作者机构：
[Zhang Yangli; Wu Xiaofu; Zhou Hailan; Zhao Fang; Chen Mingli; Zhao Chong] Cent S Univ Forestry & Technol, Coll Resource & Environm, Changsha 410004, Hunan, Peoples R China.;[Wu Xiaofu] Cent S Univ Forestry & Technol, Coll Resource & Environm, Shaoshan S Rd, Changsha 410004, Hunan, Peoples R China.
通讯机构：
[Wu Xiaofu] C;Cent S Univ Forestry & Technol, Coll Resource & Environm, Shaoshan S Rd, Changsha 410004, Hunan, Peoples R China.
摘要：
Experiments were conducted to investigate the influence of different factors on the adsorption of Zn2+ and Cd2+ ions from aqueous solution onto vermiculite. The ratio of the initial concentration of ions, C-0, to the adsorbent concentration, W-0, was shown to be the key factor determining the equilibrium ion adsorption density, q(e). Subject to the magnitude of C-0/W-0, the value of q(e) could either attain its maximum level, q(m) (the maximum adsorption density), when the solid surface was fully saturated, or approach its critical limit, q(c) (the C-0/W-0 ratio), when the ions in the bulk solution had been completely removed. The main mechanism for adsorption in the systems studied was ion-exchange. An increase in Zn2+ or Cd2+ ion adsorption from the single metal ion solution resulted in an increase in the concentrations of unadsorbed K+, Na+, Ca2+ and Mg2+ ions remaining in the bulk solution. Competition between adsorbing ions was observed in the mixed K+-Zn2+-Cd2+ ion system. Although temperature had a positive effect upon the adsorption of Zn2+ and Cd2+ ions, its effect was statistically negligible over the range 15-45 degrees C. The negative effect of decreasing pH values on the adsorption process was only significant below a pH value of 4.0, indicating that the adsorption of Zn2+ and Cd2+ ions would be significantly depressed when high amounts of H+ ions are present in the system.
摘要：
Experiments on Zn2+ and Cd2+ adsorptions on vermiculite in aqueous solutions were conducted to investigate the widely observed adsorbent concentration effect on the traditionally defined adsorption isotherm in the adsorbate range 25–500 mg/L and adsorbent range 10–150 g/L. The results showed that the equilibrium ion adsorption density did not correspond to a unique equilibrium ion concentration in liquid phase. Three adsorbate/adsorbent ratios, the equilibrium adsorption density, the ratio of equilibrium adsorbate concentration in liquid phase to adsorbent concentration, and the ratio of initial adsorbate concentration to adsorbent concentration, were found to be related with unique values in the tested range. Based on the assumption that the equilibrium state of a liquid/solid adsorption system is determined by four mutually related components: adsorbate in liquid phase, adsorbate in solid phase, uncovered adsorption site and covered adsorption site, and that the equilibrium chemical potentials of these components should be equalized, a new model was presented for describing ion adsorption isotherm in liquid/solid systems. The proposed model fit well the experimental data obtained from the examined samples.
