•Nanoarchitectonics of poly(vinyl alcohol)/graphene oxide composites for U(VI) electrosorption.•Best U(VI) eletrosorption performance for PVA/GO-4 among various PVA/GO composites.•Electrical ...double-layer formation and complexation as the electrosorption mechanism.•High electrosorption capacity and fast kinetic rate for U(VI) removal using PVA/GO-4 electrode.
The radioactive pollution attributed to the discharge of uranium-containing wastewater is considered as a long-term threat to the ecological environment. Herein the nanoarchitectonics of poly (vinyl alcohol)/graphene oxide composite (PVA/GO) electrodes were performed for the efficient U(VI) electrosorption from aqueous solution. The cyclic voltammetry (CV) measurements were conducted to evaluate the capacitive characteristics of the PVA/GO electrodes. The electrosorption capability of U(VI) was significantly enhanced by electrosorption using PVA/GO electrodes. The PVA: GO mass ratios for the PVA/GO composite electrodes were optimized according to their electrosorption performance, which showed PVA/GO-4 was the best among them owing to its excellent conductivity and well-developed mesoporous structure. The electrosorption data were simulated by different models, suggesting the good-fitting of Langmuir model for the isotherms and the first-order model for the kinetics. The electrosorption capacity of U(VI) reaches 333.0 mg/g at 0.9 V. The U(VI) electrosorption mechanism related to electrical double-layer attraction and complexation was clarified by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Moreover, the electrosorption-desorption cycles suggested excellent regeneration This works highlights the promising application of PVA/GO electrodes for the efficient electrosorptive removal/separation of U(VI) from radioactive wastewater.
The low solubility and bioavailability of aqueous insoluble drugs are critical challenges in the field of pharmaceuticals that need to be overcome. Nanocrystal technology, a novel pharmacological ...route to address the poor aqueous solubility problem of many poorly soluble drugs, has recently demonstrated great potential for industrial applications and developments. This review focuses on today’s preparation technologies, containing top-down, bottom-up, and combinative technology. Among them, the highlighted combinative technology can improve the efficiency of particle size reduction and overcome the shortcomings of a single technology. Then, the characterization methods of nanocrystal production are presented in terms of particle size, morphology, structural state, and surface property. After that, we introduced performance evaluations on the stability, safety, and the in vitro/in vivo dissolution of drug nanocrystals. Finally, the applications and prospects of nanocrystals in drug development are presented. This review may provide some references for the further development and optimization of poorly soluble drug nanocrystals.
New maleic anhydride-β-cyclodextrin functionalized magnetic iron oxide nanoparticles (IONPs@MAH-β-CD) were prepared through the simple chemical coprecipitation method. Macroscopic batch experiments ...were carried out to study its absorption behavior for uranium (VI) under different environmental conditions. Using the magnetic separation technique, it was possible to easily separate IONPs@MAH-β-CD from uranium-containing wastewater. The equilibrium for uranium (VI) adsorption was reached for 180 min. The results showed that the kinetics and isotherm of the adsorption process were consistent with the pseudo-second-order kinetic model and Langmuir model, respectively, indicating that it was a chemisorption process. Compared with pure IONPs, the maximum adsorption quantity of maleic anhydride-β-cyclodextrin-coated iron oxide nanoparticles for uranium (VI) was significantly improved, which could reach 163.93 mg g−1. The recyclability of the IONPs@MAH-β-CD was investigated, and FTIR and XPS characterization were used to explore the possible mechanism of U(VI) adsorption.
In this study, nine soils at different depths in a decommissioned uranium tailing pond in Jiangxi Province are selected as the research objects to study their mineralogical properties and reveal the ...leaching law of radioactive element uranium under natural rainfall conditions. The research results are as follows: 1) The distribution characteristics of uranium are affected by the mineral composition, microscopic morphology and physical and chemical properties of uranium tailings. 2) In static leaching experiments, acidic solutions, small particles, and high solid-to-liquid ratios all promote the release of uranium. 3) In the dynamic leaching experiment, the lower the pH of simulated rainfall, the more uranium is released. According to Fick theory, the migration mechanism of uranium is mainly surface dissolution, and the release of uranium is related to the content of migratory uranium.
Low water solubility of drug products causes delivery problems such as low bioavailability. The reduced particle size and increased surface area of nanocrystals lead to the increasing of the ...dissolution rate. The formulation of drug nanocrystals is a robust approach and has been widely applied to drug delivery system (DDS) due to the significant development of nanoscience and nanotechnology. It can be used to improve drug efficacy, provide targeted delivery and minimize side-effects. Crystallization is the main and efficient unit operation to produce nanocrystals. Both traditional crystallization methods such as reactive crystallization, anti-solvent crystallization and new crystallization methods such as supercritical fluid crystallization, high-gravity controlled precipitation can be used to produce nanocrystals. The current mini-review outlines the main crystallization methods addressed in literature. The advantages and disadvantages of each method were summarized and compared.
It is a central issue to eliminate radioactive uranium (U(VI)) efficiently from water. In this manuscript, β-cyclodextrin was cross-linked with 2,3,5,6-tetrafluoro-1,4-benzenedicarbonitrile, and then ...a carboxylation reaction was used to prepare porous cross-linked polymers rich in carboxyl groups (CA-PCDPs). Subsequently, magnetic nanoparticles (MNPs) were loaded onto the CA-PCDPs via coprecipitation, and magnetic porous β-cyclodextrin polymer nanoparticles (CA-PCDP@MNPs) were successfully obtained, which were used for efficient elimination of U(VI) from nuclear wastewater solution. Moreover, SEM, FTIR, VSM, BET, and XRD were employed to investigate the CA-PCDP@MNP and found that it had a well-developed porous structure, high specific surface area, and abundant oxygen-containing functional groups (carboxyl, hydroxyl, C-O-C, Fe-O, etc.), providing sufficient active sites for chelating uranyl ions. Experiments illustrated that the CA-PCDP@MNP had efficient removal ability for U(VI), and the maximum theoretical adsorption amount for U(VI) reached 245.66 mg/g at pH 6.0 and 303 K. Moreover, the adsorption process was more suitable for the quasi second-order kinetic model and Langmuir adsorption isotherm model, indicating that the adsorption process was chemical adsorption. Meanwhile, the CA-PCDP@MNPs also exhibited fast response magnetic recovery ability and excellent regeneration and recycling ability. In addition, the data of the adsorption mechanism demonstrated that oxygen-containing functional groups, which were rich on the surface of CA-PCDP@MNPs, were the main binding active sites of U(VI). From the above results, it can be deduced that the CA-PCDP@MNP has a good application prospect in the practical application of nuclear wastewater treatment.
In order to realize sustainable development, it is beneficial to explore an appropriate process to recover the radionuclides contained in tantalum-niobium slag. By micro-mineralogical analysis and ...roasting experiments, the effect of uranium-thorium leaching from a refractory tantalum-niobium slag is investigated. The uranium and thorium content in the slag is 2.26 × 103 mg/kg and 7.84 × 103 mg/kg, which have large recovery value. As the surface area and pore size of the slag are very small, the leaching agent cannot fully penetrate the particles. Various methods of characterization are used to analyze the mineralogical properties of roasted slag at different temperatures. The leaching ratio of U-Th is 90.84% and 96.62% at the optimum roasting temperature of 500 °C, which are about 39% and 27% higher than original samples. The oxidants Fe3+, O2 and Mn can also promote the conversion of insoluble U(IV) to soluble U(VI). Roasting reduces the content of organic C and S, thereby preventing reduction of U(VI), and increasing pore size as well as specific surface area also promote radionuclide leaching. Thus, the roasting method at 500 °C can destroy the surface wrapping structure of radionuclides, reduce the internal density of minerals, and improve uranium-thorium leaching ratio significantly. It is of great practical significance to reduce the radioactive hazard of waste tantalum-niobium slag and to strengthen the sustainable utilization of resources by suitable process improvement techniques.
In recent studies, the existence of mesoscale precursors has been confirmed in crystallization. Different from the classical crystallization theory, which only considers the sequential attachment of ...basic monomers (atoms, ions, or molecules), the nonclassical crystallization process involving precursors such as prenucleation clusters, nanoparticles, and mesocrystals is more complicated. The mesoscale structure is important for the quantitative description and directional regulation of the solution crystallization process. It is necessary to explore the mechanism by the mesoscale scientific research methods on the base of traditional chemical engineering and process system engineering research methods. Therefore, the paper reviews several representative nonclassical nucleation and growth theories, mainly including two-step nucleation theory, prenucleation clusters theory, particle agglomeration theory, amorphous precursor growth theory, particle attachment growth theory and mesocrystal growth theory. Then, the mesoscale structure and its spatiotemporal dynamic behavior are discussed, and the application of the EMMS model in the nucleation and growth process is analyzed. Finally, we put forward our views on the prospect of the paradigms and theoretical innovations of using mesoscale methods in crystal nucleation and growth.
In this paper, the gel formation and its effect on the solution crystallization process of valnemulin hydrogen tartrate in a mixed solvent system were investigated. Some offline tools, such as ...differential scanning calorimetry (DSC) and X-ray powder diffraction (XRPD), and online tools, such as FBRM and PVM, were used to monitor and analyze the process. It was found that the amorphous particles of valnemulin hydrogen tartrate were first observed and then gel formation followed and finally the amorphous state particles transformed into crystalline particles. To fully understand this process, the gel formation of this compound as well as the following transformation phenomenon were investigated in detail. It was concluded that gel was temporarily formed and acted as an intermediate phase during the transformation from an amorphous state to a crystalline state.
•The solubility of valnemulin hydrogen tartrate in five pure solvents was experimentally determined.•Several solution thermodynamic properties of valnemulin hydrogen tartrate in five pure solvents ...were calculated.•The experimental solubility data were correlated by five models.
The solubility of valnemulin hydrogen tartrate in five pure solvents was determined in temperature range of 278.15K to 333.15K by using a static analytical method. Five thermodynamic models were used to correlate the experimental solubility data. The correlated results were analyzed and compared with experimental results. It was found that the correlated results were in good agreement with the experimental results. By using the Van’t Hoff equation, the dissolution enthalpy and entropy of valnemulin hydrogen tartrate in different solvents were calculated. The mixing thermodynamic properties of valnemulin hydrogen tartrate, including the mixing Gibbs energy, the mixing enthalpy and entropy, as well as the infinite-dilution activity coefficient and the excess enthalpy, were determined by using the Wilson model and the experimental solubility data.
