The Effect Mechanism Of Typical Aluminum Minerals On The Degradation Of Antibiotics By Peroxymonosulfate Activated

With the increasing demand for antibiotics,a large number of antibiotics are used in various fields.However,the added antibiotics are not fully used and have problems such as high toxicity and low biodegradability,which seriously endanger the soil and water ecosystem and human health.In order to effectively remediate antibiotic contaminants in wastewater,advanced oxidation processes（AOPs）based on peroxymonosulfate（PMS）are becoming increasingly attractive.Peroxymonosulfate catalysts are divided into transition metals and non-metal,which have some problems such as high catalyst costs and harsh preparation methods.Herein,it is crucial for the application of PMS system to construct abundant,environment friendly and low-cost PMS catalysts.This study was focused on the application potential of abundance element Al to activate PMS.The performance of Al and its mineral,which based on Alumina,clay Bauxite and spinel,in degrading sulfamethoxazole（SMX）by activating PMS was conducted.The effect mechanism of Al and its minerals to activate PMS was clarified.The results provide material basis and theoretical basis for remediation of antibiotic contamination by abundance elements catalysts/PMS system.The main research findings are as follows:（1）The efficiency of three oxidized（hydroxide）aluminum minerals such as Al OOH,α-Al₂O₃ andγ-Al₂O₃ to activate PMS by degrading SMX was investigated.The experiments showed that the degradation rate of SMX in Al OOH/PMS system（90%）is significantly higher than that ofα-Al₂O₃（50%）andγ-Al₂O₃（40%）.The quenching experiments and Electron Spin Resonance（ESR）proved that the main reactive oxygen species in Al OOH/PMS system was singlet oxygen（¹O₂）,which was generated through the SO₅^·-electron transfer pathway.TPD and Lewis active site inhibitor experiments proved that the Lewis acid-base hydroxyl groups on the surface of Al OOH are the key factors for degrading SMX.The ion effect experiments showed that the Al OOH/PMS system is less affected by water quality parameters.Combining with the characterization results of TG,SEM and XRD before and after the reaction,Al OOH minerals have a great cyclic stability.（2）Four natural aluminosilicate minerals:pyrophyllite,montmorillonite,kaolinite,and illite were used to investigate the effect of Al O₆ Lewis acid-base sites exposed on the edge of aluminum-based minerals structure to activate PMS by degrading SMX.The results showed that the degradation efficiency order of the four minerals is:pyrophyllite>illite>montmorillonite>kaolin,and the amount of exposed Al O₆ structure at the edge of pyrophyllite is more than other three minerals.The abundance element Fe was used as probe to verify that the key to activate PMS is the Al O₆ structure of Lewis acid-base sites exposed on the edge of Al-based minerals.The results showed that Fe-pyrophyllite can remove more than 99%of SMX.Combining with the characterization results of XRD,FTIR and TPD,the probe Fe is bonded to the Al-O active site,which results in the exposure of Lewis acid-base sites on the edge surface of pyrophyllite.Furthermore,according to the quenching experiment,ESR and active species generation experiment,the amount of ¹O₂ and SO₄^·-in Fe-pyrophyllite/PMS system were significantly increased.In addition,the generation amount of ¹O₂ which generated by this system is more than 8times by Al OOH/PMS system.It was confirmed that the Al O₆ Lewis acid-base sites which exposed on the edge of pyrophyllite can activate PMS to degrade SMX efficiently.Moreover,the Fe-pyrophyllite/PMS system is relatively insensitive to inorganic ions and has good cycling stability.（3）A green and safe method was developed to expose Lewis acid-base sites on the edge of aluminosilicate mineral.Na OH was used to remove the Si element at the edge of the montmorillonite to improve the degradation rate of SMX,and then the influence mechanism in alkali-activated montmorillonite/PMS system were explored.Alkali-activated montmorillonite can efficiently remove SMX in water,and the removal rate is as high as 90%within 120 minutes of reaction time.Based on the results of ICP-OES and TPD characterizations,Si in the alkalized montmorillonite mineral was dissolved and numerous Al-O bonds were exposed,-O-being the Lewis basic site.Through quenching experiments and ESR experiments,the amount of ¹O₂ generated from alkali-activated montmorillonite/PMS system was significantly increased,while the amount of free radicals was decreased by 3 times.The Lewis basic site on the edge of montmorillonite mineral is the key site for activating PMS to generate ¹O₂.According to the results of the performance of alkalized montmorillonite/PMS system in chloride ion environment,it is confirmed that this system has the advantages of high reaction efficiency,no secondary pollution,and environmentally friendly.（4）By adjusting the ratio of Mg-Al on the surface of Mg-Al spinel,the types of Lewis basic sites of Mg-Al spinel minerals are increased.Three magnesia-aluminum spinel（Mg Al-1,Mg Al-2 and Mg Al-3）were synthesized by a hydrothermal method,and their efficiency and influence mechanism of activating PMS to degrade SMX were investigated.The results showed that the degradation rate of SMX in the order of Mg Al-3（92.5%）>Mg Al-1（61.8%）≈Mg Al-2（61.4%）.Combining to XPS,Raman,and TPD,the oxygen-deficient Lewis-like basic sites on the surface of Mg Al-3 are the key for improving the degradation rate of SMX.The quenching experiment,the ESR experiment and active species content experiment,it was demonstrated that free radical and non-radical pathways are involved in the PMS activation process of Mg Al-3 minerals.The conventional Lewis basic sites promoted the self-decomposition of PMS to generate ¹O₂,and the oxygen-deficient Lewis-like basic sites is the key factor for activating PMS to generate free radicals.The Lewis acid sites played an essential role in enriching reaction yields for PMS and SMX.In conclusion,there is a new design concept and theoretical basis for the use of main group element minerals as a means of antibiotic wastewater remediation.