聚硅酸对不同形态铝沉积行为的影响

针对给水管网中残余铝沉积和再溶解现象可能引起的水质问题,研究了聚硅酸对不同水解聚合形态铝沉积、再溶解的影响,并以石英微晶天平为表征手段,初步探讨了聚硅酸对不同形态铝沉积、再溶解过程影响的机理.结果表明,聚硅酸能显著改变不同水解聚合形态铝的沉积、再溶解行为.聚硅酸可与3种水解聚合形态的铝迅速结合而生成可沉积产物,但产物性质不同.以单体形态为主的Al_0与聚硅酸的反应产物性质较稳定,部分以溶解态存在,部分以非溶解态(可沉积态)存在;尽管铝的两种聚合形态Al_(13)和Al_(30)与聚硅酸反应也生成了部分可沉积产物,但随着时间的推移,这些产物又逐渐向溶解态转化.铝硅比对Al_0体系中铝的沉积溶解行为影响较小,而对Al_(13)和Al_(30)影响较大,且在0.2∶20(以Al和SiO_2计的质量比)时,沉积态铝的溶解速率最快.

Effect of Polysilicic Acid on the Deposition Behavior of Different Aluminum Species

To understand the water quality problems caused by deposition and re-dissolution behaviors of residual aluminum in drinking water distribution system (DWDS), the effect of polysilicic acid on the deposition and re-dissolution behaviors of different aluminum species was investigated by using jar tests and quartz crystal microbalance, which could demonstrate the deposition behavior of different aluminum species and the physic-chemical properties of deposited layers. The results showed that the effect of polysilicic acid on the deposition behavior of different aluminum species was significant. Al₀ (mainly monomeric species), Al₁₃ and Al₃₀ (polymeric species) could react rapidly with polysilicic acid, and some insoluble products formed. However, the stability of insoluble products from different aluminum species was distinct. The insoluble product formed by reaction of Al₀ with polysilicic was relatively stable. With regard to the systems of polysilicic acid with Al₁₃ and Al₃₀, the dissolved aluminum concentration increased with reaction time, which indicated that the deposited product could be gradually transformed to soluble monomeric or oligomeric aluminum species. Compared with the influence of Al/Si ratio on Al₀, the ratio of aluminum to silicon significantly affected the deposition and re-dissolution behavior of Al₁₃ and Al₃₀, and the re-dissolution rate of insoluble aluminum was the most rapid when the ratio of aluminum with silica was 0.2:20 (as mass ratio of Al to SiO₂).