Efficient copper removal using low-cost H3PO4 impregnated red-gram biochar-MnO2 nanocomposites

Abstract

Copper metal removal from wastewater is an essential step to detoxify wastewater before release into human contact. To serve the same purpose, H3PO4 impregnated and KMnO4 functionalised, red-gram seed coat biochar is synthesized, for efficient and economic biosorption of aqueous copper ions. Response Surface Methodology (RSM) is employed to achieve a high optimal adsorption capacity of 493.34 mg/g, using a low adsorbent dosage of 0.6 g/L in only 90 min. Pre- and post-adsorption characterization of the adsorbent was done using XRD & XPS spectroscopy, FE-SEM, TGA and BET analysis to study its microstructure and mechanism of adsorption. A high mesoporous surface area of 207 m2/g and the negatively charged moieties on the surface help in complexation of the ions by reduced monolayer chemisorption. Cyclic regeneration of the adsorbent was studied to assess the adsorption efficiency, which retained a value as high as 70 % after 3 adsorption-desorption cycles.