Hydrothermal leather waste by hydrothermal method for uranium (VI) removal from a Simulated Saline Solution

Hydrothermal leather waste was prepared by hydrothermal method, using leather waste as the precondition and applying the adsorption of uranium (VI) in solution. The effects of pH value, adsorption time and initial concentration of uranium (VI) on the adsorption efficiency were investigated. The adsorption process was in accordance with the pseudo‐second‐order kinetic model and Freundlich adsorption isotherm model. Kinetic and thermodynamic studies showed that the adsorption process was endothermic and spontaneous, and it reached adsorption equilibrium in 240 min. In the simulated high salinity environment, the adsorbent exhibited excellent adsorption rate on the trace of uranium (VI). The adsorbent was characterized by scanning electron microscopy, flourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy, and it was found that the adsorption mechanism was coordinated complex.     

新型磁性复合生物吸附剂吸附铀的实验研究

为了提升含铀废水的净化效果,制备一种新型磁性复合生物吸附剂,用于铀离子的吸附实验研究,运用BET吸附理论、红外光谱(IR)、X射线衍射光谱(XRD)、扫描电子显微镜(SEM)等对吸附剂进行表征,对吸附动力学进行研究.实验结果表明,Fe3 O4和啤酒酵母粉质量比为1:2,溶液pH值为5、吸附剂用量为0.05 g、初始浓度...     

Sorption of uranium from alkaline waste onto radiation grafted phosphoryl-g-Teflon matrix

High energy ⁶⁰Co γ-radiation was used to graft glycidylmethacrylate onto Teflon scrap through mutual radiation grafting technique. The epoxy ring of grafted polyGMA chains were later converted to U selective phosphoryl group, chemically. The grafted matrix was used as solid–liquid adsorbent of uranium from alkaline waste solution. More than 98% recovery of uranium from alkaline waste (~pH 8) solution was achieved. The effect of grafting extent on adsorption kinetics was also investigated. The selectivity of uranium extraction over other fission products was established. The uptake of other fission products was <5% for equilibration time of ~1 h.

     

Recovery of uranium using immobilized polyhydroxybenzene

In order to develop a new adsorbent for uranium, the adsorption of uranium from seawater by immobilized polyhydroxybenzene compounds has been investigated. Polyhydroxybenzene compounds having adjacent hydroxy groups, such as catechol and pyrogallol, form stable five-membered chelate ring with uranyl ion. The immobilized polyhydroxybenzene compounds have an excellent ability to adsorb uranium from seawater. Especially, the immobilized pyrogallol, having two chelating positions for uranyl ion, is the most suitable adsorbent for uranium recovery from seawater. This adsorbent also has a selectivity for uranium.     

Determination of uranium(VI) in natural waters after preconcentration on adsorbent containing m-aminophenol fragments

Sorption and complexing properties of a modified adsorbent based on a maleic anhydride-styrene copolymer towards uranium(VI) are studied and the main quantitative characteristics of the metal ion sorption are determined. An adsorbent containing m-aminophenol fragments is proposed for the selective sorption of uranium(VI) from solutions. The optimal sorption conditions have been found. The recovery of uranium(VI) under the optimal conditions exceeds 95%. A procedure of the sorption photometric determination of uranium(VI) in sea water is developed.     

Uranium adsorption from a liquid waste using thermally and chemically modified bentonite

In this work, uranium adsorption from aqueous (waste) solution onto thermal and chemical modified bentonite (TCMB) has been studied. The relevant factors affecting uranium adsorption onto our TCMB adsorbent were studied. These factors involved contact time, initial uranium concentrations, pH, adsorption temperature, foreign ion and the effect adsorbent (TCMB) amount using synthetic solution. The theoretical capacity of TCMB adsorbent is about 29 mg/g TCMB. The optimum adsorption conditions were choiced. Uranium elution from the loaded TCMB adsorbent has been carried out using CH₃COONa as an effective eluent. Uranium adsorption from Gattar liquid waste by TCMB adsorbent was carried out in columns. The low uranium adsorption efficiency (37.5 % of the theoretical capacity of TCMB) may be due to the adsorption competition between uranium and difference foreign ion present in the solution (as iron). More than 92 % of the loaded uranium amount on the TCMB adsorbent has been eluted using CH₃COONa as an efficient eluent.     

Adsorption of uranium on adsorbents produced from used tires

The present investigation deals with the potential use of adsorbents produced from used tires for the removal of uranium from aqueous solutions. Two different adsorbents were used including char and activated carbon produced from used tires. The surface area was larger on activated carbon. Adsorption experiments were carried out as a function of time, adsorbent concentration, pH and initial concentration of uranium. The adsorption kinetics was found to follow the Lagergren equation. The rate constants of intraparticle diffusion and mass transfer coefficients were calculated. It was shown that the equilibrium data could be fitted by the Langmuir and Freundlich equations. The adsorption of uranium in the presence of diffferent cations were also studied and the results were correlated with the ionic potential of the cations. Results obtained in the study demonstrate that the activated carbon produced from used tires can be considered as an adsorbent that has a commercial potential for uranium removal.     

Preparation of graphene oxide–chitosan composite and adsorption performance for uranium

The composite adsorbent graphene oxide–chitosan was prepared using graphite and chitosan as the initial materials. The structures and morphology of the products were characterized by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy. The products were used to remove uranium from aqueous solution by batch adsorption experiments. The effects of pH, adsorbent dosage, contact time, initial uranium concentration and temperature on the uranium removal were investigated, and the results were fitted by the adsorption isotherm models. The adsorption kinetic and thermodynamic were also studied in detail.     

Sorption of uranium(VI) from aqueous solution onto magnesium silicate hollow spheres

The sorption of uranium(VI) from aqueous solutions was investigated using synthesized magnesium silicate hollow spheres as a novel adsorbent. Batch experiments were conducted to study the effects of initial pH, amount of adsorbent, contact time and initial U(VI) concentrations on uranium sorption efficiency. The desorbing of U(VI) and the effect of coexisting ions were also investigated. Kinetic studies showed that the sorption followed a pseudo-second-order kinetic model. The Langmuir sorption isotherm model correlates well with the uranium sorption equilibrium data for the concentration range of 25–400 mg/L. The maximum uranium sorption capacity onto magnesium silicate hollow spheres was estimated to be about 107 mg/g under the experimental conditions. Desorption of uranium was achieved using inorganic acid as the desorbing agent. The practical utility of magnesium silicate hollow spheres for U(VI) uptake was investigated with high salt concentration of intercrystalline brine. This work suggests that magnesium silicate hollow spheres can be used as a highly efficient adsorbent for removal of uranium from aqueous solutions.     

Removal and recovery of uranium from aqueous solution by tea waste

Experiments on the removal and recovery of U(VI) from aqueous solution by tea waste were conducted. The adsorbent was characterized by scanning electron microscope and energy dispersive spectrometer before and after the adsorption treatment. The removal of U(VI) amounts to 86.80?% at optimum pH 6. The adsorption process reaches its equilibrium in 12?h at 308?K, and the kinetic characteristic can be described by the pseudo-second-order kinetic equation. The amount of adsorption increases from 22.92 to 142.21?mg?g^?1 with the decrease of tea waste dosage from 100 to 10?mg for solution with an initial uranium concentration of 50?mg?L^?1. Desorption for the four strippants is higher than 80?%. The equilibrium data are more agreeable with Freundlich isotherm than Langmuir isotherm.     

Adsorption of uranium (VI) from aqueous solution by tetraphenylimidodiphosphinate

The adsorption of uranium (VI) using tetraphenylimidodiphosphinate (Htpip) was studied. Factors of affecting sorption efficiency have been investigated and results showed the adsorption of uranium (VI) was equilibrium at pH 4.5, time 20 min, adsorbent dosage 0.005 g and initial concentration 50 mg L^?1 reaching 99.86 mg g^?1 of adsorption capacity and 99.86% of removal efficiency. Additionally, the interfering ions studies showed that the adsorbent possessed excellent adsorption selectivity of uranium (VI). The surface morphology of Htpip was investigated by SEM. The adsorption process of uranium (VI) onto Htpip fit the pseudo-second-order kinetic model and the Freundlich isotherm model very well.     

Removal of uranium from aqueous solutions by diatomite (Kieselguhr)

In this study, the removal of uranium from aqueous solutions by diatomite earth (Kieselguhr) fine particules has been investigated. Diatomite earth is an important adsorbent material in chromatographic studies. Uranium adsorption capacity of four different types of diatomite was determined. The adsorption of uranium on the chosen diatomite sample was examined as a function of uranium concentration, solution pH, contact time and temperature. The adsorption of uranium on diatomite followed a Langmuir-type isotherm.     

Determination of uranium isotopes in environmental samples

The determination of isotopes of uranium by alpha spectrometry in different environmental components (sediments, soil, water, plants and phosphogypsum) is presented and discussed in this paper. The alpha spectrometry is a very convenient and good technique for activity concentration of natural uranium isotopes (²³⁴U, ²³⁵U, ²³⁸U) in environmental samples and provides the most accurate determination of isotopic activity ratios between ²³⁴U and ²³⁸U. The analysis were provided information about possible sources of high concentrations of uranium in the examined sites determined by anthropogenic sources. The calculation of values ²³⁴U/²³⁸U in all analyzed samples was applied to identifying natural or anthropogenic uranium origin. Activity concentration of uranium isotopes in analyzed environmental samples shows that measurement of uranium levels is of great importance for environmental and safety assessment especially in contaminated areas (phosphogypsum waste heap).     

Diglycolamide functionalized multi-walled carbon nanotubes for removal of uranium from aqueous solution by adsorption

Diglycolamide functionalized multi-walled carbon nanotubes (DGA-MWCNTs) were synthesized by sequential chemical reactions for removal of uranium from aqueous solution. Characterization studies were carried out using FT-IR spectroscopy, XRD and SEM analysis. Adsorption of uranium from aqueous solution on this material was studied as a function of nitric acid concentration, adsorbent dose and initial uranium concentration. The uranium adsorption data on DGA-MWCNTs followed the Langmuir and Freundlich adsorption isotherms. The adsorption capacity of DGA-MWCNTs as well as adsorption isotherms and the effect of temperature on uranium ion adsorption were investigated. The standard enthalpy, entropy, and free energy of adsorption of the uranium with DGA-MWCNTs were calculated to be 6.09 kJ mole⁻¹, 0.106 kJ mole⁻¹ K⁻¹ and −25.51 kJ mole⁻¹ respectively at 298K. The results suggest that DGA-MWCNTs can be used as efficient adsorbent for uranium ion removal.     

Anion-exchange enrichment and spectrophotometric determination of uranium in sea-water

A method is proposed for the determination of uranium in sea-water. The uranium is strongly sorbed on a strongly basic anion-exchange resin (Cl(-) form) from acidified sea-water containing sodium azide (0.3M) and is easily eluted with 1M hydrochloric acid. Uranium in the effluent can be determined spectrophotometrically with Arsenazo III. The combined method allows easy and selective determination of uranium in sea-water without using a sophisticated adsorbent. The overall recovery and precision are satisfactory at the 3 mug/1. level.     

Extraction fluorimetric determination of uranium by conventional spectrophotometry

The determination of uranium by a fluorimetric method using a conventional spectrophotometer has been elaborated. The quenching effect of the matrix was reduced by separation with liquid-liquid extraction and emulsion liquid membrane extraction methods using D2EHPA as a selective extraction reagent. The method was employed for uranium determination in radioactive waste solutions and proved to be very fast and easy to perform. It was found that it is possible to determinate as low as 0.2 ppm of uranium in a 10 ml sample.     

Alpha emitters from uranium mining in the environment

Uranium mining and milling activities usually generate an enhancement of radionuclide concentrations in the environment that may cause increased radiological exposure to mankind. For risk assessment and radiological protection of man and environment in these areas, usually, it is needed to implement radiological surveillance of water, soils, agricultural products, aerosols, and mining waste discharges as well. Radionuclides to be monitored in priority are alpha-emitting nuclides of the uranium natural series. Radioactivity analysis of materials from uranium mining areas of Portugal shows departure from secular radioactive equilibrium amongst uranium series radionuclides, thus rendering invalid the assumption of equilibrium and requiring the actual determination of each radionuclide. Radionuclide measurements performed with high resolution alphaspectrometry, as reported herein, produce accurate results on specific radionuclides that are essential in computing radiation doses to critical groups of the population.     

Dissolution of metallic uranium and its alloys

This review focuses on dissolution/reaction systems capable of treating uranium metal waste to remove its pyrophoric properties. The primary emphasis is the review of literature describing analytical and production-scale dissolution methods applied to either uranium metal or uranium alloys. A brief summary of uranium's corrosion behavior is included since the corrosion resistance of metals and alloys affects their dissolution behavior. Based on this review, dissolution systems were recommended for subsequent screening studies designed to identify the best system to treat depleted uranium metal wastes at Lawrence Livermore National Laboratory (LLNL). This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis, characterization, thermodynamic and kinetic investigations on uranium (VI) adsorption using organic-inorganic composites: Zirconyl-molybdopyrophosphate-tributyl phosphate

Zirconyl-molybdopyrophosphate-tributyl phosphate (ZMPP-TBP) was a novel organic-inorganic composite adsorbent prepared by co-precipitation method and used in the adsorption of uranium from aqueous solution in batch adsorption experiments. The as-obtained product was characterized using SEM, energy dispersive X-ray spectroscopy (EDX), XRD and BET-N₂ adsorption measurements. The study had been conducted to investigate the effects of solution pH, temperature, contact time, initial concentration and coexisting ions. A maximum removal of 99.31% was observed for an initial concentration 5 mg/L, at pH 6.0 and an adsorbent dose of 1.0 g/L. The isothermal data were fitted with both Langmuir and Freundlich equations, but the data fitted the former better than the latter. According to the evaluation using the Langmuir equation, the maximum adsorption capacity of uranium (VI) was 196.08 mg/g at 293 K and pH 6.0. The pseudo-first-order kinetic model and pseudo-second-order kinetic model were used to describe the kinetic data, and the pseudo-second-order kinetic model was better. The thermodynamic parameter ΔG was calculated, the negative ΔG values of uranium (VI) at different temperature showed that the adsorption process was spontaneous. The good reusability of ZMPP-TBP also indicated that the ZMPP-TBP was a very promising adsorbent for uranium adsorption from aqueous solution.