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Kinetic and equilibrium studies on adsorption of Reactive Blue 19 dye from aqueous solutions by nanohydroxyapatite adsorbent

Ciobanu G., Barna S., Harja M.

Archives of Environmental Protection

2016

Vol. 42, no. 2

3--11

In the present study the adsorption of Reactive Blue 19 dye on the hydroxyapatite (HAp) nanopowders was investigated. The batch adsorption experiments were performed by monitoring the adsorbent dosage, contact time, dye solution concentration, pH and temperature. At pH 3 and 20ºC, high dye removal rates of about 95.58% and 86.95% for the uncalcined and calcined nanohydroxyapatites, respectively, were obtained. The kinetic studies indicated the dye adsorption onto nanohydroxyapatite samples to follow a pseudo-second order model. The Langmuir isotherm was found to be the best to represent the equilibrium with experimental data. The maximum adsorption capacity of uncalcined and calcined nanohydroxyapatite samples has been found to be 90.09 mg/g and 74.97 mg/g, respectively.

Behaviour of short polymer-high strength concrete columns under eccentric compression

Barbuta M., Toma I. O., Harja M., Toma A. M., Gavriloaia C.

Archives of Civil and Mechanical Engineering

2013

Vol. 13, no. 1

119--127

Engineers have been looking for ways to combine two or more materials in order to take advantage of their strong features. This is how the hybrid materials were born. A very common type of such a construction material is the reinforced concrete. The present paper presents the results of the experimental and numerical investigations of the behaviour of short hybrid concrete columns subjected to short-time eccentric compression. The columns are made of high strength concrete, in the compression part, and polymer concrete located in the tensioned part. At the age of 28 days the columns were subjected to eccentric compression, with constant eccentricity. The influence of the second order effects, such as creep, was neglected. From the experimental results it can be concluded that the type of reinforcement can have a significant effect on the ultimate carrying capacity of the hybrid columns. The numerical simulations by means of non-linear finite element analysis are in good agreement with the experimental results.