Leaching kinetics of colemanite by aqueous EDTA solutions

The dissolution kinetics of colemanite, a boron-containing mineral, in aqueous disodium EDTA solutions were studied. The effects of concentration and pH of the solution, particle size, and temperature were examined. A decrease in pH and particle size increased the dissolution rate, while an increase in the concentration of the solution and temperature increased the rate. The activation energy and pre-exponential factor were calculated as 50.6 kJ mol-1 and 5.14 x 10(7) m s-1, respectively

Crystallization of silver nitrate from saturated silver nitrate solution in nitric acid

112-119The aim of the present work is to submit an investigation on the optimum conditions of crystallization of silver nitrate salt from saturated silver nitrate solution in nitric acid. The saturated solutions of AgNO3 at 70°C obtained by evaporation of dilute silver nitrate solutions with nitric acid were crystallyzied in a jacketed glass vessel with controlled cooling. The parameters for the crystallization operation were chosen as stirring speed and crystallization period. For each experiment, crystals obtained from operations were filtered, washed, dried, and their photographs were taken before particle size analysis. The differential and cumulative analysis and product yield calculations showed that the optimum values of the parameter for the crystallization of silver nitrate salt from saturated silver nitrate solutions with nitric acid were determined as 500 rpm stirring speed and 240 min crystallization period, with the highest yield

Boron removal from geothermal waters by electrocoagulation

Most of the geothermal waters in Turkey contain extremely high concentration of boron when they are used for irrigation. The use of geothermal waters for irrigation can results in excess amount deposition of boron in soil. On the other hand, a minimal boron concentration is required for irrigational waters. In this study, electrocoagulation (EC) was selected as a treatment process for the removal of boron from thermal waters obtained from Ihca-Erzurum in Turkey. Current density (CD), pH of solution and temperature of solution were selected as operational parameters. The results showed that boron removal efficiency increased from pH 4.0 to 8.0 and decreased at pH 10.0. Although boron removal efficiency was highest at pH 8.0, energy consumption was very high at this pH value compared to other pH intervals. Boron removal efficiency reached to 95% with increasing current density from 1.5 to 6.0 mA/cm(2), but energy consumption was also increased in this interval. At higher temperatures of solution, such as 313 and 333 K, boron removal efficiency increased. At optimum conditions, boron removal efficiency in geothermal water reached up to 95%. (c) 2007 Elsevier B.V. All rights reserved

Boron removal by means of chemical precipitation with calcium hydroxide and calcium borate formation

Boron removal was investigated by chemical precipitation from aqueous solutions containing boron using calcium hydroxide. pH, initial boron concentration, amount of Ca(OH)(2), stirring speed and solution temperature were selected as operational parameters in a batch system. The highest boron removal efficiency was reached at pH 1.0. Increasing initial boron concentration and amount of calcium hydroxide raised to boron removal efficiency. Boron removal efficiency was highest at a stirring speed of 150 rpm. The most important parameter affecting boron removal efficiency was solution temperature. Increasing solution temperature increased importantly boron removal. XRD analysis showed that CaB3O3(OH)(5)center dot 4H(2)O, which is a borate mineral called inyoite, occurred between Ca(OH)(2) and borate ions. As a result of the obtained experimental data, when the optimum operational conditions were selected, over 96% of boron removal efficiency was reached by this method

Right Ventricular Functions in Patients Undergone Balloon Valvuloplasty for Isolated Pulmonary Valve Stenosis

Objective: Isolated pulmonary valve stenosis is the most common cause of the right ventricular outflow tract obstruction, and balloon valvuloplasty (BVP) has been the treatment of choice in these subgroup of patients. In this study, we aimed to evaluate right ventricular functions of patients who underwent BVP for PS using two-dimensional, pulse wave (PW) Doppler and tissue Doppler echocardiography during an average of 4 years (2 months-11 years) of follow-up period