萃取法回收水厂污泥中铝的技术研究 Ⅱ.浆液萃取法

Alum Recovery from Waterworks Sludge by Solvent Extraction Using Bi-(2-ethylhexyl)phosphate Ⅱ.Slurry Extraction

以水厂污泥为原料,二-(2-乙基己基)磷酸为萃取剂,煤油为稀释剂,研究了浆液萃取铝回收技术。结果表明:含固率为5%的浆液直接采用P204-煤油萃取,在pH=5.0、cP204=0.5 mol/L、相比(VO∶VA)为1∶1的条件下,铝萃取率可达96.9%以上,萃取剂回收率达到98%以上。以5 mol/L硫酸作为反萃剂,相比5∶1的条件下经3级反萃,可回收97.6%的铝,且反萃液符合液态商品硫酸铝的质量标准,可作为混凝剂利用。

Al present in a water treatment plant sludge （SiO2 54.6%, Al2O3 10.3%, organic matters 12.5%） may be recovered and recycled as liquid alum for coagulation treatment. A slurry （5% SS by weight） was first prepared by mixing the sludge in a bi-（2-ethylhexyl）-phosphate Cp204 and kerosene extractant mixture. Under the optimal conditions of pH=5.0, Cp204 =0.5 mol/L, and phase ratio Vo ： VA= 1 ： 1, 96. 9% of Al was extracted, by ion exchange of H^＋ for Al^3＋ , from the sludge. Al in the extraction liquor was then stripped by H2SO4 solution （5 mol/L） in 3-stage stripping at a phase ratio of 5 ：1 ; 97.6% of Al was moved to the clear aqueous phase which was reusable in the waterworks. 98% of the P204/kerosene extractant was recovered by centrifugation of the emulsified phase at 7 000 r/min for 10 min.