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3069800 
Journal Article 
Potassium alum crystal derived from aluminum salt in water treatment sludge by nanofiltration 
Chi, FHwa; Cheng, WenPo; Tian, DunRen; Yu, RF; Fu, ChiHua 
2015 
Yes 
Journal of Material Cycles and Waste Management
ISSN: 1438-4957
EISSN: 1611-8227 
17 
3 
522-528 
WOS:000358149400013 
The major method used for the recovery of aluminum from water purification sludge is through acidification or alkalization, however, the cost of the acid and alkali limits the amount available for use, and thus results in the low concentration of dissolved aluminum salt; moreover, the metal ions and organic matter dissolved simultaneously in the process will also increase the difficulty in reuse. Therefore, this study used sulfuric acid to dissolve aluminum in the sludge from the water treatment plant, followed by the low price nanofiltration membranes to increase the concentration of aluminum ions, and then adding potassium sulfate to produce the potassium alum crystal, which has less impurity. The influences of the molar ratio of potassium to aluminum and the temperature on the recovery of crystals are investigated. The result showed that there was good crystal recovery when the molar ratio of potassium to aluminum is above 1.6, but the recovery rate decreased as the temperature increased. 
Aluminum recovery; Water purification sludge; Nanofiltration; Potassium alum crystal