Integrated Electrodialysis (ED) and Catalytic Electrochemical Reduction (CER) Process for the Removal of Perchlorate from Dilute Aqueous Solutions

University Of Delaware, Newark DE

Investigators

Abstract

Huang, Chin-Pao CBET-0965984 The objective of the proposed research is to study the catalytic electrochemical reduction of perchlorate at low concentrations, i.e., < 1 ppm, in water under ambient conditions. Perchlorate, an emerging contaminant, can interfere with the metabolism of the thyroid gland in humans. Although the US EPA has yet to establish a drinking water standard for perchlorate, the agency has issued a Drinking Water Equivalence (DWE) of 24.5 ppb. Several states have reported the presence of perchlorate at alarming concentrations in their source waters and subsequently established precautionary drinking water standards for perchlorate in the range of 4 to 18 ppb. Recent advances in analytical chemistry of perchlorate have enabled detection of the emerging contaminant at ultra-low levels, i.e., ppb. Although adsorption processes such as ion exchange can separate perchlorate from water, chemical reduction (i.e., transformation) provides the ultimate solution to perchlorate contamination. To date, perchlorate reduction has been attempted only with biological processes. However, biological methods generally have limited public acceptance and are difficulty to apply to small to medium scale systems. There is a need for innovative technology for the treatment of drinking water that is easy to operate and affordable and has wide public acceptance. The proposed research is to study the removal of perchlorate from dilute aqueous solutions by the electrodialytically assisted (EDA) catalytic electrochemical reduction (CER) process. Newly synthesized perchlorate selective membranes will be used to enhance the accumulation of perchlorate at the vicinity of the negatively charged catalytic electrode (i.e., cathode). The catalytic electrode is prepared by the deposition of nano-sized non-precious metallic catalysts that have exhibited a high perchlorate reduction rate. The proposed research is to achieve the following objectives: 1) to synthesize, characterize and test pe-chlorate selective membranes; 2) to prepare, characterize, and test nano-metallic catalysts for electrochemical reduction of perchlorate; 3) To identify important factors controlling the electrodialytically assisted (EDA) catalytic electrochemical reduction (CER) of perchlorate; and 4) To study the short-term performance of the total electrodialytically assisted (EDA) catalytic electrochemical reduction (CER) process. Perchlorate selective membranes will be synthesized from PVC, plasticizers, additives, and ionophores (i.e., perchlorate complexes). Metallic catalysts will be made from Cd, Cr and Ti in mono-, bi- or tri-metallic forms. The best perchlorate selective membranes and the best metallic catalysts will be selected for fabricating the EDA-CER reactor. Pertinent factors that control the overall perchlorate reduction and performance of the EDA-CER reactor will be studied. The proposed research involves the study of two technologies: synthesis of a perchlorate selective membrane and catalytic electrochemical reduction. In addition to water treatment applications, the perchlorate selective membranes can be used to separate perchlorate from biological fluids and as a sensor for perchlorate ions in medical applications. The CER process can also be used to remove several contaminants in water, specifically nitrate, heavy metals, and volatile halogenated organic carbons (VHOCs). The integrated EAD-CER process represents a new approach to water purification for the removal of perchlorate in addition to other contaminants at dilute concentrations. The proposed research project will have an impact in outreach/education and public health awareness. The University of Delaware has a long history of working with minority and underprivileged communities through its well-established undergraduate programs on campus, e.g., RISE and NU-CLEUS. They will take advantage of these avenues to recruit undergraduate students from under-represented and minority groups throughout the country to participate in their research projects. They will work with regional high school science teachers to develop teaching materials in water technology. They have been active participants in many undergraduate research programs such as NSF-REU for under-graduates and NSF-RET for high school science teachers. In order to increase public awareness of safe drinking water, they will work with the Delaware 4-H program and the Philadelphia Science Museum to develop science education modules on emerging contaminants in drinking water. Additionally, they will establish an interactive web-based program on environmental safety for the general public as well as school children. The PI will host the 6th International Conference on Sustainable Water Environment at the University of Delaware in July of 2010. It is expected that this international event will strengthen global collaboration on water research.