In the process of producing ethanol, vinasse is a by-product generated in large scale, on average, at a rate around 13 L of vinasse per liter of distilled alcohol. This volume represents a problem in conditioning and treatment processes of this wastewater, which most of time is incorporated into the soil by fertigation. Considering the high levels of nutrients, especially potassium and the high content of organic matter, the disposal of vinasse into the soil needs further studies, because there may be leaching of several elements to groundwater. Batch tests were performed, which allowed assessment of the effect of different factors such as variation of the soil to solution ratio and the variation of contact time between soil and solution to evaluate the mobility of potassium in three different soil samples. The results showed that in the tests with the soil:solution ratio of 1:50, in all samples, the sorption was greater than with the ratio 1:4. The ideal contact time for establishment of equilibrium conditions was 24 h. The sample with higher percentage of clay and higher cation exchange capacity demonstrated the highest sorption of potassium.
batch test; isotherm; agroindustrial residue
