Synergy effect between tetracycline and Cr(VI) on combined pollution systems driving biochar-templated Fe3O4@SiO2/TiO2/g-C3N4 composites for enhanced removal of pollutants

Biochar-coupled Fe3O4@SiO2/TiO2/g-C3N4 composites were successfully constructed through simple sol-gel and calcination methods. The composites efficiently removed high-concentration toxic tetracycline (TC) by means of middotOH and middotO(2)(-), whose removal rate exhibited 91.88% during 3 h, and the degradation rate constant reached up to 0.0068 min(-1). The excellent performance can be attributed to the high specific surface area, enhanced visible light response, the introduction of magnetic nanoparticles and biochars expediting charge transfer, Z-scheme heterojunction enhancing the spatial separation of photo-generate carriers and, importantly extraordinary adsorption capacity of 147.96 mg g(-1). Moreover, the composites showed the most excellent efficiency under the calcination temperature of 450 ?, and exhibited good stability with tolerance to a wide range of pH and anions. Interestingly, a synergistic photocatalytic effect was discovered in the TC/Cr(VI) combined pollution systems, resulting in significantly improved removal of Cr(VI). Besides, the photocatalytic mechanism and degradation path of tetracycline were also elucidated. All these findings suggested the as-synthesized catalyst was an excellent photocatalyst for removal of TC/Cr(VI)-contaminated water.

Automated summary

Biochar-coupled Fe3O4@SiO2/TiO2/g-C3N4 composites were successfully synthesized and exhibited excellent performance in removing high-concentration tetracycline (TC) through middotOH and middotO(2)(-) generation. The composites showed a removal rate of 91.88% within 3 hours and a degradation rate constant of 0.0068 min(-1). The outstanding performance was attributed to factors such as high specific surface area, enhanced visible light response, introduction of magnetic nanoparticles and biochars, Z-scheme heterojunction, and extraordinary adsorption capacity.