Magnetic NiFe2O4/TiO2 heterostructures for the photocatalytic decontamination of glyphosate in water

Abstract

This work investigated the synthesis and photocatalytic performance of NiFe2O4/TiO2 heterostructures for the decontamination of glyphosate in water. The adapted Pechini method effectively produced NiFe2O4/TiO2 structures. Doping TiO2 with Fe and its association with NiFe2O4 promoted the formation of the rutile phase. FTIR analysis confirmed the presence of Fe3+ ions in tetrahedral sites and Fe3+ and Ni2+ ions in octahedral sites, supporting the formation of an inverted spinel-type structure. SEM-EDS analysis revealed non-homogeneous TiO2 coating on the magnetic structures. Pure oxides (NiFe2O4 and TiO2) displayed homogeneous atomic distribution. NiFe2O4/TiO2 demonstrated superior photocatalytic performance compared to individual oxides, attributed to decreased electron-hole pair recombination as evidenced by photoluminescence results. Sample NiFe2O4/TiO2 displayed photocatalytic activity in the decomposition reaction, leading to a significant increase in phosphate ion concentration by a factor of 4 within 90 min. The H2O2 addition enhanced glyphosate degradation by scavenging electrons, reducing recombination, and increasing hydroxyl radical formation. The concentration of phosphate ions increased by 96 times with the use of H2O2. The photostability test performed using the best catalyst indicated a decrease in the photoactivity from the second photocatalytic cycle onwards. The catalyst exhibited toxicity only for A. salina, suggesting its sensitivity to Fe and TiO2. No toxicity was observed in L. minor and L. sativa seeds.