Synthesis of poly[n-isopropylacrylamide-co-[2-(methylthio)ethyl methacrylate]] for gold(III) ion adsorption

Abstract

A new copolymer poly[N-isopropylacrylamide-co-[2-(methylthio)ethyl methacrylate]], poly(NIPA-co-MTEMA), with bis(acrylamide) as a crosslinking agent was synthesized by free radical polymerization. The optimum condition for the synthesis of homogeneous and heterogeneous poly(NIPA-co-MTEMA) could be achieved with 10 mM MTEMA in 5.0 %(v/v) ethanol and 30 mM MTEMA in 20.0 %(v/v) ethanol, respectively. The copolymers were characterized by Fourier transforms infrared and Raman spectroscopy, scanning electron microscope, thermal gravimetric analysis and differential scanning calorimetry. The lower critical solution temperature (LCST) of homogeneous poly(NIPA) and poly(NIPA-co-MTEMA) polymers was nearly about 32 ℃. The adsorption of gold(III) ion was studied in batch method. The optimum pHs for the adsorption of homogeneous and heterogeneous polymers were 1-3 and 1-5, respectively. The suitable adsorption time was 3 hours at 50 ℃ when using a rod shape copolymer (0.7 cm diameter and 1 cm length). The adsorption behavior of homogeneous polymers fitted to the Langmuir and Freundlich isotherms. For heterogeneous polymers fitted to the Freundlich isotherm. The desorption equilibria were reached within 2-3 hours at 10 ℃ by 0.1 M Thiourea in 5% HCl except for heterogeneous poly(NIPA) for which DI water was appropriate.