Influences of polysilicic acid in Al₁₃ species on floc properties and membrane fouling in coagulation/ultrafiltration hybrid process

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• 作者：Weiying Xu ; Baoyu Gao ; ^{baoyugao_sdu@yahoo.com.cn} ; Yan Wang ; Qin Zhang ; Qinyan Yue
• 关键词：Al13 ; Polysilicic acid ; Coagulation&ndash ; ultrafiltration ; Floc characteristics ; Membrane fouling
• 刊名：Chemical Engineering Journal
• 出版年：2012
• 出版时间：1 March 2012
• 年：2012
• 卷：181-182
• 期：Complete
• 页码：407-415
• 全文大小：854 K

文摘

Effect of polysilicic acid (pSi) on pre-formed Al₁₃ polycation ([Al₁₃O₄(OH)₂₄(H₂O)₁₂]⁷⁺) was investigated regarding the coagulation efficiency, floc properties and subsequent impact on membrane fouling in coagulation-ultrafiltration (C-UF) hybrid process. Also, the effect of pSi on the commonly used coagulant, polyaluminum chloride (PACl) was studied for comparison. Characteristics of aggregates pre-coagulated by different coagulants were investigated using a laser diffraction particle sizing device. And membrane fouling was investigated using a dead-end batch ultrafiltration unit. The results of this study indicated that the introduction of pSi into pre-hydrolyzed Al coagulants could obviously increase the coagulation efficiency, especially when the Si/Al ratio was 0.05. Al₁₃ produced stronger flocs than PACl, while pSi enhanced the floc strength factors for both Al₁₃ and PACl. However, Al₁₃-Si and PACl-Si led to smaller recovery factors (R_f) of aggregates than Al₁₃ and PACl. Additionally, the flocs formed by Al₁₃ presented compacter degree (D_f = 2.34) than those formed by PACl (D_f = 2.22); while both Al₁₃-Si and PACl-Si gave rise to much loosely constructed flocs with similar D_f values of 2.15 and 2.12, respectively. The results of ultrafiltration experiments implied that Al₁₃ produced less membrane fouling than PACl. Incorporation of pSi into Al coagulants could significantly alleviate the cake layer and adsorption resistance and thus the membrane fouling. The effects of Al₁₃-Si and PACl-Si on flux declines and filtration resistances were similar.