Crosslinked hydrogels of polyethylenimine and graphene oxide to treat Cr(VI) contaminated wastewater

This research papers reports the synthesis of graphene oxide (GO) and polyethylenimine (PEI) based crosslinked nanocomposite hydrogels (GO/PEI-NCH) for its application as potential adsorbent to treat Cr(VI) polluted water. To synthesize GO/PEI-NCH, graphene oxide was initially amine functionalized using 3-aminopropyltriethoxysilane (APTES) which was subsequently grafted with PEI. Successful functionalization of GO with APTES and the crosslinked hydrogel network formation was evidenced by characterizing samples using SEM, X-ray diffraction, Raman, FTIR and TGA. Approximately 97% Cr(VI) was adsorbed from the chromium solution of 50 mg/L concentration at pH 2 with 0.5 g/L mass of GO/PEI-NCH. Further, adsorption isotherm correlated well with Langmuir model and predicted homogenous monolayer adsorption with the adsorbent having energetically identical binding sites. GO/PEI-NCH exhibited 443.8 mg/g maximum adsorption capacity for Cr(VI). Adsorption kinetics was well defined using pseudo-second-order model. GO/PEI-NCH could be easily and efficiently regenerated using HCl solution and it exhibited good stability and reusability for ten continuous adsorption-desorption cycles. Therefore, GO/PEI-NCH is a promising candidate to treat Cr(VI) ions contaminated wastewater.