Superfund Research Program
Chloro-Organic Degradation by Polymer Membrane Immobilized Iron-Based Particle Systems
Project Leader: Dibakar Bhattacharyya
Grant Number: P42ES007380
Funding Period: 2000-2019
Chloroethylenes, chlorophenols, and polychlorinated biphenyls (PCBs) are persistent and widely dispersed in the environment, and are found in various Superfund sites. Because of the diversity of chemicals present in hazardous waste and Superfund sites, the development of both oxidative (use of hydroxy radicals) and nanotechnology-based reductive (nanosized zero-valent metals) processes is essential to bring solution to various remediation problems.
The hydroxy-radical based oxidative technique results in the generation of non-toxic organic acids and CO2. The team’s recent studies have dealt with the use of a chelate-based modified Fenton reaction (developed in their laboratory and also tested in an Industrial site) for the controlled dechlorination of trichlophenol. This requires three nontoxic chemicals: iron salt, hydrogen peroxide (H2O2), and a chelating agent. Their new approaches include the simultaneous generation (for on-site use) of needed hydrogen peroxide and chelate (gluconic acid) by using an inexpensive enzyme (glucose oxidase), glucose, and air. For in-situ remediation applications, on-site H2O2 generation (rather than storing and transporting highly concentrated H2O2) would also be highly desirable. The results showed that it is indeed possible to achieve dechlorination of chloro-organics (such as, trichlophenol) using enzymatically generated hydrogen peroxide and chelate gluconic acid near neutral pH.
In the area of nanotechnology-based dechlorination techniques, Dr. Bhattacharyya’s team has made three highly significant advancements for toxic organic remediation applications. (1) They have synthesized 20-30 nanometer size iron-nickel and iron-palladium nanoparticles in a polymeric membrane matrix providing reusability. (2) This is the first study to prove that trichloroethylene (present in contaminated groundwater) can be rapidly dechlorinated to ethane (quantified by gas chromatography) as the main product with only small amounts of nanosized iron-nickel particles. The use of nanosized particles altered the reaction pathway and eliminated toxic intermediate formation. (3) The team’s novel membrane development with immobilized palladium coated iron nanoparticles showed near complete dehalogenation (in less than 2 hours) of two types of PCB compounds by milligram quantities of materials.