Abstract :
The biosorption studies for effective removal of cadmium (II) ions from aqueous solutions using orange rind (Citrus sinensis L. Osbeck), cost effective biosorbent, was carried out in batch system. FTIR analysis of biosorbent confirmed that carboxyl, hydroxyl, carbonyl group which was responsible for
biosorption of cadmium (II) ions. The SEM represents porous structure with surface area. The effects of operational factors including solution pH, biosorbent dose, initial cadmium (II) ions concentration, contact time and temperature were studied. The optimum solution pH for cadmium (II) ions biosorption by biosorbent was 7.0 with the optimal removal 80.30 %. The biosorbent dose 5 mg/ml was enough for optimal removal of 65.15 %. The biosorption process was relatively fast and equilibrium was achieved after 90
minutes of contact. The experimental equilibrium biosorption data were analysed by four widely used twoparameters Langmuir, Freundlich, Dubinin-Kaganer-Redushkevich (DKR) and Temkin isotherm models. Langmuir isotherm model provided a better fit with the experimental data than Freundlich, Temkin and Dubinin-Kaganer-Redushkevich (DKR) isotherm models by high correlation coefficient value (R2 = 0.911). The maximum adsorption capacity determined from Langmuir isotherm was found to be 83.33 mg/g of biosorbent. Simple kinetic models such as pseudo-first-order, pseudo-second-order, Elovich equation and Weber and Morris intra-particle diffusion rate equation were employed to determine the adsorption mechanism. Results clearly indicates that the pseudo-second-order kinetic model (R2 = 0.998) was found to
be correlate the experimental data strongest than other three kinetic models and this suggests that chemical adsorption process was more dominant. Thermodynamic study revealed that the biosorption process was spontaneous, endothermic and increasing randomness of the solid solution interfaces. Orange rind (Citrus sinensis L. Osbeck) was successfully used for the biosorption studies of cadmium (II) ions from aqueous solutions and can be applied in waste water technology for remediation of heavy metal contamination.
Keyword :
Adsorption isotherms; Adsorption kinetics; FTIR; SEM; Thermodynamic study.