Volume 59, Issue 5

Metal corrosion has always been a serious problem in industry. There has always been a need to increase the number of possible, cost-effective corrosion inhibitors. However, many commercially available corrosion inhibitors have both high efficiency and high toxicity, which has led environmental authorities to ban their use. As a result, there is growing interest in scientific research into the use of environmentally friendly compounds. Surfactants and biocompatible corrosion inhibitors are special types of chemicals suitable for long-term industrial use. Molecules with unique hydrophilic and hydrophobic properties can be used in a wide range of applications to solve solubilisation problems and improve extraction processes. The use of surfactant-based products to prevent corrosion on metallic surfaces is a new approach in the field of chemical science. This review article addresses the mechanism of corrosion on metal surfaces and discusses in detail the use of environmentally friendly, cost-effective and readily available surfactants as corrosion inhibitors. The properties and applications of different types of surfactants are also discussed.

Despite numerous remarkable developments in clinical therapy, the world remains firmly in the grip of fungal infections. While conventional approaches to antifungal therapy are failing, dermatophytes continue to affect people’s daily lives, especially in humid and tropical areas, and pose a major medical problem. Cubosomes, the liquid crystalline nanostructures, are among the recently developed lipid nanoparticles that could potentially overcome the hurdles of conventional therapy. In the present study, cubosomes containing luliconazole, an antifungal drug, were formulated to overcome the limitation of poor water solubility and poor bioavailability of the drug for the main purpose of treating fungal infections. Various formulations of luliconazole loaded cubosomes were prepared with different ratios of lipid (glyceryl monooleate) and surfactant (poloxamer 407) using emulsification method. The prepared formulations were optimised and the optimised cubosomal dispersion was loaded into a carbomer-934 gel to form an emulsifying gel. All cubosomal dispersions had particle sizes ranging from 124 nm to 221.1 nm, optimal zeta potential and polydispersity index, and were found to be stable. The drug entrapment efficiency of the cubosomes was over 90%. The in vitro diffusion study showed that the developed formulation had a higher release rate than the marketed formulation. The in vitro antifungal activity study confirmed that the prepared emulsion formulation was also effective against Candida albicans . The novel drug delivery system developed in this study, the cubosomal emulgel, could thus be a favourable approach for the topical delivery of luliconazole for the treatment of fungal infections.

In this study, graphene oxide (GO) was prepared by the improved Hummers method, and a synergistically stabilized emulsion of GO and emulsifier was formulated. The best emulsion formula obtained by Response Surface Methodology consists of 1.39‰ GO, and 2.92‰ OP-10; the water-oil ratio is 4:6, achieving an emulsion index of 92.83%. The emulsion still maintained good stability under high temperature and high salt conditions, meeting the environmental requirements of medium and low permeability reservoirs. For injected water flooding, emulsion flooding could increase the oil recovery by 15.41%.

Different morphologies of silver nanoparticles (AgNPs) are prepared by reducing silver nitrate with hydrazine hydrate in an aqueous solution in the presence of the anionic surfactant sodium 6,6′-((oxybis(ethane-2,1-diyl))bis(oxy))bis(3-dodecanoylbenzenesulfonate) (SOBS), the cationic surfactant cetyltrimethylammonium bromide (CTAB) and mixtures of these two surfactants as template. By mixing these cationic and anionic surfactants, different aggregates (template) were formed. The properties of the nanoproducts are studied by X-ray diffraction, transmission electron microscopy, energy dispersive X-ray analysis and Fourier transform infrared spectroscopy. The results show that the morphology of the nanosilver can be controlled by changing the ratio of cationic to anionic surfactant in the mixture, resulting in silver nanoparticles with high crystallinity and low aggregation.

The physical and chemical properties of sodium lauryl glutamate were systematically investigated in this work. To determine the critical micelle concentration (CMC) of sodium lauryl glutamate, the surface tension was measured using the Wilhelmy plate method. The Krafft point was determined using the ultraviolet/visible spectrophotometer. The effect of pH on the solute in the solution was studied using potentiometric titration. The critical packing parameter (CPP) and Gibbs free energy (ΔG) of micelle formation were calculated using the corresponding parameters. The temperature-concentration phase diagram of sodium lauryl glutamate was constructed using the dynamic light scattering system (DLS) and polarised optical microscopy (POM). The calculated theoretical data were combined with the actual observed data from the phase diagram. Finally, the phase behaviour of sodium lauryl glutamate was determined.

A new series of carbosilane quaternary ammonium surfactants with different hydrophobic carbosilane structures (triethylsilyl, triisopropylsilyl, trihexylsilyl, triphenylsilyl) and tail groups (C 12 , C 16 , C 18 ) have been synthesized and the structures of the organosilicon carbosilane quaternary ammonium surfactants were determined by means of FTIR, NMR and elemental analysis. The properties of aqueous solutions were determined by electrical conductivity measurements and with the method of maximum bubble formation. Members of this series reduced the surface tension of water to approximately 30.5 mN/m at concentration levels of 0.14 mmol/L.

The objective of this study is to determine the effect of detergent tablets containing zeolite from rice husk ash as builder on chemical water quality and growth of water hyacinth ( Eichhornia crassipes ). Water hyacinth is a plant that grows very readily in waters contaminated by detergent effluent, which can lead to eutrophication. Three detergent formulations were studied, differing only in their zeolite content: F1 (zeolite 15%), F2 (zeolite 20%) and F3 (zeolite 25%). The same formulations containing sodium tripolyphosphate (STTP) instead of zeolite were used for comparison: P1 (STTP 15%), P2 (STTP 20%) and P3 (STTP 25%). The effluents contained the respective formulations at five concentrations (0, 25, 50, 75, 100)%. Water hyacinth growth was studied by plant wet weight, plant height, number of leaves and dry weight, and water chemical parameters were determined by chemical oxygen demand (COD), biological oxygen demand (BOD), total suspended solid (TSS) and pH value. The results of the plant growth studies showed that detergent formulations F1 and F2 and comparative detergent formulations P1 and P2 caused plant growth. The measurements of BOD, COD, TSS and pH showed that the detergent formulation with zeolite had a higher value than the formulation of the comparison detergent. The formulation with a zeolite concentration of 25% (F3) is recommended because it is the best formula that has a negative effect on plant growth compared to formulations F1 and F2. This is supported by chemical parameters among which the COD, BOD and pH values still meet the requirements of the quality standards for detergent waste water.

Sophorolipid (SL) is a surface-active glycolipid biosurfactant with promising industrial applications. It is synthesised by fermentation of hydrophobic and hydrophilic substrates using selected non-pathogenic yeasts. However, its applications are limited by high production costs and ineffective product recovery in downstream purification stages. Natural sophorolipids are produced in six to nine different hydrophobic sophorosides, where the carboxyl end of the fatty acid is either free, which is known as the acidic or open form, or it can be esterified internally to produce the lactonic form. The present study deals with the screening and selection of suitable solvents for the extraction of acidic and lactonic SL from fermentation broth. The optimisation study involves exhaustive extraction with the six different immiscible solvents ethyl acetate, butyl acetate, methylene dichloride, methyl tert.- butyl ether, methyl iso -butyl ketone and methyl ethyl ketone. The partition coefficient (K d ), which is the ratio of the solute concentration in the organic layer compared to the aqueous layer, determines the performance measurement of the extraction process in terms of yield and purity of the desired solute. The factors that influence exhaustive extraction were the broth to solvent ratio and the extraction stages. The optimal extraction conditions for the highest possible yield were a broth to solvent ratio of 1:1 and a number of extraction steps of 2. Methylene dichloride showed better results in terms of yield and selectivity in the extraction of acidic and lactonic SL from the fermentation broth compared to the other solvents investigated. For lactonic SL, the highest K d value determined was 36.6 and for acidic SL the highest K d value was 1.14.