Switching Peroxymonosulfate Activation Of Fe-Al Layered Double Hydroxide By Modified Activated Carbon:Performance And Mechanism

Antibiotics were widely used in daily life due to their high antibacterial properties,but their residue pollution seriously endangered human health and ecological stability.The development of green and efficient technologies to control antibiotic pollution was one of the main topics for researchers.The advanced oxidation process based on SO₄^·-could efficiently degrade and even mineralize organic pollutants in water bodies,which showed broad application prospects in the field of pollution control in water bodies.In this paper,a series of supported catalysts were prepared by using the unique structure of layered double hydroxide and the special physical and chemical properties of modified activated carbon.In this topic,the loading phosphoric acid modified activated carbon（PAC）enhanced the activation performance of layered double hydroxide（Fe Al-LDH）on peroxymonosulfate（PMS）and changed its catalytic mechanism.Four materials were synthesized by hydrothermal method by loading concentrated nitric acid modified activated carbon,sodium hydroxide modified activated carbon and phosphoric acid modified activated carbon.The results of adsorption and degradation experiments on tetracycline showed that compared with Fe AL-LDH,NAC@Fe Al-LDH and Na AC@Fe Al-LDH,PAC@Fe Al-LDH nanocomposite has the best PMS activation activity which 98.61%of tetracycline(TC,20mg·L^-1)could be removed within 14min in PAC@Fe Al-LDH/PMS system while that of Fe Al-LDH/PMS system was just 69.29%.The optimal reaction conditions have been determined through research to be 200mg·L^-1PMS,200mg·L^-1catalyst,solution initial p H=7 and reaction temperature of 40℃.Besides,the results of coexisting anion interference test showed that SO₄^2-and NO₃^-had no obvious effect on the degradation efficiency of TC,while HA,HCO₃^-and Cl^-had different degrees of inhibition on the degradation efficiency of TC.The results of quenching experiments and electron paramagnetic resonance（EPR）demonstrated that the main catalytic process switched from pathways of non-radicals（¹O₂）and free radicals(·OH,SO4^·-and O₂^·-)together to pathway of non-radicals（¹O₂）as PAC was introduced into the Fe Al-LDH/PMS system,also enhanced the activation performance of Fe Al-LDH for PMS.Besides,the carbon-based catalyst still had high stability after four runs,which indicated that the materials had potential for application in the field of actual environmental remediation.