AUTHOR=Uzun Habibullah 

TITLE=The impact of ash-derived natural organic matter on the adsorption of MIB and geosmin by powdered activated carbon

JOURNAL=Frontiers in Environmental Science

VOLUME=Volume 13 - 2025

YEAR=2025

URL=https://www.frontiersin.org/journals/environmental-science/articles/10.3389/fenvs.2025.1660425

DOI=10.3389/fenvs.2025.1660425

ISSN=2296-665X

ABSTRACT=Wildfires substantially alter watershed chemistry, increasing natural organic matter (NOM) loads and nutrient fluxes into surface waters, which can stimulate algal blooms and the production of taste and odor (T&O) compounds such as 2-methylisoborneol (MIB) and geosmin. This study investigated the performance of five commercially available powdered activated carbons (PACs) in removing MIB and Geosmin from water impacted by ash-derived NOM. Adsorption experiments were conducted using NOM-free water and wildfire-generated white-ash leachate (WA-L), black-ash leachate (BA-L), and unburned vegetation leachate (UV-L), each with 7.5 mg/L DOC and varying aromaticity and molecular weights (MW) (as indicated by SUVA254 and E2/E3 ratios). Under NOM-free conditions, PACs with significant micropore volumes exhibited exceptional adsorption capabilities. PAC-4, distinguished by its narrow micropores (∼0.15 cm3/g in the 0.54–1 nm range) and high pHpzc (8.7), exhibited the highest uptake of both compounds. The adsorption kinetics revealed that within 60 min, over 80% of MIB and 90% of geosmin were removed by all the carbons. PACs with well-balanced microporosity exhibited the most rapid initial uptake (10–30 min). Under NOM conditions, UV-L led to significant pore blocking because of the presence of high-MW NOM. In contrast, WA-L, which contains smaller and more hydrophobic NOM, caused minimal suppression. Despite NOM suppression, a PAC dose of 20 mg/L enabled all PACs (except mesoporous carbon) to achieve ≥85% MIB and ≥98% geosmin removal in WA-L and partially in BA-L. These results highlight the importance of selecting PACs based on pore structure and surface chemistry, as well as the need to adjust PAC dosage during post-wildfire events.