Efficient uranium immobilization on red clay with phosphates

Open-Framework Vanadate as Efficient Ion Exchanger for Uranyl Removal

The elimination of uranium from radioactive wastewater is crucial for the safe management and operation of environmental remediation. Here, we present a layered vanadate with high acid/base stability, [Me2NH2]V3O7, as an excellent ion exchanger capturing uranyl from highly complex aqueous solutions. The material possesses an indirect band gap, ferromagnetic characteristic and a flower-like morphology comprising parallel nanosheets. The layered structure of [Me2NH2]V3O7 is predominantly upheld by the H-bond interaction between anionic framework [V3O7]nn- and intercalated [Me2NH2]+. The [Me2NH2]+ within [Me2NH2]V3O7 can be readily exchanged with UO22+. [Me2NH2]V3O7 exhibits high exchange capacity (qm = 176.19 mg/g), fast kinetics (within 15 min), high removal efficiencies (>99%), and good selectivity against an excess of interfering ions. It also displays activity for UO22+ ion exchange over a wide pH range (2.00-7.12). More importantly, [Me2NH2]V3O7 has the capability to effectively remove low-concentration uranium, yielding a residual U concentration of 13 ppb, which falls below the EPA-defined acceptable limit of 30 ppb in typical drinking water. [Me2NH2]V3O7 can also efficiently separate UO22+ from Cs+ or Sr2+ achieving the highest separation factors (SFU/Cs of 589 and SFU/Sr of 227) to date. The BOMD and DFT calculations reveal that the driving force of ion exchange is dominated by the interaction between UO22+ and [V3O7]nn-, whereas the ion exchange rate is influenced by the mobility of UO22+ and [Me2NH2]+. Our experimental findings indicate that [Me2NH2]V3O7 can be considered as a promising uranium scavenger for environmental remediation. Additionally, the simulation results provide valuable mechanistic interpretations for ion exchange and serve as a reference for designing novel ion exchangers.

Bio-functionalized magnetic nanoparticles for cost-effective adsorption of U(vi): experimental and theoretical investigation

U(vi) removal using cost-effective (production cost: $14.03 per kg), biocompatible, and superparamagnetic Cinnamomum tamala (CT) leaf extract-coated magnetite nanoparticles (CT@MNPs or CT@Fe₃O₄ nanoparticles) from water resources was studied. From pH-dependent experiments, the maximum adsorption efficiency was found to be at pH 8. Isotherm and kinetic studies were performed and found to follow Langmuir isotherm and pseudo-second order kinetics, respectively. The maximum adsorption capacity of CT@MNPs was calculated to be 45.5 mg of U(vi) per g of nanoparticles (NPs). Recyclability studies suggest that over 94% sorption was retained even after four consecutive cycles. The sorption mechanism was explained by the point of the zero-charge experiment and the XPS measurement. Additionally, calculations using density functional theory (DFT) were carried out to support the experimental findings.

Low-temperature plasma induced phosphate groups onto coffee residue-derived porous carbon for efficient U(VI) extraction

For the continuous utilization of nuclear energy and efficient control of radioactive pollution, low-cost materials with high efficient U(VI) removal are of great importance. In this study, low temperature plasma method was applied for the successful modification of O-phosphorylethanolamine (O-PEA) on the porous carbon materials. The produced materials (Cafe/O-PEA) could adsorb U(VI) efficiently with the maximum sorption capacity of 648.54 mg/g at 1 hr, T=298 K, and pH=6.0, much higher than those of most carbon-based composites. U(VI) sorption was mainly controlled by strong surface complexation. From FTIR, SEM-EDS and XPS analyses, the sorption of U(VI) was related to the complexation with -NH₂, phosphate and -OH groups on Cafe/O-PEA. The low temperature plasma method was an efficient, environmentally friendly and low-cost method for surface modification of materials for the effective enrichment of U(VI) from aqueous solutions.

Application of poly(vinylphosphonic acid) modified poly(amidoxime) in uptake of uranium from seawater

To enhance the anti-biofouling properties and adsorption capability of poly(amidoxime) (PAO), vinylphosphonic acid (VPA, CH2[double bond, length as m-dash]CH-PO3H2) was polymerized on poly(acrylonitrile) (PAN) surface by plasma technique, followed by amidoximation treatment to convert the cyano group (-C[triple bond, length as m-dash]N) into an amidoxime group (AO, -C(NH2)[double bond, length as m-dash]N-OH). The obtained poly(vinylphosphonic acid)/PAO (PVPA/PAO) was used as an adsorbent in the uptake of U(vi) from seawater. The effect of environmental conditions on the anti-biofouling property and adsorption capability of PVPA/PAO for U(vi) were studied. Results show that the modified PVPA enhances the anti-biofouling properties and adsorption capability of PAO for U(vi). The adsorption process is well described by the pseudo-second-order kinetic model and reached equilibrium in 24 h. Adsorption isotherms of U(vi) on PVPA/PAO can be well fitted by the Langmuir model, and the maximum adsorption capability was calculated to be 145 mg g-1 at pH 8.2 and 298 K. Experimental results highlight the application of PVPA/PAO in the extraction of U(vi) from seawater.

Uranium sorption from waste solutions by Talc Phosphogypsum ferri-silicate synthetic new sorbent

In this investigation, a synthetic Talc Phosphogypsum ferri-silicate TPFS sorbent was prepared by thermal activation then evaluated the uranium ions removal from sulfate waste solution containing uranium. Generally, the synthetic adsorbents from raw and waste materials have a significant attention from scientists because the environmental concern and economic development, particularly, the uranium elimination from radioactive waste solutions. The uranium removal percentage and loading capacity were determined by optimization the conditions of adsorption such as the pH range, adsorbent/adsorbate ratio, uranium concentration of radioactive waste solutions, equilibrium time and temperature. The resultant adsorption efficiency and loading capacity were 87.2% and 375 mg g−1, respectively. The adsorption isothermally was in accordance with Langmuir isotherm model, in addition pseudo-second-order kinetic model, with theoretical capacity of 384.6 and 333 mg g−1, respectively. Uranium (VI) adsorption on TPFS was inhibited at elevated temperatures. The removal of uranium from sulfate waste solution by TPES sorbent according to the thermodynamic functions values was exothermic (∆H of −16.095) and non-spontaneous in nature (∆G of −17.27 at 303 K). In addition, there was a decrease in the randomness at the TPFS/uranium waste solution interface with ∆S value of 3.88.

Study on Adsorption Behavior of Nickel Ions Using Silica-Based Sandwich Layered Zirconium-Titanium Phosphate Prepared by Layer-by-Layer Grafting Method

In this study, the composite of silica-based sandwich-layered zirconium-titanium phosphate was prepared by a layer-by-layer grafting method and its adsorption properties in a diluted solution of Ni ions were specifically researched by the bath experiment method. The field-emission scanning electron microscope (FESEM) results presented the smooth surface morphology of the pristine adsorbent and a rough surface morphology of the adsorbed adsorbent and the energy dispersive analysis (EDS) results ensured the presence of the original metal element (Si, O, Ti, P, Zr) and the captured nickel element on the adsorbent. The Fourier transformed infrared spectroscopy (FTIR) revealed the new band formation of -Si-Ti-O-, -Si-Ti-O-P-, and -Si-Ti-O-P-Zr-O-, which ensured the successful modification of the silica substrate by zirconium-titanium phosphate. The specific surface area and pore size distribution analysis indicated that the pore structure was changed from type-Ⅳ to H2-type and the specific surface area (BET) of the modified composite was 337.881 m²/g. In the bath experiment, the optimal pH for adsorbing Ni ions on the composite was ~8 with the equilibrium time 30 min at room temperature and the maximum sorption amount was 50.1 mg/g. The adsorption kinetics of the sorption process were corresponded to the pseudo-second-order kinetic equation and the isothermal adsorption data were fitted well to the Redlich-Peterson Model. Thermodynamic simulation results revealed the species of Ni ions and provided a reasonable pH scope for better removal of the Ni element in wastewater.

New uranium(vi) and isothiouronium complexes: synthesis, crystal structure, spectroscopic characterization and a DFT study

U(vi) and isothiouronium salts create a strong charge-assisted network of hydrogen bonds and ionic interactions.

Fast and Selective Removal of Aqueous Uranium by a K+-Activated Robust Zeolitic Sulfide with Wide pH Resistance

For the nuclear industry, uranium is not only an important strategic resource but also a serious global contaminant with radiotoxicity and high chemotoxicity. It is very important to efficiently capture uranium from complex aqueous solutions for further treatment and disposal of nuclear wastes. Herein, we first demonstrate the suitability of a three-dimensional (3D) water-stable K⁺-exchanged zeolitic sulfide, namely K@GaSnS-1, for the remediation of radioactive and toxic uranium by ion exchange. In comparison to the pristine compound GaSnS-1, the K⁺-activated porous sulfide K@GaSnS-1 exhibits faster [UO₂]²⁺ ion uptake kinetics, following the pseudo-second-order adsorption model. Further studies indicate that K@GaSnS-1 shows high exchange capacity (q_m^U = 147.6 mg/g) and wide pH resistance (pH 2.75-10.87). In particular, it can efficiently capture [UO₂]²⁺ ion even when excessive amounts of Na⁺, K⁺, Mg²⁺, and Ca²⁺ ions are present. The highest distribution coefficient value K_d, signifying the affinity and selectivity for [UO₂]²⁺ ion, reaches as high as 1.24 × 10⁴ mL/g. More importantly, the uranium in corresponding exchanged samples can be facilely and effectively eluted by a low-cost and eco-friendly method. These merits of K@GaSnS-1 make it promising for the effective and selective removal of uranium from complex contaminated water.

The use of halloysite functionalized with isothiouronium salts as an organic/inorganic hybrid adsorbent for uranium(VI) ions removal

Elimination of U(VI) from nuclear wastes and from the underground water near the uranium mines is the serious problem. Therefore search for new sorbents for U(VI) is still a big challenge for the scientists. This paper investigates of U(VI) ions sorption on halloysite modified with the isothiouronium salts: S-dodecaneisothiouronium bromide (ligand 1), S,S'-dodecane-1,12-diylbis(isothiouronium bromide) (ligand 2), S-hexadecaneisothiouronium chloride (ligand 3), S,S'-naphthalene-1,4-diylbis(methylisothiouronium) dichloride (ligand 4), and S,S'-2,5-dimethylbenzene-1,4-diylbis(methylisothiouronium) dichloride (ligand 5). It was established that halloysite modified by the ligands with four nitrogen atoms in their structure (ligand-5, 2 and 4) was characterized by higher sorption capacity compared with that modified by the ligands with two donor nitrogens (ligand-1 and 3). The maximum sorption capacity of halloysite-5 toward U(VI) was 157 mg U/g and this places the modified mineral among the most effective sorbents for U(VI) removal from wastes. As follows from ATR, XPS and thermal degradation spectra of the sorption products [R-S-C(NH)(NH₂)]_n = 1-2(UO₂²⁺) complexes are formed on the external surface of the halloysite whereas oligomeric hydroxy complexes (UO₂)₃(OH)₅⁺ and (UO₂)₄(OH)₇⁺ are present in the interior of halloysite structure and interact predominantly with aluminols.

Synthesis, characterization and application of composite derived from rice husk ash with aluminium oxide for sorption of uranium

A composite of rice husk (RH), caustic soda and aluminium oxide was synthesized at 500°C. The activated carbon and amorphous silica dispersed over the aluminium oxide selectively adsorbed uranium in the presence of other elements. At equilibrium time 1 h, phase ratio S/L (0.1 g/10 ml), pH = 5 and uranium initial concentration 120.6 mg/l uranium adsorption efficiency was 96.35%. The uranium stripping efficiency from the load RHA–alumina composite fulfilled 99.9% at 1 h equilibrium time, a phase ratio (S/A) of 0.05 g/10 ml and 0.5 mol/l HNO3. The scanning electron microscopy photos revealed that the rice husk ash (RHA)–alumina composite has vacant or regular cavities before the adsorption, and the cavities are fully occupied by uranium after adsorption. The Fourier transform infrared spectroscopy shows a more broadening of the band υ = 3526 and 3462 cm−1 which was ascribed to the uranium adsorption. The composite adsorbed 93.75% of uranium from a waste sample. The uranium adsorption exhibited a Langmuir isotherm.

Adsorption of Uranyl Ions at the Nano-hydroxyapatite and Its Modification

Nano-hydroxyapatite and its modification, hydroxyapatite with the excess of phosphorus (P-HAP) and hydroxyapatite with the carbon ions built into the structure (C-HAP), were prepared by the wet method. They were studied by means of XRD, accelerated surface area and porosimetry (ASAP), and SEM. The size of crystallites computed using the Scherrer method was nano-hydroxyapatite (HAP) = 20 nm; P-HAP-impossible to determine; C-HAP = 22 nm; nano-HAP/U(VI) = 13.7 nm; P-HAP/U(VI)-impossible to determine, C-HAP/U(VI) = 11 nm. There were determined basic parameters characterizing the double electrical layer at the nano-HAP/electrolyte and P-HAP/electrolyte, C-HAP/electrolyte inter faces: density of the surface charge and zeta potential. The adsorption properties of nano-HAP sorbent in relation to U(VI) ions were studied by the batch technique. The adsorption processes were rapid in the first 60 min and reached the equilibrium within approximately 120 min (for P-HAP) and 300 min (for C-HAP and nano-HAP). The adsorption process fitted well with the pseudo-second-order kinetics. The Freundlich, Langmuir-Freundlich, and Dubinin-Radushkevich models of isotherms were examined for their ability to the equilibrium sorption data. The maximum adsorption capabilities (q _m ) were 7.75 g/g for P-HAP, 1.77 g/g for C-HAP, and 0.8 g/g for HAP at 293 K.

Magnesium carbonate basic coating on cotton cloth as a novel adsorbent for the removal of uranium

A magnesium carbonate basic coating on a cotton cloth was prepared by a facile and cost-effective method for uranium(vi) adsorption. The maximum adsorption capacity toward uranium is 370 mg g⁻¹, promoting a promising and effective adsorbent for practical uranium(vi) adsorption.

Dynamic immobilization of simulated radionuclide 133Cs in soil by thermal treatment/vitrification with nanometallic Ca/CaO composites

Although direct radiation induced health impacts were considered benign, soil contamination with (137)Cs, due to its long-term radiological impact (30 years half-life) and its high biological availability is of a major concern in Japan in the aftermath of the Fukushima nuclear power plant disaster. Therefore (137)Cs reduction and immobilization in contaminated soil are recognized as important problems to be solved using suitable and effective technologies. One such thermal treatment/vitrification with nanometallic Ca/CaO amendments is a promising treatment for the ultimate immobilization of simulated radionuclide (133)Cs in soil, showing low leachability and zero evaporation. Immobilization efficiencies were 88%, 95% and 96% when the (133)Cs soil was treated at 1200 °C with activated carbon, fly ash and nanometallic Ca/CaO additives. In addition, the combination of nanometallic Ca/CaO and fly ash (1:1) enhanced the immobilization efficiency to 99%, while no evaporation of (133)Cs was observed. At lower temperatures (800 °C) the leachable fraction of Cs was only 6% (94% immobilization). Through the SEM-EDS analysis, decrease in the amount of Cs mass percent detectable on soil particle surface was observed after soil vitrified with nCa/CaO + FA. The (133)Cs soil was subjected to vitrified with nCa/CaO + FA peaks related to Ca, crystalline phases (CaCO3/Ca(OH)2), wollastonite, pollucite and hematite appeared in addition to quartz, kaolinite and bentonite, which probably indicates that the main fraction of enclosed/bound materials includes Ca-associated complexes. Thus, the thermal treatment with the addition of nanometallic Ca/CaO and fly ash may be considered potentially applicable for the remediation of radioactive Cs contaminated soil at zero evaporation, relatively at low temperature.