Adsorption of chromium(VI) from saline wastewater using spent tea-supported magnetite nanoparticle

Spent tea-supported magnetite (ST/Mag) nanoparticles were synthesized as an adsorbent for the removal of hexavalent chromium [Cr(VI)] from saline wastewater. Prepared ST/Mag adsorbent was characterized using X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. Various factors affecting the uptake behavior such as pH, contact time, initial concentration of metal ions, adsorbent dose, coexisting ions, and desorption behavior were studied using batch tests. The results revealed that adsorption of Cr(VI) was highly pH dependent and the kinetics of the adsorption followed by the Avrami fractional-order and pseudo-second-order kinetic models. The results showed that the adsorption isotherms were more accurately represented by Langmuir and Liu isotherm models with a sorption capacity of 30.0 mg g⁻¹. Adsorption experiments with co-ions indicated that the adsorptive removal of Cr(VI) ions was slightly decreased. Desorption studies using alkaline eluents showed maximum recovery of ST/Mag and only 10% decrease occurring in maximum adsorption capacity after five cycles. The ST/Mag nanoparticles proved to be a very prospective adsorbent for Cr(VI) uptake from industrial high-TDS effluents.

以废茶负载磁铁矿（ST/Mag）纳米颗粒作为吸附剂，用于去除含盐废水中的六价铬[Cr(VI)]。采用X射线衍射、扫描电子显微镜及傅里叶变换红外光谱对所制备的ST/Mag吸附剂进行了表征。通过批量吸附实验，系统考察了影响Cr(VI)吸附性能的多项因素，包括pH值、接触时间、金属离子初始浓度、吸附剂投加量、共存离子及脱附行为。结果表明，Cr(VI)的吸附过程具有显著的pH依赖性，吸附动力学行为符合Avrami分数阶动力学模型与准二级动力学模型。研究发现，吸附等温线更准确地拟合Langmuir模型与Liu等温模型，最大吸附容量可达30.0 mg·g⁻¹。共存离子吸附实验结果显示，Cr(VI)的吸附去除率略有降低。采用碱性洗脱剂开展的脱附实验表明，ST/Mag可实现高效回收，且经过5次循环使用后，其最大吸附容量仅下降10%。研究证实，ST/Mag纳米颗粒是一种极具应用前景的吸附剂，可用于从工业高总溶解固体（TDS）废水中去除Cr(VI)