LEACHING RATES OF ROCK-FORMING COMPONENTS THROUGH ACIDIC ALTERATION

A series of experiments on the interactions of a glassy basaltic andes ite with acidic solution in a flowing system were carried out. Leachin g indices of seven components (Na, K, Ca, Mg, Fe, Al and Si) were defi ned to compare the relative leaching behaviour of these components at all reaction stages. At 160 degrees C and using 0.24 N H2SO4 solution, Na, Ca and Al were leached easily, compared with K, Mg, Fe and Si. Al though Si concentrated in the final residual rock, it was not always t he hardest component to leach. The leaching behaviour of these seven c omponents in a glassy rock agreed with that in crystalline rock.Result s of three experiments at 80, 120 and 160 degrees C using 0.12 N HCl s olution showed that the rise of temperature accelerated the leaching r ate of each component, whereas the leaching index for each component w as not affected by temperature. This indicated that the leaching proce sses for these seven components were independent of temperature. On th e other hand, in a series of the experiments at 160 degrees C using 0. 24, 0.12 and 0.0024 N HCl solutions to examine the effect of acidity, the change in acidity of the reacting solution affected not only the r eaction rate but also the reaction processes of the components. Na, Ca , Fe and Al became hard to leach as acidity diluted and Si became easy to leach and comparable to these components.