MECHANOCHEMICAL EFFECTS ON PHYSICOCHEMICAL PARAMETERS OF HOMOIONIC SMECTITE

According to previous works and using the sensitivity of isoelectric p oint or point of zero charge (IEP and PZC), determinations by diffusio n potential method were performed on a smectite with different homoion ic (Na+, K+, Li+, Ca2+ and Al3+) cations which were treated thermally and mechanically, in order to determine the influence of these treatme nts on the structural parameters. XRD general spectra and d(001) peaks showed that smectite peaks were more affected by mechanical treatment rather than by thermal treatment. Smectites with Ca2+ and Al3+ were a ffected to a lesser extent in agreement with infrared (i.r.) diagrams. PZC values obtained increased in the order of initial <thermal<mechan ical treated samples, raising up to pH around 7 for Na+, K+ and Li+ an d pH = 6.0 and 4.8 for Ca2+ and Al3+ samples, respectively. These incr eases in PZC values agreed with the structural Al3+ release which acte d as a mechanical mixture with the residual smectite structure and wer e confirmed by the disappearance of octahedral Al coordination in the i.r. spectra. (C) 1997 Elsevier Science B.V.