Abstract:
To study fate and transport of hexavalent chromium through soil. The effect of pore velocities on hexavalent chromium transport through soil was measured Soil was used from Mabtapud industrial estate area, Rayong, Thailand, which is mainly silty sand. Batch experiments were to set up to study the efficiencies of hexavalent chromium adsorption at pH 4, 7, and 10 and ionic strength at 0.01 M and 1.0 M. Column experiments were aimed to calculate the dispersion coefficients by the tracer tests and to study the transportation at various pore water velocities of 2.5, 4.9, 9.9 and 19.7 cm/hr. Moreover, using HYDRUS2D computer software to simulate output data to compare the result from column experiments. The results from batch experiments showed that the hexavalent chromium adsorption capacities increased with decreasing solution pH. The higher ionic strength resulted in an increase in hexavalet chromium adsorption capacities only at the pH 7. Finally, it was found that the adsorption Isotherm for this study was agreeable both Langmuir adsorption isotherm and Freundlich adsorption isotherm. The results of tracer test experiments showed that the value of dispersion coefficient was 9.39 cm2/hr. Then, the column experiments which were run with lowest pore water velocity at 2.5 cm/hr in any pH consumed the time more than the higher pore water velocities cause of the contact time was increased to promote the adsorption capacities of hexavalent chromium. After comparing the results and simulated data from HYDRUS2D founded that the column experiments which were run with the lowest pore water velocity at 2.5 cm/hr in any pH was similar to HYDRUS2D. In the contrast of the higher pore water velocity is different. Simulated data from HYDRUS2D were slower than the experiments. It could describe this by using the non-equilibrium transport assumption but the HYDRUS2D was not.