Glycerol Water Research Articles

Production of Biodegradable Plastic from Biomass

Plastic pollution is one of the most dangerous environmental problems that threaten the world. Conventional plastic doesn’t degrade and tends to end up in seas and land, killing sea animals and polluting soils. Plastics obtained from agricultural wastes and have the ability to degrade, have appeared as possible solution to the conventional plastic problems. However, in order for the biodegradable plastic to substitute the conventional plastic, it must possess similar characteristics in addition to being economically and environmentally attractive. The aim of this paper is to produce durable and degradable plastic from potato peels. The effect of different operating conditions on the characteristics of the produced plastic, including biodegradation behavior, tensile strength and water absorption behavior, were studied. Acetic Acid with amounts of 4, 6 and 8 ml were used proving that the 8 ml acid concentration is the best from biodegradation point of view. Moreover, glycerol of amounts 2,4,6 ml were used, indicating a direct relation between degradation and glycerol amount, as well as, an inverse relation between water absorption and glycerol amount. Reaction temperature as well as drying temperatures were also tested showing that the low temperatures have good effect on enhancing the properties of the produced plastic.

Experimental study on effect of surfactant and solution property on bubble rising motion

Bubbly flows are frequently run into in industrial processes. Since liquid phases usually contain impurities, bubble interface is polluted to a certain degree. This can affect flow structures, and heat and mass transfer properties at bubble interface, leading to a significant effect on industrial efficiencies. Therefore, it is important to study the hydrodynamic characteristics of polluted bubbles. It was experimentally investigated on the effects of surfactant concentration, ionization and solvent polarity on bubble shape, rise trajectory and velocity using a high–speed camera in this paper. The present studies show that the addition of a very small amount of non–ionic surfactants (1–OA) into a polar solution (a 56% glycerol–water solution) can cause a great change in bubble rise trajectory (an inhibition of about 80% in bubble lateral migration) and a decrease in bubble rise velocity (a decrease of about 25% in bubble maximum velocity) because surfactant molecules adsorbed at bubble interface gather tightly. However, the addition of ionic surfactant (SDS) with the same concentration into a polar solution cannot cause a significant change in bubble rise trajectory and rise velocity because the distribution of surfactant molecules adsorbed at bubble interface is relatively loose due to an electrostatic effect. The addition of surfactants into a non–polar solution (Dimethyl silicone oil) cannot obviously change the above parameters due to the non–solvent effect of surfactants in non–polar solutions. Namely, surfactant molecules cannot be adsorbed at bubble interface.

1H-NMR Karplus Analysis of Molecular Conformations of Glycerol under Different Solvent Conditions: A Consistent Rotational Isomerism in the Backbone Governed by Glycerol/Water Interactions.

Glycerol is a symmetrical, small biomolecule with high flexibility in molecular conformations. Using a 1H-NMR spectroscopic Karplus analysis in our way, we analyzed a rotational isomerism in the glycero backbone which generates three kinds of staggered conformers, namely gt (gauche-trans), gg (gauche-gauche), and tg (trans-gauche), at each of sn-1,2 and sn-2,3 positions. The Karplus analysis has disclosed that the three rotamers are consistently equilibrated in water keeping the relation of 'gt:gg:tg = 50:30:20 (%)' at a wide range of concentrations (5 mM~540 mM). The observed relation means that glycerol in water favors those symmetric conformers placing 1,2,3-triol groups in a gauche/gauche geometry. We have found also that the rotational isomerism is remarkably changed when the solvent is replaced with DMSO-d6 or dimethylformamide (DMF-d7). In these solvents, glycerol gives a relation of 'gt:gg:tg = 40:30:30 (%)', which means that a remarkable shift occurs in the equilibrium between gt and tg conformers. By this shift, glycerol turns to also take non-symmetric conformers orienting one of the two vicinal diols in an antiperiplanar geometry.

Zinc Vanadate (Zn3V2O8) Immobilized Multiwall Carbon Nanotube (MWCNT) Heterojunction as an Efficient Photocatalyst for Visible Light Driven Hydrogen Production.

Z-scheme photocatalytic reaction is considered an effective strategy to promote the photogenerated electron-hole separation for significantly improving the efficiency of photocatalytic hydrogen precipitation from splitting water. In this study, a heterojunction nanocomposite material based on Zn3V2O8 (ZV) with MWCNT was prepared by a hydrothermal process. The photocatalysts were characterized by X-ray diffraction, scanning electron microscopy (SEM), Fourier transform infrared (FTIR), UV-visible absorption spectroscopy, and transmission electron microscopy (TEM) to understand crystal structure, morphology, and optical properties. The efficiency of the samples was evaluated for the photocatalytic H2 production under visible solar radiation using water glycerol as a sacrificial reagent. The obtained results suggest that, between ZV and ZV@MWCNT, the latter shows higher efficiency for H2 production. The maximum H2 production efficiency was found to be 26.87 μmol g-1 h-1 for ZV and 99.55 μmol g-1 h-1 for ZV@MWCNT. The synergistic effect of MWCNT to ZV resulted in improving the efficiency of charges and light-absorbing capacity, resulting in enhanced H2 production in the heterojunction nanocomposite material. The nanocomposite was stable and highly efficient for H2 production of six or more cycles. Based on the outcomes of this study, it can be observed that forming the heterojunction of individual nano systems could result in more efficient material for H2 production under visible solar energy.

ZnO/Fe-thioporphyrazine composites as efficient photocatalysts for oxidation of glycerol to value-added C3 products in water

Photocatalytic selective oxidation of glycerol to value-added C3 products is a promising strategy for the valorization of glycerol. In this work, an inorganic/organic composite material by integrating zinc oxide (ZnO) with iron thioporphyrazine (FePz) was prepared to act as photocatalyst for photocatalytic oxidation of glycerol in water. The effects of FePz surface modification on the physicochemical properties and photocatalytic performance of ZnO were systemically studied. More importantly, the integration of ZnO with FePz could markedly improve the visible light absorption ability and effectively promote the separation of photogenerated charges. Meanwhile, introducing FePz onto the ZnO surface was beneficial to the adsorption capacity of glycerol. Just because of this, ZnO/FePz composite exhibited excellent photocatalytic activity for oxidizing glycerol in water, C3 products including glyceraldehyde and dihydroxyacetone were obtained from this composite photocatalytic system. Additionally, the active species responsible for glycerol oxidation were also determined.

Differential Sensing with Replicated Plasmonic Gratings Interrogated in the Optical Switch Configuration.

A new plasmonic configuration is proposed for application in a sensor and demonstrated for the detection of variations in the bulk refractive index of solutions. The configuration consists of monitoring two diffracted orders resulting from the interaction of a TM-polarized optical beam incident on a grating coupler, operating based on an effect termed the "optical switch". The two monitored diffracted orders enable differential measurements which cancel the drift and perturbations common to both, leading to an improved detection limit, as demonstrated experimentally. The measured switch pattern associated with the grating coupler is in good agreement with theory. Bulk sensing is demonstrated under intensity interrogation via the sequential injection of solutions comprised of glycerol in water into a fluidic cell. A limit of detection of about 10-6 RIU was achieved. The optical switch configuration is easy to implement and is cost-effective, yielding a highly promising approach for the sensing and the real-time detection of biological species.

Studies on spray dried topical ophthalmic emulsions containing cyclosporin A (0.05% w/w): systematic optimization, in vitro preclinical toxicity and in vivo assessments.

Cyclosporin A (CsA, 0.05% w/w)-loaded positively charged emulsions were prepared based on castor oil, chitosan, poloxamer 188, glycerin and double-distilled water. To augment the shelf/storage-stability of original emulsions, the solid-dry powder for reconstitution was made by spray drying technique. The screening (Taguchi OA) and optimization (face-centered central composite) designs produced the optimized conditions for spray drying: 40 Nm3/h aspirator flow rate, 15ml/min feed rate, 115°C inlet temperature, 10% mannitol and 1.25% trehalose. The % drug entrapment efficiency values of original and reconstituted emulsions ranged from 73.20 ± 0.13 to 71.55 ± 1.25%. At 20min post-dissolution, two times higher CsA release was seen from reconstituted emulsions than the original emulsions (85.78 ± 1.14 vs. 42.25 ± 1.84%) in simulated tear fluid. Using MTT assay, the reconstituted emulsions with or without CsA produced 94.512 ± 2.12 to 99.941 ± 1.89% cell viability values in HCE-2 cells. No appreciable change in capillary integrity was visualized in HET CAM following reconstituted emulsions treatment. At equivalent 15µg drug, the in vitro protein denaturation assay showed augmented inhibition value (~ 85%) for tested CsA emulsions compared to diclofenac reference (68.30 ± 2.05) indicating enhanced anti-inflammatory activity. The CsA concentrations in multiple ocular matrices of rabbit eyes determined by the UPLC-MS/MS method attained the therapeutic drug level of 50-300ng/ml even at 90min post-topical instillation of both emulsions. Overall, the CsA emulsion eyedrops can be supplied as a spray dried storable intermediate product for reconstitution.

Physical crosslinked hydrogel-derived smart windows: anti-freezing and fast thermal responsive performance.

Thermochromic hydrogels are versatile smart materials that have many applications, including in smart windows, sensing, camouflage, etc. The previous reports of hydrogel smart windows have been based on covalent crosslinking, requiring multistep processing, and complicated preparation. Moreover, most research studies focused on enhancing the luminous transmittance (Tlum) and modulating ability (ΔTsol), while the structural integrity and antifreezing ability, which are essential in practical applications, have been compromised and rarely investigated. Herein, we develop a new physical (noncovalent crosslinked) hydrogel-derived smart window by introducing an in situ free radical polymerization (FRP) of N-isopropylacrylamide (NIPAM) in a glycerol-water (GW) binary solvent system. The noncovalent crosslinked PNIPAM GW solutions are facilely synthesized, giving outstanding freezing tolerance (∼-18 °C), a comparably high Tlum of 90%, and ΔTsol of 60.8%, together with added advantages of fast response time (∼10 s) and good structural integrity before and after phase transition. This work could provide a new strategy to design and fabricate heat stimulated smart hydrogels not limited to energy saving smart windows.

Survey of Hand Issues Encountered by Hairdressers and Hairdresser Related Professionals: From Epidemiological Data to Clinical Observational Survey Results

Hand eczema is frequent among hairdressers. The aim of this open survey was (i) to assess the prevalence and identify causing factors of hand issues encountered by hairdressers and (ii) to assess the benefit of a cosmetic skin care in clinical signs and symptoms through a clinical observational survey. The survey was conducted among 391hairdressers and hairdresser-related professionals, collecting information on frequency of daily procedures, frequency/type/severity of hand issues, and glove usage. The satisfaction provided by a dermocosmetic containing niacinamide, glycerin, shea butter and thermal spring water was examined in an evaluation visit one month after survey initiation. Investigated subjects were mostly hairdressers (73%). In their daily procedures, a majority (≥76%) always or often used shampoos, hair dyes, oxidants, bleachers, straighteners and perms. Overall, a majority (>60%) of subjects always or often had hand irritation due to this use (except for straighteners). Most subjects (≥60%) reported using gloves in their procedures except with shampoos and straighteners. Among hand problems reported at survey initiation, the most intense was skin dryness, followed by redness, irritation, cracks, and fissures. Hand problems induced annoyance in their activities for most subjects (>65%), leading to discontinuation of their professional activities for 28% subjects. The test dermocosmetic was applied for 1week up to 1month. At evaluation visit (1month), the intensity of all hand signs and symptoms was decreased compared to initiation visit. In addition, 58.3% subjects reported return to professional activities instantly at evaluation visit versus 31.3% at initial visit. Most subjects (≥73%) were satisfied or very satisfied with the test cream properties. Our survey confirms the impact of hand issues experienced by hairdresser professionals and highlights the need for gloves and for efficient hand care products.

Sustainable Use of Traditional Plant Extracts for the Formulation of Herbal Shampoos

Skin and hair care products described with natural bioactive compounds have been considered as a better alternative to synthetic ones. Therefore, this study aimed to develop a natural shampoo using traditional plant extracts. With an emphasis on safety and efficacy, its physicochemical properties were evaluated and compared with the marketed shampoo. Each plant material was ground and extracted using 70% hydro-alcoholic solvent for 5-7 days. Shampoo formulation was prepared using sprouted fenugreek seeds extract and pea fruit extract as key ingredient along with other natural ingredients including: reetha, amla, marigold, orange peel, castor oil, glycerine and distilled water. The physicochemical parameters and antioxidant activity of both formulations were ascertained to ensure the safety and efficacy of the designed formulation. According to the present study, the developed shampoo (F1 & F2) was yellowish green and brown in color, had a good odor and optimum pH value of 5.32–5.96. The viscosity of F1 and F2 was found to be 2.3 to 2.08 poise; both formulations reduced the surface tension to 49.08 and 50.7dynes/cm respectively. While the solid content of F1 & F2 shampoos was found to be 20.57 and -21.87%. The developed shampoo (F1 & F2) exhibited significant antioxidant activity with IC 50 values of 53.46 (F1) & 69.4 µ/ml (F2), respectively. The findings of this study demonstrated that shampoo formulations were found to have functionality comparable to physicochemical features of marketed shampoo. However, further studies are necessary to validate the performance and quality of the shampoo. Keywords: herbal shampoo, shampoo formulation, traditional plant extracts. https://doi.org/10.55463/issn.1674-2974.50.4.14

Dual functional WO3/BiVO4 heterostructures for efficient photoelectrochemical water splitting and glycerol degradation.

Dual functional heterojunctions of tungsten oxide and bismuth vanadate (WO3/BiVO4) photoanodes are developed and their applications in photoelectrochemical (PEC) water splitting and mineralization of glycerol are demonstrated. The thin-film WO3/BiVO4 photoelectrode was fabricated by a facile hydrothermal method. The morphology, chemical composition, crystalline structure, chemical state, and optical absorption properties of the WO3/BiVO4 photoelectrodes were characterized systematically. The WO3/BiVO4 photoelectrode exhibits a good distribution of elements and a well-crystalline monoclinic WO3 and monoclinic scheelite BiVO4. The light-absorption spectrum of the WO3/BiVO4 photoelectrodes reveals a broad absorption band in the visible light region with a maximum absorption of around 520 nm. The dual functional WO3/BiVO4 photoelectrodes achieved a high photocurrent density of 6.85 mA cm-2, which is 2.8 times higher than that of the pristine WO3 photoelectrode in the presence of a mixture of 0.5 M Na2SO4 and 0.5 M glycerol electrolyte under AM 1.5 G (100 mW cm-2) illumination. The superior PEC performance of the WO3/BiVO4 photoelectrode was attributed to the synergistic effects of the superior crystal structure, light absorption, and efficient charge separation. Simultaneously, glycerol plays an essential role in increasing the efficiency of hydrogen production by suppressing charge recombination in the water redox reaction. Moreover, the WO3/BiVO4 photoelectrode shows the total organic carbon (TOC) removal efficiency of glycerol at about 82% at 120 min. Notably, the WO3/BiVO4 photoelectrode can be a promising photoelectrode for simultaneous hydrogen production and mineralization of glycerol with a simple, economical, and environmentally friendly approach.

Development of boring solutions produced from using compositions of clay minerals and surface-active substances from raw fatty acids of cotton soap stock

The article studies the physical and chemical properties of water glycerin to obtain various types of surface-active substances for use as additives to boring solutions. The addition of technical glycerin to the composition of surface-active substances obtained from raw fatty acids of cotton soap stock at oil and fat enterprises contributes to a significant improvement in their surface-active properties. A water solution of glycerin to a certain extent increases the surface-active properties of the developed soap-like surface-active substances. The qualitative indicators of the composition of surfactants obtained with different ratios of a water solution of glycerol of liquid and ointment fractions of raw fatty acids of cotton soap stock were studied for their use in the process of drilling oil and gas wells. Analyzes of the developed compositions of were carried out in the preparation of drilling fluids from alkaline bentonite, alkaline earth bentonite and carbonate palygorskite, as well as double and triple compositions. A comparative analysis of the main indicators of drilling fluids, as well as surface-active substances synthesized from the greasy fraction of raw fatty acids of cotton soap stock, showed the greatest stability of boring solutions at high temperatures and salinity of formation waters.

Micromixing Intensification within a Combination of T-Type Micromixer and Micropacked Bed.

The combination of microstructural units is an effective strategy to improve the micromixing of liquid phase systems, especially viscous systems. However, how the microstructural combination influences micromixing is still not systematically investigated. In this work, the Villermaux/Dushman reaction is used to study the micromixing performance of the viscous system of the glycerol-water in the combination of a T-type micromixer and a micropacked bed. Micromixing performances under various structural parameters and fluid characteristics are determined and summarized, and the micromixing laws are revealed by dimensionless analysis considering the specific spatial characteristics and temporal sequence in the combined microstructures. It achieves good agreement with experimental results and enables guidance for the design and scaling-up of the combined T-type micromixer and micropacked bed towards micromixing intensification in viscous reaction systems.

Chestnut-Tannin-Crosslinked, Antibacterial, Antifreezing, Conductive Organohydrogel as a Strain Sensor for Motion Monitoring, Flexible Keyboards, and Velocity Monitoring

Flexible sensing devices (FSDs) fabricated using conductive hydrogels have attracted researchers' extensive enthusiasm in recent years due to their versatility. Considering the complexity of their application environments, the integration of various functional characteristics (e.g., excellent mechanical, antibacterial, and antifreezing properties) is an important guarantee for FSDs to stably perform their applications in different environments. Herein, we developed a multifunctional conductive polyvinyl alcohol (PVA) organohydrogel PVA-CT-Ag-Al-Gly (PCAAG) by using a green, natural, and cheap biomass, chestnut tannin (CT), as a crosslinking agent, nano-silver particles (AgNPs) as an antimicrobial agent, aluminum trichloride (AlCl3) as a conducting medium, and the mixed water-glycerol as the solvent system. In this organohydrogel system, CT acted not only as the reducing and stabilizing agent for the preparation of antibacterial AgNPs but also as the crosslinking agent owing to its strong multiple hydrogen bonding interactions with PVA, realizing its multifunctional application. The PCAAG organohydrogel possessed outstanding physical and mechanical properties (350.54% of the maximum fracture strain and 1.55 MPa of the maximum tensile strength), considerable bacteriostatic effects against both Escherichia coli and Staphylococcus aureus, and excellent freeze resistance (it could function normally at -20 °C). The motion-monitoring sensor based on the PCAAG organohydrogel exhibited excellent specificity recognition for both large-amplitude (e.g., elbow bending, wrist bending, finger bending, running and walking, etc.) and small-amplitude (frowning and swallowing) human movements. The flexible keyboard constructed by using the PCAAG organohydrogel could easily achieve the transformation between digital signals and electrical signals, and the signal output had both specificity and stability. The velocity-monitoring sensor fabricated by using the PCAAG organohydrogel could accurately measure the speed of the object movement (less than 3% of relative error). In short, the present PCAAG organohydrogel solves the problems of the single application environment and a few application scenarios of traditional conductive hydrogels and possesses remarkable application potential as a multifunctional FSD in many fields such as artificial intelligence, sport management, soft robots, and human-computer interface.

Abiotic synthesis with plausible emergence for primitive phospholipid in aqueous microdroplets

Phospholipids are the protective layer of modern cells, but it is challenging for the formation of phospholipids that require a simple abiotic synthesis before the advent of primitive cells. Here, we reported the abiotic synthesis for lysophosphatidic acids (LPAs) with prebiotically plausible reactants in aqueous microdroplets under ambient conditions. The LPAs formation is carried out by fusing two microdroplets streams: one contains glycerol and pyrophosphate in water and the other one contains fatty acids in acetonitrile. Compared with the bulk solution, LPAs were generated in microdroplets without the addition of catalyst and heating. Conditions of reactant concentrations and microdroplet size varied and suggested that LPAs formation occurred near or at the microdroplet surface. The LPAs formation also showed chemoselective toward on chain-length of fatty acids. Finally, the formation of LPAs underwent two-step reactions with glycerol phosphorylation eliminating one water molecule followed by esterification with fatty acids. These results also implicated that pyrophosphate functioned as both catalysts and precursors in prebiotic LPAs synthesis. The approach using fusion aqueous microdroplets has desirable features in studying the substance exchange and interaction in atmosphere.

Synthesis and Characterization of Banana Peel Starch-based Bioplastic for Intravenous Tubes Preparation

The work undertaken in this paper intends to reduce the negative environmental effects of single-use plastics especially to trim down the medical waste generated post-utilization of plastic intravenous tubes. The present study emphasises on the production, characterization of banana peel starch-based bioplastic with Glycerin as bioplastic adhesive or plasticizer. Single-use plastic medical wastes derived from petroleum-based sources continue to accumulate in landfills and leach into the environment. Managing plastics and medical wastes tends to be an urgent environmental crisis and poses a serious threat to the same, and switching to biodegradable plastics can help to alleviate the problem. Three assorted banana peel starch-based bioplastic samples were fabricated using assorted mixtures of Banana peel starch, Corn starch, Vinegar, Glycerin and distilled water. All the three samples were subjected to evaluation tests such as moisture content, water absorption, water solubility, alcohol solubility, Soil degradation, tensile strength study and FTIR analysis. In addition, the intravenous tube was simulated using ANSYS software, and its flow and velocity profiles were studied and tested. Obtained results evince that banana peel starch-based bioplastic sample-II has the necessary physiochemical and mechanical properties, which may be printed and moulded as intravenous tube in future, for infusion and transfusion applications.

Green extraction of bioactive compounds from Azadirachta indica in aqueous glycerol and modelling and optimisation by response surface methodology

Abstract Development of efficient and green methods for extracting bioactive phytochemicals has great industrial value. Increasing environmental sensitivity at the global level has tremendously enhanced the demand for such methods. Azadirachta indica is a well-known medicinal tree. As glycerol has emerged as a green and safe extraction solvent for bioactive phytochemicals, this study aimed to investigate the efficacy of a glycerol–water solvent system to extract bioactive compounds from A. indica leaves. Modelling and optimisation were carried out by using response surface methodology (RSM) as per the Box–Behnken design with three variables, namely, solvent concentration, time and temperature. The responses were total phenolic content (TPC), total flavonoid content (TFC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and metal chelating activity (MCA). The optimum conditions found by numerical optimisation were a solvent concentration of 69.713%, a time period of 38.328 min and a temperature of 32.114 °C with the predicted values of TPC, TFC, %DPPH and %MCA as 5.27 mg gallic acid equivalents · g−1 DW (dry weight), 9.869 mg rutin equivalents · g−1 DW, 73.8% and 54.366%, respectively. The validation experiments showed almost the same results for each response with very low% errors (5.431–7.661). Increasing glycerol concentration in the extracting medium favoured the extraction of TPC, TFC and antioxidant phytochemicals, but for MCA, the trend was the opposite. In conclusion, 70% aqueous glycerol is an effective medium for the extraction of polyphenolic and antioxidant phytochemicals from A. indica leaves. Extraction models suggested by RSM have high prospects to be used on a large industrial scale.

Synthesis of Ibuprofen Monoglyceride Using Novozym®435: Biocatalyst Activation and Stabilization in Multiphasic Systems

This work was focused on the enzymatic esterification of glycerol and ibuprofen at high concentrations in two triphasic systems composed of toluene+ibuprofene (apolar) and glycerol or glycerol–water (polar) liquid phases, and a solid phase with the industrial immobilized lipase B from Candida antarctica named Novozym®435 (N435) acting as the biocatalyst. Based on a preliminary study, the concentration of the enzyme was set at 30 g·L−1 and the stirring speed at 720 r.p.m to reduce external mass transfer limitations. To obtain more information on the reaction system, it was conducted at a wide range of temperatures (50 to 80 °C) and initial concentrations of ibuprofen (20–100 g·L−1, that is, 97 to 483 mM). Under these experimental conditions, the external mass transfer, according to the Mears criterion (Me = 1.47–3.33·10−4 << 0.15), was fast, presenting no limitation to the system productivity, regardless of the presence of water and from 50 to 80 °C. Considering that the enzyme is immobilized in a porous ion-exchange resin, limitations due to internal mass transfer can exist, depending on the values of the effectiveness factor (η). It varied from 0.14 to 0.23 at 50 to 80 °C and 0.32–1 mm particle diameter range in the absence of water, and in the same ranges, from 0.40 to 0.66 in the presence of 7.4% w/w water in the glycerol phase. Thus, it is evident that some limitation occurs due to mass transfer inside the pores, while the presence of water in the polar phase increases the productivity 3–4 fold. During the kinetic study, several kinetic models were proposed for both triphasic reacting systems, with and without first-order biocatalyst deactivation, and their fit to all relevant experimental data led to the observation that the best kinetic model was a reversible hyperbolic model with first-order deactivation in the anhydrous reaction system and a similar model, but without deactivation, for the system with added water at zero time. This fact is in sharp contrast to the use of N435 in a water-glycerol monophasic system, where progressive dissolution of ibuprofen in the reacting media, together with a notable enzyme deactivation, is observed.

A terminal-velocity model for super-ellipsoidal particles

The prediction of the terminal velocity of non-spherical particles, such as sediments and microplastics, is essential for understanding their transport processes in rivers or marine environments. However, most of the existing models have been proposed based on specific particle materials, and there is a lack of systematic research on the effects of different shape factors on terminal velocity. In this study, super-ellipsoidal particles were selected as test particles for settling experiments, and a particle–velocity tracking code was developed to measure their terminal velocities during falling through glycerin–water mixtures. A terminal–velocity model for super-ellipsoidal particles was proposed based on the measured data. Owing to the new model, multivalued predictions of the terminal velocity based on a single shape factor, such as sphericity and Corey shape factor, were disclosed, and the prediction errors were evaluated. The results of this study can provide a basis for establishing a general terminal–velocity model that considers the influence of particle shape.

On the Stability of Particle–Particle Interaction during Gravitational Settling

The elevated energy demand and high dependency on fossil fuels have directed researchers’ attention to promoting and advancing hydraulic fracturing (HF) operations for a sustainable energy future. Even though previous studies have demonstrated that the proppant suspension and positioning in slickwater play a vital role during the shut-in stage of the HF operations, minimal experimental work has been conducted on the fundamental proppant–proppant interaction mechanisms, especially a complete mapping of the interactions. This study utilizes high-speed imaging to provide a 2D space- and time-resolved investigation of two-particle (proppant models: 2 mm Ø, 2.6 g·cm−3) interactions during gravitational settling in different initial spatial configurations and rheological properties. The mapping facilitates the identification of various interaction regimes and newly observed particle trajectories. Pure water results at a settling particle Reynolds number (Rep) ~ 470 show an unstable particle–particle interaction regime characterized by randomness while altering pure water to a 25% (v/v) water–glycerin mixture (Rep ~ 200) transitions an unstable interaction to a stable prominent repulsion regime where particles’ final separation distance can extend up to four times the initial distance. This indicates the existence of Rep at which the stability of the interactions is achieved. The quantified trajectories indicate that when particles are within minimal proximity, a direct relation between repulsion and Rep exists with varying repulsion characteristics. This was determined by observing unique bottle-shaped trajectories in the prominent repulsion regimes and further highlighted by investigating the rate of lateral separation distance and velocity characteristics. Additionally, a threshold distance in which the particles do not interact (or negligibly interact) and settle independently seems to exist at the normalized 2D lateral separation distance.