Adsorption of Cd on GO/PAA hydrogel and preliminary recycle to GO/PAA-CdS as efficient photocatalyst.

In this work, a GO (graphene oxide)/PAA (poly acrylic acid) hydrogel was prepared by graft polymerization between GO and AA. It was employed as highly efficient adsorbent for Cd removal from wastewater. The GO/PAA-Cd composite after the adsorption process was recycled through in-situ precipitation to obtain GO/PAA-CdS composites. During the synthesis process, the amounts of GO and AA were optimized to enable the hydrogel with maximum adsorption of Cd (316.4 mg/g at 25 °C). The structure and chemical composites of GO/PAA hydrogel were investigated through FTIR spectra, Raman spectra, and TGA. The adsorption kinetics and isotherms of Cd on GO/PAA were analyzed. The synthesized products served as an efficient adsorbent for Cd and a suitable matrix for the CdS quantum dots formation which was confirmed by various characterizations, including XPS, SEM-EDS and HRTEM. The roles of GO and PAA in the successive adsorption-photocatalyst process were proved to be complementary: PAA improved the adsorption of Cd while GO enhanced the photocatalyst efficiency. The photodegradation rate of MB (30 mg/L) was over 90% within 2 h.