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Effect of pore size on the growth of hydroxyapatite from mesoporous CaO-SiO2 substrate / Yan Deng in Industrial & engineering chemistry research, Vol. 48 N° 19 (Octobre 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 19 (Octobre 2009) . - pp. 8829–8836 Titre : Effect of pore size on the growth of hydroxyapatite from mesoporous CaO-SiO2 substrate Type de document : texte imprimé Auteurs : Yan Deng, Auteur ; Xiaoke Li, Auteur ; Qiang Li, Auteur Année de publication : 2009 Article en page(s) : pp. 8829–8836 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Mineral  hydroxypapatite  CaO−SiO2  bioactive  material Résumé : In this work, a new approach for controlling the formation rate of hard tissue mineral hydroxypapatite (HAP) through the control of inner pore sizes of CaO−SiO2 bioactive material is proposed. Highly ordered mesoporous CaO−SiO2 (MCS) bioactive material with different pore sizes were synthesized through two types of surfactants, cetyltrimethyl-ammonium bromide (CTAB) and triblock copolymer EO106PO70EO106 (Pluronic F127). These two surfactants were selected for their different pore size formation tendencies, about 2.7 nm for CTAB template and 4.9 nm for F127 template. These two types of MCS materials have identical chemical composition but differ only in their pore sizes. Their bioactivities were evaluated by the incubation of the MCS in phosphate buffer solution at 37 °C for different periods of time. SEM showed that incubated MCS with 2.7-nm pore size could rapidly form a dense layer of HAP crystallites on its surfaces within a few hours, while incubated MCS with 4.9-nm pore size just formed a sparse layer of HAP after one week of incubation, with XRD to further confirm the HAP phase. This unique phenomenon was explained from theoretical calculations in which the critical nucleation diameter, 2r* of the HAP on the MCS substrate is above 2.7 nm but below 4.9 nm. HRTEM observation proved that HAP nuclei indeed formed inside the pores of the F127 templated MCS sample with 4.9-nm pore size, which could block inner pore channels and obstruct the transportation of dissolved Ca ion to the outer surface, and then hindered the subsequent surface HAP formation. However, no HAP nuclei were found in the pores of the CTAB-templated MCS sample with 2.7-nm pore size, due to the thermodynamic instability of HAP nuclei below their critical size, r*, for which the unblocked pore channels facilitate the quick transportation of Ca ions and result in a much higher surface HAP growth rate. This finding provides a new material design strategy to accelerate the HAP formation rate simply by tuning its inner pore sizes below 2r* of HAP, without the need for modification of the material’s chemical composition. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801796y [article] Effect of pore size on the growth of hydroxyapatite from mesoporous CaO-SiO2 substrate [texte imprimé] / Yan Deng, Auteur ; Xiaoke Li, Auteur ; Qiang Li, Auteur . - 2009 . - pp. 8829–8836. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 19 (Octobre 2009) . - pp. 8829–8836 Mots-clés : Mineral  hydroxypapatite  CaO−SiO2  bioactive  material Résumé : In this work, a new approach for controlling the formation rate of hard tissue mineral hydroxypapatite (HAP) through the control of inner pore sizes of CaO−SiO2 bioactive material is proposed. Highly ordered mesoporous CaO−SiO2 (MCS) bioactive material with different pore sizes were synthesized through two types of surfactants, cetyltrimethyl-ammonium bromide (CTAB) and triblock copolymer EO106PO70EO106 (Pluronic F127). These two surfactants were selected for their different pore size formation tendencies, about 2.7 nm for CTAB template and 4.9 nm for F127 template. These two types of MCS materials have identical chemical composition but differ only in their pore sizes. Their bioactivities were evaluated by the incubation of the MCS in phosphate buffer solution at 37 °C for different periods of time. SEM showed that incubated MCS with 2.7-nm pore size could rapidly form a dense layer of HAP crystallites on its surfaces within a few hours, while incubated MCS with 4.9-nm pore size just formed a sparse layer of HAP after one week of incubation, with XRD to further confirm the HAP phase. This unique phenomenon was explained from theoretical calculations in which the critical nucleation diameter, 2r* of the HAP on the MCS substrate is above 2.7 nm but below 4.9 nm. HRTEM observation proved that HAP nuclei indeed formed inside the pores of the F127 templated MCS sample with 4.9-nm pore size, which could block inner pore channels and obstruct the transportation of dissolved Ca ion to the outer surface, and then hindered the subsequent surface HAP formation. However, no HAP nuclei were found in the pores of the CTAB-templated MCS sample with 2.7-nm pore size, due to the thermodynamic instability of HAP nuclei below their critical size, r*, for which the unblocked pore channels facilitate the quick transportation of Ca ions and result in a much higher surface HAP growth rate. This finding provides a new material design strategy to accelerate the HAP formation rate simply by tuning its inner pore sizes below 2r* of HAP, without the need for modification of the material’s chemical composition. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801796y

Separation of succinic acid from fermentation broth using weak alkaline anion exchange adsorbents / Qiang Li in Industrial & engineering chemistry research, Vol. 48 N° 7 (Avril 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 7 (Avril 2009) . - pp. 3595–3599 Titre : Separation of succinic acid from fermentation broth using weak alkaline anion exchange adsorbents Type de document : texte imprimé Auteurs : Qiang Li, Auteur ; Jianmin Xing, Auteur ; Wangliang Li, Auteur Année de publication : 2009 Article en page(s) : pp. 3595–3599 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Succinic  acid  Separation  Adsorption  Weak  alkaline  anion  exchange  adsorbe  Langmuir/Freundlich  isotherm  models  Pseudo-first/second-order  equations Résumé : Succinic acid is one of the platform chemicals that can be bioproduced from renewable resources. Separation of succinic acid by adsorption from model solutions and fermentation broth by weak alkaline anion exchange adsorbents was studied. Adsorption capacities and regenerability of several sorts of adsorbents were tested. In a static test, the adsorbent NERCB 09 has the adsorption capacity of 0.11 g succinic acid g−1 at succinic acid concentrations of 5 g L−1. In packed column test, its capacity was as high as 0.56 g succinic acid g−1 when the feeding concentration was 50 g L−1. NERCB 09 showed the high selectivity toward succinate over both glucose and amino acid at acidic or neutral conditions. Langmuir/Freundlich isotherm models and pseudo-first/second-order equations were presented to simulate the adsorption behavior. Data showed that the temperature had little effect on the adsorption isotherm. Kinetic parameters suggested that about 1.5 h were sufficient for the adsorption equilibrium. The adsorbent was easily regenerated. The adsorption capacity was steady after 30 cycles and showed 96% average recovery. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801304k [article] Separation of succinic acid from fermentation broth using weak alkaline anion exchange adsorbents [texte imprimé] / Qiang Li, Auteur ; Jianmin Xing, Auteur ; Wangliang Li, Auteur . - 2009 . - pp. 3595–3599. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 7 (Avril 2009) . - pp. 3595–3599 Mots-clés : Succinic  acid  Separation  Adsorption  Weak  alkaline  anion  exchange  adsorbe  Langmuir/Freundlich  isotherm  models  Pseudo-first/second-order  equations Résumé : Succinic acid is one of the platform chemicals that can be bioproduced from renewable resources. Separation of succinic acid by adsorption from model solutions and fermentation broth by weak alkaline anion exchange adsorbents was studied. Adsorption capacities and regenerability of several sorts of adsorbents were tested. In a static test, the adsorbent NERCB 09 has the adsorption capacity of 0.11 g succinic acid g−1 at succinic acid concentrations of 5 g L−1. In packed column test, its capacity was as high as 0.56 g succinic acid g−1 when the feeding concentration was 50 g L−1. NERCB 09 showed the high selectivity toward succinate over both glucose and amino acid at acidic or neutral conditions. Langmuir/Freundlich isotherm models and pseudo-first/second-order equations were presented to simulate the adsorption behavior. Data showed that the temperature had little effect on the adsorption isotherm. Kinetic parameters suggested that about 1.5 h were sufficient for the adsorption equilibrium. The adsorbent was easily regenerated. The adsorption capacity was steady after 30 cycles and showed 96% average recovery. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801304k