Enhanced As(III) transformation and removal with biochar/SnS/phosphotungstic acid composites: Synergic effect of overcoming the electronic inertness of biochar and WO(AsO) (As(V)-POMs) coprecipitation.

The activation of carbon atoms in biochar is an important approach for realizing the reuse of discarded woody biomass resources. In this work, a strategy for the construction of carbon-based catalysts was proposed with Magnoliaceae root biomass as a carbon source, doped by SnS and further decorated with heteropoly acid. The introduction of SnS can activate the carbon atom and destroy the electronic inertness of the disordered biochar with 002 planes. In addition, the synergy between the Keggin unit of phosphotungstic acid and biochar/SnS can suppress recombination of e-h carriers. The adsorption and photocatalysis experiments results showed that the efficiency of removing As(III) by biochar/SnS/phosphotungstic acid (biochar/SnS/PTA) systems was 1.5 times that of biochar/SnS systems, and the concentration of total arsenic in the biochar/SnS/PTA composite system gradually decreased during the photocatalysis process. The formation of As-POMs can simultaneously realize As(III) photooxidation and As(V) coprecipitation. The phase transfer of arsenic by As-POMs could significantly increase the As adsorption capacity. Specifically, the composites achieved the conversion of S atoms at the interface of biochar into SO radicals to enhance the As(III) photooxidation performance.