Adsorption of Ni2+ in aqueous solution by KMnO4 modified biomass: investigation on adsorption kinetics and modification mechanism

In this study, KMnO₄ modification was proved to effectively increase the Ni²⁺ adsorption capacity of biomass. In order to clarify the KMnO₄ modification mechanism, the Ni²⁺ adsorption characteristics of KMnO₄ modified corncob (PPCB) under adsorption time, pH and Ni²⁺ concentration were studied. The results showed that the adsorption was the pseudo second-order kinetic process, indicating that chemisorption was the dominated process, which followed the Langmuir isotherm model and the highest Ni²⁺ adsorption capacity of PPCB reached 35.6 mg/g. By KMnO₄ modification, the corncob was oxidized to generate carboxylates, and the MnO₂ (reduction product) was loaded on the modified corncob, both carboxylates and MnO₂ increased the Ni²⁺ adsorption capacity of PPCB. The molecular dynamic results indicated the carboxylate structures had the strongest adsorption capacity. Moreover, the Ni²⁺ removal efficiency of KMnO₄ modified biomass decreased linearly with the increase of lignin content in biomass, while KMnO₄ modified lignin showed a good adsorption performance, indicating that the cross-linked structures between lignin and other components in the biomass could inhibit the adsorption capacity of PPCB.