Volume 49, Issue 2

The modification of the manual direct two-phase titration method for anionic surface active agent determination is presented. The purpose was to find such organic solvent which can replace solvents applied in the method i. e. chloroform or dichloromethane since both are harmful, exhibiting carcinogenic, mutagenic and, embryotoxic properties. As a new solvent 1-butanol or isobutyl alcohol was used. The reaction in the examined alcohols caused to be acidic during the titration process. Thus the solvatochromic dye (1) i. e. 5-(3-bromo-4-hydroxy-5-methoxyphenyl)-7,7-dimethyl-7H-indolo[1,2-a]quinolinium perchlorate has been replaced with 1-phenyl-2-[2-(3-nitro-4-hydroxy-5-methoxyphenyl)ethenyl]-3,3-dimethyl-3H-indolium perchlorate (2). The pK a (3.51) of (2) facilitates its dissociation, and has the same color change at the titration endpoint. The modified method was tested on three different concentrations of sodium dodecyl sulfate solution, and the results are in good agreement with the real ones.

Removal of Pb(II) ion from aqueous solution on modified sawdust obtained from Morus alba was investigated. The sample was characterized by BET surface area, EDX, FTIR and Zeta potential technique. The surface contains carbonyl and hydroxyl functional groups which act as binding sites for Pb(II) ion. Adsorption kinetics of Pb(II) on sawdust was tested by pseudo first order, Elovich and parabolic diffusion kinetic equations. The adsorption data were found to fit to Freundlich, Langmuir and Tempkin isotherms. The rate of adsorption was high at high temperature. Thermodynamic parameters like ΔH, ΔS and ΔG were calculated from the kinetic data. The positive values of ΔS reflect some structural exchange among the active site of the adsorbent and metal ion. The negative values of Gibbs free energy (ΔG) show the spontaneous nature of the process.

Carbon prepared from Turkish coffee residue was used to remove crystal violet dye from aqueous solutions. The adsorbent was characterized by surface analyzer, infra red (IR) spectroscopy, Boehm titration and mass titration. Adsorption was studied as a function of pH, dye concentration and contact time. Pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to describe the kinetic data. The adsorption of crystal violet dye on prepared adsorbent followed pseudo second order kinetic model rather than pseudo first order kinetic model. The adsorption equilibrium data were analyzed using the Langmuir, Freundlich and Temkin isotherms model. The pH of the solution affects the adsorption capacity of the adsorbent. An increase in the adsorption capacity of the dye was observed with increase in pH. However, this was up to pH 6.5. The increase was insignificant from pH 6.5 to 10. The desorption experiments showed the possibility of regeneration of the adsorbent. Equilibrium was attained within 4 hour for 30 mg L −1 of dye concentration, while for 25 mg L 1 and 15 mg L −1 it was less than 4 hour.

Four polyoxyethylenated pentaerythritol (PE) ester surfactants have been synthesized. The molecular weights of these surfactants were calculated and evaluated experimentally by GPC and confirmed by calculations based on 1H-NMR . Also, their HLB values were calculated by Griffin formula. The surface tension and thermodynamic properties of the surfactants were obtained from surface tension measurements at different temperatures (298 – 318 K). It was found that the minimum area/surfactant molecule (A min ) for the investigated surfactants increased with increasing the molecular weight of the incorporated ethylene oxide. The thermodynamic parameters of micellization (ΔG mic , ΔH mic and ΔS mic ) and that for adsorption (ΔG ad , ΔH ad and ΔS ad ) were also calculated. The more negative Gibbs free energy of adsorption values than those of micellization suggest that these surfactants favor adsorption than micellization. This finding is utilized for monitoring their dispersancy power. It was found that the water solubility of the prepared surfactants is correlated to their HLB values. Furthermore, the biodegradability of the prepared compounds was studied at different conditions in order to investigate their usability as oil spill dispersants. The data revealed that PE200-C12 had maximum dispersion efficiency and it was completely biodegraded after 8 days.

LogP values for several nonionic surfactants were measured by the slow stirring/surface tension method. Aqueous surfactant solution is equilibrated with octanol. A surface tension technique is used to determine the concentration in the aqueous phase. Interference from octanol, which is surface active, is prevented by evaporation and re-dissolution of the sample. The effect of initial concentration on the observed logP value is discussed. Above a certain concentration the amount of surfactant in the aqueous phase exceeds the critical micelle concentration (cmc). In this region logP appears to decrease markedly with initial concentration. Using a simple model, which includes the effect of octanol on the cmc, the apparent logP can be corrected for this micellisation effect. With a tristyrylphenol ethoxylate the concentrations in aqueous and octanol phases were determined by UV absorption, giving a logP value in good agreement with the surface tension method. For a series of commercial undecyl ethoxylates, the logP value was found to decrease with increasing length of the EO chain. Products with more than 4 EO have a logP less than 3, indicating that they are unlikely to bioaccumulate.

Adsorption of different n-alkyl alcohols (hexanol, pentanol, butanol, propanol, ethanol and methanol) out of aqueous media by polyurethane foam, an insulation waste powder, (PUF) was investigated using batch system under controlled conditions. Kinetic data followed more closely to the pseudo-first-order model. The adsorption rate and the related parameters, such as the PUF dosage, n-alkyl alcohol initial concentration, pH, temperature, and ionic strength were studied. The saturation equilibrium was also studied as a function of the related parameters (PUF dose, alcohol initial concentration, temperature, pH and ionic strength). The adsorption isotherm was established for the adsorption of different alcohols on PUF. Linearized Langmuir, Freundlich and Frumkin models were applied to estimate the adsorption constants. It was estimated that the adsorption rate is positively affected by increasing PUF dose, adsorbent concentration, acidity and temperature. The adsorption equilibrium was shifted toward higher adsorption capacity by increasing the PUF dose, substrate concentration, temperature and acidity in the order of: n-hexanol > n-pentanol > n-butanol > n-propanol > ethanol > methanol. It was not affected by ionic strength. The adsorption data fit to Freundlich, Langmuir and Frumkin models, but attained a better correlation to models in the order of as Langmuir > Freundlich > Frumkin. In addition to the Freundlich, Langmuir und Frumkin constants the thermodynamic parameters of activation and adsorption were determined.

Aqueous solutions of commercially available Pluronic®R i. e. triblock copolymer composed of polypropylene oxide(PPO)-polyethylene oxide(PEO)-polypropylene oxide(PPO), (code named 25R4, BASF) in the presence of surfactant additives viz. hydrotropes (NaTS, NaXS), anionics (SDS, SDBS) and cationics (DTAB, CTAB) were investigated by cloud point(CP), surface tension and conductance techniques. All the techniques clearly indicated that Pluronic®25R4 interacts strongly with anionic surfactants but weakly with cationic surfactants. Surfactant additives used here, produced a marked increase in the CP of the copolymer. Elevation in CP is attributed to the solubility of PPO block of the copolymer and formation of Pluronic-surfactant complex. The effect of NaCl salt on the CP of Pluronic®25R4 at added SDS and CTAB was also studied and it was decreased due to the screening effect. At the presence of 25R4 in its non-associated form, the surface tension and conductance data is discussed with binding process and indicated strong interaction of Pluronic®25R4 with SDS, showing two break points (P 1 and P 2 ) in the plot and very weak interaction with CTAB observing single break point.

The spontaneous vesicle formation from a novel bulky tetrasiloxane-tailed dicephalic surfactant composed of a carbohydrate and ethylene glycol ethyl ether was reported. The surface tension measurements revealed that aggregates are formed, and dynamic light scattering (DLS) measurements suggested the aggregates are vesicles. The size and morphology were observed by transmission electron microscopy (TEM). The vesicle formation was further confirmed by dye entrapment studies.

A new tetrasiloxane-tailed dicephalic surfactant was synthesized. The structures of intermediate and product were confirmed by infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy. Surface activity and wetting ability of the surfactant were also investigated. The results show that the prepared surfactant exhibited excellent surface activity reducing the equilibrium surface tension of water to a minimum value of approximate 21.8 mN · m −1 .

A series of sulfoethyl locust bean gum derivatives with a degree of substitution (DS) ranging from 0.05 to 0.33 was prepared by etherification of locust bean gum with vinylsulfonic acid sodium salt in alkaline 2-propanol suspension. The derivatives were characterized by means of FT-IR and elemental analysis, and evaluated for laundry anti-redeposition performance, alone and in systems with mannanase and/or cellulase enzymes. Optimum anti-redeposition performance was observed at degrees of substitution of around 0.15. Mannanase was found to have a negative effect on sulfoethyl locust bean gum derivatives' performance although a system comprising sulfoethyl locust bean gum derivative and cellulase was found to be complementary.

Three series of surfactants with different amino acid moieties (glycine, glutamic acid and lysine) were synthesized with octanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid and glycine, glutamic acid, lysine respectively. The reaction conditions and their properties including surface activity, emulsibility and foamability were studied. For the surfactants with glycine moiety and glutamic acid moiety respectively, cmc (critical micelle concentration) and γ cmc (surface tension at cmc) decreased and surface activity enhanced as the length of carbon chain increased. The surfactants with glycine moiety exhibited the best emulsibility and foamability in the three series. The surfactants with glutamic acid moiety showed disappointing emulsibility, but their foamability was good. The surfactants with lysine moiety did not display favorable emulsibility and foamability due to the length of their double-chain.

The long reaction time and low conversion of the existing technologies in indirect synthesis of disodium mono-fatty alcohol citrate constrain their industrialized application. Here, we developed a new technology and synthesized a series of monoester of citric acid salts different carbon atoms in hydrophobic group. The structures of intermediate and products were defined by infrared spectra and hydrogen nuclear magnetic resonance spectra. Their physico-chemical properties were systematically studied for the first time, including equilibrium surface tension, wetting ability, emulsification stability and foaming behavior in aqueous solution. The results show that ifs the number of carbon atoms in the hydrophobic group increases, the critical micelle concentration (CMC) decreases, wetting ability weakens, the foaming volume in hard water increases and emulsification stability for liquid paraffin and bean oil increases, but opposite for oil acid.