Volume 53, Issue 6

A series of amino acid-based surfactants with a fixed alkyl chain length and with two carboxyl groups separated by a spacer of one, two or three carbon atoms have been synthesized and evaluated as potential collectors for flotation of calcite and fluorite. A monocarboxylate amino acid-based surfactant having the same length of the hydrocarbon tail was also included for comparison in the study. Experiments using a Hallimond flotation tube showed that although the flotation reagents solely differ in terms of spacer, their efficacy in terms of flotation recovery varied very much. Whereas on calcite at pH 10.5 only the monocarboxylate collector gave a high yield, on fluorite at the same pH both the monocarboxylate and the dicarboxylate collectors with one carbon between the carboxyl groups gave good results. On calcite at the natural pH the monocarboxylate collector was most efficient but the dicarboxylate collectors with a two- and a three-carbon spacer also gave a reasonable recovery. On fluorite at the natural pH the dicarboxylate collectors with a two- and a three-carbon spacer were most efficient. The ζ-potential and the flotation recovery of the mineral particles as a function of added collector were assessed and the adsorption was also monitored by diffuse reflectance infra-red spectroscopy. Taken together, the results showed that small changes in the head group region of the collector can radically affect flotation recovery. This type of knowledge is important to understand flotation selectivity in a mixture of similar minerals.

We report the phase states in dodecyltrimethyl ammonium bromide/water (DDTMABr–H 2 O) lyotropic liquid crystalline system. The temperature-concentration phase diagram of this system has been determined. Isotropic micellar L 1 phase, nematic-calamitic N C and hexagonal E mesophases have been observed in DDTMABr/H 2 O system. Dynamics of transformations of magnetically induced textures in N C and E mesophases has been investigated. Temperature and concentration dependences of the refractive index in the L 1 phase, N C and E mesophases have been determined. The appearance of the magnetically induced aligned textures of N C mesophase and changes of the optical birefringence vs. time have been investigated.

The phase behavior and rheological properties of a lyotropic liquid crystal formed in the lecithin/AEO 20 /IPM/H 2 O system were investigated by means of phase diagram, polarized optical microscopy and rheology techniques at 37°C. After adding polyoxyethylene-20-oleyl ether (AEO 20 ) and isopropyl myristate (IPM) to lecithin solutions, an isotropic liquid phase and an anisotropic liquid crystal phase were found. By analyzing the shear viscosity ( η γ=0.1 ) and yield stress ( σ 0 ), with increase in water content, the η γ=0.1 and σ 0 increase firstly and then decrease; with increasing IPM content, a decrease in the η γ=0.1 and σ 0 is observed. Notably, at the relatively higher water content area, the water content has little effect on the η γ=0.1 and critical stress. When the lecithin/AEO 20 mass ratio is 1:2, the liquid crystal phase displays a stronger shear resistance and more stable network structure.

The micelle formation of N -alkyl- N -methylmorpholinium bromide (C n MMB, n = 12, 14, 16) surfactants in aqueous solution has been investigated. Their critical micelle concentration ( CMC ), effectiveness and efficiency of the surface tension reduction, and the maximum surface excess concentration were derived from the surface tension curves. Thermodynamic parameters were then evaluated in the temperature range of 25 °C ∼ 45 °C. The results showed that with increasing the alkyl chain length, the CMC values were decreased gradually, which is consistent with the enhancement of hydrophobic effect. Due to the existence of an oxygen atom in the headgroup, an unusual surface activity of C n MMB surfactants was obtained. The obtained results should help to better understand the effect of the hydrophilic headgroup on the micelle behavior of cationic surfactants containing saturated nitrogen-containing heterocycles.

In times of low-temperature washing, laundry hygiene gains importance, as microbial contaminations on textiles can cause infection transmission and malodour formation. This study systematically investigated the antimicrobial effect of laundry detergents (solid and liquid market detergents) with regard to time and temperature in domestic washing machines. To evaluate the microbial reduction, cotton swatches contaminated with Staph. aureus, Ent. hirae, Ps. aeruginosa, C. albicans and T. mentagrophytes were washed at 20 to 60 °C, varying the washing time, with and without detergent. All tested washing factors affected the antimicrobial effect of to a varying extend, depending on the germ. The used solid market detergent containing activated oxygen bleach provided a way to achieve high microbial reductions in low temperature washing.

Commercial dishwashers are used in community facilities such as hospitals, refectories, nursing homes or food services. In this area, kitchen and food hygiene is of great importance to ensure consumer health. The aim of this study was to verify the hygienic performance of commercial dishwashers with a water-change system by use of bioindicators. This test method is described in DIN SPEC 10534. Micrococcus luteus was used as the test germ instead of Enterococcus faecium as it imposes no pathogenic risk. Micrococcus luteus was identified in initial studies as an appropriate test germ for hygiene studies. Cleaning and rinsing temperatures and holding time of the cleaning program were varied. High rinsing temperature with a constant cleaning temperature and high cleaning temperatures with a constant rinsing temperature led to a reduction of the viable cell count. Increasing the cleaning temperature resulted in a higher decrease of the viable cell count than increasing the rinsing temperature.

The objective of this research was to study the deposition mechanism of hueing dyes on different fabric surfaces. In this study, two types of fabrics and four types of hueing dyes were used to study the dye accumulation behaviors on fabric samples. The results showed that nylon and cotton treated with hueing dyes had a lower b* value and a higher CIE whiteness. Furthermore, the accumulation level of hueing dyes on nylon was much higher than on cotton fabric. The chemical composition of fabrics and molecular structures of hueing dyes were also investigated to study the interactions between different fibers and dyes. The results showed that the over-deposition of hueing dyes on fabric was mainly driven by the electrostatic forces, which could be weakened by adding salts to neutralize the fabric surface charge during home laundry.

Intense research in household cleaning offers more innovative cleaning solutions. Over the half of consumers worldwide favor functionality over “natural” and “multipurpose” claims in household care products. Due to rapid urbanization, emergence of small pack size, current environmental pressures and price escalation of petrochemical feedstock, the demand for sustainable laundry and dishwashing products is developing rapidly. The user-centered researches revealed that the increase in per capita income and wide range of choices, greatly influence consumers interactions with products as expenditure for household laundry and increase the number of sophisticated consumers. Dishwashing accounts for barely more than 0.5% of total per capita expenditure. Low energy as well as water consumption, high performance values are very important for the consumers when purchasing automatic washing appliances. Multi-usability and efficiency capture continuously the attention of the consumers in large scale in the sense of economic viability, environmental feasibility and reverted interest to use traditional liquid and powder detergents. Brand value and integrity proves to be also surprisingly important. Researches revealed that many consumers prefer household appliances with low water and energy consumption. As per the statistics, since half of the total surfactant consumption belongs to household applications particularly dishwashing and laundry washing, the natural product based surfactants produced from biomass are expected to continue to drive cleaning market.

The objective of this study is to investigate woman's practices and perceptions of using and handling of household cleaning products using qualitative and ergonomics methodology developed to reveal skills in daily life activities. A checklist and an open ended questionnaire were used in which the participants were observed and asked about the frequency of performing cleaning tasks, average monthly consumption of detergent, strategies employed for mixing products, various habits employed in cleaning, storage practices, strategies for personal protection and sharing the cleaning activities with family members. A non-probability sample of 228 volunteers, who were housewives, both employed and non-employed, with different levels of education were recruited for this study. Data were analyzed using SPSS software program. Results showed that children also contributed in domestic chores exposing themselves to chemicals. Women stated that they mixed different detergents together and over-consumed detergents. Contrasting results between the employed and non-employed women were found to be the duration of cleaning, the quantity of consumed laundry detergent and the measures of precautions and safety. The participants were consistently exposed to chemical detergents and minimal precautionary measures were taken. Cleanliness and hygiene have strong cultural values to women who prioritized those values over excessive exposure to chemicals.

Two series of cationic surfactants based on glycine molecule as sulfonate salt of N,N-diethyl glycine fatty esters having a hydrocarbon chain length of C 12 ,C 16 and C 18 followed by quaternerization with ethyl iodide were synthesized. Their chemical structures were confirmed using IR, 1 H-NMR, and mass spectroscopy. The surface activity of these amphiphiles has been determined by measurement of their surface tension. Parameters like surface tension (γ), critical micelle concentration (cmc), effectiveness (Π cmc ), efficiency (pC 20 ), maximum surface excess (Γ max ), minimum surface area (A min ) and Gibbs free energy of the micellization (ΔG mic ) and adsorption (ΔG ads ) have been determined from the measurements obtained by surface tension method. All these surfactants showed much lower CMC values compared to the similar hydrophobic chain length surfactant. All synthesized compounds have been evaluated for their biological activity against bacteria and fungi.

A series of novel dialkyl disulfonate Gemini surfactants (C n -GSBS, n = 8, 12, 14, 16, n is the carbon number of the hydrophobic chain) was synthesized from cyanuric chloride, aliphatic amine, ethylenediamine, N,N'-dimethyl-1,3-propyldiamine and sodium 2-chloroethanesulfonate. The chemical structures of the prepared compounds were confirmed by FT-IR and 1 H NMR. The critical micelle concentrations (CMC) in aqueous solutions at 25°C were determined by surface tension method. The CMC value decreased with increasing length of the carbon chain. The CMC reached a minimum as low as 5 × 10 −5 mol · L −1 for C 16 -GSBS. The interfacial tensions (IFT) between Daqing crude oil and C n -GSBS surfactant solutions were also measured. The effects of the concentration of Na 2 CO 3 , the concentration and carbon chain length of C n -GSBS on the IFT of crude oil-water were investigated in detail. The results show that, for the aqueous surfactant system containing the weak base Na 2 CO 3 , oil-water interfacial tension can be reduced to 10 −2 mN m −1 orders of magnitude. The results also indicate that with the increase of surfactant concentration and the chain length, the oil-water interfacial tension decreased markedly, which indicates that C n -GSBS surfactants have a good interface activity. These surfactants are good candidates for weak base-surfactant-polymer EOR process.