氯化镁复配硫酸铝混凝性能及絮体特性

在研究氢氧化镁混凝特性的基础上,复配氯化镁和硫酸铝作为混凝剂,以高岭土配水水样为研究对象,运用iPDA在线监测技术对混凝过程絮体形成进行监测,探讨了单独使用氯化镁和硫酸铝以及二者复配使用的混凝效果和絮体特性,确定复配使用的各种条件。结果表明,对于浊度20 NTU,pH 11.5的高岭土配水水样,氯化镁、硫酸铝最佳投加量分别为7.2 mg/L(Mg2+计)和3 mg/L(Al3+计);硫酸铝跟氯化镁复配使用时,先投加硫酸铝,间隔30 s后投加氯化镁,混凝效果较好;在镁离子最佳投加量7.2 mg/L时,铝和镁最佳质量比在1∶3~1∶2之间;镁铝复配时其FI值明显大于单独作用时,即絮体尺寸大小:二者复配硫酸铝氯化镁,而且复配条件下Zeta电位值在零电势左右浮动,浮动范围小,更利于聚集沉淀;镁铝复配时发生了协同效应,弥补了单独使用氯化镁混凝过程的不足。

Coagulation performance and floc properties of magnesium chloride combining with aluminium sulfate

On the basis of magnesium hydroxide coagulation performance, magnesium chloride combining with aluminium sulfate as coagulants were used to investigate the coagulation process of kaolin water sample by on-line intelligent particle dispersion analyzer (iPDA). The coagulation performance and floc properties were investigated using single and combined coagulants and the operational conditions were also determined. The results showed that the optimum dosages for magnesium ion and aluminium ion at 20 NTU and pH 11.5 were 7.2 and 3 mg/L, respectively. Using magnesium chloride together with aluminium sulfate as combining coagulants,coagulation performance and floc properties were better when magnesium chloride addition was preceeded by aluminium sulfate addtion at an interval of 30 s. The optimum quality ratio range was 1:3~1:2 for aluminium vs magnesium when the optimum dosage for magnesium ion was 7.2 mg/L. FI value for combing addition was greater than single condition, the change of Zeta potential was close to zero favoring better coagulation and sedimentation and the change range was not obvious.The synergistic effect which occurred at combining magnesium chloride with aluminium sulfate could make up for the deficiency of magnesium chloride solely.