Study On Adsorption And Degradation Efficiency Of PCE Based On The Growth Ring Of Water Suppiy Network

During the operation of the water supply pipe network,there will be physical,chemical,electrochemical and biological reactions within the pipeline,and the irregular ring-like mixture will appear along the inner wall of the pipeline,that is called pipeline growth ring.The pipeline growth ring is a mixture of precipitates,corrosive substances,sticky dirt and biofilm,and its main forms are: goethite,lepidocrocite and a small amount of Fe?OH?3 and Fe S and so on.Perchloroethylene is a kind of non-degradable and volatile chlorinated olefin compounds.PCE has been widely used in various living areas and production departments because of its strong ability to dissolve,excellent cleaning effect and good thermal stability,and become the main source of water pollution.PCE is more toxic to humans,and its contact will cause harm to the body's skin,lungs,central nervous system,digestive system,liver and kidney.In this paper,based on the actual pipe network growth ring,the components were analyzed,and then two kinds of iron minerals in the growth ring were prepared in the laboratory to characterize its micro-structure and surface properties.Then,iron mineral adsorption and the catalytic hydrogen peroxide decomposition were carried out to remove Perchloroethylene,and finally the mechanism of catalytic degradation of PCE.The main componentsof the iron materials prepared by the laboratory were tested as ?-Fe OOH and ?-Fe OOH,respectively,both of these materials were mesoporous materials,which had some ability to adsorb the PCE in water,the addition of hydroxyl iron oxide is related to the initial pH of the solution.The optimum dosage of adsorbent for the adsorption reaction is 3.34g/L,if the difference between the initial p H and the p HPZC of the iron mineral is too large,the adsorption effect of PCE will be greatly changed.In order to ensure the best adsorption effect,the p H of the solution should be close to the zero potential of the adsorbent.The Fenton-like system composed of two kinds of hydroxyl iron oxide and hydrogen peroxide based on the pipeline growth ring has strong oxidizing ability.The removal rate of PCE in the reaction is 83.43% in 8 hours.The influence factors of the catalytic degradation of PCE by Fenton-like system were studied: the percentages of oxidant hydrogen peroxide and the dosage of dosing,the dosage of catalyst and the initial p H of the solution were analyzed experimentally.The experimental results show that pH is the most influential factor in degradation of PCE by Fenton-like system,followed by the dosage of catalyst,and the least influencing factor is the dosage of hydrogen peroxide.The optimum conditions forthe catalytic degradation of PCE by the Fenton-like system is:p H=6,the catalyst concentration is 3.33g/L and the concentration of hydrogen peroxide is 0.77g/L.The reaction of PCE in the iron mineral/H₂O₂ system is in accordance with the secondary reaction kinetics.The detection rate of iron ions in the reaction system is3.67mg/L,which is not enough to catalyze the decomposition of H₂O₂,and the removal rate of PCE is 83.43%,indicating that the growth ring catalyzed the decomposition of H₂O₂ in the reaction system to form hydroxyl radicals instead of ionic iron.Therefore,the mechanism of the PCE degradation of the system follows the surface complication catalyzed by the hydroxyl radical mechanism.