Direct Chemical Oxidation of Mixed or Toxic Wastes

Direct Chemical Oxidation (DCO) is an ambient-pressure, low-temperature (<100 °C), and aqueous-based process aimed at the destruction of the organic fraction of hazardous or mixed waste. This paper presents an in-depth examination of the DCO process, utilizing the peroxydisulfate anion (S2O82-) in both acid and base solutions. By recycling the byproduct, typically sodium or ammonium hydrogen sulfate, electrolytically to produce the oxidant, the process enhances sustainability. The findings detail the reaction kinetics and reveal that dilute organics (concentrations < 50 ppm) are oxidized more rapidly due to the influence of intermediate free radicals on peroxydisulfate activation. Additional insights include the conversion of phosphorus, sulfur, and amino nitrogen groups to their oxyanions, while noting that ammonium ions and perfluorinated polymers remain intact. The speed of oxidation is shown to be independent of pH above 1, with the process being particularly effective in basic solutions for treating halide-rich compounds. This research demonstrates a viable method for the in situ treatment of organic contaminants in various porous media, reflecting its potential utility in addressing environmental hazards effectively.