The Mn3O4/biochar composite prepared from straw biochar and divalent manganese: investigation of synthetic conditions and malachite green degradation

Abstract

In this study, the goal was to recycle and reuse manganese in wastewater by use of a cheap material biochar, ammonia, and hydrogen peroxide to produce a Mn₃O₄/biochar composite, which could be used for the degradation of dye in wastewater (MG has been selected as a candidate dye mode here). The experiment condition of was optimized, and Mn₃O₄/biochar composite has been characterized by TEM, XRD, XPS and N₂ adsorption–desorption. The kinetics and isotherm of malachite green (MG) degradation were well described by the pseudo-second-order and pseudo-first-order kinetic modes, indicating that as prepared MBC both have good adsorption and photocatalytic capacity due to its component of biochar and Mn₃O₄. The maximum MG degradation capacity of MBC is 248.0 mg g⁻¹, which has a significant advantage compared with single biochar (160.9 mg g⁻¹). Above all, straw biochar, an agricultural waste product, has been used to recycle industrial heavy metal, which achieves the goal of “the method of waste control by waste”.