Development of a Highly Efficient Amidoxime Functionalized Cellulose Adsorbent for Enhanced Separation of Vanadium using Acetate as a Complexing Agent
Date
2020-12-16
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Abstract
Vanadium is a strategic alloying metal that is used in high strength steel for varying applications, from high performance tools to earthquake resistant rebar. However, most vanadium is produced as a by-product of iron ore mining and this cannot meet increasing demand. Several new vanadium deposits, such as stone coal or carbonaceous shales, are suitable for low-cost hydrometallurgical extraction, which involves dissolving metal ions into solution for recovery. Currently, purifying vanadium ions from other dissolved metals is done with solvent extraction, which utilizes organic solvents and toxic extractants. In this work, a cellulose-based adsorbent material was developed that demonstrates high selectivity towards vanadium. Cellulose powder was functionalized with amidoxime functional groups via a simple two step heterogenous reaction, first adding nitrile groups to the surface followed by conversion to amidoxime. We developed a new hybrid approach for amidoxime functionalization on cellulose which uses fewer reagents under benign conditions, resulting in an adsorbent with high adsorption capacity for vanadium (70 mg g-1). Furthermore, by dissolving acetic acid as a complexing agent, the vanadium adsorption capacity of the adsorbent was found to increase by over a factor of 4, from 70 mg g-1 to 330 mg g-1. Additionally, the inclusion of acetate enhanced the selectivity towards vanadium over chromium, increasing from 2.0 ± 0.5 to 7.0 ± 0.2 at an acetate concentration of 0.5 M. When in competition with simple divalent metal ions such as copper or nickel, the adsorbent had a selectivity towards vanadium of more than 150, the lower bound of detectability. Following adsorption, vanadium was found to be easily recovered through elution with dilute sulfuric acid (0.5 M) which makes the adsorbent promising for future applications. The applicability of amidoxime functionalized cellulose was further demonstrated through the synthesis and utilization of functionalized cellulose beads. Using the insights gained from functionalizing cellulose fibers, cellulose beads were functionalized to yield a similar adsorption capacity per gram of cellulose while at the same time providing mechanical structure for use in an adsorption column. From adsorption column experiments, the kinetic performance was analyzed, and future optimizations were proposed.
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Keywords
Adsorption, Cellulose, Vanadium, Amidoxime, Complexing, Acetic Acid, Selective
Citation
Bakuska, D. C. R. (2020). Development of a Highly Efficient Amidoxime Functionalized Cellulose Adsorbent for Enhanced Separation of Vanadium using Acetate as a Complexing Agent (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.