Background: Brazilian bentonites have low sodium concentration in their interlayer region. This constitutes a problem for the majority of industrial applications, that demand characteristics of sodium bentonites.
Objective: as a solution for this limitation, sodium carbonate is added to in natura clays, promoting ion exchange between interlayer cations and sodium.
Method: a granted process was based on the principle of Stokes’ Law (BR Patent 10 2013 016298). For this we used four glass columns in series in which were applied a high water flow to obtain purified clays. It was proposed a simple, fast and economic method for sodium determination that was developed and applied in bentonites by means of flame photometry. The equipment calibration was made with NaCl standard solution in concentrations between 80 and 110 ppm. The suspensions bentonites had been separate by means of centrifugation, being thus analyzed by a flame photometer.
Results: samples had been prepared according to manufacturer specifications to contain detectable amounts of sodium for the photometer detection. A resulting linear relation between average value readings versus sodium standard content solution (both in ppm) was obtained in logarithmic scale, as expected.
Conclusions: The procedure allowed to define a method that could be used in the sodification control process, being thus possible to differentiate the sodium cation content from the value of cation exchange capacity (CEC) of the bentonite. X-ray analyses of in natura and sodified clays show nanostructural differences concerning interlayer distance.