Nickel Biosorption by Fungal Chitosan from Mucor Indicus

Chitosan was extracted and purified from the cell wall of the fungus Mucor indicus. Nickel biosorption capacity of the fungal chitosan was compared with that of shrimp chitosan. Maximum adsorption capacities (mg/g) were 2.8 for fungal chitosan and 1.3 for shrimp chitosan, indicating the higher performance of fungal chitosan for nickel adsorption. Moreover, the adsorption kinetics on fungal chitosan as well as its equilibrium behavior was investigated. Besides, the effect of initial pH on nickel removal by fungal chitosan was studied. The adsorption capacity was increased by increasing the pH from 3 to 5 (from 8.5 to 10.4 mg/g, respectively). The highest adsorption capacity was obtained at pH 5. Among Langmuir, Freundlich, Temkin, and Scatchard models, Langmuir and Freundlich models described the isotherm data very well. These two models are respectively related to adsorbent with homogeneous surface (no interaction by adsorbed molecules) and adsorbent with smooth but heterogeneous surface. The kinetic data was fitted well to pseudo-second order model rather than pseudo-first order and intra-particle diffusion models. This indicated that the adsorption reaction controls the adsorption process.