Selective and Efficient Removal of Toxic Oxoanions of As(III), As(V), and Cr(VI) by Layered Double Hydroxide Intercalated with MoS4 2-

Lijiao Ma, Saiful M. Islam, Hongyun Liu, Jing Zhao, Genban Sun, Huifeng Li, Shulan Ma, Mercouri G Kanatzidis

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Abstract

We demonstrate the highly selective and exceptionally efficient capture of toxic oxoanions of As(III)/As(V) (HAsO3 2-/HAsO4 2-) and Cr(VI) (CrO4 2-) by the Mg/Al layered double hydroxide (Mg/Al-LDH) intercalated with MoS4 2- (MoS4-LDH). The MoS4-LDH exhibits very high removal rates (>99%) of As(III), As(V), and Cr(VI) from complex aqueous solutions. In the presence of many competing nontoxic anions such as SO4 2-, NO3 -, and Cl-, remarkable selectivity for HAsO3 2-, HAsO4 2-, and CrO4 2- is observed. Highly concentrated As(III) and Cr(VI) can be rapidly reduced to <10 ppb, much below the permitted level for drinking water. The maximum adsorption capacities for As(III), As(V), and Cr(VI) are 99, 56, and 130 mg/g, respectively. Sorption isotherms for As(III) and As(V) agree with the Langmuir model, suggesting a monolayer adsorption on the sorbent. The adsorptions of As(V) and Cr(VI) are exceptionally rapid, showing >93% removals within 1 min and >96% removal within 5 min. Sorption kinetics for these oxoanions follows a pseudo-second-order model consistent with a chemisorption involving possible As-S and Cr-S bonding. The Cr(VI) adsorption is accompanied by an oxidation/reduction reaction with MoS4 2- resulting in Cr(III) species. The order of rate constants (k2) is Cr(VI) > As(V) > As(III), which reflects their respective adsorption rates. The S-As and S-Cr interactions and the reduction of Cr(VI) to Cr(III) contribute to the effective uptakes. These results make the MoS4-LDH material a compelling candidate for application in remediation of water polluted with arsenic and hexavalent chromium.

Original languageEnglish
Pages (from-to)3274-3284
Number of pages11
JournalChemistry of Materials
Volume29
Issue number7
DOIs
Publication statusPublished - Apr 11 2017

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ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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