Initial Uranium Concentration Research Articles

U(Ⅵ) sorption by porous sodium zirconium phosphate pellets from aqueous solution

Zirconium phosphate is the first artificially produced layered phosphate that can sorb a variety of nuclides from solutions. Sodium zirconium phosphate (NZP) was a type of α-zirconium phosphate (α-ZrP). The porous sodium zirconium phosphate pellets (p-NZP-P) with a diameter of more than ∼3 mm were prepared and used for uranium sorption. The p-NZP-P could be immersed in solutions for more than 5 days without dissolving and structurally collapsing. The sorption properties of U(Ⅵ) on p-NZP-P in solutions were investigated by both static and dynamic sorption tests. Synthetic p-NZP-P was analyzed in detail using various characterizations to investigate their character and structural changes. In the static sorption experiment, the equilibrium sorption capacity reached the 77.5 ± 1.5 mg·g−1 when the initial concentration of U(Ⅵ) was 100 mg/L, pHinitial = 4.5, T = 25 ℃. Uranium sorption increased by ∼69 % and ∼215 %, respectively, when the initial uranium concentration was increased from 100 to 300 mg·L−1 and the temperature was increased from 15 to 55 °C. Furthermore, uranium sorption increased by ∼541 % when the initial pH increased from 2.5 to 4.5, while it decreased by ∼39 % when the initial pH increased from 4.5 to 7.0. The sorption data corresponded to the pseudo-second-order kinetic model and the Langmuir isotherm model, as well as the theoretically predicted value of sorption capacity (∼199.9 mg·g−1). The results of the dynamic sorption experiment showed that decreasing the quality, increasing the flow rate and the initial U(Ⅵ) concentration would shorten the breakthrough time. The dynamic sorption data agreed well with the Thomas model. The characterization confirmed the porous properties, while the U(Ⅵ) sorption mechanisms relate to –OH coordination and ion exchange. A radioactive rare earth wastewater treatment test suggested that p-NZP-P could be the potential uranium sorbent due to its good stability and efficiency. This paper opened opportunities for the development of practical materials for treating radioactive wastewater in the application of actual scenarios.

Adsorption of Uranium (VI) From Aqueous Solution Using Melamine Formaldehyde Organo Clay Nanocomposite Foam as a Novel Adsorbent

Uranium is a toxic radioactive element and is usually found in the environment in hexavalent form. It has become necessary to remove uranium, which can be released into the environment in excessive amounts through nuclear industrial activities, from access waters. Melamine formaldehyde/organo clay nano composite foam (MFCNCF) was prepared as a novel adsorbent by hardening with thermal treatment. Structural, crystallographic textural and surface morphological characterization of the prepared adsorbent was made by Fourier transform infrared spectrophotometry (FTIR), X-Ray diffraction (XRD), Scanning electron microscopy (SEM) and High-resolution transmission electron microscopy (HRTEM) analyses. This study aimed to investigate the adsorption of U(VI) from aqueous solutions by MFCNCF and its dependence on various variables, such as initial uranium concentration, adsorption time, adsorbent dosage, initial pH, and temperature. Additionally, its adsorption isotherm analysis and adsorption kinetics and thermodynamics were also examined. For this purpose, batch adsorption experiments were carried out and the equilibrium concentration of U(VI) in the aqueous solution was measured with a UV-Vis spectrophotometer at a wavelength of 433 nm, which corresponds to its maximum absorptivity. The results regarding adsorption kinetics showed that 30 min was sufficient to reach adsorption equilibrium and the data showed a high fit to the pseudo-second-order kinetic model. Isotherm analysis also revealed a high fit of the data to the Type III isotherm and the Halsey model. Based on these fits, an adsorption mechanism involving two regions (electrostatic and complex formation) is proposed for the current adsorption system. The adsorption isosteric enthalpy and entropy values for the first and second regions were found to be −5.35 and 2.02 kJ/mol and −16.98 and 6.40 J/mol, respectively. The experimental results showed that the prepared nanocomposite foam adsorbent is an effective and potential alternative for the effective removal of U(VI) from aqueous solutions.

Behavior of uranium(VI) in the presence of a geomaterial: an aquifer sediment

Sediments from aquatic environments can be contaminated with uranium from natural and anthropogenic sources; the behavior of U(VI) was investigated in two natural (SPT and DS) and gamma-irradiated (SPT-I) aquifer sediments in batch systems. Sediments were characterized, and quartz, albite, and kaolinite were mainly found in both sediments by X-ray diffraction. The points of zero charge were 5.4, 5.3, and 5.5, and the organic matter percentages were 48.0, 46.0, and 4.7% for SPT, SPT-I, and DS, respectively. Uranyl nitrate solutions were put in contact with each sediment considering different parameters (pH, contact time, initial concentration of uranium, and temperature). DS sediment did not adsorb any quantity of uranium at different pH values; SPT and SPT-I, attained the highest q e values at pH 3.5–4. The results show chemisorption on homogenous materials and endothermic processes. Desorption behavior of U(VI)/SPT showed a hundred percent desorption with nitric acid and humic acid solutions; in the last case, it is due to the high stability constant of the complex of uranium with the humic acids. The results help to understand the contamination and decontamination processes of sediments with uranium, the bioavailability of uranium, the ecological risk of U-contaminated sediments, and remediation. Doses of 1 MGy of Co-60 gamma radiation did not affect the uranyl ions behavior in the aquifer sediment.

Chemical modification of Aspergillus flavus extracted chitosan for uranium remediation from aqueous solution

ABSTRACT Fungal chitosan derived from Aspergillus flavus AFC was employed in the synthesis of a cross-linked polystyrene biopolymer, P-AFC, which was investigated as a biosorbent material for the effective removal of uranium ions U(VI) from aqueous solutions. The characterisation of both fungal biopolymers was achieved using Brunauer-Emmett-Teller (BET) analysis, scanning electron microscopy (SEM), and Fourier-transform infrared (FTIR) spectroscopy. The efficacy of the P-AFC biosorbent in removing uranium from an aqueous solution reached equilibrium in 240 minutes at an initial uranium concentration of 50 ppm, a biosorbent amount of 0.4 g/L, and a pH of 4.0. The maximum biosorption capacity for U(VI) was determined to be 128.21 mg g−1 at room temperature, calculated using the Langmuir model. Furthermore, kinetic and thermodynamic analyses indicated that the biosorption process was characterised by chemisorption, was exothermic, and occurred spontaneously (ΔHo = –59.98 kJ mol−1 and ΔSo = –113.32 J K−1 mol−1). Recycling experiments demonstrated that the material could be reused up to five times without a noticeable decrease in removal efficiency.

Synthesis of isotype heterojunction by series calcination of multicomponent for high efficiency photocatalytic reduction of uranium

Photocatalytic reduction of soluble U(VI) to insoluble U(IV) is considered to be one of the most effective strategies for uranium contaminant removal. Graphite carbon nitride (g-C3N4) was widely used in the photocatalytic reduction of uranium due to its adjustable band structure and excellent chemical stability. Herein, through supramolecular self-assembly method, using thiourea as precursors, a carbon nitride photocatalyst (sp-ICN) with an isotype heterojunction structure was prepared by multicomponent series calcination for photocatalytic reduction of U(VI). The effects of pH, photocatalyst dosage and initial uranium concentration were examined on the effectiveness of the sp–ICN–1.0 photocatalytic reduction of uranium. The optimal reaction rate of sp–ICN–1.0 was 0.088 min−1, being 2.8 and 2.6 times that for pristine TCN (0.031 min−1) and sp-MCN (0.034 min−1), respectively. After 5 recycling experiments, more than 90% of U(VI) can still be reduced, indicating that sp–ICN–1.0 has good stability and repeatability in photocatalytic reduction of uranium. The electrochemical characterization of sp–ICN–1.0 showed that the formation of carbon nitride isotype heterojunction could improve the efficiency of photogenerated carrier separation and transfer, also reduce the resistivity of electron migration. A potential mechanism for photocatalytic reduction in U(VI) has been proposed. The result provides an idea for the further development of a novel semiconductor carbon nitride photocatalyst for the photocatalytic reduction of uranium.

Efficient removal of uranium from acidic mining wastewater using magnetic phosphate composites

Uranium mining operations produce large volumes of acidic uranium mining wastewater, necessitating the development of environmentally friendly and recyclable materials for efficient uranium removal and recovery. The current study successfully produced hydroxyapatite (HAP-L) and magnetic phosphate composites (CaFeP-1, CaFeP-2, and FePO4) through a combination of mixing, ultrasonication, hydrothermal precipitation, and calcination methods. The research explores the influence of various parameters such as pH, solid–liquid ratio, contact time, initial uranium concentration, co-existing ions, and recyclability on the uranium removal efficiency of these materials. The findings indicate exceptional uranium adsorption capacities, with CaFeP-1 exhibiting the highest capacity among the materials, especially in acidic environments. Moreover, CaFeP-1 displays strong resistance to interference from other ions and can be recycled multiple times while maintaining high removal rates. Treatment of acidic uranium mining wastewater by CaFeP-1 results in pH adjustment and the reduction of uranium and other ion concentrations, making it a promising solution for comprehensive remediation of acidic uranium mining wastewater. The U(VI) removal mechanism by CaFeP-1 was validated through XRD, FT-IR, and XPS results. The U(VI) removal was attributed to processes such as dissolution-precipitation, surface complexation, and ion exchange. The formation of sodium uranyl phosphate hydrate was identified as a new product following U(VI) abatement by CaFeP-1. In summary, CaFeP-1 shows great potential for the effective treatment of acidic uranium mining wastewater.

Uranium removal in groundwater by Priestia sp. isolated from uranium-contaminated mining soil

Priestia sp. WW1 was isolated from a uranium-contaminated mining soil and identified. The uranium removal characteristics and mechanism of Priestia sp. WW1 were investigated. The results showed that the removal efficiency of uranium decreased with the increase of initial uranium concentration. When the uranium initial concentration was 5 mg/L, the uranium removal efficiency achieved 92.1%. The increase of temperature could promote the uranium removal. Carbon source could affect the removal rate of uranium, which was the fastest when the methanol was used as carbon source. The solution pH had significant effect on the uranium removal efficiency, which reached the maximum under solution pH 5.0. The experimental results and FTIR as well as XPS demonstrated that Priestia sp. WW1 could remove uranium via both adsorption and reduction. The common chloride ions, sulfate ions, Mn(II) and Cu(II) enhanced the uranium removal, while Fe(III) depressed the uranium removal. The Priestia sp. WW1 could effectively remove the uranium in the actual mining groundwater, and the increase of initial biomass could improve the removal efficiency of uranium in the actual mining groundwater. This study provided a promising bacterium for uranium remediation in the groundwater.

Extremely efficient aerogels of graphene oxide/graphene oxide nanoribbons/sodium alginate for uranium removal from wastewater solution

Waste-water pollution by radioactive elements such as uranium has emerged as a major issue that might seriously harm human health. Graphene oxide, graphene oxide nanoribbons, and sodium alginate nanocomposite aerogels (GO/GONRs/SA) were combined to create a novel nanocomposite using a modified Hummer's process and freeze-drying as an efficient adsorbent. Batch studies were conducted to determine the adsorption of uranium (VI) by aerogel. Aerogels composed of (GO/GONRs/SA) were used as an effective adsorbent for the removal of U (VI) from aqueous solution. Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to describe the structure, morphologies, and characteristics of (GO/GONRs/SA) aerogels. The initial concentration of uranium (VI) and other environmental factors on U (VI) adsorption were investigated, period of contact, pH, and temperature. A pseudo-second-order kinetic model can be employed to characterize the kinetics of U (VI) adsorption onto aerogels. The Langmuir model could be applied to understand the adsorption isotherm, and the maximum adsorption capacity was 929.16 mg/g. The adsorption reaction is endothermic and occurs spontaneously.

Recovery of uranium using epoxy-modified phosphorus pentasulfide as an efficient adsorbent for uranium extraction from aquatic environments.

Epoxy-modified phosphorus pentasulfide (EPMPS) formulation was developed for the supported recovery of uranium from aquatic environments. The selected components of the prepared formulation were tailored to produce a rigid foamed polymeric material that was rich in phosphorus, nitrogen, sulfur and oxygen atoms, thus increasing chelating bonding possibilities with uranium. FT-IR and SEM were applied to physically characterize the resulting sorbent. At an equilibrium time of 30 min, the phase ratio S/L of 1 g L-1, pH 3 and initial uranium concentration of 50 mg L-1 yielded an adsorption efficiency for uranium of 90%. An 85% elution of uranium from loaded EPMPS was achieved with 1 h shaking and a phase ratio (S/A) of 0.5 g/25 mL of 0.1 M CH3COONa. Sorption isotherm designs were exploited to analyze the findings from the experiments. Uranium had an adsorption capability of about 78.7 mg g-1. According to the results of uranium adsorption, when applied to an actual sample, EPMPS is a suitable substrate for uranium adsorption from nitrate media.

Phytic acid-modified carboxymethyl cellulose hydrogel for uranium adsorption from aqueous solutions

Phytic acid-modified carboxymethyl cellulose (CMC-PA) has been investigated as a promising adsorbent for the removal of uranium from aqueous solutions. The synthesis of CMC-PA involves the hydrogen bonding interaction between CMC and PA, resulting in the incorporation of PA groups onto the cellulose backbone. The hydrophilicity, reusability and adsorption capacity of the prepared CMC-PA hydrogel have improved with the increase of PA content. Moreover, the adsorption experiments were conducted by varying parameters such as pH, initial uranium concentration, and contact time. The results showed that CMC-PA exhibited excellent uranium adsorption performance, with a theoretical maximum adsorption capacity of 436 mg/g. In addition, the material exhibits excellent reusability, and the reusability improves with the increase of crosslinking density, indicating that the crosslinking structure of the polymer gel can effectively enhance the structural stability of the material. Furthermore, CMC-PA also exhibits high selective adsorption performance towards uranium ions in the presence of various competing ions. Its high adsorption capacity, reusability, and selectivity make it a promising candidate for high-performance uranium ion adsorbents.

Preparation of core-shell composite materials capable of slowly releasing phosphate and their remediation performance of uranium-contaminated groundwater

Acid in-situ leach uranium mining significantly alters the geochemistry of the ore zone, and leaves uranium, residual acid, as well as other potential contaminants in groundwater, which bring harm to human health and ecological environment. Many investigators have been trying to propose remediation strategies for the uranium-contaminated groundwater. Phosphate is an effective immobilization reagent of uranium in the groundwater. However, direct injection of phosphate tends to quickly form precipitates, resulting in fast blockage of the seepage passages in the ore zone around the injection holes and hindering its diffusion. In this paper, HAP@SiO2-600, HAP@SiO2-600@25SA, and HAP@SiO2-600@75SA with core-shell structures were prepared. Their slow-release of phosphate, the effects of pH, contact time, initial uranium concentration, and coexisting ions on their removal rate and efficiency of uranium, and their function of remediating uranium-contaminated groundwater were investigated. It was found that the increase of SA content in the outer layer of HAP@SiO2-600@25SA and HAP@SiO2-600@75SA resulted in the slow release rate of phosphate, decreasing the removal rate of uranium. The adsorption capacities of HAP@SiO2-600, HAP@SiO2-600@25SA, and HAP@SiO2-600@75SA from the aqueous solution at pH = 3.0 and 303 K were up to 582.6, 558.5, and 507.3 mg g−1, respectively. In addition, the materials showed excellent uranium removal performance in experiments where multiple ions coexisted. For actual acidic uranium-contaminated groundwater, HAP@SiO2-600, HAP@SiO2-600@25SA, and HAP@SiO2-600@75SA effectively increased the pH from 2.75 to 4.40, 3.87, and 3.72, respectively, and decreased the uranium concentration from 5.12 to 0.0062, 0.0065, and 0.0058 mg L−1, respectively. The FT-IR, XRD, TEM and XPS characterizations were performed to further clarify the uranium removal mechanism, and it was found that the elimination of U(VI) was ascribed to dissolution-precipitation, adsorption and ion exchange. The results show that the core-shell composite material capable of slowly releasing phosphate is effective in remediating uranium-contaminated groundwater.

Biomineralization of uranium by Desulfovibrio desulfuricans A3-21ZLL under various hydrochemical conditions

Uranium pollution in groundwater environment has become an important issue of global concern. In this study, a strain of Desulfovibrio desulfuricans was isolated from the tailings of acid heap leaching, and was shown to be able to remove uranium from water via biosorption, bio-reduction, passive biomineralization under uranium stress, and active metabolically dependent bioaccumulation. This research explored the effects of nutrients, pH, initial uranium and sulfate concentration on the functional groups, uranium valence, and crystal size and morphology of uranium immobilization products. Results showed that tetravalent and hexavalent phosphorus-containing uranium minerals was both formed. In sulfate-containing water where Desulfovibrio desulfuricans A3-21ZLL can grow, the sequestration of uranium by bio-reduction was significantly enhanced compared to that with no sulfate loading or no growth. Ungrown Desulfovibrio desulfuricans A3-21ZLL or dead ones released inorganic phosphate group in response to the stress of uranium, which associated with soluble uranyl ion to form insoluble uranium-containing precipitates. This study revealed the influence of hydrochemical conditions on the mineralogy characteristics and spatial distribution of microbial uranium immobilization products. This study is conducive to the long-term and stable bioremediation of groundwater in decommissioned uranium mining area.

Polyamidoxime-loaded biochar sphere with high water permeability for fast and effective recovery of uranium from seawater

Given the plentiful uranium resources within the ocean, seawater uranium recovery holds significant importance for facilitating sustainable nuclear power development. There has been extensive research involving biochar materials for seawater uranium recovery. Existing biochar materials, on the other hand, exist primarily as powders, which are difficult to recover from use. Besides, traditional amidoxime-based adsorbents exhibited low uranium extraction rate, thus greatly hindering their practical application. In this study, a biochar sphere loaded with polyamidoxime (PAO) is prepared by using carbonized mycelium and PAO, designated as PAO-BS, in order to extract the uranium efficiently and quickly. Benefited from the ultrahigh porosity, hydrophilicity and water permeability, PAO-BS shows outstanding the adsorption efficiency of uranium. In comparison to other amidoxime-based adsorbents, the PAO-BS material demonstrates a remarkable extraction capacity of 211.35 mg g−1 in simulated seawater with an initial uranium concentration of 16 ppm, implying the high efficiency of functional group utilization in PAO-BS. Collectively, these results indicate that the rapid and highly effective recovery of uranium from natural seawater using PAO-BS has considerable potential.

TiO2/CPAN-AO heterojunction in-situ grow on carbonized melamine sponge for photocatalytic reduction of uranium (VI)

Extraction of uranium from seawater is of great significance to the development of nuclear energy. Photocatalytic reduction technology offers an innovative solution for the uranium recovery. However, traditional photocatalysts in powder form are limited by recyclable issue. Herein, a constructed novel composite sponge with TiO2/CPAN-AO binary photocatalyst that improved performance in uranium recovery from seawater on account of its exceptional photocatalytic performance, high selectivity, and recyclability. In addition, a new adsorption system called "Diffusion-Capture-Anchoring" was developed for photocatalytic reduction of uranyl ions. The removal rate of uranium within 105 min was 98%, when the initial uranium concentration was 100 mg/L. The selectivity and specificity of the material for uranium were established by the addition of interfering cations. Antimicrobial experiment proved that a great inhibitory effect on Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), and Pseudoalteromonas xiamenensis (P. xiamenensis). More importantly, the excellent recycling property of the CS/TiO2/CPAN-AO was tested via the ten cycles of experiment. As an efficient and recyclable adsorbent, the CS/TiO2/CPAN-AO composite sponge demonstrates great potential for extracting uranium from the seawater.

Construction of dopamine supported Mg(Ca)Al layered double hydroxides with enhanced adsorption properties for uranium

A novel dopamine-supported Mg(Ca)Al layered double hydroxide composite was synthesized by co-precipitation method. The existence of Ca2+ and dopamine could promote the capture of uranium on the layered double hydroxides. In batch experiments, the composite exhibited good uranium removal performance, including high adsorption capacity (687.3 mg/g), strong anti-interference and good reusability (the removal percentage was still higher than 90 % after five cycles). At low initial uranium concentration, the uranium removal percentage on the composite exceeded 99.7 % and the residual concentration of uranium in the solution was <0.03 mg/L, reaching the limited standard of the World Health Organization. The studies of adsorption kinetics and isotherm indicated that the uranium adsorption behavior on the composite conformed to the pseudo-second-order kinetic and Langmuir isotherm models, suggesting that the process was a monolayer adsorption dominated by chemical adsorption. Furthermore, the high-efficiency uranium adsorption on the Mg(Ca)Al layered double hydroxide was mainly attributed to the strong complexation between the active sites (-OH and -NH2) and uranium, the precipitation of interlayer intercalation ions (CO32− and OH−) to uranium and the ion exchange of Ca2+ to uranium. Due to these advantages, the dopamine-supported Mg(Ca)Al layered double hydroxide composite is expected to be used as fine adsorbent to remove uranium from wastewater.

Application of Plantain leaves as a bio-adsorbent for biosorption of U(VI) ions from wastewater

Abstract Uranium biosorption was investigated using the bio-adsorbent of Plantain leaves. First, the bio-adsorbent structure was characterized using BET, SEM, and FTIR. The effective parameters pH, initial uranium concentration, bio-adsorbent dose, and the temperature were investigated using a central composite design (CCD). Experimental data were analyzed using Design Expert 12.0.3.0 software. According to the obtained results, the pH value of 4, initial metal ion concentration of 10 mg L−1, the bio-adsorbent dose of 0.297 g, and the temperature of 25 °C were proven for maximum biosorption efficiency of U(VI) ions from aqueous solutions. The contact time was investigated to understand the type of kinetics of the reaction. The maximum biosorption efficiency was 90 min. The optimal biosorption efficiency was 92.69%. The Freundlich isotherm and pseudo-second-order models were the best isotherms and kinetic models fitted with the results of the studied bio-adsorbent, respectively.

Kinetic study of uranium (VI) extraction with tributyl-phosphate in a stratified flow microchannel

Solvent extraction kinetics are of considerable importance in process and apparatus design, especially when the mass transfer is coupled with a chemical reaction. In such circumstances, the mass transfer can either be diffusion limited, reaction limited, or both in a mixed regime. Conventional extraction techniques lead to acquire an overall mass transfer coefficient for fast chemical systems. The latter brings together diffusional and reactional parts that are difficult to distinguish independently. This problem is addressed using a high velocity parallel flow microfluidic setup for the investigation of the extraction kinetics of the fast chemical system U(VI):HNO3/TBP:TPH. Experimental data were analyzed using a combination of overall mass transfer resistance calculations and advection–diffusion-reaction models. Results indicate that a chemically limited regime was obtained at a high initial concentration (119 g.l−1) of uranium (VI) due to Marangoni convections. Whereas, for low initial concentrations (10–30 g.l−1) and short residence times in the microchannel (≤13 ms), both diffusion and reaction impact the transfer rate. The obtained value of the apparent rate constant under current operating conditions ([HNO3] = 3 M, % TBP = 30 % (v/v)) was of (6.5 ± 1.7) × 10−4 m.s−1. This value is much higher than what conventional extraction techniques predicted, indicating the better mass transfer efficiency in the microfluidic setup due to the decrease of the diffusional limitation.

Surfactant assisted APTES functionalization of graphene oxide intercalated layered double hydroxide (LDH) for uranium adsorption from alkaline leach liquor

The efficacy of uranium adsorption by modified layered double hydroxide (LDH) has been studied in detail in this work. The effects of initial uranium (U) concentration, solution pH, adsorbent dose, temperature and the presence of other ions were investigated. The removal efficiency varied from 98% to 92% for the initial U concentration 54–216 mg/L. However, the removal efficiency was decreased to 84% when the feed concentration was increased to 432 mg/L. The removal of uranium increased with the solution pH and beyond 8.5 it was invariant indicating the adsorbent is highly suitable for treatment of alkaline leach liquor. The adsorption capacity decreased with temperature and the Langmuir capacity of the adsorbent were found to be 948, 1,026, and 1162 mg/g at 323, 313, and 303 K, at pH 8.5. Evaluation of isotherm in alkaline pH is rare in the literature and the adsorption capacity of U of the LDH based adsorbents are reported in the range of 180 to 1143 mg/g with a pH variation of 3–7 at 298 K. Second order rate equation described the adsorption kinetics adequately. It was shown that switching of pH to 11.5 resulted remarkable desorption of U. Thus, the developed adsorbent has tremendous potential to separate U from alkaline leach liquor. Much research is required to immobilize the nano-sized adsorbents in a suitable media for preparation of the commercial scale filters.

Optimization of synthesis conditions for preparation of radiation grafted polymeric fibers and process variables of adsorption with response surface methodology

Radiation-grafted polymeric adsorbents have a high adsorption capacity in purifying effluents from heavy metals. This study investigated adsorption conditions for removing uranium from aqueous nitrate solution using radiation-grafted polymeric adsorbent (PP-g-(PAAc-co-PAm)). The modified fiber (polypropylene) was synthesized with acrylic amide and acrylic acid monomers. The central composite design approach in two stages was used to determine optimal conditions. In the first stage, the effects of three factors such as acrylic amide concentration, sulfuric acid concentration and dose of gamma-ray on adsorbent synthesis were investigated to prepare an appropriate adsorbent. The impacts of three parameters, including the initial aqueous pH, uranium ion concentration, and equilibrium time on adsorption conditions, were studied using a central composite approach in the second stage. The optimum conditions for sulfuric acid concentration, acrylic amide concentration, the dose of gamma-ray, initial aqueous pH, uranium concentration, and time were optimized equally to 59.7% (v/v), 0.08 M, 20 kGy, 7, 80 ppm, and 3 h, respectively. The uranium adsorption yields equal to 62.04% achieved from the quadratic equation agreed with the experimental value equal to 59.07%. The uranium adsorption was attained to 16.79 mg/g with a grafting percentage of 30.58% under the optimum conditions. Kinetics and equilibrium isotherms described experimental data following pseudo-second-order and Langmuir models. Finally, the results showed that the radiation-grafted polymeric adsorbents are effective in uranium uptake from effluents.

Solid–liquid extraction of uranium from aqueous solution using Marathon C as a strong cation exchanger resin: kinetic, and isotherm studies

ABSTRACT In this study, Adsorption characteristics of uranium from nitrate media onto a commercially accessible strong cation exchange resin, Marathon C, were investigated. The characteristics of Marathon C, before and after adsorption of uranium, were determined using scanning electron microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). The influence of the different parameters, which may affect the process of uranium adsorption process from synthetic solutions and applying on real sample from uranium purification unit, had been tracked. Specifically, impacts of initial uranium concentration (40–300 mg/L), PH (1–8), phase ratio (0.2–1.2 g/L), contact time (2–360 min.) and temperature (& 25–50°C) on uranium removal, were studied. In addition, the sorption kinetics and equilibrium parameters were assessed. At the optimum conditions, the adsorption capacity of uranium at PH 4, 1 g Marathon C/L and 120 min were found to be nearly 131.58 mg g−1 at room temperature (& 25°C). The kinetics and isotherm studies could show that the uranium adsorption onto Marathon C is following the models of pseudo-second-order and Langmuir isotherm, respectively. The thermodynamic parameters had indicated that the adsorption of uranium is an exothermic and spontaneous process (∆H = −64.27 ± 0.01, ∆G = −22.57 ± 0.02). The detected results of uranium adsorption could reveal that Marathon C is a suitable material for adsorption of uranium from nitrate media and applying on real sample from uranium purification unit.