Addition Of Cetyltrimethylammonium Bromide Research Articles

Theoretical study on the influence of three different surfactants on the binding of laccase with bisphenol A

Laccase catalyzes the formation of phenoxyl radicals as an intermediate in Bisphenol A (BPA) degradation, and certain surfactants can affect the effectiveness of laccase in removing BPA from various effluents, yet the specific molecular details remain unclear. In this study, based on laccase and BPA complex, three surfactants, cetyltrimethylammonium bromide (CTAB), sodium dodecylbenzene sulfonate (SDBS), and TritonX-100 (TX-100), were introduced to construct four systems. We applied MD simulation along with MM-PBSA method to investigate the effects of different surfactants on the binding of laccase with BPA. During the MD simulations, these three surfactants enveloped the enzyme surface to varying degrees, causing the solvent to separate from parts of the laccase surface. The addition of CTAB and SDBS suppressed BPA degradation mainly by influencing the polar solvation free energy and van der Waals (vdW) interactions between laccase and BPA. In contrast, TX-100 promoted the degradation of BPA by reducing polar solvation free energy. This explains why in the laccase-BPA complex system the addition of a certain concentration of TX-100 resulted in a higher degradation rate compared to CTAB or SDBS. Our work clarifies the molecular mechanisms of the interaction between laccase and BPA under the influence of CTAB, SDBS, and TX-100 surfactants, and provides some guidance for laccase degradation of BPA.

Effect of surfactant on dynamics and gas-liquid mass transfer for single carbon dioxide bubbles

In carbonation reaction, the impact of surfactants on the movement and mass transfer behavior of carbon dioxide bubbles were crucial for the production of high-quality silicon dioxide products. The study employed the Matlab image processing system to investigate the shapes, motion velocities, and rise path of single carbon dioxide bubbles within varying concentrations of cetyltrimethyl ammonium bromide (CTAB) solutions. This exploration aimed to elucidate the effect of CTAB on the movement and mass transfer coefficient (MTRC) of single carbon dioxide bubbles. Alterations in the CTAB solution concentration and bubble sizes significantly influenced the mass transfer and movement characteristics of single carbon dioxide bubbles. The conclusion was drawn through the computation of the MTRC of single carbon dioxide bubbles in deionized water and CTAB solutions: the addition of CTAB significantly reduced the mass transfer efficiency of carbon dioxide in deionized water, with the MTRC of CTAB solutions decreasing as the solution concentration increased. Utilizing the stagnant cap model, it can be concluded that CTAB's reduction of the MTRC of carbon dioxide was attributed to the high viscosity of the medium, low bubble velocity, stable flow conditions, and intensified adsorption degree of CTAB molecules at the gas-liquid interface. According to the significant periodic trajectories of single carbon dioxide bubbles in the stable range, the correlation between the trajectories of compressible bubbles in surfactant solution and mass transfer in liquid phase was established, and the previous method based on rigid sphere model was modified. The paper proposed the mechanism of CTAB's influence on single carbon dioxide bubbles, offering crucial theoretical insights into the industrial application of surfactants in the carbonation process for producing silicon dioxide.

Optimization of a Rare Earth and Aluminum Leaching Process from Weathered Crust Elution-Deposited Rare Earth Ore with Surfactant CTAB

Ammonium sulfate is typically employed as a leaching agent in the in situ leaching of weathered crust elution-deposited rare earth ore. However, it is associated with challenges such as low efficiency in mass transfer for rare earth (RE) leaching, high usage of the leaching agent, and prolonged leaching duration. To address the issues mentioned above, the surfactant cetyltrimethyl ammonium bromide (CTAB) was compounded with 2% ammonium sulfate to form a leaching agent in this paper. The effects of CTAB concentration, temperature, pH, and leaching agent flow rate on the rare earth (RE) and aluminum (Al) leaching mass transfer process from RE ore were investigated using chromatographic plate theory. The results revealed that CTAB addition improved the RE mass transfer process while moderately inhibiting the Al mass transfer efficiency. Increasing the temperature and pH of the leaching solution led to higher theoretical plate numbers for RE and Al leaching, lowered theoretical plate height (HETP), and enhanced leaching mass transfer efficiency. However, under high temperature and alkaline conditions, the mass transfer efficiency begins to decrease, indicating that high temperature and alkaline conditions are not conducive to the synergistic enhancement of RE and Al leaching by CTAB. Considering that clay minerals have good pH buffering properties, adjusting the pH of the leaching solution during rare earth ore leaching operations was deemed unnecessary. The optimal mass transfer conditions for leaching RE and Al were identified as 2% ammonium sulfate concentration, 0.00103 mol/L CTAB concentration, pH range of 5.2–5.5 for the leaching solution, 0.6 mL/min leaching solution flow rate, and room temperature. The rare earth leaching mass transfer effect could be enhanced during summer operations.

The Effect of Cetyl Trimethylammonium Bromide Addition as Surfactant in Multiwalled Carbon Nanotube-Based Nanofluid for Quench Medium in Steel Heat Treatment Application

Nanoparticle addition into a fluid can increase the thermal conductivity. Such fluid is commonly called a nanofluid. Due to its improved heat transfer characteristic, nanofluid is widely used as coolant in engine or electronic equipment. In the steel heat treatment industry, nanofluid can be utilized as a quench medium. By controlling the amount of nanoparticle added in the nanofluid quench medium, the cooling rate can be adjusted. To preserve the heat transfer effectivity, the stability of the nanoparticle become very important. Hence, surfactant is quite essential to improve the particle stability and avoid particle agglomeration and sedimentation. In this study, a multiwalled carbon nanotube (MWCNT) was used as the nanoparticle in the distilled water. The concentration of the MWCNT was varied at 0.1, 0.3, and 0.5 % w/v. For the surfactant, Cetyl Trimethylammonium Bromide (CTAB) was chosen to disperse the particle better. In each of the three MWCNT variations, CTAB was added from 3 – 30% w/v. The maximum thermal conductivity obtained was in the nanofluid with 0.3% MWCNT and 5% CTAB at 0.72 W/mK. For the steel hardness, the value was roughly stable at 33 – 35 HRC in the nanofluid with no CTAB and 3 – 5% CTAB addition. Excessive surfactant addition at 30% CTAB decrease the hardness significantly up to 17 HRC.

Constructing Interconnected Hollow Mesopore Sn-Si Mixed Oxide Microspheres by Aerosol-Assisted Alkali Treatment with Enhanced Catalytic Performance in Baeyer-Villiger Oxidation

In this work, Sn-Si mixed oxide microspheres with concave hollow morphologies were first synthesized by a simple aerosol method using the very common commercial surfactant cetyl trimethyl ammonium bromide (CTAB) as a template, and then highly interconnected mesoporous and hollow Sn-Si mixed oxide microspheres were synthesized via an alkali (NaOH) treatment in the presence of CTAB. The results show that CTAB plays a crucial role not only in forming hollow morphologies during the aerosol process, but also protecting the amorphous framework and thus preventing the excessive loss of Sn species during the NaOH treatment. More importantly, it widens mesoporous distribution and forms interconnected mesoporous channels. The catalytic performance of Baeyer–Villiger oxidation on the interconnected mesoporous and hollow Sn-Si mixed oxide microspheres with 2-adamantanone and hydrogen peroxide was 9.4 times higher than that of the sample synthesized without the addition of CTAB; 2.3 times that of the untreated parent, which was due to the excellent diffusion properties derived from the hollow and interconnected mesopore structure. This method is mild, simple, low-cost, and can be continuously produced, which has the prospect of industrial application. Furthermore, the fundamentals of this study provide new insights for the rational design and preparation of highly interlinked mesoporous and hollow metal-oxides with unique catalytic performances.

High performance potentiometric hydrogen sensor based on ZnO porous cage sensing electrode

In this paper, ZnO porous cages were prepared by a facile one-pot encapsulation-calcination method and used as sensing electrodes for planar mixed-potential hydrogen sensors. As the amount of cetyltrimethylammonium bromide (CTAB) added during the preparation increased, the size of the individual ZnO cage decreased while the average pore size increased. The hydrogen sensing performance was enhanced with the increase of CTAB addition. At 0.35 wt% CTAB addition, the response value of the cages to 20 ppm hydrogen at 450 °C was −60.8 mV, which was 11.5 times higher than that of the conventional particles. A high response of −10.6 mV was obtained for 0.3 ppm hydrogen. Moreover, the response time to 500 ppm hydrogen was 26 s, which was 10.6 times shorter than that of the particles. Better selectivity and excellent repeatability were also achieved. Superior potentiometric hydrogen performance is mainly attributed to the highly porous sensing electrodes constructed from cages.

Performance and mechanism of CO2 reduction by DBD-coupled mesoporous SiO2

Abstract In the process of CO2 reduction with dielectric barrier discharge (DBD)-coupled catalysis, the existing material presents unsatisfactory synergy, such as high cost, complicated preparation processes, and low conversion rates. An inexpensive and environmentally friendly mesoporous SiO2 with different morphologies by gel–sol method was synthesized and then introduced for synergistic conversion of CO2 with DBD. The physicochemical properties of the synthesized mesoporous SiO2 materials were analyzed using X-ray diffraction, thermogravimetric analysis, scanning electron microscopy and Brunauer-Emmett-Teller method, indicated the prepared mesoporous materials manifested large specific surface areas, ordered pore channels and pore size, and good stability. The CO2 reduction performance, CO selectivity, and energy efficiency of DBD alone and DBD-coupled mesoporous SiO2 were investigated at different input powers. The SiO2 prepared with 1.05 g cetyltrimethylammonium bromide addition had the highest activity, in which the conversion of CO2, CO yield and energy efficiency were increased by 56.73, 68.41, and 122.31%, respectively, compared with DBD alone. The primary CO2 conversion mechanism of the mesoporous SiO2-coupled DBD was analyzed. It is shown that the suitable pore capacity structure, the large specific surface area, and the presence of filament discharge within the pore size of suitable mesoporous material can promote the decomposition of CO2 on its surface.

Effect of different pre-treatments on the redispersion capacity of spray-dried microfibrillated cellulose: Elaboration and characterization of biofilms

This study aimed to evaluate the influence of the addition of the cationic surfactant cetyltrimethylammonium bromide (CTAB) in microfibrillated cellulose (MFC/CNFs) suspensions submitted to different pretreatments to produce redispersible spray-dried (SD) MFC/CNFs. Suspensions pretreated with 5 % and 10 % sodium silicate and oxidized with 2,2,6,6,-tetramethylpiperidinyl-1-oxyl (TEMPO) were modified with CTAB surfactant and subsequently dried by SD. The SD-MFC/CNFs aggregates were redispersed by ultrasound to produce cellulosic films by the casting method. In summary, the results demonstrated that the addition of CTAB surfactant to the TEMPO-oxidized suspension was critical to achieving the most effective redispersion. The experimental results obtained using micrographs, optical (UV–Vis), mechanical, water vapor barrier properties, and the quality index confirmed that the addition of CTAB to the TEMPO-oxidized suspension favored the redispersion of spray-dried aggregates, development of cellulosic films with attractive properties, offering possibilities for the elaboration of new products, for example, in the production of bionanocomposites with higher mechanical performance. This research brings interesting insights into the redispersion and application of SD-MFC/CNFs aggregates, strengthening the commercialization of MFC/CNFs for industrial use.

Novel cetyltrimethylammonium bromide modified mixed adsorbent for efficient treatment of dyeing and printing wastewater

The treatment of dyeing and printing wastewater is a formidable challenge due to its high chemical oxygen demand (COD) and chromaticity, which pose severe threats to both the environment and human health. In this study, a composite modified adsorption material was prepared based on the applicability and feasibility in practical engineering applications. A novel mixed modified adsorbent was developed by incorporating activated carbon and activated clay as the foundation materials, followed by the addition of cetyltrimethylammonium bromide (CTAB) for modification. The performance of the composite adsorbent was evaluated via adsorption experiments of bromophenol blue (BPB) solution and dyeing and printing wastewater. The results demonstrated that the mixed modified adsorbent achieved a remarkable removal rate of 99% for BPB and 99.3% for chromaticity, under the optimal adsorption conditions. Furthermore, the regeneration performance of the mixed modified adsorbent was found to be exceptional. The adsorption process of BPB by the composite adsorbent was governed by the quasi-second-order kinetic model and Freundlich isotherm model, as evidenced by adsorption kinetics and isotherm analyses. The straightforward preparation method, coupled with the superior adsorption performance, underlines the promising potential of the proposed composite adsorbent for practical applications.

Highly porous biobased membranes via electrospinning of PBS and CTAB

The field of nanofiber research has been gradually shifting towards sustainable materials, but the main challenges include modifying their properties to fit specific needs and applications. In this study, ultrathin and porous biobased poly(butylene succinate) (PBS) membranes were fabricated using electrospinning. The neat PBS polymer was found to be very difficult to process, but defect-free nanofibers were generated by adding cetyltrimethylammonium bromide (CTAB) as a surfactant. To determine the effect of CTAB on PBS membranes, extensive characterization of the newly developed material was performed, including morphology, wettability, water absorption, thermal, mechanical, and hydrolytic degradation properties. Scanning electron microscopy (SEM) showed that adding 0.04% w/v of CTAB produced smooth and beadless nanofibers with an average diameter of 380 nm. The presence of CTAB, as a surfactant, significantly improved the membrane porosity and generated higher hydrophilicity even when starting with an intrinsically hydrophobic material (original PBS). The result was a higher water absorption and hydrolytic degradation of the membrane. On the mechanical side, the surfactant highly improved the elongation at break from 51% for the neat PBS membrane to 192% for the PBS/CTAB membrane with 0.04% w/v CTAB. However, CTAB addition had a negligible effect on thermal stability and crystallinity. The results of this study showed that the high porosity and hydrophilicity of PBS/CTAB electrospun membranes, combined with their outstanding water absorption capacity, elasticity, and biodegradability, present a novel solution for enhancing the performance and functionality of biomaterials in various biomedical fields, especially in tissue engineering and wound dressing applications.

Surfactant-Modified Construction Waste Bricks for the Removal of Diclofenac from Aqueous Solutions

This study aimed to enhance the efficiency of construction waste bricks (PRBPs) in removing diclofenac (DFC) by preparing surfactant-modified waste bricks (CCBPs) as adsorbents. The properties of the adsorbents were analyzed, and the parameters related to the adsorption process were examined. The findings demonstrate that the addition of cetyltrimethyl ammonium bromide (CTAB) significantly improved the ability of the waste bricks to adsorb DCF. The pH values affected the adsorption behavior, with the adsorption decreasing as the pH increased. The adsorption process followed the pseudo-first-order kinetic equation, and the rate of adsorption was fast. The Langmuir model was used to fit the adsorption isotherms. According to the adsorption thermodynamics, the adsorption of DCF onto both adsorbents was exothermic, and it was more favorable at lower temperatures. The adsorption capacity of the CCBPs decreased sharply as the KCl concentration increased. The mechanism of adsorption might be explained by the interplay of the π-π interaction, surface complexation, and electrostatic interaction. This study offers a new method for removing micropollutants from aqueous solutions using waste bricks, thus extending the scope of their reuse applications.

Synthesis of ordered mesoporous silica from biomass ash and its application in CO2 adsorption

It is possible to achieve high-value utilization of solid wastes and lower the cost of mesoporous silica synthesis by synthesizing mesoporous silica from solid wastes. In this study, silica was extracted using the alkali fusion method using biomass ash as the starting material. Biomass ash based mesoporous silica was successfully prepared by hydrothermal method with silicon extract solution as silicon source. The optimum conditions for preparation were determined as follows: addition of cetyltrimethylammonium bromide was 0.45g, hydrothermal temperature was 120 °C, hydrothermal time was 24h. The prepared mesoporous silicon was systematically characterized, and the results showed that high surface area (495 m2/g) and ordered pore structure appeared in the synthesized mesoporous silica materials. The synthesized mesoporous silica showed excellent CO2 adsorption performance (0.749 mmol/g) at 25 °C and 1 bar. According to the calculation of adsorption isotherm and thermodynamics, non-linear Freundlich model can fit the adsorption isotherm better and the adsorption heat of mesoporous silica is less than 20 kJ/mol, which belongs to physical adsorption. After five cycles of CO2 adsorption, the adsorption property was still above 90%, and the CO2/N2 adsorption selectivity reached 396.6, showing good regeneration performance and adsorption selectivity. This research can provide a new possibility for the high-value exploitation of biomass ash and reducing the cost of synthetic mesoporous silica.

Synthesis of Hierarchical ZSM‐11 Nanorods Aggregates and Catalytic Properties in Cyclohexene Hydration to Cyclohexanol

AbstractA series of hierarchical ZSM‐11 nanorods aggregates were prepared by a hydrothermal crystallization method with the addition of cetyltrimethylammonium bromide (CTAB). The physical and chemical properties of the samples were characterized and the catalytic properties in the direct hydration of cyclohexene to cyclohexanol were also investigated. The characterization results showed that adding CTAB effectively increased the crystallinity of the zeolite, and the external specific surface areas and pore volume of the zeolite increased dramatically. With the increase of CTAB addition, more and more mesopores were formed which could be clearly seen from TEM micrograph. The ratio of Brønsted/Lewis acid decreased first and then increased with the increase of CTAB addition, with the lowest point appeared at the ratio of CTAB/SiO2 of 0.015. The zeolite synthesized at the CTAB/SiO2 ratio of 0.015 exhibited the highest reaction rate with the cyclohexene conversion as high as 14.23 %. The excellent performance of the hierarchical ZSM‐11 nanorods aggregates can be attributed to the lowest Brønsted/Lewis acid ratio and large mesoporous volume.

Template-Assisted SnO2: Synthesis, Composition, and Photoelectrocatalytical Properties

A series of tin oxides were synthesized with polystyrene microspheres (250 nm) as the template. It was shown that an increase in the template content led to increasing specific pore volume and to the formation of bimodal pore structure with pores of 9 and 70 nm in diameter. Addition of cetyltrimethylammonium bromide (CTAB) during synthesis led to the formation of friable structures (SEM data), to an increase in the average pore diameter from 19 to 111 nm, and to the formation of macropores of 80–400 nm in size. All materials had similar surface properties and cassiterite structure with 5.9–10.8 nm coherent scattering region (XRD data). Flat-band potentials of the samples were determined and their photoelectrocatalytic properties to oxidation of water and methanol were studied in the potential range of 0.4–1.6 V RHE. It was shown that the sample obtained using CTAB was characterized by lower flat-band potential value, but appeared significantly higher photocurrent in methanol oxidation, which resulted from enhanced macro-meso-porous structure to facilitate methanol pore diffusion.

THE MESOPOROUS BIOSILICA CATALYST FROM ANDONG BAMBOO LEAF FOR DIRECT-PYROLYSIS REACTION

Silica is a functional material with broad benefits, including as a catalyst. It is essential to substitute synthetic silica with natural silica to support green technology and economic development. The silica extraction process from bamboo leaf waste was carried out using an acid-base solution and a cetyltrimethylammonium bromide (CTAB) template structure to get mesoporous biosilica. This mesoporous biosilica was then applied as a biocatalyst for α-cellulose direct pyrolysis. Biosilica was characterized using various analyses including Fourier Transform Infrared Spectroscopy (FTIR), Surface Area Analyzer (SAA), Scanning Electron Microscope (SEM), gravimetric methods, and applications to the cracking process using Pyrolysis Gas Chromatography Mass Spectrometry (Py-GCMS). The CTAB addition is divided into three variations, namely 0.05:1, 0.1:1, and 0.2:1. The data found that the highest yield was produced in the CTAB biosilica 0.2:1, and the silica content in the bamboo ash and CTAB biosilica sample was 60% and 90.5- 93.6%, respectively. The surface acidity of the biosilica ranged from 1.97 and 2.1 mmol/g. The essential groups in the biosilica formed are hydroxyl, silanol, and siloxane groups, with the morphology of the silica being observed to be irregular in shape, forming aggregates like coral. The surface area of biosilica with the ratio of 0.05:1, 0.1:1, and 0.2:1 was 177.068 m2 /g, 661.166 m2 /g, and 684.852 m2 /g, respectively, with a pore size distribution following the mesoporous class. The α-cellulose cracking using py-GCMS with a biosilica catalyst at CTAB variations of 0.05:1, 0.1:1, and 0.2:1 yielded a hydrocarbon content of 44.88%; 61.6%; and 30.4%.

Ultrafine metallic cobalt nanoparticle encapsulated in N‐doped carbon as high‐efficiency catalysts for reduction of 4‐nitrophenol

Novel and efficient ultrafine metallic cobalt nanoparticles encapsulated in N‐doped carbon catalysts are prepared via a facile method from pyrolysis of ZIF‐67‐x%CTAB, which is modified by CTAB (cetyltrimethyl ammonium bromide). The content of surfactant CTAB can control the crystal size of ZIF‐67, which further determines the Co particle size of Co@CN‐x%CTAB. The as‐prepared ZIF‐67‐x%CTAB and Co@CN‐x%CTAB were characterized by X‐ray powder diffraction (XRD), scanning electron microscopy (SEM), high‐resolution transmission electron microscopy (HRTEM), Brunauer−Emmett−Teller (BET), and X‐ray photoelectron spectroscopy (XPS). Co@CN‐0%CTAB could not maintain the primary morphologies of ZIF‐67‐0%CTAB with the collapse of skeleton. However, the Co@CN‐3%CTAB and Co@CN‐5%CTAB catalysts inherit the original morphologies with skeleton constriction. It indicated that Co@CN catalysts could maintain the skeleton structure of ZIF‐67 by adding CTAB during the preparation process. The particle size of Co@CN decreased with the increasing of CTAB content. Moreover, the addition of CTAB facilitated the formation of Co‐Nx species on catalyst surface. The kinetic rate constant of Co@CN‐5%CTAB catalyst was 0.99 min−1, which is 2.5 times as high as that of Co@CN‐0%CTAB catalyst for 4‐nitrophenol reduction. The excellent catalytic performance of Co@CN‐5%CTAB may be due to the presence of Co (0) species generated in situ during the calcination process, the smaller Co nanoparticles and more Co‐Nx site on the surface of the catalyst.

Piezo-, photo- and piezophotocatalytic activity of electrospun fibrous PVDF/CTAB membrane

A composite material based on polyvinylidene fluoride (PVDF) nanofibers modified with cetyltrimethylammonium bromide (CTAB) was synthesized by coaxial electrospinning. The morphology and structure of the material were studied by SEM, FTIR spectroscopy, X-ray diffraction analysis, XPS, and the piezo-photo- and piezo-photocatalytic activity during the decomposition of the organic dye Methylene blue (MB) was studied. It is shown that the addition of CTAB promotes additional polarization of the PVDF structure due to ion-dipole interaction. It has been shown for the first time that the addition of CTAB promotes the photosensitivity of the wide-gap dielectric polymer PVDF (the band gap is more than 6 eV). It was demonstrated that the photocatalytic decomposition efficiency was 91% in 60 minutes. The material exhibits piezocatalytic activity – 73% in 60 minutes. Experiments on trapping active oxidizing forms have established that OH hydroxyl radicals play the main role in the photocatalytic process.

Tunable morphology of strontium titanate nanocubes controlled by tert-butylamine-assisted solvothermal method and their enhanced electrical conductivity

The exploration of the size and shape of well-defined strontium titanate (SrTiO3) nanocubes remains challenging despite the increasing interest in this material, owing to its remarkable morphology-dependent electron and phonon transport abilities. This paper discusses the controllable solvothermal synthesis of SrTiO3 nanocube with tunable morphology in the ethanol-water solvent, using cetyltrimethylammonium bromide (CTAB) as a capping agent and tert-butylamine (TBA) as a mineralizer. The SrTiO3 nanocubes crystallization can be described as the dissolution-precipitation process, and the addition of CTAB and TBA affects the transformation of oriented attachment in forming a well-defined nanocube. In this study, the X-Ray Diffraction (XRD) data supported by the Le Bail refinement analysis revealed the shape-dependent tuning in lattice parameters of polycrystalline samples. The electrostatic interaction of CTAB and TBA on the particle surface of SrTiO3 was proven by the appearance of specific absorption peaks in the IR spectrum. XPS spectra show the chemical shift toward higher binding energy confirming the attraction of the nitrogen N-containing groups from CTAB and TBA with SrTiO3 through the synergistic capping effect. Meanwhile, HRTEM images showed that the nanocube particles have a uniform shape, sharp edges and vertices, flat faces, and narrow size distribution. In addition, the electrical conductivity in the bulk samples with uniform nanocubes increases three-fold compared to non-uniform nanocubes. These findings can potentially set a foundation for establishing synthesis techniques for producing morphologically-distinct particles based on surface interactions through the selective adsorption of additives.

Application of surfactant for improving leaching process of weathered crust elution-deposited rare earth ores

Weathered crust elution-deposited rare earth ores (WREOs) in China are the main source of medium and heavy rare earths in the world. In order to improve the seepage and the mass transfer of traditional ammonium salt leaching process of WREOs, surfactants were added in the ammonium sulfate leaching solution and the ammonium chloride leaching solution. The leaching kinetics, the mass transfer process, and the adhesion work reduction factor calculated from the interfacial properties were studied to reveal the strengthening mechanism of surfactant. In the presence of the tested five surfactants, cetyl trimethyl ammonium bromide (CTAB), dodecyl trimethyl ammonium bromide (DTAB), sodium dodecyl sulfate (SDS), sodium oleate and oleic acid, the permeability of WREOs is improved, the rare earth (RE) leaching efficiency increase and the impurity aluminum (Al) leaching efficiency decrease, indicating its promotional effect on the leaching process of WREOs. Furthermore, CTAB shows a better leaching enhancement, and the optimal addition dosage is 0.4 g/L for the two ammonium salt leaching agent systems. The kinetics analysis shows the internal diffusion controls model of RE and Al leaching process, and the leaching kinetics equations of RE and Al related to CTAB concentration were obtained for the two ammonium salt leaching systems. According to the chromatographic plate theory, the mass transfer efficiency of RE increases with the CTAB concentration increasing until 0.4 g/L, which confirms that the optimal CTAB addition is 0.4 g/L. Smaller adhesion work and adhesion work reduction factor indicate more favorable permeation as well as the leaching process.

Microscale and molecular regulation for molybdenum disulfide with extended layer spacing for high-performance sodium ion battery anodes

Molybdenum disulfide (MoS2) exhibits large layer spacing (0.62 nm) and considerable theoretical capacity (670 mAh g−1), which has been expected to be used as anode materials for sodium ion batteries (SIBs). However, MoS2 prepared by traditional hydrothermal method has the disadvantages of poor conductivity, easy agglomeration and uncontrollable morphology. Therefore, in this work two kinds of carbonaceous materials (carbon nanotubes and nitrogen doped carbon) are used to improve the electrochemical sodium storage ability of MoS2 at the molecular level and micron scale by one-pot hydrothermal method. Among them, carbon nanotubes contribute greatly to the conductivity and morphology of the composites at the micron scale, while cetyltrimethylammonium bromide (CTAB) derived nitrogen doped carbon is inserted into the interlayer of MoS2 crystal at the molecular level to realize the layer by layer protection of MoS2. Meanwhile, it is found that the CTAB addition amount of 1.5 mmol for the optimized experiment can provide the best electrochemical performance of the final modified MoS2 electrode materials. Experiments show that the synergistic dual-carbon MoS2 composite has uniform diameter of 1 μm flower ball morphology, excellent conductivity and improved cycle stability along with a high capacity of 350 mAh g−1 at 1A g−1 after 500 cycles, showing a high capacity retention rate of 89.4%. This work may develop a simple and effective way to synthesis high performance two-dimensional MoS2 composite anode for SIBs.