Surface area/mass

The mode of distribution is simply the value of the most frequent size present. A distribution exhibiting a single maximum is referred to as a unimodal distribution. When two or more maxima are present, the distribution is caUed bimodal, trimodal, and so on. The mode representing a particle population may have different values depending on whether the measurement is carried out on the basis of particle length, surface area, mass, or volume, or whether the data are represented ia terms of the diameter or log (diameter). 

A first-order irreversible catalytic reaction r" = k"C/ ) occurs in a slurry reactor (or fluidized bed reactor). Spherical catalyst particles have diameter R, density surface area/mass Sg, and a fraction g of the reactor is occupied by catalyst. The average pore diameter is d. Find an expression for r C ) in terms of these quantities. 

Nanomaterials may in their own right possess novel and useful properties or as a composite of the same or different materials to form larger useful structures. Safety consideration is therefore of paramount importance since completely inert materials have the ability to exhibit toxic effects by virtue of a reduction in their size and associated increase in surface area-mass ratio, let alone materials manipulated specifically to impart novel properties. 

Colloidal particles are also characterized by a large surface area/mass ratio (called specific surface), and by a strong surface charge that favors adsorption. For example, montmorillonite clays and some organic colloids may have specific surfaces of up to 800 m2/g. 

Catalyst surface area/mass of catalyst bed a = 60 cmVg cat. 

The drying kinetics (rate of drying, and hence required drying time) also depend strongly on solids properties, particulany particle size and porosiW. The surface area/mass ratio and the internal pore structure control the extent to which an operation is diffusion-limited, i.e., diffusion into and out of the pores of a given solids particle, not through the voids among separate particles. 

If sufficient growth has taken place that change in surface area/mass should be taken... 

The initial grow rate, which represents the productivity of the initial seed before reduction in surface area/mass, may be particularly useful if that seed is to be used in a scaled-up operation ... 

Colloidal particles interact strongly with the fluid, but the individual particles have some structural integrity, so they cannot be said to dissolve homogeneously. The colloidal mixture behaves so distinctively because of the latge surface area of interaction between the particles and water or air. The ions at the boundary interact with the ions and molecules of both phases. This is true at any surface or phase boundary, but the interaction of colloidal phases is large because their surface areas are so large. A 1-mm sand particle has a surface area/mass ratio of about 0.002 m2g-1 a -fixa clay particle, 2 m2g 1 and a 1-nm particle, 2000 m2g 1. 

What is the mass of each of the above size particles The specific gravity of aluminosilicates is 2.65. Calculate the surface area/mass ratios of the above cubes, assuming that they are aluminosilicates. 

Particulate size data reported for numerous particulate systems in natural waters can be modeled accurately with a two-parameter power law, given by dN/dl = AV. The exponent of the power law, p, has been shown to be a useful estimator of the relative contribution of particulate size classes to the total number, surface area, mass and volume concentration, and extinction coeflBcient of the particulate fraction. Reported values of p range from 1.8 to 4.5 in low ionic-strength solutions. 

When carrying out a gas-liquid reaction, the gas may be dispersed in the liquid, as in bubble-column reactors or stirred tanks, or the gas phase may be continuous, as in spray contactors or trickle-bed reactors. The fundamental kinetics are independent of the reactor type, but the reaction rate per unit volume and the selectivity may differ because of differences in surface area, mass transfer coefficient, and extent of mixing. In the following sections, gas holdup and mass transfer correlations and other performance data for gas liquid reactors are reviewed and some problems of scaleup are discussed. 

It follows that individual measuring methods depend upon particle definition. Particle definitions might include such details as number, length, surface area, mass, and volume, as a result of which one has the choice of using various counting methods - microscopy, image analyzers, laser diffraction, as well as sieving and air classification methods. 

As discussed in Maynard and Aitken (2007), different situations will require different material attributes—whether surface area, mass, or particle number concentration—to be measured the paper recommends measuring all three where possible. The idea of a universal aerosol sampler enabling the collection of personal exposure to all three of these metrics is explored in this paper and in the Nature paper on the safe handling of nanotechnology written by 13 distinguished nanotechnology experts (Maynard et al., 2006). 

Many modem processes involve the formation of emulsions to create a high (surface area/mass) ratio and thereby produce fast kinetics which results in a high production rate. 

Foams are widely used in iron- and steelmaking process since they provide rapid refining of the metal droplets held in the foam as a result of the enormous (surface area/mass) ratio. Foaming slags are also used on Electric Furnaces (EAPO to stabilise the arc and improve energy efficiency. 

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