| Mercury currently in particular to water pollution, it is difficult to be biodegradated but is easily absorbed by the bio-accumulating and through the food chain, causing great harm to human health. People developed many physical, chemical or biological methods for mercury-polluted water treatment, such as chemical precipitation, ion exchange, electrolysis, activated carbon adsorption, metal reduction method, microbiological method, and so on. While perfecting these methods at this stage and treatment efficiency increasing, there are still various drawbacks. Therefore, a simple, fast, cost-effective, green, environmentally friendly, and without secondary pollution approach is still desired.This thesis is partially fiancially suppoted by the National Natural Science Foundation of China (No.20835003 and No.20805032) and focused on photo-induced chemical vapor generation. By systematically studying the various factors on the wastewater treatment efficiency for mercury removal, including the UV irradiation time, the concentration of the reaction medium, flow rate, and other important experimental conditions, the optimal solution has been selected. Based on mercury removal, we have established a method of photo trapping and investigate the mercury in the liquid - gas - solid phase transformation mechanism of the migration system.The following main results were obtained:Through investigating the irradiation time, reaction medium concentration, carrier gas flow rate and other factors impact on the treatment efficiency, the optimal experimental procedure has been established. With the formic acid concentration of 10% (v / v), 10 s exposure time, 300 mL/min argon flow rate, the removal efficiency was more than 99 .4%. Compared with traditional mercury water treatment, it is faster, green, and economy. Formic acid was the only agent through the whole process, and the carrier gas used in the experiments could be replaced with much less epensive air. No additional pollution to the environment, since the reactants and by-products are friendly to the environment (CO2 and water).A new method called photo trapping has been established. It is a way of mercury vapor capture through UV light exposure. The whole process without any additional reagent, mercury can be carried out from gas phase into solid phase under UV light exposure and trapped on the surface of the quartz tube. With this method, the collection of the previous emission (mercury vapor) efficiency can reach 98%, thus avoiding secondary pollution. It is more economical, efficient and convenient than other traditional treatment method. It can also be applied to the removal of mercury vapor in the air and suitable for environmental and geochemical samples analysis.By discussing the mechanism of the photo-induced cold vapor generation and photo trapping in the acid medium, we found formic acid produced a strong reduction CO? or H?, both of them can reduct with Hg2 + and produce Hg0. Mercury vapor can be oxided into HgO under UV with the presence of water vapor to achieve the capture of mercury.In the program, carrier gas can be completely replaced by air. Natural light can achieve the effect of UV light, but takes longer time. The water itself contains organic compounds which play the role of formic acid matter. Therefore, we simulated the migration and transformation of mercury in the natural way throughout the study, and this is beneficial to the study of migration and the transformation of mercury in the liquid - gas - solid phase. |
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