Extracting Uranium from Seawater: Promising AF Series Adsorbents

Abstract

A new family of high-surface-area polyethylene fiber adsorbents named the AF series was recently developed at the Oak Ridge National Laboratory (ORNL). The AF series adsorbents were synthesized by radiation-induced graft polymerization of acrylonitrile and itaconic acid (at different monomer/comonomer mol ratios) onto high surface area polyethylene fibers. The degree of grafting (%DOG) of AF series adsorbents was found to be 154−354%. The grafted nitrile groups were converted to amidoxime groups by treating with hydroxylamine. The amidoximated adsorbents were then conditioned with 0.44 M KOH at 80 °C followed by screening at ORNL with sodium-based synthetic aqueous solution, spiked with 8 ppm uranium. The uranium adsorption capacity in simulated seawater screening ranged from 170 to 200 g-U/kg-ads irrespective of %DOG. A monomer/comonomer molar ratio in the range of 7.57−10.14 seemed to be optimum for highest uranium loading capacity. Subsequently, the adsorbents were also tested with natural seawater at Pacific Northwest National Laboratory (PNNL) using flow-through column experiments to determine uranium loading capacity with varying KOH conditioning times at 80 °C. The highest adsorption capacity of AF1 measured after 56 days of marine testing was demonstrated as 3.9 g-U/kg-adsorbent and 3.2 g-U/kg-adsorbent for 1 and 3 h of KOH conditioning at 80 °C, respectively. Based on capacity values of several AF1 samples, it was observed that changing KOH conditioning from 1 to 3 h at 80 °C resulted in a 22−27% decrease in uranium adsorption capacity in seawater.

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

“…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.…”

“…In the last decades, researchers worldwide have tried various methods to recover uranium from seawater and aqueous solution, such as coprecipitation, [6] ion-exchange, [7] adsorption via porous organic polymers, [8,9] and organic-inorganic hybrid adsorbents. [3,18] Uranium extraction from seawater via fiber adsorption has recentlyThe oceans contain hundreds of times more uranium than terrestrial ores. [3,17] In the 1990s, Japan Atomic Energy Agency (JAEA) research teams had successfully captured over 1083 g of uranium directly from ocean by using nonwoven fabric adsorbent, firmly establishing the practicality of uranium recovery from the oceans in appreciable quantities.…”

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.…”

Uranium uptake with graphene oxide sponge prepared by facile EDTA-assisted hydrothermal process

“…As pH is greater than 6.0, U(VI) sorption decreases gradually. In alkaline solution, because of excess OH À ions presenting in the system, the uranyl ions are further hydrolyzed into negative species such as UO 2 (OH) 3 À , (UO 2 ) 3 (OH) 7 À , UO 2 (OH) 3 À , or the deposit form of UO 2 (OH) 2 [28]. 36 and 196.51 mg · g À1 at pH 6.0, respectively.…”

“…With the increasing interest in nuclear power industry, uranium is gradually released into environment from uranium milling activities, refining, and nuclear power plant accident contamination, making it a most common radionuclide contaminant in soils and groundwater [1]. Up to now, a number of techniques have been proved to be effective in treating uraniumcontaminated effluent including solvent extraction, membrane filtration, ion exchange, and adsorption [3,4]. Therefore, the removal of uranium from the waste liquid is of great concern.…”