The role of typical inorganic anions on the transformation of dissolved organic matters in catalytic ozonation

Abstract

Heterogeneous catalytic ozonation (HCO) is an effective technology for the advanced treatment of various industrial wastewater. The effect of different anions on dissolved organic matter (DOM) reactivity during the HCO process might vary considerably. However, the impact of this DOM conversion process induced by inorganic anions remains unclear. Herein, the effect of HCO₃⁻ and SO₄²⁻ on DOM molecular changes in petrochemical wastewater by HCO was systematically investigated using spectroscopy, resin fraction, and FT–ICR MS techniques. HCO₃⁻ showed stronger inhibition of organics on degradation than SO₄²⁻, primarily due to the scavenging of reactive oxygen species. Moreover, HCO₃⁻ and SO₄²⁻ favored the inhibition of hydrophobic fractions over hydrophilic fractions. At the molecular level, the similar effect of HCO₃⁻ and SO₄²⁻ on HCO favored the conversion of compounds with lignins/CRAM-like to aliphatic/proteins and aromatic structures. The higher reactivity of HCO + HCO₃⁻ with low-unsaturated and high-oxidized compounds resulted in reduced oxygen addition reactions. HCO + SO₄²⁻ promoted oxygen addition reactions due to facilitating the transformation of unsaturated DOM into more saturated aldehydes, ketones, and carboxylic acids. These findings highlight significant differences in HCO₃⁻ and SO₄²⁻ effects on DOM transformation during HCO. Our study provides molecular-level insights into the behavioral changes of DOM during HCO induced by inorganic anions, helping guide the optimization of HCO processes for treating actual industrial wastewater.