Prediction of column leaching behaviour based on batch leaching tests with different liquid to solid ratios

Abstract

Batch leaching tests with different liquid per solid ratios and contact times were conducted on tsunami deposit soil. The chemicals of concern are arsenic (As), boron (B), and sodium (Na). Two parameters were obtained from the tests, which are the partition coefficient (Kd) and the available mass of contaminants per unit mass of soil (MT). Here, the "available mass of contaminants" refers to the mass of contaminants that will take part in adsorption-desorption reaction, but not the total mass of contaminants which are present in the soil system. Using these two parameters, temporal concentration profiles based on the analytical solution of a one-dimensional advection-dispersion equation were plotted for different contact time, and compared with the results of column leaching tests, which were conducted separately using 10-cm long and 5-cm high columns. From the comparisons, multiple sets of two parameters at different contact times are needed to express the column test results for all three chemicals. To predict the column leaching behaviour from batch test with minimum numbers of contact times, two contact times, 6 and/or 24 hours can be selected.