Fast and efficient aqueous arsenic removal by functionalized MIL-100(Fe)/rGO/δ-MnO2 ternary composites: Adsorption performance and mechanism.

Because of its significant toxicological effects on the environment and human health, arsenic (As) is a major global issue. In this study, an Fe-based metal-organic framework (MOF) (Materials of Institut Lavoisier: MIL-100 (Fe)) which was impregnated with reduced graphene oxide (rGO) by using a simple hydrothermal method and coated with birnessite-type manganese oxide (δ-MnO2) using the one-pot reaction process (MIL-100(Fe)/rGO/δ-MnO2 nanocomposites) was synthesized and applied successfully in As removal. The removal efficiency was rapid, the equilibrium was achieved in 40 min and 120 min for As(III) and As(V), respectively, at a level of 5 mg/L. The maximum adsorption capacities of As(III) and As(V) at pH 2 were 192.67 mg/g and 162.07 mg/g, respectively. The adsorbent revealed high stability in pH range 2-9 and saturated adsorbent can be fully regenerated at least five runs. The adsorption process can be described by the pseudo-second-order kinetic model and Langmuir monolayer adsorption. The adsorption mechanisms consisted of electrostatic interaction, oxidation and inner sphere surface complexation.

Functional rGO aerogel as a potential adsorbent for removing hazardous hexavalent chromium: adsorption performance and mechanism.

A novel functional rGO aerogel was synthesized by a facile hydrothermal method. In this process, graphene oxide (GO) was used as the precursor and oxidant to synthesize the aerogels. Ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) and pyrrole monomer (reducing agent) were selected to use as hole scavenger and nitrogen sources. The obtained EDTA-2Na/polypyrrole (Ppy)/rGO aerogel (EPGA) has a high adsorption capacity for Cr(VI) anions, and the maximum adsorption capacity reached 361 mg/g at 298 K at pH of 2. In addition, EPGA exhibited a good ability to selectively remove Cr(VI) anions under the effect of coexisting ions (Cl-, NO3-, SO42-, PO43-, Ni+, Cu2+, Zn2+, and Cd2+) and good regeneration ability. The kinetics process and adsorption isotherm can be fitted well with the pseudo-second-order kinetic model and Freundlich isotherm model, respectively. The removal mechanism involved electrostatic interaction, reduction, ion exchange, and chelation process. This work provides a simple and environmentally friendly synthetic route for EPGA, which will be a potential candidate for efficient removal Cr(VI) anions from industrial wastewater.