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Research on Removal of Arsenic from Raw Water by Zero-valent Iron

Author: ZhangWei
Tutor: ShiYongSheng
School: Kunming University of Science and Technology
Course: Municipal Engineering
Keywords: Zero-valent iron Trivalent arsenic Sync oxidative adsorption Permeable reactive barrier Water body restoration
CLC: TU991.2
Type: Master's thesis
Year: 2010
Downloads: 157
Quote: 0
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Abstract


The world's more than 100 million people drinking water arsenic exceeding about more than 20 countries, especially in concentration can lead to acute and chronic human poisoning arsenic were found in the source of drinking water in Bangladesh, China, and Mongolia. Arsenic pollution comes mainly from anthropogenic and geochemical factors, the \In the water environment, arsenic trivalent (As (III)) and pentavalent (As (Ⅴ)) two kinds of valence state exists, but many studies have confirmed the toxicity, solubility, mobility of As (Ⅲ) much larger than As (Ⅴ), As (Ⅲ) usually exists in molecular form, so a variety of process water As (Ⅲ) removal efficiency of As (V) are much lower than the water As (Ⅲ) removal a hot research scholars. As (Ⅲ) removal method, zero-valent iron (Fe (0)) has a readily available, inexpensive and non-toxic harmless, its synchronization oxidative adsorption of As (Ⅲ) attention by researchers. This study is the effect of factors in addition to arsenic adsorption mechanism of As (III) the adsorption performance as well as the impact of Fe (0) Fe (0). The results show that Fe (0) to the effective removal of As (Ⅲ), Fe (0) and As (Ⅲ) mass ratio of 1000:1, the initial concentration of As (III) of 100μg / L, pH5. 0:00 240min contact time, the removal rate of As (III) of more than 90%. Fe (0) on the adsorption of As (Ⅲ) in line with the Langmuir isotherm model, the equilibrium adsorption capacity for 1.9790mg / g. Fe (0) oxidation of As (III) the adsorption reaction course, the first order reaction kinetic equation. Fe (0) formed in water, corrosion and oxidation of iron (hydr) oxides by surface Fe-OH functional groups and As (Ⅲ) and As (Ⅴ) surface complexation reaction occurs to form a double-ligand complexes, the solution arsenic in play the inner ligand complex adsorption. The study also showed that Fe (0) the effect of the removal of As (Ⅲ) by the significant influence of pH and dissolved oxygen concentration of the water samples, weakly acidic conditions (pH5 ~ 7) and high dissolved oxygen is conducive to the removal of As (Ⅲ). Ions in the water on the Fe (0) to remove the effect of As (Ⅲ) also have an impact, high concentrations of H2PO4-existence of competitive adsorption of arsenate (sub) iron (hydr) oxide surface, the H2PO4-on Fe (0 inhibition) removal of As (Ⅲ); iron arsenate in NO3-(sub) (hydrogen) oxide surface there is no competitive adsorption, and high concentration of NO3 can promote corrosion of Fe (0) NO3- removal of As (Ⅲ) Fe (0) promoted; Ca2, Mg2 promote the removal of As (Ⅲ) Fe (0), and the the Ca2 role more significant. This topic Fe (0) and quartz sand composed of the reaction wall under low pressure conditions on the subject of As (III) contamination of the original water carried repair of Fe (0) reaction layer thickness for 600mm quartz sand filter layer thickness to 600mm effluent As (III) concentration were below 50μg / L, reached the surface water environment quality standard (GB3838-2002) I - III class waters total arsenic concentration standard requirements, while meeting the irrigation water quality standards \water quality requirements), and high water for vegetable irrigation water total arsenic concentration standard requirements, effluent total iron concentration lower than 0.3mg / L, total iron concentrations below drinking water health standards \limit, has a practical application for the wall of the reaction, in low-power conditions, water restoration, simulation experiments using a gravity filter, without the pressure-driven, focus on considering the congestion of the quartz sand layer to determine quartz sand layer of the cleaning cycle, the application of the method to fix the arsenic pollution engineering practice to provide reference. The reaction wall construction investment is small, low running costs, the treatment effect is good, simple maintenance and management, therefore, arsenic contamination of raw water, the reaction wall repair is effective and feasible.

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CLC: > Industrial Technology > Building Science > Municipal Engineering > Water supply project ( on the Water Works ) > Clean Water ( water treatment )
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