Removal of direct red 81 from aqueous solution by adsorption onto magnesium oxide-coated kaolinite: Isotherm, dynamics and thermodynamic studies (original) (raw)
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DESALINATION AND WATER TREATMENT, 2018
In the present work, two Algerian clay samples, Djebel Debagh (DD3) and Tamazert (KT2), were used as adsorbents for the removal from the water of Derma Blue R67, which is an acid dye commonly used in the tanning industry. The two clay samples used were first treated by acid in order to enhance their retention capacities, and then characterized using X-ray diffraction, scanning electron microscopy, surface area measurements (Brunauer, Emmett et Teller method (BET)), surface charge (points of zero net proton charge), and electrophoretic mobility (Zetaphoremeter). Further, the adsorption experiments of the acid dye from water onto the clay surface were carried out by investigating various parameters such as, the contact time, the initial dye concentration, the aqueous phase pH, the clay amount and the temperature. The results indicate that the two adsorbents are efficient and that the anionic dye removal from water is mainly feasible at ambient temperature. Further, the comparison of the experimental adsorption data to the prediction models has shown that the Langmuir model gives the best fit, indicating the formation of a monolayer by the acid dye molecules on the clay surface. Finally, the adsorption kinetics follows a two-type process onto KT2 kaolinite, whereas onto DD3, it only follows the pseudo-second order model. From the overall data, it is concluded that the Algerian local kaolin clays are good adsorbent candidates for wastewater treatments.
SN Applied Sciences
Presence of dye molecules in water causes various harmful effects for both human and aquatic species. Herein, we tried to remove two cationic dyes, namely Crystal violet and Brilliant green, from water by kaolinite clay mineral. The kaolinite clay mineral is further treated with 0.25 M and 0.05 M H 2 SO 4 to increase its adsorption capacity. The structural changes due to acid treatment were analyzed by XRD, zeta potential, FTIR, SEM, cation exchange capacity, BET surface area, and pore volume measurements. Kinetic data were analyzed by using five different kinetic models and the data fitted best to pseudo-second-order model. Langmuir isotherm showed best fit to the adsorption of both Crystal violet and Brilliant green. Acid-treatment has slightly increased the adsorption capacities for both the dyes. The Langmuir monolayer adsorption capacity of raw kaolinite was found to be 47.17 and 25.70 mg g −1 for Crystal violet and Brilliant green, respectively, which increased to 49.50 and 50.51 mg g −1 for 0.25 M and 0.50 M acid-treated kaolinite in case of Crystal violet and to 26.45 and 26.88 mg g −1 in case of Brilliant green at 303 K. Crystal violet adsorption was exothermic with increase in ∆G values, whereas Brilliant green adsorption was endothermic in nature with decrease in ∆G in the temperature range 293-323 K. Reusability study showed the adsorbents could be successfully used up to 3rd cycle without much loss of adsorption capacity.
2017
The tanning industry, particularly the discharges from the dyeing process, induces environment pollution, causing hence human health problems. The treatment of the effluents by using low cost clays would have an important economic and environmental interest, as it would promote the local clays from the Algerian East. In the present work, we tested two Algerian kaolin clays, DjebelDebagh "DD3" and Tamazert “KT2”. These two clayswere firsttreated by acid in orderto enhance their retention capacities,and then characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), surface area measurements (BET method), surface charge (PZNPC), and electrophoretic mobility (Zetaphoremeter). The adsorption experiments were done using the Derma Blue R67 acid dye, commonly used in the tanning industry. The results showthat the adsorption is efficient and feasible at ambient temperature, and well described by the Langmuir model indicating a monolayer covering of the clay b...
Water, Air, & Soil Pollution, 2018
Waste water from textile and other industries containing dyes, especially azo dyes, are a serious health hazard. This study deals with removal of two leaststudied anionic azo dyes, namely, Crocein orange G (COG) and Procion red MX5B (MX5B) from water with the help of montmorillonite and acid-treated montmorillonite. Structural changes of montmorillonite clay mineral after acid treatment were thoroughly investigated with the help of XRD, FTIR, SEM, BET surface area, and porosity measurements and zeta potential measurements. Influences of pH, interaction time, adsorbent amount, and temperature on adsorption were monitored, and the dye-clay mineral interactions were explained on the basis of physico-chemical characteristics of the materials. Acidic pH favored the adsorption of both dyes, and maximum adsorption was observed at pH 2.0 for both the dye. The dye-clay interaction reached equilibrium at 180 min for COG and at 240 min for MX5B, respectively. Adsorption kinetics and isotherm were studied in details, and it was observed that the adsorption process followed pseudo-second-order kinetics and Freundlich isotherm at 303 K. Langmuir monolayer adsorption capacity for MX5B and COG were found to be 11.04 and 9.51 mg g −1 , respectively, at 303 K. Acid treatment of montmorillonite clay mineral showed 23.45 and 15.67% increase in adsorption capacity for MX5B and COG, respectively. The adsorption process is highly dependent on temperature and is endothermic in nature. This endothermic interaction is mainly driven by increase in entropy and decrease in Gibbs energy at higher temperature. This study successfully showed that montmorillonite and acid-treated forms can be effectively used to remove both COG and MX5B dyes from water.
Raw kaolinite was used as a precursor for several types of modified kaolinite. The modification processes included modification by sodium hydroxide, sodium phosphate, sodium sulfate, CTAB, and sodium acetate. The structural, morphological, and chemical properties of raw kaolinite and the modified products were evaluated using XRD, SEM, TEM, and FT-IR analyses. The modified products were used as adsorbent materials for acidic Congo red dye from aqueous solutions. The adsorption processes were evaluated as a function of reaction time, initial dye concentration, and adsorbent masses. Phosphate-modified kaolinite achieved the best removal results followed by sulfate-modified kaolinite and kaolinite sample modified by CTAB. Kinetic studies indicated that the adsorption equilibrium was obtained after 360 min for the samples, which were modified by NaOH and CTAB, whereas the modified samples that were treated by phosphate, sulfate and, acetate achieve the equilibrium after 240 min. The adsorption by all the products is of chemical nature occurs through energetically heterogeneous surfaces and fitted well with pseudo-second order kinetic model. The equilibrium studies revealed that the adsorption using kaolinite modified by sodium hydroxide, sodium phosphate, and sodium sulfate occurs in monolayer form and represented well by Langmuir model. The estimated q max values are 136.98, 149.25, and 135.13 mg/g for the three products in order. The uptake using modified kaolinite by CTAB and sodium acetate shows more fitting with Tamkin and Freundlich isotherm models rather than with Langmuir model. Graphical Abstract Kaolinite sample was modified by organic and inorganic salts to enhance its adsorption properties. Modified kaolinite samples exhibit changes in the structural and morphological features. The modified samples showed high adsorption capacity than raw kaolinite. Highlights ● Kaolinite was modified by several inorganic and organic salts. ● Effect of modification and the structural and morphological features was investigated. ● The adsorption behavior of the modified products for Congo red dye was addressed. ● The change in the adsorption behavior was studied through kinetic and isotherm studies.
DESALINATION AND WATER TREATMENT
The removal of Congo red dye from aqueous solutions by adsorption reaction onto three distinct adsorbents: graphene oxide (GO), graphene oxide-grafted-3,3'-diaminobenzidine (GO/ DAB), and GO/DAB-grafted-ethylenediaminetetraacetic acid (GO/DAB/EDTA) was investigated in batch experiments. The study of the effects of pH and contacting time on adsorption systems is the first step in optimizing them. The results revealed that depending on the type of adsorbent, the optimum pH values and periods differed. The Congo red (CR) dye adsorptions onto the investigated adsorbents GO, GO/DAB, and GO/DAB/EDTA required pH (3.0, 7.0, and 5.0, respectively) and time (60, 30, and 45 min). The fundamental adsorption properties of the dye were evaluated using adsorption equilibrium isotherms, namely the Langmuir, Freundlich, and Dubinin-Radushkevich models. The maximum adsorption values (q max) were calculated using the Langmuir isotherm results, and they were 1,250; 1,428.5 and 1,438.1 mg/g for the adsorption of CR dye onto adsorbents GO, GO/DAB, and GO/DAB/EDTA, respectively, and these results proved the preference for prepared GO-derivatives over GO. The kinetic models, namely pseudo-first-order and pseudo-second-order, were employed to understand the mechanism of the adsorption process, and they fitted very well with the pseudo-second-order kinetic model, which relies on the assumption that chemisorption may be the rate-limiting step. This study reveals that the presence of functional groups and active sites on the studied adsorbent contributed to its high affinity for CR dye adsorption. As a result, they can be used as efficient and cost-effective dye adsorbents in industrial effluent. Thermodynamic parameters including enthalpy ΔH°, entropy ΔS°, free energy ΔG°, and activation energy E a of the adsorption process were calculated and used to interpret the results, which revealed that the adsorption systems were a spontaneous and endothermic process for GO and its composites. Also, low activation energy values (E a < 40 kJ/mol) were characteristics of the physisorption mechanism and diffusion-controlled process.
Adsorption Science & Technology, 2012
The < 25 µm fraction of natural clay containing kaolinite, chlorite, illite and illite/smectite mixed layered clay minerals was characterized and used as a potential adsorbent for the removal of Rhodamine B (RB) dye from aqueous solution. Adsorption experiments were carried out in batch mode by varying the following parameters: pH, temperature, initial dye concentration, adsorbent dosage and time of contact. The equilibrium data were well fitted by both the Langmuir and Freundlich adsorption isotherms. The Langmuir monolayer adsorption capacity was found to be 4.77 mg/g, which was better than the value reported for kaolinite (1.95 mg/g). The adsorption process followed pseudo-second-order kinetics. Negative ∆G 0 values indicated that adsorption onto this clay was a spontaneous process. A maximum dye uptake of > 90% was achieved at 313 K employing an initial dye concentration of 4.8 × 10-6 M, a pH value of 2 and an adsorbent dosage of 1 g/ .
Heliyon, 2020
In the present research, the kaolin adsorbents (beneficiated, raw powder, and calcined) were prepared from Ethiopian natural kaolin through mechanical, wet, and thermal processes. The geochemical and surface properties of kaolin adsorbent were characterized using FTIR, SEM/EDS, XRD, and XRF. In the batch experiment, basic operation parameters (initial dye concentrations, pH, temperature, contact time, and adsorbent dosage) were examined. Percentage removal efficiency basic yellow 28 (BY28) dye were recorded as 94.79%, 92.08%, and 87.08% onto beneficiated, raw, and calcined kaolin absorbents, respectively at an initial dye concentration of 20 mg/L, solution pH of 9, the temperature of 30 C C, and contact time of 60 min and adsorbent dosage of 1g/ 100L. The molar ratio of SiO 2 /Al 2 O 3 was recorded as 2.911 Percent mass composition of Ethiopian kaolin which is higher than the expected pure kaolinite standard which allows us to classify the kaolin clay as a siliceous one. The calculated values of ΔG 0 for beneficiated adsorbent are-1.243, 1.576, and 4.396 kJ/mol at 303.15, 323.15, and 343.15 K, respectively for 20 mg/L of dye concentration and solution pH of 9, suggests that the thermody-namic behavior at lowest temperature is more feasible and spontaneous as compared with the higher temperature one. A similar fashion was calculated for raw and calcined adsorbents. The negative values of ΔH o and ΔS suggest that the adsorption phenomenon is exothermic and the adsorbate molecules are organized on the solid phase in a more disordered fashion than the liquid phase. The pseudo-first-order and pseudo-second-order models have been used to describe the kinetics in the adsorption processes. The Pseudo-second-order model has been fitted for the BY 28 dye adsorption in the studied concentration range. The adsorption of BY 28 dye for raw and calcined adsorbents follows the Langmuir isotherm and the Freundlich isotherm fitted for the beneficiated adsorbent. The amount of BY28 dye taken up by beneficiated, raw, and calcined kaolin adsorbents was found as 1.896, 1.842, and 1.742 mg/g, respectively at a contact time of 1.0 h, the adsorbent dosage of 1.0 g, initial dye concentration ¼ 20 mg/L and solution pH ¼ 9 at 30 C. The results found that these raw and prepared local kaolin adsorbents have a capacity as low-cost alternatives for the removal of dyes in industrial wastewater.
Saudi Journal of Engineering and Technology
Decolourisation of wastewater, particularly from textile industries is one of the major environmental concerns these days. The limitations of most of these treatment methods are their high operational and maintenance costs cannot effectively be used to treat wide range of such wastewater. This work describes the use of kaolinite clay as an efficient adsorbent material for anionic azo dye methyl orange removal from synthesized wastewater. Batch adsorption experiment of 200 mgL-1 azo dye methyl orange contaminant removal using kaolinite clay at different stirring speed: 100, 200, 300, 400 and 500 rpm at constant pH4 and contact time of (0-180) minutes were investigated, thus, adsorption increases with increase in stirring speed with maximum removal of 69.90% and maximum adsorptive capacity of 3.476 mg/g at 500 rpm. The adsorption equilibrium data were well described by Langmuir>Freundlich>Koble-Corrigan whilst adsorption kinetic data by pseudo second-order>pseudo first-order>intraparticle diffusion>Reichenberg equation in the stated order based on high correlation coefficients and relatively small values of error function analyses (χ 2 , RMSE, NSD and ARE). The adsorption processes were controlled by chemisorption. The potential applicability of Alkaleri kaolinite clay from Northeast-Nigeria could be employed as a low-cost adsorbent alternative to commercial/activated carbon in the removal of azo dye methyl orange from wastewater.
A zeolitic-tuff (NRZ)was characterized using X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) as well as surface properties. The ability of the NRZ to removal of malachite green (MG) dye has been evaluated. Effect of initial dye concentrations, amount of adsorbent, contact time, temperature, pH and stirring time on the removal of MG were estimated in batch adsorption experiments. Isotherm data were analyzed by Langmuir, Freundlich and Temkin isotherms. Results of XRD showed that the NRZ composed mainly of clinoptilolite (45 wt %), cowlesite (41 wt %) and cristobalite (14 wt %). N2-adsorption analysis revealed to surface area, pore radius and pore volume are 38.292 m 2 /g, 17.39 Å, 0.085 cc/g, respectively. The adsorption isotherm was matched with type II and hysteresis of H3 type. The cation exchange capacity of NZ was 2.8 meq/100g and pH about 7, which showed high fit with the Langmuir isotherm. The maximum capacity was found to be 129.65 mg/g at 298 K. Kinetics of adsorption process was evaluated by pseudo-first order, pseudo-second order, and intraparticle diffusion mechanism. Pseudo-second order kinetic model was provided a better fit with the data. The mechanism of the adsorption process was not controlled only by intra-particle diffusion but involved complex mechanism. The Elovich model and the thermodynamic parameters suggested that the adsorption was a chemisorption spontaneous process and exothermic in nature. The values of activation energy confirmed the exothermic nature of the process. The results of multi-stages continue process(CSTR) was indicated that the MG could be removed from aqueous solution with 10 min with high removal %.