An economically viable method for the removal of selected divalent metal ions from aqueous solutions using activated rice husk (original) (raw)
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Chemical Engineering Communications, 2013
Four carbon=silica-containing materials obtained by pyrolysis of rice husks were characterized and their adsorption properties towards some metal ions were evaluated. GC=MS analysis and FT-IR spectroscopy were applied for identification of functional groups finely dispersed on the surface. Their amounts were gravimetrically determined after extraction with acetone. The specific surface area and porosity of the materials were characterized by the Brunauer-Emmett-Teller (BET) method and by mercury porosimetry, respectively. The adsorption properties of the carbonized rice husks towards Fe(III), Pb(II), Cr(III), and Cu(II) ions in single-and multicomponent aqueous solutions also containing Ni(II), Co(II), Mn(II), and Cd(II) were studied in a batch system. The effects of contact time, acidity of initial solutions, and metal ion concentrations were followed. Pseudo-first-order, pseudosecond-order, and intraparticle diffusion models were used to analyze kinetic data. Equilibrium experimental data were fitted to linear Langmuir and Freundlich models. The maximum adsorption capacities for single-and multicomponent adsorption were calculated and compared with literature data. A correlation between the adsorption properties of pyrolyzed rice husks and their textural and surface parameters was established. Possibilities for desorption of the investigated ions were estimated.
Journal of Hazardous Materials, 2006
The present study deals with the characterization of low-cost rice husk ash (RHA) for its various physico-chemical properties and adsorption characteristics of metal ions. The average particle size of RHA was 150.47 m. Proximate analysis showed the presence of high amount of ash in RHA. Bulk density and the heating value of RHA were 104.9 kg/m 3 and 9.68 MJ/kg, respectively. The pore size distribution results showed that the RHA was predominantly mesoporous. The BET surface area was 36.44 m 2 /g. The average pore diameter by BET was 42.603Å. The BJH pore area showed 80% of the pore area due to the mesopores. The polar groups present on the RHA surface imparted considerable cation exchange capacity to it. RHA was found to be an effective adsorbent for the removal of cadmium (Cd(II)), nickel (Ni(II)) and zinc (Zn(II)) metal ions from aqueous solutions. The pH 0 ≈6.0 is found to be the optimum for the removal of individual cations from the aqueous solutions by RHA at an optimum dose of 10 kg/m 3 . The kinetics of adsorption showed that the metal ions adsorption on RHA is a gradual process with quasi-equilibrium being attained in 5 h. The pseudo-second-order kinetics represents the equilibrium data well. The effective diffusion coefficient of the cations onto the RHA is of the order of 10 −13 m 2 /s.
Journal of environment and earth science, 2017
In the present study the adsorption of Cu (II) and Zn (II) ions on rice husk from artificially prepared aqueous solutions of these metal ions was investigated following the batch mode adsorption procedure. Accordingly, the effects of operating parameters such as pH, contact time, and initial concentration of metal ion solution were evaluated. The results so obtained in this study indicated that the optimum conditions for the Cu(II) and Zn(II) ions adsorption were found to be as follows: pH of 6 and 7; contact times of 100 and 125 minutes; and these values were actually determined by setting the initial concentration of 50 mg/L for each metal ion solution. Upon measurements of the residual metal ion concentration using FAAS method, the percent adsorption of both Cu (II) and Zn (II) ions showed significant increase with an increase in each case of the contact time. Furthermore, it was evidently implicated that the binding process of the metal ions on the adsorbent (rice husk) could be affected by change in the pH of both metal ion solutions. In addition the experimental data were analyzed against both Langmuir and Freundlich isotherm for determining the maximum adsorption capacity of the title bioserbent with respect to each of the tested metal ions. The adsorption maxima were calculated on the basis the Langmuir isotherm and found to be 1.93 and 12.98 mg/g for Cu (II) and Zn (II) metal ions respectively. These values are suggested that the rice husk investigated in this study can have a good application potential for the removal of both metal ions (Cu (II) and Zn (II)) from aqueous solutions. In fact, the goal of this work was to develop an inexpensive, highly available, effective metal ion adsorbent from natural waste as alternative to existing commercial adsorbents.
American Journal of Chemical Engineering, 2020
This study was carried out to evaluate the efficiency of metal ions removal from aqueous solution using silica adsorbent. Silica was extracted from rice husk using sol-gel method. The silica was modified with 1.0 M of nitric acid. Using batch adsorption technique, the effects of temperature, pH, contact time and adsorbent dosage on adsorption process of Cu (II), Zn (II), Mn (II) and Pb (II) ions were studied using standard solutions of their salts. Percentage removal of the metals ions studied decreased as the temperature was varied between 28°C and 43°C. Percentage removal of metal ions studied showed an increase at different pH varying from 4 to 8 and decreased after the pH 8. The variation of contact time between 2 and 8 hours showed a sharp increase in metals removal from 2 to 6 hours but a slow increase after 6 hours. The percentage removal of metal ions increase as the adsorbent dosage increased between 0.5 g and 2.0 g. The maximum percentage removal of metal ions was found to be 99.48%. The general observed trend of efficiency being Cu>Pb>Zn>Mn. The experimental data was also tested using adsorption isotherm models of Langmuir and Freundlich and Langmuir model was found to be the best fit for the data.
Efficiency of Rice Husk for Removal of Cu(II) and Zn(II) Ions from Aqueous Solution
2017
In the present study the adsorption of Cu(II) and Zn(II) ions on rice husk from artificially prepared aqueous solutions of these metal ions was investigated following the batch mode adsorption procedure. Accordingly, the effects of operating parameters such as pH, contact time, and initial concentration of metal ion solution were evaluated. The results so obtained in this study indicated that the optimum conditions for the Cu(II) and Zn(II) ions adsorption were found to be as follows: pH of 6 and 7; contact times of 100 and 125 minutes; and these values were actually determined by setting the initial concentration of 50mg/L for each metal ion solution. Upon measurements of the residual metal ion concentration using FAAS method, the percent adsorption of both Cu(II) and Zn(II) ions showed significant increase with an increase in each case of the contact time. Furthermore, it was evidently implicated that the binding process of the metal ions on the adsorbent (rice husk) could be affe...
Chemical Engineering and Processing, 2009
The present study deals with the competitive adsorption of cadmium (Cd(II)) and nickel (Ni(II)) ions from aqueous solution onto rice husk ash (RHA). Non-competitive Redlich-Peterson (R-P) and Freundlich models represent the single metal ion equilibrium sorption data. The adsorption capacities for the binary mixtures-RHA system are in the order Ni(II) > Cd(II). The combined equilibrium sorption of Cd(II) and Ni(II) ions onto RHA is found to be antagonistic in nature and the extended Freundlich model was found to best represent the binary equilibrium isotherm data. .in (V.C. Srivastava).
The sorption of cadmium(II) ions on mercerized rice husk and activated carbon
Turkish Journal of Chemistry
This work describes the removal of Cd(II) ions in aqueous solution by unmodified and base-modified rice husk (RH) as compared to that by activated carbon (AC). Mercerization of RH was carried out by using dilute solutions (0.013 M) of NaOH, KOH, and Ca(OH) 2. The experiments were conducted in duplicate under 1-batch and 2-batch treatments. In the 1-batch treatment, a fresh 200 mg of each adsorbent was used to study the sorption of the Cd(II) ions from 100-mL solutions at an initial concentration of 5 mg L −1. The adsorption percentage increased in the order of unmodified RH (80.13 ± 0.46%) < Ca(OH) 2-modified RH (90.74 ± 0.18%) < NaOH-modified RH (93.36 ± 0.23%) ≤ KOH-modified RH (93.78 ± 0.27%) < AC (98.4 ± 0.18%). In the 2-batch treatment, a fresh 100 mg of each adsorbent was placed in 100-mL solutions at an initial concentration of 5 mg L −1 of Cd(II) ions for 30 min, and the resulting solutions were filtered. The filtrates were subjected to another fresh 100 mg of each adsorbent for an additional 30 min. The percentage removal of the metal ion using the 2-batch treatment for unmodified RH, base-modified RH, and AC was 97.71%, 98.00 ± 1.00%, and nearly 100%, respectively.
Thermodynamic Characterization of Sorption of Copper(II) ions on Rice Husk
INTERNATIONAL JOURNAL OF ENGINEERING SCIENCES & RESEARCH TECHNOLOGY, 2014
This paper attempts to develop simple and easily understandable thermodynamic parameters related sorption process at the equilibrium. Batch kinetic studies were conducted for the adsorption of Cu(II) on SCRH (sodium carbonate treated rice husk). The removal were observed to increases from 92.9 to 96 % with the increase in temperature from 15° to 50° C. Equilibrium time was found to be 60 min. The overall scenario represented by thermodynamic parameters was found to be a better indicator of understanding the process mechanism. Sorption of Cu(II) on SCRH followed pseudo second-order kinetic equation. The Gibbs free energy ΔG° values for the adsorption processes of Cu(II) at 15° , 30° , 40° and 50 °C was obtained as – 6.16, – 6.84, – 8.01 and – 8.53 kJ/mol respectively. The negative value, ΔG° confirms the feasibility of the adsorption process and spontaneous nature of adsorption. The values of ΔH° and ΔS ° for Cu(II) were obtained as 14.37 kJ/mol and 70.92 J/mol respectively. The positive value of ΔH° indicates endothermic nature of adsorption, while positive ΔS ° value confirms the increased randomness at the solid-liquid interface during adsorption. The activation energy for the sorption of Cu(II) was found as 9.00 kJ/mol indicating chemisorptions.
Chemical Engineering Journal, 2008
We prepared activated carbon by pyrolyzing an agro-waste, rice husk, in the presence of ZnCl 2 . The activated carbon displayed both microporous and mesoporous nature with a significant surface area of 180.50 m 2 · g -1 . Fourier transform infrared (FTIR) spectrograms of the activated carbon were recorded to determine the number and positions of the functional groups available on its surface. The adsorption of methylene blue (MB) from its aqueous solutions by rice husk activated carbon (RHAC) was studied. The removal of dye increased from (82.75 to 93.20) % with decreasing initial concentration of MB from (100 to 60) mg · L -1 . The time of equilibrium was found to be 100 min. Higher removal was obtained at higher dose of adsorbent, and the removal increased from (86.75 to 99.83) % with increasing adsorbent dose from (0.40 to 0.60) g. The removal of methylene blue increased from (93.20 to 99.16) % with increasing temperature from (30 to 50)°C at 60 mg · L -1 MB concentration, 150 rpm, and 100 µm particle size. Isotherm studies were conducted to know the capacity of the activated carbon. Langmuir and Freundlich isotherm equations were applied for the equilibrium data.
Thermodynamic and kinetic studies of cadmium adsorption from aqueous solution onto rice husk
Brazilian Journal of Chemical Engineering, 2010
The adsorption behavior of rice husk for cadmium ions from aqueous solutions has been investigated as a function of appropriate equilibrium time, adsorbent dose, temperature, adsorbate concentrations and pH in a batch system. Studies showed that the pH of aqueous solutions affected cadmium removal with the result that removal efficiency increased with increasing solution pH. The maximum adsorption was 98.65% at solution pH 6, contact time 60 min and initial concentration of 25 mg/L. The experimental data were analysed by the Langmuir, Freundlich and Temkin models of adsorption. The characteristic parameters for each isotherm and related correlation coefficients have been determined. Thermodynamic parameters such as o G Δ , o H Δ and o S Δ have also been evaluated and it has been found that the sorption process was feasible, spontaneous and exothermic in nature. The kinetics of the sorption were analysed using the pseudo-first order and pseudo-second order kinetic models. Kinetic parameters, rate constants, equilibrium sorption capacities and related correlation coefficients for each kinetic model were calculated and discussed. It was shown that the adsorption of cadmium could be described by the pseudosecond order equation, suggesting that the adsorption process is presumably a chemisorption. The rice husk investigated in this study showed good potential for the removal of cadmium from aqueous solutions. The goal for this work is to develop inexpensive, highly available, effective metal ion adsorbents from natural waste as alternative to existing commercial adsorbents.