Characteristics of equilibrium, kinetics studies for adsorption of Hg(II), Cu(II), and Ni(II) ions by thiourea-modified magnetic chitosan microspheres

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• 作者：Limin Zhou ; Yiping Wang ; Zhirong Liu ; Qunwu Huang
• 关键词：Chitosan magnetic microspheres ; Heavy metals ; Adsorption ; Thiourea
• 刊名：Journal of Hazardous Materials
• 出版年：2009
• 出版时间：30 January 2009
• 年：2009
• 卷：161
• 期：2-3
• 页码：995-1002
• 全文大小：618 K

文摘

Magnetic chitosan microspheres were prepared and chemically modified with thiourea (TMCS) for adsorption of metal ions. TMCS obtained were investigated by means of X-ray diffraction (XRD), IR, magnetic properties and thermogravimetric analysis (TGA). The adsorption properties of TMCS toward Hg²⁺, Cu²⁺, and Ni²⁺ ions were evaluated. Various factors affecting the uptake behavior such as contact time, temperature, pH and initial concentration of the metal ions were investigated. The kinetics was evaluated utilizing the pseudo-first-order, pseudo-second-order, and the intra-particle diffusion models. The equilibrium data were analyzed using the Langmuir, Freundlich, and Tempkin isotherm models. The adsorption kinetics followed the mechanism of the pseudo-second-order equation for all systems studied, evidencing chemical sorption as the rate-limiting step of adsorption mechanism and not involving a mass transfer in solution. The best interpretation for the equilibrium data was given by Langmuir isotherm, and the maximum adsorption capacities were 625.2, 66.7, and 15.3 mg/g for Hg²⁺, Cu²⁺, and Ni²⁺ ions, respectively. TMCS displayed higher adsorption capacity for Hg²⁺ in all pH ranges studied. The adsorption capacity of the metal ions decreased with increasing temperature. The metal ion-loaded TMCS with were regenerated with an efficiency of greater than 88 % using 0.01–0.1 M ethylendiamine tetraacetic acid (EDTA).