Incorporation of TiO₂ Immobilized Waste Based Fe-Clay Beads Exhibiting In-situ Hybrid Behaviour Towards Paraquat Degradation

In this study, environmentally considerate Fe-rich clay beads were synthesized incorporating industrially generated waste by-products i.e., Red Mud and Foundry Sand as Fe sources. Further, the beads were successfully coated with metal, non-metal and metal-non-metal modified TiO₂ which exhibited excellent degradation towards class II-moderately hazardous-herbicide i.e., Paraquat (PQ). The leaching of Fe from the clay beads at natural pH of PQ (photo-Fenton) and the catalytic behavior of modified TiO₂ under sunlight (photocatalysis) resulted in an in-situ hybrid process. This work displays a clear comparison between photo-Fenton, photocatalysis, and hybrid process for treating 25 ppm of PQ solution in fixed mode. Within 60 min, 79% PQ degradation was encountered by hybrid process using TiO₂ beads which significantly increased to 93% by modifying TiO₂ coating with Fe and S. From kinetics data, 27% synergy was achieved with coated beads pertaining to the dual behavior. Further, the beads displayed stability up to 50 cycles, and the same was confirmed from the FTIR, XRD, and FESEM-EDX analysis displaying the efficacy of this technique for practical application in real life. Also, 76% mineralization along with the formation of simpler, non-toxic species at the end of the process confirms the process to be safe for the environment.