Rapid toxicity elimination of organic pollutants by the photocatalysis of environment-friendly and magnetically recoverable step-scheme SnFe2O4/ZnFe2O4 nano-heterojunctions

An efficient and environmentally-friendly photocatalytic degradation process by nontoxic and easily-recovered photocatalysts is desirable for wastewater treatment. Step-scheme (S-scheme) SnFe2O4/ZnFe2O4 nano-heterojunctions with nontoxicity, strong magnetism, and high visible-light photocatalytic performance were synthesized by one-step solvothermal strategy, and SnFe2O4 content was optimized. 5% SnFe2O4/ZnFe2O4 heterojunctions exhibited optimal visible-light photocatalytic performance in degrading tetracycline with 93.2% removal efficiency, and the COD of actual pharmaceutical wastewater decreased by 77.5% due to the efficient production of active species. Moreover, 5% SnFe2O4/ZnFe2O4 heterojunctions is very convenient to be recycled from solution using external magnetic field, and the photocatalytic activity remains almost unchanged in repeated use due to its strong magnetism and high stability. More significantly, the toxicity evaluation confirmed nontoxicity of SnFe2O4/ZnFe2O4 and rapid toxicity elimination process of tetracycline by photocatalysis, indicating that environment-friendly and magnetically recoverable S-scheme SnFe2O4/ZnFe2O4 heterojunction is a promising photocatalyst for wastewater treatment.