Browsing by Author "Wang, Dongsheng"

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Coagulation behavior of Al-13 aggregates
(2008-10-01)
Lin, Jr-Lin
;
Chin, Ching-Ju M.
;
Huang, Chihpin
;
Pan, Jill R.
;
Wang, Dongsheng
The coagulation behavior of Al-13 aggregates formed in coagulation of kaolin was investigated by small angle static light scattering (SASLS), solid-state Al-27 NMR and tapping mode atomic force microscope (TM-AFM). A kaolin suspension was coagulated by PACl containing high content of Al-13 polycation (PACl-Al-13). The results indicated that Al-13 was predominant in destabilizing kaolin particles for PACl-Al-13 coagulation even though at alkaline pH (pH 10). At such high pH, Al-13 aggregates were observed when the dosage of PACl-Al-13 was increased. In addition, the mechanism of coagulation by PACl-Al-13 at alkaline pH was affected by dosage. When the dosage was insufficient, coagulation was caused by electrostatic patch, which led to compact flocs with high fractal dimension (D-f) Interparticle bridging dominated the coagulation when the coagulant dosage approached the plateau of adsorption, which caused the looser flocs with low Df. The in-situ AFM scanning in liquid system proved that the existence of linear A113 aggregates composed of a chain of coiled Al-13 in coagulation by PACl-Al-13 at a high dosage and alkaline pH. Meanwhile, several coiled Al-13 aggregates with various dimensions were observed at such condition. Crown Copyright (C) 2008 Published by Elsevier Ltd. All rights reserved.
Effect of Al(III) speciation on coagulation of highly turbid water
(2008-05-01)
Lin, Jr-Lin
;
Huang, Chihpin
;
Pan, Jill Ruhsing
;
Wang, Dongsheng
;
環境工程研究所
In Taiwan, the turbidity of raw water for fresh water treatments can sometimes reach as high as 40000 NTU due to intensive rainfall, especially in typhoon seasons. In response, water works often apply large quantities of coagulants such as polyaluminium chloride (PACl). In this study, simulated and natural highly turbid water was coagulated with two PACls, a commercial product (PACl-1) and a laboratory product (PACl-E). The Al species distributions of PACl-1 and PACl-E under various pH conditions were determined, and the corresponding coagulation efficiency was evaluated. The PACl-E has a wider range of operational pH, while the efficiency of PACl-1 peaks at around neutral pH. For simulated water up to 5000 NTU, the PACl-E was superior to PACl-1 at low dosage and in the pH range studied. Similar results were discovered with natural water, except that when the turbidity was extremely high, the coagulation efficiency of PACl-E decreased significantly due to the presence of large amounts of organic matter. The coagulation of PACl-E was closely related to the content of polycationic aluminium (Al-13) while that of PACl-1 was dictated by the amount of Al, The sludge from PACl-E coagulation had better dewaterability when the optimum dosage was applied. The experimental results suggest that for natural water up to 5000 NTU, PACl containing high Al-13 species is recommended for coagulation. In cases when the water contains high organic matter, efficient coagulation depends upon enmeshment by amorphous aluminium hydroxide. (C) 2008 Elsevier Ltd. All rights reserved.
Hydrolyzed Al(III) clusters: Speciation stability of nano-Al(13)
(2011-01-01)
Wang, Dongsheng
;
Wang, Shuifeng
;
Huang, Chihpin
;
Chow, Christopher W. K.
;
環境工程研究所
Pure nano-Al(13) and aggregates at various concentrations were prepared to examine the particle size effect of coagulation with inorganic polymer flocculant. The property and stability of various species formed were characterized using Infrared, (27)Al-NMR, photo correlation spectroscopy (PCS), and Ferron assay. Results showed that concentration and temperature exhibited different roles on the stability of Al(13). The quantity of Al(b) species analyzed by ferron assay in the initial aging period corresponded well with that of Alp, which has been confirmed in a dimension range of 1-2 nm by PCS. Al(13) solutions at high concentrations (0.5-2.11 mol/L) were observed to undergo further aggregation with aging. The aggregates with a wide particle size distribution would contribute to the disappeared/decreased Al(13) basis on the (27)Al-NMR spectrum, whereas a part of Al(13) would still remain as Al(b). At low concentrations, Al(13) solution was quite stable at normal temperature, but lost its stability quickly when heating to 90 degrees C.
Hydrolyzed Al(III) clusters: Speciation stability of nano-Al-13
(2011-01-01)
Wang, Dongsheng
;
Wang, Shuifeng
;
Huang, Chihpin
;
Chow, Christopher W. K.
;
環境工程研究所
Pure nano-Al-13 and aggregates at various concentrations were prepared to examine the particle size effect of coagulation with inorganic polymer flocculant. The property and stability of various species formed were characterized using Infrared, Al-27-NMR, photo correlation spectroscopy (PCS), and Ferron assay. Results showed that concentration and temperature exhibited different roles on the stability of Al-13. The quantity of Al-b species analyzed by ferron assay in the initial aging period corresponded well with that of Alp, which has been confirmed in a dimension range of 1-2 nm by PCS. Al-13 solutions at high concentrations (0.5-2.11 mol/L) were observed to undergo further aggregation with aging. The aggregates with a wide particle size distribution would contribute to the disappeared/decreased Al-13 basis on the Al-27-NMR spectrum, whereas a part of Al-13 would still remain as Al-b. At low concentrations, Al-13 solution was quite stable at normal temperature, but lost its stability quickly when heating to 90 degrees C.