Internal Diffusion Resistance Research Articles

Oxidation kinetics of typical high FeO ferrous spinels

In this study, the isothermal oxidation kinetics of magnetite (OM), high-Mg magnetite (MM), titanomagnetite (TM), and chromite (CM) were investigated by applying thermogravimetry (TG) analysis at temperatures ranging from 1073 K to 1223 K. The results show that different high-FeO spinels possess distinct oxidizability. The oxidation process of OM in the temperature range from 1073 K to 1223 K is faster than others, followed by MM and TM. While CM exhibits the poorest oxidizability, and generally undergoes complex phase transitions. In the initial stage of oxidation, high FeO spinels have a higher oxidation rate due to the surface oxidation of spinel particles. However, the oxidation rate gradually declines in the later stages of oxidation due to increased internal diffusion resistance. The results of oxidation kinetics indicate that the initial oxidation stage of four spinels can be described as random nucleation and subsequent growth mechanism. The average apparent activation energies of the initial oxidation stage of OM, MM, TM, and CM are 25.09 kJ/mol, 32.39 kJ/mol, 58.10 kJ/mol, and 82.42 kJ/mol, respectively.

Accelerated Diffusion of a Copper(I)-Functionalized COF Packed Bed Reactor for Efficient Continuous Flow Catalysis.

Flow chemistry provides a neo-orientation for the research and development of chemical technology, in which heterogeneous continuous catalysis based on packed beds can realize rapid separation and recycling. However, options for heterogeneous catalysts are still limited. In this work, we gradually grow covalent organic frameworks (COFs, TpBpy) on the surface of a silica gel (SiO2)-supported substrate to obtain a stable copper(I)-chelated high-loading heterogeneous catalyst (SiO2@CuI-TpBpy). SiO2@CuI-TpBpy shows high catalytic activity in three-component Huisgen 1,3-dipolar cycloaddition, giving the corresponding triazoles with excellent yields and reposeful recyclability under batch conditions. The structures of the catalysts remain steady, and the copper contents are basically unchanged after five cycles. Then, the catalysts are successfully applied for three-component heterogeneous catalysis in a one-pot continuous flow to prepare rufinamide in 89% yield for 24 h stably and efficiently with mere traces of copper ions remaining. More importantly, the catalytic system reveals a minuscule effect of catalyst particle size on internal diffusion. This COF encapsulation strategy presents a new possibility for the design of industrial heterogeneous catalysts with high metal loading and low internal diffusion resistance.

Simulating the Moisture Diffusion and Evaporation of Sawdust during Convective Drying using the Spatial Reaction Engineering Approach

AbstractThe spatial reaction engineering approach (S‐REA) was used to simulate hot air drying of sawdust. The studies extended the previous work reported in literature where the sawdusts were dried using hot air at 70 °C, 80 °C, and 90 °C. The simulated results were found to agree well with the experimental moisture content (R2 > 0.98) and temperature (R2 > 0.82) profiles. In a further analysis using S‐REA, the spatial profiles of moisture content and vapor concentration were generated to understand better the physics behind. Simulation also revealed that the external mass transfer resistance was more dominant as compared to the internal diffusion resistance. The vapor concentrations were observed peaked at time range of about 10 800– 18 000 s and dropped thereafter upon further heating. This observation could be supported by the variation in the vapor effective diffusivities where peak diffusivity values typically occur after most of the moisture evaporates towards the end of drying.

Alumina microspheres for the adsorption of fatty alcohols containing oxygenates in Fischer-Tropsch synthetic oils

The efficient and economical removal of oxygenated compounds from Fischer-Tropsch synthetic oil is vital to the promotion of high-quality chemical development in the coal chemical industry. In this study, alumina microspheres with high specific surface area, high pore capacity, and small particle size were prepared. The adsorption thermodynamics, adsorption kinetics, and column adsorption experiments were systematically conducted on various fatty alcohols bearing different carbon numbers, in mixtures of α-olefins and alkanes with different carbon numbers. The competitive adsorption behavior between weakly polar, oxide-containing methyl acetate and 12-alcohols on an alumina surface was investigated to better reduce the actual system. The Freundlich model exhibited a better fit than the Langmuir model. The adsorption kinetics and proposed first-order kinetic equations fitted better to the Crank model. Comparing the adsorption effect of commercial alumina and the alumina microspheres prepared in this study, it was observed that a smaller particle size and larger pore volume reduced the internal and external diffusion resistance of adsorption, and a larger specific surface area provided more adsorption sites for the adsorption of the oxide-containing compounds. The competitive adsorption behavior of fatty alcohols and methyl acetate on the surface of γ-alumina was explored using a combination of density functional theory (DFT) calculations and experimental techniques. The results of this study can prove to be extremely useful for the efficient removal of oxide-containing compounds from Fischer-Tropsch synthetic oils.

Textural effect of Pt catalyst layers with different carbon supports on internal oxygen diffusion during oxygen reduction reaction.

One way to address the cost issue of polymer electrolyte membrane fuel cells (PEMFCs) is to reduce the amount of platinum used in the cathode catalyst layers (CLs). The oxygen mass transfer resistance of the cathode CLs is the main bottleneck limiting the polarization performance of low Pt-loading membrane electrodes at high current densities. Pt nanoparticles, ionomers, carbon supports, and water in cathode CLs can all affect their oxygen mass transfer resistance. From the perspective of carbon supports, this paper changed the texture of CLs by adding carbon nanotubes (CNTs) or graphene oxide (GO) into carbon black (XC72) and studied its impact on the oxygen mass transfer resistance. A mathematical model was adopted to correlate total mass transfer resistance and internal diffusion efficiency factor with CL structure parameters in order to determine the dominant textural effect of a CL. The results show that adding 30%CNT or 20GO to carbon black of XC72 improved the electrocatalytic performance and mass transfer capability of the composite carbon-supported Pt catalyst layers during oxygen reduction reaction. The study further reveals that the smaller particle-sized carbon material with tiny Pt nanoparticles deposition can minimize the internal oxygen diffusion resistance. A less dense CL structure can reduce the oxygen transfer resistance through the secondary pores. The conclusion obtained can provide guidance for the rational design of optimal cathode CLs of PEMFCs.

Carbonic Anhydrase-Embedded Hydrogen-Bonded Organic Frameworks Coating for Facilitated Offshore CO2 Fixation.

Exhausted emission of carbon dioxide (CO2 ) from ships or offshore platforms has become one of the major contributors to global carbon emissions. Enzymes such as carbonic anhydrase (CA) have been widely used for CO2 mineralization because of their high catalytic rate. However, CA in seawater is easy to inactivate and difficult to reuse. Immobilization would be a feasible solution to address the stability issue, which, however, may cause an increase of internal diffusion resistance and reduced catalytic activity. In this regard, design of high-performance biocatalysts for acquiring high catalytic activity and stability of CA is highly desirable. Herein, a monolithic catalyst of Filler-CA@Lys-HOF-1 (FCLH) was prepared by chemical sorption of CA on the surface of the Filler followed by the coating of Lys-HOF-1. The highest catalytic activity of FCLH was obtained by regulating the amount of HOF-1 monomer added. Due to the protection of Lys-HOF-1, the FCLH showed good tolerance against acidity and salinity, which could retain about 80.2 % of the original activity after 9 h incubation in simulated seawater. The catalytic activity of FCLH could retain 85.4 % of the initial activity after 10 cycles. Hopefully, our study can provide a promising biocatalyst for CO2 mineralization, which may drive down carbon emissions when used for CO2 capture and conversion on offshore platforms.

Intramolecular synergistic catalysis of ternary active sites of imidazole Ionic-liquid polymers immobilized on nanosized CoFe2O4@polystyrene composites for CO2 cycloaddition

The cycloaddition reaction of CO2 with epoxides is challenging, thereby requiring the development of environmentally friendly catalysts. Herein, a strategy was developed to construct a multifunctional heterogeneous magnetic catalyst (MPNPs-[ImR2NH2][ZnBr3]) of aminoethyl imidazole metal halide ionic liquids coated on nano-sized CoFe2O4@polystyrene for CO2 cycloaddition. The created catalytic system displayed the intramolecular synergy of ternary active sites (Zn2+, Br−, and –NH2), as well as coupling of catalysis and magnetic separation. In the absence of co-catalyst and solvent, MPNPs-[ImR2NH2][ZnBr3] exhibited excellent catalytic performance for CO2 cycloaddition (99.92% yield and 100% selectivity) at 120 ℃ with 0.16 mol% catalyst dosage in 2.5 h. By appropriately increasing the reaction duration and catalyst dosage, 98.83% conversion and 99.26% selectivity were achieved even at mild conditions of 60 °C and 0.1 MPa. After 10 cycles of reuse, the recycled MPNPs-[ImR2NH2][ZnBr3] demonstrated the same high-efficiency activity as the fresh catalyst, as well as excellent stability and magnetic separation. Based on the density functional theory (DFT) calculations, the intramolecular synergy of ternary active sites and the catalytic mechanism of bimolecular activation based on the multifunctional structure were proposed. This excellent catalyst was attributed to the intramolecular synergy of ternary active sites, large loading of active centers, lower internal diffusion resistance, the inert protective effect of polystyrene layer and the easily magnetic separation of CoFe2O4, highlighting a new direction for green catalytic chemistry.

Co–Pyridinic-N Bond Constructed at the Interface of CoxP and N-Doped Carbon to Effectively Facilitate Oxygen Reduction

The construction of bonding interfaces between cobalt-base phosphides and N-doped carbon is considered an effective means to promote ORR catalytic performance. However, the role of different nitrogen configurations in promoting the ORR performance of cobalt-base phosphides is currently unknown. Herein, the honeycomb-like CoxP@N-doped carbon catalyst was constructed to systematically investigate the effect of different nitrogen configurations on improving the catalytic performance of CoxP. Systematic experimental investigations and density functional theory (DFT) calculations indicate that the interaction of Co with pyridinic-N not only regulates the atomic Co coordination environment but also induces strong orbital hybridization between N-p orbitals and Co-d orbitals, significantly increasing the electron density on pyridinic-N sites, which greatly increases the attraction to oxygen-containing intermediates and lowers the reaction energy barrier, thus promoting the catalytic activity for ORR. Furthermore, honeycomb morphology not only reduces the internal diffusion resistance of reactants and products as well as the relative concentration of surface reactants but also exposes more accessible active sites and increases the contact area with the electrolyte, thus greatly enhancing the oxygen reduction reaction. As expected, the as-prepared catalyst exhibits ultrahigh ORR activity with a half-wave potential of 0.88 V, which is superior to that of the noble metal Pt and most previously reported non-noble metal catalysts. This study perfectly explains why cobalt-base phosphide embedded in N-doped carbon can improve its ORR catalytic performance.

Polyethyleneimine/polydopamine-functionalized self-floating microspheres for caramel adsorption: Interactions and phenomenological mass transfer kinetics

A polyethyleneimine/polydopamine-functionalized self-floating microsphere (EHGM/PDA/PEI) bears an etched hollow glass microsphere as a support, polydopamine as an interfacial cross-linking “glue”, and polyethyleneimine as a functional monomer was fabricated and used as a decolorization sorbent for sugarcane juice. The advantages of EHGM/PDA/PEI for sugarcane juice decolorization were attributed to its richness of target polyethyleneimine monomers, well-connected and abundant three-dimensional network-like aperture structure, and nontoxicity. Moreover, EHGM/PDA/PEI has excellent self-floating performance to allow separation from the adsorption system after decolorization and may have a faster separation speed and lower energy consumption than conventional solid–liquid separation methods. Synthetic caramels were used as model colorants of sugarcane juice to assess EHGM/PDA/PEI performance. The adsorption capacity of EHGM/PDA/PEI for caramels was 18.36 mg/g with a removal efficiency of 91.80% in the adsorption equilibrium state. The interaction mechanisms revealed that the caramel adsorption on EHGM/PDA/PEI was mostly mediated by protonated amine groups, followed by electron sharing. Two layers of caramels adhered onto EHGM/PDA/PEI were mainly mediated by electrovalent bonds between carboxylate and protonated amine. On average, one caramel molecule can be shared by 3–4 protonated amine groups of EHGM/PDA/PEI, which suggests a parallel sorption orientation. Four phenomenological mass transfer models [external diffusion resistance (EXTDR), internal diffusion resistance (INTDR), EXTDR–INTDR mixed, and adsorption onto active sites (AOAS)] proposed new and unique insights into the dynamic properties of the adsorption process.

Insights into mass transfer mechanism and micro-interaction of melanoidin adsorption on polyethyleneimine-functionalised pomelo-peel-derived aerogel

Melanoidins are recalcitrant colouring and polluting polymers present in the effluent streams of molasses-based distilleries. Adsorption is the most prospective technology with ease of operation and high efficiency. Herein, the removal of melanoidins from spent wash was investigated by synthesising a polyethyleneimine (PEI) functionalised pomelo-peel (PP) derived aerogel (PEI-PPA). The PEI-PPA is distinguished by the porous network structure and abundant accessible functional groups (mainly protonated primary amine) that are conducive to the elimination of colouring contaminants (melanoidins). The incorporation of PEI into supporting matrices (i.e., PP–derived aerogel) effectively improved the melanoidin adsorption capacity (from a previous-best research of 230 mg/g to the current 615.70 mg/g), while the melanoidin removal rate reached 92.36 %. The independent gradient model and Hirshfeld surface analysis were used to investigated the possible electroweak interaction relationship between PEI-PPA and melanoidin. By analysing the number of melanoidin molecules bonded to each active site using a novel double-layer adsorption model, a mixed inclination (parallel and non-parallel orientation) of melanoidin onto the PEI-PPA surface was found. For the two mass transfer models fitted results, the adsorption onto the active sites (AOAS) model better described the behaviour of melanoidin adsorption by PEI-PPA than the external diffusion resistance–internal diffusion resistance (EDR–IDR) mixed model under the same conditions, revealing the AOAS was rate-controlling during the mass transfer process. AOAS both contained chemisorption and physisorption. The calculated rates of chemisorption were far higher than those of physisorption before equilibration, indicating chemisorption was main the rate-determining step. Altogether, this work proposed an effective conversion for PP into bio-adsorbent and provided a detailed analysis of mass transfer mechanism.

Effective melanoidin adsorption of polyethyleneimine- functionalised molasses-based porous carbon: Adsorption behaviours and microscopic mechanisms

Sugar industry is an integral part of the food and agriculture sector of the national economy. Cane juice decolourisation is a crucial process in sugar production that directly impacts the final colour value of the sugar. However, the chemicals used in traditional methods may be harmful for food safety. Thus, advanced and effective alternatives methods should be developed to further address the problems on sugar production and quality. In this study, polyethyleneimine-functionalised molasses-based porous carbon (PMPC) was prepared from cane molasses, and was reversely applied to remove melanoidins from cane juice. The melanoidin removal efficiency by PMPC was 91.66% with the adsorption capacity of 550.00 mg/g in the adsorption equilibrium state. From the adsorption thermodynamics analysis, the adsorption process of melanoidins onto PMPC was spontaneous and endothermic. Analysis of the interaction mechanisms demonstrated that the successful adsorption of melanoidins by PMPC was mainly achieved through the electrostatic interations and other weak interactions (hydron-bond interaction), and a melanoidin molecule can be bonded with three to four protonated amine groups of PMPC. In addition, the mass transfer behaviour of the melanoidins adsorbed onto PMPC was determined using the mixed model of external and internal diffusion resistance, and the active-onto-site adsorption model. The results showed the melanoidins adsorbed by PMPC was a multilayer adsorption process dominated by chemisorption. Therefore, PMPC was proved to be an ideal adsorbent for cane juice decolourisation, with the advantages of green, high efficiency, and recyclability.

Detecting voltage shifts and charge storage anomalies by iron nanoparticles in three-electrode cells based on converted iron oxide and lithium iron phosphate

Noticeable voltage shifts have been observed in the charge/discharge profiles of a three-electrode cell with a lithium metal reference electrode and having a deeply lithiated iron oxide (Fe/Li2O) negative electrode galvanostatically cycled in a limited potential range against a positive LiFePO4 counterpart. The origin of such shifts has been attributed to charge storage anomalies in the Fe/Li2O nanocomposite due to characteristic reduced Fe nanoparticle sizes. These shifts also affected the extreme points of the voltage profiles of the positive electrode, which was also independently monitored. A combined evaluation of voltage profile slippages with possible changes in internal resistance and/or Li+ inventory loss, including an aimed analysis of current interruptions at the end of each lithiation/de-lithiation half-cycle to monitor the internal resistance and diffusion resistance coefficient of the Fe/Li2O electrode, has enabled a clarification of its altered charge storage. An asymmetric behaviour of the Fe/Li2O electrode during Li+ uptake/release has been revealed, highlighting a progressive, diffusion-controlled-type voltage drift at low potentials vs. Li+/Li, and an unusual tendency to slight oxidation with capacitive variations during the reverse electrochemical processes at higher voltages, instead.

Simulation of novel jellyfish type of process for bioremediation application

A bioinspired device was fabricated as a sustainable remedial method and its performance as a membrane-enzyme reactor with cyclic ultrafiltration was investigated. The body of the jellyfish-like device was composed of two parts: 1) Jellyfish arms: Mono and co-axial electrospinning have been utilized to synthesize the flexible parts (e.g., multilayer membrane PS-PVDF/PAN/PS-PVDF) used for immobilization of aliphatic degrading enzymes, and 2) Jellyfish tentacles: Hollow fiber membranes were selected for physical immobilization of polycyclic aromatic hydrocarbon (PAH) degrading enzymes. To study the behavior of the membrane/enzyme reactor, the hollow fiber enzyme reactor with pulsation was operated by recycling an enzyme solution to assess ultrafiltration efficiency. A mathematical model was suggested to describe the experimental data obtained in this study to predict the effectiveness of the reactor for PAH removal. When testing the performance of the jellyfish-like device, those equipped with nanofibers with an oil sorption capacity of (10. ±0.7gdilbit/gfiber) were more effective at removing oil particles before they touched the hollow fiber membrane surface. Moreover, the reaction rate measured in a free soluble enzyme and a recirculating immobilized enzyme solution exhibited a slight difference in the kinetic parameter, Km (0.03 and 0.021 mM) due to the internal diffusional resistance. Based on biodegradation studies, a synergistic effect between membrane adsorption, enzymatic degradation, and ultrafiltration was proposed for the removal of anthracene from the column of water.

Hierarchically Structured CA@ZIF-8 Biohybrids for Carbon Dioxide Mineralization.

Carbonic anhydrase (CA) is a powerful biocatalyst for carbon dioxide (CO2) mineralization, of which immobilization is usually used for maintaining its catalytic activity against harsh external stimuli. However, the incorporated materials for CA immobilization would commonly increase the internal diffusion resistance during the catalytic process, thereby decreasing the catalytic efficiency. In our study, poly-L-glutamic acid (PLGA) as the structure regulator was used to induce the synthesis of CA@zeolitic imidazolate framework-8 (CA@ZIF-8) biohybrids. The introduction of PLGA that could coordinate with Zn2+ interfered the crystallization of ZIF-8, thereby changing the morphological structure of CA@ZIF-8 biohybrids. With the increase of PLGA amount from 0 to 60mg, PLGA(x)-CA@ZIF-8 biohybrids were gradually transformed from a dodecahedron structure to a 3D lamellar nano-flower structure, which caused elevated exposed surface area. Accordingly, the loading ratio was increased from 34.6 to 49.8mg gcat-1, while the catalytic activity was elevated from 20.6 to 23.4%. The CO2 conversion rate was enhanced by nearly two folds compared to PLGA(0)-CA@ZIF-8 under the optimized condition. The final CaCO3 yield could reach 5.6mg mgcat-1, whereas the reaction system could remain above 80% of the initial reaction activity after 8 cycles.

Tailoring of ZnFe2O4-ZrO2-based nanoarchitectures catalyst for supercapacitor electrode material and methanol oxidation reaction

Herein, a simple hydrothermal approach was employed to synthesize a homogeneous and compact ZnFe2O4 nanoparticles on the surface of ZrO2 (ZnFe2O4-ZrO2), and it was utilized as a supporting-material for Pt nanoparticles. The fabricated ZnFe2O4-ZrO2 and ZnFe2O4-ZrO2/Pt nanoarchitectures were employed as an electrode material for the supercapacitor cells, and an electrocatalyst for the methanol oxidation reaction, respectively. The Pt nanoparticles were electrochemically deposited on the ZnFe2O4-ZrO2 support. The electrochemical characterizations illustrated that ZnFe2O4-ZrO2 supported Pt was of a peak current density of 104.74 mA/cm2, which was 1.73 more than the peak current density of Pt without the use of nanocomposite support and strong cycling stability of 110 percent after 150 cycles for the methanol oxidation reaction. As a supercapacitor electrode, ZnFe2O4-ZrO2 offered a high specific capacitance of 193.76F/g at a current density of 1.0 A/g, an appropriate rate efficiency (102.4 F/g at current density of 8 A/g), and strong cycling stability of 93 % after 250 galvanostatic charge–discharge revealing the high cycle stability of the nanocomposite. The superb electrochemical behavior of the ZnFe2O4-ZrO2 electrode was ascribed to the low internal charge resistance and ion diffusion resistance. The more ion/electron pathways of diffusion and a suitable contact area with the electrolyte, and the strong synergistic interaction between the components conferred exceptional conductivity and structural durability on the electrode. The results paved the new avenues for nanoengineering of up-and-coming metal-based nanoarchitectures to be utilized in energy storage and conversion systems.

Investigation of local sensitivity for vehicle-oriented fuel cell stacks based on electrochemical impedance spectroscopy

The lifetime of fuel cells is a severe constraint on fuel cell industrialization, which is significantly influenced by the consistency of the fuel cell stack. This paper is the first to measure the impedance of a whole high-power fuel cell stack throughout its ten equal areas based on a multi-channel impedance test system. Based on the equivalent circuit model combined with the relaxation time distribution, the differences in the local polarization dynamics processes of the stack and its sensitivity to working condition variations are analyzed in detail. Additionally, the Pearson correlation between the local voltage and internal state parameters is quantified. The results show that the distribution characteristics of the local polarization dynamics losses are inherent to the stack structure and assembly errors, but are less influenced by the working conditions without extreme conditions. Furthermore, the robust correlations between the local voltage and the internal ohmic resistance and oxygen diffusion resistances in the stack are revealed. More importantly, this study would support the variance assessment of the internal state based on the local voltage, which will have comprehensive applications in controlling fuel cell systems.

Effective Maxwell−Stefan diffusion model of near ambient air drying validated with experiments on Thomson seedless grapes

AbstractWith 8% of the world's grapes being dried into raisins, grape drying constitutes a sizable part of agricultural revenue. The drying process in the developing regions of the world struggles with a lack of reliable drying techniques and rising energy costs. In this work, we report a systematic study to elucidate the intrinsic drying kinetics of Thomson seedless grapes. The grapes are subjected to drying by warm air (40−55°C) rather than hot air (>60°C), which has the advantage of producing the sought‐after green raisins. The air velocity is varied between 0.05 and 0.15 m/s to isolate the effect of external mass transfer resistance. A 1D mathematical model was developed that incorporates the effects of internal diffusion and external mass transfer resistance as well as the effects of temperature and relative humidity on the kinetics and driving forces. In addition, the model incorporates a novel thermodynamic model to describe the vapour pressure of water at the surface of the grape. The uniqueness of the model is that it combines thermodynamics and mass transfer in a single framework. Therefore, the parameters that describe the evaporation are the same parameters that describe the internal diffusion within the matrix, making the model robust. This robust, experiment‐trained model can be reliably transferred to develop detailed computational protocols to model cost‐effective grape drying processes in the field.

Experimental Data and Modeling the Adsorption-Desorption and Mobility Behavior of Ciprofloxacin in Sandy Silt Soil

The improved understanding of the behavior of antibiotics in soil is of great importance due to their environmental hazard and frequent detection. In this work, the adsorption-desorption and mobility behaviors of ciprofloxacin in sandy silt soil, affecting the fate of ciprofloxacin in the environment, were studied by a series of batch tests and column tests. In batch tests, the effects of contact time, initial ciprofloxacin concentration, sandy silt soil dosage, solution pH, and ionic strength on ciprofloxacin adsorption and desorption in sandy silt soil were considered. Adsorption results were satisfactorily modeled, with good fittings to the pseudo-second-order model (R2 > 0.999) and Langmuir model (R2 > 0.991), with the value for Langmuir’s maximum adsorption capacity (qm) 5.50 mg g−1. Ciprofloxacin adsorption decreased sharply by increasing the pH from 7.0 to 10.0 and the ionic strength from 0.01 to 0.2 mol L−1 CaCl2. Comparatively, ciprofloxacin was more readily desorbed from sandy silt soil at alkaline and high ionic strength conditions. Breakthrough curves of ciprofloxacin obtained from the column experiments were described by the two-site model, Thomas model, and Yan mode. Of these models, the two-site model was the most suitable to describe the mobility of ciprofloxacin. The retardation factor (R) obtained in the two-site model was 345, suggesting strong adsorption affinity with ciprofloxacin on the sandy silt soil surface. The results from the Thomas model suggested the extremely small external and internal diffusion resistances. The Yan model was not suitable. Cation exchange interaction, electrostatic interaction, mechanical resistance, entrapment between porous media, and gravity sedimentation were proposed to be the important adsorption mechanisms.

Insight into the Enhanced Removal of Water from Coal Slime via Solar Drying Technology: Dewatering Performance, Solar Thermal Efficiency, and Economic Analysis

In this work, solar drying technology was applied for the deep dewatering of coal slime to save thermal energy and reduce the dust produced during the hot drying process of coal slime. Solar drying technology is used to dry coal slime to realize its resource utilization. The influence of solar radiation intensity and slime thickness is investigated on the drying process. The greater the solar radiation intensity (SRI) is, the faster the drying indoor air and coal slime are heated, and the faster the drying efficiency is. As the slime becomes thinner, the internal water diffusion resistance becomes smaller and the drying efficiency correspondingly becomes faster. In addition, to facilitate the application of coal slime drying in the actual project, the Page model is fitted and found to have a good fit for solar drying coal slime. Meanwhile, the optimal drying conditions are determined by analyzing the energy utilization under different conditions. It is found that the target moisture content of 10% is optimal for coal slime drying with the highest energy utilization. The laying thickness (L) of 1 cm has the highest solar thermal efficiency of 54.1%. More importantly, economic calculation and analysis are conducted in detail on solar drying. It is found that the cost of solar drying (¥38.59/ton) is lower than that of hot air drying (¥ 65.09/ton). Therefore, solar drying is a promising method for the drying of coal slime.

High-performance asymmetric supercapacitor achieved by CoS2 nanoparticles decorated polyaniline functionalized SBA-15-derived mesoporous nitrogen-doped carbon with rod-like architectures

The promising candidates for high-performance electrode materials, transition metal species@N-doped mesoporous carbon composites (M/MO/M(OH)2@NDMCs), were synthesized by carbonization of metal ion-doped polyaniline (PANI) functionalized mesoporous silica SBA-15, followed by etching the mesoporous silica template. The yielded M/MO/M(OH)2@NDMC can be further converted into sulfide via a simple hydrothermal sulfidization treatment. The mesoporous structure, large amount of the accessible electrochemically active nitrogen species, partially graphitic structure, and transition metal compounds of transition metal species@NDMC composites will increase the electronic and ionic conductivity by reducing the internal and ion diffusion resistances resulting in fast diffusion of ions in the electrolyte to the electrode surface. These endowed them good electrochemical performance characteristics for use in supercapacitor electrodes. Correspondingly, NiO/Ni(OH)2@NDMC, Co/Co(OH)2@NDMC, and CoS2@NDMC as the electrodes in 2 M KOH showed specific capacitance of 337, 589, and 1178 F g–1 at 2.0 A g–1, respectively. Furthermore, the assembled asymmetric supercapacitor device utilizing CoS2@NDMC as a cathode exhibited a satisfactory energy storage capability (50 Wh kg–1 at 750 W kg–1) with an admirable cyclic life (retaining ~99% initial capacitance over 6000 repeated cycles). This finding gives these transition metal species@NDMC composites, especially CoS2@NDMC, prospective applications as high-performance supercapacitor electrode materials, where a fast charge/discharge is required.