species present in the cavity, or diffuse out of the bubble into the bulk liquid medium where they are able to react with solute molecules. The extent of degradation of an organic dye such as malachite green (MG) is limited by the quantity of hydroxyl radicals diffused from cavitation bubbles. In this work, the effect of bromide ions on sonolytic degradation of MG was investigated. The obtained results clearly demonstrated the considerable enhancement of sonochemical destruction of MG in the presence of bromide. No significant differences were observed in the presence of chloride and sulfate, excluding the salting-out effect. Positive effect of bromide ions, which increases with increasing bromide level and decreasing MG concentration, is due to the generation of dibromine radical anion (Br ÅÀ 2 ) formed by reaction of Br À with Å OH radicals followed by rapid complexation with another anion. The generated Br ÅÀ 2 radicals, reactive but less than Å OH, are likely able to migrate far from the cavitation bubbles towards the solution bulk and are suitable for degradation of an organic dye such as MG. Additionally, Br ÅÀ 2 radicals undergo radical-radical recombination at a lesser extent than hydroxyl radicals and would be more available than Å OH for substrate degradation, both at the bubble surface and in the solution bulk. This effect compensates for the lower reactivity of Br ÅÀ 2 compared to Å OH toward organic substrate. Addition of bromide to natural and sea waters induces a slight positive effect on MG degradation. In the absence of bromide, ultrasonic treatment for the removal of MG was promoted in complex matrices such as natural and sea waters.

Ultrasonics Sonochemistry, 2011

The sonolytic degradation of endocrine disrupting compound 4-cumylphenol (4-CyP) in aqueous solut... more The sonolytic degradation of endocrine disrupting compound 4-cumylphenol (4-CyP) in aqueous solution was investigated. The influence of operating parameters for sonication process such as 4-CyP initial concentration, frequency, power, pH, temperature and saturating gas was examined. The extent of degradation was inversely proportional to the initial substrate concentration. The rate of 4-CyP degradation was frequency dependent. The degradation rate increased proportionally with increasing ultrasonic power from 20 to 100 W and temperature in the range of 20-50°C. The most favorable degradation pH was acidic media. Destruction in the presence of saturating gas follows the order: argon > air > nitrogen. The 4-CyP degradation was inhibited in the presence of nitrogen gas owing to the free radical scavenging effect in vapor phase within the bubbles of cavitation. The ultrasonic degradation of 4-CyP was clearly promoted in the presence of bromide anions and the promoting effect on degradation increased with increasing bromide concentration. At low 4-CyP concentration (0.05 mg L À1 ), bicarbonate ion drastically enhanced the rate of 4-CyP degradation. Experiments conducted using pure and natural water demonstrated that the sonolytic treatment was more efficient in the natural water compared to pure water.

Ultrasonics Sonochemistry, 2003

The aim of this work is the evaluation of the effects of ultrasound on p-chlorophenol adsorption-... more The aim of this work is the evaluation of the effects of ultrasound on p-chlorophenol adsorption-desorption on granular activated carbon. Adsorption equilibrium experiments and batch kinetics studies were carried out in the presence and the absence of ultrasound at 21 kHz. Results indicate that the adsorption of p-chlorophenol determined in the presence of ultrasound is lower than the adsorption observed in the absence of ultrasound. Desorption of p-chlorophenol from activated carbon with and without the application of ultrasound was studied. The desorption rates were favoured by increased ultrasound intensity. This rise is more noticeable as temperature increases. The addition of ethanol or NaOH to the system causes an enhancement of the amount of p-chlorophenol desorbed, especially in the presence of ultrasound. A synergetic enhancement of the desorption rate was observed when ultrasonic irradiation was coupled with ethanol chemical regeneration.

Ultrasonics Sonochemistry, 2008

The dead needles of Aleppo pine (Pinus halepensis) were tested as a possible sorbent for the remo... more The dead needles of Aleppo pine (Pinus halepensis) were tested as a possible sorbent for the removal of malachite green from aqueous solutions in the absence and presence of ultrasound. Batch process was employed for sorption kinetic and equilibrium studies. Sorption experiments indicated that the sorption capacity was dependent of operating variables. Both the rate and the amount of malachite green sorption are markedly increased in the presence of the ultrasonic field. The dye removal with the assistance of ultrasound was enhanced with the increase of sorbate initial concentration and temperature, and with the decrease of sorbent dosage and ionic strength. The combination of stirring and ultrasound leads to an improvement of the removal of dye. The sorption kinetics was controlled by the intraparticle diffusion. The intraparticle diffusion coefficient increased 1.7 times in the presence of ultrasound and up to 3.6 times in the combined process. The sorption capacity, estimated according to the Freundlich model, indicates that ultrasound enhanced the sorption properties of the sorbent. The effect of ultrasound on the improvement of dye sorption is due to a variety of physical and mechanical effects as well as to thermal properties. The combination of ultrasound and stirring for the sorption process was shown to be of interest for the treatment of wastewaters contaminated with malachite green.

Ultrasonics Sonochemistry, 2010

The aim of this work was to study the emulsification assisted by ultrasonic probe (22.5 kHz) and ... more The aim of this work was to study the emulsification assisted by ultrasonic probe (22.5 kHz) and investigate the removal of copper(II) ions from aqueous solution using water-in-oil-in-water (W/O/W) emulsion liquid membrane process (ELM). The membrane was prepared by dissolving the extractant bis(2-ethylhexyl)phosphoric acid (D2EHPA) and the hydrophobic surfactant sorbitan monooleate (Span 80) in hexane (diluent). The internal phase consisted of an aqueous solution of sulfuric acid. Effects of operating parameters such as emulsification time, ultrasonic power, probe position, stirring speed, carrier (D2EHPA) and surfactant (Span 80) concentrations volume ratios of organic phase to internal striping phase and of external aqueous phase to membrane (W/O) phase, internal phase concentration and choice of diluent on the membrane stability were studied. With ultrasound, the W/O emulsion lifetime were much higher than those reported previously by mechanical agitation. The effect of carrier and Cu(II) initial concentration on the extraction kinetics was also investigated. Nearly all of the Cu(II) ions present in the continuous phase was extracted within a few minutes. Additionally, the influence of H 2 SO 4 concentration on the stripping efficiency was examined.

Ultrasonics, 2014

In this work, energy analysis of an oscillating isolated spherical bubble in water irradiated by ... more In this work, energy analysis of an oscillating isolated spherical bubble in water irradiated by an ultrasonic wave has been theoretically studied for various conditions of acoustic amplitude, ultrasound frequency, static pressure and liquid temperature in order to explain the effects of these key parameters on both sonochemistry and sonoluminescence. The Keller-Miksis equation for the temporal variation of the bubble radius in compressible and viscous medium has been employed as a dynamics model. The numerical calculations showed that the rate of energy accumulation, dE/dt, increased linearly with increasing acoustic amplitude in the range of 1.5-3.0 atm and decreased sharply with increasing frequency in the range 200-1000 kHz. There exists an optimal static pressure at which the power w is highest. This optimum shifts toward a higher value as the acoustic amplitude increases. The energy of the bubble slightly increases with the increase in liquid temperature from 10 to 60°C. The results of this study should be a helpful means to explain a variety of experimental observations conducted in the field of sonochemistry and sonoluminescence concerning the effects of operational parameters.

The Journal of Physical Chemistry A, 2007

In the present study, the sorption of cadmium from aqueous phase by wheat bran was investigated w... more In the present study, the sorption of cadmium from aqueous phase by wheat bran was investigated with and without the assistance of ultrasound. Kinetic data and sorption equilibrium isotherms were carried out in batch conditions. The influence of different operating parameters such as ultrasonic power, cadmium initial concentration, sorbent mass, temperature, and the combination of ultrasound and mechanical stirring on the kinetics of cadmium removal was studied. The obtained results show that the ultrasonic irradiation significantly enhances and improves the efficiency of the removal of cadmium, especially in the combined method. The sorption kinetic data were found to be well-represented by the pseudo-second-order rate equation, both in the absence and presence of ultrasound as well as in the combined process (stirring and ultrasonication). Ultrasonic power played a key role in the removal of cadmium. Equilibrium isotherm results could be well described by the Langmuir model both with and without the assistance of ultrasound. The effect of temperature on the sorption isotherms of cadmium in the absence and presence of ultrasound has been also studied and the thermodynamic parameters ∆G°, ∆H°, and ∆S°were determined. The monolayer sorption capacities were 51.81, 35.09, and 22.78 mg g -1 for experiments conducted by the combined process, in the presence of ultrasound, and in passive conditions, respectively. The combination ultrasound-stirring for the sorption process was shown to be of interest for the treatment of wastewaters contaminated with cadmium.