Removal of Heavy Metals in Storm Water Runoff Using Porous Vermiculite Expanded by Microwave Preparation

Abstract

The main objective of this study was to examine the effectiveness of vermiculite for removing heavy metals from water. Vermiculite components were analyzed by X-ray fluorescence, and the concentrations of metal ions were measured by inductively coupled plasma spectrometry. Serial batch kinetic tests and batch sorption tests were conducted to determine the removal characteristics for heavy metals in aqueous solutions. Solution pH values of tests with the inflated vermiculites generally increased and then stabilized. Equilibrium pH was generally established within 5 h. Removal rates of inflated vermiculite were tested at the initial concentration of 3 mg/L. At equilibrium concentrations, except for chromium (36.23%), most heavy metals were effectively removed (96.08–98.54%). Finally, sorption data were correlated with both Langmuir and Freundlich isotherms. For each metal, the Q max obtained using the Langmuir isotherm was as follows: lead, 725.4 mg kg−1; cadmium, 568.8 mg kg−1; zinc, 540.2 mg kg−1; copper, 457.2 mg kg−1; and chromium, 0.9 mg kg−1. The study results indicate that inflated vermiculite has outstanding removal rates and therefore can be used as an adsorbent for various heavy metals.