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J Hazard Mater. 2018 Sep 15;358:145-154. doi: 10.1016/j.jhazmat.2018.06.033. Epub 2018 Jun 24.

Multifunctional photoactive and selective adsorbent for arsenite and arsenate: Evaluation of nano titanium dioxide-enabled chitosan cross-linked with copper.

Author information

1
Yale University, School of Forestry and Environmental Studies, 195 Prospect St., New Haven, CT 06511, United States; Nanosystems Engineering Research Center for Nanotechnology-Enabled Water Treatment (NEWT), Yale University, New Haven, CT 06511, United States.
2
Yale University, School of Forestry and Environmental Studies, 195 Prospect St., New Haven, CT 06511, United States.
3
Yale University, Department of Chemical and Environmental Engineering, 17 Hillhouse Ave, New Haven, CT 06511, United States.
4
Yale University, School of Forestry and Environmental Studies, 195 Prospect St., New Haven, CT 06511, United States; Nanosystems Engineering Research Center for Nanotechnology-Enabled Water Treatment (NEWT), Yale University, New Haven, CT 06511, United States; Yale University, Department of Chemical and Environmental Engineering, 17 Hillhouse Ave, New Haven, CT 06511, United States. Electronic address: julie.zimmerman@yale.edu.

Abstract

A novel multifunctional sorbent material of nano-titanium dioxide-enabled chitosan beads cross-linked with copper (CuTICB) is capable of photo-oxidation of As(III) to the less-toxic and more easily adsorbed As(V) in UV light and selective adsorption of arsenite (As(III)) and arsenate (As(V)) in the presence of phosphate, a strong adsorptive competitor and inhibitor of arsenic removal performance. CuTICB is an attractive sorbent as simultaneous photo-oxidation and adsorption reduces treatment time and cost while selective adsorption improves removal efficiency of arsenic in typical environmental conditions where competitive ions are predominant. In CuTICB, nano-titanium dioxide (n-TiO2) anatase photo-oxidizes As(III) to As(V) through generation of reactive oxygen species. Additionally, Cu-chitosan bidentate crosslinkers form through Lewis acid-base coordinate bonding between Cu(II) and chitosan amine groups resulting in cationic behavior that electrostatically favors As(V) chelation even when phosphate concentrations are orders of magnitude higher. The influence of copper and n-TiO2 loading on arsenic photo-oxidation and selective removal over phosphate was explored to optimize CuTICB design using batch experiments under varying systems conditions. For a system requiring both photo-oxidation and selective adsorption, it was found that copper and n-TiO2 act non-linearly and synergistically, where maximum loadings of both does not yield the optimal selectivity or removal efficacy.

KEYWORDS:

Adsorption; Arsenic; Chitosan; Photochemistry; Selective

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