Abstract

The immobilization and removal of trivalent arsenic [As(III)] onto A-doped graphene (AG: AC(93)H(24)) nanoadsorbents with first-row transition metals (A: Sc-Zn) was characterized by means of theoretical computations in the gas phase and in an explicit/implicit solvent media. In the gas phase, AG adsorbents have a high affinity toward As(III), with adsorption energies in the range of 1.2-2.0 eV, where the chemical acid-base interaction takes place mainly by bidentate surface complexation like in mineral surfaces. Moreover, the adsorption stability is improved at least 229% compared to the adsorption onto intrinsic graphene. The different binding abilities emerge from the interplay and balance between intermolecular electrostatic interactions and repulsive steric terms due to Pauli repulsion; the best adsorbents show high intermolecular electrostatic energies E-els (-0.4 eV), and low contributions of the repulsive steric terms as a result of the decrease in the number of 3d electrons. The analysis of the stability in the water model indicates that all the adsorbents (excepting ScG and ZnG) could be considered as remarkable potential adsorbents of trivalent arsenicals from aqueous sources at neutral pH, and mainly without the competition of water molecules by the adsorption active sites. The bidentate surface complexation is not affected underwater, and the chemisorption remains as the main adsorption mechanism whereby As(III) is immobilized. Therefore, doped graphene with first-row transition metals could be considered as a new class of remarkable nanoadsorbents for wastewater treatment and water purification, where in terms of energy saving, a pre-oxidation process to convert As(III) to As(V) is not required. (C) 2019 Elsevier B.V. All rights reserved.