Synergic effect of CuS and MgO for boosting adsorption-photocatalytic activity of S-doped biochar

Adsorption coupled with photocatalysis is a promising route to remove dyes from wastewater. Biochar was modified with S, CuS, and MgO (CuS–Mg/S-BC) through one-pot sulfurization to boost the adsorption and photocatalytic removal of rhodamine B (RhB). The abundant functional groups as well as vacant sites formed at the junction interface among S-doped biochar, CuS, and MgO favored RhB adsorption and photon capture, and this tight interface increased the separation and transfer of photoinduced e−-h+ pairs. Hence, CuS–Mg/S-BC exhibited greater removal efficiency than S-doped biochar, 2-CuS/S-BC (The biochar is loaded with 5 % CuS), and b-Mg/S-BC (The biochar is loaded with 5 % MgO). Langmuir and second-order models well described the adsorption isotherms and kinetics, respectively of CuS–Mg/S-BC composites. 2 b-CuS-Mg/S-BC (Biochar is loaded with both 5 % CuS and MgO) exhibited a removal efficiency of 95.70 % within 120 min, and qe estimated from the second-order model was 981.67 mg g−1. For a 220 mg L−1 RhB solution, the removal efficiency and the adsorption efficiency decreased from 95.70 % to 87.01 % and from 83.54 % to 76.17 %, respectively, after seven cycles.