Dual heteroatom-doped porous biochar from chitosan/lignosulfonate gels for enhanced removal of tetracycline by persulfate activation: Performance and mechanism

Rational design of carbon material structures is essential for enhancing the performance of persulfate-based advanced oxidation processes (PS-AOPs) in water purification. In this study, a self-doping and self-templating strategy was devised to produce N, S co-doped biochar catalysts through pre-cryocrushing and carbonization procedures employing chitosan (N-source) and lignosulfonate (S-source) derived from biomass waste. The as-synthesized materials exhibited excellent performance in removing tetracycline (TC) through a synergistic process of adsorption and catalytic activation. Mechanistic studies confirmed that electron transfer serves as the primary pathway, while singlet oxygen plays an auxiliary role. Furthermore, the toxicity of the degradation system, the impact of the complex water matrix, and the reusability of the catalysts were thoroughly investigated. Overall, this work is devoted to the treatment and application of biomass waste, which provides a feasible method for synthesizing heteroatom-doped biochar and offers valuable insights into the critical role of heteroatom-doped carbocatalysts in non-radical activation of persulfate.