Direct uranium recovery from brine concentrate using amidoxime adsorbents for possible future energy source

Abstract

Summary Recovery of uranium from concentrated brine rejection from a small seawater reverse osmosis plant in Thailand using four types of the amidoxime adsorbents was experimentally performed. Adsorbents were directly submerged in continuously flowing discharged brine concentrate. Studied adsorbents were amidoximated polymer gel prepared from gamma irradiation, amidoximated polymer gel prepared from UV radiation curing, amidoximated polyacrylonitrile fibers, and chromic‐acid‐treated low‐density polyethylene fibers grafted with amidoxime functional group using gamma radiation. Uranium concentration in brine concentrate and input seawater was analyzed to be 4.8 and 3.1 ppb, respectively. Gel adsorbent synthesized by gamma irradiation exhibited the highest uranium loading capacity of 1.39 mg/g‐ad with 20 000 L/h rejected brine flow‐rate after 6 weeks of soaking. The estimated uranium recovery cost is 406.81 USD/kg uranium. If the adsorption capacity was increased to 2 mg/g‐ad, the projected cost was reduced to 338.95 USD/kg. Under this land‐based recovery scheme, no work is performed in an open ocean environment, thus, ensuring safety and reducing cost and time, especially the costs associated with ships, personnel, and diesel fuel to bring the materials to the ocean and back to the shore. The present study demonstrates that direct uranium recovery from discharged brine concentrate is possible using amidoxime‐based adsorbents developed to study uranium extraction from natural seawater. This should pave the way for further experimental studies in larger seawater reverse osmosis (SWRO) plants for the possible future energy source. A proposed large‐scale, yet very simple, deployment strategy at a hypothetical SWRO plant is also presented. Novelty statement Successful uranium adsorption by directly submerging adsorbents in continuously flowing discharged brine concentrate from seawater reverse osmosis plant Mooring and recovery costs largely eliminated because of land‐based deployment Highest uranium uptake capacity of 1.39 mg/g adsorbent after 6 weeks of soaking

Binding Study of Vanadium and Uranium Complexes with Amidoxime Ligands at different pH

“…Addition of vanadium(V) to open-chain glutardiamidoxime, the 1 H NMR and 13 C NMR signals, for CH 2 's of glutardiamidoxime remain at the same position as that of free glutardiamidoxime without any vanadium. This observation suggests that openchain glutardiamidoxime does not react with vanadium(V).…”

“…The 1 H NMR peaks for free glutarimidedioxime at ∼ 1.9 ppm, and ∼ 2.5 ppm, and peaks for complexed glutarimidedioxime, at ∼ 3.0 ppm and ∼ 2.2 ppm were observed. The 1 H NMR peaks were correlated with 13 C NMR peaks for free glutarimidedioxime at 19 ppm and 25 ppm, and for complexed glutarimidedioxime at 18 ppm and 22 ppm.…”

“…After a minimum of 4-7 days, glutardiamidoxime was completely complexed with UO 2 glutardiamidoxime, complexation was observed. Three different 13 C NMR signals were observed for three non-equivalent carbons, À CH 2 À CH 2 À CH 2 À , of open-chain glutardiamidoxime because three CH 2 's become non-equivalent upon complexation with UO 2 + 2 (Figure 11b). The signal for complexed quaternary carbon belonging to C(NH 2 )=NOH was not observed.…”

“…[3][4] Amidoxime-based polymer adsorbents have been shown to be most effective material for sequestering uranium from seawater. [5][6][7][8][9][10][11][12][13][14][15][16] Vanadium is a major competing element for uranium adsorption from seawater using amidoxime-based adsorbents. [17][18][19][20] Vanadium adsorption is much greater than uranium from seawater utilizing amidoxime-based adsorbents.…”

“…The total amount of uranium present in sea water is around 4.5 billion metric tons [3–4] . Amidoxime‐based polymer adsorbents have been shown to be most effective material for sequestering uranium from seawater [5–16] . Vanadium is a major competing element for uranium adsorption from seawater using amidoxime‐based adsorbents [17–20] .…”