Bi-functional biochar-g-C3N4-MgO composites for simultaneously minimizing pollution：Photocatalytic degradation of pesticide and phosphorus recovery as slow-release fertilizer.

Significant progress has been made in the development of phosphorus recovery adsorbents and photocatalysts for degradation of pesticides. However, the bifunctional materials for phosphorus recovery and photocatalytic degradation of pesticides have not been designed, and the mechanism of the interaction between photocatalysis and P adsorption remains unexplored. Herein, we develop biochar-g-C3N4-MgO composites (BC-g-C3N4-MgO) with bi-function application to minimize water toxicity and eutrophication. The results show phosphorus adsorption capacity of the BC-g-C3N4-MgO composite reaches 111.0 mg·g-1, and its degradation ratio of dinotefuran reaches 80.1% within 260 min. The mechanism studies show that MgO can play variety roles in BC-g-C3N4-MgO composite, in which can improve the adsorption capacity of phosphorus, enhance the utilization efficiency of visible light and the separation efficiency of photoinduced electron-hole pairs. The biochar existed in BC-g-C3N4-MgO serves as charge transporter with a good conductivity, which promotes the fluent transfer of photo-generated charge carriers. The ESR indicates that both •O2- and •OH generated from BC-g-C3N4-MgO are responsible for dinotefuran degradation. Finally, pot experiments reveal that P laden BC-g-C3N4-MgO promotes the growth of pepper seedlings with high P utilization efficiency of 49.27%.