Solid Concentration In Suspension Research Articles

Effect of sediment size on bioleaching of heavy metals from contaminated sediments of Izmir Inner Bay

The effect of sediment size on metals bioleaching from bay sediments was investigated by using fine (< 45 μm), medium (45–300 μm), and coarse (300–2000 μm) size fractions of a sediment sample contaminated with Cr, Cu, Pb, and Zn. Chemical speciation of the metals in bulk and size fractions of sediment were studied before and after bioleaching. Microbial activity was provided with mixed cultures of Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans. The bioleaching process was carried out in flask experiments for 48 days, by using 5% (W/V) of solid concentration in suspension. Bioleaching was found to be efficient for the removal of selected heavy metals from every size fraction of sediments, where the experiments with the smaller particles resulted in the highest solubilization ratios. At the end of the experimental period, Cr, Cu, Pb and Zn were solubilized to the ratios of 68%, 88%, 72%, and 91% from the fine sediment, respectively. Higher removal efficiencies can be explained by the larger surface area provided by the smaller particles. The changes in the chemical forms of metals were determined and most of the metal releases were observed from the reducible and organic fractions independent from grain size. Higher concentrations were monitored in the residual fraction after bioleaching period, suggesting they are trapped in this fraction, and cannot be solubilized under natural conditions.

Grindability of Quartz in Stirred Media Mill

Nowadays, ultrafine grinding in the submicron particle size range is becoming an increasingly conventional process. One of the mostly used ultrafine grinding ways is the size reduction in the so called stirred media mill. This article deals with the experimental investigation of wet grinding of quartz in a stirred media mill. The applicability of the introduced operating Rittinger index and the lower limit size of Rittinger law are studied. Furthermore, the effect of solid concentration of suspension, ball filling ratio, circumferential speed of the stirrer, and size of grinding media on the fineness (median particle size and specific surface area) was examined. Additionally, a relative grindability calculated from the operating Rittinger index is introduced in order to compare the efficiency of stirred media milling. It was found that the grinding conditions greatly affect the applicability of Rittinger's law and its lower limit size.

Influence of mixing and solid concentration on sodium bicarbonate secondary nucleation rate in stirred tank

AbstractThis work aims to investigate the influence of the solid concentration in suspension on the contact secondary nucleation rate of sodium bicarbonate crystallization in a stirred tank crystallizer and to show the necessity of a local description of the mixing for a nucleation rate influence study. Experiments and computational fluid dynamics (CFD) simulations are realized. Crystallization kinetic parameters are extracted from experimental data using a mass distribution fitting approach. CFD and the experimental results allow identifying that a mixing property correlated with the measurements of the secondary nucleation rate in the stirred tank crystallizer appears to be the turbulent dissipation rate on the edge of the impeller. Its influence and the influence of the solid concentration in the suspension on the secondary nucleation rate are estimated by the evaluation of their exponents in a kinetic law. The obtained exponent values are then discussed qualitatively. (© 2010 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Quantitative in situ monitoring of citric acid phase transition in water using Raman spectroscopy

Citric acid exhibits two solid (anhydrous/monohydrate) phases in water. Below 34 °C, the more stable form being the monohydrate. This organic compound was selected as a model product to evaluate the continuous monitoring of solvent-mediated phase transition using in situ Raman spectroscopy. Specific calibration of the spectral data was developed at 15 °C for assessing in-line both the overall solid concentration in suspension (from 5% to 25%, w/w) and the composition of the solid phase (from 0% to 100% content of anhydrous). It is shown that, in addition to such key-measurements, supersaturation can also be computed in-line from the mass balance of the solute. In order to validate the technique, seeded phase transition experiments were performed at 15 °C and the kinetic process involved during the transition of anhydrous to monohydrate was successfully monitored. Both overall solid concentration and solid phase composition measurements were validated using off-line analytical methods (titration of solute concentration and DSC, respectively). The accuracy of the Raman measurements was found to be of the order of 5%.

In-line monitoring of partial and overall solid concentration during solvent-mediated phase transition using Raman spectroscopy

A calibration strategy for the continuous monitoring of solvent-mediated phase transition was developed using in situ Raman spectroscopy. Citric acid which exhibits enantiotropy during its anhydrous/monohydrate phase transition was selected as a model organic product. Using 25 samples in suspension, specific calibration of the spectral data was obtained for estimating in-line both the overall solid concentration in suspension and the composition of the solid phase. In addition to such key-measurements, reliable estimates of supersaturation were computed in-line from the mass balance of the solute. In order to validate the technique, anhydrous to monohydrate phase transition experiments were performed in suspensions at 15 °C and the kinetic process involved was monitored. Despite the use of various solid concentrations and reactor configurations, both the reproducibility and the reliability of the in situ Raman measurements are shown to be satisfactory.

Measurement of solid concentration in suspension using supersonic waves.

The relation between the solid volume fraction and the attenuation coefficient of supersonic waves in suspension of large particles was investigated. Experiments were performed on the gravity flow of two kinds of spherical polystylene pellets (0.406mm and 1.50mm) in a vertical pipe. The attenuation rate was measured for two frequencies of a supersonic wave (40kHz and 200kHz). The solid fraction was measured up to about 14%. It was found that the attenuation coefficient was proportional to the solid volume fraction in the range of measurements. In addition to the experiment, theoretical calculation was carried out, assuming the particles to be fixed rigid spheres. The calculated results compared well with the measurements.

Theoretical and experimental study of factors affecting capillary suction time (CST)

Factors affecting capillary suction time (CST) were studied theoretically and experimentally. The factors were elucidated from a linearly measured capillary suction time (LCST), which was obtained with a simpler device than conventional radial equipment. The LCST should be correlated with the specific resistance to filtration of sludge under the condition that a quantity, i.e. the product of specific resistance and cake mass deposited per unit filtrate volume, is greater than some critical value. If this quantity is greater than the critical value, the LCST is not always correlated with the filterability, but the LCST can always be correlated well with the solid concentration of suspension.