Effects of magnesium impregnation on stability and sorption performance of biochar derived from sawdust and corn husks

Biochar was derived from MgCl ₂ and MgO pretreated sawdust and corn husks at 300°C and 600°C, respectively, to investigate the effects of exogenous minerals on the stability and sorption performance of the resulting biochar. Impregnation with Mg decreased carbon concentration, increased yield and ash concentration, and increased the pH values at the point of zero charge (pH _PZC ) of the resulting biochar. The chemical stability of biochar oxidized by K ₂ CrO ₇ was enhanced with increasing pyrolysis temperature and decreased with the pretreatment of MgCl ₂ and MgO. Mg-impregnation enhanced carbon loss of the resulting biochar and increased the sorption capacity of biochar for CR significantly, which is potentially caused by electrostatic interaction and surface complexation. This study indicates that magnesium-impregnation significantly enhances the sorption performance of anionic contaminants and the pyrolysis temperature has a greater effect on the stability of the resulting biochar than the magnesium-impregnation.