PAC-PDMDAAC复合絮凝剂净化海水的絮凝特性及其絮凝条件优化

Flocculation of Composite Flocculant PAC-PDMDAAC for Seawater Purification and Its Optimum Coagulation Condition

以聚合氯化铝(PAC)和聚二甲基二烯丙基氯化铵(PDMDAAC)为原料制备了PAC-PDMDAAC复合絮凝剂,将其用于海水的净化处理。考察了PDMDAAC与Al的不同质量比对絮凝指数FI、形成絮体厚度及体系稳定动力学参数的影响,确定了PAC-PDMDAAC复合絮凝剂的PDMDAAC/Al最适宜配比。采用Box-Behnken响应面法分析了絮凝剂投加量、反应pH值之间的交互作用及其对浊度和COD_(Mn)去除效果的影响。实验结果表明:与聚合氯化铝(PAC)相比,PAC-PDMDAAC复合絮凝剂净化海水过程中形成絮体更大,沉降性能更好;随着PDMDAAC与Al质量比的增大,絮凝指数FI曲线上升越快速,絮体分层厚度越大,沉降速度越快,稳定动力学参数越大。PAC-PDMDAAC复合絮凝剂的最适宜混凝条件为:反应体系pH值为7.5,絮凝剂投加量为15.3mg/L,在该条件下复合絮凝剂对海水COD_(Mn)和浊度的去除率均值分别为65.2%和87.4%,实验结果与响应曲面模型预测值基本相符。

The composite flocculants were prepared using PAC（Polymeric aluminum chloride） and PDMDAAC（Poly dimethyl diallyl ammonium chloride） as raw materials,and was used in purification treatment of seawater.The coagulation process during the treatment of coastal seawater was evaluated by investigating flocculation index（FI）,floc thickness and stability kinetics under different PDMDAAC/Al mass ratios.The Box-Behnken response surface methodology was used to study the combined effects of flocculant dosage and pH on turbidity and COD_（Mn） removal efficiency.The experimental results demonstrated that the composite flocculant had better flocculant efficiency than PAC.The increase in the PDMDAAC/Al mass ratio resulted in a larger flocculation index,flocs thickness and stability kinetics parameter,and the floc sedimentation rate was also increased.The optimal coagulation conditions for the treatment of seawater using PAC-PDMDAAC were as follows：pH 7.5,flocculant dosage 15.3 mg/L.Moreover,the maximum removal rate of COD_（Mn） and turbidity under optimal conditions reached up to 65.2%and 87.4% respectively,which were consistent with the predicted value by response surface methodology.