Adsorption characteristics of Cr (III) onto starch‐graft‐poly(acrylic acid)/organo‐modifed zeolite 4A composite: A novel path to the adsorption mechanisms

Superabsorbent polymer are extensively synthesized in our daily life, and have become important scavengers of metal ions dissolved in aquatic environment. Herein, Herein, an in‐depth study was performed to examine the morphology and adsorption properties of the starch‐graft‐poly(acrylic acid)/organo‐modifed zeolite 4A composite by coupling SEM, XRF, and ICP‐MS, and to completely characterize the Cr (III) coordination sphere within the complex by combining DFT calculations and XAS. The results showed that the adsorption capacity of the synthesized composite could reach to a very large value of 651.42 mg g ⁻¹ with initial Cr ³⁺ concentration ascending to 50 mmol L ⁻¹ , while the removal rate decreased continuously. By virtue of DFT calculations and XAS, it was found that the adsorbed chromium was coordinated by four carboxyl O in quasi‐equator plane and two water O in axial direction to form a quasi‐octahedral geometry. The Cr–O/C distance of our compound were very close to those reported values of Cr‐adsorbed organic compounds and polynuclear chromium carboxylate compounds. Finally, the combination of DFT calculations and XAS was demonstrated to be a powerful method to explore the mechanisms of metal ion adsorption onto synthesized composite. POLYM. COMPOS., 39:1223–1233, 2018. © 2016 Society of Plastics Engineers