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

ABSTRACT

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.

GRAPHICAL ABSTRACT

KEYWORDS:

• Adsorption
• Ni²⁺
• KMnO₄ modification
• Biomass
• Water treatment

Acknowledgements

The assistance from the Analytical and Testing Center of Huazhong University of Science and Technology is acknowledged.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (NSFC) [grant numbers 51976074, 51750110496), China Postdoctoral Science Foundation Funded Project [grant number 2020M672352].