Extracting Uranium from Seawater: Promising AI Series Adsorbents

Abstract

A new series of adsorbents (AI10 through AI17) were successfully developed at ORNL by radiation induced graft polymerization (RIGP) of acrylonitrile (AN) and vinylphosphonic acid (VPA) (at different mole to mole ratios) onto high surface area polyethylene fiber, with high degrees of grafting (DOG) varying from 110 to 300%. The grafted nitrile groups were converted to amidoxime groups by reaction with 5 wt % hydroxylamine at 80 °C for 72 h. The amidoximated adsorbents were then conditioned with 0.44 M KOH at 80 °C followed by screening at ORNL with prescreening brine spiked with 8 ppm uranium. Uranium adsorption capacities in prescreening ranged from 171 to 187 g-U/kg-ads irrespective of percent DOG. The performance of the adsorbents with respect to uranium adsorption in natural seawater was also investigated using flow-through-column testing at the Pacific Northwest National Laboratory (PNNL). Three hours of KOH conditioning led to higher uranium uptake than 1 h of conditioning. The adsorbent AI11, containing AN and VPA at the mole ratio of 3.52, emerged as the potential candidate for the highest uranium adsorption (3.35 g-U/kg-ads.) after 56 days of exposure in seawater flow-through-columns. The rate of vanadium adsorption over uranium linearly increased throughout the 56 days of exposure. The total mass of vanadium uptake was ∼5 times greater than uranium after 56 days.

Significantly Enhanced Uranium Extraction from Seawater with Mass Produced Fully Amidoximated Nanofiber Adsorbent

“…[3,[20][21][22][23][24][25] However, in this study, we found that 10 × 10 −3 m NaOH solution is enough to "active" the imide dioxime and/or amidoxime groups sufficiently. In most of the previous studies, 0.44 m NaOH (or KOH) solution was generally used for the alkaline treatment of adsorbent fibers prepared by RIGP or ATRP from PE trunk fibers.…”

“…NH 2 OH·HCl (12 g) was completely dissolved into DMF (100 mL), NaOH (6.9 g) was added to the solution and mixed with vigorous magnetic stirring for 2 h. After that, PAN powder (10 g) was added to the solution, the mixture was stirred for another 30 min at Adv. [18,[20][21][22][23][24]32] room temperature, then transferred to an oil bath, and kept at 80 °C for 12 h with continuous mechanical stirring. 2018, 8, 1802607 Figure 5.…”

“…); C 0 and C t are the initial and final concentrations of uranium (mg L −1 ) at each time point; V is the volume of the solution (L) and m is the mass of the PIDO NFs (g). For the adsorption isotherm study, a series of uranium spiked seawater with different initial concentrations of uranium (1,5,10,20,40,80, and 160 ppm) were contacted with 15 mg of alkaline conditioned PIDO NF mat following a similar procedure as described above. Each set of experiments was conducted three times and the average values were used for calculation.…”

“…Great efforts have been made to develop clean energy as alternatives to fossil fuels. [19][20][21][22][23][24][25][26][27] Very recently, Cui and co-workers reported the application of an amidoxime-functionalized electrode in a half-wave rectified alternating current electrochemical (HW-ACE) method for the extraction of uranium from seawater. [3] With DOE direction, the uranium uptake capacity of fiber adsorbents in natural seawater has more than tripled in five years.…”

Fit-for-purpose block polymer membranes molecularly engineered for water treatment

“…For example, amidoxime binding chemistries for the targeted separation of uranium from seawater have been identified, but current substrates result in problematic low uptake capacities. 138,139 The block polymer platform lends itself well to such instances due to its structural characteristics and easily modified chemical properties. These features could, likewise, improve the separation performance of membranes lined with phosphate-chelating agents for the recovery of phosphorus from wastewater streams.…”