Limiting current technique

Richard S. H. Mah and Mordechai Shacham, Pipeline Network Design and Synthesis J. Robert Selman and Charles W. Tobias, Mass-Transfer Measurements by the Limiting-Current Technique... 

MASS-TRANSFER MEASUREMENTS BY THE LIMITING-CURRENT TECHNIQUE... 

Electrochemical measurements of mass-transfer rates by the limiting-current technique have been employed with increasing frequency in the last 20 years. This chapter offers a discussion of the underlying principles, conditions of validity, and selected applications. 

Since current can be measured with ease and precision, the limiting-current technique provides a convenient and, under certain conditions, accurate method for measuring mass-transfer rates. The conditions for valid measurement and correct interpretation of limiting currents are discussed in the following sections. 

In this chapter the theory and practice of limiting-current technique for the measurement of mass-transport coefficients have been described. The selective discussion and tabular compilation of results of investigations that used limiting-current measurements should be indicative of the widespread use of this relatively novel method. 

By providing a better understanding of the method, this chapter is intended to inspire more precise and more widespread use of the limiting-current technique in studies of transport phenomena. 

In addition to time-of-flight techniques, other methods based on current measurements have been described. Space-charge-limited current techniques have been reported by Lampert and Mark (1970), Mort and Emerald (1974), Nespurek and Silinsh (1976), Sworakowski and Nespurek (1979), Silinsh... 

Hall, D.W., Scott, K., and Jachuck, R.J.J. (2001), Determination of mass transfer coefficient of a cross-corrugated membrane reactor by the limiting-current technique, International Journal of Heat and Mass Transfer, 44(12) 2201-2207. 

It is essential for modelling purposes to be able to obtain numerical values of a mass transfer coefficient that can be introduced in the equations derived in Chapter 3. We shall first discuss methods of obtaining values of by calculation and then in Section 2.3.4 give an account of the limiting current technique for obtaining experimentally. 

A commercially available cell " uses this type of particulate turbulence promoter in the form of a fluidized bed of electrochemically inert particles, typically glass spheres. This Chemelec cell is aimed at the secondary recovery of metals and their removal from effluents. Little reliable information is available on mass transfer to spheres in a fluidized bed. Nassif, using a limited current technique, investigated mass transfer to the particles of a fluidized bed as well as to the wall enclosing them. For the latter he derived ... 

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