| The kinetics of gold cementation was studied by the use of rotating disk method using zinc powder. The rate constant was proportional to the square root of agitation speed as suggested by the Levich equation, Κ = 0.62 D＾(2/3) v＾(-l/6) ω＾(1/2). In the absence of initial zinc ions and above 40℃, it is considered that the overall cementation rate would be controlled by mass transfer rate through the aqueous diffusion boundary, however, below 40℃, the reaction mechanism would be changed. When zinc powder is added as a precipitant, the rate constant increases with increasing agitation until a condition of full particle suspension is roached. Thereafter, the specific rate constant is essentially independent of any further increase in agitation speed. |
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