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Adsorption behaviors and mechanisms of methyl orange on heat-treated palygorskite clays / Hao Chen in Industrial & engineering chemistry research, Vol. 51 N° 43 (Octobre 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 43 (Octobre 2012) . - pp. 14026–14036 Titre : Adsorption behaviors and mechanisms of methyl orange on heat-treated palygorskite clays Type de document : texte imprimé Auteurs : Hao Chen, Auteur ; Aiguo Zhong, Auteur ; Junyong Wu, Auteur Année de publication : 2013 Article en page(s) : pp. 14026–14036 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Clay  mineral Résumé : Understanding completely the interaction of clay mineral and anionic dye is very important for the applications of clay minerals. In this paper, the adsorption behaviors of heat-treated palygorskite clays for methyl orange (MO) from an aqueous medium were studied using equilibrium batch and theoretic calculation techniques. The crystal structure and surface appearance of the heat-treated samples were studied using Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). The adsorption results reveal that a higher calcining temperature helps in improving removal performance of palygorskite clay for methyl orange. The isothermal adsorption experiments show that there is almost no adsorption at low dye concentrations but a sudden linear increase occurs when the dye concentration exceeds to a certain value. A lower change point is observed for 700 °C treated sample compared with that of the natural sample. The leaching of exchangeable Mg2+ ions located in palygorskite should be a key factor affecting the adsorption capacity. Both the experimental and theoretical studies suggest that the adsorption of MO onto heat-treated palygorskite clay is controlled by the two mechanisms: for samples treated at lower temperatures (<300 °C), the hydrogen bonding between oxygen groups of −SO3– (anionic head groups of MO) and H+ of both the bound zeolitic water and coordinated water should be important. While for samples calcined at higher temperature (>400 °C), electrostatic interaction between the dye–Mg2+ complexes and negatively charged surface of heat-treated palygorskite clay becomes dominant. In addition, the latter becomes stronger with the increasing the calcination temperature, which can be ascribed to the formation of a higher ratio of complexes and stronger negatively charged surface of the adsorbent caused by leaching of more metal ions. This work provides a deep insight into the interaction of heat-treated palygorskite clay and anionic dye, which paves the way for their practical applications in anionic dye adsorption. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie300702j [article] Adsorption behaviors and mechanisms of methyl orange on heat-treated palygorskite clays [texte imprimé] / Hao Chen, Auteur ; Aiguo Zhong, Auteur ; Junyong Wu, Auteur . - 2013 . - pp. 14026–14036. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 43 (Octobre 2012) . - pp. 14026–14036 Mots-clés : Clay  mineral Résumé : Understanding completely the interaction of clay mineral and anionic dye is very important for the applications of clay minerals. In this paper, the adsorption behaviors of heat-treated palygorskite clays for methyl orange (MO) from an aqueous medium were studied using equilibrium batch and theoretic calculation techniques. The crystal structure and surface appearance of the heat-treated samples were studied using Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). The adsorption results reveal that a higher calcining temperature helps in improving removal performance of palygorskite clay for methyl orange. The isothermal adsorption experiments show that there is almost no adsorption at low dye concentrations but a sudden linear increase occurs when the dye concentration exceeds to a certain value. A lower change point is observed for 700 °C treated sample compared with that of the natural sample. The leaching of exchangeable Mg2+ ions located in palygorskite should be a key factor affecting the adsorption capacity. Both the experimental and theoretical studies suggest that the adsorption of MO onto heat-treated palygorskite clay is controlled by the two mechanisms: for samples treated at lower temperatures (<300 °C), the hydrogen bonding between oxygen groups of −SO3– (anionic head groups of MO) and H+ of both the bound zeolitic water and coordinated water should be important. While for samples calcined at higher temperature (>400 °C), electrostatic interaction between the dye–Mg2+ complexes and negatively charged surface of heat-treated palygorskite clay becomes dominant. In addition, the latter becomes stronger with the increasing the calcination temperature, which can be ascribed to the formation of a higher ratio of complexes and stronger negatively charged surface of the adsorbent caused by leaching of more metal ions. This work provides a deep insight into the interaction of heat-treated palygorskite clay and anionic dye, which paves the way for their practical applications in anionic dye adsorption. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie300702j

Removal capacity and adsorption mechanism of heat-treated palygorskite clay for methylene blue / Hao Chen in Chemical engineering journal, Vol. 174 N° 1 (Octobre 2011) 

Public ISBD [article]  in Chemical engineering journal > Vol. 174 N° 1 (Octobre 2011) . - pp.143–150 Titre : Removal capacity and adsorption mechanism of heat-treated palygorskite clay for methylene blue Type de document : texte imprimé Auteurs : Hao Chen, Auteur ; Jie Zhao, Auteur ; Aiguo Zhong, Auteur Année de publication : 2012 Article en page(s) : pp.143–150 Note générale : Génie chimique Langues : Anglais (eng) Mots-clés : Adsorption  Heat-treated  palygorskite  Methylene  blue  Dissolved  ions  Mechanism Résumé : In this work, palygorskite clay was activated by heat treatment method and its capacity for the removal of a typical cationic dye, methylene blue, was studied. The activated samples were characterized by XRD and BET techniques. The physical quantities including the cation exchange capacity (CEC) of the activated samples, the variation of pH during the adsorption process and the concentration of metal ions in the supernatant were also measured. The results show that the adsorption capacity of the heat-treated sample increases with temperature and reaches the maximum at 700 °C, and then decreases with further increasing temperature. In general, with the increasing calcined temperature, the variation trend of the adsorption capacity of activated samples for dye is accordant with that of CEC. The results of the metal ions leached from the adsorbent demonstrate the leaching amount of divalent ions (Mg2+, Ca2+) in all samples are significantly higher than that of univalent (Na+, K+) and trivalent ions (Fe3+, Al3+). In addition, the changing tendency of leaching amount of divalent ions with the increasing temperature is consistent with that of adsorption capacity of the heat-treated samples whether the dye solution is acidic, neutral or alkaline. The leaching of divalent ions should be the main factor affecting the adsorption capacity of heat-activated palygorskite for methylene blue. ISSN : 1385-8947 En ligne : http://www.sciencedirect.com/science/article/pii/S1385894711010205 [article] Removal capacity and adsorption mechanism of heat-treated palygorskite clay for methylene blue [texte imprimé] / Hao Chen, Auteur ; Jie Zhao, Auteur ; Aiguo Zhong, Auteur . - 2012 . - pp.143–150. Génie chimique Langues : Anglais (eng) in Chemical engineering journal > Vol. 174 N° 1 (Octobre 2011) . - pp.143–150 Mots-clés : Adsorption  Heat-treated  palygorskite  Methylene  blue  Dissolved  ions  Mechanism Résumé : In this work, palygorskite clay was activated by heat treatment method and its capacity for the removal of a typical cationic dye, methylene blue, was studied. The activated samples were characterized by XRD and BET techniques. The physical quantities including the cation exchange capacity (CEC) of the activated samples, the variation of pH during the adsorption process and the concentration of metal ions in the supernatant were also measured. The results show that the adsorption capacity of the heat-treated sample increases with temperature and reaches the maximum at 700 °C, and then decreases with further increasing temperature. In general, with the increasing calcined temperature, the variation trend of the adsorption capacity of activated samples for dye is accordant with that of CEC. The results of the metal ions leached from the adsorbent demonstrate the leaching amount of divalent ions (Mg2+, Ca2+) in all samples are significantly higher than that of univalent (Na+, K+) and trivalent ions (Fe3+, Al3+). In addition, the changing tendency of leaching amount of divalent ions with the increasing temperature is consistent with that of adsorption capacity of the heat-treated samples whether the dye solution is acidic, neutral or alkaline. The leaching of divalent ions should be the main factor affecting the adsorption capacity of heat-activated palygorskite for methylene blue. ISSN : 1385-8947 En ligne : http://www.sciencedirect.com/science/article/pii/S1385894711010205