Ultra-high adsorption capacity and selective removal of Congo red over aminated graphene oxide modified Mn-doped UiO-66 MOF

Abstract

A new adsorbent composite Mn-doped UiO-66/Aminated-graphene oxide (Mn-UiO-66@GO-NH2) was synthesized via solvothermal method and well-characterized by XRD, SEM, EDX, TGA, FT-IR, N2 adsorption/desorption analysis and zeta potential. The as-synthesized Mn-UiO-66@GO-NH2 composite showed excellent performance toward Congo red dye adsorption with ultra-high capacity of 1265.82 mg/g. Adsorption performance of Mn-UiO-66@GO-NH2 composite and effect of pH on its adsorption capacity were investigated. The adsorption process fitted well with pseudo-second order and both Langmuir and Freundlich models. Thermodynamic of the process showed that the adsorption of CR on Mn-UiO-66@GO-NH2 composite is an endothermic process. In addition, Mn-UiO-66@GO-NH2 composite displays a good adsorption selectivity toward CR among two other dyes cationic methylene blue (MB) and anionic methyl orange (MO). The mechanism of the removal is proposed to be a combination of electrostatic attraction, π-π stacking, hydrogen bonding, and pore filling mechanism. The good reusability indicates that Mn-UiO-66@GO-NH2 composite can be applied for practical wastewater treatment.