| Uranium is a key basic resource of the nuclear power industry,and there is abundant uranium resource exist in the seawater,In order to meet people's growing demand for nuclear power,there is an urgent need to extract uranium resources from seawater.Among many existing materials for uranium extraction from seawater,the extraction of uranium by using amidoxime group-based adsorbents demonstrate high practical application potential,due to its'relatively high efficiency,high selectivity,and high affinity to the uranyl.Thus,the development of new adsorbent that can fully display the amidoxime functional group is expected to promote the practical application of the technology of uranium extraction from seawater.Due to the high specific surface area,high mechanical strength,and low cost of achievement,several natural ore nanomaterials are used in remediation of environmental heavy metal contamination.In this study,by combination utilizing of the the excellent properties of the natural ore nanomaterials and amidoxime functional group,two adsorbents,including the montmorillonite composited porous polypropylene amidoxime nanofiber and the dual-surface amidoximated halloysite nanotube,are fabricated for uranium extraction from natural seawater.By using the water-swelling property of montmorillonite,montmorillonite was used as a pore-forming agent and used in prepare of porous polypropylene amidoxime nanofiber?SMON-PAO?through solution blow spinning technology.Compared with the optimal p H 7.0 of polypropylene amidoxime?PAO?nanofiber,the optimal p H of SMON-PAO fiber increased to p H 8.0,which was near the p H of natural seawater.This property of the adsorbent would benefit the application of the SMON-PAO in seawater environment.The specific surface area of SMON-PAO was 95.72 m2g-1,which was much higher than that of the PAO fibers.The hydrophilic test of SMON-PAO was carried out and the results showed that the fiber maintained excellent hydrophilic property,and the contact angle of the fiber reduced to 0°within0.08 s.These properties of SMON-PAO adsorbent were attributing to the high hydrophilicity,positive surface charge of montmorillonite,and the high specific surface area of porous fibers.After being treated by alkali,the saturation adsorption capacity of SMON-PAO reached 1089.36 mg g-1in the uranium spiked simulated seawater?p H=8?with uranium concentration of 8 ppm within 30 hours.In natural seawater,after a field test of 56 days,the SMON-PAO nanofiber archived a high uranium extraction capacity of 9.59±0.64 mg g-1,indicated that SMON-PAO fiber is an potential adsorbent for practical uranium extraction from natural seawater.Inspired by the hollow structure of halloysite,amidoxime groups were chemical cross-linked onto the dual-surface of the halloysite nanotube to fabricate the dual-surface amidoximated halloysite nanotube adsorbent?AO-HNTs?.The concentration analysis of the contents of amidoxime group in AO-HNTs showed that the amidoxime group maintained a concentration of was 3.57 mmol g-1.The saturation uranium extraction capacity of AO-HNTs reached 456.24 mg g-1in the stimulated seawater with uranium concentration of 32 ppm with 13 hours.In natural seawater,AO-HNTs realized a uranium extraction capacity of 5.70 mg g-1within a short field test of 5 days and a uranium extraction capacity of 9.01 mg g-1within a field test of 30 days,which is much shorter than that of the amidoxime polymer fiber adsorbent with saturation uranium extraction time of several months.Due to the low cost of archievement and the high chemical stability,the utilization of AO-HNTs for uranium extraction would significantly reduce the economic cost for uranium extraction from seawater.In summary,the finding of this study revealed that the utilization of natural ore nanomaterials would significantly benefit the capacity for uranium extraction,as well reduced the economic cost and time consumption for uranium extraction.The developed adsorbents showed high potential for being used in practical uranium extraction from natural seawater. |
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