Effect of cations on permeant flow-through bentonite clays using a rapid filter press test

The relative effects of different cations on permeant flow through two comm ercially available Wyoming bentonite clays have been assessed using a rapid filter press (RFP) test. The clays were exposed to test solutions of sodiu m, potassium, calcium, ammonium and zinc ions, all added as acetates at dif ferent molarities, so that the relative effect; on flow rates could be dete rmined. Results showed that ammonium and potassium had particularly deleter ious effects on permeant flow for both clays, while solutions of sodium and zinc acetate permeated at much lower rates. Of the two materials tested, t he modified bentonite, which had been treated with surface-active additives , had significantly improved performance compared to the untreated clay. XR D has been used to identify changes in interlayer spacing (d(001)) associat ed with exposure to the different acetate solutions.