Liquid Diffusion Research Articles

Oyster shell powder-loaded cellulose gel beads as a high-efficiency adsorbent for phosphorus recovery: preparation, kinetics, isotherms and thermodynamic studies.

Given the critical importance, resource limination and environmental toxicity of phosphorus, the study of phosphorus recovery and utilization is extremely urgent. This paper utilized unmodified oyster shell powder (OSP) and cotton fibers as raw materials to prepare OSP-loaded cellulose gel beads (OSP@Gel) through the fiber-dissolving capability of LiBr·3H2O molten salt, for phosphate recovery from water. The surface microstructure and chemical properties of OSP@Gel were characterized by using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), confirming the loading of OSP onto the gel matrix. The phosphorus adsorption capacity of a single OSP@Gel bead could reach up to 8.80 ± 0.32 mg at the optimal OSP doping amount of 1.0 g and optimal pH of 5.0. Kinetic and isotherm analyses revealed that the experimental data fit the PSO model and the Langmuir model. Thermodynamic analysis suggested that the phosphate adsorption was endothermic. Combined results from SEM and XPS analyses indicated that the adsorption of phosphate by OSP@Gel was chemical, with adsorption rate controlled by both liquid film diffusion and intraparticle diffusion. The high phosphate adsorption capacity, good mechanical stability in water, and easy degradability in plant soil provide OSP@Gel beads with great potential for phosphate recovery.

A new liquid membrane diffusion model for characterizing the adsorption kinetics of europium by using a continuous measurement of adsorption platform

A new liquid membrane diffusion model for characterizing the adsorption kinetics of europium by using a continuous measurement of adsorption platform

Comprehensive analysis of cationic dye removal from synthetic and industrial wastewater using a semi-natural curcumin grafted biochar/poly acrylic acid composite hydrogel.

Polymer composites offer a tailored framework as an exceptional candidate for water treatment due to their tunable chemical structure, porous 3D architecture, physiochemical stability, accessibility, pH-sensitivity and ease of use. In this study, curcumin-engineered biochar is embedded into a cross-linked polyacrylic acid hydrogel matrix using in situ polymerization for developing a semi-natural adsorbent for the removal of cationic dye from an aqueous solution. The physicochemical features of the generated composite hydrogel are significantly influenced by the implementation of curcumin-grafted biochar into the polyacrylic acid substrate. Comprehensive characteristic approaches were employed to explore all aspects of the adsorbent's properties, especially its removal efficacy. The methodical adsorption study was accomplished by monitoring dynamic factors such as pH, adsorbent content, time frame, and initial dye concentration. The presence of the porous aromatized structure of biochar, active oxygen-enrich functional groups (carboxyl, hydroxyl, keto, enol, ether) coupled with the conjugated curcumin structure facilitate the effective establishment of hydrogen bonds, electrostatic interactions, π-π interactions, electron donor-acceptor and charge-assisted H-bonding with the malachite green (MG) and rhodamine B (Rho) molecules. The highest adsorption capacities of MG and Rho reached 521 mg g-1 and 741 mg g-1 respectively, in the range of neutral pH, considering their molecular nature, functionalities, and unique adsorption mechanisms. The isothermal modeling was carried out with Henry, Langmuir, Jovanovic, Freundlich, Temkin, and Koble-Corrigan models to determine the adsorption system. Additionally, the kinetic data were assessed with Bangham, pseudo-first-order, pseudo-second-order, intra-particle, and liquid film diffusion models to ascertain the rate-limiting phase. The Koble-Corrigan and Langmuir isotherm models (R2 > 0.997) as well as pseudo-second-order (R2 > 0.998) and Elovich (R2 = 0.983 and 0.995) kinetics models provide a substantial level of concordance with empirical findings. The analysis of non-linear diffusion models revealed that the Bangham (R2 > 0.995) pore and liquid film diffusion (R2 > 0.960) models has major influence on the rate of the adsorption procedure. The binary adsorption test demonstrated higher efficacy of the synthesized adsorbent in the removal of malachite as compared to rhodamine. This study sheds light on the design of a cost-effective semi-natural polymeric composite for treating dye-polluted wastewaters, a major milestone toward environmental and ecological sustainability.

Novel amino-ethyl carboxymethyl cellulose crosslinked ampholyte hydrogel development for Methyl Orange Removal from Waste water: Kinetics, isotherms, and thermodynamics studies

In this study, a novel ampholyte hydrogel known as amino-ethyl carboxymethyl cellulose crosslinked hydrogel (AECMC) was synthesized and utilized to remove Methyl orange (MO), an azo-dye commonly found in dyes contaminated wastewater. This marks the first instance of such a hydrogel being generated for this specific application. The presence of induced amine groups in the modified carboxymethyl cellulose matrix facilitated the creation of adsorption positive charge centers, which effectively attracted MO azo-dye anions. The level of amination exhibits a clear correlation with both the percentage of MO adsorption and the capabilities of adsorbents. An initial rapid adsorption phenomenon was seen within the first 15 min, followed by a gradual decrease in the rate of adsorption until reaching a plateau. The adsorption capacity is notably influenced by the temperature of adsorption, particularly in the case of employing low aminated carboxymethyl cellulose (CMC) derivative. The aforementioned effect exhibits a decrease in magnitude when increasing levels of aminated carboxymethyl cellulose (CMC) derivatives are employed. The kinetics of the adsorption process was assessed by the use of three models: Pseudo-first-order, Pseudo-second-order, and Elovich. Moreover, the mechanism of the adsorption process was monitored using two models, namely Dumwald–Wagner and intraparticle models, which described the liquid film diffusion or intraparticle diffusion, while the external mass transfer was examined by the Boyd model. The Boyd diffusion model determines that the process rate is limited by film diffusion. Additionally, the adsorption isotherm was examined using established models such as Langmuir, Freundlich, and Temkin isotherms. The thermodynamic characteristics of the MO adsorption process have been investigated at various adsorption temperatures using the Van't Hoff model. The results obtained from the study indicate that the process of MO adsorption adhered to the Pseudo-second-order kinetic model. Additionally, the Langmuir isotherm model was found to be applicable, with a maximum adsorption capacity of 2.033 mg/g for the Langmuir monolayer. Furthermore, it was observed that the adsorption process was spontaneous and exhibited an endothermic character.

Cinética da secagem e propriedades termodinâmicas da casca de goiaba

ABSTRACT: The drying agroindustrial products is used to preserve the sensory and nutritional quality and to reduce the biological activity, preventing deterioration and loss of commercial value. The objective was to study the mathematical modeling Guava bark drying to obtain flour and to determine and evaluate the effective diffusion coefficient, get the activation energy and the thermodynamic properties in drying temperatures of 45, 55, 65 and 75 °C. The experiment was conducted Instituto Federal Goiano - Campus Rio Verde, the guava was purchased in local shops in the city of Rio Verde Goiás, in the commercial maturity. Among the analyzed models, Midilli was the best to represent the drying phenomenon. The effective diffusion coefficient increased with increasing temperature and the activation energy for liquid diffusion drying was 37,207kJ mol-1. The enthalpy and entropy increased with increasing drying temperature. While the Gibbs free energy increased with increasing drying temperature.

Remediation of organic pollutant from the aqueous environment using in-house fabricated polyaniline-based hybrid composite (PANI-MnPBA/NiCoMnS) materials

Polyaniline-based hybrid material (PANI-MnPBA/NiCoMnS) was prepared by hydrothermal-solvothermal approach. Synthesized hybrid material was characterized through FTIR-spectroscopy, p-XRD, SEM, EDX, BET, and Zetasizer techniques. Hybrid material as adsorbent for removal of Congo red (CR) from water system showed excellent results such as 98 % removal efficiency and 254 mg/g adsorption capacity. Furthermore, various studies like adsorption isothermal, kinetic, thermodynamic, and statistical analysis were performed to understand the adsorption phenomenon. From various kinetic models, pseudo-first and second-order kinetic models, intra-particle and liquid film diffusion kinetic models, pseudo-first-order kinetic model, and liquid-film diffusion kinetic model both are most suitable for explaining the adsorption phenomenon due to the greater value of R2 (0.955) for CR. According to these kinetic models, physio-sorption and diffusion play a basic role in the adsorption of CR. Moreover, ΔG (-1779.508 kJ mol−1) and ΔH (61,760.889 kJ mol−1) values explained the spontaneous and exothermic nature of the adsorption process, respectively. Furthermore, for support of the adsorption mechanism via electrostatic attractions before and after the adsorption process FTIR results of as-synthesized adsorbent were measured (NH peaks before 3668.88, after 3541.41 cm−1). These results confirm electrostatic attraction for the adsorption process. Finally, the statistical model was added (n < 1), according to this model, adsorption follows a multi-anchorage approach and adsorbent contains enough sites for adsorption of CR.

Simultaneous removal of triadimefon and dinotefuran by a new biochar-based magnesium oxide composite in water: Performances and mechanism

In recent years, the ecological security has been seriously threatened by the residues of pesticides in the environment. In this study, a new biochar-based magnesium oxide composite (MTBC) was successfully prepared using Traditional Chinese Medicine residues and MgCl2 solution, and then applied for the removal of triadimefon (TDF) and/or dinotefuran (DIN) in water. Batch experiments results indicated that 86.42 and 87.86 % of TDF and DIN removals could be obtained by MTBC within 120 min, respectively. The TDF adsorption process was proved to be well fitted with the pseudo-second-order kinetic, Elovich, liquid film diffusion, Intra-particle diffusion and Langmuir isothermal models. The TDF adsorption by MTBC was a spontaneous endothermic reaction, and chemical adsorption process was dominant. The inhibitory of the coexisting anions on TDF removal followed the order of SO42−＜Cl−＜HPO43−＜HCO3–. Both TDF and DIN could be simultaneously removed by MTBC at the certain concentrations levels. The possible removal mechanism for the adsorption of TDF and DIN by MTBC was proposed, both TDF and DIN were rapidly distributed and adsorbed on MTBC surface, then diffused into the interior pores structure and were finally adsorbed on MTBC through various reaction processes. The TDF removal process might be involved with hydrogen bonding, π-π interaction, pore filling and electrostatic interaction, while DIN removal might be involved with hydrogen bonding, pore filling and electrostatic interaction. These findings suggested that biochar-based magnesium oxide composite was an effective adsorbent for the remediation of agricultural effluents containing TDF and DIN.

Improved engineering model for water absorption in softwoods

Modeling of moisture transfer in porous materials is typically partitioned into liquid transport and vapor diffusion. Coefficients for liquid transport are often derived from laboratory measurements of water absorption by partial immersion. Although the assumption that capillary liquid transport is dominant while vapor diffusion is negligible is a reasonable assumption for mineral-based materials, recent work indicates that it is not representative of water absorption in wood across the grain. This article builds on earlier work and develops an improved engineering model for liquid water transport in softwoods. The approach uses a constant liquid diffusivity value, relies primarily on ordinary hygrothermal property measurements, and partitions vapor and liquid transport in a practical way that is informed by current understanding of wood–water interactions. The model is optimized using one-dimensional simulations calibrated against measured water uptake across a range of softwood species. Laboratory measurements were conducted to investigate key properties of eastern white cedar, which had the highest relative error in a previous version of the model, and to examine the practicality and relevance of vacuum saturation and free saturation for southern yellow pine. The model accuracy is improved by paying closer attention to the moisture storage function and capillary saturation value.

Optimizing Mass Transfer in Multiphase Fermentation: The Role of Drag Models and Physical Conditions

Detailed knowledge of the flow characteristics, bubble movement, and mass transfer is a prerequisite for the proper design of multiphase bioreactors. Often, mechanistic spatiotemporal models and computational fluid dynamics, which intrinsically require computationally demanding analysis of local interfacial forces, are applied. Typically, such approaches use volumetric mass-transfer coefficient (kLa) models, which have demonstrated their predictive power in water systems. However, are the related results transferrable to multiphase fermentations with different physicochemical properties? This is crucial for the proper design of biotechnological processes. Accordingly, this study investigated a given set of mass transfer data to characterize the fermentation conditions. To prevent time-consuming simulations, computational efforts were reduced using a force balance stationary 0-dimension model. Therefore, a competing set of drag models covering different mechanistic assumptions could be evaluated. The simplified approach of disregarding fluid movement provided reliable results and outlined the need to identify the liquid diffusion coefficients in fermentation media. To predict the rising bubble velocities uB, the models considering the Morton number (Mo) showed superiority. The mass transfer coefficient kL was best described using the well-known Higbie approach. Taken together, the gas hold-up, specific surface area, and integral mass transfer could be accurately predicted.

Oxidative Molecular Layer Deposition of Conductive PEDOT Coatings Onto Polymer Sponges to Form Compressible Porous Electrodes

The formation of compressible porous sponge electrodes is appealing to overcome liquid phase diffusion in electrochemical applications including energy storage, water desalination, and electrocatalysis. Previous work has employed wet chemical synthesis to deliver conductive materials into porous polymer sponge supports, but these approaches struggle to produce functional electrodes due to (1) poor electrical connectivity of the conductive network and (2) mechanical rigidity of the foam after coating. In this work we employ oxidative molecular layer deposition (oMLD) via sequential gas-phase exposures of 3,4 ethylenedioxythiophene (EDOT) and molybdenum pentachloride (MoCl5) oxidant to coat polyurethane sponges with electrically-conductive and redox-active poly(3,4 ethylenedioxythiophene) (PEDOT) coatings. We analyze the oMLD deposition on compressible polyurethane sponges and modify the reaction conditions to obtain mechanically compressible and electrically conductive sponges. We specifically identify the importance MoCl5 dose time to enhance the conductivity of the sponges and the importance of EDOT purge time to preserve the mechanical properties of the sponges. This approach produces an electrically conductive PEDOT network within the sponge support with minimal impact on the sponge’s mechanical properties, offering advantages over wet-chemical synthesis approaches. The compressible, conductive sponges we generate have the potential to be used as compressible electrodes for water desalination, energy storage, and electrocatalysis.

Rapidly achieving high-performance joining of single crystal superalloy and powder metallurgy superalloy via partial transient liquid phase diffusion bonding

A rapid and high-performance partial transient liquid phase diffusion bonding process has been proposed for the DD5 single crystal superalloy and the FGH96 P/M superalloy via a mixture of NiTi alloy and FGH96 P/M superalloy powders as interlayer. During the bonding process, isothermal solidification and homogenization of the joint were achieved through a rapid diffusion mechanism of short-range and large-area between the liquid phase of NiTi and the FGH96 particles and the base material. When bonded at 1170 °C only for 60 min of the holding time, isothermal solidification and homogenization of the joints were completed. The isothermal solidification joint consisted of a polycrystalline zone with γ/γ′ structure similar to that of FGH96 and an epitaxial growth zone (EGZ) derived from DD5. Compared with traditional brazing and transient liquid diffusion bonding process (TLP), no brittle compounds and eutectics of Si and B were presented in the joint, which ensured the joint with excellent mechanical properties. With the increase of holding time, both the tensile strength and elongation was significantly increased on account of the reduction of η-Ni3Ti. When the joints were bonded at 1170 °C for 60 min, the elevated temperature strength of 650 °C reached 880.7 MPa, which was more than 80 % and 60 %o that of the DD5 and FGH96, respectively.

Ruggedness test made with mortars by free water intake test

Capillary movement in porous building materials is modelled by unsaturated flow. Material property needed for the calculations is liquid water diffusivity which is usually estimated by water absorption coefficient and capillary saturation moisture content. While determining of water absorption coefficient can be done according to EN-ISO 15148:2002 there is still lack of knowledge about sources of uncertainty in the experiment. In this paper author presents results of ruggedness tests done with mortar. The sources of errors investigated here was the shape and water inflow area of the specimen. Some specimens were also deprived of side sealing and sealing of upper surface as it was known to have impact on results. Results shows there is no considerable impact on measured capillary properties if the specimen sides are sealed or not. Nor does affect the immersed surface area of the specimen. The shape of the immersed surface instead has significant impact on values of both water absorption coefficient and capillary saturation of the specimen.

Graphite Nanoplatelets Nanostructured Films as Multifunctional Protective Layer in Kevlar/Nomex Sandwich Composites

In the aerospace sector, structural and non-structural composite components are usually subjected to a wide range of environmental conditions. Among all, moisture can seriously damage these materials’ performance, reducing their mechanical, thermal, electrical, and physical properties as well as their service time. Lightweight protective barrier coatings capable of reducing the diffusion of gases and/or liquids in a material can improve the material’s resistance in humid environments. In this work, nanolamellar nanocomposites characterized by a high in-plane orientation of nanoplatelets have been employed as protective coatings for Kevlar sandwich panels, reproducing the construction of a nacelle engine. The effectiveness of the protection against water uptake of nanocomposites reinforced with graphite nanoplatelets (GNPs) at high filler contents (70, 80 and 90 wt%) has been investigated using moisture uptake and Ground-Air-Ground (GAG) tests in an environmental chamber. GNP coatings effectively work as barrier by generating highly tortuous paths for molecule diffusion. Results showed a dependence of the absorption on the coating composition and inner structure. Films @70 wt% GNPs showed the best protection against moisture uptake by delaying the phenomenon and reducing the absorption by −80% after 3 days and −35% after 41 days.

The Preparation, Microstructure, and Wet Wear Properties of an Fe55-Based Welding Layer with the Co-Addition of 0.01 wt% CeO2 and 1.5 wt% SiC Particles Using the Plasma Beam Spraying Method

Severe erosion wear is found on valve spools, which threatens the safety and reliability of these units. The use of the plasma beam spraying surfacing method can significantly improve the corrosion resistance and sealing performance of hydraulic valve spools, reduce material waste, and reduce maintenance costs. The effects of the co-addition of CeO2 and SiC particles on the morphology, surface cracks, microstructure, precipitated phases, and wear property of plasma-beam-sprayed Fe55-based coatings on 1025 steel were investigated using OM, EDS, ultra-deep field microscopy, and a wet sand rubber wheel friction tester, respectively. The dendrite exhibited a directional growth pattern perpendicular to the substrate and the transitional states of the microstructure with the co-addition of CeO2 and SiC particles. CeO2 or SiC reduced the liquid phase diffusion coefficient DL of Cr and C and resulted in a decrease in the G/R ratio. The dendrites changed into equiaxed grains. The main phase composition of the Fe55 welding layer was Cr7C3, γ-Fe. The martensite in the surfacing layer and the carbides formed Cr7C3, which can improve the hardness of the surfacing layer. The grain boundaries consisted mainly of a reticular eutectic structure. The uniform distribution of the Cr7C3 hard phase in the Fe55+1.5 wt% SiC+0.01 wt% CeO2 resulted in a uniformly worn surface. The sub-wear mechanisms during the friction process were micro-ploughing and micro-cutting. The hardness and toughness of Fe55+1.5 wt% SiC+0.01 wt% CeO2 were well-matched, avoiding excessive micro-cutting and microplastic deformation. A low content of CeO2 could lead to the formation of equiaxed grain and effectively improve the uniformity of the microstructure. The wear-resistant layer of Fe55+1.5 wt% SiC+0.01 wt% CeO2 can effectively improve the service life and long-term sealing performance of the valve spools.

α-PW11Fe(Co/Ni)/BC derived carbon fiber based nanocomposites for high efficiency electromagnetic wave absorption via synergistic effects of polarization and conductance

In order to enhance the wave-absorbing performance of dielectric/carbon fiber based wave-absorbing materials and explore the dissipative mechanism of electromagnetic wave (EMW), this study utilizes liquid diffusion of K4PW11O39Fe(III)(H2O) (α-PW11Fe), K5PW11O39Co(II)(H2O) (α-PW11Co), K5PW11O39Ni(II)(H2O) (α-PW11Ni) and bacterial cellulose (BC), as well as high temperature carbonization strategy to prepare polycrystalline polyphase transition metals and their compounds with three dimensional porous conductive network structure loaded carbon fiber based nanocomposites wave-absorbing materials. By changing the element type, drying mode and filling amount, we can achieve the tunability of electromagnetic parameters and absorbing properties. Impressively, the best synthesized sample 20 %-α-PW11Ni/BC derived carbon fiber based nanocomposites has excellent EMW absorption properties, with a maximum reflection loss (RL) of -68.1 dB at 2.6 mm matching thickness. The effective absorbing bandwidth (EAB) is 7.2 GHz, and the RL less than -10 dB in the frequency band of 2.2–5.0 mm thickness is 5.3 to 18.0 GHz. The excellent absorbing performance is attributed to the synergy of polarization and conductance, balanced impedance matching, good interface/dipole polarization, and multiple reflections and scattering. Therefore, the prepared composite has a broad application prospect in the field of EMW absorption, and provides a new idea for the design of new efficient absorbing materials.

Preparation and Characterization of Iron Oxide Nano-adsorbent by Enteromorpha Flexuosa Algae obtained from Yanbu Red Sea, Saudi Arabia

Water contamination caused by toxic cadmium metal ions is a worldwide problem. There is a need to explore new methods of cadmium removal from water. The green algae Enteromorpha flexuosa, obtained from the Red Sea in Yanbu, Saudi Arabia, was used to prepare iron nanoparticles. TEM, FT-IR, XRD, and SEM techniques were used to characterize the prepared nanoparticles. The prepared nanoparticle's surface was rough, with nanoparticle sizes ranging from 10 to 50 nm. The developed nanoparticles were used to adsorb cadmium ions from water in batch mode. With a 25.0 µg/L concentration, a temperature of 25˚C, 7.0 pH, 60 minutes contact time and 0.5 g/L dose, the maximum removal of cadmium was 48.2 µg/g. The sorption efficiency was measured using the Dubinin-Radushkevich, Temkin, Langmuir and Freundlich models. The amounts of ΔG° were -8.0, -9.93 and -12.24 kJ/mol while the values of ΔS° and ΔH° were -30.96 x 10-3 kJ/mol and 37.79 x 10-2 kJ/mol. These data confirmed the endothermic nature of cadmium metal ions removal. Along with the liquid film diffusion process, the adsorption adopted the kinetics of pseudo-second-order type. The recorded adsorption method is fast, cost-effective, and environmentally friendly and can be applied for testing the elimination of cadmium metal ions in natural waters.

Molecular dynamic study on the transport properties of ionic liquids in ZTC porous carbon materials

The adsorption and diffusion behavior of ions within electrodes have a significant impact on the energy density and charging/discharging speed of supercapacitors. Zeolite-Templated Carbon (ZTC) material, a type of porous carbon material characterized by well-defined pore shape and spatial structure, is recognized as a promising electrode material owing to its numerous advantages. This study employs molecular dynamics simulations to investigate the diffusion and adsorption profiles of ionic liquids [EMI][BF4] in different types of ZTC materials as electrodes. Additionally, the effect of ion size, pore dimension, pore shape, and the properties of the adsorbed ions are discussed. The degree of confinement (DOC) and ion diffusivity are thoroughly analyzed to elucidate the transport behavior of ions within the ZTC pores. The results demonstrate that the diffusion coefficient and degree of confinement of ionic liquids predominantly depend on the anion size and the pore size of the porous carbon. Surprisingly, in certain cases, larger anions exhibit enhanced diffusion ability and adsorption effect. These findings unravel the underlying transport mechanism of ions in ZTC materials and provide valuable theoretical insights for the application of ZTC materials as electrodes in the field of supercapacitors.

Optimization of leaching parameters for the extraction of copper from hematite-dominated copper ore using Response Surface Methodology (RSM)

The optimization of recovery of copper from Akiri hematite-dominated copper ore using hydrometallurgy was investigated in this study. The Akiri copper ore deposit hosts a high-grade copper mineral from which copper metal can be extracted. However, the ore is dominated by gangue minerals that need to be mechanically reduced for efficient copper recovery. The purpose of this study is to optimize the extraction of the metal from hematite-dominated copper ore. The experiments that were carried out in the course of this study include crushing, pulverization,mineralogical and chemical characterizations of the sample and sulpheric acid leaching. Response surface methodology was used to optimize the system parameters namely;temperature, concentration of the leachant and contact time so that an efficient method will be developed for the extraction of copper.Chalcopyrite, covellite and cuprite are the copper minerals while the gangues minerals were quartz ,mica, hematite,etc.on the characterization of the copper ore. The major oxides in the ore are hematite ,copper oxide and silica and revealed that the ore contains 4.61% copper and 65.8% iron. Effect of three independent factors like concentration ,temperature and contact time for copper extraction from the hematite-dominated copper ore was studied.Central composite design method was applied to the proposed quadratic model that connect the factors used for best copper extraction at the best process condition. The work shows that concentration of the acid was the best efficient factor for copper extraction compare to temperature and contact time. This may be as a result of high value of F-statistics for the concentration of the leachant, which effects to high level of copper extraction.Experimental and predicted values for weight loss from the copper ore were obtained as 39.10% and 39.03% at optimum conditions, respectively. The optimum conditions of 1.5M acid concentration, 90oC reaction temperature and 90minutes contact time were obtained and from which 6.64%Cu at recovery of 92.0% and 2.31%Fe was obtained without stirring. Also, the ore was subjected to leaching with stirring at 400rpm with the optimum conditions obtained to know the effect. The grade obtained was 7.84% Cu at recovery of 83.51% and iron content 5.47%. This shows that leaching without stirring is the best option against leaching with stirring to extract the copper and to reduce the iron and other gangues contents in the copper ore.The activation energies were estimated as 13.20kJ/mol and 22.67kJ/mol for liquid film diffusion and diffusion product layer respectively, the values indicate that the leaching rate is controlled by diffusion process.

The solid effect of dynamic nuclear polarization in liquids - accounting for g-tensor anisotropy at high magnetic fields.

In spite of its name, the solid effect of dynamic nuclear polarization (DNP) is also operative in viscous liquids, where the dipolar interaction between the polarized nuclear spins and the polarizing electrons is not completely averaged out by molecular diffusion on the timescale of the electronic spin-spin relaxation time. Under such slow-motional conditions, it is likely that the tumbling of the polarizing agent is similarly too slow to efficiently average the anisotropies of its magnetic tensors on the timescale of the electronic . Here we extend our previous analysis of the solid effect in liquids to account for the effect of -tensor anisotropy at high magnetic fields. Building directly on the mathematical treatment of slow tumbling in electron spin resonance , we calculate solid-effect DNP enhancements in the presence of both translational diffusion of the liquid molecules and rotational diffusion of the polarizing agent. To illustrate the formalism, we analyze high-field (9.4 T) DNP enhancement profiles from nitroxide-labeled lipids in fluid lipid bilayers. By properly accounting for power broadening and motional broadening, we successfully decompose the measured DNP enhancements into their separate contributions from the solid and Overhauser effects.

Investigation on interphase mass transfer coefficient of a deformable bubble with density contrast using phase-field lattice Boltzmann method

The gas–liquid mass transfer process with density contrast is modeled in this paper using a phase-field Lattice Boltzmann (LB) method. In this method, the phase-field model used to calculate the flow field and the continuous species transfer model used to calculate the concentration distribution are coupled by introducing the divergence condition of the velocity in the presence of mass transfer into the Allen-Cahn equation. For a deformable bubble rising in stagnant liquid, a two-dimensional parameter dependence study is conducted and the results indicate that an increase in initial diameter, as well as a decrease in liquid diffusion coefficient or liquid viscosity, can improve the steady-state value for the Sherwood number, whereas the distribution coefficient has a little impact on this steady-state value. Furthermore, a correlation originally proposed by Takemura and Yabe (1998) modified with a shape factor can be used to predict the steady-state Sherwood number in the numerical results.