Study On The Efficiency And Mechanism Of Removal Of Typical Trace Contaminants In Groundwater By Iron-manganese Composite Oxide Filter

Groundwater is an extremely important fresh water resource for human beings.However,with the rapid development of the economy,the demand for groundwater by industry,agriculture and human life is increasing.Due to weak supervision,it has brought uncontrolled groundwater extraction and severe groundwater pollution.At present,more than 200 kinds of organic pollutants have been detected in groundwater,and the types and quantities of organic pollutants are still increasing rapidly.Organic pollution in groundwater poses a serious threat to drinking water safety,and the management of organic pollution in groundwater needs urgent solution.It has been reported that iron-manganese oxides have good adsorption and oxidation effects on many organic pollutants,such as phenols and antibiotics.The research team prepared an iron-manganese composite oxide on the surface of the quartz sand filter.At present,the mechanism of iron-manganese co-oxide filter media removing conventional inorganic pollutants has been clarified,but the removal effect and mechanism of new organic pollutants are still unclear.In this study,the iron-manganese co-oxide filter media were adopted from a pilot-scale water treatment plant,and typical organic pollutants in groundwater bisphenol A and tetracycline were selected as target pollutants.Firstly,the purpose of this project is to explore the effectiveness and influencing factors of the removal of typical organic pollutants bisphenol A and tetracycline in groundwater by iron-manganese co-oxide filter media.Secondly,the acute toxicity changes of iron-manganese co-oxide filter media in the process of removing typical organic pollutants in groundwater were investigated by water quality acute toxicity luminescence bacteria method.Based on a series of micro-characterization results of the surface of the iron-manganese co-oxide filter media,the mechanism of the removal of organic pollutants bisphenol A and tetracycline by the iron-manganese co-oxide filter media was analyzed.In addition,the effect of iron-manganese co-oxide filter media on the simultaneous removal of inorganic pollutant manganese and organic pollutant bisphenol A and tetracycline was investigated.The main research results are as follows:（1）Through small-scale experiments,40g iron-manganese co-oxide filter media can cumulatively remove about 601.70mg bisphenol A and 149.45mg tetracycline.It is proved that the iron-manganese co-oxide filter media can effectively remove the organic pollutants bisphenol A and tetracycline in the environment of the incoming water（underground raw water）of the Xi’an Beijiao Water Plant.（2）The factors influencing the removal of bisphenol A and tetracycline from the iron-manganese co-oxide filter media was initially identified:the more the quality of the iron-manganese co-oxide filter media,the higher the removal rate of bisphenol A and tetracycline;Increasing the initial concentration of bisphenol A and tetracycline has little effect on the removal of bisphenol A and tetracycline by the iron-manganese co-oxide filter media,and the higher the initial concentration,the more qe;when the common coexisting cations Mg²⁺,Ca²⁺,and K⁺concentration are At 0.01mol/L,Mg²⁺,Ca²⁺,and K⁺had no significant effect on the removal of bisphenol A,and Ca²⁺and K⁺had no significant effect on the removal of tetracycline.However,Mg²⁺and tetracycline competed for active sites and affected the removal rate of tetracycline.When the oxygen concentration is lower than 0.3mg/L,it can inhibit the removal of bisphenol A and tetracycline.（3）The reaction kinetics during the removal of bisphenol A and tetracycline from the iron-manganese co-oxide filter media was clarified.The process of removing bisphenol A from the iron-manganese co-oxide filter media complies with the quasi-secondary reaction kinetic equation,k₂ is 4.404g/（mg·min）,the theoretical equilibrium adsorption capacity is 0.9936 mg/g,and R² is 0.9649;The process of removing tetracycline by iron-manganese co-oxide filter media complies with the quasi-secondary reaction kinetic equation,k₂ is 4.404g/（mg·min）,the theoretical equilibrium adsorption capacity is 0.03438 mg/g,and R² is 0.9936.（4）Explore the micro changes of the iron-manganese co-oxide filter media through micro-characterization.It was found that the morphology and crystal structure of bisphenol A and tetracycline did not change significantly,but the functional groups on the surface of the iron-manganese co-oxide filter media were changed.Based on the change of TOC and removal rate during the removal of bisphenol A and tetracycline by iron-manganese co-oxide filter media,it is proved that the removal of bisphenol A and tetracycline by iron-manganese co-oxide filter media is a process of adsorption and oxidation.Three steps of the process of removing bisphenol A and tetracycline from iron-manganese co-oxide filter media were proposed.Firstly,bisphenol A and tetracycline are adsorbed on the surface of the iron-manganese co-oxide filter media to form a surface complex.Then,electron transfer was carried out between iron-manganese composite oxide and surface complex,and bisphenol A and tetracycline were oxidized.Finally,part of the reactant intermediate is desorbed,and part of the reactant and the reactant intermediate are adsorbed on the surface of the iron-manganese composite oxide.