A novel tetraethylenepentamine functionalized polymeric adsorbent for enhanced removal and selective recovery of heavy metal ions from saline solutions†
A series of multi-amine functionalized polymeric adsorbents with polymethacrylate–divinylbenzene as the substrate were facilely prepared for the enhanced removal and selective recovery of Cu(II) and Ni(II) from saline solutions. The optimal experiment of suspension polymerization between divinylbenzene and methylacrylate was designed by response surface methodology. The multi-amine was successfully grafted on polymethacrylate–divinylbenzene beads as evidenced by N–H deformation vibrations in Fourier-transform infrared spectrometry and characteristic absorption peaks of nitrogen in X-ray photoelectron spectroscopy. Among the newly-synthesized multi-amine adsorbents, the tetraethylenepentamine decorated resin (PAMD) exhibited the highest content of N, reaching as high as 20.38%. The maximum adsorption capacity of PAMD for Cu(II) was up to 1.21 mmol g−1, which is obviously superior to such commercial multi-amine resins as Purolite S984. With increasing concentration of NaNO3 in the solutions, the uptake of Cu(II) and Ni(II) onto PAMD was significantly enhanced by up to 74.28% and 75.51%, respectively. It is noteworthy that the separation factor towards Cu(II) became infinite with the help of NaNO3 despite the moderate one (1160.19) in a Cu(II)/Ni(II) salt-free solution, and such interesting characteristics could be potentially applied to prepare high-purity nickel. The salt-promotion effect of PAMD was expressed by the promotion index (Kp). Furthermore, based on the model of a compressed electric double layer, the quantitative simulation of salt-enhanced adsorption was illuminated for the first time. PAMD has also been successfully applied to treat the actual saline effluent, and a greater volume of wastewater can be decontaminated by PAMD (330 BV) compared with S984 (220 BV) under the same conditions. These interesting findings suggest that PAMD could be satisfactorily applied in the advanced treatment of actual saline effluents with low-cost, high-efficiency and good-reproducibility.