Browsing by Author "Chin, Ching-Ju M."

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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.
Coagulation dynamics of fractal flocs induced by enmeshment and electrostatic patch mechanisms
(2008-11-01)
Lin, Jr-Lin
;
Huang, Chihpin
;
Chin, Ching-Ju M.
;
Pan, Jill R.
;
環境工程研究所
The size and structure of flocs during floc formation were monitored for various coagulation mechanisms. Two distinctive mechanisms, namely, enmeshment and electrostatic patch, govern the dynamics of kaolin particles coagulation by polyaluminurn. chloride (PACl). They were investigated by small angle static light scattering (SASLS) and solid-state Al-27 NMR. In addition, a novel wet SEM (WSEM) was used in-situ to image the morphology of the aggregate in aqueous solution. Synthetic suspended particles were coagulated by two PACl products, a commercial product (PACl) and one laboratory product (PACl-E). The PACl-E contained more than 60% Al-13 while the PACI contained only 7% Al-13, with large percentage of colloidal Al. For coagulation by PACI at neutral pH and high dosage where the strong repulsion between particles occurs, the enmeshment ruled by reaction-limited aggregation (RLA) results in larger sweep flocs as well as higher fractal dimensional structure. For coagulation by PACl-E at alkaline pH and low dosage, the flocs were coagulated predominately by electrostatic patch with Al-13 aggregates. At such condition, it is likely that diffusion-limited aggregation (DLA) predominately rule PACl-E coagulation. The fractal dimension (D-s) values of PACl and PACl-E flocs formed at enmeshment and electrostatic patch increased with dosage, respectively. When breakage of flocs occurs, the breakage rate of PACI-E flocs is slower than that of sweep flocs. By WSEM imaging, the adsorption of spherical Al precipitates onto the particles was observed to form sweep flocs with a rough and ragged contour, while the PACI-E flocs were formed with a smooth and glossy structure. (C) 2008 Elsevier Ltd. All rights reserved.
The origin of Al(OH)(3)-rich and Al(13)-aggregate flocs composition in PACl coagulation
(2009-09-01)
Lin, Jr-Lin
;
Huang, Chihpin
;
Chin, Ching-Ju M.
;
Pan, Jill R.
;
環境工程研究所
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.
The origin of Al(OH)(3)-rich and Al-13-aggregate flocs composition in PACl coagulation
(2009-09-01)
Lin, Jr-Lin
;
Huang, Chihpin
;
Chin, Ching-Ju M.
;
Pan, Jill R.
;
環境工程研究所
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.