Adsorption of Cd(Ⅱ) from acidic aqueous solutions by tourmaline as a novel material

作     者：WANG CuiPing WANG BaoLin LIU JingTing YU Li SUN HongWen WU JiZhou 

作者机构：Key Laboratory of Pollution Processes and Environmental Criteria of the Ministry of EducationCollege of Environmental Science andEngineeringNankai UniversityTianjin 300071China 

出 版 物：《Chinese Science Bulletin》 (科学通报(英文版))

年 卷 期：2012年第57卷第24期

页      面：3218-3225页

学科分类：083002[工学-环境工程] 0830[工学-环境科学与工程（可授工学、理学、农学学位）] 081901[工学-采矿工程] 0819[工学-矿业工程] 08[工学] 

基　　金：supported by the National Natural Science Foundation of China (20907024) the Fundamental Research Funds for the Central Universities 

主　　题：酸性水溶液 吸附时间 镉(Ⅱ) 电气石 Langmuir模型 Freundlich模型 碱性水溶液 Cd(Ⅱ) 

摘      要：Batch experiments were conducted to investigate the behavior and mechanisms for the adsorption of Cd(Ⅱ) from aqueous solutions by tourmaline under acidic conditions. The results indicated that the adsorption of Cd(Ⅱ) significantly depend on the adsorption time, temperature, and the initial concentration of the metal ion. Furthermore, tourmaline had a very good adsorption capacity for Cd(Ⅱ) in acidic, neutral and alkaline aqueous solutions. This good adsorption capacity is attributed to the observation that tourmaline can automatically adjust the pH values of acidic (except pH 2.0 and 3.0), neutral or alkaline aqueous solutions to 6.4. Specifically, the removal capacity for Cd(Ⅱ) was higher at strongly acidic pH values (in contrast to industrial wastewater pH values) compared to that obtained for other types of adsorbents. Furthermore, the results obtained in this study showed good fits to the Langmuir and Freundlich adsorption isotherms. However, the Langmuir model fit better than the Freundlich model. The maximum uptake of Cd(Ⅱ) by tourmaline was 31.77, 33.11 and 40.16 mg/g at pH 4.0 at 15, 25 and 35°C, respectively. Therefore, tourmaline is an effective adsorbent for the removal of Cd(Ⅱ) from acidic aqueous solutions. In addition, the kinetics for the Cd(Ⅱ) adsorption by tourmaline closely followed the pseudo-second-order model. The thermodynamic parameters indicated that adsorption was feasible, spontaneous, and endothermic. Furthermore, the pH variation after adsorption, ζ-potential, metal ions desorbed and released, and FT-IR analysis indicated that the physisorption and chemisorption mechanisms of tourmaline for heavy metals. These mechanisms included water that was automatically polarized by tourmaline, the ion exchange process, and electropolar adsorption. Among the mechanisms, the automatic polarization of water caused by tourmaline is a unique adsorption mechanism for tourmaline.