Nekhunguni Pfano Mathews, Tavengwa Nikita Tawanda, Tutu Hlanganani
Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Private Bag X3, WITS 2050, Johannesburg, South Africa.
Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Private Bag X3, WITS 2050, Johannesburg, South Africa.
J Environ Manage. 2017 Jul 15;197:550-558. doi: 10.1016/j.jenvman.2017.04.038. Epub 2017 Apr 15.
In this work, the synthesis of iron (hydr) oxide modified zeolite was achieved through precipitation of iron on the zeolite. The structure and surface morphology of iron (hydr) oxide modified zeolite (IHOMZ) was studied by scanning electron microscopy (SEM), coupled with an energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared (FT-IR) spectra. The efficiency of IHOMZ was then investigated through batch technique for the extraction of As(V) from mine waste water. The optimum parameters for maximum As(V) adsorption were: an initial As(V) concentration (10 mg L), adsorbent dosage (3.0 g), contact time (90 min) and temperature (53 °C). The initial pH of the solution had no compelling effect on As(V) adsorption by IHOMZ. However, adsorption capacity was significantly affected by the solution temperature with 53 °C registering the maximum removal efficiency. The thermodynamic parameters: Entropy (ΔS° = 0.00815 kJ (K mol)), variation of the Gibbs free energy (ΔG°) and enthalpy (ΔH° = 9.392 kJ mol) of As(V) adsorption onto IHOMZ system signified a non-spontaneous and endothermic process. It was noted that Freundlich isotherm model exhibited a better fit to the equilibrium experimental data, implying that the adsorption process occurred on a heterogeneous surface. The kinetic data from As(V) adsorption experiments was depicted by the pseudo-second-order kinetic model (R > 0.999), suggesting a chemisorption adsorption process. The experimental batch equilibrium results indicated that IHOMZ could be used as an effective sorbent for As(V) ion extraction from acid mine drainage.
在本研究中，通过在沸石上沉淀铁实现了铁（氢）氧化物改性沸石的合成。采用扫描电子显微镜（SEM）、能量色散X射线光谱仪（EDX）和傅里叶变换红外光谱（FT-IR）对铁（氢）氧化物改性沸石（IHOMZ）的结构和表面形态进行了研究。然后通过间歇技术研究了IHOMZ从矿山废水中萃取As(V)的效率。As(V)最大吸附量的最佳参数为：初始As(V)浓度（10 mg/L）、吸附剂用量（3.0 g）、接触时间（90 min）和温度（53℃）。溶液的初始pH值对IHOMZ吸附As(V)没有显著影响。然而，吸附容量受溶液温度的显著影响，53℃时去除效率最高。As(V)吸附到IHOMZ体系上的热力学参数：熵（ΔS° = 0.00815 kJ/(K·mol)）、吉布斯自由能变化（ΔG°）和焓（ΔH° = 9.392 kJ/mol）表明该过程是非自发的吸热过程。结果表明，Freundlich等温线模型与平衡实验数据拟合较好，这意味着吸附过程发生在非均相表面。As(V)吸附实验的动力学数据用准二级动力学模型描述（R > 0.999），表明是一个化学吸附过程。间歇平衡实验结果表明，IHOMZ可作为从酸性矿山排水中萃取As(V)离子的有效吸附剂。
