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

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 CO 3 2− 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 − , NO 3 − and SO 4 2− ) and humic acid (HA) did not significantly affect the removal of TC, especially HCO 3 − , which displayed a positive effect. Additionally, quenching experiments and electron paramagnetic resonance (EPR) analysis indicated that the degradation of TC involved radical (·OH and SO 4 ·- ) and nonradical ( 1 O 2 ) processes in the DLMT/PMS system, and the nonradical ( 1 O 2 ) 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. DLMT/PMS system exhibited a great catalytic capability for the degradation of TC with excellent pH buffering properties and high reusability. Activation PMS mechanism involved radical and nonradical processes, and the nonradical process was the major mechanism. • PMS was efficiently activated with low-cost dolomite (DLMT) to degrade TC. • The DLMT catalyst displayed great stability and excellent pH buffering properties. • 1 O 2 was the dominant reactive oxygen species in the DLMT/PMS system. • The mechanism of PMS activation and the degradation pathway of TC were proposed. • The DLMT/PMS system transformed TC molecules into harmless compounds.