Trichloroethylene adsorption by pine needle biochars produced at various pyrolysis temperatures.

In this study, pine needles were converted to biochar (BC) at different pyrolysis temperatures of 300, 500, and 700 °C to sorb trichloroethylene (TCE), and the changes in BC properties with each temperature were evaluated. Pyrolysis temperature showed a pronounced effect on BC properties. Decreases in molar H/C and O/C ratios resulted from removing O- and H-containing functional groups with increasing temperature, and produced high aromaticity and low polarity BCs. BCs produced at higher temperature showed greater TCE removal efficiency from water due to their high surface area, micro-porosity, and carbonized extent. The performance of various BCs for TCE removal was assessed by the Freundlich, Langmuir, Temkin, and Dubinin-Radushkevich adsorption models, among which the Temkin and Dubinin-Radushkevich models best described TCE adsorption onto various BCs, indicating prevailing sorption mechanism as pore-filling.