Demand-oriented construction of Mo3S13-LDH: A versatile scavenger for highly selective and efficient removal of toxic Ag(I), Hg(II), As(III), and Cr(VI) from water

Abstract

Inspired by the classic ion-exchange reaction, a single phase material of Mg0.66Al0.34(OH)2(Mo3S13)0.03(NO3)0.14(CO3)0.07·H2O (Mo3S13-LDH) was masterly constructed by intercalating Mo3S132− into the MgAl-LDH gallery. Prepared Mo3S13-LDH displays excellent binding affinity and high selectivity for Ag(I) and Hg(II) in a mixed solution, in which an apparent selectivity order of Hg(II) > Ag(I) ≫ Pb(II), Cu(II), Ni(II), Co(II), Cd(II), and Mn(II) is observed. Enormous capture capacities (qmAg = 446.4 mg/g, qmHg = 354.6 mg/g) and fast equilibration time (within 60 min) place Mo3S13-LDH in the upper ranks of materials for such removal. For oxoanions, As(III) (HAsO32−) and Cr(VI) (CrO42−) can be specifically trapped by Mo3S13-LDH with comparable loading ability (qmAs = 61.8 mg/g, qmCr = 90.6 mg/g) in the coexistence of multiple interfering anions. Notably, high Hg(II) and Cr(VI) concentrations are finally reduced below the safe limit of drinking water. The excellent capture capacity of Mo3S13-LDH benefits from the rational design by following two aspects: (i) the multiple sulfur ligands in Mo3S132− groups give place to various capture modes and different affinity orders for target ions, and (ii) large-sized Mo3S132− groups widen the interlayer spacing of LDH, thereby accelerating the mass transfer process. Furthermore, the satisfactory structural stability of Mo3S13-LDH is also reflected through the unchanged hexagonal prismatic shape after adsorption. All of these highlight the great potential of Mo3S13-LDH for the application in water remediation.