Comprehensive Stoichiometric Studies on the Reaction of Silicon in HF/HNO3 and HF/HNO3/H2SiF6 Mixtures

The stoichiometry of the wet chemical etching of silicon in concentrated binary and ternary mixtures of HF, HNO3 and H2SiF6 was comprehensively investigated. A complete quantification of both dissolved and...

Prediction of Aqueous Solution Surface Tension of Some Surfactant Mixtures and Composition of Their Monolayers at the Solution–Air Interface

Measurements of the surface tension of the aqueous solution of SDDS mixture with fluorocarbon surfactants (FC) were carried out and considered in light of the surface tension of aqueous solutions of individual surfactants. Similar analyses were made for many other aqueous solutions of binary and ternary mixtures, taking into account the literature data of the surface tension of aqueous solutions of TX100, TX114, TX165, SDDS, SDS, CTAB, CPyB and FC. The possibility of predicting the surface tension of the aqueous solution of many surfactant mixtures from that of the mixture components using both the Szyszkowski, Fainerman and Miller and Joos concepts was analyzed. The surface tension of the aqueous solutions of surfactant mixtures was also considered based on the particular mixture component contribution to the water surface tension reduction. As a result, the composition of the mixed surface layer at the solution–air interface was discussed and compared to that which was determined using the Hua and Rosen concept. As follows from considerations, the surface tension of the aqueous solution of binary and ternary surfactant mixtures can be described and/or predicted.

The Feasibility of Binary and Ternary Hydrate Mixtures of CH4, CO2 and C3H8 for Metals Removal

The selection of suitable hydrate formers and their respective gas composition for high hydrate formation driving force is critical to achieve high water recovery and metals removal efficiency in the hydrate-based desalination process. This study presents a feasibility analysis on the possible driving force and subcooling temperatures for the binary and ternary mixtures of methane, carbon dioxide, and propane for hydrates-based desalination process. The driving force and subcooling of the gas systems was evaluated by predicting their hydrate formation phase boundary conditions in 2 wt.% NaCl systems at pressures ranges from 2.0 - 4.0 MPa and temperatures of 1 – 4°C using Modified Peng-Robinson Equation of State in the PVTSim software package. The results suggested that the driving force of CH4-C3H8 and CO2+C3H8 binary systems are similar to their ternary. Thus, the use of binary systems is preferable and simpler than the ternary systems. For binary gas composition CO2+C3H8 (70:30) exhibited a higher subcooling temperature of 8.07 ºC and driving force of 1.49 MPa in presence of 2wt% salt. In case of ternary system (CH4-C3H8-CO2) composition of (10:80:10) provided a good subcooling temperature of 12.86 ºC for hydrate formation. The results favour CO2-C3H8 as preferred hydrate formers for hydrate- based desalination. This is attributed due to the formation of sII structure and as it constitutes 136 water molecules which signifies a huge potential of producing more quantity of treated water.

Phase Behavior of Selected Condensed Double-Decker Shaped Silsesquioxane Compounds

Bisfunctional dichlorosilanes were reacted with tetrasilanol of double-decker shaped octaphenylsilsesquioxane (DDSQ) to form fully condensed DDSQ compounds. The crystallographic and thermal characteristics of these compounds were examined. For compounds capped with dichlorosilanes bearing linear aliphatic moieties, as the number of carbon increases from methyl to n-butyl (from 1 to 4) the melting temperature, Tm, dropped from 546 K to 416 K. While for compounds capped with cycloaliphatic, as the moiety changes from cyclopentyl to cyclohexyl, the value of Tm increases from 533 K to 555 K. Surprising, the highest Tm observed was that when capping was done using diisopropyl dichlorosilane. A Tm of around 565 K was observed, which was even higher as compare to diphenyl dichlorosilane capped DDSQ, which had Tm of about 526 K. Phase behavior of binary and ternary mixtures of these condensed DDSQ was also investigated. To our surprise, mixtures of these compounds form eutectic. The eutectic points were calculated based on ideal binary and ternary eutectic from the thermal properties of pure components. Depending on the crystallography, experimental observations of eutectic match well with calculated values.