Strong degradation of orange II by activation of peroxymonosulfate using combination of ferrous ion and zero-valent copper

Abstract

• Fe(II) coupled with ZVC boosted PMS to degrade orange II. • Fe(II)/ZVC/PMS system exhibited high removal of TOC for orange II. • Fe(III)/Fe(II) cycle was promoted by Cu(I) and ZVC. • Cu(III), OH and SO 4 − were the main oxidants in the Fe(II)/ZVC/PMS system. • Orange II in actual sample was greatly degraded in Fe(II)/ZVC/PMS system. Zero-valent copper activated peroxymonosulfate (ZVC/PMS) system was widely used to degrade refractory contaminants due to being highly effective. However, the low reactivity and easy dismutation of cuprous species (Cu(I)) in acid condition limited its efficiency. In our study, ZVC coupled with ferrous ion (Fe(II)) promoted PMS to degrade orange II. Multiple oxidants including Cu(III), OH and SO 4 − made main contribution on orange II degradation in the Fe(II)/ZVC/PMS system. In the Fe(II)/ZVC/PMS system, ZVC generated Cu(I) by H + corrosion and PMS oxidation, and Cu(I) reacted with oxygen producing hydrogen peroxide. Then, Fe(II) and Cu(I) catalyzed hydrogen peroxide and PMS to generate Cu(III), OH and SO 4 − , and thereinto Fe(III) was reduced to Fe(II) by ZVC and Cu(I). In the Fe(II)/ZVC/PMS system, water matrix including humic acid, sulfate and nitrate had no significant impact on orange II degradation, while chloride restrained the degradation of orange II. The Fe(II)/ZVC/PMS system exhibited great degradation for orange II in tap water, lake water and well water. Additionally, the Fe(II)/ZVC/PMS system degraded more than 90% of methyl orange, rhodamine B, acetaminophen, ibuprofen, propranolol and diclofenac. Through adjusting the final reaction solution to pH 8.5 and subsiding, the discharge of total copper met the II-level environmental quality standards for surface water in China (1 mg/L). Hence, the study provided a promising method to induce PMS for enhanced degradation of contaminants.