Enhanced removal of U(VI) from aqueous solution by chitosan-modified zeolite

Journal of Radioanalytical and Nuclear Chemistry - A typical type of natural zeolite(Z) modified with chitosan was applied to remove U(VI) from aqueous solution. Batch experiments were performed to...     

Adsorptive removal of U(VI) from aqueous solution by hydrothermal carbon spheres with phosphate group

The phosphorylated hydrothermal carbon spheres (HCS-PO₄) were developed by functionalizing hydrothermal carbon spheres (HCS) with o-phosphoethanolamine, and the structure and textural property were characterized by SEM and FT-IR. The parameters that affect the uranium(VI) sorption, such as solution pH, initial U(VI) concentration, contact time, and temperature, had been investigated. The HCS-PO₄ showed the highest uranium sorption capacity at initial pH 6.0 and contact time of 120 min. The adsorption kinetics was better described by the pseudo-second-order model, and the adsorption process could be well defined by the Langmuir isotherm and the maximum monolayer adsorption capacity increased from 80.00 to 434.78 mg/g after phosphorylation. The thermodynamic parameters, ?G° (298 K), ?H° and ?S°, demonstrated shown that the sorption process of U(VI) onto HCS-PO₄ was feasible, spontaneous and endothermic in nature. The spent HCS-PO₄ could be effectively regenerated by 0.1 mol/L EDTA solution for the removal and recovery of U(VI) and reused for ten cycles at least. Selective adsorption studies showed that the HCS-PO₄ could selectively remove U(VI), and the selectivity coefficients of HCS in the presence of co-existing ions, Mg(II), Na(I), Zn(II), Mn(II),Co(II), Ni(II), Sr(II), Cs(I) and Hg(II) improved after functionalization.     

Adsorption of U(VI) from aqueous solution by cross-linked rice straw

Adsorption of U(VI) from aqueous solution by cross-linked rice straw(CRS) was studied with batch experiments. The adsorbent was characterized by Fourier transform infrared spectroscopy (FT-IR). The effect of contact time, initial pH, temperature, adsorbent amount and initial U(VI) concentration was investigated. Langmuir, Freundlich and Dubinin–Radushkevich (D–R) adsorption isotherms and two kinetic models of pseudo-first-order and pseudo-second-order were used to describe the adsorption process. The result showed that the adsorption process was highly pH dependent and the favorable initial pH was 5.0. The adsorption process was rapid within first 60 min and equilibrium reached at 100 min. The adsorption process could be well defined by the Langmuir isotherm and pseudo-second-order equation, which indicated that the chemical adsorption was the rate-limiting step. The thermodynamic parameters (?H°, ?S°, ?G°) of the adsorption system were also calculated. The negative value of ?H° and ?G° indicated that the reaction was endothermic and spontaneous in nature. All the above suggested that CRS has considerable potential for the removal of U(VI) from aqueous solution.     

High performance of phosphonate-functionalized mesoporous silica for U(VI) sorption from aqueous solution

The renaissance of nuclear energy promotes increasing basic research on the separation and enrichment of nuclear fuel associated radionuclides. Herein, we report the first study for developing mesoporous silica functionalized with phosphonate (NP10) as a sorbent for U(VI) sorption from aqueous solution. The mesoporous silica was synthesized by co-condensation of diethylphosphatoethyltriethoxysilane (DPTS) and tetraethoxysilane (TEOS), using cationic surfactant cetyltrimethylammonium bromide (CTAB) as the template. The synthesized silica nanoparticles were observed to possess a mesoporous structure with a uniform pore diameter of 2.7 nm, and to have good stability and high efficiency for U(VI) sorption from aqueous solution. A maximum sorption capacity of 303 mg g(-1) and fast equilibrium time of 30 min were achieved under near neutral conditions at room temperature. The adsorbed U(VI) can be easily desorbed by using 0.1 mol L(-1) HNO(3), and the reclaimed mesoporous silica can be reused with no decrease of sorption capacity. In addition, the preconcentration of U(VI) from a 100 mL aqueous solution using the functionalized mesoporous silica was also studied. The preconcentration factor was found to be as high as 100, suggesting the vast opportunities of this kind of mesoporous silica for the solid-phase extraction and enrichment of U(VI).     

Fe3O4-modified sewage sludge biochar for U(VI) removal from aqueous solution: performance and mechanism

Journal of Radioanalytical and Nuclear Chemistry - Sewage sludge-derived biochar (SSB) was prepared at 600 °C pyrolysis temperature and modified by co-precipitation with Fe3O4 to...     

Adsorption of U (VI) ions from aqueous solution using silicon dioxide nanopowder

The adsorption kinetics for removal of uranium (V1) from aqueous solution using silicon dioxide nanopowder (nano-SiO₂) was investigated in batch and continuous techniques. Pseudo-first order and pseudo-second order were used to analyze the kinetics of batch experiments. In continuous technique the important parameters (initial concentration, flow rate and bed height) on the breakthrough curves were studied and the adsorption kinetics was analyzed using Thomas and Yoon and Nelson kinetic models. The comparison between the kinetic models was evaluated by the correlation coefficients (r²). The results indicated that the batch experiments fitted well with pseudo second-order kinetic model. The comparison of the experimental breakthrough curve to the breakthrough profile obtained from Thomas and Yoon and Nelson methods showed a satisfactory fit for silicon dioxide nanopowder.     

Adsorption of U(VI) from aqueous solution by sulfonated ordered mesoporous carbon

The sulfonated mesoporous carbon (CMK-3-SO₃H) prepared by functionalizing mesoporous carbon (CMK-3) via vapor transfer method has been explored for the removal and recovery of uranium from aqueous solutions. The influences of different experimental parameters such as solution pH, initial concentration, contact time and temperature on adsorption were investigated. The results showed that CMK-3-SO₃H has the highest uranium sorption capacity at initial pH of 5.0 and contact time of 120 min, and the adsorption process could be better described by the pseudo-second-order model and Langmuir isotherm. Selective adsorption studies showed that the CMK-3-SO₃H could selectively remove of U(VI), and the selectivity coefficients of mesoporous carbon in the presence of co-existing ions, Mg(II), Zn(II), Mn(II), Cu(II), Ni(II), Sr(II) and Hg(II) improved after functionalization.     

Application of Brazilian kaolinite clay as adsorbent to removal of U(VI) from aqueous solution: Kinetic and thermodynamic of cation-basic interactions

The compound N¹-[3-(trimethoxysilyl)propyl]diethylenetriamine was anchored onto Amazon kaolinite surface by heterogeneous route. The modified and natural kaolinite samples were characterized by transmission electron microscopy, scanning electron microscopic, X-ray diffraction, and nuclear magnetic nuclei of ²⁹Si and ¹³C. The well-defined peaks obtained in the ¹³C NMR spectrum in the 5.0-62.1 ppm region confirmed the attachment of organic functional groups as pendant chains bonded into the porous clay. The ability of these materials to remove U(VI) from aqueous solution was followed by a series of adsorption isotherms adjusted to a Sips equation at room temperature and pH 4.0. The kinetic parameters analyzed by the Lagergren and Elovich models gave a good fit for a pseudo-second order reaction with k₂ values 16.0 and 25.1 mmol g⁻¹ min⁻¹ ranges for natural and modified kaolinite clays, respectively. The energetic effects caused by metal ion adsorption were determined through calorimetric titrations.     

Polyaniline/oxidation etching graphitic carbon nitride composites for U(VI) removal from aqueous solutions

Journal of Radioanalytical and Nuclear Chemistry - Polyaniline/oxidation etching g-C3N4 composites (PANI/OCN) were synthesized through an oxidative polymerization method and applied to remove...     

Low-cost reed straw-derived biochar prepared by hydrothermal carbonization for the removal of uranium(VI) from aqueous solution

Journal of Radioanalytical and Nuclear Chemistry - Uranium is the important nuclear fuel and its effective adsorption using low-cost materials is meaningful to environmental protection and...     

A high efficient sorption of U(VI) from aqueous solution using amino-functionalized SBA-15

Uranium is one of the most hazardous heavy metal due to its long half-life radioactivity, high toxicity and mobility as aqueous uranyl ion (UO₂ ²⁺) under ordinary environmental conditions. Herein, amino functionalized SBA-15 (APSS) was developed as a rapid and efficient sorbent for removal of U(VI) from the environment. The APSS sample was synthesized by grafting method and was characterized by SEM, NMR, SAXS, and N₂ sorption/desorption isothermal experiments. The sorption of U(VI) by APSS was investigated under different conditions of pH, contact time, initial U(VI) concentration, ionic strength and solid–liquid ratio. The results show that the sorption of U(VI) by APSS is strongly dependent on pH but independent of ionic strength and solid–liquid ratios (m/V). The sorption is ultrafast with an equilibrium time of less than 30 min, and the sorption capacity is as large as 409 mg/g at pH 5.3 ± 0.1. Besides, the U(VI) sorption by APSS from extremely diluted solution and the desorption of U(VI) from APSS were also studied. It is found that 100 mg of APSS can almost completely remove the U(VI) ions from 4 L aqueous solution with the U(VI) concentration as low as 4.2 ppb and the sorbed U(VI) can be completely desorbed by 0.1 mol/L nitric acid. The results strongly reveal the high performance of the APSS material in the removal and preconcentration of U(VI) from the aqueous solution.     

Ozonated graphene oxides as high efficient sorbents for Sr(II) and U(VI) removal from aqueous solutions

Ozone was used to oxidize graphene oxides (GO) to generate ozonated graphene oxides (OGO) with higher oxygen-containing functional groups. The as-prepared OGO was characterized by Fourier transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Based on the results of potentiometric acid-base titrations, the total carboxylic acid concentration on OGO surface was calculated to be 3.92 mmol/g, which was much higher than that on GO surface. The results of adsorption experiments indicated that the adsorption capacities of OGO for Sr(II) and U(VI) removal were improved significantly after ozonization.     

Synthesis of molybdenum disulfide/graphene oxide composites for effective removal of U (VI) from aqueous solutions

Journal of Radioanalytical and Nuclear Chemistry - In this study, a novel adsorbents, molybdenum disulfide-graphene oxide (MoS2–GO) composites, is prepared by one-step hydrothermal method and...