Synthesis of chelating resins with iminodiacetic acid and its wastewater treatment application

The chelating resins have high potential applications for the selective removal and recovery of metal ions from industrial waste solutions. The hydrophilic acrylate monomer with the iminodiacetic acid chelating group was prepared from glycidyl methacrylate and iminodiacetic acid at 60degreesC. The microbeads, prepared from acrylate monomer with the iminodiacetic acid chelating group, were employed by inversion suspension polymerization. In the pH range of 2-6, a reasonably good equilibrium sorption capacity is maintained for Cr3+ (ca. 2.7 mmol/g) and Cu2+ (ca. 1.8 mmol/g) in the chelating resins. The adsorption of Cd2+ and Pb2+ on microbeads is clearly affected by the pH of the solution, such that these ions' adsorption capacity increased with the pH of the aqueous solution. The adsorption of Cd2+ (ca. 1.25-1.87 mmol/g) and Pb2+ (ca. 0.99-1.89 mmol/g) showed a maximum at approximately pH = 5 and 6, respectively. The adsorption isotherms of Cr3+ and Cu2+ adsorbed on microbeads were following the Langmuir isotherm, but the adsorption behavior of Cd2+ and Pb2+ were not. The concentration of alkaline earth-metal cations on the range of 0-200 ppm had no influence on metal ions adsorbed capacity of chelating resins. Additionally, NTA (nitrilotriacetic acid) had no significant influence on metal ion adsorption by chelating resins. Furthermore, phenol pollutant can be adsorbed effectively by metal ions chelated microbeads; therefore, the microbeads were useful not only in recovering metal ions but also in the treating phenol pollutants in wastewater. (C) 2002 Wiley Periodicals, Inc.