Adsorption Investigation Of Ni²⁺ Onto The Polyvinylidene Fluoride Resin Modified By Dithylenetriamine Pentaacetic Acid

The modification of polyvinylidene fluoride (PVDF) resin was conducted using the combination methods of solution blending technique and phase inversion process. Polyaminecarboxylate chelating groups, using the amide covalent bond reaction between dithylenetriamine pentaacetic acid (DTPA) and melamine (MA), were blended to PVDF resin to form MA-DTPA/PVDF resin. The synthesized condition of the modified resin was optimized by the orthogonality experiments, and the components of the cast solution were obtained. The modified resin was characterized by thermogravimetry (TG), X-ray diffraction measurement (XRD), Fourier transform infrared ray (FTIR), nuclear magnetic resonance spectroscopy (NMR) and scanning electron microscopy (SEM). The adsorption properties of the modified resin for nickle ion were examined using static and dynamic adsorption methods, respectively.The effects of pH, initial metal ion concentration and the temperature on the sorption capacity of the modified resin have been investigated. The result of the experiment indicates that the optimal dosage of DTPA, MA PVDF and PVP were 50 g/L,64 g/L,100 g/L and 12.5 g/L, respectively. TG measurement illustrates that the modified resin has excellent thermal stability, and XRD measurement reveals that the modified resin shows the similar crystal structure as that of the pristine PVDF. In addition, FTIR and NMR measurements clearly demonstrate that the polyaminecarboxylate functional group has been blended into the PVDF successfully.The static adsorption results indicate that the MA-DTPA/PVDF resin possesses an excellent adsorption property of Ni²⁺ and the saturation adsorption capacity is 16.68 mg/g. The adsorption isotherm fits better to the Langmuir isotherm model. The adsorption kinetics accords with the pseudo-second-order kinetics model. ?H°is less than 0,â–³G°is lower than 0, andâ–³S°is less than 0, which shows that the adsorption of Ni²⁺ by the modified resin is a spontaneous and exothermic process.The fixed bed adsorption results indicate that the modified PVDF resin can be used for the treatment of the nickel-containing wastewater with low concentrations; there is an optimal flow rate for the removal of nickel ion. Thomas model is found suitable for describing the whole dynamic behavior.