Investigation of Zn2+ and Cd2+ Adsorption Performance by Different Weathering Basalts
2016
Qi, Shuo | Xue, Qiang | Niu, Zhenru | Zhang, Yankun | Liu, Fei | Chen, Honghan
Geological barriers play an important role in preventing pollution of groundwater. Basalts are common geological media; however, there have not been any studies that report the effect of basalt type on the metal ion adsorption performance. In this study, we explored the metal ion (Zn²⁺ and Cd²⁺) adsorption ability of two kinds of weathering basalts, the origin weathering basalt (WB) and the eluvial deposit (ED), both of which were derived from same basaltic formation. Characteristics of the sediments were examined by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Barrett-Joyner-Halenda (BJH) measurement, and the rapid potentiometric titration (RPT) method. Batch experiments were performed to evaluate the Zn²⁺ and Cd²⁺ adsorption performance of WB and ED and how adsorption was affected by contact time, initial metal ion concentration, pH, and ionic strength. Despite WB and ED having similar chemical compositions, WB exhibited better adsorption than ED likely due to the fact that WB was rougher and had more small-sized spherical structures and stronger electrostatic forces. The adsorption process fits the Freundlich isotherm model well. The adsorption efficiency decreased with a decrease of pH (from 4 to 2) and with increasing ionic strength. These results suggest that a geological barrier composed of WB media might be able to effectively sequester metallic contaminants to prevent them from reaching groundwater.
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