Abstract
Chitosan was chemically functionalized with poly(diethylaminoethyl methacrylate) (PDEAEMA) using a grafting to approach to produce a CO2-responsive material for adsorbing metals from wastewater streams. A need for improved economical and greener approaches to recover heavy metals from wastewater streams exists due to increasing resource scarcity. Chitosan is currently used as an adsorbent for heavy metals but suffers from some properties that can be disadvantageous to its effectiveness; it is difficult to effectively disperse in water (which limits available surface area) and to regenerate. We set out to improve its effectiveness by grafting CO2-responsive tertiary amine containing polymers onto the chitosan backbone, with the goals of preparing and assessing a new type of adsorbent based on a novel concept; using carbon dioxide switchable polymers to enhance the performance of chitosan. PDEAEMA chains prepared by nitroxide-mediated polymerization were grafted onto chitosan functionalized with glycidyl methacrylate. In carbonated water, the grafted chitosan displayed improved dispersibility and exhibited a Ni(II) adsorption capacity higher than several other chemically functionalized chitosan variants reported in the literature with the regenerated material having a higher capacity than all physical and chemical derivatives reported in the literature. The results of this study validate the continued development of this material for applications in heavy metal removal and recovery from wastewater streams.
Highlights
Chitin (poly(2-acetamido-2-deoxy-β-D-glucose)) is the second most abundant natural polymer in the world, second only to cellulose
(CTS–g–glycidyl methacrylate (GMA)–PDEAMEA), to improve its effectiveness by grafting CO2 -responsive tertiary amine containing polymers onto the chitosan backbone, with the goals of preparing and assessing a new type of adsorbent based on a novel concept; using carbon dioxide switchable polymers to enhance the performance of chitosan, The longer term objective is development of a material that allows for the recovery of the adsorbed metal and regeneration of the material without the use of aggressive acid or caustic agents
CTS–g–GMA was synthesized by reacting the GMA epoxide with the primary alcohol from
Summary
Chitin (poly(2-acetamido-2-deoxy-β-D-glucose)) is the second most abundant natural polymer in the world, second only to cellulose This material is produced by a vast number of living organisms, typically as a main component of arthropod exoskeletons [1]. Many countries across the world have large unexploited sources of crustacean shells that are appropriate for manufacturing chitin and chitosan Both biopolymers exhibit excellent biocompatibility, biodegradation in the human body, and non-toxicity making them attractive over synthetic alternatives [2]. These properties allow chitosan to find applications in the water and wastewater treatment, agriculture, biopharmaceuticals, cosmetics and toiletries, and the food and beverages industries [1]. Compared to cellulose and chitin, the ability to dissolve chitosan under aqueous acidic conditions allows for somewhat easier functionalization; Polymers 2017, 9, 394; doi:10.3390/polym9090394 www.mdpi.com/journal/polymers
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