Removal behavior and mechanisms of Cd(II) by a novel MnS loaded functional biochar: Influence of oxygenation

Abstract Porous functional biochar (fBC) from mill bran was fabricated and used as a supporting agent for loading manganese sulfide (MnS). The manganese sulfide loaded functional biochar (MnS-fBC) composite’s physicochemical properties and Cd(II) removal performance were examined. Various adsorption parameters such as pH, initial Cd(II) concentration, biochar dosage and temperature were adopted to examine the Cd(II) removal behavior. The dynamics of Cd(II) concentration and Mn(II) dissolution were monitored. Typical biphasic adsorption behavior where a fast initial-adsorption followed by a slow removal was observed in the experiments. The main mechanisms were found to be closely related to the oxygenation conditions. Thus, additional experiments were conducted to examine the influence of oxygenation as well as reaction dynamic and evolution. The Eh-pH diagrams were employed to interpret the results, which showed that the governing Cd(II) removal mechanisms including complexation with MnS/MnOx and formation of CdS varied in different DO settings and changed over time. The dissolution of Mn was controlled by solution pH, Cd(II) adsorption and redox potential of the solution. The present study demonstrates the feasibility of MnS-fBC composite as an efficient sorbent for Cd(II) removal from water.