Fungal biomass composite with bentonite efficiency for nickel and zinc adsorption: A mechanistic study

Fungal dead biomass composite with bentonite (FBC) efficiency was evaluated for the absorption of Ni(II) and Zn(II) from aqueous media. The process variables were optimized and maximum adsorption was achieved at pH 6 (Ni) and 5 (Zn), adsorbent dose 0.05 g, contact time 30 min, initial metal ions concentration 200 mg/L and temperature 51 degrees C. At optimum conditions, 161 mg/g of Ni(II) and 78.5 mg/g of Zn(II) was removed using FBC. Langmuir, Freundlich and Harkins-Jura isotherms and pseudo-first-order, pseudo-second-order and intraparticle diffusion models were applied to understand the adsorption mechanism. The pseudo-second-order kinetic model and Langmuir isotherm fitted well to the adsorption experimental data. The surfactants and salts (CaCl2, KCl, NaCl, CuSO4 and FeCl3) FBC pre-treatment did not affect the Ni(II) and Zn(II) adsorption. The Delta G degrees, Delta H degrees and Delta S degrees values suggest that the adsorption process of Ni(II) and Zn(II) onto FBC was spontaneous and endothermic in nature. NaOH efficiently desorbed Ni(II) and Zn(II) from FBC without compromising the adsorption capacity of composite. Results showed that FBC is efficient for the adsorption of Ni(II) and Zn(II) and is a potential candidate for the adsorption of metal ions from wastewater. (C) 2016 Elsevier B.V. All rights reserved.