Sorption of divalent metal ions by modified carbopol-based adsorbent nanocomposite hydrogel

Abstract

A new adsorbent, modified Carbopol 934-polyacrylamide network polymer (mCarbo-PAm hydrogel), embedded with silver nanoparticles, has been introduced to remove divalent metal ions. It was prepared by supporting nanosized "Ag" onto a porous modified carbopol 934-polyacrylamide polymer network using free radical polymerization. The nanogels were characterized by different methods, including Fourier Transform Infrared spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Thermogravimetric Analysis (TGA) and swelling kinetics. The outcome exhibited that the loading of Ag nanoparticles onto mCarbo-PAm hydrogel was successful in improving the swelling ability of the gel. The nanocomposite hydrogel sorption results indicated that the affinity order was Pb2+(96.52 %) > Cu2+(86.66 %) > Zn2+(69.64 %) at pH 6.7. Which is better than the mCarbo-PAm hydrogel sample: Pb2+(71.78 %) > Cu2+(69.54 %) > Zn2+(33.92 %). The kinetic results showed that sorption follows pseudo-second-order kinetics at pH 6.7. The thermodynamic studies verified that the adsorption processes were nonspontaneous in the case of Pb2+ and spontaneous in the cases of Cu2+ and Zn2+. The observed adsorption process is endothermic in nature. The work also highlights the reusability of the synthesised adsorbent for the metal ion sorption for upto 8 cycles, wherein, no compromise in adsorption capacity was observed till 5th cycle.