A study of zinc separation from an alkaline leach liquor using fixed and moving bed ion exchange systems
As far as it is known from the survey of literature this is the first study of the problem of Zn separation from NaOH solution through ion exchange. It was therefore essential to carry out a selection procedure for finding a suitable resin for the separation. Ten resins were tested from which Amberlite IRC-718 was selected. The resin was found to tolerate the high pH involving the process and give a favourable equilibrium relationship for 0.1 and 0.2M NaOH solutions. Work concerning fixed and moving bed processes was done to determine various design parameters such as mass transfer coefficients, zone height, number and height of transfer units. The kinetics of ion exchange was studied through fixed bed operation by obtaining breakthrough data. These data were analysed through a new method and also by the methods of Michaels,and Moisan and O'Hern. For some data the methods of Michaels, and Maison and O'Hern were found to be inadequate while the new method was applicable to all the data. The kinetics of ion exchange was found to be controlled by diffusion of ions in the solution. This was also confirmed by the determination of activation energy which gave a value of 1.6 kcal/mole. Correlations for saturation time, zone height and zone velocity were established, The extraction efficiency of 99.6% was achieved using a moving bed system with bed height of 24cm and solution flow rate of 7 ml/min. The height of transfer units was found to increase with Zn and OH ions concentration, solution flow rate, and cycle time. However, HTU was unaffected by bed height increase. Correlation of HTU with Zn concentration was established.
Networked Digital Library of Theses and Dissertations