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Published on: October 15, 2015
Effect of pH on phosphorus (P) dissolution and recovery from polyaluminum chlorides (PAC) sludge
Umair Ali Toor1, Dong-Jin Kim1
1Department of Environmental Sciences and Biotechnology, Hallym University, Chuncheon, Gangwon 24252, South Korea.
Abstract:
Phosphorus (P) dissolution from polyaluminum chlorides (PAC) sludge was investigated for sustainable P recovery. P dissolution followed 1st order kinetics with the rate constants of 3.8 × 10-2, 0.8 × 10-2, 1.3 × 10-2 and 1.9 × 10-2 min-1 at pH 1, 2.5, 10.5 and 12, respectively. Strong acidic and alkaline conditions dissolved about 82 (pH 1) and 88% (pH 12) of the total P by adding 0.214 g HCl and 0.357 g NaOH per gram P dissolved, respectively. Chemical P fractionation showed that more than 96% of the total P of the PAC sludge was AlP and it was reduced to 11.3 (pH 12) and 12.6% (pH 1.0) after the acid and alkali treatment. ATR-FTIR showed that AlPO4 in the PAC sludge was transformed to Mg3(PO4)2∙4H2O and CaHPO4∙2H2O after alkali treatment and H3PO4 and Na/MgP after acid treatment. Dissolved P can be recovered by precipitation with Ca and Mg.
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