Remediation of In–situ chemical oxidation of organic contaminants in the subsurface environment based on carbon catalysts

Abstract:  

Beyond conventional organic pollution originating from large scale industrial complexes, soil and groundwater contamination caused by recalcitrant micropollutants from daily human activities has recently emerged as a critical environmental concern. In particular, pharmaceuticals and endocrine disrupting chemicals (EDCs) discharged via municipal wastewater are not completely removed by conventional wastewater treatment processes. Consequently, they enter subsurface environments, posing severe threats to ecosystems and the security of groundwater resources. In this talk, we present advanced technologies for fabricating high-performance carbon based nanocatalysts via waste upcycling and chemical synthesis, alongside field scale in-situ remediation outcomes for the effective control of these recalcitrant organic pollutants.

First, we developed resource circulating carbon catalyst fabrication technologies using municipal waste and agro industrial byproducts, as well as high-performance carbon catalyst synthesis techniques via precise structural tailoring. Carbon catalysts with maximized specific surface area and subsurface mobility were fabricated using various raw materials, including agricultural and marine byproducts (e.g., mulberry wood, rice husk, and seaweeds such as Capsosiphon fulvescens, Undaria pinnatifida, Gracilaria, and Laminaria), disposable diapers, and conductive polymers.

Furthermore, functionalized carbon catalysts with abundant active sites such as mesoporous carbon hollow spheres (MCHS), N-SAPC, and N-MCHS were synthesized using precursors like melamine and urea. Notably, by establishing a metal-free carbon catalyst system that eliminates concerns over heavy metal leaching, we confirmed superior oxidative degradation performance toward a broad spectrum of micropollutants, including pharmaceuticals and personal care products (PPCPs) and EDCs. Furthermore, incorporating Hemin or polyaniline (PANI) to engineer nitrogen (N) and metal active sites on the catalyst surface enabled us to elucidate the degradation mechanisms of target micropollutants (e.g., Diclofenac and Simazine) under visible-light conditions (KBN@TiO2@rGO) and dual-oxidant systems.

These research outcomes were subsequently applied to field scale subsurface remediation projects to validate their performance under real field conditions. On actual organic contaminated sites, in-situ reactive zones (IRZs) based on Fe(II)/PS and CAC/PS/CaO2 advanced oxidation processes were operated to induce rapid pollutant degradation. In addition, an injectable permeable reactive barrier (iPRB) incorporating colloidal activated carbon (CAC) was operated to effectively intercept plume migration. To address final residual contamination, a polishing process utilizing persistent release persulfate (PS) candles was introduced, ensuring both long term sustainability and stability in remediation efficiency.

In conclusion, this presentation proposes a novel paradigm of resource circularity turning the ’cause of environmental pollution’ into the ‘solution for environmental remediation’ by upcycling low value municipal waste into precursors for high-performance carbon catalysts and key materials for subsurface restoration. This approach provides a highly sustainable and value-added technological strategy capable of simultaneously solving subsurface contamination caused by recalcitrant organic pollutants and waste management challenges.

Bio:

Won Sik Shin is a Professor in the Department of Environmental Engineering at the Kyungpook National University, Daegu, Republic of Korea. He received Ph.D. degree from the Department of Civil and Environmental Engineering, Louisiana State University, USA at 1998. After graduation, he worked for Hazardous Substance Research Center/South & Southwest as a post-doctoral researcher. He joined water environmental research team at Pohang Research Institute of Science and Technology (RIST) as a senior researcher working for biological wastewater treatment and soil remediation for steel-making industry. He started his academic career at the Kumoh National Institute of Technology, Gumi, Korea as an assistant professor in 2002. After two years, he joined in the Department of Environmental Engineering, Kyungpook National University (KNU), Daegu, Republic of Korea since 2004. In 2007, He was nominated as POSCO-endowed professor. He received the “2025 Researcher Award” from Korea Society of Soil and Groundwater. He served as the President of Korean Society of Sediment Environment and Dredging. Currently he is serving as Director of Research Institute of Advanced Energy Technology and Head of Center for Research Facilities at KNU. Mainly his recent research activities are focused on i) application of advanced oxidation process (AOP) for the remediation of contaminated groundwater using metal-free carbon-based catalysts, ii) the remediation of heavy-metal contaminated sediment such as dredging/capping and stabilization, and iii) photocatalytic/electrochemical degradation of micropollutants using solar energy.