Effect of Anions and Cations on Tartrazine Removal by the Zero-Valent Iron/Peroxymonosulfate Process: Efficiency and Major Radicals

Zero-valent iron/peroxymonosulfate (Fe0/PMS) has been considered as a promising approach for wastewater treatment. Anions and cations are widely present in wastewater and have significant effects on the performance of the Fe0/PMS system for wastewater treatment. Thus, in the present study, tartrazine was selected as the target model; SO42−, NO3−, HCO3−, and Cl− were selected as representative anions and Ca2+, Cu2+, Mg2+, and Mn2+ were chosen as representative cations. The effect of these anions and cations on tartrazine removal and major radicals in the Fe0/PMS were systematically investigated. The presence of a certain concentration of SO42− and Cl− had positive, NO3− had negative, and HCO3− had negligible effects on tartrazine removal in the Fe0/PMS system. SO42− and HCO3− had a small effect on the contribution proportion of reduction, SO4•− and •OH; a certain concentration of Cl− could enhance the contribution proportion of •OH; and NO3− would decrease the contribution proportion of SO4•− and •OH. A certain concentration of each of Ca2+, Cu2+, Mg2+, and Mn2+ could enhance the tartrazine removal in the Fe0/PMS system. Ca2+, Cu2+, and Mg2+ had no effect of the contribution of reduction, SO4•− and •OH, while a certain concentration of Mn2+ could enhance the contribution proportion of SO4•−. These results can provide some references for the Fe0/PMS system to treat actual wastewater containing anions and cations.