摘要
研究了水溶液中六价铬Cr(Ⅵ)在Mg/Al型双金属氧化物(Mg/Al-LDOs)上的吸附情况。双金属氧化物(LDOs)能通过吸附环境中的阴离子和水分子来恢复重建水滑石结构。实验表明,Mg/Al-LDOs对Cr(Ⅵ)有很强的吸附能力,其吸附能力和吸附速度都远大于未焙烧的Mg/Al型水滑石,后者的吸附机制主要是离子-离子交换。吸附动力学研究表明,Mg/Al-LDOs对Cr(Ⅵ)的吸附主要发生在0～3h,吸附等温线符合Langmuir和Freundlich方程。Mg/Al-LDOs对Cr(Ⅵ)的平均吸附量大约为64.2mg/g,略低于根据Langmuir方程算出的理论吸附量(74.83mg/g),远小于水滑石的最大阴离子交换容量(301.6mg/g),这主要是环境中的CO2-3离子的竞争吸附引起的。
Many industrial processes such as tanning, galvanization, spin, papermaking, and printing and dyeing cause Cr contamination. Exposure to Cr(Ⅵ) compounds causes skin ulcerations, irritative dermatitum and bronchial carcinomas. Great efforts have been focused on identified minerals that might removal chromium from aqueous. Therefore, adsorption of chromium (Ⅵ) on Mg/Al layered double oxides (Mg/Al LDOs) was studied in laboratory. Mg/Al layered double hydroxides (Mg/Al LDHs) are a group of synthetic clayish minerals with layered structure, in which the basic Me O OH layers are interstratified with anion layers. Mg/Al LDOs obtained by calcination of Mg/Al LDHs at about 500 ℃, adsorb anions from water through the reconstruction of their layered structure. It is demonstrated that the Mg/Al LDOs exhibit interesting adsorption properties removing , and LDOs could be a new type of environmental adsorbent for aqueous in contaminated ecosystems. The results indicate that the adsorption of via rehydration in LDOs is much bigger in amount than in LDHs in which the adsorption occurs through ion exchange. The process of adsorption by Mg/Al LDOs mainly occurred within 0～3 h, and then attended to Elovich Equation and the two constant rate equation. Adsorption isotherms could be both fitted to the Langmuir equation and Freundlich equation. However, the Langmuir equation is more favored. The average Cr(Ⅵ) amount adsorbed by Mg/Al LDOs is about 64.2 mg/g, a little lower than the theoretical anion exchange capacity (74.83 mg/g) calculated from the Langmuir equation, but much lower than the maximal formula anion exchange capacity of Mg/Al LDOs (301.6 mg/g). This is most probably caused by the competitive adsorption of from the solution. The percentage of Cr(Ⅵ) removal can reach above 99%with appropriate amount of adsorbent, and therefore, MgAl LDOs is a successful adsorbent to remove Cr (Ⅵ) in aqueous solution.
出处
《地球化学》
CAS
CSCD
北大核心
2004年第2期208-214,共7页
Geochimica
基金
"十五"国家重点基础研究发展规划项目(G2000078503)
