An improved technique for extraction of uranium from seawater

Uranium has a wide range of applications such as nuclear energy generation. Seawater has the most significant uranium reserve as compared to terrestrial ores thus its appropriate extraction will ensure a constant supply of the nuclear power for the generations to come. Currently, several methods are available for the extraction of the seawater uranium including floatation, membrane dialysis, ionic exchange, sorption among others. The method to be used however depends on its operation requirements, cost, and reliability. Therefore, sorption method has been widely used. It involves the use of sorbents with large sorption capacity, good mechanical property and regenerability to ensure high uranium selectivity.

However, it is still difficult for the sorbents to overcome biofouling that occurs during the process of extracting seawater uranium. Biofouling occurs at the wetted surfaces that provides accumulation sites for algae, plants, animals or bacteria and usually involves a four-step process. At the initial stage, the microorganism coats the surface after which the bacterial cells settle on the coated surface. Microbial generated in the third stage results in rough surfaces thus capturing more larval forms and particles and eventually, the microorganisms outgrow on the various surfaces.

Considering the effects of biofouling on the uranium seawater extraction, sorbents having antifouling properties should be developed for the extraction processes. For instance, biofouling continuously reduces the sorption capacity hence preventing accessibility of the ligands and also leads to biocorrosion which reduces the reusability of the sorbents.

A group of researchers at Soochow University Professor Daoben Hua, Ms. Huijun Zhang, Ms. Lixia Zhang and Ms. Xiaoli Han in collaboration with Dr. Liangju Kuang from Purdue University and Professor Daoben Hua from Jiangsu Higher Education Institution proposed guanidine and amidoxime co-functionalized polypropylene nonwoven fabric for extracting the seawater uranium. This was in a bid of preventing the biofouling as the fabric has antifouling property. The authors prepared the functionalized fabric by the reactions of the GMA graft polymerization, amidoximation, and the open ring epoxy group. Finally, they investigated the parameters affecting antibacterial assay and uranium adsorption. Their work is published in the journal, Industrial and Engineering Chemistry Research.

The authors successfully observed that the polypropylene nonwoven fabric guanidine group was capable of killing bacteria as well as inhibiting the bacterial adhesion due to the hydrophilic function present. Coexisting ions had no effects on the uranium sorption and thus the equilibrium could be achieved within five hours at a pH of 8.0, a temperature of 298.15 K and capacity of 112 mg/g from Langmuir model. It could also be effectively regenerated at higher adsorption frequencies after five cycles.

The authors for the first time reported about a functionalized sorbent for seawater uranium extraction with antifouling properties. The guanidine groups are used to improve on the selectivity and antifouling performance, thereby accelerating the rate of uranium sorption. Additionally, polypropylene nonwoven fabrics are vital for effective adsorption of the uranium from the seawater. The study will, therefore, advance the extraction of uranium from the seawater by replacing the other convention extraction methods currently used.