Contact Angle Research Articles

Multiscale simulation of water/oil displacement with dissolved CO[formula omitted]: Implications for geological carbon storage and CO[formula omitted]-enhanced oil recovery

This study combines molecular and pore-scale simulations to enhance our understanding of water, carbon dioxide (CO2), and oil flow in a porous system for high-efficiency geological carbon storage and enhanced oil recovery. We use molecular dynamics simulations to study the variation of interfacial tension (IFT), viscosity, and contact angle across varying system CO2 concentrations. The study reveals that the IFT simulation accuracy in the three-component mixture system relates positively to the volume-to-interfacial area ratio, and IFT decreases with CO2 concentration. Oil–CO2 mixture viscosity decreases and shows an intersection with water viscosity as CO2 concentration increases. The contact angle on the hydrophobic surface of kaolinite first increases and then decreases with CO2 concentration, while the hydrophilic surface contact angle is not sensitive to the CO2 concentration. Visualizing CO2 density distribution reveals its accumulation at fluid-fluid and fluid-solid interfaces and the combined effect results in the highest CO2 density at contact-line regions. Meanwhile, the elevated CO2 density at fluid-fluid interfaces reduces IFT, contributing to the initial contact angle increase, while the CO2 density increase at fluids-solid surface explains the subsequent contact angle decrease. These findings are then upscaled into a core-scale system using lattice Boltzmann simulations. The results are summarized into a phase diagram, which reveals the non-monotonic variations of the initial-residual (I-R) curves across different CO2 concentrations, and the residual saturation overall decreases with CO2 concentration for high initial saturations. These findings underscore the critical roles of system CO2 concentration and rock components, particularly kaolinite clay minerals, in subsurface multiphase seepage confronted in geological carbon storage and CO2-enhanced oil recovery, highlighting the importance of digital rock physical chemistry.

Hypothesizing the Oleic Acid-Mediated Enhanced and Sustained Transdermal Codelivery of Pregabalin and Diclofenac Adhesive Nanogel: A Proof of Concept.

Pregabalin (PG) and diclofenac diethylamine (DEE) are anti-inflammatory molecules that are effective in relieving inflammation and pain associated with musculoskeletal disorders, arthritis, and post-traumatic pain, among others. Intravenous and oral delivery of these two molecules has their limitations. However, the transdermal route is believed to be an alternate viable option for the delivery of therapeutic molecules with desired physicochemical properties. To this end, it is vital to understand the physicochemical properties of these drugs, dosage, and strategies to enhance permeation, thereby surmounting the associated constraints and concurrently attaining a sustained release of these therapeutic molecules when administered in combination. The present work hypothesizes the enhanced permeation and sustained release of pregabalin and diclofenac diethylamine across the skin, entrapped in the adhesive nano-organogel formulation, including permeation enhancers. The solubility studies of pregabalin and diclofenac diethylamine in combination were performed in different permeation enhancers. Oleic acid was optimized as the best permeation enhancer based on in vitro studies. Pluronic organogel containing pregabalin and diclofenac diethylamine with oleic acid was fabricated. Duro-Tak® (87-2196) was added to the organogel formulation as a pressure-sensitive adhesive to sustain the release profile of these two therapeutic molecules. The adhesive organogel was characterized for particle size, scanning electron microscopy, and contact angle measurement. The HPLC method developed for the quantification of the dual drug showed a retention time of 3.84 minutes and 9.69 minutes for pregabalin and diclofenac, respectively. The fabricated nanogel adhesive formulation showed the desired results with particle size and contact angle of 282 ± 57 nm and ≥120⁰, respectively. In vitro studies showed the percentage cumulative release of 24.90 ± 4.65% and 33.29 ± 4.81% for pregabalin and diclofenac, respectively. In order to accomplish transdermal permeation, the suggested hypothesis of fabricating PG and DEE nano-organogel in combination with permeation enhancers will be a viable drug delivery method. In comparison to a traditional gel formulation, oleic acid as a permeation enhancer increased the penetration of both PG and DEE from the organogel formulation. Notably, the studies showed that the use of pressure-sensitive adhesives enabled the sustained release of both PG and DEE.Therefore, the results anticipated the hypothesis that the transdermal delivery of adhesive PG and DEEbased nanogel across the human skin can be achieved to inhibit inflammation and pain.

Mechanism of action of the novel reagent dodecyl trimethyl ammonium chloride on magnesite and quartz surfaces

Silica impurities are one of the key factors that reduce the quality of magnesite. In this experiment, dodecyl trimethylammonium chloride (KDMP) was used as a quartz collector for silica-magnesium separation, and mineral flotation tests demonstrated that KDMP can effectively desiliconize and purify magnesite under the conditions of 20 mg/L and pH 5.0. Contact angle and Zeta potential measurements show that KDMP alters quartz’s characteristics more than magnesite. X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (FTIR) tests show that KDMP works on quartz and adsorbs solely on its surface, not on magnesite. Field Emission Scanning Electron Microscopy (FESEM) and Atomic Force Microscopy (AFM) images revealed that the KDMP collector adsorbed exclusively on the quartz surface, forming a layer of adsorption structure, but was weak on the magnesite surface. As a result, the KDMP collector is a highly intriguing flotation collector that can efficiently separate magnesite from quartz while also introducing a new form of collector for the separation and purification of low-grade magnesite.

Sea urchin-like Fe3O4 hollow microspheres/fatty amines composites phase change materials for highly efficient light-to-thermal conversion and heat storage

Pure phase change materials (PCMs) have limited photothermal conversion capabilities. To improve the photothermal conversion capability of PCMs, we developed composite phase change materials (FHS@PCMs) of sea urchin-like Fe3O4 hollow spheres (FHS) loaded with fatty amines (hexadecylamine (HDA) and octadecylamine (ODA)). The material composition and the surface nano-raised structure of FHS enable FHS@PCMs to exhibit excellent light absorption (up to 90 %, without any additional modification) and thermal conductivity. Moreover, the internal hollow spherical structure would prevent the leakage of PCM during the phase change process. Interestingly, FHS and FHS@PCMs exhibit inherent superhydrophobic properties with a water contact angle greater than 150°, thus endowing them with self-cleaning properties. FHS possesses strong magnetic properties that aid in material collection. Furthermore, the prepared FHS@PCMs exhibited exceptional thermal properties. The latent heat of FHS@HDA and FHS@ODA was 139.21 J∙g−1 and 140.13 J∙g−1, respectively. Additionally, FHS@PCMs maintained their excellent thermal properties even after 50 and 100 thermal cycles. Under one solar radiation, FHS@PCMs show a photothermal conversion efficiency of 89.63 % and 88.02 %, respectively. Taking of these advantages, the as-prepared composite phase change material may have significant potential in the fields of solar energy conversion and storage.

Modification and mechanistic study of fluid/fluid and carbonate rock/fluid interfaces using a glycolipid biosurfactant from an indigenous strain of Gordonia terrae for MEOR applications

To clarify the mechanism of the interface behavior between carbonate surface/biosurfactant solution/oil systems, the interfacial tension (IFT), surface wettability, spreading coefficient (SC), and capillary number were investigated with regard to the synergistic effects of a biosurfactant from an indigenous Gordonia terrae strain (isolated from an Iranian oil reservoir), formation water salinity, and pH using response surface methodology (RSM-CCD). According to the analysis of variance results, the process effectively depicted by the quadratic model demonstrated statistical significance in terms of the responses of IFT, wettability alteration, and SC, which were significantly affected by biosurfactant concentration. The optimal conditions were 0.260 g/L biosurfactant, 36.202 g/L salinity, and a pH of 5.9. Accordingly, the quadratic model was verified using the estimated optimal parameters, thereby confirming the accuracy of the model in which a strongly water-wet surface (contact angle change from 159° to 31°) and IFT reduction (from 23.96 to 1.26 mN/m) resulted in an SC of near-zero value (−0.18) and 25 % recovery of oil during the imbibition experiments after secondary water flooding. The desorption of the polar components of crude oil from the dolomite rock surface was also investigated through determining the un-coverage ratios of the elements using energy dispersive X-ray microanalysis and characterization. Although the solutions containing biosurfactants contributed to the alteration of the rock surface wettability, their performance strongly depended on the pH and salinity, resulting in different desorption ratios. The desorption of approximately 40 % of the adsorbed organic compounds from the carbonate surface was a critical limiting factor affecting the surface properties of the rock, and was responsible for altering the wettability to water-wet conditions. The results of this study are expected to contribute to the development of effective biosurfactant-flooding techniques for MEOR.

Insight into in situ enzymatic transesterification modification of polyethylene terephthalate fibers with polyethylene glycol

Polyethylene terephthalate (PET) fabric was enzymatically modified with polyethylene glycol (PEG). Lipase from Aspergillus oryzae was used as a catalyst. The wetting behavior of the modified PET fabric was characterized by the water contact angle, water adsorption dynamics and moisture regain. The initial water contact angle of the modified fabric decreased from 129.3° to 74.9°. The water absorption dynamics results indicated that the equilibrium water absorption amount of the modified fabric was approximately 10 times greater than that of the untreated sample. The initial absorption rate (Vinit) of the modified fabric was almost 30 times higher than that of the untreated fabric. The moisture regain reached 3.52% after modification. Scanning electron microscopy revealed granular and sheet coatings on the surface of the modified fabric. Chemical linkage of PEG onto the PET fibers was confirmed by attenuated total reflection–Fourier transform infrared spectroscopy. The modification had no significant effect on the thermal properties of the PET fabrics according to the thermogravimetric curve and differential scanning calorimetry results. The mechanical properties of the modified fabric were slightly improved. Therefore, in situ enzymatic transesterification between PET and PEG could be a potential novel modification approach for adding value to PET fiber textiles.

Deep insight into the effect of smithsonite particle size on surface heterogeneity and adsorption behavior: A case of fatty acid system

The studies for microfine mineral flotation have focused on the two main directions of increasing the apparent mineral particle size and reducing the bubble size, while little research has been reported on the special surface properties and adsorption mechanisms of mineral particles of different sizes. In this study, sodium oleate was chosen as a typical surfactant. The mechanism of the effect of smithsonite particle size on the heterogeneity and adsorption behavior of the mineral surface was explored in depth. Through microflotation experiments, BET area tests, Washburn contact angle tests, particle agglomeration tests, adsorption tests and inorganic carbon analysis, it was pointed out that the smaller the size of the particles, the greater the surface wettability, and the smaller the density and thickness of adsorbed oleate on the surface. The difficulty of encapsulating the mineral surface with a hydrophobic layer of oleate hydrocarbon chains, as well as suboptimal particle aggregation sizes, are key reasons for the poor flotation behavior of fine smithsonite. Furthermore, the inhomogeneity of active sites and charge distribution of surface components of smithsonite with different sizes was revealed from a microscopic point of view by DRIFT spectroscopic analysis, XPS analysis and zeta potential measurements. As the particle size of smithsonite decreases, the positive charge density on the surface is higher and the hydration tendency is more intense, hindering the adsorption of oleate. This work is expected to guide the full particle size recovery of minerals in the flotation from a novel microscopic point of view.

Impact of acid surface pretreatment on the hydrophobic agglomeration of micro-fine ilmenite and titanaugite in flotation

Acid surface pretreatment was employed to realize the selective hydrophobic agglomeration of micro-fine ilmenite in flotation. Microflotation and artificially mixed mineral experiments manifested that after acid surface pretreatment, the recovery of micro-fine ilmenite with the increase of NaOL concentration and the floatability difference of micro-fine ilmenite and titanaugite increased significantly. Zeta potential and contact angle analyses suggested that acid surface pretreatment intensified the adsorption of NaOL on ilmenite surfaces while reducing it on titanaugite surfaces. Turbidity, optical microscope, and EDLVO theory analyses attested that the hydrophobic attraction dominated in a short particle spacing in NaOL solution. Following acid surface pretreatment, the hydrophobic agglomeration between micro-fine ilmenite particles enhanced in NaOL solution due to increased hydrophobic attraction. In contrast, the hydrophobic attraction and agglomeration between micro-fine titanaugite particles as well as between micro-fine ilmenite and titanaugite particles weakened. Overall, acid surface pretreatment improved the selective adsorption of NaOL and the selective hydrophobic agglomeration of micro-fine ilmenite, resulting in enhanced separation efficiency and recovery of micro-fine ilmenite.

Preparation of highly stable immobilized Candida antarctica lipase B (CALB) through adjusting the surface properties of carrier: Preparation, characterization and performance evaluation

The stability of the immobilized lipase is the key factor that determines the economy and feasibility of its industrial application. Here, two robust immobilized Candida antarctica lipase B (CALB) were prepared through adjusting the surface properties of ECR1030 resin. Silane coupling agent (SCA) and dialdehyde cellulose (DAC) were employed to modify the carrier surface. Contact angle measurement showed that the hydrophobicity of the modified carrier increased first, and then decreased with the increase of the chain length of SCA. FTIR results showed that Si-O-Si bond and aldehyde group were attached to ECR1030, respectively, indicating that the ECR1030 resin was successfully modified. Meanwhile, the NH and CN bond were observed in the corresponding immobilized CALB, suggesting CALB was immobilized onto the modified carriers. The effects of immobilization conditions on CALB immobilization was further investigated, and the C8-ECR1030-CALB and DAC-ECR1030-CALB with the activity of 12,736 U/g and 11,962 U/g were obtained. Moreover, the stability of the immobilized lipases was evaluated and compared with the commercial Novozym 435. The C8-ECR1030-CALB and DAC-ECR1030-CALB exhibited comparable or superior stability to Novozym 435 and showed better deacidification effect than Novozym 435. This study paves road for further study involving preparation of highly stable immobilized lipase.

Solanum tuberosum leaf extract as an eco-friendly corrosion inhibitor for Q235-steel in HCl medium: experimental and theoretical evaluation

Solanum tuberosum leaf extract (STLs), used as a biodegradable corrosion inhibitor, was prepared to mitigate the corrosion rate of Q235 steel in HCl medium. The active inhibitory components existing in STLs were tracked by Fourier transform infrared spectroscopy. Electrochemical measurements, morphological characterization and contact angle tests were combined to evaluate the anti-corrosion performance of STLs at various concentrations and different temperatures, and the results show that the addition of STLs can evidently magnify the charge transfer resistance, expand the double layer capacitance at electric /solution interface, and simultaneously reduce the corrosion current density of Q235 steel in HCl medium with the maximum inhibition efficiency of 91.89%. The adsorption behavior of STLs on steel was investigated using X-ray photoelectron spectroscopy and adsorption models. It is revealed that the molecules of STLs spontaneously bind to the substrate through chemical and physical action, forming a protective layer to block the diffusion pathway of harsh ions. Furthermore, theoretical calculations confirm that Solanum tuberosum leaves components were adsorbed on steel substrates through donor-acceptor interactions.

Microstructure and friction properties of NiTi2-based composite layer prepared by ultrasonic assisted underwater wet laser deposition

An in situ TiC-enhanced NiTi2-based composite deposition layer was prepared by ultrasonic assisted underwater wet laser deposition. The evolution of the microstructure and interface state, and the friction properties in the air and brine solution environments of the deposition layer were analyzed and researched. The results demonstrated that the thermal and steady-state cavitation from ultrasound effects increase the total energy of the melt pool and promote mixing. The dilution rate of the ultrasonic assisted underwater laser deposition layer increases to 86.72 % compared with that of the underwater laser deposition layer (78.75 %). Ultrasonic reduced underwater laser deposition defects such as lack of fusion and weld slag, and enhanced the wettability between the deposition layer and substrate. The contact angle of the UWNT layer (24.40°, in average) is smaller than the WNT layer (29.80°, in average). Ultrasonic shortened the contact time between the deposition layer surface and the solution, which reduced the reaction of the Ni element with the brine solution. It also transformed the deposition layer from hypereutectoid microstructure to hypoeutectic microstructure and from planar interface to cellular interface. With the effect of the ultrasonic field, the elements in the deposition layer become more uniformly distributed and the secondary phases undergo spheroidization. In the ultrasonic assisted deposition layer, stress-induced FCC-Ti was discovered. Ultrasonic field also reduced the dispersion of the microhardness and increased the average microhardness to 863.3 ± 45.1 HV0.3. Tribology properties show that ultrasonic field effectively improved the wear resistance and friction stability of the ultrasonic assisted deposition layer. The COF of the ultrasonic assisted deposition layer was less affected by the environment, with values of 0.25 and 0.24 observed in air and brine solution, respectively. Overall, the research results in this paper can provide a new insight to improve the surface properties of NiTi2-based alloy underwater laser deposition.

Dynamic analysis of adsorbate behavior in nanopores: Liquid bridge formation, cavitation, and contact angle evaluation via molecular dynamics simulations

To explore the internal transport mechanisms and evolutionary processes within nanopore, molecular dynamic simulations were employed to explore the formation of liquid bridges and the evolution of menisci. The adsorption–desorption isotherms were obtained, and the dynamic behavior of the adsorbate was analyzed. Results revealed two distinct processes governing the behavior of the adsorbate within nanopore. At low pressure ratios, a molecular adsorption layer initially grows continuously on the pore surface. As the pressure ratio increases, an additional mechanism emerges, characterized by the formation of a liquid bridge near the nanopore mouth. This leads to pore filling as the liquid bridge expands and retreats towards the pore’s closed end. During desorption, cavitation occurs, which can be characterized as an activation process. Once initiated, cavitation intensifies, progressively increasing the number of cavities. The convergence of these cavities undermines the stability of the liquid bridge, ultimately resulting in its collapse and the rapid evaporation of the adsorbate molecules. Additionally, we further calculated the contact angle at the vapor–liquid interface using the Kelvin equation. The results indicated a deviation of less than 5 % compared to our simulations, suggesting that the Kelvin equation is applicable for materials with pore sizes of at least 3.6 nm.

Uncovering mechanism of excessive copper ion-activated depressed-sphalerite under moderate alkaline conditions: A combined experimental and DFT investigation

Currently, extensive research exists on the activation mechanisms of sphalerite, yet there is a notable absence of studies on the mechanisms behind the activation of depressed sphalerite. This paper investigates the mechanism through which moderate or excessive copper ions activate depressed sphalerite under conditions (pH 9–10) of moderate alkalinity, employing a comprehensive approach that includes pure mineral flotation experiments, contact angle measurements, FESEM-EDS, XPS, and density functional theory simulations.The results from pure mineral flotation experiments reveal that, at a copper ion concentration of 1 × 10−4 mol/L, sphalerite, previously depressed by zinc sulfate, is activated by copper ions, achieving a recovery rate of 91.46 % with butyl xanthate as the collector. However, when more cooper ions are added, the recovery of sphalerite decreases. Contact angle measurements and FESEM-EDS data indicate that under conditions of moderate alkalinity, zinc sulfate undergoes hydrolysis to form hydrophilic colloidal substances (hydroxylated zinc) that adhere to the surface of sphalerite, rendering it hydrophilic and thereby depressed. Following the introduction of copper ions, a dense striated material forms on the surface of sphalerite previously inhibited by zinc sulfate, enhancing its hydrophobicity, but if more copper ions were added, the hydrophobicity of activated sphalerite will be weakened. XPS findings further suggest that activated sphalerite by copper is capable of forming polysulfides, which then act on the sphalerite. DFT simulations verify that under moderate alkalinity conditions, copper ions first undergo a hydroxylation reaction in the solution before adsorbing or precipitating on the mineral surface as hydroxylated substances, which subsequently interact with sulfur on the surface of sphalerite. The analysis of the density of states indicates that following the addition of butyl xanthate, the strongest 3p orbital electron peak of the sulfur atom bound to butyl xanthate and the strongest 3d orbital electron peak of zinc are at distinct energy levels, suggesting that the overlap of the electronic density of states is minimal, indicating a weak and unstable interaction between the sulfur and zinc atoms bonded with butyl xanthate. Conversely, the strongest 3p orbital electron peak of the sulfur atom bonded with butyl xanthate overlaps with the strongest 3d orbital electron peak of copper and is positioned near the Fermi level, signifying a strong reactivity and more stable interaction between the sulfur and copper atoms.

Investigation of the effect and mechanism on the flotation performance of alkylglycine-based collectors by acyl group

The structure difference of the flotation reagent has a significant influence on its flotation performance. In this work, sodium N-lauroyl glycinate (SNG) was synthesized by introducing an acyl group into sodium N-dodecylglycinate (SN), and was using the collector in the oxide ores flotation. Properties of these two collectors were compared, and the effects behavior and mechanism of introducing the acyl group on the flotation performance of alkylglycine-based collectors to the zinc oxide minerals were systematically investigated. Flotation results proved that the introduction of C = O group into SN barely affected the floatability of smithsonite, hemimorphite and calcite, while the floatability of quartz was greatly reduced. Contact angle tests, surface tension tests, and froth collapse measurements indicated that the introduction of the acyl group into SN could selectively weaken its ability to improve the hydrophobicity of mineral surfaces, reduce its surface tension, adsorption capacity and intensity on the mineral surface, and the froth stability, thereby enhancing its selectivity, consistent with the flotation results. Fourier transform infrared spectroscopy (FTIR) analyses and density functional theory (DFT) calculations revealed that the introduction of the acyl group could increase the cross-sectional area and reduce the charge of the SNG polar groups to selectively weaken the adsorption interaction, particularly by significantly reducing the electrostatic adsorption between SNS and quartz surfaces. These also confirm that SNG is a promising highly selective collector for the flotation separation of zinc oxide minerals.

A “performance-inheritance” strategy for achieving hydrophilic/hydrophobic fluorescent biomass-derived carbon dots through simple solvothermal treatments

It remains a challenge to obtain hydrophilic/hydrophobic materials with promising biocompatibility and environmental compatibility by simple methods. Herein, we designed a “performance-inheritance” strategy and for the first time constructed hydrophilic/hydrophobic fluorescent spirulina-derived carbon dots (CDs) through simple solvothermal treatments. The contact angle of hydrophobic CDs with near-infrared (NIR) fluorescence is 110°, while hydrophilic CDs with blue fluorescence is 19°. We further revealed that the NIR luminescence is derived from the chlorophyll structure, while blue fluorescence is from the surface states. Based on the hydrophilicity/hydrophobicity of CDs, a ratiometric sensor was constructed to detect water content in organic solutions. In addition, CDs with NIR emission have low toxicity and good biocompatibility, making them efficient probes for bioimaging. This strategy provides a simple method for the high value-added conversion of algae and a new perspective for the “design-preparation-application” of biomass-derived CDs with specific properties.

A high-strength, environmental-friendly, and multifunctional soy protein adhesive inspired by biomineralization

Soy protein is an economical and eco-friendly adhesive material that offers significant potential for the development of bio-based adhesives. However, they have poor water resistance, low bonding strength, mold-susceptibility, and deterioration, which are serious challenges to the widespread application of soy protein adhesives in plywood. This work was inspired by the biomineralization phenomenon and the preparation of a novel soy protein adhesive (SPI-RGT-AgNPs). The SPI-RGT-AgNPs adhesive exhibited excellent viscosity, residual rate, and moisture absorption performance compared with the original soy protein isolate (SPI) adhesive, with an increase from 37° (SPI) to 81° (SPI-10RGT-10AgNPs) in water contact angle testing. The dry and wet adhesion strengths reached 2.49MPa and 1.43MPa, 193% and 117% higher than SPI adhesive, respectively. Molecular docking simulations were used to verify that the introduction of modifiers significantly improved the stability and crosslinking strength of the adhesive. The best ratio of the SPI-RGT-AgNP adhesive was confirmed using the response surface methodology (RSM). Simultaneously, SPI-RGT-AgNPs adhesive also showed excellent anti-mildew and anti-microbial efficiencies to Escherichia coli (98.18%) and Staphylococcus aureus (99.33%). In addition, a life-cycle assessment was used to explore the pollution emissions from the adhesives. As compared to formaldehyde-based adhesives, the SPI-RGT-AgNP adhesive had lower energy consumption and pollution emissions. Therefore, this study prepared a novel high-strength and multifunctional soy protein adhesive, guiding the production of multifunctional and green adhesives.

Influence of Nanopesticide Surface Chemistry on Adsorption to Plant Cuticle and Wax Layer: The Role of Zeta Potential and Wetting

Nanopesticidal adsorption on plant surfaces is a critical determinant of their application efficacy, persistence, and ecological impact. In this study, we systematically investigate the impact of surface chemistry on the attachment of nanopesticides for seven different nanocarriers: ethyl lauroyl arginate (ELA, cationic), cocamidopropyl betaine (CAPB, zwitterionic), tween 80 (TW80, nonionic), β-cyclodextrin (βCD), sodium dodecyl sulfate (SDS, anionic), whey protein isolate (WPI), and poloxamer 407 (PXL, nonionic). Azadirachtin from neem seed extract was employed as a model pesticide active ingredient. The nanopesticides were characterized using dynamic light scattering, UV-visible spectroscopy, static contact angle (SCA, θ), and zeta (ζ) potential measurements. Pepper leaves (ζ = −11.6 mV) and candelilla wax (ζ = −2.6 mV) films were utilized to analyze the effect of nanocarrier chemical composition on nanopesticide adsorption. Fluorescence microscopy was utilized to quantify the adsorption of nanopesticides (with fluorophore tagging) on the substrates. It was found that the choice of nanocarrier significantly influenced the adsorption behavior. Nanopesticides with ELA corona, which was cationic with a zeta potential of ∼+19 mV and θ of ∼ 61°, exhibited the highest affinity towards the leaf cuticle and wax substrates, attributed to favorable electrostatic interactions forces. Conversely, nanopesticides with SDS (ζ = −48 mV; θ = 45°), WPI (ζ = −24 mV; θ = 54°), and PXL (ζ = −31 mV; θ = 64°) corona demonstrated the least adsorption. These findings indicate a weak correlation between the wetting behavior of nanopesticide suspensions and nanopesticide adsorption on plant and wax surfaces, as well as a strong correlation between nanopesticide zeta potential and nanopesticide adsorption. These findings heuristically recommend that aqueous cationic and zwitterionic nanocarriers for pesticides provide superior adsorption characteristics on pepper leaves and candelilla wax surfaces. Aqueous macromolecular carriers such as PXL and WPI have performed less effectively in adherence compared to shorter chain amphiphiles with similar zeta potential and wetting characteristics, indicating that the steric and osmotic chain effects of hydrophilic macromolecules hinder the adsorption relative to shorter chains.

Application of calcium hypochlorite and carboxymethyl chitosan as combined depressants for selective flotation separation of chalcopyrite from pyrite at low alkalinity

Flotation separation of copper-sulfur at low alkalinity has attracted soaring interest in the beneficiation of copper sulfide ore. In this work, application of calcium hypochlorite (Ca(ClO)2) and carboxymethyl chitosan (OCMC) as combined depressants for selective flotation separation of chalcopyrite from pyrite was investigated. A maximum recovery difference of 71.35 % between both minerals is observed under the recommended conditions ([Ca(ClO)2] = 60 mg/L, [OCMC] = 400 mg/L and 40 mg/L SBX at pH=8). Besides, the copper-sulfur flotation separation indexes were assessed by the artificial mixed-mineral tests. Results of contact angle measurement, zeta potential and adsorption amount analysis reveal that the combined depressants severely impede the collector adsorption onto pyrite surfaces, and has a light effect on the chalcopyrite. OCMC exhibits a stronger complexing ability on Ca2+ and Fe2+ ions than Cu2+ ions. XPS results confirm that the combined depressant interact with pyrite surfaces intensively, and prompt a deep conversion of S22- and Sn2-/S0 into S2- and SO42- species, as well as a deep transformation of Fe(II)-S into Fe(III)-O/OH on the pyrite surface. ToF-SIMS and thermodynamic calculation results afford the favorable evidence for the selective suppression of the pyrite with added the combined depressant. Thereby the selective oxidation and intense complexation on the pyrite stemming from the combined depressant synergy are responsible for the selective separation of chalcopyrite from pyrite.

Superhydrophobic poly(lactic acid) membrane prepared with the induction of modified carbon dots for efficient separation of water-in-oil emulsions

Superhydrophobic separation membranes are considered to be one of the most promising technologies for oil-water separation. However, the plastic waste generated from discarded membranes poses a challenge to the preparation of degraded superhydrophobic separation membranes for achieving eco-friendly separation. In this study, superhydrophobic poly(lactic acid) (PLA) membranes were fabricated using a non-solvent induced phase separation method assisted by l-cysteine modified carbon dots (Cys-CDs). The synergistic effect of Cys-CDs-induced crystallization behavior of PLA and the phase separation process results in the evolution of the surface of the PLA-based membrane from a pistil-like structure to a multi-level micro-nano structure composed of dense lamellar nanofibers and microspheres with an increase in Cys-CDs content. At a Cys-CDs content of 5 wt%, the surface roughness of PLA-based separation membrane reached its maximum, and the water contact angle was as high as 159°. Remarkably, the superhydrophobic Cys-CDs/PLA membrane exhibited promising performance in the separation of water-in-oil emulsions, with a rejection rate of 99.98 % and a flux of 315.74 L·m−2·h−1·bar−1. Additionally, the superhydrophobic Cys-CDs/PLA separation membrane also demonstrates impressive properties such as acid-alkali resistance and rapid recycling into high-value chemicals. Consequently, this rapidly recoverable superhydrophobic porous Cys-CDs/PLA membrane shows great potential for practical applications in actual oil-water separation.

Rigid polyurethane foam with durable hydrophobicity and flame retardancy endowed by novel functional surfactants

Traditional rigid polyurethane foam (RPUF) with flame retardancy might be easily damaged in some moist condition due to its hydrophobicity, which would lead to unsafety. Therefore, novel surfactants with both hydrophobic fluorinated group and flame-retardant phosphorus group were synthesized. With lower surface tension and more hydrogen bonds formed in polyurethane, the mixed surfactants, which were used in the preparation of RPUF, have not only obviously improved the size uniformity and integrity of cells but also enhanced its hydrophobicity, compressive strength and thermal insulating performance. Besides, effective ‘protection’ could be constructed on the surface of RPUF by prepared surfactants, when ammonium polyphosphate (APP) and expandable graphite (EG) were introduced to provide good flame retardancy. As a result, with just 2.8wt% content of those functional surfactants, hydrophobic and flame-retardant RPUF with water contact angle of 126 °, limiting oxygen index of 25%, compressive strength of 1.3MPa and thermal conductivity of 27mW/mK, were finally obtained, which is ahead of other flame-retardant RPUF reported before. It’s worth noting that, this hydrophobic and flame-retardant RPUF exhibits more stable and durable properties when soaking in HCl solution (2mol/L), NaOH solution (2mol/L), NaCl saturated solution and various solvents (THF and EtOH), or under strong fiction for 100 times and high and low temperature cycling test for 20 times. This would provide a novel and effective strategy to endow RPUF with enhanced and durable flame retardancy, hydrophobicity, compressive strength and thermal insulating performance even under extreme conditions.