Activation Of Peroxymonosulfate By CNT-TiO₂ Under UV-light For Degradation Of Organic Pollutants

Advanced oxidation technology?AOT?is widely used in wastewater treatment or environmental remediation,which can generate high reactive radicals in situ,such as·OH,¹O₂ and SO₄^·-.Sulfate radical-advanced oxidation technology?SR-AOT?is a new type of advanced oxidation technology that can activate persulfate?PS?or peroxymonosulfate?PMS?to generate SO₄^·-and other radicals for the oxidization of pollutants.The transition metal can effectively activate PMS,but there is a risk of inevitable metal leaching,which could cause pollution to the water body again.As the non-metal catalyst,carbonaceous catalysts showed the catalytic activity in the PMS activation without loading and doping metals,which have attracted the attention of researchers.However,the activation efficiency of current carbon materials will need to be improved.In addition,the photoactivation of PMS has advantages of clean and mild conditions,but it suffered from the low utilization of light energy.When the photocatalysts was applied as a carrier composite for transition metal or metal oxide-based catalysts in the UV/PMS system,the efficiency of the activation of PMS was increased.To address the mentioned problems,the carbon nanotubes and photocatalyst TiO₂ composite catalyst was prepared.Under the UV-light,the efficiency of PMS activation by UV/PMS/CNT-TiO₂ system was investigated.The reaction mechanism of the system to degrade organic pollutants was explored.The combination of different AOTs provides new thinking for PMS activation.The research content and results are as follows:?1?The composite catalyst CNT-TiO₂ was prepared by wet impregnation method,sol-gel method and hydration-dehydration method.The morphology and structure of the catalyst were characterized.The results showed that the morphology of the catalysts prepared by different methods is different,but TiO₂ was anatase type unaffected by the CNT doping.The all CNT-TiO₂ catalyst exhibited the absorption peak at a UV<380 nm.As a target pollutant,phenol was used to investigate the degradation performance of the composite catalyst prepared by different methods in pre-experiments.The catalyst prepared via hydration-dehydration method showed the best performance.?2?To examine catalytic degradation performance of the UV/PMS/CNT-TiO₂ system,phenol,sulfamethoxazole?SMZ?,atrazine?ATZ?and bisphenol A?BPA?were chosen as the target pollutants.The results showed that degradation of these pollutants is almost 90%in 30min,which could suggestion that the system is suitable for the degradation of various refractory organic pollutants.The first order kinetic rate constant of phenol degradation in UV/PMS/CNT-TiO₂ system is 0.18 min^-1,which was 23.7 times that of the Co₃O₄/PMS system(0.0076 min^-1).The catalytic degradation efficiency of the UV/PMS/CNT-TiO₂ system declined slightly when too much catalyst or PMS was employed.Meanwhile,the system has a wide initial pH range?3.19-9.13?for the degradation of phenol.After three recovery experiments,the phenol removal rate of the CNT-TiO₂ composite catalyst was close to 70%.?3?The reaction mechanism of the UV/PMS/CNT-TiO₂ system was estimated by radical quenching experiments,capture and determination of radical,electrochemical impedance spectroscopy?EIS?and photochemical experiments.The results show that there are two main radicals,SO₄^·-,·OH and ¹O₂.The electron transport resistance in the system is smaller than other systems.In the reaction system,CNT,as electron transport media,could transfer photoinduced electrons from photocatalyst to PMS for efficient activation of PMS.Meanwhile,the recombination of photogenerated electron-hole pairs was reduced,which is beneficial to the photocatalytic process.Finally,the catalytic degradation of organic pollutants by the UV/PMS/CNT-TiO₂ system was improved.