Remediation Of Sulfathiazole Contaminated Soil By Peroxymonosulfate:Performance,Mechanism And Phytotoxicity

Sulfathiazole（STZ）is a typical sulfonamide antibiotic.It is mainly used to treat diseases such as digestive tract and respiratory tract infections caused by sensitive bacteria in livestock breeding or livestock.However,due to incomplete digestion of animals,its high concentration of drug residues found in water and soil environments in different parts of the world.Although many methods have been developed to deal with SAs in the environment,the vast majority of studies have been conducted with the aqueous phase as the research medium,and studies on how to degrade STZ in soil and the potential impact of STZ on soil health are scarce.Peroxymonosulfate（PMS）has been successfully used to remove organic pollutants from water,but is rarely used in soil remediation.In addition,in previous studies,PMS can be activated by different methods such as transition metal,ultraviolet（UV）,ultrasonic（US）,and pyrolysis to generate strong oxidizing substances such as SO₄^·-and HO·,thereby efficiently decomposing organic pollutants.But additional reagent addition or energy input not only increases the system operating cost,but may also increase potential environmental risks,thus limiting its universality for practical applications.Therefore,numerous reports are devoted to using PMS alone to degrade pollutants in the environment,and studies have found that the PMS direct oxidation process has excellent performance and can effectively degrade organic pollutants without electronic mediators,catalysts or external energy.In addition,studies have shown that non-radical species with mild oxidation potentials such as ¹O₂ have higher substrate specificity and better resistance to conventional active species such as SO₄^·-and HO·produced by traditional PS-AOPs.In conclusion,the use of PMS alone for STZ treatment in soil seems to be a promising treatment technology,and to the best of our knowledge,this is the first attempt to use PMS for STZ-contaminated soil.The main findings are as follows:（1）The asymmetric molecular structure and stronger oxidation of PMS make it have better STZ degradation ability than PDS and H₂O₂,4 mmol/L PMS can degrade96.54%of STZ in the soil within 60 min.PMS had an excellent performance for STZ removal at various concentration levels of STZ.Quenching and probe experiments revealed that ¹O₂ rather than SO₄^·-and HO·was the predominant reactive oxygen species responsible for STZ removal.In addition,the possible degradation intermediates and degradation pathways of the oxidation system were proposed by LC/MS analysis.（2）When the initial pH value of the reaction was in the range of 3.21-9.00,the degradation of STZ in soil by PMS showed an ideal degradation effect,and when the p H value increased to 10.96,the degradation efficiency of STZ decreased significantly;PMS can effectively degrade STZ in the soil temperature range at 10°C-40°C;The presence of Cl^-,SO₄^2-,NO₃^-,Fe³⁺,and HA enhanced the degradation efficiency of STZ,while HCO₃^-and Mn²⁺presented an obstructive effect on STZ elimination at high concentrations.（3）Different chemical extraction procedures were used to determine the bioavailability of the heavy metals,PMS oxidation process caused unnoticeable influence of the concentrations of heavy metals except for the increase of Mn concentration and the decrease of Ba concentration.Moreover,the germination rate and stem length of wheat and radish both increased,indicating PMS oxidation reduced the toxicity of STZ,and the increase of Mn concentration did not cause negative impact on their growth.Besides,the results of XRD and FTIR tests showed oxidation processes had negligible impacts on soil structure and composition.In this study,the mechanism of degradation of STZ by PMS and the factors affecting its efficiency were systematically analyzed,and the effects of the remediation system on the original physiochemical properties of soil were discussed in combination with specific experiments.The research results show that PMS can effectively remove antibiotic residues in the soil environment,which is of great significance to restore soil ecological health.It can be applied to soil pollution control in different regions,and provide a reliable method reference for other pollutants.