Enhanced As(III) transformation and removal with biochar/SnS2/phosphotungstic acid composites: Synergic effect of overcoming the electronic inertness of biochar and W2O3(AsO4)2 (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 SnS2 and further decorated with heteropoly acid. The introduction of SnS2 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/SnS2 can suppress recombination of e(-)h(+) carriers. The adsorption and photocatalysis experiments results showed that the efficiency of removing As(III) by biochar/SnS2/phosphotungstic acid (biochar/SnS2/PTA) systems was 1.5 times that of biochar/SnS2 systems, and the concentration of total arsenic in the biochar/SnS2/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 SO4 center dot- radicals to enhance the As(III) photooxidation performance.

Automated summary

The strategy proposed in this study for constructing carbon-based catalysts using Magnoliaceae root biomass as a carbon source, doped with SnS2 and decorated with heteropoly acid, can activate carbon atoms and enhance the photocatalytic performance for improved arsenic adsorption. The synergistic effect between SnS2 and phosphotungstic acid in suppressing carrier recombination was observed, leading to 1.5 times higher efficiency in arsenic removal compared to systems without phosphotungstic acid. The formation of As-POMs also facilitated simultaneous As(III) photooxidation and As(V) coprecipitation, significantly increasing the arsenic adsorption capacity.