Industrial Technology Research Institute

Mao-Sung Lee

Wang-Kuan Chang

Chi-Chung Liao

Ren-Yang Horng

Hsin Shao

Chihpin Huang

Shih-Ming Yen

A method of removing arsenic from water by using a reactor that is provided with a fluidized bed of carriers is disclosed. An arsenic-containing influent is mixed in the reactor with a sulfide aqueous solution or metallic salt aqueous solution at a predetermined pH, thereby resulting in formation of crystals of arsenic sulfides or arsenic acid metal salts. The arsenic contained in the influent is thus removed by crystallization. An effluent with a reduced arsenic content is discharged from the reactor. The carriers, on which the crystals are formed, are periodically removed from the reactor which is replenished with fresh carriers immediately after.

Method of arsenic immobilization in crystalline form from water

The present invention provides a crystallization process for removing fluoride from waste water. Fluoride-containing waste water is introduced into a fluidized bed crystallizer provided with a carrier. A water soluble sodium reagent and a water soluble aluminum reagent are added into the fluidized bed crystallizer to form crystallized cryolite (Na,AlF,) onto the carrier. The treated waste water is separated from the fluidized bed crystallizer to obtain a primary treated water. The formed cryolite is in the form of crystals, which contain about less than 10% water, and is very convenient for re-utilization.

Crystallization process for removing fluoride from waste water

A process for removing fluoride from wastewater is presented. Calcium (or magnesium), sodium and aluminum reagents are added into a fluidized bed crystallizer to remove most of the fluoride in wastewater. The remaining fluoride is removed by aluminum hydroxide. Alternatively, two fluidized bed crystallizers are used in series to treat the fluoride-containing wastewater: in the first fluidized bed crystallizer, calcium (or magnesium), sodium and aluminum reagents are used to treat the wastewater which contains high concentrations of fluoride, so that the fluoride concentrations thereof are largely reduced. Then, in the second fluidized bed crystallizer, a calcium reagent is added to further remove fluoride therein.

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Hsinchu, Taiwan

Mao-Sung Lee