查看更多>>摘要：Silica aerogel and Fe doped silica aerogel composite were synthesized by sol-gel method adopting ambient pressure drying method. The crystal structure, surface morphology, pore structure, surface functional groups and elemental composition of silica aerogel prepared with different concentrations of Fe3+ were characterized by XRD, SEM, TEM, BET, FTIR, XPS and Zeta potential analysis. The specific surface area of the composite aerogel was found to decrease with the increase addition amount of FeCl3. The optimal composite aerogel adsorbent had a surface area of 240 m(2)/g with well-developed mesoporous network, which possessed a maximum malachite green(MG) adsorption capacity of 1592 mg/g, as compared to virgin silica aerogel of 1250 mg/g. Adsorption capacity for large molecules like MG is very low for the most popular adsorbent such as high surface area activated carbon, which is usually the first-choice adsorbent for wastewater treatment. Such high adsorption capacitiy of the silica aerogel composite is highly promising as it is on the classification of low-cost adsorbents, which can serve to be far better alternative for waste water treatment applications.
查看更多>>摘要：Natural gas purification by economic and low-energy adsorptive separation processes is important. However, as a difficult global problem, N-2 removal from N-2/CH4 mixtures is challenging because of their similar physical properties. In this study, the separation of N-2/CH4 by Cr-metal-organic frameworks (MOFs) (MIL-100Cr, MIL-101Cr and TYUT-96Cr) with various open Cr site densities was studied. Gas sorption isotherms showed that TYUT-96Cr exhibited the highest N-2/CH4 uptake ratio (13.67 at 0.01 bar and 298 K) of the selected Cr-MOFs, which was consistent with the highest density of Cr (III) sites. This material provided the highest CH4 productivity (0.716 mmol/cm(3)) per cycle for N-2 removal from a 5:95 N-2/CH4 mixture to produce 99.99% pure CH4, as shown by the breakthrough experiments. Pressure-swing adsorption simulations indicated that, by a two-bed sixstep method, pristine 95% methane was enriched to 98.9% by TYUT-96Cr. The largest CH4 productivity, high breakthrough selectivity and thermal stability of TYUT-96Cr among the Cr-MOFs, made it a promising adsorbent in trace N-2 removal for practical industrial application.
查看更多>>摘要：Herein, the tungsten carbide (W2C) coated with the ultrathin carbon layer (W2C@C) was firstly exploited as an efficient and stable oxidative desulfurization (ODS) catalyst, which was prepared via annealing metallophthalocyanine/phosphotungstic acid composites at 800 degrees C under N-2 atmosphere. The Zn element in precursor markedly promoted the formation of the pure-phase W2C during annealing process. W2C@C showed a remarkable ODS performance with H2O2 as oxidant under mild conditions. Dibenzothiophene (DBT) was100% removed by W2C@C within 40 min at 50 degrees C. The density functional theory (DFT) calculations combined with the radical scavenging experiments suggest that the ODS over W2C@C follows a non-radical mechanism that involves the facile formation of surface active oxygen species. Moreover, the W2C@C catalyst could be easily regenerated by solvent washing and recycled with no obvious loss of performance. Therefore, W2C could be firstly suggested as a promising catalyst for the ODS of liquid fuels.
查看更多>>摘要：The present work investigates various swirl flow motions for the cavitation characteristics through numerical simulation of the four-phase cavitating flow in a Venturi tube. A three-dimensional Eulerian-Eulerian approach available in a commercial CFD software was used in conjunction with the kappa - omega SST scheme and Schnerr-Sauer cavitation model adopted for solid-liquid-vapor-air flows. The results of simulations are validated against the experimental data obtained in our previous study (Shi et al., 2020). Excellent predictions of flow characteristics were obtained by various solid concentrations. The results reveal that the intense swirl motions can substantially affect the movement of cavitation bubbles and micro particles. When intensive swirl motion is imposed in the process, an efficient separation of micro particles are of significant importance A higher swirl strength is of benefit to cavitation performance and degree of protection on the inner surface of throat walls from the cavitation erosion but not solid erosion. In addition, the turbulent viscosity analysis predicts weaker turbulent viscosity ratio, resulting in higher multi-factor coupling cavitation production in the divergent region. The primary and secondary swirling re-entrant jets are identified and analyzed as well. This work illustrates main features of the swirl impact on the cavitation phenomena in four-phase flows: solid-liquid-vapor-air flows. This information can strongly support the design, optimization, and application of hydrodynamic cavitation devices in the field of separation process in industrial wastewater or sludge processing.
查看更多>>摘要：The interest in utilizing nanoemulsions in a number of industrial applications is growing rapidly because of their superiority over conventional emulsions. Therefore, the formulation of highly stable crude oil-in-water nanoemulsions with different salinity (i.e., NaCl) levels is preseented in this study. Despite the observed extreme emulsion stability, zeta potential of the nanoemulsions decreased with increasing the salt concentration as a result of the charge screening effect induced by NaCl addition. Charge screening effect and, accordingly, the weakening of the electrostatic repulsion range and strength resulted in an increase in the average droplet size and also in a wider size distribution as the salinity level in the nanoemulsions increased. Additionally, the nanoemulsion viscosity also increased with increasing the salt concentration, however, the increase was marginal (except at 20 g/L NaCl). One interesting and unprecedented observation reported herein is the change in the nanoemulsion flow behavior from shear-thinning to Newtonian and then to shear-thickening as the applied shear rate increased. Nonetheless, at a salt concentration of 20 g/L NaCl, the shear-thickening behavior disappeared. Another important finding is that the presence of NaCl made the on-purpose destabilization of these stable nanoemulsions through the addition of NaOH or HCl (i.e., pH-alteration induced demulsification) more effective.
查看更多>>摘要：Nanoscale zero-valent iron (nZVI) was not considered as an ideal candidate for catalytic ozonation process in aqueous media because of its drawbacks of rapid passivation, self-agglomeration and consequent loss of reactivity. In this study, a novel disilicate-modified nZVI (Si-nZVI) material, was prepared through a liquid-phase reducing method with hydrosoluble disilicate as a modifier. The optimal Si-nZVI catalyst (Si15-nZVI), with negligible iron leaching and a good tolerance in ozone water, showed favorable water-dispersibility to achieve a highly efficient ozonation catalysis for removing quinoline (91.9% removal efficiency). Compared to the nZVI, the Si-nZVI displayed satisfactory catalytic stability and benign reusability as well. It was revealed that -[Si-O-Fe]-OH groups on Si15-nZVI, as the dominating active centers, played an essential role to boost the adsorption and catalytic decomposition of O-3 in aqueous solution. This study demonstrates the suitability of SinZVI to catalytic ozonation process, and provides a prospective oxidation technology for decontamination.
查看更多>>摘要：Persulfate (PDS) activation is an effective approach for removing organic pollutants from industrial wastewater, but a more cost-effective catalyst is required. In this study, novel iron-carbon (Fe-C) granules were successfully prepared by a facile calcination method and were applied to PDS activation. Radical quenching experiments, electron spin resonance spectroscopy, and electrochemical analyses were performed to investigate the removal efficiency of methyl orange (MO) by the Fe-C/PDS process and the effects of influencing factors such as the Fe-C dosage, PDS concentration, initial pH, and MO concentration. Fe-C was observed to have a pore structure and abundant functional groups that are beneficial for PDS activation and pollutant removal. The MO removal mechanisms of the Fe-C/PDS process included adsorption, degradation, and co-precipitation, among which the degradation process consisted of radical and non-radical pathways involving the formation of SO4-center dot, (OH)-O-center dot, O-2(-center dot), and O-1(2) as well as electron transfer. Calculations based on density functional theory were used to propose potential degradation pathways of MO. The Fe-C/PDS process exhibited high adaptability to inorganic anions and natural organic matter in aquatic environments and high removal efficiencies of various organic pollutants.
查看更多>>摘要：Ultrasmall size and abundant defects are two key factors for enhancing the property of catalysts. However, how to simultaneously introduce defects and ultrasmall nanoparticles is still challenging. Herein, oxygen vacancies on confinement of ultrafine Co3O4 NPs (6-14 nm) in nitrogen-doped graphene-supported macroscopic microspheres (Co3O4@N-rGO) were firstly fabricated and its large-scale applications in peroxymonosulfate activation for eliminating pollutants. Detailed characterizations manifested that ultrafine Co3O4 allowed a higher density of active sites to be exposed, the synergy of abundant oxygen vacancies and confinement graphene-supported structure induced the interfacial mass/electron transfer. As expected, Co3O4@N-rGO achieved ultra-fast (0.453 min-1) sulfamethoxazole (SMX) degradation and 67.4 % mineralization within 10 min, which greatly outperformed that of Co3O4 NPs from ZIF-67 (0.055 min-1). Integrated with ESR and quencher experiments, electrochemical analysis and XPS spectra before and after reaction, the degradation of SMX was dominated by singlet oxygen and other ROS had an auxiliary role. Moreover, a continuous fluidized-column reactor represented a cost-effective method for large-scale industrial wastewater treatment. This work not only verified the coaction of confined and ultrasmall NPs and oxygen vacancy but also provided a generally applicable strategy, thus expanding the applicability of heterogeneous catalysts.
查看更多>>摘要：Photocatalytic fuel cell (PFC) is a novel energy conversion device that can effectively convert light into chemical energy and then electrical energy, accompanied with the pollutant purification treatment by photocatalytic technology. In this study, the synergetic photocatalytic degradation of organic dye in anode and the reduction of heavy metal Cr(VI) in cathode are carried out in an improved dual-chamber PFC device with TiO2 and core-shell structured Ag@Fe2O3 nanoparticles as photoanode and cathode materials, respectively. Among different materials, Ag@Fe2O3 shows the highest catalytic activity to the reduction of Cr(VI) with an apparent kinetic constant of 0.058 min(-1), even much better than commercial Pt foil (0.027 min(-1)). From morphology and electrical characterizations, the excellent electrical conductivity of noble metal Ag and suitable conduction band positions between TiO2 and Fe2O3 lead to a rapid and directional transfer of photoinduced electrons, and the variable valence of Fe(II)/(III) in iron oxide facilitates continuous catalytic reduction of Cr(VI) to Cr(III). Moreover, the addition of H2O2 into anode chamber can significantly accelerate the reactions and electricity output. The radical quenching tests prove that the existence of H2O2 can efficiently increase the production of photoinduced carriers, and more oxidizing species (such as O-2(-center dot) and center dot OH) can be produced from the reactions between H2O2 and photoinduced holes or electrons.
查看更多>>摘要：The presence of arsenic (As) in crude antimony trioxide (Sb2O3) impedes the Sb recovery and results in an environmental issue. Selective As removal from crude antimony trioxide would therefore enable using this residue in commercial Sb2O3 production. This work uses a nitric acid leaching method to remove As from crude antimony trioxide. Arsenic oxide and antimony oxide are respectively converted to soluble H3AsO4 and insoluble antimony(III) oxide hydroxide nitrate Sb(III)OHN during HNO3 leaching. The As content in the crude antimony trioxide decreases from 3.0 wt% to 0.4 wt%. The As removal ratio reaches 86%, while the Sb leaching ratio is limited to 0.3%, confirming the high selectivity of HNO3 leaching. The leaching residue is composed of cervantite (Sb2O4) and Sb(III)OHN. By calcining the leaching residue in the air at 200 degrees C, it can be converted to a mixture of cervantite and valentinite (Sb2O3). Finally, cervantite is decomposed above 1070 degrees C in N-2 into Sb4O6 that can be condensed as Sb2O3. A novel flowsheet is proposed for both As removal and Sb recovery from the crude antimony trioxide.
NSTL
Elsevier