The Role of Mass Transfer in the Removal of Heavy Metal Ions by Ion Exchange Using Batch Gas Sparged Vessel

T. M. Zewail

Abstract
Mass transfer behaviour of a batch gas sparged vessel for conducting ion exchange reactions involving heavy metal removal has been investigated. The effect of various parameters such as type of heavy metal ion (Ni2+, Cd2+), superficial gas velocity, physical properties of the solution and temperature on the mass transfer coefficient was studied. It has been found that mass transfer coefficient increases as gas superficial velocity and temperature increase. At equilibrium, a maximum removal efficiency of 99.98 % was obtained for Ni2+ and Cd2+. Activation energy calculations gave the values of E = 2.4 and 3.3 kJ mol–1 for Ni2+ and Cd2+ respectively. These values confirm the diffusion controlled nature of ion exchange reactions. Dimensional analysis of the present mass transfer data led to the following correlations: For Ni2+ JD = 0.334 (Re · Fr)–0.14 For Cd2+ JD = 0.125 (Re · Fr)–0.25 The importance of these mass transfer correlations in the design and operation of gas sparged vessels used for conducting ion exchange reaction was highlighted.

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Keywords
mass transfer, ion exchange, gas sparging, heavy metal removal