Unob Fuangfa, Wongsiri Benjawan, Phaeon Nuchnicha, Puanngam Mahitti, Shiowatana Juwadee
Department of Chemistry, Faculty of Science, Chulalongkorn University, Payathai Road, Bangkok 10330, Thailand.
J Hazard Mater. 2007 Apr 2;142(1-2):455-62. doi: 10.1016/j.jhazmat.2006.08.049. Epub 2006 Aug 25.
Silica gel is widely used in research laboratories, especially for the purification of organic compounds. Consequently, waste silica gel is generated in increasing amounts. In this work, waste silica was modified by coating its surface with iron oxide aiming to obtain an effective adsorbent for metal removal from wastewater. In the preparation of the adsorbent, the optimal pretreatment temperature and iron concentration were investigated. The coated waste silica was characterized for BET surface area, pore size, specific pore volume and iron content. Iron oxide-coated waste silica was tested for the adsorption of Pb(II), Cu(II), Cd(II) and Ni(II) from solutions in a batch system. The effect of contact time, pH and salt concentration on metal adsorption was investigated. It was found that the adsorption of metals occurred rapidly and reached equilibrium within 30 min. The pH suitable for metal adsorption was between 6 and 7 and leaching of iron from the coating was observed only at pH 3 or lower. The presence of salt reduced the adsorption efficiency of the adsorbent. The adsorption behavior followed both Langmuir and Freundlich isotherms (25 degrees C). Finally, the efficacy of the adsorbents was investigated using aqueous lab waste where removal efficiencies ranging from 62 to 89% were achieved when the initial metal concentrations ranged from 13 to 42 mg L(-1).
硅胶在研究实验室中广泛使用，尤其是用于有机化合物的纯化。因此，产生的废硅胶数量不断增加。在这项工作中，通过用氧化铁包覆废硅胶的表面对其进行改性，旨在获得一种从废水中去除金属的有效吸附剂。在吸附剂的制备过程中，研究了最佳预处理温度和铁浓度。对包覆后的废硅胶进行了比表面积、孔径、比孔容和铁含量的表征。在间歇系统中测试了氧化铁包覆的废硅胶对溶液中Pb(II)、Cu(II)、Cd(II)和Ni(II)的吸附性能。研究了接触时间、pH值和盐浓度对金属吸附的影响。结果发现，金属的吸附迅速，在30分钟内达到平衡。适合金属吸附的pH值在6到7之间，仅在pH值为3或更低时观察到涂层中铁的浸出。盐的存在降低了吸附剂的吸附效率。吸附行为符合Langmuir和Freundlich等温线（25℃）。最后，使用实验室废水研究了吸附剂的效果，当初始金属浓度在13至42 mg L(-1)范围内时，去除效率达到62%至89%。
