Characterization of floc size and structure under different monomer and polymer coagulants on microfiltration membrane fouling
Characterization of floc size and structure under different monomer and polymer coagulants on microfiltration membrane fouling
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DOI：
10.1016/j.memsci.2008.04.008
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发表时间：
2008-08
影响因子：
9.5
通讯作者：
Jin Wang;J. Guan;S. R. Santiwong;T. Waite
中科院分区：
文献类型：
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作者：
Jin Wang;J. Guan;S. R. Santiwong;T. Waite
无机单体明矾、聚合氯化铝（ACH）和聚合氯化铝（PACl）混凝剂预混凝的团聚体特性对腐殖酸（HAs）的去除和微滤（MF）膜污染的减轻有重要影响。ACH和PACl形成的絮体的分形维数比单体明矾形成的絮体的分形维数高，表明高分子絮凝剂形成的Keggin结构比明矾水解产物的六聚环结构更紧密。相应地，滤饼层比阻远高于明矾，并且当用ACH和PACl预凝结时，MF膜通量劣化严重得多。此外，PAC的碱度越高，滤饼层结垢越严重，产生的密集水解产物Al 13的比例越大。因此，聚合物混凝剂ACH和PACl似乎不适合预混凝-MF工艺，因为滤饼层阻力增加了2至3倍，尽管它们与用于去除HAs的明矾相比节省了60-70%的剂量。此外，根据Carman-Kozeny关系，对于扫凝条件下的三种铝基混凝剂，剂量不足会导致HA去除率较低，并产生更多的小颗粒，导致饼层比阻较高。另一方面，混凝剂水解物种作为直接污染物负荷加重滤饼阻力的MF膜时，过量。预混凝-微滤组合工艺的最佳投加量应保持在最小值，以提供更好的HAs去除效果，并产生更低的滤饼层比阻和更高的膜过滤性能。
The characteristic of aggregates pre-coagulated by inorganic monomer alum, polymer aluminium chlorohydrate(ACH) and polyaluminium chloride(PACl) coagulants impose major impact on the removal of humic acids (HAs) and the reduction of microfiltration (MF) membrane fouling. The fractal dimension of flocs formed by ACH and PACl is higher than that by monomer alum, indicating Keggin structure produced by polymer coagulants is much more compact compared with hexameric ring structure of alum hydrolysis species. Correspondingly, cake layer specific resistance is far higher and the MF membrane flux deteriorates much more severely when pre-coagulated by ACH and PACl than by alum. Moreover, the higher basicity contains in PACls, the cake layer fouling is more serious for producing more proportion of dense hydrolysis species Al13. Thus, the polymer coagulant ACH and PACl seems not adapt to the pre-coagulation–MF process for cake layer resistance increase two to three times although they save 60–70% dose in comparison with alum for HAs removal. Additionally, for three Al-based coagulants under sweep coagulation condition, insufficient dose result in lower HAs removal and produce more small particles caused higher cake layer specific resistance according to Carman–Kozeny relationship. On the other hand, coagulant hydrolysis species as direct contaminant loading aggravated cake resistance on the MF membrane when overdosed. The optimum dose should keep the minimum to provide better HAs removal efficiency, and produce lower cake layer specific resistance and higher membrane filterability for pre-coagulation–MF hybrid process.