Study On The Degradation Performance And Mechanism Of Two Kinds PPCPs By Activation Of Peroxymonosulfate With Functional LDHs

Pharmaceutical and personal care products（PPCPs）are a kind of emerging pollutants closely related to people’s production and life.PPCPs mainly exist in water environment,and are mainly antibiotic PPCPs in China.Ofloxacin（OFL）and sulfamethoxazole（SMX）can effectively prevent and treat bacterial disease of human and animal.Thus,they are widely used in medicine,animal husbandry,aquaculture and agriculture and other fields.However,they are discharged into water bodies in various forms through urine and faeces,because they are overused and cannot be effectively absorbed by humans and animals.At present,the existence of these two antibiotics has been detected in surface water,underground water and drinking water,and their long-term existence will cause bacteria to produce resistance genes,which is detrimental to human beings and the ecological environment.Therefore,it is very necessary to find an effective removal technology.Advanced oxidation processes（AOPs）have attracted more and more attention for their efficient and thorough removal of antibiotics.LDHs have become an ideal catalyst for AOPs because of their unique layered structure,composition adjustable,biocompatibility and multiple active sites.In this study,two kinds of efficient catalysts were obtained through introducing cobalt ion into the traditional Mg-Al layered bimetallic hydroxide（Mg-Al LDH）to synthesize the Co-Mg-Al layered bimetallic oxide（Co-Mg-Al LDO）and replacing the transition metal with lithium alkali metal to synthesize the Li-Al layered bimetallic hydroxide Li-Al LDH.After characterizing the physicochemical properties of the two catalysts such as crystal shape,microscopic morphology,specific surface area and surface composition,two catalytic systems were established and used for catalyzing the degradation of OFL and SMX respectively.The main research contents and results are as follows:（Ⅰ）In the Co-Mg-Al LDO/peroxymonosulfate（PMS）system,the catalyst exhibited efficient catalytic performance.Under the conditions of p H=6.72,0.8 m M PMS and 0.1g/L catalyst dosage,98.3%of OFL with an initial concentration of 30 mg/L was degraded within 40 min.The results of free radical quenching experiments and the electron paramagnetic resonance results indicated that there were mainly four kinds of active species,including hydroxyl radical（HO^·）,sulfate radical(SO₄^·-),singlet oxygen（¹O₂）and superoxide radical(O₂^·-),in the Co-Mg-Al LDO/PMS system.In addition,a reasonable reaction mechanism and OFL possible degradation pathway were both proposed for this system.The Co-Mg-Al LDO catalyst had outstanding reusable performance and chemical stability by cycling experiments and metal ion leaching experiments.The Co-Mg-Al LDO/PMS system,as expected,has great potential for efficient wastewater catalytic treatment.（Ⅱ）Li-Al LDHs are a unique group of LDHs and their applications have been attracted wide attention.A Li-Al LDH was prepared by the hydrothermal method and used to activate PMS for degrading SMX.It was found that 0.4 g/L catalysts,1.57 m M PMS and p H=11.00 were the optimal condition for the degradation process of the Li-Al LDH/PMS system at 30°C.Under this condition,the degradation rate of 80 mg/L SMX could reach 98.2%within 130 min.Meanwhile,the catalyst also showed superior stability and recoverability.After five cycles,the degradation rate of SMX was still higher than95.3%.Based on free radical scavenging experiments and electron spin resonance results both the radical and nonradical pathways synergistically completed the degradation in the Li-Al LDH/PMS system,with the non-free radical（¹O₂）playing the predominant role.A reasonable degradation pathway was also proposed based on the detection of intermediates in the degradation process.In the actual wastewater treatment process,this efficient system served as a reference for Li-Al LDH as a catalyst to activate PMS to degrade SMX,as well as other antibiotics.