Department of Chemistry, Jamia Millia Islamia, New Delhi, 110025, India,
Environ Sci Pollut Res Int. 2013 Aug;20(8):5425-40. doi: 10.1007/s11356-013-1543-y. Epub 2013 Feb 20.
Arsenic contamination of groundwater is a major threat to human beings globally. Among various methods available for arsenic removal, adsorption is fast, inexpensive, selective, accurate, reproducible and eco-friendly in nature. The present paper describes removal of arsenate from water on zirconium oxide-coated sand (novel adsorbent). In the present work, zirconium oxide-coated sand was prepared and characterised by infrared and X-ray diffraction techniques. Batch experiments were performed to optimise different adsorption parameters such as initial arsenate concentration (100-1,000 μg/L), dose (1-8 g/L), pH of the solution (2-14), contact time (15-150 min.), and temperature (20, 30, 35 and 40 °C). The experimental data were analysed by Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. Furthermore, thermodynamic and kinetic parameters were evaluated to know the mode of adsorption between ZrOCMS and As(V). The maximum removal of arsenic, 97 %, was achieved at initial arsenic concentration of 200 μg/L, after 75 min at dosage of 5.0 g/L, pH 7.0 and 27 ± 2 °C. For 600 μg/L concentration, the maximum Langmuir monolayer adsorption capacity was found to be 270 μg/g at 35 °C. Kinetic modelling data indicated that adsorption process followed pseudo-second-order kinetics. The mechanism is controlled by liquid film diffusion model. Thermodynamic parameter, ΔH°, was -57.782, while the values of ΔG° were -9.460, -12.183, -13.343 and -13.905 kJ/mol at 20, 30, 35 and 40 °C, respectively, suggesting exothermic and spontaneous nature of the process. The change in entropy, ΔS°= -0.23 kJ/mol indicated that the entropy decreased due to adsorption of arsenate ion onto the solid adsorbent. The results indicated that the reported zirconium oxide-coated marine sand (ZrOCMS) was good adsorbent with 97 % removal capacity at 200 μg/L concentration. It is interesting to note that the permissible limit of arsenic as per World Health Organization is 10 μg/L, and in real situation, this low concentration can be achieved through this adsorbent. Besides, the adsorption capacity showed that this adsorbent may be used for the removal of arsenic from any natural water resource.
地下水砷污染是全球范围内对人类的主要威胁。在现有的各种除砷方法中，吸附法具有快速、廉价、选择性好、准确、重现性好和环境友好等特点。本文描述了利用氧化锆涂层砂（新型吸附剂）从水中去除砷酸盐。本工作采用红外和 X 射线衍射技术制备和表征了氧化锆涂层砂。通过批量实验优化了不同的吸附参数，如初始砷酸盐浓度（100-1000μg/L）、剂量（1-8g/L）、溶液 pH 值（2-14）、接触时间（15-150min）和温度（20、30、35 和 40°C）。通过 Langmuir、Freundlich、Temkin 和 Dubinin-Radushkevich 等温线模型对实验数据进行了分析。此外，还评估了热力学和动力学参数，以了解 ZrOCMS 和 As(V) 之间的吸附模式。在初始砷浓度为 200μg/L、剂量为 5.0g/L、pH 值为 7.0 和 27±2°C 时，砷的去除率最高，达到 97%。对于 600μg/L 的浓度，在 35°C 下，最大的单层 Langmuir 吸附容量为 270μg/g。动力学模型数据表明，吸附过程遵循准二级动力学。该机制受液膜扩散模型控制。热力学参数ΔH°为-57.782，而在 20、30、35 和 40°C 下，ΔG°的值分别为-9.460、-12.183、-13.343 和-13.905kJ/mol，表明该过程是放热和自发的。熵变ΔS°=-0.23kJ/mol表明，由于砷酸盐离子吸附到固体吸附剂上，熵减小。结果表明，所报道的氧化锆涂层海砂（ZrOCMS）是一种去除率为 97%的良好吸附剂，在 200μg/L 浓度下的去除率为 97%。值得注意的是，世界卫生组织规定的砷允许限量为 10μg/L，在实际情况下，通过这种吸附剂可以达到这一低浓度。此外，吸附容量表明，这种吸附剂可用于去除任何天然水源中的砷。
