1,4,8,11-tetraazacyclotetradecane bound to poly(p-chloromethylstyrene-ethylene glycol dimethacrylate) microbeads for selective gold uptake

Poly(p-chloromethylstyrene-ethylene glycol dimethacrylate) (poly(p-CMS-EGDMA)) polymeric microbeads, with an average size of 186 mum were synthesized by the suspension polymerization of p-CMS in an aqueous medium. To increase the rigidity of the polymeric microbeads EGDMA monomer was added to polymerization medium at 25% for cross-linking. 1,4, 8,11-Tetraazacyclotetradecane (cyclam) was reacted with p-CMS under nitrogen atmosphere for 18 h at 65 degreesC. Fourier transform infrared (Fr-IR) spectrophotometry, thermogravimetric analysis (TGA) and elemental analysis were used to characterize the plain and ligand-attached microbeads structures. The affinity of the cyclam-attached poly(p-CMS-EGDMA) microbeads for gold ions were used to test the adsorption/desorption behavior from aqueous media containing different concentrations of gold (0.05-10 mM) at different pH values (2.5-5.0). The uptake of gold ions onto the poly(p-CMS-EGDMA) microbeads from solution was 6.18 mmol g(-1). More than 95% of the adsorbed gold ion was desorbed over 48 h in a desorption medium containing 0.8 M thiourea in 3 M HCl. Poly(p-CMS-EGDMA) co-polymeric microbeads containing the cyclam ligand were found to be suitable for repeated use without noticeable loss of adsorption capacity. The selective adsorption of gold onto the microbeads at pH 3.0 was very high compared to Cu(II), Ni(II), Co(II) and Zn(II). (C) 2002 Elsevier Science B.V. All rights reserved.