Removal efficiency of some biosorbents in removing of cadmium from aqueous solution
Document Type : Research Paper
Authors
1 Associate Prof. of Soil Science, Faculty of Agriculture, Uremia University, Urmia, Iran
2 MSc. Student of Soil Science, Faculty of Agriculture, Uremia University, Urmia, Iran
Abstract
The application of organic sorbents for removing heavy metal from water, replacing expensive sorbents, is particularly appropriate for developing countries. To investigate the efficiency of some organic sorbents in removing of Cd2+ from aqueous solution, an experiment was conducted with three organic sorbents (sunflower stalks, apple and grapevine pruning residues) and 11 initial concentration of Cd2+ (0- 200 mg L-1) at three pH (4, 6, 8). The results showed that three organic sorbents have relatively high removal efficiency (RE) for cadmium from aqueous solution, and RE increased with increasing of pH but initial concentration of cadmium showed invers effect. The highest RE was obtained at pH 8 and low initial concentration of Cd (≤10 mg L-1) for all three organic sorbents. Among sorption models (Langmuir, Temkin and Freundlich), Langmuir model was better fitted for experimental data (R2= 0.99). At pH8, maximum mono layer adsorption (qmax) of sunflower stalks, apple and grape pruning residues were obtained 8905, 8155 and 7895 mg kg-1, respectively. All sorption parameters (qmax, A, KF, KT, KL, n) of sunflower stalks was more than those of apple and grape pruning residues. Therefore, sunflower stalks in comparison to apple and grape pruning residues, have a high efficiency in removing of cadmium from aqueous solution. The Gibbs free energy of reaction (ΔGr) and separation factor of Langmuir (RL) indicated that the sorption reaction of Cd2+ by all three biosorbents are spontaneous and favorable.
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