Degradation of organic pollutants in natural magnetite-activated peroxymonosulfate system enhanced by hydroxylamine: Catalytic performance, reaction pathway, and enhancement mechanism

Abstract

The degradation of organic pollutants using natural minerals in advanced oxidation process gains increasing interest due to abundant resources, rich active metals, and easy engineered preparation, but it is limited by the relatively low catalytic performance of natural minerals. The enhanced pollutant degradation in natural mineral/peroxymonosulfate (PMS) system has been rarely studied. In this work, the enhancement of hydroxylamine natural magnetite/PMS system was innovatively proposed. In comparison with the natural magnetite/PMS system, the degradation efficiency of Rhodamine B (RhB) was increased by 61.82 % after the addition of hydroxylamine, and the RhB degradation followed a pseudo-first-order kinetic model with a rate constant of 0.1040 min−1. The Fe2+/Fe3+ conversion efficiency was improved by the synergistic effect of hydroxylamine, which was demonstrated by X-ray photoelectron spectroscopy and determination of the Fe2+ concentration in the reaction system. The influence of process factors on the degradation process was examined, including hydroxylamine concentration, catalyst dosage, PMS concentration, initial pH, temperature, inorganic anions, and humic acid. The hydroxylamine-assisted natural magnetite/PMS system exhibited a wider pH range (3−11) and good reusability (degradation efficiency of 90.30 % for the seventh run). Besides, the effective degradation of different organic pollutants was obtained, including methyl organic, malachite green, tetracycline, sulfadiazine, and ofloxacin. Sulfate radical, hydroxyl radical, and singlet oxygen were mainly reactive oxygen species in the reaction system. The energy consumption was only 4.33 kWh/kg, significantly lower than previously reported systems, showing a significant environmental application value.