Coalescence, Spreading, and Rebound of Two Water Droplets with Different Temperatures on a Superhydrophobic Surface

Carbon Nanotube Enhanced Filtration and Dewatering of Kerosene

Current approaches to dewatering aviation fuel such as kerosene are adsorption by activated charcoal, gravity separation, etc. The objective of this work is to develop and demonstrate the filtration and dewatering of kerosene using a carbon nanotube immobilised membrane (CNIM). Highly hydrophobic membranes were prepared by immobilising carbon nanotube (CNTs) over polytetrafluoroethylene (PTFE) and polyvinylidene difluoride (PVDF) microfiltration membrane for the dewatering of ppm level water from kerosene. The effects of different CNT concentrations on membrane morphology, hydrophobicity, porosity, and permeability were characterised. After immobilising CNT into membranes, the contact angle increased by 9%, 16%, and 43% compared to unmodified 0.1 μm PTFE, 0.22 μm PTFE and 0.22 μm PVDF membranes, respectively. The CNIM showed remarkable separation efficiency for the fuel-water system. The micro/nano water droplets coalesced on the CNT surface to form larger diameters of water droplets detached from the membrane surface, leading to enhanced water rejection. In general, the water rejection increased with the amount of CNT immobilised while the effective surface porosity over pore length and flux decreased. PTFE base membrane showed better performance compared to the PVDF substrate. The CNIMs were fabricated with 0.1 and 0.22 μm PTFE at an optimised CNT loading of 3 and 6 wt.%, and the water rejection was 99.97% and 97.27%, respectively, while the kerosene fluxes were 43.22 kg/m2·h and 55.44 kg/m2·h respectively.

A Review of Biopolymers' Utility as Emulsion Stabilizers

Polysaccharides, polynucleotides, and polypeptides are basic natural polymers. They have various applications based on their properties. This review mostly discusses the application of natural polymers as emulsion stabilizers. Natural emulsion stabilizers are polymers of amino acid, nucleic acid, carbohydrate, etc., which are derived from microorganisms, bacteria, and other organic materials. Plant and animal proteins are basic sources of natural emulsion stabilizers. Pea protein-maltodextrin and lentil protein feature entrapment capacity up to 88%, (1-10% concentrated), zein proteins feature 74-89% entrapment efficiency, soy proteins in various concentrations increase dissolution, retention, and stability to the emulsion and whey proteins, egg proteins, and proteins from all other animals are applicable in membrane formation and encapsulation to stabilize emulsion/nanoemulsion. In pharmaceutical industries, phospholipids, phosphatidyl choline (PC), phosphatidyl ethanol-amine (PE), and phosphatidyl glycerol (PG)-based stabilizers are very effective as emulsion stabilizers. Lecithin (a combination of phospholipids) is used in the cosmetics and food industries. Various factors such as temperature, pH, droplets size, etc. destabilize the emulsion. Therefore, the emulsion stabilizers are used to stabilize, preserve and safely deliver the formulated drugs, also as a preservative in food and stabilizer in cosmetic products. Natural emulsion stabilizers offer great advantages because they are naturally degradable, ecologically effective, non-toxic, easily available in nature, non-carcinogenic, and not harmful to health.

Drop-on-Drop Impact Dynamics on a Superhydrophobic Surface

Investigation of multiple droplet interactions is vital due to its importance in various applications, including sprays. In this context, the interaction of a sessile droplet (droplet #1) interaction with an oncoming droplet (droplet #2), in a vertically aligned, drop-on-drop configuration, on a superhydrophobic surface is investigated, both experimentally and computationally. Three droplet impact regimes, with low We number of the impacting droplet (i.e., We_droplet #2 ∼ 1.0) is observed, viz., gentle merging, late merging, and droplet bounce-off without merging. Complementary simulation of the gentle merging regime shows that a very high-pressure gradient is generated between the neck and the bulk region immediately after the contact, which acts as a driving force for the subsequent rapid evolution of the droplet shape. With a larger We number (We_droplet #2 ∼ 8.2 and 14.8), there is always a unique outcome of the impact experiments. The two droplets merge, spread, recede, and bounce-off; there are multiple instances of rebound of the combined droplet mass from the surface. The estimated shear stress emanating during the impact and subsequent dynamics is large enough to cause deterioration of chemically coated superhydrophobic surfaces. The difference in the shape of moving droplet #2 at the instance of impact for We_droplet #2 ∼ 1, as compared to We_droplet #2 ∼ 8.2 and 14.8 is also highlighted. Important time scales during coalescence and beyond are the inertial-capillary time scale (∼16 ms) and viscous-capillary time scale (∼8 s). We also highlight the role of the droplet #1 deposition boundary condition, influence of the We number of droplet #2, and substrate wettability on drop-on-drop interactions, which has direct relevance to the transport mechanisms happening in various engineering applications like spraying pesticides, spray cooling, and rain interactions, etc.

Scientific information about sugar-based emulsifiers: a comprehensive review

The instantaneous demand for foods, detergents, cosmetics, and personal care products that can be commercialized with value-added benefits including natural origin, environmental friendliness, and sustainability is increasing day by day. Accordingly, the associated industries are trying to identify bioactive ingredients that may be natural alternatives to synthetic ones. This review article is mainly aimed at the classification of natural saccharide-based emulsifiers (which are mainly bio-surfactants), their methods of preparation and their various types of applications in daily life activities. Different routes of production of mono and polysaccharide-based emulsifiers and their industrial advantages are exclusively highlighted. The readers can get an approach on how sugar-based emulsifiers are synthesized and used in the pharmaceutical, food, and personal care industries to contribute excellent physicochemical properties and feature excellent functional characteristics. Many of the synthetic procedures are associated with the use of natural ingredients to prepare emulsions concerning “eco-friendly” selective materials. In this report, an endeavour has been made towards contextual examples for the production methods of some saccharide-based emulsifiers and their advantages in various fields.

Amphiphilic natural emulsifiers form tiny droplets of oil-in-water stable emulsions and are very much effective for industries.

Anthropogenic emissions from the combustion of composite coal-based fuels

Composite fuels made of waste from coal, petroleum and wood processing industries have a high environmental and economic potential. In this research, we experimentally studied the concentrations of the most hazardous gaseous anthropogenic emissions (CO₂, SO₂, NO) from waste-based fuel combustion. Using two techniques operating in complementary temperature ranges, we obtained data on SO₂ and NO emissions in the temperature range from 300 °C to 1000°C, including all the stages of thermochemical conversion of fuels. A quasi-stationary technique was used, based on a setup of thermogravimetric analysis with mass spectrometry, to obtain information in a low-temperature range (300-600°C). This technique allows the conversion at a low controlled rate of heating a sample together with the furnace. To obtain data in a high-temperature range (700-1000°C), a non-stationary technique was used, where the sample was introduced into a pre-heated furnace. The conditions were established in which it was possible to reduce the concentration of flue gases from the combustion of the compositions under study (replacement of the coal part with water, injection of water vapor, addition of biomass, selection of the temperature range). The impact of water vapors was determined when they were injected into the chemical reaction zone together with air and when they were formed naturally by evaporation from the fuel sample. Unlike biomass that reduces the emissions of sulfur oxides from composite fuels due to the mechanical dilution of the mixture, water vapor present in the heterogeneous reaction zone decreases the gaseous anthropogenic emissions through chemical reactions and conversion of a part of fuel sulfur and nitrogen to an inactive form (neutral to the environment).