Novel poly(imide dioxime) sorbents: Development and testing for enhanced extraction of uranium from natural seawater

Abstract

A new series of amidoxime-based polymer adsorbents were synthesized at the Oak Ridge National Laboratory (ORNL) by electron beam induced grafting of acrylonitrile and itaconic acid onto polyethylene fiber. Hydroxylamine derivatives of poly(acrylonitrile) (PAN) moiety are demonstrated to possess two kinds of functional groups: open-chain amidoxime and cyclic imide dioxime. The open-chain amidoxime is shown to convert to imide dioxime on heat treatment in the presence of an aprotic solvent, like dimethylsulfoxide (DMSO). The formation of amidoxime and imide dioxime was confirmed by 13 C CP-MAS spectra. The adsorbents were evaluated for uranium adsorption efficiency at ORNL with simulated seawater spiked with 8 ppm uranium and 5 gallon seawater in a batch reactor, and in flow-through columns with natural seawater at the Marine Science Laboratory (MSL) of Pacific Northwest National Laboratory (PNNL) at Sequim Bay, WA. The DMSO-heat-treated sorbents adsorbed uranium as high as 4.48 g-U/Kg-ads. from seawater. Experimental evidence is presented that the poly(imide dioxime) is primarily responsible for enhanced uranium adsorption capacity from natural seawater. The conjugated system in the imide dioxime ligand possesses increased electron donation ability, which is believed to significantly enhance the uranyl coordination in seawater.

Origin of the unusually strong and selective binding of vanadium by polyamidoximes in seawater

“…Previous experimental studies indicate that conversion of polyacrylonitrile to polyamidoxime simultaneously generates cyclic imide-dioxime and open-chain amidoxime functionalities (Fig. 1c ) 13 and the relative yields of these two functional groups depend strongly on the synthesis conditions 14 . Since the aliphatic carboxylic acid comonomers are weak complexants for vanadium ions 15 and primarily increase fiber hydrophilicity 16 , our investigations focused exclusively on binding by the two representative small molecule analogs: glutaroimide-dioxime (H 3 IDO) and acetamidoxime (HAO).…”

Investigations Into the Reusability of Amidoxime-Based Polymeric Uranium Adsorbents

“…Several formulations (AI8, AF8, AF1, AF1-DMSO) of amidoxime-based, high-surface area polyethylene fibrous braids were prepared by Chris Janke, Richard Mayes, and Sadananda Das at Oak Ridge National Laboratory (ORNL) using the radiation-induced graft polymerization (RIGP) method (Kim et al, 2013(Kim et al, , 2014Janke et al, 2013;Das et al, 2016a;Das et al, 2016b;Das et al, 2016c). The RIGP method involves four processing steps: (1) electron beam irradiation of high surface area polyethylene fibers, (2) co-grafting polymerizable monomers containing nitrile groups and hydrophilic groups to form grafted side chains throughout the fiber,…”

Adsorption capacity of kelp-like electrospun nanofibers immobilized with bayberry tannin for uranium(vi) extraction from seawater

“…Uranium(VI), which plays an important role in the development of the nuclear industry, mainly exists in two forms in nature: deposits in terrestrial ores and in seawater. 1,2 Uranium resources from terrestrial ores are limited, so it is desired to extract uranium from seawater, in which the quantity of uranium is around 4.5 billion tons. 3 To date, lots of technologies have emerged for the extraction of uranium, such as solvent extraction, 4 chemical precipitation, 5 ion-exchange, 6 and adsorption.…”