Volume 61, Issue 1

This article focuses on the description of novel mixed system formulations of bis-quaternary ammonium salts (bis-QASs) and the nonionic surfactant Triton X-100 (TX-100). Measurements of surface tension ( γ ), foam stability, contact angle (CA) and cloud point (CP) were investigated at different ratios of the given compounds. The results indicated that changes in the structure of the bis-QASs amphiphilic cation, including the length of the alkyl spacer and the presence or absence of –OH groups, affected the adsorption and micellization. Furthermore, the elongation of the alkyl spacer in the bis-QASs structure affects the increase in the CP temperature. The research carried out shows the future potential of mixed combinations (bis-QASs and TX-100) to be used in industrial applications.

In addition to high cleaning performance, many consumers pay special attention to low energy and water consumption in automatic dishwashers. Eco programs are designed to effectively clean normally soiled dishes with low energy and water consumption. However, Eco programs are relatively long and consumer acceptance of programs lasting longer than 2 h is not very high. The vast majority of short programs for lightly soiled dishes consume equal to lower amounts of energy and water than Eco cycles on average. In this study, we investigate the effect of different dishwasher programs on the cleaning performance for a variety of soils using four different market detergents. The results show that the detergent has a major influence on the cleaning result, especially for short cycles and that for certain short cycle/cleaner combinations similar good results can be achieved as with Eco cycles. The data collected were also used to train predictive models to make forecasts on cleaning performance for unknown program parameter combinations, and to examine the multivariate relationships of the program parameters and the cleaners in more detail.

As a natural, non-toxic adsorbent, chitosan is well suited for the removal of heavy metals and antibiotics. In this study, chitosan was modified with polypropylene glycol and itaconic anhydride to improve the mechanical properties of chitosan, and the polypropylene glycol-itaconic anhydride-chitosan adsorbent was successfully prepared. The adsorbent was characterised and analysed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis and X-ray photoelectron spectroscopy (XPS). The effects of the different conditions on the adsorption of Pb 2+ and cephalexin were investigated. The Langmuir adsorption isotherm model showed that the maximum adsorption capacities of Pb 2+ and cephalexin could reach 431.73 mg g −1 and 153.72 mg g −1 , respectively. The possible adsorption mechanism of Pb 2+ and cephalexin was discussed.

This work concerns the coacervate extraction of industrial dye, namely Acid Green 9 (AG-9) from aqueous solution by nonionic surfactant Lutensol AO7 and TX-114 (readily biodegradable). Binary water/surfactant and pseudo-binary phase diagrams were plotted. The extraction results as a function of wt% of the surfactant and temperature are expressed by: percentage of solute extracted, E %, residual concentrations of solute and surfactant in the dilute phase ( X s,w and X t,w respectively) and volume fraction of coacervate at equilibrium (Ф c ). For each parameter, whose values are determined by a design of experiments, these results are subjected to empirical smoothing in three dimensionsusing response surface methodology (RSM). The aim of this study is to find out the best compromise between E  % and Ф c . Under optimal conditions, the extraction extent of AG-9 reaches 98 % and 96 % using TX-114 and Lutensol AO7, respectively. The effect of Na 2 SO 4 and CTAB addition is also studied. Finally, the possibility of recycling the surfactant is proved.

The rheological properties of the flotation slurry are one of the most important factors affecting the separation by this process. The presence of clay in the flotation process causes many problems due to its effect on the slurry rheology. In this study, the effect of glauconitic clay on the rheological behaviour of semi-salt type minerals (phosphate and calcite) in the presence/absence of anionic surfactant (sodium lauryl sulfate, SLS) as flotation reagent was investigated as a preliminary step towards understanding their behaviour during flotation. The results showed that the flow behaviour of each mineral, either phosphate or calcite was Newtonian. When glauconite was added in the absence of surfactant, the behaviour shifted to that of Bingham fluids with yield stress for both slurries. When glauconite was added to phosphate slurry in the presence of the surfactant, the behavior was strictly Newtonian, with a slight increase in viscosity with increasing glauconite content. The addition of SLS to calcite slurries shifted the behaviour from Newtonian behavior to shear thickening, with an increase in yield stress and viscosity with addition of glauconite, reaching a maximum value at 10 % addition and then decreasing with further addition of glauconite.

The interactions between a gemini surfactant 12-2-12 and bovine serum albumin (BSA) have been studied in aqueous and mixed aqueous media by conductance measurements using the iterative method at different temperatures ranging from 298.15 K to 313.15 K with step size 5. The critical micellar concentration (CMC) as well as the degree of ionization for the micelles ( α ) have been evaluated and their variation with solvent type and temperature has been discussed. The error for conductivity measurements was calculated and found to be much smaller than for surface tension measurements using the platinum ring method. The CMC values for the mixture of 12-2-12 and BSA in aqueous solvent solutions follow the sequence: DMF > AN > DMSO > water. These values were further confirmed by surface tension studies. From the thermodynamic parameters, hydrophobic interactions were found to be the driving force for micellization. The existence of enthalpy-entropy compensation was established from the linear plot of Δ H ° m and Δ S ° m .

In this work, the functional groups of Eurohypnum leptothallum extract (ELE) were extracted by aqueous immersion and identified by FTIR. The corrosion inhibitory effect of ELE as a natural plant corrosion inhibitor on pure iron in 0.5 mol L −1  H 2 SO 4 solution was investigated by test methods such as the weight loss method, electrochemical behaviour and detection of metal surface topography. The results show that ELE has a positive inhibitory effect on the corrosion behaviour of pure iron in 0.5 mol L −1 H 2 SO 4 solution, and the higher the concentration of ELE, the greater the corrosion inhibitory effect. It can still reach 83.97 % at high temperatures. The results of SEM examination and contact angle measurements show that the corrosion degree of the metal decreases significantly after the additon of ELE and that the hydrophobicity of the metal surface increases. The adsorption of ELE on the surface of pure iron tends to isothermal Langmuir adsorption and, as a mixed corrosion inhibitor, the charge transfer resistance of the system increases significantly and the capacitance value of the electrical double layer decreases significantly.

Two novel UV photosensitive micellar systems, trimeric dodecyl anionic–cationic surfactant (TDCC)/ trans -OMCA, and trimeric cetyl anionic–cationic surfactant (TCCC)/ trans -OMCA, were successfully synthesized by using two different carbon chain length trimeric anionic–cationic surfactants (TACS, including TDCC and TCCC) and the photosensitive additive trans -o-methoxycinnamic acid ( trans -OMCA). The incorporation of trans -OMCA resulted in a peak in the zero shear viscosity ( η 0 ) of the system at pH = 6.17–6.61. The flow behaviour of the TACS/OMCA system was well described by the Carreau-Yasuda model. Prior to UV irradiation, the TCCC/ trans -OMCA system exhibited pronounced shear thinning, thixotropic, and viscoelastic properties. After UV irradiation at 365 nm, the isomerization of trans -OMCA to cis -OMCA caused the disruption of the network structures, leading to a significant decrease in the thixotropic and viscoelastic properties, resulting in a decrease in viscosity. The viscosity reduction rate of the TCCC/ trans -OMCA system reached 99 %. The influence of the hydrophobic carbon chain length on the UV responsiveness was also investigated. The TDCC/ trans -OMCA system exhibited an 86 % decrease in η 0 after UV irradiation, highlighting the favorable effect of longer hydrophobic tail chains in improving the UV responsiveness of the micellar system. The UV light kinetics of the TCCC/ trans -OMCA solution were studied and a rheological model was developed to accurately describe the viscosity changes. The TCCC was found to predominantly exhibit cationic characteristics at pH = 6.17–6.61. In this pH range, the 2 wt% TCCC/0.12 wt% NaSal system exhibited excellent viscoelasticity, and the addition of trans -OMCA disrupted the network structure resulting in a decrease in viscosity. After UV irradiation, the viscosity of the system increased by 2.5 times, confirming the potential of the TCCC/NaSal/ trans -OMCA micellar system as a UV thickener.

Amphiphilic surfactants, which are currently used mainly for cleaning purposes, are produced in large quantities from petroleum, but are often harmful to the environment and poorly biodegradable. Therefore, the importance of environmentally friendly, non-toxic and skin-friendly biosurfactants is increasing. Different types of biosurfactants exist depending on their molecular structure. Trehalolipids belong to the low molecular weight glycolipids. Compared to other microbial glycolipids, they often show different properties and performances, including inhibition and enhancement of biodegradation rates. Optimisation of their production and downstream processing is one of the major obstacles to the potential use of trehaloselipids in a range of applications. This review provides an overview of different substrates and microorganisms used for trehalose lipid production, as well as various applications in bioremediation, biomedicine and microbial enhanced oil recovery.

A comparison is made between synthetic and biosurfactants in terms of their origin, structure, physico-chemical properties, applications, production costs, toxicity, biodegradability and environmental impact. It is shown that the chemical structure of surfactants synthesised by living organisms is more complicated than that of those produced by classical methods. The reduction in water surface tension induced by synthetic and biosurfactants is almost the same. Due to their origin and structure, biosurfactants are preferred in medical, cosmetic and food applications, mainly because they are less toxic than synthetic surfactants. Synthetic surfactants require more time and special environmental conditions to start the biodegradation process compared to biosurfactants, which can easily start biodegradation under normal physical conditions. This mini-review highlights this new category of surfactants (biosurfactants). It also provides a comparison between synthetic and biosurfactants is provided using the available data reported in the literature.