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Detrimental thixotropic thinning of filter cake of SiO2 – Al2O3 composite coated TiO2 particles and Its control / Bing-Xin Wei in Industrial & engineering chemistry research, Vol. 50 N° 24 (Décembre 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 24 (Décembre 2011) . - pp. 13799–13804 Titre : Detrimental thixotropic thinning of filter cake of SiO2 – Al2O3 composite coated TiO2 particles and Its control Type de document : texte imprimé Auteurs : Bing-Xin Wei, Auteur ; Lin Zhao, Auteur ; Ting-Jie Wang, Auteur Année de publication : 2012 Article en page(s) : pp. 13799–13804 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Thixotropic Résumé : A SiO2–Al2O3 double layer coating process is widely used for TiO2 particle to reduce its photocatalytic activity. The conventional coating process needs a long time and uses large amounts of acid and alkali solutions. We recently developed a new SiO2–Al2O3 composite coating process that needs less time and does not use acid and alkali solutions. This process produced coated TiO2 particles with excellent weather durability, but it had the problem that the filter cakes composed of these particles were thixotropically thin and were easily broken up by shear or disturbance on a conveyor belt; that is, the cakes thinned into slurries very quickly. A slurry is not a suitable physical form for the subsequent drying process in industrial production. To understand this problem better, the rheology of the filter cakes was measured. Experiments to investigate the mechanism of the thixotropic thinning behavior indicated that the Si–O–H groups on the surface of the coated particles formed, by hydrogen bonding, a network structure of the particles that entrapped water within the structure. This structure was easily destroyed by an applied shear or disturbance, leading to the release of the occluded water, and the presence of water caused the cake to become a slurry and its viscosity to decrease sharply. This thixotropic thinning behavior of the filter cake was eliminated by coating the particle surface with a thin film of aluminum oxide. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie201233u [article] Detrimental thixotropic thinning of filter cake of SiO2 – Al2O3 composite coated TiO2 particles and Its control [texte imprimé] / Bing-Xin Wei, Auteur ; Lin Zhao, Auteur ; Ting-Jie Wang, Auteur . - 2012 . - pp. 13799–13804. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 24 (Décembre 2011) . - pp. 13799–13804 Mots-clés : Thixotropic Résumé : A SiO2–Al2O3 double layer coating process is widely used for TiO2 particle to reduce its photocatalytic activity. The conventional coating process needs a long time and uses large amounts of acid and alkali solutions. We recently developed a new SiO2–Al2O3 composite coating process that needs less time and does not use acid and alkali solutions. This process produced coated TiO2 particles with excellent weather durability, but it had the problem that the filter cakes composed of these particles were thixotropically thin and were easily broken up by shear or disturbance on a conveyor belt; that is, the cakes thinned into slurries very quickly. A slurry is not a suitable physical form for the subsequent drying process in industrial production. To understand this problem better, the rheology of the filter cakes was measured. Experiments to investigate the mechanism of the thixotropic thinning behavior indicated that the Si–O–H groups on the surface of the coated particles formed, by hydrogen bonding, a network structure of the particles that entrapped water within the structure. This structure was easily destroyed by an applied shear or disturbance, leading to the release of the occluded water, and the presence of water caused the cake to become a slurry and its viscosity to decrease sharply. This thixotropic thinning behavior of the filter cake was eliminated by coating the particle surface with a thin film of aluminum oxide. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie201233u

Spray coating of adsorbent with polymer latex on sand particles for fluoride removal in drinking water / Hai-Xia Wu in Industrial & engineering chemistry research, Vol. 47 n°14 (Juillet 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 n°14 (Juillet 2008) . - p. 4697-4702 Titre : Spray coating of adsorbent with polymer latex on sand particles for fluoride removal in drinking water Type de document : texte imprimé Auteurs : Hai-Xia Wu, Auteur ; Ting-Jie Wang, Auteur ; Xiao Min Dou, Auteur ; Bei Zhao, Auteur Année de publication : 2008 Article en page(s) : p. 4697-4702 Note générale : Bibliogr. p. 4702 Langues : Anglais (eng) Mots-clés : Fe-Al-Ce  adsorbent;  Polymer  latex;  Spray  coating Résumé : An iron-aluminum-cerium trimetal hydroxide (Fe-Al-Ce) adsorbent with an acrylic-styrene copolymer latex binder, which can cross-link and cure at room temperature, was coated on sand particles by spray coating. The adhesion of the coated layer increased with the latex/Fe-Al-Ce ratio. A suitable latex/Fe-Al-Ce ratio and thickness of coated adsorbent were determined to be 0.8 and 70 μm, respectively, giving good stability and adsorption capacity. The corresponding adsorption capacity of fluoride ions on the coated sand reached 3.46 mg/g at pH 7.0 and an initial fluoride concentration of 50 mg/L. Sand coated with Fe−Al−Ce is a potential adsorbent for use in a packed bed for fluoride removal from drinking water. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800278b [article] Spray coating of adsorbent with polymer latex on sand particles for fluoride removal in drinking water [texte imprimé] / Hai-Xia Wu, Auteur ; Ting-Jie Wang, Auteur ; Xiao Min Dou, Auteur ; Bei Zhao, Auteur . - 2008 . - p. 4697-4702. Bibliogr. p. 4702 Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 n°14 (Juillet 2008) . - p. 4697-4702 Mots-clés : Fe-Al-Ce  adsorbent;  Polymer  latex;  Spray  coating Résumé : An iron-aluminum-cerium trimetal hydroxide (Fe-Al-Ce) adsorbent with an acrylic-styrene copolymer latex binder, which can cross-link and cure at room temperature, was coated on sand particles by spray coating. The adhesion of the coated layer increased with the latex/Fe-Al-Ce ratio. A suitable latex/Fe-Al-Ce ratio and thickness of coated adsorbent were determined to be 0.8 and 70 μm, respectively, giving good stability and adsorption capacity. The corresponding adsorption capacity of fluoride ions on the coated sand reached 3.46 mg/g at pH 7.0 and an initial fluoride concentration of 50 mg/L. Sand coated with Fe−Al−Ce is a potential adsorbent for use in a packed bed for fluoride removal from drinking water. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800278b

The roles of the surface charge and hydroxyl group on a Fe−Al−Ce adsorbent in fluoride adsorption / Hai-Xia Wu in Industrial & engineering chemistry research, Vol. 48 N° 9 (Mai 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 9 (Mai 2009) . - pp. 4530–4534 Titre : The roles of the surface charge and hydroxyl group on a Fe−Al−Ce adsorbent in fluoride adsorption Type de document : texte imprimé Auteurs : Hai-Xia Wu, Auteur ; Ting-Jie Wang, Auteur ; Lin Chen, Auteur Année de publication : 2009 Article en page(s) : pp. 4530–4534 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Surface  charge  Hydroxyl  group  Fe−Al−Ce  adsorbent  Fluoride  adsorption  External  voltage Résumé : The roles of the surface charge and hydroxyl group on a Fe−Al−Ce adsorbent in fluoride adsorption were studied. Fluoride adsorption at different initial solution pH was investigated. An external voltage was applied to an adsorbent-coated electrode to examine the adsorption characteristics due to the surface charge. The capability of accepting or providing H+ of the hydroxyl on the adsorbent surface was determined through the titration of NaOH solution, and the change of the hydroxyl before and after adsorption was analyzed by FTIR. Fluoride adsorption was rapid during the initial stage but slowed down later. Fluoride ions were transferred to the adsorbent surface by Coulombic attraction and/or thermal motion, forming a temporary and nonspecific adsorption. The enriched fluoride ions reacted with the hydroxyl groups on the adsorbent surface, forming a stable adsorption. The surface charge on the adsorbent and ion exchange between surface hydroxyl groups and fluoride ions have a large effect on the adsorption rate and efficiency. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800890q [article] The roles of the surface charge and hydroxyl group on a Fe−Al−Ce adsorbent in fluoride adsorption [texte imprimé] / Hai-Xia Wu, Auteur ; Ting-Jie Wang, Auteur ; Lin Chen, Auteur . - 2009 . - pp. 4530–4534. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 9 (Mai 2009) . - pp. 4530–4534 Mots-clés : Surface  charge  Hydroxyl  group  Fe−Al−Ce  adsorbent  Fluoride  adsorption  External  voltage Résumé : The roles of the surface charge and hydroxyl group on a Fe−Al−Ce adsorbent in fluoride adsorption were studied. Fluoride adsorption at different initial solution pH was investigated. An external voltage was applied to an adsorbent-coated electrode to examine the adsorption characteristics due to the surface charge. The capability of accepting or providing H+ of the hydroxyl on the adsorbent surface was determined through the titration of NaOH solution, and the change of the hydroxyl before and after adsorption was analyzed by FTIR. Fluoride adsorption was rapid during the initial stage but slowed down later. Fluoride ions were transferred to the adsorbent surface by Coulombic attraction and/or thermal motion, forming a temporary and nonspecific adsorption. The enriched fluoride ions reacted with the hydroxyl groups on the adsorbent surface, forming a stable adsorption. The surface charge on the adsorbent and ion exchange between surface hydroxyl groups and fluoride ions have a large effect on the adsorption rate and efficiency. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie800890q