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Highly efficient separation of organic substances from high salinity brine by nanofiltration
No full textEfficient separation of organic compounds from the high salinity brines during the treatment of reverse osmosis concentrate (ROC) is highly desirable and also very challengeable for the purpose of zero liquid discharge (ZLD). For the general treatment process, the efficient removal of organic compounds from the NaCl rich solution before the evaporation-crystallization stage is one of the key challenges. In this work, separation of N-(2-hydroxypropyl) morpholine (NMH), 4-morpholineacetate (MHA), the major organic components of ROC in refinery, and monovalent/divalent ions from the high salinity brines by three commercial nanofiltration (NF) membranes, i.e. Desal-5DK, Desal-5DL and NF270 were systematically investigated. The effects of various parameters on the rejection performance of these three NF membranes were experimentally investigated. The results showed that the retentions of NMH and MHA were dominated by flux and pH. Single stage filtration experiments showed that the rejection to NMH and MHA with various operating parameters was high and stable for DK. In comparison, DL and NF270 had higher separation efficiency for monovalent and divalent ions. The experiments determined that the rejections of NMH and MHA were 99.16% and 98.42% under the optimized conditions, respectively, indicating that NF membranes were highly efficient for separating organic compounds from the high salinity brine
<p>Removal of Mn(II) from hydrochloric acid leach liquors of nickel laterite ore through microbubble oxidation and acid leaching</p>
No full textLeach liquor obtained from atmospheric acid leaching of nickel laterite with HCl solution contain large concentrations of Mn and Mg. This paper presents a method for separating large amounts of Mn and Mg from Ni and Co chloride solution by microbubble aeration oxidation and acid leaching processes. Such methods utilize the multiple advantages of the microbubble technology, such as large specific surface area, negatively charged surface, long stagnation, high oxygen mass transfer efficiency, and the ability to generate active oxygen. The effects of aeration pore size, oxygen flow rate, reaction temperature, stirring speed, and pH were studied. Under optimal experimental conditions (bubbling O-2 flow = 0.4 L/min, aeration aperture = 0.45 mu m, speed of agitation = 400 rpm, temperature = 50 ?, pH = 7), the recovery efficiency of Ni and Co were 99.3% and 89.0%, and the removal efficiency of Mn and Mg were 99.5% and 97.7%, respectively. Through XRD, XPS, and FTIR, it was found that soluble Mn was first oxidized to Mn(3)O(4 )and MnO2.H2O. In the acid dissolution process, Mn3O4 reacted with dilute sulfuric acid to form MnO2, which is insoluble in dilute acid, and was thus easily separated from Ni and Co. Analysis of the mass transfer process showed that the microbubble aeration method can greatly increase the oxygen mass transfer coefficient (0.073 s-1), accelerate the dissolution of O-2, and create conditions for the generation of active oxygen species
Adsorption of heavy metal ions by iron tailings: Behavior, mechanism, evaluation and new perspectives
No full textHere we report the adsorption of heavy metal ions from wastewater by the pellet material (IT@SA) of iron tailings (IT) compounded with sodium alginate (SA) as a regenerable adsorbent. The adsorption capacities of IT@SA on Zn2+, Cu2+, Pb2+ and Ni2+ were 1.748 mg/g, 2.404 mg/g, 10.000 mg/g and 1.279 mg/g, respectively. The adsorption behavior would be in accordance with the Langmiur isothermal adsorption model, the pseudo second-order kinetic model and the intra-particle diffusion model, indicating that the adsorption process was mainly controlled by monolayer chemisorption on heterogeneous surfaces, and that the adsorption proceeded spontaneously due to intermolecular interactions. The selective adsorption of IT@SA can be represented as exhibited Pb2+ > Cu2+ > Zn2+ > Ni2+ under competitive adsorption conditions. The adsorption mechanisms mainly include surface physical adsorption, ion exchange, functional group complexation, precipitation, electrostatic attraction, etc. This work opens up a new direction for designing stimuli-responsive materials for energy-efficient and sustainable heavy metal ions adsorption and water purification, while the recycling of iron tailings contributes to the sustainable development of China's iron ore processing industry. It fully conforms to the concept of clean production and efficient utilization of industrial solid waste materials
Catalytic Pyrolysis of Poly(ethylene terephthalate) withMolybdenum Oxides for the Production of Olefins and TerephthalicAcid br
No full textA catalyst based on molybdenum oxides was prepared and used for the catalytic pyrolysis of PET (poly(ethyleneterephthalate)) in a H2atmosphere to facilitate the direct conversion of PET for producing olefins (ethylene and propylene) andTPA (terephthalic acid). At a reaction temperature of 400 degrees C, the yields of olefins and aromatic products were the highest, reaching10.10 and 52.16 wt %, respectively. Meanwhile, the carbon black could be entirely removed. The content of TPA in aromaticproducts was about 70%, and the content of benzoic acid reached 22.64%. Analyses using in situ gas chromatography (GC) andhigh-performance liquid chromatography (HPLC) were performed to clarify the possible reaction mechanism involved in thecatalytic pyrolysis of PET. Vinyl ester was found to be an important intermediate in the formation of olefins. The molybdenum oxidecatalyst promoted the cleavage of the C-O bond in the side chain of PET molecules to form TPA and monovinyl terephthalate. Bycatalytic hydrogenation, vinyl ester was easily attacked by H to drop offthe vinyl end to form olefins, simultaneously converting theester groups into a carboxyl group and further into a TPA. This is also the main path for the production of olefins. Meanwhile, thesource of olefins also involved the hydrogenation of the coordinated quaternary cycle transition state of vinyl esters and the Htransfer and cracking of monoethyl terephthalate. In addition, it was found that the presence of H2was the main reason for thereduction of carbon black products. This work is promising to promote the highly efficient utilization of waste PET and directionaladjustment of pyrolysis products
Laser powder bed fusion of cemented carbides by developing a new type of Co coated WC composite powder
No full textThe study addresses the issue of the absence of high-quality WC-Co composite powder for laser powder bed fusion and assessing the printability of the new powder in terms of densification, microstructure and mechanical properties. The fluidized bed chemical vapor deposition (FBCVD) combined with electroless plating process was adopted to make core-shell structured WC-Co composite powder. The excellent uniformity of Co and good powder flowability were achieved by tuning the size and distribution of Co catalyst during FBCVD and regulating their relationship to the subsequent electroless plating behavior. The newly developed composite powder exhibited excellent printability. The densification mechanism was largely dependent on the laser energy density. The liquid formed by the melting of Co was responsible for the densification at low laser energy density, while the Co-W-C ternary liquid resulted from the dissolution of WC into Co melt dominated the densification at high laser energy density. Microstructurally, the morphology and size of WC grains were insignificantly changed because of its non-participation with liquid formation at low laser energy density. The rectangular/triangular WC grain morphology similar to the traditional sintered was formed at high laser energy density because of the precipitation of WC from the Co-W-C ternary liquid. Affected by the different liquid formation processes, increasing laser energy density increased the relative density, promoted the W2C phase formation and decreased WC grain size, which remarkably improved the hardness and tribological properties of the printed cemented carbide
A comprehensive characterization of virgin and recycled 316L powders during laser powder bed fusion
No full textThe primary constraints hindering the widespread adoption of laser powder bed fusion (LPBF) are expensive raw materials, internal defects, difficulty in controlling the quality and stability, and lack of consistency in the powder feedstock. The spatters induced by the violent interaction between the laser and powder can be deposited on the unmelted powder bed, and if not effectively separated by sieving, they would pose a significant detriment to the characteristics and consistency of the recycled powders. In this work, a systematic investigation of the evolution mechanism of 316L powders after 10 and 30 successive recycling in the LPBF process was presented. Firstly, the variation mechanism of particle size distribution and morphology of 316L powder and the generation mechanism of heterogeneous particles were studied. Then, changes in microstructure and hardness trends were characterized. Finally, we emphasized the changes of chemical composition, phase composition, magnetic properties, and the formation mechanism of oxide spots. The results show that the circulation had significant effects on the physical properties, phase transformation, mechanical properties, and magnetic properties of the 316L powders, but had minor effects on the chemical composition, surface and cross-sectional microstructure. In addition, a large number of oddly shaped, large-diameter spatters were identified in the recycled powders, which could not be separated effectively by sieving, and the formation mechanism of the spatters were elaborated. Based on the comprehensive high temperature oxidation thermodynamics and experimental results, it was concluded that the circular oxide spots on the spatter surface were a composite of multiple oxides of Mn and Si. Further, it was also shown that the ferrite content, XRD peak characteristics, and magnetic properties in the recycled powders were governed by the droplet solidification modes, which in turn is determined by the chemical composition and cooling rates. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)
A comprehensive 3D multi-physics coupled simulation model of slurry redox flow batteries
No full textSlurry redox flow battery (SRFB) offers a high energy density and low cost solution for scalable storage of renewable energies. Here we present a 3D multi-physics coupled model for SRFB. This model incorporates the fluid dynamics of slurry flow, electrochemistry of lithium electrode reactions, transport of solid lithium in particles and mass balance in storage tank. The work introduces a molar mass transfer equation to convert the global solid lithium concentration change in slurry flow domain into a local reaction source on the electrode surface, which helps to accurately describe the dynamic state of charge (SOC) in SRFB considering flow convection. Simulations on this model have been conducted to predict the fluid dynamic and electrochemical performance of SRFB. The simulation results agree well with experimental results, which validate the further application of this model in optimizing SRFB designs
Oil-in-ionic liquid nanoemulsion-based intranasal delivery system for influenza split-virus vaccine
No full textEffective antigen delivery and immune stimulation in nasal mucosa determine the success of mucosal immunity. Here, an oil-in-ionic liquid (o/IL) nanoemulsion formulated with choline and niacin IL ([Cho][Nic]), squalene, and Tween 80 surfactant is explored as a vaccine delivery system for intranasal mucosal immunization. Compared to the o/w emulsion counterpart without the ILs, the o/IL manoemulsion showed a reduced and more uniform size of approximately 168 nm and significantly improved stability. Studies in mice model showed that when was used as an intranasal vaccine delivery system for influenza split-virus antigens, the antigens in the o/IL nanoemulsion induced strong mucosal immune responses with secretory IgA titers 25- and 5.8-fold higher than those of naked and commercial MF59-adjuvanted antigens, respectively. The o/IL nanoemulsion system also induced stronger systemic humoral responses. The excellent mucosal adjuvant effects of the o/IL nanoemulsion mainly benefited from the prolonged retention of antigens in the nasal cavity, enhanced antigen permeation into the submucosa, and the consequently promoted proliferation of CD11b cells and CD4+ T cells in nasal mucosaassociated lymphoid tissue. Moreover, when used as an injection adjuvant, the o/IL nanoemulsion also induced stronger humoral immune responses than MF59. Thus, the [Cho][Nic]-based o/IL nanoemulsion vaccine delivery system can serve as a promising adjuvant platform
Vanadium phosphorus oxide catalyst: Progress, development and applications
No full textWith the increasing awareness of carbon neutrality, the global warming issue has been well addressed for the reduction of carbon emissions into the atmosphere. Enormous amounts of carbonaceous gaseous byproducts have already been released into the atmosphere especially after the start of industrial revolution in the last century. Most industrial processes releases low carbon alkanes directly into the environment. Among them petroleum refinery units generate low carbon alkanes especially n-butane as gaseous byproducts. In recent decades, n-butane has been used as a reagent to generate important valuable chemicals such as maleic anhydride with the support of vanadia catalysts. The complex vanadium phosphorus oxide exists in the nature in almost fifteen different phases. Each one has distinguished structural morphology and chemical composition, and exhibits particular physiochemical characteristics such as surface acidity, lattice oxygen, surface oxygen, valance state, P/V ratio, V+4/V+5, surface to lattice oxygen ratio, etc., which are highly dependent on the precursor preparation and catalyst activation conditions. Researchers believed that either the addition of various promoters/cocatalysts/metals-dopants, or introducing new preparation techniques such as microwave irradiation, ultrasound, ball milling, barothermal, calcination, sol-gel method electrospinning, hydrothermal and solvothermal synthesis can be used for the improvement of the catalytic selectivity and activity. Aforementioned different aspects are described in the current review along with the description of reaction kinetics and reaction mechanism. Additionally, we have also highlighted the important industrial issues such as air/n-butane pretreatment, deactivation, water supplement, phosphorus supplement, and the strong exothermic reaction, which are influencing the overall catalytic performance. (c) 2022 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved