铝盐混凝剂的混凝效果与残留铝含量和组分之间的关系研究

研究了氯化铝、硫酸铝、聚合氯化铝(poly-aluminum chloride, PAC)3种铝盐混凝剂在腐殖酸-高岭土模拟水样中的应用,以比较3种混凝剂在该水样中的混凝效果与残留铝含量和组分之间的关系.结果表明, 3种铝盐混凝剂在试验选取的投加量下对浊度和UV254的去除率最高可达90%左右,PAC能在较高的投加量下达到较好的混凝效果;较高投加量下PAC混凝沉淀出水中残留总铝含量为0.9 mg/L左右,余铝率为-3.0%左右,均明显低于传统的铝盐混凝剂;3种混凝剂混凝处理腐殖酸-高岭土模拟水样时,残留铝均大部分以溶解性总铝的形式存在,且溶解性有机铝在总溶解性铝中所占比例较大;PAC在腐殖酸-高岭土混凝沉淀出水中残留总铝的含量下降最快,且能够有效降低出水中毒性较大的溶解性铝的含量,其混凝沉淀出水中残留总溶解性铝含量为0.6 mg/L左右.

Relationship Among Coagulation Effect of Al-based Coagulant, Content and Speciation of Residual Aluminum

The application of AlCl₃, Al₂ (SO₄)₃ and poly-aluminum chloride (PAC) in humic acid-kaolin simulated water was studied in this article. It is intended to discuss the relationship among coagulation effect of Al-based coagulants in humic acid-kaolin simulated water and content and speciation of residual aluminum. It was found that, the turbidity removal efficiency and UV₂₅₄ removal efficiency could reach about 90% at the tested dosage. At higher dosage, PAC gave better coagulation effect. The residual total aluminum content and residual aluminum ratio of PAC, which was 0.9 mg/L and -3.0% or so respectively, were greatly lower than those of AlCl₃ and Al₂(SO₄)₃. The residual total dissolved aluminum was the predominant content in the effluent after coagulation and sedimentation by the three Al-based coagulants. For the total dissolved aluminum, the proportion of dissolved organic aluminum was significantly higher than that of other aluminum speciation. With respect to humic acid-kaolin simulated water, the content of residual total aluminum in the effluent after coagulation and sedimentation by PAC decreased obviously compared to AlCl₃ and Al₂ (SO₄)₃. PAC could effectively decrease the content of residual dissolved aluminum speciation which has higher toxicity. The content of residual total dissolved aluminum in the effluent after coagulation and sedimentation by PAC was about 0.6 mg/L.