Biodegradable Cryogels for Adsorption and Electrochemical Oxidation of Organic Dyes
Date
2022-01-03
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Abstract
The supply of clean water is becoming one of the greatest challenges of the 21st century. Therefore, sustainable and cost-effective measures must be developed and implemented to reduce water scarcity and prevent contamination of our water systems. This work aims to develop novel, environmentally-friendly 3D structured adsorbents for the removal of dissolved organic pollutants from wastewater. This was achieved by developing hydrophobic cryogels composed of TEMPO-oxidized cellulose nanofibers (TOCN) and electrochemically exfoliated graphene (EEG). TOCN/EEG cryogels were hydrophobized by incorporating oleic acid (OA) into the precursor gels. The cryogels were synthesized by mixing the components at 50 °C and 300 rpm for one hour, followed by freeze-drying the gels. The effect of OA loading, TOCN/EEG weight ratios (1:1 and 1:2), and initial solids content were systematically investigated through microstructural and rheological characterization of the precursor gels, and the morphology and adsorption capacity of the derived cryogels. The optimum OA loading for the hydrophobization of TOCN (HTOCN) was found to be 5 wt.%, at which the strongest gel was obtained. The initial solids content and EEG loadings in the precursor gel alter the morphology and adsorption capacity of the derived cryogels. The maximum adsorption uptake was increased by 180% for the 1:1 HTOCN/EEG weight ratio when the initial solids content in the precursor gels was increased from 1 wt.% to 4 wt.% compared to only 70% rise when the solids content was increased from 1.5 wt.% to 6 wt.% for the 1:2 HTOCN/EEG cryogels. The drop in the adsorption capacity enhancement of the 1:2 HTOOCN/EEG cryogels was attributed to the higher extent of EEG sheets aggregation at higher EEG contents. The electrochemical regeneration studies confirmed the ability to oxidize the methylene blue adsorbed onto the cryogels with minimal changes in the cryogels’ adsorption capacities after multiple regeneration cycles. The cryogel made of 1:1 HTOCN/EEG with 1 wt.% solids content gel was tested for 18 adsorption-electrochemical regeneration cycles with no observable mass loss and retained adsorption capacity confirming the feasibility of the proposed approach for developing adsorbents with long-term stability.
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Keywords
Materials Science, Cryogels, Electrochemistry, Adsorption.
Citation
Abuhatab, S. S. (2022). Biodegradable Cryogels for Adsorption and Electrochemical Oxidation of Organic Dyes (Master thesis). University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca .