Highly performant biochar prepared <i>via</i> co-activation designed for the removal of antibiotics

Antibiotics in water bodies pose a serious threat to the ecosystem and human health, necessitating the development of environmentally friendly and sustainable adsorbents for water purification. This paper proposes a novel ratio of adsorbents K2FeO4, KHCO3, and rice straw (RS) in composites. The synergistic co-activation of K2FeO4 and KHCO3 significantly enhances the adsorption performance through surface modification and porosity development, which is 4.21 times that of the original biochar (BC). The adsorption behavior of the composites under different conditions was investigated by varying the adsorbent dosage, tetracycline hydrochloride (TH) concentration, and pH. The removal rate of TH in water by magnetic materials is 85.93%, an increase of 65.54% compared with the original BC. The removal performance of 1RS-2Fe-1K was better than most adsorbents, and its adsorption performance in real water was also satisfactory. The removal rate of TH in all water bodies was above 80%. A fixed bed column experiment revealed that 1RS-2Fe-1K was suitable for the continuous adsorption of TH in an aqueous medium, which was completed after 1,840 min. Washing with deionized water improves the protonation of functional groups and layer-by-layer exposure of the composite structure in 1RS-2Fe-1K. It also improves the reusability of the composite. Repeated use tests confirmed a retention rate of 50.81% after five cycles. From an economic perspective, using agricultural waste as a feedstock reduces raw material costs, while the co-activation process ensures high adsorption efficiency with minimal additional inputs. Environmentally, this approach minimizes waste and promotes sustainable water treatment. This study provides a new perspective on utilizing agricultural waste composites as sustainable adsorbents, offering a cost-effective and environmentally friendly solution for the removal of antibiotics from water.