A comparative study on the uptake properties of alginate microcapsules containing Cyanex 302 extractant, Lewatite TP 214 chelating resin, and Amberlite 200CT strongly acidic ion exchanger has been conducted using Ag+ as the target ion. The study resulted in an analytical formula, as well as three phenomenological breakthrough formulas that are also applicable in other fixed-bed operations. It also demonstrated a close similarity of the uptake properties of alginate microcapsules (MCs) and the chelating resins. Advantages of MCs over chelating resins include ease of preparation, ability to immobilize different extractants, and, most remarkably, an enormous distribution factor (K-d approximate to 10(6) cm(3)/g). As for the stabilization of MCs, two different methods of coating and matrix modification were applied; the latter proved to be superior, because of enhancement of both the uptake capacity and the column performance. Another achievement of the current study was the discovery of a new method for estimating the thickness of the coating layer of MCs.