New Chelate Resins Prepared with Direct Red 23 for Cd[sup.2+], Ni[sup.2+], Cu[sup.2+] and Pb[sup.2+] Removal

In this paper, two chelate resins prepared by a simple procedure were used for the removal of Cd[sup.2+], Ni[sup.2+], Cu[sup.2+], and Pb[sup.2+] (M[sup.2+]) from aqueous solutions. Amberlite IRA 402 strongly basic anion exchange resin in Cl[sup.−] form (IRA 402 (Cl[sup.−]) together with Amberlite XAD7HP acrylic ester co-polymer (XAD7HP) were functionalized with chelating agent Direct red 23 (DR 23). The chelate resins (IRA 402-DR 23 and XAD7HP-DR 23) were obtained in batch mode. The influence of interaction time, pH and the initial concentration of DR 23 solution was investigated using UV-Vis spectrometry. The time necessary to reach equilibrium was 90 min for both resins. A negligible effect of adsorption capacity (Qe) was obtained when the DR 23 solution was adjusted at a pH of 2 and 7.9. The Qe of the XAD7HP resin (27 mg DR 23/g) is greater than for IRA 402 (Cl[sup.−]) (21 mg DR 23/g). The efficiency of chelating resins was checked via M[sup.2+] removal determined by the atomic adsorption spectrometry method (AAS). The M[sup.2+] removal by the IRA 402-DR 23 and XAD7HP-DR 23 showed that the latter is more efficient for this propose. As a consequence, for divalent ions, the chelated resins followed the selectivity sequence: Cd[sup.2+] > Cu[sup.2+] > Ni[sup.2+] > Pb[sup.2+]. Additionally, Cd[sup.2+], Cu[sup.2+] and Ni[sup.2+] removal was fitted very well with the Freundlich model in terms of height correlation coefficient (R[sup.2]), while Pb[sup.2+] was best fitted with Langmuir model for IRA 402-DR 23, the Cu[sup.2+] removal is described by the Langmuir model, and Cd[sup.2+], Ni[sup.2+] and Pb[sup.2+] removal was found to be in concordance with the Freundlich model for XAD7HP-DR 23. The M[sup.2+] elution from the chelate resins was carried out using 2 M HCl. The greater M[sup.2+] recovery from chelating resins mass confirmed their sustainability. The chelate resins used before and after M[sup.2+] removal by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analysis were evaluated.