Higher Mass Transfer Coefficient Research Articles

Three-dimensional porous SiC/BDD electrode with long-term robustness and enhanced electrochemical degradation performance for refractory organic pollutants

Boron-doped diamond (BDD) electrodes with a three-dimensional (3D) porous network structure can overcome the mass transfer limitations and increase substantially the utilization rate of active oxygen species. Nonetheless, the 3D porous network structure was invariably built using metallic substrates, which inherently have inferior stability because of their non-corrosion resistance and the severe thermal mismatch between BDD films and substrates. Herein, we reported, for the first time, the use of a commercially porous silicon carbide (SiC) as the substrate to construct a 3D SiC/BDD electrode to simultaneously alleviate the problematics of substrate corrosion and thermal mismatch. This novel electrode exhibited a long-term service lifetime of 800 h in 3 M H2SO4 under the current density of 50 mA cm−2, over 500 times longer than the conventional metallic substrate-based BDD electrodes. The optimum p-SiC/BDD electrode exhibited a high oxygen evolution potential of 2.04 V vs. SHE, a low charge transfer resistance of 18.4 Ω, a high mass transfer coefficient of 2.78 × 10−5 m s−1, and a thin diffusion layer thickness of 25.2 μm. The proposed electrode had a threefold larger pseudo-first-order reaction rate constant than a flat BDD electrode, although it consumed just a fourth of the latter’s electric energy. The superior performance was attributable to an increased mass transfer rate confirmed by computational fluid dynamics (CFD) simulations as well as a high yield of reactive oxygen species verified by electron spin resonance (ESR). Furthermore, the proposed SiC/BDD electrode could work effectively under different water matrices in the presence of diverse salt electrolytes, thus paving a new avenue for the structure design of robust non-active anode materials.

Antibubble column: A mean to measure and enhance liquid–gas mass transfer through surfactant-laden interfaces

Antibubbles are ephemeral objects composed of a liquid core encapsulated by a thin gas shell immersed in a liquid bulk. The gas shell thickness evolves in time, driven by two contributions: gravitational drainage and gas–liquid mass transfer. The low density contrast between the antibubble and the bulk, as well as its weak deformability constitute advantages that are used to measure the mass transfer coefficient (MTC) in a so-called antibubble column, in a time-resolved fashion. Shells made with pure air give low data reproducibility. Consequently, perfluorohexane, a low-solubility gas, was mixed to air to enforce gas desorption from the bulk and obtain reliable data. MTC obtained with various surfactants and concentrations are found to deviate from the Frössling correlation built for fully rigid interfaces: higher MTC are consistent with partially rigid interfaces due to a partial coverage of surfactants along a so-called spherical cap, while lower MTC are consistent with an additional resistance to the transfer of mass due to the presence of surfactants forming a monolayer at high concentration. Finally, the advantages in terms of control and compactness of an antibubble column as compared to a bubble column for liquid–gas mass transfer are demonstrated. Specifically, an antibubble is shown to transfer dozens of times more mass than a bubble that would initially carry the same amount of gas. Antibubbles are therefore shown to provide a new, time-resolved, way to measure MTC, as well as promising route to enhance liquid–gas transfers in multiphase reactors.

Advanced oxidation of Arsenic(III) to Arsenic(V) using ozone nanobubbles under high salinity

Arsenic, a highly toxic element, is present in various water resources as As(III) and/or As(V). The removal of As(V) using adsorption is considered to be easier than the removal of As(III). In this work, we report the oxidation of As(III) to As(V) using ozone nanobubbles. Ozone has been widely used in the advanced oxidation process (AOP) to remove organics and inorganics in wastewater. The major advantage of ozone nanobubbles is their enhanced half-life, which leads to higher ozone solubility in water. In addition, the rate of mass transfer by using nanobubbles can be enhanced drastically. The effect of ozone flow rates, initial As(III) concentrations, pH levels, and the presence of salt is systematically studied in this work. The present results revealed that ozone nanobubbles positively impacted the oxidation of As(III) to As(V). AOP process based on O3 NBs (nanobubbles) was most efficient with 99 % oxidation rates of 1 ppm of As(III) within 20 minutes at 6.5 ppm ozone concentrations. An acidic pH of 3–7 promoted quick oxidation due to the high mass transfer coefficient of ozone nanobubbles. About ∼70 % degradation of As(III) to As(V) was achieved with 0.10854 min-1 rate constant at acidic (pH = 3) compared to ∼39 % degradation with 0.046 min-1 rate constant at pH =11. The presence of salt (∼50 mM) in the solution not only hindered the ozone mass transfer coefficient but also reduced the stability of nanobubbles. The detection of reactive oxygen species, particularly hydroxyl radical was unravelled by utilizing 2-propanol as a scavenger.

Convective Drying of the Zucchini Slices; Impact of Pretreatments on the Drying Characteristics and Color Properties, Evaluation of Artificial Neural Network Modeling and Thin-Layer Modeling

This study focused on the impact of citric acid, hot water blanching, and ultrasound pretreatment on the drying of zucchini slices, color properties, and the comparison of artificial neural network (ANN) and thin-layer modeling. The pretreatments enhanced the drying rate and reduced drying time. Ultrasound pretreatment was observed as the most effective, with a reduction rate of the drying time as 40%. Besides, mass transfer and moisture diffusion phenomena were positively affected by pretreatments, depending on the increment of the drying rate. The highest mass transfer coefficient (hm), moisture diffusivity (D) by the Dincer and Dost model, and effective moisture diffusivity (Deff) by the Crank equation were obtained with ultrasound pretreatment. On the other hand, Midilli and Kucuk, Parabolic, and Page gave the best predictions among the thin-layer models. However, ANN modeling had a better performance than thin-layer modeling due to a higher determination coefficient (R2) and lower root mean square error (RMSE) values. Color properties of the zucchini slices were affected by drying processes. In general, the redness and yellowness of the zucchini slices increased; however, lightness did not show statistical significance. Additionally, citric acid pretreatment gave the lowest total color difference (∆E).

Analysis and insights of the second-generation ternary AMP-PZ-MEA solvents for post-combustion carbon capture: Absorption-regeneration performance

This work comprehensively investigates absorption and regeneration performance of the second-generation AMP-PZ-MEA in comparison with the first-generation AMP-PZ-MEA, the benchmark 5 M MEA, and the conventional MEA at the same amine concentration. The performance indicators include CO2 absorption capacity, mass transfer coefficient, CO2 removal percentage, amount of desorbed CO2, initial CO2 desorption rate, and regeneration heat duty. Both 6 M (i.e., 2:2.5:1.5, 1.3:3.2:1.5, and 0.95:3.55:1.5) and 7 M (i.e., 2:2.5:2.5, 1.3:3.2:2.5, and 0.95:3.55:2.5) second-generation blends show more promising overall absorption and regeneration performance than 5 M, 6 M, and 7 M MEA. In comparison with the first-generation blend, 6 M and 7 M second-generation blends deliver more favorable mass transfer rate. Interestingly, an increase of PZ:AMP molar ratio accelerates mass transfer and absorption capacity but unfavorably affects solvent regeneration. Also, high viscosity of the second-generation 7 M blend (especially, at its equilibrium CO2 loading) retards the solvent regeneration. The key success for a formulation of AMP-PZ-MEA is appropriate PZ:AMP molar ratio and total amine concentration. Too high and too low PZ:AMP molar ratio lead to (i) solvent precipitation and (ii) imbalance of absorption and regeneration performance. Three standouts are recommended. 2.5:0.5:3 is attractive due to its low regeneration heat duty (42.1% lower than that of 5 M MEA). In terms of mass transfer coefficient, 0.95:3.55:1.5 shows 148.6% higher than 5 M MEA. 2:2.5:1.5 is also favorable according its high mass transfer coefficient (91.3% greater respecting 5 M MEA) and low regeneration heat duty (16.3% less than 5 M MEA).

Clean-In-Place (CIP) wastewater management using nanofiltration (NF)-forward osmosis (FO)-direct contact membrane distillation (DCMD): Effects of draw salt

A substantial amount of water is being used during Clean-in-Place (CIP) operation, and is transformed into wastewater that can cause eutrophication to the nearby ecosystem. The present study proposed the Nanofiltration (NF) – Forward Osmosis (FO) – Direct Contact Membrane Distillation (DCMD) to recover the cleaning agents and reclaim freshwater from the model CIP wastewater. NF steps were suggested as prefiltration steps to remove organic compounds from the CIP wastewater. NF steps reduced the lactose and protein contents by 100 % and 95.6 %, respectively. The permeates from NF steps were further managed by the integrated FO-DCMD system. Several draw salts such as NaCl, KCl, MgCl2, and CaCl2 were compared to investigate the influence on FO and DCMD performance. It was found that monovalent salts (NaCl and KCl) outperformed the divalent salts (MgCl2 and CaCl2) in terms of water flux for both FO and DCMD. This can be attributed to the lower viscosity and higher mass transfer coefficient. In addition, the replenishment costs of each salt were evaluated since salts loss occurred during FO and DCMD operation. The cost evaluation revealed that NaCl is most the cheapest salts per reclaimed water. All of this observation indicates that NaCl is preferred in terms of water flux and replenishment cost. The NF permeate kept concentrated using the integrated FO-DCMD or single FO with 2 M of NaCl. Compared to a single FO that showed a consistent decline in draw solution concentration, FO-DCMD could maintain the concentration of the draw solution. Despite the constant concentration, flux decline of FO was observed due to fouling formation caused by the high-temperature operation. However, the FO-DCMD could accomplish the recovery of pure water. Finally, the cleaning agents recovered by the NF-FO-DCMD showed the cleaning efficacy comparable to the fresh NaOH. These results suggest the potential of the proposed system to manage the CIP wastewater.

Mass Transfer of Natural Dye Extraction and the Degradation Rate

This research studied the effect of temperature on the mass transfer rate and degradation rate of natural dye extraction. As the representative, two natural dyes extracted from Senduduk and Susupan Gunung plants were employed. Senduduk and Susupan Gunung are weed plants that are often found in peatlands. Susupan Gunung is easily found in South Kalimantan, and local people use it as a natural dye for handicraft products. Senduduk is often found in the South Sumatra area also used as a natural dye for traditional fabrics. Senduduk and Susupan Gunung were extracted in a three-neck flask using water as a solvent at temperatures of 50°, 70°, and 90°C. Samples of the extract solution were taken at certain times until the tannin concentration was constant. The tannin concentration in the solution was analyzed using volumetric methods. Experimental data consists of tannin concentrations in solution at various times. The mass transfer coefficient, equilibrium constant, and tannin degradation rate constant were determined by minimizing the sum square of errors between experimental data and the model. Senduduk contains more tannin (0.0094 g/cm3 solution) than Susupan Gunung (0.0079 g/cm3 solution), and Senduduk has a higher mass transfer coefficient than Susupan Gunung. The higher the temperature, the greater the rate of tannin degradation. During the extraction process, extract of Senduduk and Susupan Gunung leaves are stable at 50°C, which tends to degrade faster at higher temperatures.

Koefisien Perpindahan Massa pada Ekstraksi Polisakarida dari Biji Asam Jawa dengan Pelarut NaOH

Asam jawa merupakan tanaman tropis yang mudah sekali tumbuh di Indonesia. Daging buah asam jawa telah banyak dimanfaatkan sebagai bumbu masakan, pemberi rasa asam, dan obat – obatan. Sedangkan, biji dari buah asam jawa belum dimanfaatkan secara optimal. Biji asam jawa mengandung polisakarida 50-60%, sehingga berpotensi untuk dimanfaatkan sebagai sumber sakarida dengan cara melakukan ektraksi kandungan polisakarida dari biji asam jawa. Penelitian ini bertujuan untuk mengetahui koefisien perpindahan massa polisakarida pada proses ekstraksi biji asam jawa dengan pelarut NaOH. Ekstraksi polisakarida pada biji asam jawa dilakukan dengan ekstraksi secara batch. Untuk 50gram biji asam jawa diekstrak menggunakan 300ml larutan NaOH dengan variasi konsentrasi 0,1N; 0,2N; 0,3N; 0,4N; 0,5N dengan variasi waktu ekstraksi 15;30;45;60;75 menit. Filtrat hasil ektraksi dipisahkan menggunakan etanol 96% dengan perbandingan 1:2 dan didiamkan selama 24jam. Padatan yangdihasilkan dipanaskan pada suhu 75oC dan dilakukan analisa kadar polisakarida menggunakan metode gravimetri.Penelitian ini memberikan hasil nilai koefisien perpindahan massa (kLa) tertinggi pada konsentrasi NaOH 0,5N yakni bernilai 0,01734/menit.

Feasibility of electrodeionization for phosphate removal.

In this study, electrodeionization (EDI) in bath mode was tested regarding its capability to remove phosphate (PO4 3- ) ions from aqueous solutions. Various parameters affecting the phosphate removal rate via EDI were determined. The results showed that the phosphate removal rate depends on the applied voltage and that the optimum potential was 15 V, corresponding to a phosphate removal rate of 97%. Changing the stream rate of the phosphate-containing solution also affected the phosphate removal rate. Changing the pH of the phosphate-containing solution from 2 to 6 enhanced the phosphate removal rate from 80% to 97%. The presence of Cl- , NO3 - , and SO4 2- ions did not affect the phosphate removal rate. The highest mass transfer coefficient (k) of phosphate was calculated to be 7.85 × 10-4 m/s, and the flux was calculated to be 3.72 × 10-4 mol/m2 s1 at a flow velocity of 3L/h. Thus, the study results showed the feasibility of EDI as an alternative membrane process for removing phosphate from aqueous solutions. PRACTITIONER POINTS: Electrodeionization was employed for the removal of phosphate. The removal of phosphate exhibited dependence on applied potential. EDI demonstrated a remarkable 97% efficiency in phosphate removal. The pH of the solution was found to influence the removal rate.

Design and Preparation a New Composite Hydrophilic/Hydrophobic Membrane for Desalination by Pervaporation.

Herein, experimental and theoretical approaches were used to design a new composite membrane for desalination by pervaporation. The theoretical approaches demonstrate the possibility to reach high mass transfer coefficients quite close to those obtained with conventional porous membranes if two conditions are verified: (i) a dense layer with a low thickness and (ii) a support with a high-water permeability. For this purpose, several membranes with a cellulose triacetate (CTA) polymer were prepared and compared with a hydrophobic membrane prepared in a previous study. The composite membranes were tested for several feed conditions, i.e., pure water, brine and saline water containing a surfactant. The results show that, whatever the tested feed, no wetting occurred during several hours of desalination tests. In addition, a steady flux was obtained together with a very high salt rejection (close to 100%) for the CTA membranes. Lastly, the CTA composite membrane was tested with real seawater without any pretreatment. It was shown that the salt rejection was still very high (close to 99.5%) and that no wetting could be detected for several hours. This investigation opens a new direction to prepare specific and sustainable membranes for desalination by pervaporation.

Performances of a Y-type structured packing produced by 3D foam-printing for the intensification of gas absorption processes

In this work, we report pilot-scale tests on a new design of Y-type corrugated polylactic acid (PLA) packing (Prototype FT.Y), produced by an innovative additive manufacturing process consisting of a one-step 3D foam-printing process. The design characteristics of the packing and the surface texture of the prototype, which is analyzed with optical measurements, are presented. The performances of the FT.Y packing are characterized and compared with those of a benchmark commercial Mellapak 250Y packing, through experimental tests aimed to estimate pressure drops and mass transfer coefficients. The new packing is also tested for a reference absorption case study, the wet Flue Gas Desulfurization (wet-FGD), for its large application in the process industry and as a lab testing method. The 3D foam printing technology allows for an easy tailor-made design of the packing, providing lower weights and interesting surface properties. These translate in low pressure drops and high mass transfer coefficients, which are comparable or superior to those of the Mellapak 250.Y. Indeed, the FT.Y packing provides high liquid-film mass transfer coefficients, which allows desulfurization efficiencies up to 42 % higher than those expected for the benchmark packing. Beyond the potential manufacturing advantages provided by the 3D-foam printing, the FT.Y packing performances make this unit a valuable alternative for process intensification in absorption and distillation processes, especially in those cases when the liquid-film mass transfer resistance has a relevant role in the process design.

Characteristics of CO2 adsorption and desorption on activated carbon in comparison with zeolite 13X and carbon molecular sieve and applications in biogas upgrading using vacuum pressure swing adsorption

AbstractBACKGROUNDBiogas upgrading is the process that increases the fraction of methane (CH4) in biogas, making the biogas suitable for use as vehicle fuel or as fuel with high and stable heating values for combustion engines. The advantages and disadvantages of activated carbon (AC) in CO2/CH4 adsorptive separation should be well understood before application for biogas upgrading. In the first part of this study, characteristics of CO2 adsorption and desorption on AC were investigated using Aspen Adsorption. In the second part, vacuum pressure swing adsorption (VPSA) was modeled, and the performances of the VPSA process using zeolite 13X, carbon molecular sieve (CMS) and AC were compared.RESULTSThe simulations showed that the advantages of AC for CO2 adsorption include relatively high dynamic adsorption capacity and high mass transfer coefficient of CO2 (KLDF,CO2) in AC and consequently relatively high CO2 desorption rates. However, due to the relatively high mass transfer coefficient of CH4 (KLDF,CH4) in AC, the molecular sieving characteristics for CO2 that were estimated from the ratio between KLDF,CO2 and KLDF,CH4 of AC were not significantly higher than that of zeolite 13X and significantly lower than that of CMS (9.85, 8.41 and 20.92 for AC, zeolite 13X and CMS, respectively).CONCLUSIONSThe modeling results predicted that the VPSA process using zeolite, CMS and AC adsorbents gives a biomethane product of around 98%, 97% and 93% CH4, respectively. © 2023 Society of Chemical Industry (SCI).

Study on liquid–liquid two-phase mass transfer characteristics in the microchannel with deformed insert

In this work, the liquid–liquid two-phase mass transfer characteristics in the microchannel with deformed insert were studied. The experiment used di-(2-ethylhexyl) phosphoric acid/kerosene-Cu 2+ as the mass transfer evaluation system. The effects of some key factors such as the total flow velocity, channel inner diameter, channel length, insert diameter, extractant concentration on the extraction efficiency and mass transfer coefficient were systematically investigated. Compared with a simple microreactor, the liquid–liquid mass transfer enhancement effect of the insert was quantitatively analyzed. The study found that the regular deformation of insert could cause fluid interface deformation and promote flow state chaos, effectively increasing the mass transfer rate. And the enhancement effect of the insert was more significant at high flow velocities. The highest mass transfer coefficient in the microchannel with deformed insert was 7.886 s –1 , the enhancement factor could reach 4.17. And only needed 0.095 s to approach the extraction equilibrium. The deformed center insert exhibited an effective liquid–liquid mass transfer enhancement effect, which can be used as a micro-chemical process enhancement method to be applied in the fields of higher throughput mass transfer and chemical synthesis, and at the same time provide ideas for development and structural optimization of microreactors.

Inducing hierarchical pores in nano-MOFs for efficient gas separation.

The synthesis of metal-organic frameworks (MOFs) and their processing into structures with tailored hierarchical porosity is essential for using MOFs in the adsorption-driven gas separation process. We report the synthesis of modified Cu-MOF nanocrystals for CO2 separation from CH4 and N2, prepared from DABCO (1,4-diazabicyclo[2.2.2] octane) and 9,10 anthracene dicarboxylic acid linkers with copper metal salt. The synthesis parameters were optimized to introduce mesoporosity in the microporous Cu-MOF crystals. The volumetric CO2 adsorption capacity of the new hierarchical Cu-MOF was 2.58 mmol g-1 at 293 K and 100 kPa with a low isosteric heat of adsorption of 28 kJ mol-1. The hierarchical Cu-MOF nanocrystals were structured into mechanically stable pellets with a diametral compression strength exceeding 1.2 MPa using polyvinyl alcohol (PVA) as a binder. The CO2 breakthrough curves were measured from a binary CO2-CH4 (45/55 vol%) gas mixture at 293 K and 400 kPa pressure on Cu-MOF pellets to demonstrate the role of hierarchical porosity in mass transfer kinetics during adsorption. The structured hierarchical Cu-MOF pellets showed stable cyclic CO2 adsorption capacity during 5 adsorption-desorption cycles with a CO2 uptake capacity of 3.1 mmol g-1 at 400 kPa and showed a high mass transfer coefficient of 1.8 m s-1 as compared to the benchmark zeolite NaX commercialized binderless granules, suggesting that the introduction of hierarchical porosity in Cu-MOF pellets can effectively reduce the time for CO2 separation cycles.

Ammonia recovery from anaerobic digestion effluent by aeration-assisted membrane contactor

The ammonia recovery from anaerobic digestion (AD) effluent offers a low cost and low carbon footprint strategy for N recovery. To enhance ammonia recovery performance, the aeration-assisted membrane contactor (MC) process was presented with aeration applied on the feed side. The ammonia recovery performance with different pH adjustment methods and operating parameters were tested. Results illustrated that a high ammonia mass transfer coefficient (Kov = 4.85 ×10−7 m/s) could be achieved in the aeration-assisted MC. With the increase in air flow rate from 0 L/min to 0.6 L/min, the Kov increased from 1.21 × 10−7 m/s to 4.85 × 10−7 m/s by about 300%, and the ammonia separation factor (St) increased from 5.75 to 8.91 by about 55%. Additionally, the Kov increased sharply with the increase in feed temperature. Notably, the ammonia removal efficiency can reach 82% after 6-h experiment, which might be due to the large contact area of membrane contactor and the high mass transfer efficiency caused by the optimal conditions. The greenhouse gas (GHG) emission evaluation showed that compared with that of Haber-Bosch process (4.2 kg-CO2 eq/kg-N), the GHG emission of aeration-assisted MC was 1.86 kg-CO2 eq/kg-N under room temperature. The aeration-assisted MC can provide a high-efficient and low GHG-emission ammonia recovery process.

Modeling of Tubular Electrochemical Reactor with a Spiral Design of Anode for Treatment of Petroleum Refinery Wastewater

Petroleum effluent is often made up of a complex combination of metals and organic molecules. In the present work, modeling of a tubular electrochemical reactor (TER) with a novel design operated at batch recycle for petroleum refinery effluent treatment by anodic oxidation was investigated. The reactor is composed from a cylindrical stainless steel cathode and a spiral porous graphite anode at its center. The impact of flow rate on the COD reduction and mass transfer coefficient (k) was studied. Results showed that increasing flow rate led to higher removal efficiency of COD and higher mass transfer coefficient where COD removal of 70% and k with value of 6.283x10-4 cm/s were obtained at flow rate of 4l/min. A power low correlation was obtained between mass transfer coefficient(k) and Reynolds number (Re) with coefficient of determination (R2) equal to 0.994869.This relation can be described as k=1.906x10-6(Re) 0.545 with range of Re 10000≤Re≤ 40000 prevailing turbulent conditions.

An efficient cobalt separation using PVDF-co-HFP based ultrafiltration polymer inclusion membrane by room temperature ionic liquids

Cobalt has been used enormously in industrial and technological applications, especially lithium-ion batteries. Continuing production of cell phones and laptops containing lithium-ion batteries has increased demand for cobalt, which has resulted in a global accumulation of industrial waste in the world. As a result, the separation and purification of cobalt from industrial waste become quietly important. In this study, the high-efficiency recovery of cobalt ions was achieved by PVDF-co-HPF (polyvinylidene fluoride hexafluoropropylene) based ultrafiltration polymer inclusion membranes (UPIM), which were produced by mixing room temperature ionic liquids, plasticizers, and the polymer under optimal conditions. The highest mass transfer coefficient (Jo) of cobalt transport was determined as 3.36x10-6 mol/s m−2 for the optimized UPIM containing 11.35 % (w/w) ONPOE (2-nitrophenyl octyl ether) and 12.27 % (w/w) RTIL4 (1,3-decyl-1H-imidazol-3-ium bromide). Morphological and structural analysis of all UPIMs were investigated by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX). A good relationship was determined between the cobalt peaks in the ATR-FTIR pattern and the color intensity of UPIMs with corresponding room temperature ionic liquids. It indicates that the optimized UPIM has a good potential not only for cobalt recovery but also for qualitative and quantitative direct colorimetric cobalt determination.

Experimental study on heat and mass transfer characteristics between a novel ionic liquid and air under low-humidity conditions

Functional ionic liquids (ILs) are a promising alternative to traditional liquid desiccants. This work is mainly concerned with an experimental investigation on the dehumidification and regeneration performance of an adiabatic falling-film device working with a novel ionic liquid (IL). A specialty of this report is the operation under rather low air temperature as well as low absolute humidity. The effect of air and solution volume flow on the coupled heat and mass transfer coefficient was evaluated based on the state parameters of air and solution by means of the NTU-Lef model. Additionally, aqueous lithium bromide solution (LiBr-H2O) was used for comparison. The results indicated that both IL and LiBr-H2O can dehumidify moist air to nearly 2.2 g/kgda, and the regeneration rate of IL is significantly larger than that of LiBr-H2O. The heat and mass transfer coefficient of IL in dehumidification process is less than that of LiBr-H2O, while the regeneration process is the opposite. It is found that the low wettability of IL on the surface of falling-film plate limits its excellent dehumidification potential, whereas its high mass transfer coefficient in the regeneration process makes up for the disadvantage of poor regeneration potential. Besides, a new correlation for the coupled heat and mass transfer coefficient of IL is proposed. From the perspective of operation optimization, increasing the wettability of IL on falling-film plate will significantly improve the dehumidification rate, and the optimal flow range of IL needs to be considered in the regeneration process. This study establishes a basis for the optimization of heat and mass transfer process between ILs and moist air, and provides guidance for the application of liquid desiccant dehumidification under low-humidity conditions.

Design and experimental analysis of a novel slant‐plate photoreactor

AbstractA novel slant‐plate photoreactor (SPR) immobilized with titanium dioxide (P25) was developed to address the disadvantage that the effluent on the backlight side of the corrugated plate photoreactor could not be treated. The SPR was tested and analyzed regarding the degradation of phenol under UV light. For comparison, a flat‐plate photoreactor, a slurry photoreactor, and a corrugated plate photoreactor were also examined. The performance of SPR in phenol degradation was higher than either corrugated plate photoreactor with the same angle or flat‐plate. Furthermore, SPR exhibited highest energy utilization efficiency compared to the corrugated plate photoreactor with the same angle and flat‐plate photoreactor in phenol oxidation. The superior performance of SPR was due primarily to the highly exposed catalyst surface area, high mass transfer coefficient, and multiple reuses of reflected light. In addition, the SPR was tested under natural solar light for its possible implementation in practice.

Assessment of a Modified Hydrocyclone with Ultrasonic Assistance for Nickel Powder Electrochemical Production

An electrochemical reactor based on a modified hydrocyclone with ultrasonic assistance is examined with the purpose of analyzing the continuous production of nickel powder from dilute solutions simulating industrial wastewaters containing nickel. Under operating conditions, nickel deposition takes place under mass-transfer control and the helical flow inside the reactor generates a high mass-transfer coefficient, thus improving the removal of metal ions. The application of ultrasound is crucial for the detachment of the electrodeposited nickel, which allows its recovery as a metal powder. The best result was achieved at a current density of 5368 A m–2 and 60 °C yielding a nickel powder fraction obtained from the spigot of the device higher than 90%. The gravimetric current efficiency and the specific energy consumption were 33.4% and 23.8 kW h kg–1, respectively, for an experiment lasting 13 min. The nickel particles are of high purity and dendritic nature with an average size of 22.9 μm.