Uranyl Solutions Research Articles

Photocatalytic Extraction of Uranium from Seawater Using Covalent Organic Framework Nanowires.

In the push to achieve net-zero emissions by 2050, nuclear power will play an essential role alongside renewable wind and solar power, and correspondingly global interest and investment in this well-established technology is accelerating. The uranium present in seawater could support nuclear power generation for centuries, but traditional adsorptive separation strategies have proven ineffective for the selective extraction of uranium from this vast resource. Here, we report the synthesis of nanowires of a triazine-linked two-dimensional covalent organic framework via a solvent modulation approach, which can be used to access nanowire external diameters ranging from 50 to 200 nm. The 100 nm nanowires are exceptionally promising for the capture of uranium(VI) via photocatalytic reduction. Under simulated sunlight and without the use of sacrificial agents, the nanowires achieve a uranium uptake of 10.9 g/g from a 100 ppm uranyl(VI) solution, which is the highest reported to date among materials studied for photo and electrocatalytic uranium capture. Significantly, these nanowires exhibit a uranium adsorption capacity of 34.5 mg/g after exposure to seawater under irradiation for 42 days, a record among all materials reported to date for uranium capture.

Electrochemical/computational analysis and the derivation of Pourbaix diagrams of redox-active structural and adsorbed species in uranyl peroxide clusters (U60)

Electrochemical analysis of U60 nanoclusters (Li40K20[UO2(O2)(OH)]60(H2O)214) and their natural analog, the mineral studtite (UO2)O2(H2O)2·(H2O)2, was carried out using cyclic voltammetry with a powder microelectrode setup. Voltammetric analysis was supplemented by ab initio quantum mechanical modeling to understand the mechanism, thermodynamics, and structural changes during redox transition (with a semi-quantitative kinetics evaluation). This research aims to better understand the redox behavior and transport of dissolved and structural (incorporated) uranyl units in the environment. Further analysis is performed to determine if redox switching of actinyl ions in clusters can be performed while leaving the cluster intact or at what redox transition it disintegrates. Quantum-mechanical calculations were applied to approximate electrochemical peak potential shifts and add them to standard reduction potentials to more accurately assign peaks to specific redox transitions between different species. These peak potentials are calculated from oxidation state-dependent binding energies between different uranyl species either within or adsorbed to U60. This theoretical approach incorporates extensive error cancellation and serves to predict electrochemical redox potentials and identify the reaction taking place. Voltammograms of U60 in electrolyte solutions exhibit kinetically-inhibited coupled redox peaks assigned to the U(VI)/U(V) transition of cluster structural uranyl units at −0.34 V (vs. standard hydrogen electrode), indicative of U60 reduction from UO22+ to UO2+. The U(V)/U(IV) transition at −0.71 V is assigned to the subsequent U60 reduction of UO2+ to UO20. A method of observing these transitions in situ using synchrotron x-ray absorption spectroscopy was explored. Voltammetry, modeling, and peak analysis indicate a kinetically-inhibited two-step, one-e- (per step) reduction of U60 from U(VI) to U(V) to U(IV). Voltammetry and x-ray absorption spectroscopy measurements performed before and after exhaustive cycling and the highly stable nature of U60 provide evidence that clusters typically do not break apart upon reduction. Voltammograms of U60 collected in varied uranyl solutions are indicative of UO22+ adsorption to the cluster surface and its subsequent reduction at +0.24 V (U(VI)/U(V)) and −0.05 V (U(V)/U(IV)). For uranyl solutions in electrolyte, the two-step, one-e- (per step) reduction of U60 is superseded by uranyl adsorption from solution to the electrode surface with subsequent reduction via U(V) disproportionation. This study represents the sole electrochemical investigation of U60 in the literature and only the second of any uranyl peroxide nanocluster. It is also one of the first to use quantum–mechanical approaches in combination with existing solution-based standard reduction potentials to calculate Pourbaix (EH-pH) diagrams for adsorbed and structural species.

Uranium biomineralization by immobilized Chryseobacterium sp. strain PMSZPI cells for efficient uranium removal

Uranium (U) contamination is hazardous to human health and the environment owing to its radiotoxicity and chemical toxicity and needs immediate attention. In this study, the immobilized biomass of Chryseobacterium sp. strain PMSZPI isolated from U enriched site, was investigated for U(VI) biomineralization in batch and column set-up. Under batch mode, the fresh or lyophilized cells successfully entrapped in calcium alginate beads demonstrated effectual U precipitation under acid and alkaline conditions. The maximum removal was detected at pH 7 wherein ∼98–99% of uranium was precipitated from 1 mM uranyl carbonate solution loading ∼350 mg U/g of biomass within 24 h in the presence of organic phosphate substrate. The resulting uranyl phosphate precipitates within immobilized biomass loaded beads were observed by SEM-EDX and TEM while the formation of U biomineral was confirmed by FTIR and XRD. Retention of phosphatase activity without any loss of uranium precipitation ability was observed for alginate beads with lyophilized biomass stored for 90 d at 4 °C. Continuous flow through experiment with PMSZPI biomass immobilized in polyacrylamide gel exhibited U loading of 0.8 g U/g of biomass at pH 7 using 1 l of 1 mM uranyl solution. This investigation established the feasibility for the application of immobilized PMSZPI biomass for field studies. Environmental implicationUranium contamination is currently a serious environmental concern owing to anthropogenic activities and needs immediate attention. We have developed here a biotechnological method for successful uranium removal using immobilized cells of a uranium tolerant environmental bacterium, Chryseobacterium sp. strain PMSZPI isolated from U ore deposit via phosphatase enzyme mediated uranium precipitation. The ability of immobilized PMSZPI cells to precipitate U(VI) as long-term stable U phosphates under environmental conditions relevant for contaminated waters containing high concentrations of U that exerts toxicity for biological systems is explored here. The long term stability of the immobilized biomass without compromising its U removal capacity shows the relevance of the bioremediation strategy for uranium contamination proposed in this work.

Highly efficient extraction of uranium(VI) from seawater by polyamidoxime/polyethyleneimine sponge

Extracting uranium from seawater is of great significance for ensuring the sustainable development of nuclear energy. This article designs a simple and mass-produced porous sponge polyamidoxime/polyethyleneimine (PAO/PEI) for uranium extraction from seawater. The prepared porous sponge has excellent flexibility and mechanical strength, which can withstand harsh marine environments. In a 50 mg/L uranyl solution, the maximum adsorption capacity of PAO/PEI is 666.67 mg/g. Moreover, PAO/PEI sponge exhibits excellent selectivity for uranium in competitive adsorption conditions. FTIR and XPS are used to explore the adsorption mechanism, and the results showed that the synergistic effect of amidoxime and amino groups enhanced the binding of uranium(VI). The adsorption capacity after 15 days of enrichment in 100L natural seawater is 9.79 mg/g, and the average rate is 0.653 mg/g/day. The results indicate that PAO/PEI porous sponge has broad application prospects in large-scale seawater uranium(VI) extraction.

Removal of radioactive material (Uranium-VI) from low level wastewaters and subsequent disposal of loaded biomass

The concentration of radioactive material i.e., Uranium, when disposed from nuclear reactor as low-level wastewater is under the limit value of 10 mg/l and concentration from mine tailing wastes is in the order of 10–100 mg/l. Biosorption is very cost-effective adsorption mechanism, discussed in this paper for removal Uranium (VI) from LLW using nonviable fungus called Ganoderma lucidum. Non-viable fungus has its advantage over viable fungus like for viable fungus one has to maintain temperature, pH and nutrient level. In this paper, the fungus called Ganoderma lucidum (GL) was used for sequestering uranium (VI) followed by studying their equilibrium and kinetics. Results show sorption rate is satisfactory, and data fitted a model of second order. Also, GL to be very effective biosorbent with 70 % of the total sequestration took place during the first 5 min for pure uranyl solution the corresponding specific uranium uptake rates being 0.106 mg/g-min at equilibrium concentration of 10 mg/L (Uranium VI) and pH maintained is 5. In this paper effect of competing co-ions were also studied and it is found out that effect of iron on uranium uptake is quite significant whereas the effect of other co-ions is at best marginal. Thus, biosorption by GL fungus is energy efficient and cost-effective method for removal of radioactive material from low level wastewater.

High-efficient uranium-ion adsorption on manganate nanoribbons

Manganate Na0.44MnO2 nanoribbons were synthesized by molten-salt method and the adsorption properties of the sample for radionuclide uranium were investigated. The adsorption experiment result shows that the removal rate of 0.10 g Na0.44MnO2 nanoribbons to 36 mg/L uranyl solution reaches 97 %, and the adsorption process reaches equilibrium in about 5 h. The adsorption isotherms of uranium ions on Na0.44MnO2 fitted well to the Langmuir model, corresponding to the maximum adsorption capacity of 203.27 mg/g. This work provides good candidates for the radionuclide-uranium adsorption.

Nanoemulsion assembly toward vaterite mesoporous CaCO3 for high-efficient uranium extraction from seawater

Uranium extraction from seawater is particularly significant and regarded as an indispensable strategy for satisfying the increasing demand for nuclear fuel owing to the high uranium reserves (about 4.5 billion tons) in seawater, while remains great challenges due to the low concentration, the interference of various cations and the complexity of the marine environment. Thus, developing a highly efficient adsorbent with high adsorption capacity, excellent selectivity, low cost, and facile synthesis method is significant and urgently required. Inorganic materials show many advantages in adsorption such as low cost, fast response, high stability, etc, while conventionally, have poor capacity and selectivity especially in real seawater. Herein, mesoporous CaCO3 (mCaCO3) with vaterite phase is synthesized by a facile nanoemulsion strategy and “ready-to-use” for uranium adsorption without functionalization and post treatment. Surfactant Pluronic F127 not only assembles into reverse micelles to form mesopores, but also stabilizes the active vaterite phase. The obtained mCaCO3 with high surface area (48.2 m2/g), interconnected mesopores (11 nm), and unique vaterite phase achieves highly efficient uranium adsorption with a maximum adsorption capacity of 850 ± 20 mg-U/g in uranium-spiked seawater and 6.5 ± 0.5 mg-U/g in 700 L of natural seawater for one week, as well as excellent selectivity, matching the state-of-the-art U adsorbents. After adsorption, mCaCO3-U is dissolved with a simple acid elution to obtain concentrated uranyl solution for purification, avoiding the disposal of adsorbents. To the best of our knowledge, this is the first case to report mesoporous CaCO3 for uranium adsorption from seawater with such a good performance. The facile synthesis, abundant raw materials and eco-friendly adsorption-desorption processes endow the mCaCO3 as a promising candidate for large-scale uranium extraction from seawater.

Effect of bi-functionalization silica micro beads on uranium adsorption from synthetic and washing pregnant uranyl solutions

Effect of bi-functionalization silica micro beads on uranium adsorption from synthetic and washing pregnant uranyl solutions

Chemical Modification of Combusted Coal Gangue for U(VI) Adsorption: Towards a Waste Control by Waste Strategy

Uranium mining waste causes serious radiation-related health and environmental problems. This has encouraged efforts toward U(VI) removal with low cost and high efficiency. Typical uranium adsorbents, such as polymers, geopolymers, zeolites, and MOFs, and their associated high costs limit their practical applications. In this regard, this work found that the natural combusted coal gangue (CCG) could be a potential precursor of cheap sorbents to eliminate U(VI). The removal efficiency was modulated by chemical activation under acid and alkaline conditions, obtaining HCG (CCG activated with HCl) and KCG (CCG activated with KOH), respectively. The detailed structural analysis uncovered that those natural mineral substances, including quartz and kaolinite, were the main components in CCG and HCG. One of the key findings was that kalsilite formed in KCG under a mild synthetic condition can conspicuous enhance the affinity towards U(VI). The best equilibrium adsorption capacity with KCG was observed to be 140 mg/g under pH 6 within 120 min, following a pseudo-second-order kinetic model. To understand the improved adsorption performance, an adsorption mechanism was proposed by evaluating the pH of uranyl solutions, adsorbent dosage, as well as contact time. Combining with the structural analysis, this revealed that the uranyl adsorption process was mainly governed by chemisorption. This study gave rise to a utilization approach for CCG to obtain cost-effective adsorbents and paved a novel way towards eliminating uranium by a waste control by waste strategy.

Influence of Alkaline Earth Metal Ions on Structures and Luminescent Properties of NamMnUO2(CO3)3(4-m-2n)- (M = Mg, Ca; m, n = 0-2): Time-Resolved Fluorescence Spectroscopy and Ab Initio Studies.

The luminescence spectra of triscarbonatouranyl complexes were determined by experimental and theoretical methods. Time-resolved laser-induced fluorescence spectroscopy was used to monitor spectra of uranyl and bicarbonate solutions at 0.1 mol kgw-1 ionic strength and pH ca. 8. The concentrations of Mg2+ and Ca2+ in the samples were chosen in order to vary the proportions of the alkaline earth ternary uranyl complexes MgUO2(CO3)32-, CaUO2(CO3)32-, and Ca2UO2(CO3)3. The luminescence spectrum of each complex was determined by decomposition in order to compare it with the simulated spectra of model structures NamMnUO2(CO3)3(4-m-2n)- (M = Mg, Ca; m, n = 0-2) obtained by quantum chemical methods. The density functional theory (DFT) and time-dependent (TD)-DFT methods were used with the PBE0 functional to optimize the structures in the ground and excited states, respectively, including relativistic effects at the spin-free level, and water solvent effects using a continuum polarizable conductor model. The changes in the structural parameters were quantified with respect to the nature and the amount of alkaline earth counterions to explain the luminescence spectra behavior. The first low-lying excited state was successfully computed, together with the vibrational harmonic frequencies. The DFT calculations confirmed that uranyl luminescence originates from electronic transitions from one of the four nonbonding 5f orbitals of uranium to an orbital that has a uranyl-σ (5f, 6d) character mixed with the 2p atomic orbitals of the carbonate oxygens. Additional single-point calculations using the more accurate TD-DFT/CAM-B3LYP allow one to determine the position of the luminescence "hot band" for each structure in the range 467-476 nm and compared fairly well with experimental reports at around 465 nm. The complete luminescence spectra were built from theoretical results with the corresponding assignment of the electronic transitions and vibronic modes involved, mainly the U-Oax stretching mode. The resulting calculated spectra showed a very good agreement with experimental band positions and band spacing attributed to MgUO2(CO3)32-, CaUO2(CO3)32-, and Ca2UO2(CO3)3. The evolution of luminescence intensities with the number of alkaline earth metal ions in the structure was also correctly reproduced.

Removal of uranium by immobilized biomass of a tropical marine yeast Yarrowia lipolytica

A marine yeast, Yarrowia lipolytica isolated from an oil polluted sea water and shown earlier to sequester dissolved uranium (U) at pH 7.5, was utilized in the present study for developing an immobilized-cell process for U removal from aqueous solutions under batch and continuous flow through systems. In batch system, optimum biosorption conditions for U removal were assessed by investigating the effects of biomass dose, initial U concentration, contact time and pH of solution using Y. lipolytica cells immobilized in calcium alginate beads. Appreciable uranium-binding capabilities over a wide pH range (3–9) were observed with the alginate beads bearing yeast cells. Out of Langmuir and Freundlich models employed for describing the sorption equilibrium data under batch mode, uranyl adsorption followed Langmuir approach with satisfactory correlation coefficient higher than 0.9. Uranyl adsorption kinetics by Y. lipolytica entrapped in alginate beads was best described by the pseudo-second-order model. While the environmental scanning electron microscopy established the immobilization and the uniform distribution of Y. lipolytica cells in the alginate beads, the Energy Dispersive X-ray spectroscopy analysis confirmed the deposition of U in the beads following their exposure to uranyl solution. Fixed bed flow-through column comprising of Y. lipolytica biomass immobilized in polyacrylamide matrix displayed high efficacy for continuous removal of uranium at pH 7.5 up to five adsorption-desorption cycles. Adsorbed U by immobilized cells could be significantly desorbed using 0.1 N HCl. Overall, our results present the superior efficiency of immobilized Y. lipolytica biomass for U removal using batch and regenerative approaches.

Physicochemical Behavior of Uranium and Lanthanum in the Presence of Abies religiosa Leaf Biomass

The biomass from Abies religiosa was conditioned and characterized. The adsorption kinetic data indicated sorbate-adsorbent interaction by chemical bonds. The maximum adsorption capacity of the biomass is four times higher for U(VI) (44.7 ± 0.3 mg g−1) than La(III) (12.7 ± 0.2 mg g−1). The pHeq tends to the point of zero charge of the biomass. These adsorption capacities decreased as both the biomass dosage and ionic strength increased. The adsorption is a spontaneous and exothermic process. Adsorption may be due to the bonding of the metal ions to hydroxyl and carbonyl groups of the biomass. The fluorescence spectra of the U(VI) biomass reveal indirectly the presence of uranyl ions and it suggests an energy transfer from the uranyl to the biomass forming a bond of ionic character. Moreover, the unusual fluorescence of the uranyl solutions after contact with the biomass indicates the coexistence of uranyl(V) with uranyl(VI).

Bis[2-(methacryloyloxy)ethyl] phosphate radiografted into track-etched PVDF for uranium (VI) determination by means of cathodic stripping voltammetry

We report the radiation grafting of bis[2-(methacryloyloxy)ethyl] phosphate (B2MP) through electron-beam onto PVDF films and through swift heavy ions (SHI) irradiations into the pores of track-etched PVDF membranes. Radiolytically produced radicals were studied using EPR. To adapt the radiation grafting protocol inside the nanopores of track-etched membranes, the electron-beam irradiated films at varying monomer concentrations, doses and solvent mixtures were first studied. It was found that track-etched membranes, even after 1 h of chemical treatment, do not require a post-etching irradiation to initiate free-radical polymerization of B2MP from remaining radiationinduced radicals. The presence of functional groups inside the nanopores of the membrane were examined using FTIR and XPS. After exposure of B2MP-g-PVDF membranes to a uranyl solution, XPS was also exploited to evidence of O2UO22+ trapping inside the membrane nanoporosity by tracking the presence of U 4f peak. The B2MP-g-PVDF membranes were converted into electrodes by depositing 35 nm of gold on each side through a mask. Detection of ppb concentrations (from 20 to 100 ppb) of uranyl by B2MP-g-PVDF membrane electrodes was demonstrated by means of square wave cathodic stripping voltammetry (SW-CSV). The limit of detection (LOD) was estimated to be 17 ppb (3σ−/ slope).

Photocatalytic reduction of uranyl: Effects of organic ligands and UV light wavelengths

Although previous studies demonstrate the photochemical reduction of uranyl (UO22+) in the presence of various organic compounds, the actual roles of organic molecules as ligands and electron donors during the photoreaction are poorly understood. In this study, photochemical reduction of uranyl is examined with respect to organic ligands as electron donors and complexing agents, the role of titanium oxide (TiO2) nanoparticles as a photocatalyst, and the influence of UV light irradiation with emission peaks in the UV-A, UV-B, and UV-C ranges. Organic compounds with different binding affinities to uranyl such as acetate, ethylenediaminetetracetate (EDTA), oxalate, and hydroquinone were selected. Uranyl solutions prepared with one organic compound in a 1:8 molar ratio were irradiated under anoxic and acidic conditions (O2

Enhanced sorption capacities for lead and uranium using titanium phosphates; sorption, kinetics, equilibrium studies and mechanism implication

The application of new synthesized titanium phosphates to the lead and uranium removal from acidic aqueous solutions (pH 2) was explored. Batch sorption experiments were carried out using lead- and uranyl solutions of concentration range 50–6000 and 50–4000 mg·L−1 respectively. The effect of pH, concentration, competing cations, temperature and reaction time on the adsorption equilibrium was investigated. The sorbents were examined by FTIR, XRD, XPS and SEM-EDS and characterized as mix salts while the formation of precipitates chloropyromorphite (Pb5(PO4)3Cl) and sodium-autunite (NaUO2PO4) after sorption was demonstrated. Typical sorption isotherms were constructed and modelled by the Langmuir, Freundlich and Temkin equations. The highest sorption capacity values (qmax: 2000 mg·g−1 Pb and 1250 mg·g−1 U) were observed for TiP3 which contains sodium in its structure. The kinetic data, obtained at 298, 308 and 323 K, obeyed a pseudo-second order equation and thermodynamic parameters were calculated. EPA Toxicity Characteristic Leaching Procedure and desorption experiments were performed in order to test the environmental compatibility of the sorbents. The results indicated that the sorption of Pb and U on titanium phosphates can be interpreted by a model combining adsorption and surface complexation toward surface precipitation.

The application of visible absorption spectroscopy to the analysis of uranium in aqueous solutions

Through assay analysis into an excess of 1M H2SO4 at fixed temperature a technique has been developed for uranium concentration analysis by visible absorption spectroscopy over an assay concentration range of 1.8–13.4mgU/g. Once implemented for a particular spectrophotometer and set of spectroscopic cells this technique promises to provide more rapid results than a classical method such as Davies-Gray (DG) titration analysis. While not as accurate and precise as the DG method, a comparative analysis study reveals that the spectroscopic method can analyze for uranium in well characterized uranyl(VI) solution samples to within 0.3% of the DG results. For unknown uranium solutions in which sample purity is less well defined agreement between the developed spectroscopic method and DG analysis is within 0.5%. The technique can also be used to detect the presence of impurities that impact the colorimetric analysis, as confirmed through the analysis of ruthenium contamination. Finally, extending the technique to other assay solution, 1M HNO3, HCl and Na2CO3, has also been shown to be viable. Of the four aqueous media the carbonate solution yields the largest molar absorptivity value at the most intensely absorbing band, with the least impact of temperature.

Reaction of ozone with uranium(IV) oxalate in water

Decomposition of aqueous suspensions of uranium(IV) oxalate under the action of an ozone–oxygen mixture was studied. The process occurs in two steps. In the first step, the U(IV) oxidation with the formation of oxalic acid uranyl solutions prevails. The second step involves decomposition of oxalate ions and hydrolysis of uranyl ions. An increase in temperature accelerates the transformation of uranium(IV) oxalate into uranium(VI) hydroxide compounds. In solutions containing KBr or UO2Br2, the following reaction occurs: O3 + Br– → O2 + BrO–. The arising hypobromite ions and hypobromous acid oxidize uranium(IV) oxalate extremely efficiently. The possible mechanism of ozonation of aqueous uranium(IV) oxalate suspensions is discussed.

Thorium-234 Electrodeposition Using Ionic and Aqueous Uranyl Solutions

Electrodeposition process of natural uranyl many has several deposit possibilities, since the process variables and uranium natural isotopes and secular equilibrium may induce the formation of several uranium compounds. One of these deposit possibilities is the strong beta-emitter thorium-234. The present work showed that pulsed polarization and 2-propanol natural uranyl solution (50 mM [U]) induced the formation of intense beta-emission in the samples, with activity beta-alpha ratio reaching levels of 300, which is much higher than the secular equilibrium ratio around 1. The natural decay of the deposited samples showed that the beta-emitter as most probable element to be thorium-234 within a pertinent regression exponential decay curve adjustment (R2=0.998) giving a typical experimentation value for half-life as 22.88 days. This value was found lower than the typical 24.10 days for thorium-234 (specific activity of 85.69x1013 Bq/g), probably due to activity contribution of uranium-235 daughter, thorium-231 (specific activity of 19.67x1015 Bq/g), which beta-decays having half-life of 25.6 h. Further experimentation with pulsed polarization of the cathode (0 to -15V; 12.5 Hz – duty time = 87.5% and process time varying until 3600s) also showed that thorium-234 depends on solution acidity, solution usage and deposition time. XRD spectra suggests that the deposit would be probably a combined structure of uranium-thorium hydride, which decomposes with time.

Extraction of UO22+ into Ionic Liquid Using TTA and TBP as Extractants

Thenoyltrifluoroacetone and Tributyl-phosphate have been used for extraction of UO22+ into Ionic Liquid 1-Butyl-3-methylimidazoliumbis(trifluoromethylsulfonyl)imide. Increasing acidity of uranyl solution from 0.01 to 3 mol L−1 HNO3 for TTA in IL, the distribution ratio (DU) and extraction efficiency (%E) both decreased. Further increment in acidity shows reversal of trend. Similar behavior is observed for TBP. With increasing concentration of TTA, %E increases stabilizing at 0.5 mol L−1 TTA. Adding methanol to TTA increased the DU due to active enolic formation. The developed kinetic model estimates the overall mass transfer coefficient (Ka) as 3.6 x 10−2 s−1. Synergistic effect has been observed for combination of TTA + TBP resulting in enhanced DU.

Thorium-234 Electrodeposition Using Ionic and Aqueous Uranyl Solutions

The isotope 234Th is daughter from 238U natural decay, with a half-life of 24.1 days. Then, 234Th produces 234Pa/234mPa pair, which decay to 234U, with a half-life of 6.70 h, emitting an intense beta radiation in the order of 2.2 MeV [1]. This short-lived thorium isotope has been used as a tracer for a variety of transport processes in aquatic systems [2,3]. Pourbaix diagram for aqueous solution of thorium and uranyl, as presented in Figure 1, shows that Th4+ has pref-erential hydroxide formation if compared to (UO2)2+ in pHs greater than 3. For this, some beta/alpha ratio increase is fore-seen during uranyl electrodeposition. Considering lower pHs, there is a prevalence of ionic state for either cations Th4+ or (UO2)2+. [Figure 1 – Pourbaix Diagram for uranyl solution containing thorium in low concentration.] The present work made an extensive experimentation to obtain thorium precipitation as 234Th, which happens during uranyl reduction or hydroxyl precipitation. The experimental process was as indicated below:1. Acidic solutions of 50mM [U] in UO2(NO3)2 in 2˗propanol (ionic solution: 140 experiments) and 50mM [U] UO2(NO3)2 in bidistilled water (aqueous solution: 98 experiments) with pH~1; 2. Direct cathodic polarization galvanostatic set at ˗100mA (110 experiments); 3. Pulsed cathodic polarization galvanostatic set at ˗100mA during 70 ms (“on”-stage) followed by 10 ms (“off”-stage) with a frequency of 12.5 Hz (128 experiments). The 4-graph set in Figure 2 shows the main results of the 234Th electrodeposition by means of radioactive alpha and beta emission counting. From these results, it is re-markable that the direct polarization and aqueous solu-tion has no great effect in changing the beta/alpha ratio. The level of this ratio stayed under 10, which could be a sign of preferential electrodeposition of thorium as indi-cated in Pourbaix diagram. However, when 2˗propanol uranyl electrolyte was used associated with pulse polari-zation, the results showed drastic increase of beta/alpha ratio. It reached ratio levels above 100. [Figure 2 – Results of ratio, varying with pH, from electrodeposi-tion experiments taking into account the solution type (aqueous and ionic) and the electrodeposition method (direct and pulsed). Experiments: 238 in total; 98 aqueous and 140 ionic; 110 using direct polarization and 128 using pulsed polarization.] This association of pulse polarization and ionic electro-lyte under high cathodic polarization imposed variables that are important to build up the 234Th content obtained from uranyl-solution electrodeposition in very acidic 2-propanol media, under higher cathodic polarization. This occurrence might be linked to restrictions imposed by non-protonated process by using 2-propanol solution, hindrance of water electrolysis to produce hydroxyl near the cathode and H2 evolution4,5, which promotes very acidic media around the cathode and probable hydride formation in absence of hydroxyl. As a general idea, there is a likely co-reduction of Th4+ and U4+ co-reduction, forming hydride species. The co-reduction from uranium-VI (uranyl) to uranium-IV has a feasible condition under high acidic condition, low water electrolysis and non-equilibrium of high imposed cathodic polarization4,5. When there is an exhaustion of thorium deposition in the same solution, noticed by beta-counting decreasing, it is observed that uranium electrodeposition starts more promptly, discernible by alpha-counting increasing.