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Cycle 9 (2020 Deadline)
Biochar facilitated bioremediation: a green solution for dioxin/furan pollution
PI: Dang Thuong Huyen (huyen1982@hcmut.edu.vn), 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.
 |  | | Team members prepare jackfruit and durian shells. | Rice husk biochar production Photo credit: PI Huyen |
Summary of Recent Activities:
In addition to a field trip to collect more agricultural by-products for use in their project, during the first quarter of 2023 Dr. Huyen and her team focused primarily on lab work. This included adding Raman spectroscopy measurements to their arsenal of techniques and installing a new Soxhlet system donated by the Japanese environmental company Yagai Kagaku, which also provided the team with the necessary training. The Soxhlet system is used to completely extract and concentrate dioxin from soil samples, after which the samples will be sent to Japan for further analysis. In addition, the team has worked on analyzing the five types of biochar involved in their study, ultimately selecting two biochars with different characteristics at two pyrolysis temperatures—rice husk biochar and coffee shell—for further experimentation.
Dr. Huyen has been collaborating closely with the other PEER PIs in Vietnam who are working on dioxin-related projects, including sharing soil samples and coordinating experiment plans. She also participated in the final project workshop organized by PEER Cycle 6 PI Dr. Ngo Thi Thuy Huong entitled "Persistent Organic Pollutants and Dioxin Contamination: Environmental Issues and Mitigation Technologies," during which Dr. Huyen presented her team’s research results and analysis on the characteristics of five types of biochar that were pyrolyzed at two different temperatures. In addition, as a further example of integration of her project with USAID’s relevant activities in Vietnam, she has also agreed to mentor a female graduate student who works on the support team of the USAID contractor working on dioxin remediation.
Although the project still has another year to run, it is also helping facilitate new linkages and applied research opportunities not related to dioxin remediation. Based on research on the characteristics of biochar through this project, Dr. Huyen and her team have connected with companies such as BASF, HRK, Sourcebynet, and Texstyle. They held a seminar to discuss the potential of agricultural byproducts for the sustainable development goals of businesses, and the PI presented the potential research on biochar and agricultural byproducts to the attending representatives. Additionally, the team is conducting negotiations on the application of their biochar research in producing water-permeable bricks to support the protection of groundwater resources and prevent flooding. One of the companies is proposing that the PEER researchers join their research team on wood fiber, and another has agreed to sponsor research on producing bioplastic materials from seaweed and dragon fruit peels. Dr. Huyen’s group is also researching the potential of biochar for use in energy storage and waste management using devices sponsored by this project, and a third firm has expressed interest and plans to prioritize their research for startup funding soon.
In the rest of the spring and summer of 2023, the researchers will conduct five experiments for treating dioxin-contaminated soil under different sets of aerobic and anaerobic conditions. Other plans include analyzing dioxin isomers, completing DNA extraction and sequencing of microorganisms collected from their soil samples, and submitting a research article on the characteristics of biochar.
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