Characterization of a Sodium Persulfate Sustained Release Rod for in Situ Chemical Oxidation Groundwater Remediation

In situ chemical oxidation (ISCO) using sodium persulfate (SPS) is an increasingly implemented process for the remediation of subsurface contamination. For this study, a SPS sustained release rod (SR-rod) was prepared by mixing SPS particles and melted paraffin wax with a SPS/wax mass ratio of 6/1. Observation of the rod in potassium iodide solution revealed that, as soon as the rod was placed in the solution, the color turned yellow due to the oxidation of I- to form I-2. The solution became darker at the bottom and lighter toward the top because the density of dissolved SPS causes it to sink along the surface of the rod. On the basis of the results of the column experiment which creates a steady SPS release from the rod, a matrix boundary diffusion controlled two-film theory model was derived to explain the SPS release behavior. On the basis of the model developed and the effective SPS diffusion coefficient within the rod matrix, the minimum release time for the rod can be determined. The designed sustained release system would be expected to have a SPS duration of at least longer than the determined minimum release time regardless of site conditions. The SPS SR-rod minimum release time as a function of the radius of the rod was established. With a better understanding of the characteristics of the sustained release system, the SPS SR-rod could potentially be developed as a practical approach for in situ remediation of contaminated aquifers.