EXAFS studies on adsorption irreversibility of Zn(II) on TiO2: Temperature dependence

CORC > 生态环境研究中心 > 中国科学院生态环境研究中心 > 环境水质学国家重点实验室

	EXAFS studies on adsorption irreversibility of Zn(II) on TiO2: Temperature dependence
	Li, Wei; Pan, Gang; Zhang, Meiyi; Zhao, Dongye; Yang, Yuhuan; Chen, Hao; He, Guangzhi
刊名	JOURNAL OF COLLOID AND INTERFACE SCIENCE
	2008-03-15
卷号	319 期号:2 页码:385-391
关键词	zinc TiO2 temperature dependence EXAFS adsorption-desorption adsorption mode adsorption irreversibility hysteresis
英文摘要	Adsorption irreversibility of Zn(II) on TiO2 at various temperatures was studied using a combination of classical macroscopic methods and extended X-ray absorption fine structure (EXAFS) spectroscopy. When the temperature was increased from 5 to 40 degrees C, the Zn(II) adsorption capacity increased by 130%, and adsorbed Zn(II) became more reversible. The standard Gibbs free energy change (AGO) of the adsorption reaction at 5, 20, and 40 degrees C was determined to be -19.58 +/- 0.30, -22.28 +/- 0.10, and -25.14 +/- 0.21 kJ mol(-1), respectively. And the standard enthalpy (Delta H-0) and entropy (Delta S-0) were 24.55 +/- 2.91 kJ mol(-1) and 159.13 +/- 0.53 J mol(-1) K-1 respectively. EXAFS spectra results showed that the hydrated Zn(II) was adsorbed through fourfold coordination with an average Zn-O bond distance of 1.98 +/- 0.01 angstrom. Two Zn-Ti atomic distances of 3.25 +/- 0.02 and 3.69 +/- 0.03 angstrom were observed, which corresponded to an edge-sharing linkage mode (strong adsorption) and a corner-sharing linkage mode (weak adsorption), respectively. As the temperature increased from 5 to 40 degrees C, the number of strong adsorption sites (N-1) remained relatively constant while the number for the weak adsorption sites (N-2) increased by 31%. These results indicate that the net gain in adsorption capacity and the decreased adsorption irreversibility at elevated temperatures were due to the increase in available weak adsorption sites (N-2) or the decrease in the ratio of N-1/N-2. Both the macroscopic sorption/desorption equilibrium data and the molecular level evidence of this study suggest that in a given environmental system (e.g., soils or natural waters) zinc and other similar heavy metals are likely more mobile at higher temperatures. (C) 2007 Elsevier Inc. All rights reserved.
WOS记录号	WOS:000253259100001
内容类型	期刊论文
源URL	[http://ir.rcees.ac.cn/handle/311016/22244]
专题	生态环境研究中心_环境水质学国家重点实验室
推荐引用方式 GB/T 7714	Li, Wei,Pan, Gang,Zhang, Meiyi,et al. EXAFS studies on adsorption irreversibility of Zn(II) on TiO2: Temperature dependence[J]. JOURNAL OF COLLOID AND INTERFACE SCIENCE,2008,319(2):385-391.
APA	Li, Wei.,Pan, Gang.,Zhang, Meiyi.,Zhao, Dongye.,Yang, Yuhuan.,...&He, Guangzhi.(2008).EXAFS studies on adsorption irreversibility of Zn(II) on TiO2: Temperature dependence.JOURNAL OF COLLOID AND INTERFACE SCIENCE,319(2),385-391.
MLA	Li, Wei,et al."EXAFS studies on adsorption irreversibility of Zn(II) on TiO2: Temperature dependence".JOURNAL OF COLLOID AND INTERFACE SCIENCE 319.2(2008):385-391.