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Advances in Environmental Research
  Volume 5, Number 2, June 2016, pages 141-151
open access

Application of nanofiltration membrane in the recovery of aluminum from alkaline sludge solutions
Wen Po Cheng, Fung Hwa Chi, Ruey Fang Yu and Dun Ren Tian

    Large amounts of aluminum hydroxide (Al(OH)3) exist in water purification sludge (WPS) because of the added aluminum coagulant in water treatment process. Notably, Al(OH)3 is an amphoteric compound, can be dissolved in its basic condition using sodium hydroxide to form aluminate ions (Al(OH)4-). However, in a process in which pH is increasing, the humid acid can be dissolved easily from WPS and will inhibit the recovery and reuse of the dissolved aluminate ions. This study attempts to fix this problem by a novel approach to separate Al(OH)4 - ions using nanofiltration (NF) technology. Sludge impurity in a alkaline solution is retained by the NF membrane, such that the process recovers Al(OH)4 - ions, and significantly decreases the organic matter or heavy metal impurities in the permeate solution. The Al(OH)4- ion is an alkaline substance. Experimental results confirm that a recovered coagulant of Al(OH)4- ion can effectively remove kaolin particles from slightly acidic synthetic raw water.
Key Words
    aluminate; nanofiltration membrane; recovery; coagulant
Wen Po Cheng, Ruey Fang Yu and Dun Ren Tian: Department of Safety, Health and Environmental Engineering, National United University, No.1, Lienda, Miaoli 360, Taiwan, R.O.C

Fung Hwa Chi: Department of Environmental Engineering Kun Shan University, No.195, Kunda Rd., Yongkang Dist., Tainan City 710, Taiwan, R.O.C.

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