Probing the surface chemistry of tunable biopolymer-based adsorbents with toxic and non-toxic pollutants Bernd Steiger and Dr. Lee Wilson Department of Chemistry, University of Saskatchewan, 110 Science Place, Canada Sustainable and environmentally conscious application of green adsorbents to meet global water security challanges is garnering increasing research interest. The removal of oxyanions such as arsenate or sulfate or organic dye remediation is a key challenge. To improve the adsorption properties, the adsorption mechanism of the individual pollutant has to be elucidated to gain molecular insights onto the surface characteristic of adsorbents. Herein, chitosan and alginate derived polyelectrolyte complexes with aluminium as active site were prepared and their physicochemical characteristics investigated. The aluminium content during synthesis was varied and the effect onto the adsorption properties was investigated also. Characterization was performed through various techniques (XPS, XRF, 27 Al and 13 C solids NMR). Based on the selected active site, Al(III), fluoride and arsenate as probes were chosen due to their chemisorption behaviour in addition to sulfate. To probe the role of multi-dentate binding and the organic fractions, anionic dyes (reactive black 5 and methyl orange) were used in conjunction with the cationic dye methylene blue. Isotherm models (Langmuir, Freundlich, Hill and Scatchard) were used to investigate not only the adsorption capacity and homogeneity of the adsorption sites, but also show (non-)cooperativity of the adsorbate binding onto the adsorbate. Regeneration of the adsorbent was investigated with sulfate as model anion for electrostatic binding. Additionally, arsenate remediation was further investigated in real water samples to investigate the effect of salinity. The unique structure-function properties of these polysaccharide composites are modular by design that will provide sustainable adsorbent technology to address emerging global water security challenges. References 1. A. Kumar, P. Paul, S.K. Nataraj, Bionanomaterial Scaffolds for Effective Removal of Fluoride, Chromium, and Dye, ACS Sustain. Chem. Eng. 5 (2017) 895–903. https://doi.org/10.1021/acssuschemeng.6b02227 2. M.M. Hassan, M.H. Mohamed, I.A. Udoetok, B.G.K. Steiger, L.D. Wilson, Sequestration of Sulfate Anions from Groundwater by Biopolymer-Metal Composite Materials, Polymers (Basel). 12 (2020) 1502. https://doi.org/10.3390/polym12071502 3. I.A. Udoetok, O. Faye, L.D. Wilson, Adsorption of Phosphate Dianions by Hybrid Inorganic–Biopolymer Polyelectrolyte Complexes: Experimental and Computational Studies, ACS Appl. Polym. Mater. 2 (2020) 899–910. https://doi.org/10.1021/ acsapm.9b01123. 4. B.G.K. Steiger, I.A. Udoetok, O. Faye, L.D. Wilson, Counterion Effects in Metal Hybrid Biopolymer Materials for Sulfate Adsorption: An Experimental and Computational Study, ACS Appl. Polym. Mater. (2021) acsapm.1c00706. https://doi. org/10.1021/acsapm.1c00706
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