Preparation and characterization of melamine-formaldehyde-DTPA chelating resin and its use as an adsorbent for heavy metals removal from wastewater

Melamine-formaldehyde-diethylenetriaminepentaacetic acid (MF-DTPA) resin was prepared as a new adsorbent for removing heavy metals from wastewater effluents. The resin was synthesised by anchoring the chelating agent diethylenetriaminepentaacetic acid (DTPA) to melamine via amide covalent bond during melamine-formaldehyde condensation reaction in an acidic aqueous medium. The effects of reaction parameters (temperature, acidity, and water content) on resin characteristics (water regain, rigidity, DTPA functionality, and porosity) were monitored to specify the best synthesis conditions. The resin was chemically characterized using infrared spectroscopy (FTIR), elemental analysis (EA), thermal programmed decomposition-mass spectrometry (TPD-MS), solid-state 13C NMR and 15N NMR, and was morphologically characterized using N2 gas adsorption/desorption (BET analysis) and field emission-scanning electron microscopy (FE-SEM). The water regain factor was also calculated to determine hydrophilic character of the resin. The simultaneous adsorption performance of MF-DTPA resin towards selected heavy metals, Co(II), Cd(II), Zn(II), and Cu(II), was discussed. Quantitative analysis for adsorption was conducted using atomic absorption to investigate the kinetics, adsorption isotherm and thermodynamics of the removal process considering pH, initial concentration, temperature, and contact time as controlling parameters. The mechanism of adsorption was suggested based on experimental results. This work shows the potential application of the MF-DTPA resin for removing heavy metals from wastewaters.