Enhancement of the Exchangeable Sodium Percentage of Bentonites through Dialysis

ABSTRACT

Dialysis has been used over the past decades as a laboratory procedure to homoionize the exchange complex of bentonites and remove the excess soluble salts naturally contained in the bentonite pores. However, if the bentonite fabric is in an aggregated state, reduced pore accessibility limits the replacement of interlayer exchangeable cations by those in the dialyzing solution, thus undermining the efficiency of the homoionization process. To overcome these limitations, this study introduces a novel dialysis procedure that incorporates a preliminary treatment phase prior to homoionization. The additional phase consists of dialysis cycles with deionized water, aimed at promoting tactoid dispersion and improving accessibility of interlayer cations. A powdered bentonite was used to assess the improvement in sodium homoionization achieved with the new method compared with the conventional procedure. The modified dialysis procedure increased the exchangeable sodium percentage from 35 % to 78 %, accompanied by a corresponding decrease in the exchangeable calcium percentage.