查看更多>>摘要：? 2021This study attempts to clarify the correlation between the structural parameters of vortex finders (diameter ratio and insertion depth) and the strong turbulent flow field and performance of cyclone separators. To elucidate the effects due to the overflow pipe diameter, insertion depth, and Reynolds number on the tangential velocity index (n) and separation efficiency, 0.3D, 0.4D, 0.5D, 0.6D, and 0.7D (where D is the diameter of the cyclone separator's cylindrical section) were selected as the vortex finder diameter and insertion depth, which were studied using three methods: computational fluid dynamics (CFD) software Fluent, experiments, and artificial neural network simulations. With Fluent, the Reynolds stress model (RSM) of turbulence was adopted to describe transport equations, and the discrete phase model (DPM) for two-phase flow was used to calculate the efficiency and separate particles at different inlet velocities. Experiments were conducted to measure the operational pressure drop and separation efficiency of the system; subsequently, the results were used to validate the CFD calculation results. Finally, a 5–5-1 three-layer artificial neural network was established based on 336 sets of data for values of n obtained from numerical simulations. In addition, a backpropagation (BP) artificial neural network model was employed to predict the correlation between the structural and operational parameters of the cyclone separator and n values. The obtained results indicate that the BP artificial neural network can accurately predict the distribution of n values within the flow field of the cyclone. Increasing the diameter of the vortex finder with the same inlet velocity can reduce the total pressure drop due to the cyclone, thereby reducing the kinetic energy loss and improving the separation efficiency of fine particles. Increasing the insertion depth of the vortex finder leads to an increase in the values of n. Considering the stability of the flow field structure and energy dissipation, an S/D value between 0.5 and 0.6 is preferred.
查看更多>>摘要：? 2022 Elsevier B.V.The Si-O-Si moiety present in low-cost, easy-to-prepare geopolymers forms a part of the skeletal structure and does not participate in adsorption. In this work, a novel composite adsorbent (SGM-MDTC) was synthesized by grafting macromolecular dithiocarbamate (MDTC) on slag-based geopolymer microspheres (SGM), and the Si–O–Si in SGM was activated to enhance the Cd(II) adsorption performance of the geopolymer adsorbent. The SGM-MDTC was synthesized successfully and characterized using the XRD and FT-IR techniques. The Si-O-Si unit present in SGM was activated after anchoring MDTC. The activation was confirmed using the XPS technique. It was observed that the morphology of SGM and SGM-MDTC changed significantly, and the specific surface area of SGM increased from 52.99 to 72.36 m2/g following the process of MDTC anchoring. The effects of pH, the dosage of SGM-MDTC, contact time, and initial concentration during static adsorption on the adsorption performance of Cd(II) on SGM-MDTC were studied. It was observed that the process followed the pseudo-second-order kinetics, Langmuir, and Sip models and was primarily controlled by the process of intra-particle diffusion. The adsorption capacity of the synthesized SGM-MDTC (205.8 mg/g) material was nearly twice as high as that of SGM (106.7 mg/g) under conditions of static adsorption. Dynamic adsorption is more suitable for practical application than static adsorption. The adsorption capacity of SGM-MDTC was as high as 382.8 mg/g. This revealed that the synthesized SGM-MDTC material exhibited excellent Cd(II) purification performance and high application value.
查看更多>>摘要：? 2022 Elsevier B.V.Dye pollutants in various water resources have brought about severe damages to individuals’ health. To attenuate the adverse effects on human beings, we design a novel composite based on graphene oxide and molecular sieve 4A (GO/4A) towards efficient removal of Rhodamine B (RB) in aqueous solutions. The adsorption properties were tested via adjusting experimental conditions, and the adsorption capacity of GO/4A-3 for RB reached as high as 62.81 mg·g?1 when pH equaled 3. Compared with acid-modified 4A molecular sieve, the removal performance of RB was improved by 291%, attributed to the electrostatic interaction between GO and RB dye molecules. The successful combination of GO and 4A molecular sieve also effectively improved the poor separation performance of GO itself. Adsorption isotherm and kinetic studies demonstrated that the adsorption of RB on GO/4A-3 composite followed the Langmuir isotherm (R2 = 0.996) and pseudo-second-order kinetic model (R2 = 1). The thermodynamics of adsorption showed that the RB was spontaneously, endothermically, and entropy-increasing adsorbed onto 4A molecular sieve and GO/4A composites. This study provided a facile and efficient way to process the difficult-to-decompose dye wastewater.
查看更多>>摘要：? 2022 Elsevier B.V.Capturing p-xylene from waste gas is a top priority, as it is classified as a Group I carcinogen, which can cause great harm to the human living environment. In this study, a facile synthetic route was designed to prepare microporous biochar (CABCs) through esterification and ion exchange and successively introduce carboxyl and alkali metal ions on the surface of biochar precursor before carbonation. The CABCs showed excellent performance in capturing p-xylene. The optimal preparation conditions were citric acid concentration of 0.6 mol L?1, KOH concentration of 2 mol L?1, carbonization temperature of 800 °C, and time of 60 min. The pore size of CABCs was 1.48 nm, which was 2.60-fold larger than n-CABCs derived from biochar precursor without citric acid modification. The presence of moisture had a negative effect on capturing p-xylene. In addition, the adsorption of p-xylene onto CABCs was described well using pseudo-second-order kinetic and Langmuir isothermal models, and the maximum monolayer adsorption capacity was 110.74 mg g?1 at 313 K. Furthermore, the adsorption properties of p-xylene onto CABCs were demonstrated by theoretical calculations based on density functional theory and molecular dynamics simulation to guide the optimization of pore size. Moreover, p-xylene adsorption was endothermic and spontaneous in nature, and the adsorption mechanism primarily included micropore filling and π–π interaction.
查看更多>>摘要：? 2022 Elsevier B.V.Electrodialysis with ultrafiltration membrane (EDUF) is currently investigated at semi-industrial scale (560 cm2 of effective electrode surface) for the separation of bioactive cationic peptides. In this study, the focus was put on the impact of the initial whey protein hydrolysate (WPH) concentration, and the effect of current intensity have been tested. Experiments at 2%, 4% and 8% (w/v) WPH showed that a proportional relationship exists between the initial WPH concentration, and the quantity of peptides recovered. The cationic recovery fractions contained 16 peptides in similar amount as the previous work although including newly identified sequences. Thus, selectivity of the cationic recovery fraction was even improved. The working parameters used allowed obtaining a final 4.7% peptide yield after 6-h runs at 8% WPH. Aiming at nutraceutical applications built on the important ACE-inhibitory and DPP-IV inhibitory activities observed (6 times and 4 times higher than those of the initial WPH, respectively), two types of eco-efficiency scores were established based on those bioactivity values. Considering these scores, using the cationic recovery fractions as an antidiabetic product seems to be the most promising avenue. Preliminary results yielded by an experiment at higher current intensity are also very encouraging due to a barely increased environmental impact cost conjugated to a significantly higher peptide yield and preserved bioactivities. With all these new results, EDUF can be viewed as a promising industrial technology for the recovery of bioactive peptides in the perspective of ecoefficient strategies.
查看更多>>摘要：? 2021 Elsevier B.V.Reactive species, such as hydroxyl radicals (·OH), holes (h+) and superoxide radicals (·O2?), are considered as the main active substances involved in the photocatalytic degradation of organic pollutants. However, to the best of our knowledge, the effect of the photon energy on the generation of these species has never been examined in detail. In this study, the photocatalytic production of ·OH, h+ and ·O2? over niobium pentoxide (Nb2O5) was investigated as a function of the excitation wavelength. The ESR results clearly show that all three active species can be generated at 355 nm for both pure and C-doped Nb2O5. At 532 nm, which is well beyond the absorption edge of Nb2O5 (399 nm), only h+ and ?O2? are produced over pure Nb2O5, while at the same time all three species can be produced over C-doped Nb2O5. The results of the trapping experiments indicate that ?O2? and h+ are the main reactive species that are responsible for the photocatalytic degradation. The photogenerated holes play a crucial role in the wavelength range of 365–420 nm but become less active with increasing wavelength. ?O2? shows little dependence on wavelength and is consistently active at all wavelengths between 365 and 630 nm, in particular, for C-doped Nb2O5. It is concluded that the presence of localized states within the forbidden gap has a profound impact on the photocatalytic activity in the visible-wavelength region.
查看更多>>摘要：? 2021 Elsevier B.V.It has been ever attracting increasingly growing demand to develop highly efficient method of aqueous arsenites [As(III)] removal due to the high toxicity of arsenic in drinking water. This work presents an oil vine-like structural MIL-53(Fe) modified by nitrogen doped carbon quantum dots (N-CQDs) with excellent As(III) removal property, which is achieved through the photocatalytic oxidation of the As(III) and simultaneous adsorbed the generated arsenate [As(V)]. The abilities of As(III) oxidation and removal efficiency for N-CQDs3/MIL-53(Fe) are over 6 times higher than that of pure MIL-53(Fe). The impressively capability of N-CQDs3/MIL-53(Fe) in photocatalytic oxidation and adsorption is attributed to the accelerated separation of photogenerated electron-hole by the in situ embedded N-CQDs. Moreover, the results of the experimental analysis and density functional theory (DFT) DFT calculations confirm that the edge structure of C/O site significantly improves the removal ability of As(III) by forming bidentate C-O-As bonds and occupying coordinatively unsaturated atoms. Therefore, based on the excellent performance and reusability of N-CQDs3/MIL-53(Fe) in As(III) removal, it offers a new potential strategy to develop high efficient MOF based materials for As(III) removal.
查看更多>>摘要：? 2022 Elsevier B.V.The treatment of oily wastewater has received significant attention because of its negative influence on environments. Despite various methods on oil removal were developed, photoeletrocatalysis (PEC) technique is considered to be a promising method. In this study, Ag3PO4@NiO-Ni foam photoelectrode was synthesized through the “hydrothermal-impregnation-calcination” three-steps to realize the PEC degradation of oil pollutants in water. The introduction of NiO-Ni foam provides simultaneous advantages of functioning as an electrode material and the synergistic photodegradation with Ag3PO4. The resulting Ag3PO4@NiO-Ni foam photoelectrode are characterized and utilized for the degradation of diesel and crude oil under PEC condition. Within two hours, the photoelectric removal of 1000 mg/L diesel can reach 88.7%. The influence of virous environmental factors, such as pH, temperature, inorganic cation and humic acid, on PEC degradation have been investigated. After 10 cycles, the removal of more than 70% can still be maintained. Finally, the possible PEC degradation mechanism was analyzed. This provides effective theoretical support for the treatment of actual oily wastewater.
查看更多>>摘要：? 2022 Elsevier B.V.The solar-driven interface evaporation (SIE) is considered as a potential approach for desalinating seawater and obtaining clean water. However, most reported SIE systems can hardly handle with the accumulating salt crystals. Herein, a new type of SIE device based on surface-carbonized rattan (C-rattan) is presented for high-performance and salt-free desalination. Owing to the hierarchical channels in each vascular bundle and the natural gradient structure of the rattan stem, the C-rattan evaporator can spontaneously generate salinity gradients between and within the vascular bundles that form a synergistic effect to prompt salt exchange and high-salinity solution reflow. In addition to a high water evaporation rate of 1.47 kg m?2 h?1 and an efficiency of 90.4% under 1 sun illumination, the C-rattan also presents an outstanding salt resistance ability and an evaporation rate of 1.17 kg m?2 h?1 even for the high-salinity brines (20 wt% NaCl solution). Additionally, the C-rattan possesses the self-cleaning ability that enables it to clear off extra added salt during the solar desalination process. Considering its low-cost and sustainable raw materials, simple preparation procedures, long-term salt resistance ability and self-cleaning capacity, the C-rattan-based SIE device holds a great promise for people living in developing regions to obtain drinkable water from seawater or high-salinity brine.
查看更多>>摘要：? 2021 Elsevier B.V.Esterification coupled with pervaporation (PV) is an effective method to improve conversion by thoroughly and rapidly removing the water product. In this study, a high-flux and acid-resistant mordenite (MOR) zeolite membrane was applied to enhance the esterification of acetic acid and ethanol. The effects of catalysts, catalyst loading, reaction temperature and initial acid/alcohol molar ratio on the conversion of ethanol for the esterification with PV were investigated systematically. Results showed that a high conversion (99.3%) was obtained in a short reaction time of 480 min when the operating conditions were optimized as reaction temperature of 353 K, concentrated H2SO4 catalyst loading of 0.1 wt% and initial acid/alcohol molar ratio of 1.5:1. The conversion of esterification without PV reached equilibrium was 76.7% but enhanced to 99.3% with PV in 480 min. The conversion of ethanol was up to 98.4% even at a low initial acid/alcohol molar ratio of 1.2:1. Importantly, the membrane showed good acidic stability in the esterification with PV after 8 reaction cycles. Thus through the coupling of PV and esterification, the conversion of ethanol was greatly improved due to the water from esterification was removed timely. On the other hand, the usage of acetic acid could be reduced, which enormously decreased the energy consumption in the production process.
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