The effect of the electrolyte concentration and pH on the rheological properties of the original and the Na_2CO_3-activated KUtahya bentonite

摘要

The effect of the Na_2CO_3 activation on the rheological properties of a bentonite from Kiltahya (Turkey) was investigated. The bentonite was activated with Na_2CO_3 at different dosages (1-15 g Na_2CO_3/100 g bentonite). The activated samples were examined by chemical and X-ray diffraction analysis. The calcium bentonite was completely converted to sodium bentonite when the Na_2CO_3/bentonite ratio was 2.5/100. The rheological values showed a maximum after addition of 2.5/100 Na_2CO_3 (bentonite concentrations 2-6/100 w/w). At 2.5 g Na_2CO_3/100 g bentonite, the shear stress was also measured at several NaCl and Na-hexametaphosphatC concentrations. NaCl addition decreased the rheological properties up to NaCl concentrations of 0.005 moll~-l. Further addition of NaCl increased the rheological properties again. The addition of Na-hexa- metaphosphate caused a decrease in the rheological properties to a constant value higher phosphate concentrations. The lowest yield stress was obtained around pH 7.