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Cycle 9 (2020 Deadline)

Biochar facilitated bioremediation: a green solution for dioxin/furan pollution

PI: Dang Thuong Huyen (, Ho Chi Minh City University of Technology
U.S. Partner: Karl Rockne, University of Illinois at Chicago
Project Dates: June 2021 - June 2024

Project Overview:
Agent Orange was used to defoliate more than 31,000 km2 of forest in Vietnam. Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans formed during the manufacturing process, together with co-contamination by other chemicals and heavy metals, have resulted in widespread contamination of soils across the country. More than 35.42 million liters of Agent Orange, Agent White, and Agent Blue were transported and stored during the Vietnam War, and the most widely used of these agents was Agent Orange, resulting in dioxin hotspots at airbases where the substance was stored and transferred. This project will focus on the Bien Hoa site, given its proximity to Ho Chi Minh City University of Technology (HCMUT) and the team’s extensive experience working on bioremediation efforts at this location. High concentrations of dioxins were observed at several boreholes obtained from the site, and the results demonstrated that the greatest concentrations of 2,3,7,8-TCDD were due to defoliants in a restricted zone within a few meters of the surface. Toxic equivalency factors for some samples exceeded 1000 pg/g, primarily from high concentrations of tetra-CDDs.

The project’s goal is to address this problem through a collaboration between HCMUT and the University of Illinois at Chicago on a green, circular economy solution using plant-based biochars sourced from waste stocks. The team will achieve this goal by investigating how the beneficial properties of biochars to sequester hydrophobic pollutants and facilitate electron transfer to microbes living on/near the organic matter surface can be optimized for improved bioremediation of PCDDs/TCDDs. The research represents an interesting symmetrical approach to the problem of Agent Orange, using plant-based products to facilitate the treatment of pollution.

The scientific merit of this project will result from investigations into the sorption and biostimulation potential of biochars produced from various agricultural sources. Knowledge of the sorption potential and energy will result from a comparison of sorption isotherm data to various mechanistic sorption models. Two different pyrolysis temperatures will be used to test the hypothesis that higher temperatures produce biochars of greater graphitic content that more efficiently stimulates PCDD/F dechlorination. Thus, this research will address both an urgent national need to remediate contaminated soil while furthering fundamental knowledge of biochar-mediated dechlorination. Recently, the Vietnamese national government promulgated the circular economy in its five-year strategic plan to beneficially reuse waste products from one industry as feedstocks for others. Thus, the utilization of these types of biomass for the fabrication of efficient adsorption products is an effective and sustainable green solution with potentially great benefits to the economy and the environment.

9-553 Jackfruit Preparation9-553 Biochar Production
Team members prepare jackfruit and durian shells.Rice husk biochar production Photo credit: PI Huyen

Summary of Recent Activities:

During the third quarter of 2022, Dr. Huyen and her team collected more agricultural by-products for their experiments. They roasted materials like durian and jackfruit rinds, coffee and rice husks, and coconut husks and shells into biochar and then characterized the resulting products using various analytical chemistry techniques. They have also been characterizing soil samples they collected from Bien Hoa Airbase. While awaiting the results of dioxin analysis and DNA sequencing being conducted separately, the team at HCMUT is conducting some experiments on atrazine remediation and writing a paper on their biochar characterization work.

A challenge has arisen with the soil dioxin analysis. Dr. Huyen had intended to send her samples to a lab in Ho Chi Minh City, but in the late summer and fall of 2022 it was awaiting recertification and license renewal so it was unable to receive any materials. She then tried to send some samples to a university-based lab in Taiwan, but due to new policies regarding the importation of soils, the samples were sent back by the Taiwanese authorities. As of the end of October, she was exploring the possibility of sending the samples to Japan for testing by a company there, but the process is time-consuming.

Dr. Huyen will be visiting her U.S. partner Dr. Karl Rockne and other colleagues at the University of Illinois Chicago November 7-17. While at UIC she will be extracting and sequencing DNA from the Bien Hoa soil samples, performing aerobic experiments on atrazine on biochars with distinct properties to examine the behavior and effectiveness of atrazine-treated microorganisms. She will also spend some time in Prof. Brian Chaplin’s lab studying the electrochemistry of biochar. Dr. Huyen and her colleagues will be working on joint publications on biochar properties and discussing future research directions on the project. Dr. Rockne is expected to visit Vietnam in March-April 2023 to present short-term training courses and participate in seminars to exchange information with colleagues at HCMUT.

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