CO2-Responsive Graft Modified Chitosan for Heavy Metal (Nickel) Recovery

Abstract

Abstract:Chitosan was chemically functionalized with poly(diethylaminoethyl methacrylate) (PDEAEMA) using a grafting to approach to produce a CO 2 -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 CO 2 -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.

Chitosan–Zinc(II) Complexes as a Bio-Sorbent for the Adsorptive Abatement of Phosphate: Mechanism of Complexation and Assessment of Adsorption Performance

“…Chitosan (CTS) is a biopolymer emerging in the adsorption process and is derived from chitin, the second most plentiful natural polymer after cellulose [ 13 , 14 , 15 ]. It has many advantages as a bio-sorbent, such as good adsorption capacity, biodegradability, and biocompatibility [ 15 , 16 , 17 , 18 , 19 ].…”

History of nitroxide mediated polymerization in Canada

“…[ 166 ] The Cunningham group has recently made extensive contributions towards using NMP to make hybrid materials with chitosan, cellulose, and starch, using both grafting‐from (where the initiator is grafted onto the carbohydrate backbone and used to polymerize from the site on the backbone) and grafting‐to (where a pre‐made polymer is linked to a complementary functionality on the backbone) approaches. [ 167,168 ] The first reports produced from this group involved the use of chitosan, [ 169–173 ] where it was functionalized with the BlocBuilder initiator by first linking a methacrylic acid to the amine groups present on the chitosan backbone and then using intermolecular radical addition (IRA) to attach the initiator. Subsequently, various polymers were grown from the sites to impart different solubility or add some functionality such as thermoresponsiveness or complexing behaviour.…”

“…For example, poly(oligo(ethylene glycol) methacrylate) was grafted on chitosan for dye removal in aqueous solutions [ 172 ] while amino‐functional polymers were grafted onto chitosan to apply CO 2 ‐switchable surfaces for metal recovery. [ 173 ] Similar approaches were used when another poly(saccharide), nanocrystalline cellulose (NCC), was applied, as indicated below, for the grafting of MMA and MA onto the backbone (Figure 12). [ 174–178 ]…”

Isothermal Adsorption Properties for the Adsorption and Removal of Reactive Blue 221 Dye from Aqueous Solutions by Cross-Linked β-Chitosan Glycan as Acid-Resistant Adsorbent

“…At the same time, chitosan is also soluble in acidic media and cannot be used as an insoluble adsorbent. The removal of acidic dyes from acidic effluent could be realized by preparing chitosan with good adsorption performance [23] and stability in low-pH solutions via chemical grafting modifications [24]. A review of the literature shows that α-chitosan from crab and prawn shells is the most frequently used for chemical modification by grafting.…”