Modification of clay mineral with 2-(3-(2-aminoethylthio)propylthio)ethanamine for removal of metals from water

Abstract

The modified hectorite for the removal of mercury(II) and silver(I) ions from water was prepared. The hectorite was grafted with 3-aminopropyltriethoxysilane via reaction with hydroxyl groups on the hectorite surface, followed by ethyl-2-bromopropionate and 2-(3-(2-aminoethylthio)propylthio)ethanamine, respectively. X-ray diffraction spectroscopy, thermo gravimetric analysis, surface area and porosity analysis, infrared spectroscopy and CHN elemental analysis were used to characterize the modified hectorite. The results showed that the basal spacing of the modified hectorite increased from 12.7 to 18.4 Å and the surface area of hectorite decreased from 54.48 to 16.48 m2 g-1. The content of carbon, hydrogen and nitrogen were 9.63, 2.16 and 1.78 % by weight, respectively. Then, the effect of parameters that could affect the extraction of metal ions such as, pH of metal ions solutions, extraction time, adsorbent dose and kinetics, ionic strength, interfering ions and initial concentration of metal ions in solutions, were studied using batch method. The initial pH of solutions suitable for removal of Hg(II) and Ag(I) ions were in the range of 3-8 and 4-8, respectively, using the extraction time of 60 min. Furthermore, the adsorption ability of the adsorbent was independent to ionic strength and interfering ions in the solutions. The adsorption kinetics followed a pseudo-second order kinetics and the adsorption isotherm fit well the Langmuir model for the two metal ions. The maximum adsorption capacities were 0.33 and 0.47 mmol g-1 for Hg(II) and Ag(I) ions in solutions having initial pH of 3.0 at 25°C. In addition, the adsorbent could also remove Hg(II) and Ag(I) ions in the real water samples.