Adsorption of zinc (II) onto MnO2/CS composite: equilibrium and kinetic studies

In this work, manganese dioxide/ chitosan (MnO2/CS) was used to remove Zn(II) from an aqueous sample over a concentration range of 30-100 mg/L, adsorption time of 15-180 min, and pH of 2-5. The maximum sorption (>80%) was achieved at pH 4 after 80 min with an initial concentration of 50 mg/l and 0.1 g of MnO2/CS. The experiment data were analyzed using the non-linear Freundlich, Langmuir, Redlich-Peterson, Sips, Temkin and Dubinin-Radushkevich (D-R) isotherm models. Langmuir isotherm offers maximum sorption capacity (q(m)) of 24.21 mg/ g (RMSE = 1.575 and chi = 0.8034), while the Temkin and Dubinin-Radushkevich (D-R) isotherm models indicated that adsorption followed a physical process. Furthermore, kinetic studies showed that the adsorption processes partially followed the pseudo-second-order equation. In addition, intra-particle diffusion model was used to ascertain the sorption process mechanism. MnO2/CS has also been used to remove Zn(II) from the wastewater produced by the galvanized iron manufacturing industry.