Interlayered modified hydroxides for removal of graphene oxide from water: Mechanism and secondary applications

The extensive use and inevitable release of graphene oxide (GO) to the environment have increased the threat of its exposure to living organisms. This study reports the design of Fe-based hydroxides with different interlayers anions, i.e., Cl⁻, SO₄²⁻, CO₃²⁻, and NO₃⁻ to capture GO from an aqueous medium. Various characterization techniques, including X-ray diffraction (XRD), Fourier transform infrared (FTIR), and scanning electron microscopy (SEM), confirmed the successful synthesis of these different materials. The Fe-hydroxides as Fe-HO/(NO₃) with NO₃⁻ interlayers anions effectively removed up to 190 mg/g GO and was tolerant to a high concentration of background electrolyte, different anions, and increasing ionic strength. These remarkable features of Fe-HO/(NO₃) originated from the weak bonding abilities of interlayers NO₃⁻ anions that facilitated simple self-exfoliation of hydroxide nanosheets, and thus promoted the electrostatic interactions between the positively charged layers of hydroxides and negatively charged GO particles. The coagulated end product (Fe-HO/(NO₃)@GO can be further used in advanced oxidation processes (AOPs) as catalyst or adsorbent for the treatment of different pollutants. We believe that this work not only explains the positive aspect of regulating anions in the hydroxides layers but also provides a direction to develop new materials for environmental remediation.