Chitosan crosslinked composite based on corncob lignin biochar to adsorb methylene blue: Kinetics, isotherm, and thermodynamics

Methylene blue (MB) in industrial wastewater is a potential threat to human health and environment and the removal of methylene blue attracts wide attention. In this study, corncob lignin was carbonized at 400 °C and cross-linked with chitosan in the presence of epichlorohydrin to prepare a composite (CS-BC), and the adsorption behavior was discussed by using MB as adsorbate. Its removal of methylene blue reached 99.96% with a maximum adsorption capacity of 499.8 mg/g, and the adsorption behavior was in accordance with the Langmuir model. The fitness of pseudo-second-order kinetic model conceded that chemisorption played a major role. Compared with unmodified biochar, the adsorption capacity of CS-BC was increased by ~2 times. CS-BC had good recyclability and was easy to separate from water, which maintained excellent absorption performance after 5 cycles. The excellent adsorption capacity and recycling performance of CS-BC provide a prospect way to eliminate methylene blue from industrial effluents. • Lignin waste released from bioethanol production was used as biochar feedstock. • Chitosan modified lignin-biochar composite was applied to remove methylene blue. • The possible adsorption mechanism of adsorbent composite was proposed. • The maximum adsorption capacity of adsorbent reached 499.8 mg/g.