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

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-4l [Zn4(Td)Zn(Oh)Cl4(BTDD)3], and the effects of metal exchange [M-MFU-4l, where M = Fe(II), Ni(II), Cu(II)]. Our results show that M-MFU-4l 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-4l. 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. (c) 2022 Elsevier B.V. All rights reserved.