Adsorption Behaviors and Mechanisms of Methyl Orange on Heat-Treated Palygorskite Clays

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• 作者：Hao Chen ; Aiguo Zhong ; Junyong Wu ; Jie Zhao ; Hua Yan
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2012
• 出版时间：October 31, 2012
• 年：2012
• 卷：51
• 期：43
• 页码：14026-14036
• 全文大小：595K
• 年卷期：v.51,no.43(October 31, 2012)
• ISSN：1520-5045

文摘

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 掳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 掳C), the hydrogen bonding between oxygen groups of 鈭扴O₃^{鈥?/sup> (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 掳C), electrostatic interaction between the dye鈥揗g2+ 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.}