Study On Degradation Performance Of Organic Pollutant In Aqueous Solution By Urea Hydrogen Peroxide Oxidation

Urea hydrogen peroxide?UHP?is a kind of solid oxidants with properties of both hydrogen peroxide and urea,and it has great stability.After dissolving into water,it can release reactive oxygen slowly and controllably and react for a long time.Its reactive oxygen content is high and equal to 36.17%of hydrogen peroxide,which makes it have the functions of oxidation,disinfection,sterilization and bleaching.Due to no residual toxicity after use,it becomes a new type of green and great oxidant and has been widely used in many aspects of life.Fenton and Fenton-like reactions are applied extensively in sewage treatment because they can produce a large number of highly oxidative free radicals,HO·,which has no selectivity to pollutants.Therefore,UHP is used as a solid substitute for hydrogen peroxide in the research of this dissertation,and three kinds of catalytic systems are conducted to activate UHP to remove organic contaminants.The specific research contents are as follows:?1?Different kinds of metal ions were used to activate UHP and then degrade the contaminant of azo dye AO7.The effect factors of catalyst concentration,oxidant concentration,pollutant concentration and reaction environment pH value on AO7 removal were explored.And then the ability of H₂O₂ decomposition by these metal ions were also evaluated.Moreover,the promotive effect of other metal ions on the decomposition of H₂O₂by Fe???was preliminarily explored,which will provide research basis for the following study.The results indicated that Fe???is the most effective metal ion on H₂O₂ decomposition,while the effect of Cu???is mild and Mn???and Co???almost have no effect.In the metal ions of Fe???/UHP strengthening experiment,the presence of Cu???presence makes obvious promoting effect,and the next chapter Cu???/Fe???/UHP bimetallic system was applied for further experimental study on wastewater treatment,in order to explore its degradation effect and mechanism.?2?Cu???was selected to strengthen Fe???/UHP system to catalyze the degradation of azo dye AO7.The factors of oxidant concentration,pollutant concentration,Cu???/Fe???ratio and reaction environment pH value on AO7 removal were all investigated.Furthermore,the degradation mechanism was explored and the treatment was evaluated.The results indicated that the addition of Cu?II?can strengthen the efficiency at a certain extent under various oxidant concentrations.And even a small amount of Cu???will promote the removal of pollutant,which can avoid the toxicity and negative effects of metal ions in the environment.The addition of Cu???can improve the stability of soluble iron ions and the availability of H₂O₂.Free radical scavenging tests indicated the important function of HO·and O₂·^-in the contaminant degradation.Bimetallic system provides a good idea for the treatment of refractory organic wastewater and industrial wastewater.?3?Chelated-Fe???was used as catalyst to activate UHP,and then OA/Fe???/UHP system was applied to the degradation of bisphenol A?BPA?.The effect factors of oxidant concentration,pollutant concentration,OA/Fe???ratio,reaction environment pH value and solution matrix on BPA removal were explored.Moreover,the degradation dynamics and mechanism were also studied.The results illustrated that the addition of OA has obvious enhancement on the efficiency of BPA degradation in Fe???/UHP system.It can be explained that the existence of OA can reduce the pH value of reaction solution,simultaneously the chelation of Fe???and ligand improves the stability of soluble iron ions,slows down the iron precipitation formation and expands the pH range of reaction,which is advantageous to the treatment of natural water.Moreover,the slow-releasing potential of UHP improves its availability in the oxidation system.The presence of CO₃^2-,HCO₃^-and HA inhibited the degradation rate significantly.BPA degradation process is two-stage reaction,and the second stage after 15 min followed pseudo-first-order kinetic model.In addition,both HO·and O₂·^-were identified that they played an important role in the oxidative degradation of BPA.OA/Fe???/UHP system provides a practical and effective method for handling refractory pollutants in natural water,and with the advantage of environmentally friendly,this method has vast potential for future development.