Polymer conditioning of alum sludge and discrepancies between estimates of the optimum dosage

The paper outlines the effects of polymer conditioning on alum sludge properties, such as floc size, density, fractal dimension (DF) and rheological properties. Experimental results demonstrate that polymer conditioning of alum sludge leads to: larger floc size with a plateau reached in higher doses; higher densities associated with higher doses; increased degree of compactness; and an initial decrease followed by an increase of supernatant viscosity with continued increase in polymer dose. The secondary focus of this paper dwells on a comparison of the estimates of optimum dose using different criteria that emanate from established dewatering tests such as CST, SRF, liquid phase viscosity and modified SRF as well as a simple settlement test in terms of CML30. Alum sludge was derived from a water works treating coloured, low-turbidity raw waters.

Speeds of sound, isentropic compressibilities, and excess molar volumes of cycloalkanes, alkanes and aromatic hydrocarbons at 303.15 K. II. Results for cycloalkanes+aromatic hydrocarbons

The speeds of sound u, isentropic compressibilities ?S, molar sound functions R, excess isentropic compressibilities ?SE and excess molar volumes VE for eight binary mixtures of cyclopentane, cyclohexane, cyclooctane and methylcyclohexane with benzene and of cyclohexane with toluene, ethyl benzene, p-xylene and propyl benzene at 303.15 K are reported. The effects of molecular sizes and shapes of the component molecules and of interaction energy in the mixture have been discussed. The Prigogine–Flory–Patterson theory has been applied to analyze the present binary mixtures along with the mixtures of cis- and trans-decalins with benzene and toluene taken from the literature.

Speeds of sound, isentropic compressibilities, viscosities, and excess molar volumes of binary mixtures of alkanoates with tetra- and trichloromethanes at 303.15 K

Speeds of sound u, isentropic compressibilities ?S, viscosities ?, excess isentropic compressibilities ?SE, excess molar volumes VE, viscosity deviations ??, and excess Gibbs energies of activation ?G*E of viscous flow have been investigated for six binary mixtures of diethyl malonate, diethyl bromomalonate, and ethyl chloroacetate with tetra- and trichloromethane at 303.15 K. The values of ?SE, VE, ??, and ?G*E are highly dependent on the type of components involved and the composition curves are unsymmetrical. The results obtained for viscosity of binary mixtures were used to test the semi-empirical relations of Grunberg-Nissan, Tamura-Kurata, Hind-McLaughlin-Ubbelohde, Katti-Chaudhri, McAllister, Heric-Brewer and Auslaender. The experimental speeds of sound have been analyzed in terms of collision factor theory and free length theory of solutions.

Selective catalytic reduction of O-2 with excess H-2 in the presence of C2H4 or C3H6

The selective reduction of molecular oxygen with excess H-2 in the presence of alkenes was achieved successfully for the first time: silver supported on alumina catalysts exhibited full conversion of O-2 at temperature as low as 50 degrees C, while the conversion of ethene or propene remained essentially zero up to 250 degrees C.