Tetraethylenepentamine-enriched magnetic graphene oxide as a novel Cr(VI) removal adsorbent

Abstract

In this study, a novel Cr(VI) adsorbent, tetraethylenepentamine (TEPA)-enriched magnetic graphene oxide (MGO), was developed. To this end, MGO was synthesized through coprecipitation and then modified with 3-(trimethoxysilyl)-1-propanethiol. Afterward, methacrylic acid was grafted onto modified MGO using free radical polymerization, and TEPA was attached to achieve TEPA-enriched MGO (termed MGOT). Subsequently, the MGOT structure was characterized through FTIR, XRD, TGA, VSM, FESEM, TEM, DLS, zeta potential, and BET analysis. Furthermore, the effect of Cr(VI)/MGOT ratio, temperature, and pH on Cr(VI) sorption was studied using Box–Behnken Design (BBD) in response surface methodology. The results indicated that the quadratic model developed by BBD using Design-Expert software produced optimal results. The numerical optimization revealed the optimal Cr(VI)/MGOT ratio, temperature, and pH to be 1.58, 37.24 °C, and 3.23, respectively. Maximum adsorption capacity at optimal levels was determined to be 287.15 mg/g. In addition, the Lagergren kinetic and Langmuir isotherm models accurately represented the Cr(VI) adsorption process on MGOT. The spontaneous endothermic nature of the adsorption process was demonstrated by its thermodynamic properties. Based on the obtained results, we conclude that MGOT is an excellent reusable adsorbent for Cr(VI) selectivity sorption and magnetic separation from wastewater.