KINETICS OF GOLD LOADING FROM BROMIDE SOLUTION ONTO AN ANION-EXCHANGERESIN

The kinetics of loading of gold from bromide solution onto an anion ex change resin, PAZ-4, was investigated in a batch stirred reactor. The initial loading rate was described mathematically by a first-order rea ction rate equation. The effect of such variables as agitation speed, temperature, resin particle size, resin concentration, initial concent ration of gold and bromide in solution on the rate was investigated. T he model described fairly accurately the loading process in terms of t he varibles investigated. The rate constant for the initial loading ra nged from 0.5 to 1.3 x 10(-3) sec-1 and the half-time was 9.3 to 56 mi nutes. The initial rate constant increased with increasing temperature under the conditions investigated with an activation energy of 15.7 k J/mole (3.8 kcal/mole). The rate constant was directly proportional to the concentration of the resin in solution. The subsequent reduction reaction was also modeled by the first-order rate equation and the app arent rate constant was estimated to be 3.0 x 10(-6) sec-1 with a half -time of about 44 hours. The loading kinetics involve two major proces ses: (i) the initial rapid loading dominated by ion exchange-type adso rption, and (ii) the slow electron exchange reduction reaction which b ecomes dominant only after the completion of the ion exchange process.