Reduction of uranium by Desulfovibrio desulfuricans in high sulfate and nitrate containing solutions

Biological reduction of uranium has been found to be important in the formation of iron and uranium ore deposits in anaerobic sediments. This discovery forms the basis of a new treatment technology that may be capable of selectively removing uranium from wastewaters. This study evaluated the potential for biological removal of uranium in surrogate solutions containing constituents similar to those found in actual wastewaters. Batch laboratory experiments were performed to determine the effect of high concentrations of sulfate and nitrate on the removal of uranium by D. desulfuricans. The experiments were performed with sulfate concentrations up to 10,000 mg/L, nitrate concentrations up to 50,000 mg/L, and with uranium concentrations at 100 mg/L. All of the experiments were run in a bicarbonate solution with lactic acid as the carbon source. The reactors were sampled by filtering through a 0.2 micron filter. The filtrate was stored in a 4°C cooler until it was analyzed. The samples were analyzed for uranium, sulfate, and/or nitrate as required. Combined nitrate/sulfate solutions were tested for any significant changes in the rate of uranium removal. In test reactors containing 100 mg/L uranium and \u3c5,000 mg/L sulfate, uranium was removed to \u3c0.1 mg/L in approximately one day. Results of a 10,000 mg/L sulfate solution experiment demonstrated a slight drop in the rate of uranium removal. A more significant decline in the rate of removal was observed in all of the sulfate reactors containing lower initial concentration of uranium. In test reactors containing \u3c10,000 mg/L nitrates, uranium was removed to \u3c0.1 mg/L within one day. At 50,000 mg/L nitrate, uranium removal occurred more slowly. In the combined nitrate/sulfate solutions, the D. desulfuricans removed uranium from 100 mg/L to \u3c0.1 mg/L within one day in the reactors containing \u3c5,000 mg/L nitrate. In the reactors containing 50,000 mg/L nitrate, uranium removal to \u3c1 mg/L occurred over 10 days. These results were independent of the sulfate concentrations. Possible explanations for the decline in the rates of uranium removal include competitive interference between the uranyl and sulfate ions, sodium inhibition, and ionic strength inhibition. A computer model was utilized to identify the potential uranium species that would be present in the test solutions. These data were compared to data gathered for actual nitrate-containing wastes. Modeling of waste indicates this stream may not be suitable for biological uranium removal under current conditions. The model predicted most of the waste streams would have very little soluble uranium, if any. The phosphate concentration in these wastewaters were relatively small; however, it seems to have sufficient affinity to complex with uranium and precipitate. If, however, the wastewater does not contain phosphate nor significant quantities of calcium, it may be possible to selectively remove the uranium from the wastewater using D. desulfuricans

IMOBILISASI ZEOLIT BEKAS PENYERAP LIMBAH RAFINAT DARI PRODUKSI RADIOISOTOP MOLIBDENUM-99 DENGAN POLIMER

Rafinat waste that produced by Instalation of Radioisotop Production is contained uranium. The research of uranium sorption by zeolite Alumino Silico Phosphate (ASP) and selected of best waste loading for immobilisation of saturated zeolite uranium used resin epoxy has been done. Uranium used is a simulation waste from uranyl nitrat hexahydrat which has 50 ppm in concentration. Zeolite ASP was made by mixing pure zeolite with Ammonium Dihydrogen Phosphate (ADHP). This research was done to variate the factor that influence the sorption process. Which are composition of zeolite ASP,retention time, and pH. The result of selected variable will be used for making saturated zeolite uranium will be immobilized with epoxy resin with variation of waste loading. Optimum condition of uranium sorption reached on zeolite ASP 1:1 with pH 7 and retention time for 12 minutes with uranium removal efficiency 51,1 %. Base on density, compressive strenght, and leaching rate ,the best result for polymer-waste block is on 20 % waste loading. In that condition the density for polymer waste block is 1,0538 gram/cm3 , the compreesive strenght 19,36 kN/cm3 and the leaching rate is not detected. Key word: Sorption, zeolite ASP, waste loading, epoxy resi

Functionalization of chitosan with 3,4-dihydroxybenzoic acid for the adsorption/collection of uranium in water samples and its determination by inductively coupled plasma-mass spectrometry

A chitosan resin derivatized with 3,4-dihydroxybenzoic acid moiety (CCTS-DHBA resin) was newly synthesized for the collection/concentration of trace uranium by using cross-linked chitosan (CCTS) as base material, and the adsorption behavior of uranium as well as 60 elements on the resin was examined by passing the sample solutions through a mini-column packed with the resin. After the elution of the collected elements on the resin with 1M HNO3, the eluates were measured by inductively coupled plasma-mass spectrometry (ICP-MS). The CCTS-DHBA resin can adsorb several metal cations and several oxoanionic elements at appropriate pH. Among these metal ions, uranium shows an excellent adsorption behavior on this resin. Uranium as UO22+ species can be adsorbed on the resin by chelating mechanism with adsorption capacity of 330 mg g(-1) resin. Through the column treatment, the complete removal of large amounts of alkali and alkaline earth matrices without any loss of adsorption efficiency over prolonged usage were achieved with this resin. The CCTS-DHBA resin was applied to the adsorption/collection of uranium in tap water, river water and seawater samples with satisfactory results. The validation of the proposed method was carried out by analyzing uranium in the standard reference materials of SLRS-4, CASS-4, and NASS-5 after passing through the CCTS-DHBA resin, and the results showed good agreement with the certified values

Investigating the mechanism of Uranium removal by zerovalent iron

Zerovalent iron (ZVI) has been proposed as a reactive material in permeable in situ walls for groundwater contaminated by metal pollutants. For such pollutants that interact with corrosion products, the determination of the actual mechanism of their removal is very important to predict their stability in the long term. From a study of the effects of pyrite (FeS2) and manganese nodules (MnO2) on the uranium removal potential of a selected ZVI material, a test methodology (FeS2MnO2 method) is suggested to follow the pathway of contaminant removal by ZVI materials. An interpretation of the removal potential of ZVI for uranium in the presence of both additives corroborates coprecipitation with iron corrosion products as the initial removal mechanism for uranium.Keywords: iron, redox reactions, uranium, water treatmentresearc

Uranium Removal from Groundwater and Wastewater Using Clay-Supported Nanoscale Zero-Valent Iron

The peculiarities of sorption removal of uranium (VI) compounds from the surface and mineralized groundwater using clay-supported nanoscale zero-valent iron (nZVI) composite materials are studied. Representatives of the main structural types of clay minerals are taken as clays: kaolinite (Kt), montmorillonite (MMT) and palygorskite (Pg). It was found that the obtained samples of composite sorbents have much better sorption properties for the removal of uranium from surface and mineralized waters compared to natural clays and nZVI.It is shown that in mineralized waters uranium (VI) is mainly in anionic form, namely in the form of carbonate complexes, which are practically not extracted by pure clays. According to the efficiency of removal of uranium compounds from surface and mineralized waters, composite sorbents form a sequence: montmorillonite-nZVI > palygorskite-nZVI > kaolinite-nZVI, which corresponds to a decrease in the specific surface area of the pristine clay minerals

Use of Boron Compounds to Precipitate Uranium from Water

A method is provided for removing uranium from water. The method includes the mixing of a boron reagent with water contaminated with uranyl dication ions, leading to removal of the uranium from that water

Reclamation with Recovery of Radionuclides and Toxic Metals from Contaminated Materials, Soils, and Wastes

A process has been developed at Brookhaven National Laboratory (BNL) for the removal of metals and radionuclides from contaminated materials, soils, and waste sites. In this process, citric acid, a naturally occurring organic complexing agent, is used to extract metals such as Ba, Cd, Cr, Ni, Zn, and radionuclides Co, Sr, Th, and U from solid wastes by formation of water soluble, metal-citrate complexes. Citric acid forms different types of complexes with the transition metals and actinides, and may involve formation of a bidentate, tridentate, binuclear, or polynuclear complex species. The extract containing radionuclide/metal complex is then subjected to microbiological degradation followed by photochemical degradation under aerobic conditions. Several metal citrate complexes are biodegraded, and the metals are recovered in a concentrated form with the bacterial biomass. Uranium forms binuclear complex with citric acid and is not biodegraded. The supernatant containing uranium citrate complex is separated and upon exposure to light, undergoes rapid degradation resulting in the formation of an insoluble, stable polymeric form of uranium. Uranium is recovered as a precipitate (polyuranate) in a concentrated form for recycling or for appropriate disposal. This treatment process, unlike others which use caustic reagents, does not create additional hazardous wastes for disposal and causes little damage to soil which can then be returned to normal use

Four methods for determining the composition of trace radioactive surface contamination of low-radioactivity metal

Four methods for determining the composition of low-level uranium- and thorium-chain surface contamination are presented. One method is the observation of Cherenkov light production in water. In two additional methods a position-sensitive proportional counter surrounding the surface is used to make both a measurement of the energy spectrum of alpha particle emissions and also coincidence measurements to derive the thorium-chain content based on the presence of short-lived isotopes in that decay chain. The fourth method is a radiochemical technique in which the surface is eluted with a weak acid, the eluate is concentrated, added to liquid scintillator and assayed by recording beta-alpha coincidences. These methods were used to characterize two `hotspots' on the outer surface of one of the He-3 proportional counters in the Neutral Current Detection array of the Sudbury Neutrino Observatory experiment. The methods have similar sensitivities, of order tens of ng, to both thorium- and uranium-chain contamination.Comment: 22 pages, 19 figure

Removal of uranium from aqueous wastes using electrically charged carbon nanofibers

The presence of aqueous uranium wastes is a problem in the United States and their treatment/disposal is desirable. Treatment methods have been developed but result in concentration opposed to conversion to a disposable form. This technique involves recovery of uranium as a solid, providing an advantage over other methods. The technique utilizes carbon nanofibers as electrodes which successfully electrosorb uranium ions. Fibers with varying surface characteristics were evaluated in the removal process and all were determined to be equally and extremely effective. Various experimental parameters were evaluated including applied potential, pH, and flow rate. The critical applied potential at which significant removal is achieved is between -0.3 and -0.4 V. Decreasing pH hinders the electrosorption process while increasing it enhances the process. As expected, an increase in flow rates results in decreased removal. It was determined that cyclic loading/unloading increased fiber performance and a capacity of at least 5.45 guranium /gcarbon can be achieved. These results illustrate that this technique can be effectively implemented to solve current waste management problems