查看更多>>摘要：Solvent extraction of phosphoric acid from wet process phosphoric acid produced by decomposing low grade phosphate with hydrochloric acid was investigated by the mixture of n-butanol (nBA) and isopropyl ether (iPE). The experimental results show that the mixture has good performance on P2O5 extraction and Ca2+ purification from HCl-route wet-process phosphoric acid. Optimization of extraction process shows that nBA has good performance for H3PO4 separation at the condition of 5:1 O/A phase ratio, 293 K extraction temperature, 9:1 VB/VE ratio and 15 min extraction time. Based on the Van't Hoff equation, the enthalpy changes of P2O5 extraction was calculated to be -16.41 kJ.mol- 1. The results from liquid-liquid mass transfer show three stages can achieved about 90 wt% P2O5 extraction regardless of the countercurrent and cocurrent extraction. And the relation of total extraction percent and cross-flow extraction stages for all tested components were summarized. Moreover, the extraction mechanism between H3PO4 and nBA was discussed by researching the extraction equilibrium under different conditions. The result showed that phosphoric acid was extracted in the form of H3PO4nBA, H3PO42 nBA and H3PO43 nBA complexes. Stripping operations using Deionized water as a extractant for phosphoric acid was also investigated at different conditions.
查看更多>>摘要：Developing new and efficient methods as an alternative to hemodialysis is important due to the challenges associated with poor efficiency of membranes and long dialysis sessions. Recently, metal organic frameworks (MOFs) have attracted interest in the membrane community due to their tunable physical and chemical properties. However, their potential in uremic toxin separations is still unknown and it is not practical to test each synthesized MOF for uremic toxin separations. The main objective of this study is to computationally assess membrane-based uremic toxin separation performances of 60 bio-compatible MOFs (bio-MOFs). Combining grand canonical Monte Carlo (GCMC) and equilibrium molecular dynamics (EMD) simulations, we predicted urea, creatinine, and water permeabilities of bio-MOFs and their membrane selectivities for urea/water and creatinine/water separations. Results showed that OREZES, a carboxylate-based MOF exhibited the highest membrane selectivity (347.94) for urea/water separation whereas BEPPIX, an amino-based MOF gave the highest creatinine/water selectivity (1.5 x 105) at infinite dilution and 310 K. Guest-guest and host-guest interaction energies for uremic toxins were also computed during EMD simulations and van der Waals interactions were found to be much stronger than the coulombic interactions. We finally examined the effect of MOF's flexibility on the predicted membrane performance and membrane selectivities of bio-MOFs for urea/ water separation significantly enhanced when the structural flexibility was considered in simulations. Our results will be a guide for further studies to design novel bio-MOF membranes for uremic toxin separations.
查看更多>>摘要：Pyroprocessing technology with molten salt electrolysis as the core is a promising technology for the reprocessing of spent fuel. In this work, the electrochemical reduction mechanism and kinetic properties of Nd3+ on various electrodes (inert W and reactive Al, Ga, Bi, Cd, Zn, Pb, and Sn electrodes) were systematically investigated and compared in LiCl-KCl eutectic melts using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and Tafel techniques. The electrochemical reduction of Nd3+ was a two-step process on the W electrode including Nd3+-> Nd2+ and Nd2+-> Nd, while it became a one-step process involving three electrons on the reactive electrodes with obvious depolarization effects. Furthermore, the connections between the reduction potentials of Nd3+ on these reactive cathodes and the formation energies of the electrode-rich alloy phases (Al11Nd3, Cd11Nd, Pb3Nd, Zn17Nd2, Ga6Nd, Sn3Nd, BiNd2) were established. After evaluating the physico-chemical, depolarization and kinetic properties of these reactive electrodes, liquid Cd was considered as the most favorable material for the electrochemical extraction of Nd. In addition, Al, Cd, and Bi are also promising candidates for An / Ln separation.
查看更多>>摘要：Activation of peracetic acid (PAA) for pollutants degradation has been a hotspot recently. In this study, mo-lybdenum disulfide (MoS2) was first employed to enhance sulfamethoxazole (SMX) degradation in the Fe(III)/ PAA process at pH 3.0. The addition of MoS2 can not only accelerate the transformation from Fe(III) to Fe(II), but also can directly activate PAA. A series of reactive species including Fe(IV), O-1(2), HO center dot, CH3C(O)O-center dot and CH3C(O) OO center dot were generated in this Fe(III)/MoS2/PAA process, which was responsible for SMX degradation except O-1(2). The increase of MoS2 dosage (0.025-0.2 g/L) accelerated SMX degradation, and the optimum pH was 3.0. The increase of either PAA (0.075-0.45 mM) or Fe(III) concentration (0.025-0.2 mM) also accelerated SMX degra-dation. However, the higher concentration of SMX, the addition of humic acid, and extra adding H2O2 lowered the removal efficiency of SMX. Based on the identified products, possible pathways of SMX degradation initiated by electron transfer reaction were proposed. Furthermore, a continuous flow reactor configuration was employed to recycle the used MoS2, and the stable removal efficiency of SMX during 6 h reaction brings a new strategy for this process in practical use. This study developed an efficient method to remove SMX and provided a new idea for the PAA activation in water treatment.
查看更多>>摘要：The MgAl2O4 nanoparticles with different particle sizes prepared by a polyacrylamide gel method with different metal salts as raw materials which was used to study its efficiency as an adsorbent for removal of Congo red, acid orange 7 and acid fuchsin from wastewater. It was difficult to obtain pure MgAl2O4 nanoparticles with basic magnesium carbonate or aluminum acetate coupled with other metal salts. Based on the molecular weight, coordination number, ion radius and the number of water of crystallization for the metal salt and the phase purity of the target product, a neural network prediction model was established to predict the effect of synthesis parameters on the phase purity of MgAl2O4. The microstructure characterization confirmed that the minimum particle size of MgAl2O4 nanoparticles prepared with aluminum nitrate and magnesium sulfate as metal salts was about 22 nm, and the maximum particle size of MgAl2O4 nanoparticles prepared with aluminum nitrate and magnesium chloride as metal salts was about 50 nm. Adsorption experiments of MgAl2O4 nanoparticles were performed as a function of process parameters: various dyes including Congo red, acid orange 7 and acid fuchsin, adsorption time, particles size, initial dye concentration, initial adsorbent concentration, pH value and reaction temperature. The thermodynamic studies showed that the adsorption of MgAl2O4 nanoparticles for removal of Congo red from wastewater is an exothermic and spontaneous process. The maximum adsorption capacity of 89.043 mg/g for the MgAl2O4 nanoparticles was found at 1 g/L of initial adsorbent concentration, 100 mg/L of initial dye concentration, 6.9 of pH, and 299.8 K of temperature for removal of Congo red from wastewater. The adsorption of Congo red, acid orange 7 and acid fuchsin can be assigned to the synergistic effect of electrostatic interaction, pore filling and ion exchange. This present work provides a technical reference for the synthesis of other metal oxide nanoparticles using metal salts with different acid groups.
查看更多>>摘要：The construction of dual Z-scheme photocatalysts is an effective way to promote the separation and migration of electrons-holes as well as retain their high redox abilities. Herein, a distinctive dual Z-scheme photocatalyst based on phase junction WO3 and CdS (CW) was successfully fabricated via hydrothermal method and in-situ precipitation process. The as-prepared materials showed the advantages of both phase junction and dual Z-scheme mechanism (promoted utilization of carriers and improved redox potential). As a result, the k(app) value of 75CW (0.05237 min(-1)) was 29.8 times that of phase junction WO3 (0.00176 min(-1)) and 2.9 times that of CdS (0.01799 min(-1)) in terms of imidacloprid (IMD) degradation. Trapping experiment and electron spin resonance (ESR) proved the dual Z-scheme mechanism, the key to significantly improve photocatalytic degradation efficiency of WO3/CdS nanocomposites. Combined the analysis of liquid chromatography-mass spectrometry (LC-MS) with density functional theory (DFT) calculation, rational degradation pathways of IMD were put forward in detail. This work is excepted to provide new horizons for the construction of dual Z-scheme system with phase junction and the photodegradation of IMD.
查看更多>>摘要：While CeO2 is a promising catalyst for soot elimination, it is essential to develop CeO2 with higher contact areas, and reactivity for effective soot oxidation as catalytic soot oxidation is dominantly controlled by structures, and surficial properties of catalysts. In this study, a Ce-Metal organic frameworks (MOFs) consisting of Ce and trimesic acid (TA) is employed as the precursor as CeTA exhibits a unique broccoli-like hierachitecture which is transformed into CeO2 with a hierarchical structure consisting of nanofibers of CeO2 bundled together, forming a broccoli-like CeO 2 nanostructure. More importantly, these CeO2 nanofibers in this broccoli-like CeO2 (BCL-CeO2) possesses porous structures, and also more oxygen vacancies, enabling BCL-CeO2 to become a promising catalyst for soot oxidation. Thus, BCL-CeO2 shows a much higher catalytic activity than commercial CeO2 nanoparticle (com-CeO2) for soot oxidation with a significantly lower ignition temperature (T-ig). More importantly, while soot oxidation by com-CeO2 leads to production of CO together with CO 2 , BCL-CeO2 can completely convert soot to CO2. The tight contact mode also enables BCL-CeO2 to exhibit a very low T-ig of 295 degrees C, whereas the existence of NO and H2O also enhances the soot oxidation by BCL-CeO2 to reduce the T-ig. The mechanism of NO-assisted soot oxidation is also examined, and validated by DRIFTS to identify the presence and transformation of nitrogencontaining intermediates. BCL-CeO2 is also recyclable over many consecutive cycles and maintained its high catalytic activity for soot oxidation. These results demonstrate that BCL-CeO2 is a promising and easily-prepared hierarchitectured Ce-based catalyst for soot oxidation.
查看更多>>摘要：Willow gentian (Gentiana asclepiadea L., Gentianaceae) is a medicinal plant that is primarily used in the treat-ment of gastrointestinal and liver diseases in folk medicine. As a bitter raw material, it is also used in the food industry for liquors flavoring. In order to optimize the ultrasound-assisted extraction (UAE) of gentiopicroside, isovitexin, isoorientin, and isogentisin, as well as total polyphenols from the underground parts of willow gentian, the influence of process parameters was investigated. Extraction time (from 5 to 65 min), ethanol concentration (from 10 to 90% v/v), solid to liquid ratio (from 1:10 to 1:50 w/v), and extraction temperature (from 20 to 80 degrees C) were estimated at five levels as independent variables. The response surface methodology (RSM) and the artificial neural network (ANN) approach were employed to develop a predictive extraction model and to establish optimal extraction conditions to simultaneously maximize the extraction yield of all target compounds. Established optimal values of process parameters were: extraction time 50 min, ethanol concen-tration 53% (v/v), solid to liquid ratio 1:40 (w/v), and extraction temperature 65 degrees C. The obtained extraction yields under predicted optimal conditions for gentiopicroside (49.23 mg/g DW), isoorientin (1.00 mg/g DW), isovitexin (4.04 mg/g DW), isogentisin (1.14 mg/g DW), and TPC (10.03 mg of GAE/g DW) confirmed the adequacy of both RSM and ANN models. Compared with the RSM model, the ANN model fitted better with the experimental values of each compound (higher coefficient of determination and lower mean absolute deviation) indicating its higher predictive capacity. The developed high-accuracy extraction model provides the basis for further separation and purification, as well as for studying the bioactivity of selected compounds from under -ground parts of G. asclepiadea.
查看更多>>摘要：Photo-responsive ZnS nanostructures (ZnSM1 and ZnSM2) were synthesized using 3-mercaptopropionic acid (MPA) and polyvinylpyrrolidone (PVP) capping agents respectively via reflux method. Capped photocatalysts hold unique optical properties such as absorption in visible region, multi band gap values and surface defects. Interestingly, structural analysis revealed that nanorods and nanospheres were formed with MPA and PVP whereas randomly arranged particles were formed without using any capping agent (ZnSUC). The successful passivation of -COOH (1549 cm(-1) and 1357 cm(-1)) in case of ZnSM1 whereas -CH2 (1284 cm(-1)) and C-N stretching (1429 cm(-1)) for ZnSM2 was determined by FT-IR studies. Owing to effective charge separation, 1D structure, suitable band gap energies and higher surface area (252 m(2) g(-1)), ZnSM1 exhibited enhanced photocatalytic activity towards crystal violet degradation (CV, 93%) under UV light which was about two folds higher than standard ZnS. Under sunlight, uncapped ZnS nanoparticles (ZnSUC and std. ZnS) showed minor activity in comparison to capped ZnSM1 (88%) and ZnSM2 (77%). Moreover, 83% degradation of 2-nitrophenol (NP) was obtained using ZnSM1 without using any other reducing agent under solar irradiations. Thus, present work provides more insights to understand the outstanding activity of ZnS nanomaterials towards organic pollutants beyond UV region without metal deposition.
查看更多>>摘要：Flow-electrode capacitive deionization (FCDI) is a special type of CDI, flowable slurry is used as the flow electrode instead of the fixed electrode. Compared to fixed-electrode CDI, FCDI has the advantage of unlimited desalination capacity, continuous desalination, and easy scale upgrade. Thus, FCDI has attracted the interest of many scholars. In this review, we summarize and compare the progress of FCDI researches in terms of the perspective of the design of FCDI cell structure, operating mode of FCDI, the component of flow phase and environmental applications. Finally, some possible problems of the current stage of FCDI technology are presented and the future direction of FCDI is outlined.
NSTL
Elsevier