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
Bowen Yang, Jiawei Dai, Yuan Zhao, Zhanchao Wang, Jingwei Wu, Caiya Ji, Yuhu Zhang, Pu Xiao
Abstract
Abstract Biochar-coupled Fe 3 O 4 @SiO 2 /TiO 2 /g-C 3 N 4 composites were successfully constructed through simple sol–gel and calcination methods. The composites efficiently removed high-concentration toxic tetracycline (TC) by means of ·OH and · $${\rm O}_2^{-}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mi>O</mml:mi> <mml:mn>2</mml:mn> <mml:mo>-</mml:mo> </mml:msubsup> </mml:math> , 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. Graphical Abstract