Turbidity particle size distribution

When a beam of light is intercepted by a turbid medium, part of the incident light is absorbed, part is directly reflected, and part is scattered. The attentuation produced is a function of the concn, particle size distribution and color of the suspension... 

In order to calculate particle size distributions in the adsorption regime and also to determine the relative effects of wavelength on the extinction cross section and imaginary refractive index of the particles, a series of turbidity meas irements were made on the polystyrene standards using a variable wavelength UV detector. More detailed discussions are presented elsewhere (23) > shown here is a brief summary of some of the major results and conclusions. 

The other state variables are the fugacity of dissolved methane in the bulk of the liquid water phase (fb) and the zero, first and second moment of the particle size distribution (p0, Pi, l )- The initial value for the fugacity, fb° is equal to the three phase equilibrium fugacity feq. The initial number of particles, p , or nuclei initially formed was calculated from a mass balance of the amount of gas consumed at the turbidity point. The explanation of the other variables and parameters as well as the initial conditions are described in detail in the reference. The equations are given to illustrate the nature of this parameter estimation problem with five ODEs, one kinetic parameter (K ) and only one measured state variable. 

Figure 14 Particle size distribution of a ten-component mixture of narrow polystyrene dispersions. Left intensity measured as function of t with a turbidity detector. Right integral and differential particle size distribution. Reproduced from Machtle [84] by permission of The Royal Society of Chemistry. 

Applications of optical methods to study dilute colloidal dispersions subject to flow were pioneered by Mason and coworkers. These authors used simple turbidity measurements to follow the orientation dynamics of ellipsoidal particles during transient shear flow experiments [175,176], In addition, the superposition of shear and electric fields were studied. The goal of this work was to verify the predictions of theories predicting the orientation distributions of prolate and oblate particles, such as that discussed in section 7.2.I.2. This simple technique clearly demonstrated the phenomena of particle rotations within Jeffery orbits, as well as the effects of Brownian motion and particle size distributions. The method employed a parallel plate flow cell with the light sent down the velocity gradient axis. 

D < 500 pm, Fraunhofer Diffraction Pattern Analysis (FDPA) can be employed in measuring particle size distributions (4,5). For the particles in the intermediate range, 0.7 pm < D < 10 pm, Mie theory of scattering holds and Turbidity Spectra (TS) can furnish information about particle sizes (6). 

For polydisperse systems, replacement of equation 13 into equation 2 for every particle diameter, yields an approximation to the turbidity in terms of ratios of moments of the particle size distribution without having to make assumptions regarding the shape of the distribution ... 

The overall conclusion from the analysis of equation 18 over the complete domain of a is that, in principle, information about the shape of the particle size distribution can be obtained directly from turbidity, or in general, from scattering measurements. However, the discriminating power of the measurements in terms of the particle size distribution depends upon the wavelength range selected for the analysis. The major difficulty in the interpretation of the data arises from the behavior of the extinction itself as function of the size parameter which causes the measurements "see" a different average at every wavelength. 

Measuring Particle Size Distribution of Latex Particles in the Submicrometer Range Using Size-Exclusion Chromatography and Turbidity Spectra... 

Therefore, in principle, the parameters of the particle size distribution can be estimated from specific turbidity measurements at different wavelengths. This is not true, however, in the Rayleigh regime (i.e. small particles, (D/Am) less than 0.1). In this case, the extinction coefficient is proportional to (D/Am)4 and... 

SEC has been shown (7) to give satisfactory results for latexes with broad particle size distributions as well. The method is particularly useful (7) in the determination of distributions of small particles when specific turbidity would provide only a turbidity (or weight) average diameter. 

Wavelength, turbidity measurements, effect on particle size distributions, 172-174 Weight distributions... 

Turbidity has been widely used for determining the particle size distribution (PSD) of particles in suspension, since it is experimentally simple, can be used over a wide size range and does not disturb the system under investigation. It is also fast, reproducible and inexpensive. 

Zollars [52] described an on-line turbidity system for the estimation of particle size distribution, refractive index and solids concentration. In a review and simulation of turbidimetric methods of on-line analysis Brandolin and Garcia-Rubio [53] state that this method is suitable only for... 

Crawley et. al. [57] applied the above equations to determine particle size distributions from turbidity measurements. The problems arise in finding a particle size distribution from the measured extinction coefficient due to the ill-defined inversion problem. Scholtz et.al. [58] focused on the problem of analyzing spectra of colloidal solutions, for which the size distribution was known from other methods like electron microscopy and light scattering they termed this transmission spectroscopy. ... 

Transient turbidity is an optical technique for measuring the size of magnetic particles [63,64], It does this by aligning particles in an electric field, removing the field, and following their return to random orientation induced by Brownian motion. Their relaxation is measured by turbidity and this can be related to particle size distribution if assumptions are made... 

Water Treatment Very significant effects of particle size distributions on the performance of water treatment processes have been proposed by Lawler et al. (1980). Particle mass or other parameters related to particle mass (turbidity) are important means to characterize the performance of solids separation processes. If particulate volume and particulate density are known, the relation between particle size and particle mass can be established. Assuming spherical particulates and a constant density, this relation can easily be derived. 

Kinetic measurements are changing from macroscopic to microscopic scales. Initially, kinetics consisted of macroscopic measurements of the fluid phases associated with hydrates - such as gas consumption rates or liquid turbidity, fundamentally in Bishnoi s laboratory.Subsequently, mesoscopic measurements of hydrate cry-stais, -82 particle size distribution, and film growth rates are available. Microscopic kinetic hydrate phase measurements are emerging. A review of microscopic hydrate science for both kinetics and thermodynamics is presented by... 

Precipitate detection methods typically use light scattering techniques such as nephelometry, flow cytometry, and turbidity measurements to determine the amount of the precipitate formed during the incubation process. A major advantage with these types of techniques is the availability of particle size distribution and aggregation information. 

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