| Summary: | 碩士 === 國立中興大學 === 環境工程學系所 === 101 === The aim of this study is to remove alachlor, highly toxic endocrine disruptors, by advanced treatment by coagulation, activated carbon adsorption, and advanced oxidation process (UVC/H2O2 and UVA/TiO2). Therefore, explore the feasibility of advanced treatment applied to alachlor.
This research used aluminum potassium sulfate dodecahydrate as coagulant. The adsorbents were two commercial activated carbons, granular activated carbon (GAC) and powdered activated carbons (PACs). Moreover, in advanced oxidation processes employ ultraviolet-C (UVC) radiation-hydrogen peroxide, and ultraviolet-A (UVA) -titanium dioxide. They strongly rely on oxidative characteristics of free-radical species such as hydroxyl radicals (HO˙) that mediate degradation or decomposition of target compounds. The TiO2 was synthesized by sol-gel method and characterized by field emission scanning electron microscope (FE-SEM), high resolution X-ray diffractometer (HRXRD), and electron spectroscope for chemical analysis (ESCA).
FE-SEM results showed that TiO2 had smaller particle size than commercial TiO2 about 22 nm amd 88 nm, respectively. The crystal structures of TiO2 contains anatase and rutile. Furthermore, the surface of photocatalyst is related to O-Ti-O bonds.
Only 10 % of alachlor decay in coagulation–flocculation performance. The adsorption of alachlor on GAC shows that extended Langmuir model gives a best fit with experimental observations, where the higest percentage of adsorption capacity was 99 %. However it required seven hours. On the other hand, it could be achieved about 98% of adsorption rapidly of both acid and basic solution for PAC after two hours, and equilibrium data fitted well with Freundlich model. Besides, alachlor could be degraded by more than 80% by direct photolysis. But the concentration of alachlor did not conformed to the EPA emission standard. Nevertheless the effectiveness of H2O2 addition for alachlor removal during UVC treatment was increase to 99 %. Although direct photolysis of alachlor in UVA/TiO2 system were inefficient, removal efficiency would reach about 93 % of the adsorption capacity and photocatalytic reaction by the photocatalyst. Two kinds of photocatalytic degradation reactions followed pseudo-first-order kinetic model.
Summary of this study, UVC/H2O2 advanced oxidation process was the best treatment of alachlor.
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