Volume 56, Issue 2

The control of infections and maintenance of hygienic conditions are of central importance and the insights gained through several investigations have practical significance today. In contrast, the maintenance of environment and surface disinfection is still controversial and demands novel disinfectants to meet the required criteria. The healthcare centers are fraught with various microorganisms and serve as a point source for multidrug resistance in patients which is more critical to treat. Therefore, it has begun a comprehensive plan in hospitals to focus on disinfection and maintenance of hygiene which is not always appreciated. The urgency to determine the effectiveness of disinfectants is often questioned. The review article shows how the existing problems could be solved by a systematic approach and reports on effective evaluation studies that meet the requirements.

The ubiquitous finding of microplastic in the abiotic and biotic environment has gained a lot of attention recently in the media, scientific community and among the general public. One of the known sources of microfibres is the washing of textiles. It would be a conceivable option to install filters in domestic washing machines that would sift out microplastics to prevent this pollution. The aim of this paper was to conduct a comprehensive literature search on microplastics filters in washing machines published already. Although the results of this research show that there has been an effort to find solutions for this problem in a worldwide context, there has been no known proven system that prevents microfibre release in the aquatic environment which does not have a harmful influence on the washing behaviour and/or washing results.

The study was an attempt to develop fabric softener formulations with a markedly higher content of active substances compared to traditional products. The assumption was to design the formulations in such a manner as to eliminate problems associated with the application of cationic surfactants at high concentrations, and to obtain products exhibiting a high level of quality (products characterized by functionality and usability expected by consumers). The selection of magnesium chloride concentration in products of this type was found to be related to the desired product concentration. It was also demonstrated that by adding salt to concentrated fabric softeners, it is possible to regulate their viscosity and dissolution time in water, and also reduce the viscoelastic properties which are undesirable in the process of manufacture of such products.

This study aimed to investigate the simultaneous removal of methylparaben (MePB) and propylparaben (PrPB) from effluents (each one at 16 mg/L) using a nonionic micellar system containing Triton X-114. Response surface methodology (RSM) has been carried out. Extraction results using nonionic surfactant two-phase system were considered as a function of surfactant concentration and temperature variation. Four responses were investigated: MePB and PrPB extraction yield (E), solute (X s,w ) and surfactant (X sf,w ) concentrations in the aqueous phase and the volume fraction of micellar phase (ϕ C ) at equilibrium. Very high extraction efficiencies (99 % for PrPB and 84 % for MePB) were achieved at optimal conditions. Thereby, the amounts of PrPB and MePB were reduced 80 and 5 times, respectively. The extraction improvement using sodium sulfate was also shown. Finally, the solute stripping from micellar phase by pH change was proved.

The emulsion of hydrocarbon components in water is usually found in the wastewater of refineries. In this work, a mathematical modeling of the destabilization process of gas condensate droplets in water emulsions was constructed using the population balance equation, and the coalescence coefficient (agglomeration kernel) of different demulsifiers (KENON 20, KENON 4, KENON 2, CTAB, SDS, Span 80, Span 60, Polyamide, Polyacrylamide and an EO/PO block copolymer of dodecan-1-ol) was obtained. For modeling, it needs droplets size distribution before adding a demulsifier at time = 0 and after adding a demulsifier at time = 1 h and 2 h. For this purpose, the numerical method of Crank-Nicolson by MATLAB software was applied. Additionally, the growth of gas condensate droplets was modeled by the population balance, and the agglomeration kernel for each demulsifier with the help of two models (simple flow and sum of the volumes) was determined. Moreover, the dependency of the agglomeration kernel to time was obtained. The results showed that the accuracy of the sum of the volumes model was better than the simple flow model to describe destabilization of the emulsion with demulsifiers. Furthermore, the agglomeration kernel of demulsifiers increases with increasing the demulsification time.

As a result of growing awareness, consumers are increasingly interested in products that are safe on the skin and environmentally-friendly. This is one of the most important reasons for the very rapid development of the natural cosmetics segment which has been observed for several years now. Among the most commonly used anionic surfactants of natural origin are sodium lauryl sulfate (SLS) and sodium coco sulfate (SCS). As there are no unambiguous reports on the safety of using SCS, in this study an attempt was made to evaluate the effect of SCS on the skin. The results of the determination of the skin irritation potential (zein value) indicate that the analyzed parameter is approximately 15 % lower in SCS than in SLS. SCS has a stronger ability to interact with epidermal lipids and cause their elution from the skin, which in turn may damage the protective epidermal barrier. The results obtained during the evaluation of the effect produced by the analyzed substances on the metabolism of human keratinocytes (HaCaT) show that after 4 h of incubation with the studied groups of compounds there was a significant decrease in cell proliferation. The highest decrease in cell metabolism was demonstrated for SLS.

In the presence of dodecylbenzene sulfonic acid (DBSA), a part of the phase diagram of water, oleic acid, and n -octanol was constructed as a function of the temperaure dependent from DBSA-concentration. The liquid three-phases microemulsion region in the phase diagram was efficient for the esterification of oleic acid and n -octanol. The results exhibit that the shift of phase boundary contributed to product separation and catalyst recycling.

Surfactants play an important role in enhanced oil recovery by reducing the interfacial tension (IFT) between oil and water and changing the wettability of reservoir rock. Studies have been made to determine the effect of temperature, salt, alkali and polymer on IFT in the presence of anionic (SDS), cationic (CTAB) and nonionic (Tween 80) surfactants. The experimental data reveal that with increase in temperature the surface tension and IFT of the above surfactants are significantly reduced. IFT values of surfactants are also affected by the presence of polymer, alkali and salt. The results show that the addition of polymer increases the IFT as well as the contact angle of all the surfactant solutions. On the other hand, the presence of alkali in surfactant solution reduces the IFT between crude oil and water as alkali reacts with the acidic components of crude oil to form additional in-situ surfactants. It has been found that the presence of salt in an aqueous solution of different surfactants reduces IFT and contact angle as the salt increases the tendency of the surface active agents to accumulate at the interface. Sand pack flooding in presence of different chemical combinations has also been investigated. It has been found that the enhanced oil recovery by alkali-surfactant-polymer flooding is better than the corresponding surfactant and surfactant-polymer flooding.

The adsorption of sodium dodecyl sulfate (SDS) and N,N-dimethyldodecan-1-amine oxide (DDAO) and their mixtures from their solutions, onto Jordanian Natural Clay (JNC) was investigated at room temperature. The clay was firstly analyzed with X-ray fluorescence technique. The surface tension of the single and mixed surfactant solutions was then measured as a function of the total surfactant concentration and the critical micelle concentration ( CMC ) values of these solutions were determined. The interaction between SDS and DDAO as indicated by their interaction parameter was calculated according to the regular solution model. Adsorption of single surfactants onto 3 % wt/vol Jordanian Natural Clay, using the depletion method, was ultimately investigated. Although no absorbed SDS molecules were found onto the Jordanian Clay, but a pronounced adsorption tendency for DDAO and mixed SDS/DDAO molecules was obtained. The amounts of surfactant adsorbed onto 3 wt/vol% JNC follow the trend: SDS/DDAO > DDAO > SDS indicating the importance of synergistic interaction of surfactants on their adsorption behavior.

The viscosity, specific viscosity, and fluidity of Cu(II) surfactant complexes derived from mustard oil with urea/thiourea/2-amino-6-chloro benzothiazole in a non-aqueous solvent has been determined at a constant temperature of 303.15 K. The results were used to determine the critical micelle concentration (CMC), soap complex-solvent interactions and the effect of chain length of the surfactant molecule on various parameters. The conclusions with regard to solute-solute and solute-solvent interaction have been discussed in terms of well-known Moulik and Jones-Dole equations. The effect of surfactant concentration on the viscosity of the solution in non-polar solvent has been discussed. The observations suggested that the structure breaking effect by the solute on the solvent molecules is more prominent above CMC as compared to below CMC after the formation of the micelles. This information plays a role in various industrial and biological applications.