Volume 58, Issue 3

This review discusses surfactants used for chemical flooding, including surfactant-polymer flooding and alkali-surfactant-polymer flooding. The review, unlike most previous reviews in the field, has a surfactant focus, not a focus on the flooding process. It deals with recent results, mainly from 2010 and onward. Older literature is referred to when needed in order to put more recent findings into a perspective.

The requirements for commercial dishwashers differ fundamentally from those for domestic dishwashers. For commercial dishwashers, capacity and programme duration are the main factors. Accordingly, different designs are offered for the different types of requirement. Comprehensive data on the usage behaviour of commercial dishwashers is scarcely available. Within the framework of face-to-face interviews, 200 companies in Germany and Denmark were visited to record their user behaviour. With the help of the data obtained, not only errors in the usage behaviour were found, but also indications of unnecessarily high water and energy consumption, which, inter alia, lead to increased costs for the companies. The results show that manual pre-rinsing in particular leads to increased water consumption. Furthermore, the dishwashers are only partially loaded, which leads to more wash cycles than necessary. In order to ensure the optimal utilisation and correct user behaviour of commercial dishwashers, while simultaneously reducing the impact on the environment, there is an urgent need to educate users better on how to use them correctly.

The interactions between cocopropane bis-guanidinium acetates, tallowpropane bis-guanidinium acetates with bovine serum albumin (BSA) in an aqueous solution were studied by fluorescence and circular dichroic spectroscopy measurements. The aim of the study was to elucidate the influence of the hydrophilic group and the length of the hydrophobic chain of these surfactants on the mechanism of binding to BSA. The results revealed that for both surfactants, at low concentrations, the Stern–Volmer plots had an upward curvature and at high concentrations, the quenching efficiency was decreased with increase in surfactant concentration. Different thermodynamics parameters demonstrated the existence of hydrogen bond and van der Waals force which acting as binding forces. Static quenching was observed among the protein and surfactant. The conformation of BSA was changed at higher surfactant concentrations as shown by synchronous fluorescence and CD spectroscopy. This work reveals the mechanism and binding characteristics between guanidine surfactants and protein, and provided the basis for further applications of surfactants.

In the present study, the micelle aggregation numbers and hydrodynamic radius distributions of the gemini surfactants (abbreviated as C m -(EO) n -E-C m (m = 12–16, n = 1, 2)) were investigated by fluorescence spectroscopy and dynamic light scattering (DLS). The rheological properties of these surfactants were determined using a rheometer. The Surfactants C 14 -(EO)-E-C 14 and C 16 -(EO)-E-C 16 formed worm-like micelles at a concentration of 200 mmol/L. It was found that longer hydrophobic chains or shorter linkage groups promoted the growth of worm-like micelles. Then, the influence of the inorganic salt NaBr and the organic salt sodium salicylate (NaSal) on the formation and properties of wormlike micelles in aqueous C 16 -(EO)-E-C 16 solutions at a surfactant concentration of 20 mmol/L was investigated. The results showed that NaSal could penetrate deeper into the hydrophobic group of the micelle due to its good hydrophobic interaction, which promoted micelle growth and resulted in worm-like micelles. In addition, the tested systems showed a Maxwell behavior at lower frequencies, but deviated from the Maxwell mode at higher frequencies. Finally, the formation of worm-like micelles was also verified by micro polarity measurements.

The interaction of carboxylic acid gemini surfactant 4,8-didodecyl-3,9-dioxo-6-hydroxy-4,8-diaza-1,11-undecanedicarboxylic acid (CGS12) with amphoteric surfactant cocamidopropyl betaine (CAPB) at 258C and pH 7.0 has been investigated using pH titration, surface tension, dynamic light scattering (DLS) and cryogenic transmission electron microscopy (Cryo-TEM) measurements. The pH titration results show that CGS12 exhibits anionic surfactant properties and CAPB exists as a zwitterionic form at pH 7.0. The surface tension results show that the critical micelle concentration (CMC) values of the CAPB/CGS12 mixture are low, and basically exhibit a decreasing trend with decreasing molar ratio of CAPB (X CAPB ). The variation of the CMC of the mixture reveals that the mixing is close to ideal. The DLS results indicate that the CAPB/ CGS12 mixture mainly forms the larger aggregates with the hydrate radii approximately 70-145 nm at various X CAPB . The Cryo-TEM images further demonstrate the CAPB/CGS12 mixtures mainly form vesicles. The results indicate that the aggregate size and microstructure of the mixture change little with the variation of X CAPB .

Three cationic copolymers methacryloxyethyl trimethyl ammonium chloride-butyl acrylate-acrylamide (MTAC-BA-AM terpolymer) were designed and synthesized by emulsion polymerization. Their structures were confirmed by FT-IR and 1 H NMR. The effect of content of hydrophobic monomer butyl acrylate (BA) in MTAC-BA-AM terpolymer on surface activities, flocculation and antibacterial properties were investigated. The study of surface tension shows that MTAC-BA-AM terpolymer has good surface activity due to the introduction of hydrophobic monomer BA. The flocculation experiment showed that the light transmittance of the kaolin suspension supernatant was 98.13% when the dose of MTAC-BA-AM terpolymer in the kaolin suspension was 0.03 mg/L, which was obviously better than the P(MTAC-AM) (91.02%) without hydrophobic modification of BA. The bacteriostatic experiment of MTAC-BA-AM terpolymer showed that as the content of hydrophobic monomer BA in MTAC-BA-AM terpolymer increased the inhibitory rate of MTAC-BA-AM terpolymer aginst Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus)

The growing need for sustainable natural-based surfactants from green chemistry has led to syntheses of surfactants without the use of solvents and without the generation of by-products when milder manufacturing processes are used. The zwitterionic betaine ester surfactants are derived from natural renewable sources and are biodegradable. In this research, the betaine ester surfactant 2-di-methylaminoethyllaurate betaine was synthesized from 2-di-methylaminoehanol and lauric acid derived from coconut oil in a three-step chemo-enzymatic esterification reaction. The enzymatic process was optimized in terms of operating parameters such as temperature, time, molar ratio and enzyme concentration, resulting in a yield of 87.91%. Structural analysis of the intermediate 2-di-methylaminoethyl laurate as well as the final product 2-di-methylaminoethyl laurate betaine was carried out with FTIR and 1 H NMR. The surfactant properties of the betaine were also determined and showed that the betaine can be used as a co-surfactant in many cosmetic and personal care products.

Removal of phosphate impurities is a prerequisite for using phosphate ores in different applications. The flotation process is one of the most promising processes that have been used to improve the phosphate grade. However, the flotation performance depends on the type of the associated impurities to valuable minerals due to their different flotation behaviour that needs more attention. In this paper, the flotation response of impurities at different pH and dodecyl tri-methyl ammonium bromide (DTAB) collector concentrations was investigated using the statistical design of experiments. The results indicated that some impurities were completely removed such as silica and alumina while others are only partially removed at about 72% and 38%, respectively. Thus, based on the impurities response to flotation and their rejection by flotation using DTAB collector, they are classified into two groups. The first group is SiO 2 , MgO, and Al 2 O 3 , while the second group includes only sulphide mineral (FeS 2 ). The lowest rejection percentage for pyrite is due to its chemical composition as a sulphide mineral that has a different interaction with DTAB collector in comparison to first group minerals.

To study the sodium oleate (NaOL) adsorption on quartz and its effect on flotation under weak-acidic conditions, the adsorption characteristics of NaOL on the surface of quartz were determined at pH = 6.5 by Fourier transform infrared spectroscopy (FTIR). The solution chemical calculation results show that NaOL exists as oleic acid (HOL) under weakly acidic conditions. The existence form and charge distribution of quartz and HOL were analyzed by Molecular Dynamics Simulation (MDS) using Materials Studio (MS) software, and the results showed that HOL is prone to the (101) and (100) surfaces of quartz under weak-acidic conditions by hydrogen bonding. The flotation verification test with NaOL as a collector was also performed under weak-acidic conditions. The flotation test led to a partial flotation of quartz into the froth products, reducing the grade of hematite direct flotation concentrate, which is consistent with industrial production.