查看更多>>摘要：Barium tungstate is one of the important components of complex tungsten minerals and is also an intermediate product of hydrometallurgy. Since it is thermodynamically a very stable mineral, most of the current tungsten ore leaching methods are ineffective for its processing. In addition, due to the high toxicity of barium ions, special attention must be paid during the leaching process. In order to solve these problems, a new method of using sodium sulfate to decompose barium tungstate is proposed in this article. A thermodynamic analysis of the Ba~(2+)-SO_4~(2+)-WO_4~(2-)-H2O system is carried out, in which the changes of various ions and precipitations at different pH values and different amounts of sodium sulfate were explored. Moreover, this method is theoretically proved to be feasible. Also, the leaching of barium tungstate experiment was carried out. Under optimum conditions with liquid/solid ratio 10:1 mL/g, reaction temperature 75 °C, and Na2SO4 dosage 2.5-3.0 M times to BaWO4, the leaching rate of barium tungstate was >99%. This method has the advantages of simplicity, and high leaching rate, and it is cost effective with no barium toxicity.
查看更多>>摘要：The continuous extraction of an amino acid from an aqueous solution into an ionic liquid phase was studied experimentally in small channels, demonstrating a double intensification of the solvent used and the overall process. Channels with 0.5, 1 and 2 mm internal diameter were used for the extraction of the amino acid, L-tryptophan from an aqueous solution (0.005 mol L~(-1)), into a hydrophobic ionic liquid, 1-Butyl-3-methylimida-zolium Bis (trifluoromethanesulfonyl)imide, [C4mim] [Tf2N] in the presence of a crown ether extractant , Dicyclohexano-18-crown-6, (DC18C6). A mechanism was proposed for the extraction which involved the ammonium centre of the amino acid forming hydrogen bonds with the 18~crown-6 part of the extractant at a 1:1 ratio. Partition coefficients up to 25 were obtained. The continuous extraction experiments were carried out during plug flow where the interfacial areas reported reached up to 5500 m~2m~(-3) at 50% volume fractions. Extraction efficiencies up to 90% were obtained for residence times less than 30 s. Overall mass transfer coefficients (K_La) found reached up to 0.14 s~(-1).
Heyder Pereira NevesGabriel Max Dias FerreiraGuilherme Max Dias Ferreira
19页
查看更多>>摘要：The rare earth elements, a group of metals consisting of the lanthanide series, together with yttrium and scandium, are increasingly important in high technology industries worldwide. Given the need to expand production of these elements, there is a search for processes to obtain them that are less environmentally damaging, since the rare earths production chain is associated with several environmental problems and concerns. Solvent extraction, one of the important steps involved in the obtaining of rare earth elements, is receiving much attention in the scientific and industrial community, with a renewed search for approaches that avoid the use of organic solvents. Among the various options, cloud point extraction and the use of aqueous two-phase systems are alternatives to the use of traditional organic solvents. This review considers these two more environmentally friendly techniques and their use for the extraction and/or separation of rare earth elements. The issues addressed include their potential to replace traditional liquid-liquid extraction, in terms of the efficiency, toxicity, and biodegradability of the components forming the systems, as well as their potential applications and future perspectives.
查看更多>>摘要：Recycling and utilization of metal resources in extracted vanadium residue can effectively alleviate resource shortage and environmental pollution problems. In this work, a closed-loop recovery process of Fe and Ti from | extracted vanadium residue with ammonium sulfate as a roasting additive is proposed. The results show that the acidifier-ammonium bisulfate produced during the roasting process of ammonium sulfate can significantly reduce the roasting temperature. Under the optimal process conditions, 96.91% Fe and 27.33% Ti are leached, and 81.79% Fe is recovered in the form of ammonium jarosite. Ti-doped LiFePCVC is prepared by solid-state synthesis with ammonium jarosite as Fe source, and the initial discharge specific capacity of the LiFePCVC reached 141.6 mAh·g~(-1) at 0.1C. The waste residue after recovering Fe and Ti from extracted vanadium residue is a high-quality raw material for preparing petroleum proppant, and the ammonium sulfate generated during the roasting process can also be recycled. The closed-loop process proposed in this study not only avoids the use of a large number of strong acids but also realizes the full utilization of extracted vanadium residue, improves the utilization rate of mineral resources, reduces environmental pollution, which has important reference significance for the high-value utilization of similar metallurgical waste slag.
查看更多>>摘要：The authors regret that in the above paper, Fig. 2(a), Fig. 3(d, f), Fig. 6(b), Fig. 7(c), and Table 1 are mistaken. Therefore, new analyses were provided as follows:The XPS of O 1s at 531.60 and 529.9 eV (Fig. 3d) are assigned to the hydroxyl group and lattice oxygen, respectively. The peaks at 288.5 and 284.9 eV in Cls spectrum (Fig. 3f) are related to the C=O and C-C groups from Cdots.
查看更多>>摘要：Efficient trap of polar aromatic amines (AAs) is challenging due to their high water-solubility. In this study, electroenhanced solid phase microextraction (EE-SPME) based on porous monolith doped with carboxylic carbon nanotubes (M@CCNs) was developed for the first time to efficiently capture AAs at trace levels in water samples, According to the chemical features of studied AAs, poly (l-vinyl-3-octylimidazolium tetrafluoroborate-co-divinylbenzene) monolith mingled with M@CCNs was fabricated on the surface of stainless steel wire and utilized as the extraction medium of EE-SPME. Results well evidenced that the introduction of carboxylic carbon nanotubes not only enhanced the surface area of monolith, but also introduced carboxyl group into the adsorbent. The implement of electric field during extraction process improved the trap performance, the extraction efficiencies increased by 36-48% compared with without application of electric field. The practicability and reliability of M@CCNs/EE-SPME was demonstrated by combining high-performance liquid chromatography with diode-array detector to quantify studied AAs in various water samples. The limits of detection and limits of quantification located at the ranges of 0.0013-0.012 ug/L and 0.0042-0.040 μg/L, respectively. The recoveries with different fortified concentrations were in the range of 83.1-118%. In addition, related extraction mechanism of M@CCNs/EE-SPME towards studied AAs was deduced.
查看更多>>摘要：In this study, a novel Fe/Co bimetallic spinel sulfide (FeCo2S4) modified g-C3N4 composite (FeCo2S4-CN) was prepared by a hydrothermal method and firstly applied as a catalyst for the activation of peracetic acid (PAA) at neutral pH. The efficient rhodamine B (RhB) degradation in FeCo2S4-CN/PAA system indicated that PAA was successfully activated by FeCo2S4-GN. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) results indicated that g-CsN4 carrier could anchor FeCo2S4 particles with good dispersion. The X-ray photo-electron spectroscopy (XPS) analysis suggested that the surface sCo(II) and =Fe(II) could activate PAA to form CH3C(O)O· and ·OH, synchronously yielding =Co(III) and =Fe(III). Meanwhile, the surface ≡Co(III) and ≡Fe(III) could also react with PAA to generate GH3C(O)OO~· as well as ≡Co(II) and ≡Fe(II), resulting in the redox cycles of ≡Co(II)/≡Co(III) and ≡Fe(II)/≡Fe(III). Besides, the presence of S~(2-) in FeCo2S4-CN was favorable to these redox cycles. Radical scavenging experiments confirmed that organic radicals (i.e., CH3C(O)O~· and CH3C(O)OO~·) were the primary reactive species for RhB degradation in FeCo2S4-CN/PAA system. This system also exhibited a high removal efficiency for various organic contaminants, suggesting its potential application in degrading refractory pollutants.
查看更多>>摘要：MXenes have emerged as a superlative contestant water purification technology due to their two-dimensional multilayered structures, multifarious chemical composition, photocatalytic properties, and activated metallic hydroxide sites. The explosion of publications on MXenes results in (>4380 articles) with the tide ''MXenes'' according to the Web of Science (as of Nov. 16th, 2021), so it is essential to provide timely updates of this field with particular emphasis on MXenes in dye removal/degradation/adsorption that is rarely reported. This review emphasizes the rational design of MXenes-based composites, membranes, sorbents, photo-catalysts, and electrodes for dyes removal/adsorption/degradation supported by several mechanisms. The comparison between MXenes and other materials is also highlighted for the sustainable development of the water purification system along with the life cycle assessment of MXenes and their cytotoxicity and potential for large-scale applications. However, there are current challenges and prospects on MXenes that must be mitigated to endorse their practical utilization in sustainable future societies.
查看更多>>摘要：Composite hydrophobic PFPE/PVDF membranes were prepared by coating and UV-curing for vacuum membrane distillation (VMD). The water contact angle of PFPE/PVDF membrane reached 162.6°, while the decrease in pore size in comparison to the original membrane was insignificant. The effects of organic and inorganic foulants (including humic acid, sodium silicate and calcium carbonate) on membrane performance were investigated. As for this PFPE coating layer, it had an active mitigation effect on the scaling behavior and almost no membrane wetting occurred. In particular, the organic migration across the membrane was completely prevented. Then the membrane cleaning process was conducted to prove the stability under long-term operation of composite membranes when deionized (DI) water was used as cleaning agent after repeated cycles of VMD treatment of 2 M NaCl feed solutions containing 200 mg/L humic acid (HA). The results of a 30-h test indicate that the salt rejection was kept at a high level, exceeding 99.99% and the recovery of MD flux was around 90% of the initial flux after the second cleaning cycle. The promising anti-fouling and anti-wetting performance of the composite PFPE/PVDF membranes provides a high potential for further development of these membranes for membrane distillation and membrane crystallization applications.
查看更多>>摘要：Ultrafiltration (UF) has been extensively employed in current water treatment practice, during which limited removal for soluble contaminants and membrane fouling remain two perennial hurdles to efficient operation. This study proposed a promising approach by simultaneous coupling of fluidized granular activated carbon (GAC) and PAC with UF process, whereby PAC was responsible for improving effluent quality, and fluidized GAC was targeted for mitigating UF fouling and PAC deposition. The operational performance of such integrated GAC-PAC-UF system was systemically evaluated in a lab-scale setup. The results showed that fluidized GAC particles with larger size appeared highly effective in removing PAC deposition and fouling formed by surface water. PAC addition improved the effluent quality mainly by adsorbing humic acid-like substances. More importantly, energy consumption by GAC fluidization was found to be at least an order-of-magnitude lower than conventional fouling control methods employed in UF. Furthermore, redundancy analysis revealed that the key mechanism for UF fouling mitigation was tied to GAC particle momentum, whereas inorganic fouling mitigation was mostly achieved by GAC-induced liquid turbulence. It is expected that such integrated GAC-PAC-UF process proposed should be technically feasible and economically viable, potentially achieving high permeate quality and reducing membrane fouling with limited energy requirement.
NSTL