Synthesis of polystyrene-coated magnetic particles modified with 2-(3-(2-Aminoethylthio) propylthio) ethanamine for extraction of Hg(II) and Ag(I) Ions

Abstract

A new adsorbent for mercury(II) and silver(I) extraction from aqueous solution was prepared using cobalt ferrite magnetic particles. To improve the stability of the particles in acidic solution, the cobalt ferrite particles were coated with polystyrene via atom transfer radical polymerization. The ligand 2-(3-(2-aminoethylthio)propylthio)ethanamine (AEPE) was further grafted on the polystyrene-coated particles to improve the extraction efficiency and selectivity toward Hg(II) and Ag(I) ions. The obtained adsorbents were characterized by Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, thermogravimetric analysis, scanning electron microscopy and surface area analysis. The results from characterization indicated the presence of the desired molecules on the magnetic particles surface. The extraction efficiency of adsorbent was evaluated using batch method. The effect of solution pH, extraction time, ionic strength and coexisting ions were investigated. The optimal pH for Hg(II) and Ag(I) extraction were pH 7-8 and pH 5-8, respectively, using the extraction time of 60 minutes. The ionic strength and coexisting ions in solution did not affect the extraction efficiency, except for chloride ions. The adsorption isotherm and adsorption kinetics for the two metals followed Langmuir isotherm and pseudo-second order kinetics, respectively. The maximum adsorption capacities were 0.42 and 0.44 mmol g-1 for Hg(II) and Ag(I), respectively. The suitable eluent for the desorption of Hg(II) and Ag(I) were 0.5 M thiourea in 1% HNO3 and 1.0 M thiourea in 1% HNO3, respectively, using the elution time of 60 minutes. The adsorbent gave the highest extraction efficiency for Ag(I) extraction only for the first time application. On the other hand, the adsorbent could be used to extract Hg(II) at least 10 times. Moreover, the adsorbent could also extract Hg(II) and Ag(I) ions in real wastewater samples.