Potential applications of ASR fly ash in photo-Fenton like process for the degradation of tetracycline at neutral pH: Fixed-bed approach

The current research work investigated the effective utilization of automobile shredder residue (ASR) fly ash as an alternative iron source to degrade recalcitrant organic pollutants like tetracycline (TC) via a visible-light-driven photo-Fenton-like process at neutral pH. The whole photodegradation process was carried out in a fixed mode by using highly durable ASR fly ash beads as the catalyst in the photo-Fenton reaction. As confirmed through several characterization techniques, these beads contained hematite, goethite, magnetite, pyrite and wustite forms of iron oxides. Moreover, iron cations (Fe2+ and Fe3+) had leached out from the ASR fly ash beads during the reaction, which further promoted the photo-Fenton process. The detailed mechanism for the photodegradation of TC using ASR fly ash beads was studied. The high photodegradation efficiency of TC after 3 h of natural solar irradiation further confirmed the real-time applications of ASR fly ash in wastewater treatment. The ASR fly ash beads remained active and stable even after 10 recycling tests, as cross confirmed through characterization tests. Therefore, the obtained results clearly indicated that the use of ASR fly ash in wastewater treatment can add value to waste while providing a low cost and sustainable solution to various industries.