Carbon dots inspired upgradable hierarchical carbon for enhanced tetracycline adsorption

Abstract

Lignin, a bulk waste byproduct from biorefining processes, possesses complex macromolecular structures that resist dissociation during thermal conversion. However, its propensity for condensation and carbonization makes it suitable for carbon material preparation. Nevertheless, the amorphous nature of lignin causes melting and flow during heating, which covers newly formed pores and results in underdeveloped pore structures in the resulting hierarchical carbons. In this study, an innovative pre-carbonization engineering strategy was proposed to break this barrier. By purposeful re-carbonization, partial lignin macromolecules were induced to form numerous micro-carbon dots, which effectively blocks the melting and flowing of lignin when heating, preventing the covering of newborn pores. The unstable interface between the carbonized phase and the lignin phase provides more active sites for pore development. Characterization results showed that the prepared carbon material exhibited hierarchical pore structure with an extremely high specific surface area. Furthermore, the optimal sample possessed the maximum BET surface area and adsorption capacity for tetracycline as 2246 m²/g and 1196 mg/g, representing 42.77 % and 23.15 % enhancements respectively compared to hierarchical carbon derived from raw lignin. In conclusion, the lignin-based hierarchical carbon material developed in this study provides a simple, economical, and efficient method for the removal of antibiotics in wastewater treatment, contributing to water pollution control.