Study of Degrading Acid Orange 7(AO7) by Activated Peroxymonosulfate (PMS) with Waste Cast Iron (WCAI) as Catalyst

Abstract

Heterogeneousperoxymonosulfate (PMS) activation systems have become the promising options forwater treatmentowing to the advantage of overcoming the tremendous loss of dissolved metal ions. Nevertheless, heterogeneouscatalysts were mainly obtained via synthesis that was involved with harsh conditions and high cost, therebylimiting practical application.Hence, cheap, efficient and environmentally friendly heterogeneous catalysts are attractive.In this study, scrap cast iron (WCAI) was collected and directly adopted as catalyst for PMS’ degradation of azo dye Acid Orange 7 (AO7). The effect of WCAI and PMS dosage on WCAI/PMS was investigated and then the optimum addition of 0.1g/L PMS and 0.2g/L WCAI was determined. The results showed that WCAI could effectively activate PMS to remove AO7, under the optimum concentration of WCAI and PMS, 96.9% AO7 could be completely removed within 30 min. Quenching experiments reveal that the active constituents in WCAI/PMS system, more elaborately,•OH and SO4•−, SO4•−, play the dominant role for the oxidation of AO7. Moreover, the effect of solution pH and inorganic ions was further investigated. Acidic conditions were more conducive to the degradation process. Cl−, HCO3− and H2PO4− all exerted inhibition on the removal of AO7 by WCAI/PMS system, the effect of HCO3− was rather more significant than that of Cl− and HCO3−. This study provides the proof of the application based on iron-based catalyst mediated persulfate activation system for water treatment.