標題: The origin of Al(OH)(3)-rich and Al-13-aggregate flocs composition in PACl coagulation
作者: Lin, Jr-Lin
Huang, Chihpin
Chin, Ching-Ju M.
Pan, Jill R.
環境工程研究所
生物科技學系
Institute of Environmental Engineering
Department of Biological Science and Technology
關鍵字: PACl;Coagulation;Al-13;Aluminum hydroxide;Composition;XPS
公開日期: 1-Sep-2009
摘要: The composition of hydrolyzed Al species is essential for the understanding of coagulation with Al-based coagulants. Surface characteristics of flocs formed by coagulation with two distinct polyaluminum chloride (PACl) coagulants were identified. One commercial coagulant (PACl-C) with voluminous monomeric Al and colloidal Al(OH)(3) and a custom-made PACl (PACl-Al-13) containing high Al-13 content were applied to destabilize kaolin particles. The flocs formed by PACl-C and PACl-Al-13 at neutral and alkaline pH ranges, respectively, were observed by FE-SEM and HR-TEM. In addition, the Al composition of these flocs was characterized by XPS and HR-XRD, and the imaging of Al(OH)(3) precipitates and Al-13 aggregates were conducted by SEM as well as tapping mode AFM in liquid system. The observations of flocs indicate that the morphology of Al(OH)(3)-rich flocs are fluffy and porous around the edge of flocs, while the Al-13-aggregate flocs have a glossy contour and irregular structure. Both Al(OH)(3)-rich and Al-13-aggregate flocs do not possess well-formed crystalline structure except for the Al-13-like crystal exists in the Al-13-aggregate flocs. Among Al(OH)(3) precipitates, colloidal Al(OH)(3) is micro-scale in size, while amorphous Al(OH)(3) is nano-scale. During the formation of Al-13 aggregates, some coiled and clustered Al-13 aggregates with smoother surface were observed. The XPS study on floc surface showed that tetrahedral (Al-IV)/octahedral (Al-VI) Al ratio on the surfaces of PACl-C and PACl-Al-13 flocs is 1:1.6 and 1:9.9, respectively. Of the in situ formed Al-13, almost half of Al-hydroxide precipitates on the surface of Al(OH)(3)-rich flocs possess the Al-IV center. It also found that the irregularly aggregated Al-13 with a similar Al-13 Crystalline structure subsists on the surface of Al-13-aggregate flocs. (C) 2009 Elsevier Ltd. All rights reserved.
URI: http://dx.doi.org/10.1016/j.watres.2009.06.023
http://hdl.handle.net/11536/149841
ISSN: 0043-1354
DOI: 10.1016/j.watres.2009.06.023
期刊: WATER RESEARCH
Volume: 43
起始頁: 4285
結束頁: 4295
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