Fluorescence drainage profiles of thin liquid films.
Fluorescence drainage-profiles of thin liquid films formed from Rhodamine solutions containing anionic, cationic and non-ionic surfactants have been investigated. It is found that the influence of system variables such as electrolyte concentration, dye concentration, film environment and solution viscosity can be evaluated by means of the profiles. The addition of sodium chloride leads to the expansion (non-ionic surfactant), or contraction (anionic surfactant) of the profiles. In the case of the cationic surfactant, it reduces the number of fringes in the profiles. The height of selected fringes changes linearly with dye concentration, and no fringes are observed when the films are submerged in non-polar solvents. The influence of solution viscosity on film thickness and drainage rate is demonstrated by the number and frequency of fringes in the profile. The formation of first and second "black films" from solutions containing varying concentrations of sodium chloride can be shown.
Stability and some properties of the second black film
The conditions under which the two black films—the first of greater and variable thickness and the second of about 44 A—are formed by solutions of sodium dodecyl sulphate in the presence of NaCl are established and the effect of several additives upon the relative stability of these two films is investigated. Specific effects of counterions upon this behaviour are marked and are interpreted in terms of an ionic size effect upon the structure of the second black film and of preferential surface adsorption. Some conclusions about the composition and heat of formation of the second black film are drawn using Le Chatelier's principle. At higher ionic strengths counterions have also specific effects upon the thickness of the first black film in line with their hydrated size and adsorption.
Heavy metal adsorption from industrial wastewater by PAMAM/TiO2 nanohybrid: Preparation, characterization and adsorption studies
Abstract This study investigates the removal of heavy metals from industrial wastewater using TiO 2 nanoparticles modified with poly-amidoamine dendrimer (PAMAM, G 4 ). The metal ions Cu 2 + , Pb 2 + , and Cd 2 + were selected as model pollutants. FTIR, SEM, BET surface area and Zeta potential measurements, and Dispersion Observing methods have been employed for characterizing the synthetic nanohybrid and these techniques indicated that the PAMAM loaded on to TiO 2 have been favorably synthesized. The effects of several parameters including initial metal ion concentration, temperature, pH solution, the nanohybrid dosage and contact time were studied. The experimental data were analyzed using equilibrium isotherm and kinetics models. The adsorption process was studied using isotherm, kinetics, and thermodynamics models. The analysis shows that the Langmuir isotherm and pseudo-second-order kinetics are appropriate models for the adsorption process. The thermodynamic parameters illustrate that the absorption is endothermic and spontaneous. The findings suggest that the nanohybrid is a good super absorbent for the removal of heavy metals from industrial effluents.