Tailoring the arsenic(III) removal ability from water using metal-organic frameworks via metal exchange – A computational study.

• Metal exchange on MFU-4 l based adsorbents promotes the inner-sphere surface adsorption of As(III). • Electrostatic and charge-transfer driving forces determine the adsorption mechanism. • As(III) adsorption is a spontaneous and exothermic process for pristine, Cu(II) and Fe(II)-based MOFs. • Aqueous environments have a weak influence on the adsorption stability of the As(III)-M-MFU-4 l complexes. • The recovery of the adsorbents can be reached by treatment with phosphate-based eluents. Searching and developing efficient adsorbent materials for arsenic removal is critical in water treatment. Recently, Metal-Organic Frameworks (MOFs) have gained attention due to their chemical stability and ability to capture water-soluble arsenic species. Here, we performed a computational chemistry study of the arsenic removal ability by the Zn-based MOF, MFU-4 l [Zn 4(Td) Zn (Oh) Cl 4 (BTDD) 3 ], and the effects of metal exchange [M-MFU-4 l , where M = Fe(II), Ni(II), Cu(II)]. Our results show that M-MFU-4 l based adsorbents promote the inner-sphere surface adsorption of arsenic in a wide range of pH. Metal exchange with Fe(II) species promotes a bidentate arsenic uptake, resulting in the highest adsorption ability compared to the reference system MFU-4 l. Energy decomposition analyses (ALMO-EDA) reveal that electrostatic and polarization driving forces dominate the adsorption mechanism, providing a partial orbital overlapping (coordinative bonding). In addition, thermochemical analyses reveal that arsenic adsorption is a spontaneous and exothermic process at room temperature for pristine, Cu(II) and Fe(II)-based MOFs, which are retained in a wide range of operating temperatures (298–1000 K). Finally, solvent effects have a weak influence on the adsorption stability because attractive electrostatic effects overcompensate the solvation destabilization, while the recovery of the adsorbent materials can be straightforwardly reached by treatment with phosphate-based eluents for repetitive cycles of use. Therefore, this study would provide new insights into MOFs application as technology remediation for arsenic removal from water. [ABSTRACT FROM AUTHOR]