Combination of Co-Precipitation with Zeolite Filtration to Remove Arsenic from Contaminated Water

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7/1/2008 - 6/30/2010

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  • Zhaohui Li, UW-Parkside

Arsenic contamination of natural waters becomes a serious issue worldwide. Thus, arsenic removal from contaminated water attracts great attention recently. Most technologies involve in oxidation, co-precipitation and adsorption of arsenic onto coagulated flocs. Several sorptive media, including activated alumina, iron sand, hydrated ferric oxide, and activated bauxite, have been tested. The goal of this research is to combine co-precipitation with zeolite filtration to effectively remove arsenic from water. Coprecipitation involves in simultaneous addition of AlCl3, FeCl3 or NaOH to form Al(OH)3 or Fe(OH)3 precipitates on which arsenic has strong adsorption, while filtration separates arsenic-containing iron/aluminum hydroxide precipitates from water. Thus, the essence to remove arsenic from water is to separate iron/aluminum hydroxide precipitates from water via filtration. Although sand is commonly used as the filtration media, its affinity for Al(OH)3 or Fe(OH)3 precipitates is limited due to its low charge density and smaller surface area. Zeolite has larger surface area and higher charge density and is an ideal sorbent and filtration medium. In this research we will test the optimal mass/mass ratio of arsenic to flocculent to achieve an anticipated reduction in aqueous arsenic concentration. Then, we will test the mass/mass ratio of flocculent to filtration media to achieve an anticipated reduction in colloidal iron/aluminum hydroxide concentration. We will also determine the throughput volumes and evaluate the overall efficiency in terms of cost reduction and volume reduction of solid waste when zeolite is used compared to sand. It is expected that the overall efficiency of arsenic removal will be higher and the amount of waste generated per fixed volume of water will be much less when zeolite is used. Moreover, zeolite can remove other undesired metal cations. It is anticipated that benefit of using zeolite instead of sand as the filtration media will be well justified.

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