复合混凝剂中PDM对PAC铝形态分布影响

选用3种盐基度的聚合氯化铝(PAC)分别与聚二甲基二烯丙基氯化铵(PDM)制成系列复合混凝剂PAC/PDM,研究了PDM特征黏度、PAC与PDM质量配比对复合混凝剂中盐基度、铝形态分布的影响及其与混凝性能的关联.分别采用酸碱滴定法、Al-Ferron逐时络合比色法和混凝烧杯试验对复合混凝剂的盐基度、铝形态分布和混凝性能进行了考察.结果表明,在试验范围内,随着PDM特征黏度由0.87dL/g增加至3.79dL/g,或PAC/PDM质量配比由20∶1减小至5∶1,未观察到复合混凝剂的盐基度和铝形态分布有明显变化;而混凝试验结果表明,针对所选模拟原水,当余浊下降至6NTU时,复合混凝剂PAC/PDM(2.88/10∶1)能使PAC投加量减少19.2%—19.5%;随PDM特征黏度由0.87增加至3.79dL/g,絮团尺寸和沉降速率增加;随PAC/PDM质量配比由20∶1减少到5∶1,PAC投加量减少15.9%—19.9%,因此PDM能明显提高PAC的混凝性能,且随着复合混凝剂中PDM特征黏度增加,或者PAC/PDM质量比例降低,混凝效果都得以增强.由此可见,复合混凝剂中PDM对PAC盐基度和铝形态分布的影响与其优越的强化混凝性能未有直接的关联性.

Effect of PDM in Composite Coagulants on the Aluminum Species Distribution in PAC

A series of composite coagulants were prepared from polyaluminum chloride(PAC)with three kinds of basicity and polydimethyldiallylammonium chloride(PDM),the influences of intrinsic viscosity of PDM and the mass ratios of PAC to PDM on the basicity and the aluminum species distribution in composite coagulants were studied.Meanwhile,the correlation between these influences and the coagulation performance of composite coagulants was also investigated in detail.Acid-alkali titration,Al-Ferron complexation timed spectrophotometry and jar test were used respectively to measure basicity,aluminum species distribution and coagulation performance.The results showed that the basicity and the aluminum species distribution in composite coagulants didn’t change observably with the intrinsic viscosity of PDM increasing from 0.87dL/g to 3.79dL/g or the ratios of PAC to PDM decreasing from 20∶1 to 5∶1.However,the jar test results indicated that for the simulative water,when residual turbidity of 6NTU was required,the composite coagulants PAC/PDM(2.88/10∶1)could decrease the PAC dose by 19.2%—19.5%;with the intrinsic viscosity of PDM increasing from 0.87dL/g to 3.79dL/g,the floc size and settlement rate increased,with the ratios of PAC to PDM decreasing from 20∶1 to 5∶1,the PAC dosage was decreased by 15.9%—19.9%.So PDM improved the coagulation effect of PAC remarkably,and the coagulation effect were enhanced either with the intrinsic viscosity of PDM increasing or the ratios of PAC to PDM decreasing.Therefore,there is no direct correlation between the influences of PDM on basicity or aluminum species distribution in PAC and the high enhanced coagulation efficiency of composite coagulants.