Study On The Application Of Novel Iron-based Catalysts In Advanced Oxidation Processes For Degradation Of Organic Contaminants

With the rapid development of various industrial fields in China,the yields and consumptions of organic chemical products such as dyes and antibiotics are increasing,but resulting in more severe environmental pollution.Advanced oxidation processes are common methods to treat organic pollutants with weak degradability.Among them,persulfate oxidation method has attracted extensive attention because of its advantages such as high treatment efficiency,strong oxidation capacity and wide application range.Iron-based materials can activate persulfate（PS）or peroxymonosulfate（PMS）to produce free radicals like·SO₄^-,thus often used in advanced oxidation systems to improve the degradation efficiency of organic pollutants.However,the frequently used iron-based catalysts like zero valent iron and magnetite usually have some disadvantages,such as poor stability and high iron leaching level,which may affect their recycling and aggravate the secondary pollution.In order to solve the above common problems of iron-bearing materials and promote their research progress in organic wastewater treatment,two novel iron-based catalysts,carbide slag ferrosilicon and nontronite,are proposed in this paper.Firstly,the composition and physicochemical properties of carbide slag ferrosilicon and nontronite catalysts were tested and analyzed,then two advanced oxidation systems ferrosilicon/PMS and nontronite/NaHSO₃ were constructed and utilized to degrade organic dyes and antibiotics in water respectively.The performance of these two catalytic systems in organic pollutant treatment was reflected through a series of degradation experiments and the reaction mechanisms of them were also explored.The obtained main conclusions are as follows:（1）Ferrosilicon from carbide slag had high iron proportion and strong magnetism.This ferrosilicon sample was used to activate PMS for degradation of the typical dye methylene blue.After reacting for 45 min under light irradiation,this system could remove 99.90%of methylene blue in the solution.In addition,carbide slag ferrosilicon could achieve efficient removal of methylene blue in five cycle catalyzing processes and its iron leaching rate was much lower than that of zero valent iron,showing strong catalytic activity and stability.In the ferrosilicon/PMS/light system,PMS could be activated by ferrosilicon and light radiation simultaneously to produce a large amount of·SO₄^-,which played the dominant role in dye degradation.（2）Two nontronite samples NNT1 and NNT2 with different iron content were prepared by hydrothermal synthesis.The main phases of two samples were nontronite clay and both had high purity.When activating NaHSO₃ to degrade tetracycline,NNT2sample showed higher catalytic efficiency due to its higher structural iron content and the tetracycline removal was more than 95%after 60 min reaction.Besides,the nontronite catalyst also exhibited great catalytic stability and low iron leaching concentration in the cyclic catalyzing experiments.·SO₄^-was the main active specie of nontronite/NaHSO₃ system,and meanwhile·OH radicals also participated in the decomposition of tetracycline molecules.