Valorization of biochar and lignin derived from the NaOH pretreatment of lignocellulosic biomass for applications as an adsorbent and antioxidant.

In this study, oak and larch pretreated with NaOH were carbonized, and the suitability of their physical and chemical properties for ibuprofen adsorption was analyzed. Lignin (NaOH-L) was also separated from the liquid fraction generated after NaOH pretreatment, and its antioxidant activity was evaluated. The biochar yield of pretreated biomass was higher than the of raw material, and the biochar yield from larch (28.76–34.81%) was higher than that from oak (26.62–28.35%). The carbon content of the biochar was also higher than that of the raw material, while the oxygen content decreased on the biochar. The biochar obtained from oak exhibited its highest specific surface area (403.18 m2/g) when pretreated with 2% NaOH, whereas the larch biochar had its highest specific surface area (481.18 m2/g) when prepared using the raw material. The larch biochar exhibited a higher ibuprofen removal efficiency than did the oak biochar, with the Freundlich isothermal model most accurately describing the ibuprofen adsorption behavior. Furthermore, larch exhibited a higher NaOH-L recovery yield (16.98 and 21.93%) than oak (5.83 and 15.02%). The NaOH-L from larch (IC 50 for DPPH and ABTS of 0.49–1.03 and 0.04–0.06, respectively) had a higher antioxidant activity than that of oak (IC 50 for DPPH and ABTS of 1.77–2.68 and 0.39–0.53, respectively). The removal rate of ibuprofen was high for larch biochar following a 4% NaOH pretreatment. Additionally, the antioxidant activity was high for the recovered lignin under the same conditions. [Display omitted] • The biochar yield increased as the NaOH concentration increased. • The ibuprofen removal efficiency of larch biochar is higher than that of oak biochar. • The recovery yield of lignin derived from the NaOH pretreatment of larch was high. [ABSTRACT FROM AUTHOR]