Junmei Zhao

Superior Na‐Storage Performance of Low‐Temperature‐Synthesized Na3(VO1−xPO4)2F1+2x (0≤x≤1) Nanoparticles for Na‐Ion Batteries

Na-ion batteries are becoming comparable to Li-ion batteries because of their similar chemical characteristics and abundant sources of sodium. However, the materials production should be cost-effective in order to meet the demand for large-scale application. Here, a series of nanosized high-performance cathode materials, Na3(VO(1-x)PO4)2F(1+2x) (0≤x≤1), has been synthesized by a solvothermal low-temperature (60-120 °C) strategy without the use of organic ligands or surfactants. The as-synthesized Na3(VOPO4)2F nanoparticles show the best Na-storage performance reported so far in terms of both high rate capability (up to 10 C rate) and long cycle stability over 1200 cycles. To the best of our knowledge, the current developed synthetic strategy for Na3(VO(1-x)PO4)2F(1+2x) is by far one of the least expensive and energy-consuming methods, much superior to the conventional high-temperature solid-state method.

An ionic liquid-based synergistic extraction strategy for rare earths

In this work, a novel IL-based synergistic extraction system utilizing the ionic liquid tricaprylmethyl-ammonium nitrate ([A336][NO3]) and the commercial extractant di(2-ethylhexyl) 2-ethylhexyl phosphonate (DEHEHP) was developed for the extraction of rare earth (RE) nitrates. Pr(III) was used as a model RE and the effects of key factors, i.e. the ratio of [A336][NO3] to DEHEHP, the acidity of feed solutions, and the concentration of a salting-out reagent, were systematically studied. Our results demonstrate that the mixture of [A336][NO3] and DEHEHP had an obviously synergistic extraction effect for the extraction of Pr(III). The maximum synergistic enhancement coefficient of 3.44 was attained at X-A = 0.4 (v%). Alternatively, a mixture of [A336][Cl] and DEHEHP hardly extracted Pr(III) from chloride media. Moreover, we investigated the Pr(III) extraction mechanism and demonstrated that Pr(III) can be extracted as the neutral complexation species Pr(NO3)(3)center dot chi DEHEHP and the ion-type species [A336](y)center dot Pr(NO3)(3+y). These extraction processes can effectively hamper the release of organic cation-ligands into the aqueous phase. The synergistic extraction effect is mainly derived from the enhanced solubility of the extracted species in the ionic liquid phase. The extraction behaviors of Pr(III) could be properly described by Langmuir and pseudo-second-order rate equations. An increase in temperature was unfavorable for the extraction reaction but greatly improved the extraction rate. Interestingly, the mixed IL extraction system has an obviously synergistic extraction effect for light REs (LREs, La-Eu), but an anti-synergistic effect for heavy REs (HREs, Gd-Lu, Y), thus indicating that our synergistic extraction system is helpful for the separation of LREs from HREs. In addition, the high selectivity between REs and non-REs suggested that the recovery of REs from a complicated high-salt leachate could be highly possible. It demonstrates that the IL-based synergistic extraction strategy developed in this work is promising and sustainable, and as a result the development of an IL-based synergistic extraction process for the recovery of REs is straightforwardly envisaged.

Monodisperse Iron Phosphate Nanospheres: Preparation and Application in Energy Storage

An approach to synthesize monodisperse nanospheres with nanoporous structure through a solvent extraction route using an acid-base-coupled extractant has been developed. The nanospheres form through self-assembly and templating by reverse micelles in the organic solvent extraction systems. More importantly, the used extractant in this route can be recycled. The power of this approach is demonstrated by the synthesis of monodisperse iron phosphate nanospheres, exhibiting promising applications in energy storage. The synthetic parameters have been optimized. Based on this, a possible formation mechanism is also proposed. The synthetic procedure is relatively simple and could be extended to synthesize other water-insoluble inorganic metal salts.

Reduction of hexavalent chromium by Pannonibacter phragmitetus LSSE-09 coated with polyethylenimine-functionalized magnetic nanoparticles under alkaline conditions

A novel cell separation and immobilization method for Cr (VI)-reduction under alkaline conditions was developed by using superparamagnetic Fe(3)O(4) nanoparticles (NPs). The Fe(3)O(4) NPs were synthesized by coprecipitation followed by modification with sodium citrate and polyethyleneimine (PEI). The surface-modified NPs were monodispersed and the particle size was about 15 nm with a saturation magnetization of 62.3 emu/g and an isoelectric point (pI) of 11.5 at room temperature. PEI-modified Fe(3)O(4) NPs possess positive zeta potential at pH below 11.5, presumable because of the high density of amine groups in the long chains of PEI molecules on the surface. At initial pH 9.0, Pannonibacter phragmitetus LSSE-09 cells were immobilized by PEI-modified NPs via electrostatic attraction and then separated with an external magnetic field. Compared to free cells, the coated cells not only had the same Cr (VI)-reduction activity but could also be easily separated from reaction mixtures by magnetic force. In addition, the magnetically immobilized cells retained high specific Cr (VI)-reduction activity over six batch cycles. The results suggest that the magnetic cell separation technology has potential application for Cr (VI) detoxification in alkaline wastewater.

pH-regulative synthesis of Na3(VPO4)2F3 nanoflowers and their improved Na cycling stability

Na-ion batteries are becoming increasingly attractive as a low cost energy storage device. Sodium vanadium fluorophosphates have been studied extensively recently due to their high storage capacity and high discharge voltage. Shape and size often have a crucial influence over the properties. The controlling synthesis of nanoparticles with special microstructures is significant, which becomes a challenging issue and has drawn considerable attention. In this study, Na3(VPO4)2F3 nanoflowers have been synthesized via a pH-regulative low-temperature (120 °C) hydro-thermal route. In particular, it is a green route without any organic compounds involved. The hydro-thermal reaction time for the formation of Na3(VPO4)2F3 nanoflowers has also been investigated. A weak acid environment (pH = 2.60) with the possible presence of hydrogen fluoride molecules is necessary for the formation of the desired nanoflower microstructures. Compared to the nanoparticles obtained by Na2HPO4·12H2O, the as-synthesized Na3(VPO4)2F3 nanoflowers showed an excellent Na-storage performance in terms of superior cycle stability, even without any further carbon coating or high-temperature treatment.

Block copolymer micellization induced microphase mass transfer: Partition of Pd(II), Pt(IV) and Rh(III) in three-liquid-phase systems of S201–EOPO–Na2SO4–H2O

Three-liquid-phase partitioning of Pd(II), Pt(IV) and Rh(III) in systems of S201(diisoamyl sulfide)/nonane-EOPO(polyethylene oxide-polypropylene oxide random block copolymer)-Na(2)SO(4)-H(2)O was investigated. Experimental results indicated that the selective enrichment of Pd(II), Pt(IV) and Rh(III) respectively into the S201 organic top phase, EOPO-based middle phase and Na(2)SO(4) bottom phase was achieved by control over the phase behavior of the three-liquid-phase systems (TLPS). The microphase mass transfer behavior of Pt(IV), Pd(II) and Rh(III) was closely related to the micellization of EOPO molecules. A suggested micro-mechanism model and a mass transfer model describe the micellization of EOPO molecules and the effect on mass transfer of platinum ions across the microphase interfaces. The salting-out induced continuous dehydration and ordered arrangement of the hydrophilic PEO segments in amphiphilic EOPO micelle, and these are the main driving forces for mass transfer of platinum metal ions onto the exposed activity sites of the dehydrated PEO segments. The differences in microphase interfacial structure of EOPO micelles are crucial for the efficient separation between Pt(IV), Pd(II) and Rh(III).

Extraction of rare earths(III) from nitrate medium with di-(2-ethylhexyl) 2-ethylhexyl phosphonate and synergistic extraction combined with 1-phenyl-3-methyl-4-benzoy l-pyrazolone-5

Abstract The extraction of trivalent rare earths (RE) from nitrate solutions with di‐(2‐ethylhexyl) 2‐ethylhexyl phosphonate (DEHEHP, B) and synergistic extraction combined with 1‐phenyl‐3‐methyl‐4‐benzoyl ‐pyrazolone‐5 (HPMBP, HA) were investigated. The extraction distribution ratios demonstrate a distinct “tetra effect,” and Y lies between Tb and Dy when DEHEHP is used as a single extractant for RE. According to the corresponding separation factors (SF12) for adjacent pairs of rare earths, it could be concluded that DEHEHP could be employed for the separation of La from the other rare earths, and Y from light rare earths. The present work has also found that mixtures of HPMBP and DEHEHP have an evident synergistic effect for RE(III). Taking Y(III) as an example, a possible synergistic extraction mechanism is proposed. The enhancement of extraction in the binary system can be explained due to the species Y(NO3) · A2 · HA · B formed. The synergistic enhancement coefficients (R), extraction constants, formation constants and thermodynamic functions of the reaction were calculated. The extraction of heavy rare earths (HRE=Tb3+, Dy3+, Ho3+, Er3+, Tm3+, Yb3+ and Lu3+) has also been investigated using such a binary system and compared with that of Y(III). The results show that the synergistic extraction distribution ratios follow the order: The separation factors (SFRE/Y) between Y and HRE were calculated and compared with the single extraction system. The possibility of separating Y(III) from heavy rare earths is discussed according to the separation factors.

Selective adsorption–deposition of gold nanoparticles onto monodispersed hydrothermal carbon spherules: a reduction–deposition coupled mechanism

Hydrothermal carbon spherules (HCSs) can be loaded with a variety of metal nanoparticles for various applications. In this work, three types of HCSs were prepared from saccharides (mono-, di- and poly-saccharides) by a modified hydrothermal method using glucose, sucrose and starch as sources. Au nanoparticles can be deposited onto the HCSs through a regular adsorption process. For comparison, the HCSs made from mono-saccharide glucose (HCSs-M) have a higher adsorption capacity for Au(III) from aqueous acidic chloride media. The adsorption behaviors for AuCl4- by HCSs-M were systematically investigated. HCSs-M shows a high selectivity for Au(III) towards Pd(II), Pt(VI), Rh(III) and some relevant base metals such as Fe(III), Co(II), Cu(II) and Ni(II). An extra reductant glycine can not only significantly improve the adsorption capacities and selectivity, but also accelerate the adsorption rate. The Langmuir isotherm model and the 2nd-order kinetics model can properly describe the adsorption behaviors of AuCl4-. The adsorption mechanism of Au(III) by HCSs has been confirmed by XPS, XRD, TG, FTIR, SEM and TEM techniques, which demonstrate that AuCl4- deposited onto the HCSs has been reduced to Au-0. On the basis of this phenomenon, a reductiondeposition coupled mechanism has been proposed. The current research illustrates the prospect for HCSs to be used as effective adsorbents for the selective adsorption separation of Au(III) from chloride media. It also demonstrates the possibility to integrate the selective recovery of gold from complex industrial waste streams and the fabrication of functional carbon materials through loading with gold nanoparticles.

Kinetics of Cerium(IV) Extraction with DEHEHP From HNO3‐HF Medium Using a Constant Interfacial Cell with Laminar Flow

Abstract Studies of the extraction kinetics of cerium(IV) into n‐heptane solutions of di(2‐ethylhexyl)‐2‐ethylhexyl phosphonate DEHEHP from HNO3‐HF solutions have been carried out using a constant interfacial cell with laminar flow. The experimental hydrodynamic conditions were chosen so that the contribution of diffusion to the measured rate of reaction was minimized. The data were analyzed in terms of pseudo‐first order constants. The effects of the stirring rate, specific interfacial area, and temperature on the extraction rate showed that the most probable reaction zone is in the aqueous homogeneous phase. The results were compared with those of the system without HF. It was concluded that the presence of HF decreases the extraction rate of cerium. The addition of HF increases the activation energy for the forward reaction from 21.2 to 55.3 kJ/mol and for the reverse process from 57.9 to 79.0 kJ/mol. According to the experimental data correlated as a function of the concentration of the relevant species involved in the extraction reaction, the corresponding rate equation was deduced as follows: The kinetic mechanism of the extraction process was proposed taking an aqueous chemical reaction as the rate‐determining step of the overall reaction.

A phase transfer assisted solvo-thermal strategy for the synthesis of REF3 and Ln3+-doped REF3 nano-/microcrystals

Monodisperse orthorhombic-phase rare earth fluorides nano-/microcrystals with a special shape of disk-stacked cylinder have been synthesized via a facile phase transfer assisted solvo-thermal route, where an acid-base-coupled extractant has been employed to transfer hydrofluoric acid into an oil phase as a fluoride source. The synthetic parameters have been optimized and a possible formation mechanism has also been proposed. More importantly, the adopted acid-base-coupled extractant in this route can be recycled. Surveying all of the lanthanides from La to Lu, most of the heavy rare earths, such as Tb, Dy, Ho, Er, Tm and Yb, can form LnF3 nanocrystals with the similar morphologies. Furthermore, Ln(3+)-doped YF3 (Ln=Tb, Yb/Er) nanocrystals have also been synthesized, and their down-conversion and up-conversion (980 nm) luminescent properties were examined. The current approach could be extended to synthesize other metal fluorides nanoparticles.