Study On Detection Of Perchlorate In Water And Removal Of It By Using Photocatalytic Reduction

Perchlorate is widely used in military industry, fireworks industry, leatherworking and so on. It interferes with the uptake of iodine into the thyroid and mayaffect human health. It is one of the persistent inorganic pollutants and has some feature such as high solubility, low absorbability and high stability. China is not only a great power in aviation and spaceflight military affairs field but also a main producing country of fireworks, so there may be the problem of perchlorate pollution and the concerning research should be carried out. An analytical method about the determination of trace perchlorate in groundwater was built. The perchlorate distribution in Harbin and a method about removing perchlorate from water were studied. All these researches have great realistic significance to the potential environmental risks and development of relevant contingency planning emergency measures.The analytical method of the determination of trace perchlorate in groundwater is studied. At first, the optimumdetecting conditions were found by studying the influences of suppressor current, eluent concentration, eluent velocity and column temperature on detecting perchlorate by using ion chromatography (IC). Then, the optimumgathering conditions of PWAX were found. PWAX is one kind of solid phase extraction (SPE) column. At last, the course of perchlorate gathering and detecting perchlorate by using IC were combined, namely determination of trace perchlorate in water by SPE-IC. The results indicate that when the perchlorate concentration in water ranges from1μg/L to15μg/L, and thechloridionconcentration and sulfate concentration are both smaller than30mg/L, the limit of detection is0.60μg/L and the recovery ranges from99.7%to100.5%.Seasonal variation and influencing factors of perchlorate distribution in groundwater, surface water, rain, snow and surface soilwere studiedin differentperiods in Harbin and its vicinity, China. Results indicate that perchlorate only can be detected in snow during the spring festival and the perchlorate concentration ranged from0.02μg/L to0.15μg/L. In addition, the mean concentration can reach the maximum (0.13μg/L).Perchlorate concentrations in groundwater and surface water decrease after rainy season in summer.Groundwater samples collected in the floodplain areas of the Songhua River and the Ashi River containedhigher perchlorate concentrations than that far away with the rivers.Cu–TiO2/SiO2catalystswere prepared by the sol–gel dip-coating method. The catalyst has the best catalyticactivity when the nominal mass ratio of Cu2+to TiO2is0.5%(Cu0.5).The influences of oxygen, catalyst concentration, hole scavengerconcentration, e, pH, hydroxyl radical, reaction temperature and common ions on photocatalytic perchlorate reduction were studied. Results indicate that the efficiency of perchlorate reductioncan reach95%after260min irradiation (368±0.5K) when the initial perchlorate concentration and citric acidconcentration are0.001mmol/L and0.15mmol/L, citric acid (1.5mmol/L) is added to the system at a constant speed2mL/min. The reaction of perchlorate reduction matches first-order dynamical reaction equation when the initial perchlorate concentrations are different.Cl is identified as the end product and ClO3is the intermediate in the course of perchlorate reduction. Perchlorate is reduced by e and CO2, CO2is the intermediate when citric acid is oxidated by photogenerated hole.