Effects of Chemical, Biological, and Physical Aging As Well As Soil Addition on the Sorption of Pyrene to Activated Carbon and Biochar

TLDR

The study evaluates the suitability of biochar and activated carbon for remediating contaminated soils by measuring pyrene sorption before and after aging, with and without soil. Biochar and activated carbon were aged alone or with soil using biological, chemical, and physical treatments, and their pH, elemental composition, cation exchange capacity, microporous surface area, and pyrene sorption isotherms were quantified. Chemical aging at 110 °C most strongly altered material properties, raising pH and CEC, while pyrene sorption remained high—log K values ranged 7.80–8.21 for AC and 5.22–6.21 for biochar—though chemical aging reduced sorption by up to 1.8 log units, yet both materials retained strong sorption capacity in soil and after harsh aging, supporting their use in contaminated land remediation.

Abstract

In this study, the suitability of biochar and activated carbon (AC) for contaminated soil remediation is investigated by determining the sorption of pyrene to both materials in the presence and absence of soil and before as well as after aging. Biochar and AC were aged either alone or mixed with soil via exposure to (a) nutrients and microorganisms (biological), (b) 60 and 110 °C (chemical), and (c) freeze-thaw cycles (physical). Before and after aging, the pH, elemental composition, cation exchange capacity (CEC), microporous SA, and sorption isotherms of pyrene were quantified. Aging at 110 °C altered the physicochemical properties of all materials to the greatest extent (for example, pH increased by up to three units and CEC by up to 50% for biochar). Logarithmic K(Fr) values ranged from 7.80 to 8.21 (ng kg(-1))(ng L(-1))(-nF) for AC and 5.22 to 6.21 (ng kg(-1))(ng L(-1))(-nF) for biochar after the various aging regimes. Grinding biochar to a smaller particle size did not significantly affect the sorption of d(10) pyrene, implying that sorption processes operate on the subparticle scale. Chemical aging decreased the sorption of pyrene to the greatest extent (up to 1.8 log unit for the biochar+soil). The sorption to AC was affected more by the presence of soil than the sorption to biochar was. Our results suggest that AC and biochar have a high sorption capacity for pyrene that is maintained both in the presence of soil and during harsh aging. Both materials could therefore be considered in contaminated land remediation.