Dolomite as a low-cost peroxymonosulfate activator for the efficient degradation of tetracycline: Performance, mechanism and toxicity evolution

Abstract

Herein, natural dolomite (DLMT) was employed to activate peroxymonosulfate (PMS) for the removal of tetracycline (TC) in an aqueous solution. Under optimum conditions, the degradation efficiency of TC was 80.94 % within 60 min, which was more than twice that achieved by PMS oxidation alone (37.01 %). The enhanced degradation efficiency of TC was attributed to the release of CO32− by dissolved DLMT to form reactive oxygen species, and the DLMT/PMS system exhibited excellent pH buffering properties. Kinetic analysis of TC degradation followed a quasi-first-order kinetic model. The presence of coexisting inorganic anions (Cl−, NO3− and SO42−) and humic acid (HA) did not significantly affect the removal of TC, especially HCO3−, which displayed a positive effect. Additionally, quenching experiments and electron paramagnetic resonance (EPR) analysis indicated that the degradation of TC involved radical (·OH and SO4·-) and nonradical (1O2) processes in the DLMT/PMS system, and the nonradical (1O2) process was the major mechanism. Furthermore, two reasonable degradation pathways for TC were proposed by UPLC–MS analysis, including terminal oxidation, deamination, deacetylation, ring-opening and other ways. The toxicity of the TC catalytic degradation process could gradually decrease according to the quantitative structure-activity relationship (QSAR) prediction. This work provided a novel, green and low-cost PMS activator to degrade organic pollutants in practical water treatment.