Electrokinetic study of the buffer capacity of some soils from Tenerife.

During electroremediation treatment applied to polluted soils, secondary reactions may result which can influence the efficiency of a decontamination process. The most important of these secondary reactions is the generation of acid and alkaline fronts as a consequence of the electrolysis of water which occurs at the electrodes. These fronts interact with the soil fraction closest to the electrodes, and their influence on the process of pollutant removal is dependent on the buffer capacity present in the soil. This buffer capacity, related to the presence of specific functional groups, can be determined by volumetric techniques in which the soil is placed in contact with an alkaline material for a given time period, and subsequently analyzed for the resultant pH. This information may not be directly applicable to the electrokinetic process since it may be related to a process involving dynamic changes generated by the continuous electrical field applied to the soil. The objective of the present study was to determine the buffer capacity of the soil by means of quantitative determination of a “buffer function” obtained under identical conditions to those operating during an electroremediation treatment. This function was determined for a group of soils from Tenerife Island, Spain. The results obtained from both techniques are shown and compared, and the findings reveal some discrepancies related to the type of acid-base disturbance applied. In the case of regulatory function, it is possible to relate these variations to some soil properties such as pH and the presence of carbonate.