A Greener Amidoximation Process for Fabrication of Popular Uranium Complexing Fiber Using Water as the Single Solvent

A mixed water-organic solvent used for amidoximation increased the production cost of an amidoxime-based polymer sorbent and was not environmentally friendly as well. In this work, the amidoximation of an ultrahigh molecular weight polyethylene fiber co-grafted with acrylonitrile and methacrylic acid was carried out in aqueous solution without the use of an organic solvent. The effects of amidoximation parameters including NH2OH concentration, temperature, time, and various solvents on the uranium adsorption performances in both uranium-spiked brine and simulated seawater were investigated. Results indicated that the optimal amidoximation parameters were 5% (w/v) NH2OH, 80 degrees C, and 24 h. The uranium adsorption capacities of the sorbents amidoximated in aqueous solution were comparable with those of sorbents amidoximated in the various mixed water-organic solvents. Moreover, in comparison with both acidic (pH similar to 3) and alkalic (pH similar to 11) aqueous solution, the sorbent amidoximated in neutral (pH similar to 7) NH2OH aqueous solution achieved higher uranium adsorption capacities in both uranium-spiked brine (112.4 mg/g) and simulated seawater (7.4 mg/g). Additionally, potassium hydroxide (KOH) treatment was a necessary process and indeed significantly increased the uranium adsorption capacity.

Automated summary

This study explored the amidoximation of polymer sorbents in aqueous solution, which proved to be cost-effective, environmentally friendly, and achieved comparable uranium adsorption capacities compared to using mixed water-organic solvents. Additionally, a neutral NH2OH aqueous solution was found to significantly enhance the uranium adsorption capacities, and potassium hydroxide treatment was crucial for increased adsorption.