Preparation of a novel bio-adsorbent of sodium alginate grafted polyacrylamide/graphene oxide hydrogel for the adsorption of heavy metal ion.

A novel bio-adsorbent named SA-PAM/GO hydrogel composites was synthesized through free radical polymerization. The structure and performance were characterized and analyzed by BET, SEM-EDS, FTIR and TGA. After modification, the BET surface area increased more than tripled, which was consistent with SEM results. Under optimal conditions, the maximum adsorption capacity of Cu2+ and Pb2+ were 68.76 mg/g and 240.69 mg/g, respectively. In addition, the research of kinetics and isotherms displayed that the pseudo-second-order kinetic model and the Langmuir isotherm model fitted the data well. After further research, the different adsorption mechanism including physical adsorption, chemical adsorption and electrostatic interactions were discussed. The chemical adsorption accompanying the ion exchange process was confirmed as the staple adsorption mechanism. Furthermore, the adsorbent still maintained good adsorption capacity after 5 cycles of adsorption-regeneration. Therefore, the SA-PAM/GO hydrogel composites have potential to remove the heavy metal ions from water body effectively.

Preparation of acrylamide/acrylic acid cellulose hydrogels for the adsorption of heavy metal ions.

Modified cellulose hydrogels were prepared by blending and cross-linking with acrylamide and acrylic acid. The structure of hydrogels was characterized and analyzed with fourier transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Under the optimized conditions, the maximum absorption capacity in modified cellulose hydrogels of Cu (II), Pb (II) and Cd (II) ions were 157.51, 393.28 and 289.97 mg/g, respectively. In addition, the metal ion adsorption process accorded with pseudo-second-order rate equation and Langmuir adsorption isotherm. Based on the microstructure analysis and adsorption kinetics, the adsorption mechanisms such as physical, chemical, and electrostatic interactions are discussed. The adsorption process was controlled by the ion-exchange mechanism.