Superfund Research Program
Oxidative Remediation of Recalcitrant Contaminants with Persulfate
Project Leader: David L. Sedlak
Grant Number: P42ES004705
Funding Period: 2006-2022
Project Summary (2011-2017)
Persulfate (S2082-) is a relatively inexpensive reagent that can be used to oxidize many of the most recalcitrant contaminants present at hazardous waste sites. Although it is becoming more popular for hazardous waste site remediation, the chemical reactions through which persulfate oxidizes contaminants are not well understood. The overall goal of this research is to develop and test new approaches for oxidizing contaminants that are difficult to treat with existing technologies (e.g., PCBs, 1,4-dioxane and PFOA) and apply it to make treatment systems more robust and efficient. Through the use of kinetic models and detailed research on reaction mechanisms, the researchers are developing the means of predicting contaminant transformation rates and optimizing system performance.
This mechanistic understanding of persulfate chemistry requires that researchers build increasing complexity into the model in stages. Initially, the researchers are calibrating their kinetic model for the homogeneous reactions through which persulfate is converted into oxidants using experiments with various compounds that react predominantly with sulfate radical or hydroxyl radical. After calibrating the model over the range of conditions likely to be encountered during remediation, the researchers investigate the role of heterogeneous reactions of iron-containing solids on the initiation of radical production. By applying findings from experiments in heterogeneous systems with state-of-the-art surface characterization techniques, the researchers are synthesizing new types of heterogeneous catalysts for ex situ treatment of contaminated groundwater. They are also using results from the heterogeneous experiments to improve the predictive ability of the model and identify optimal conditions for remediation. After defining the conditions that are best suited for contaminant remediation, the researchers will assess the potential formation of toxic intermediate products during the remediation process using high content screening assays and mass spectrometry. This research is leading to a mechanistic understanding of persulfate chemistry that should, in turn, lead to a level of understanding that will allow engineers to avoid excessive use of reagents and the formation of toxic intermediates when persulfate is used for remediation.