Enhanced adsorption capacity of antibiotics by calamus-biochar with phosphoric acid modification: Performance assessment and mechanism analysis

•A mesoporous calamus biochar with average pore size of 5.14 nm was obtained.•The specific surface area was 797 m2·g−1 by phosphoric acid modification.•The maximum adsorption capacity for SMX and ERY was 216 and 325 mg·g−1.•The adsorption of ERY is pH and coexisting matrixes insensitive.•Complexation, π-π interaction, and pore filling were the key roles in adsorption. Adsorption is one of the effective methods to remove antibiotics from water. Plant-based biochar can be effectively modified to enhance the adsorption capabilities of antibiotics. Calamus biochar (PBC) was modified by phosphoric acid to study its adsorption efficacy on erythromycin (ERY) and sulfamethoxazole (SMX). PBC had a pore density of 0.771 m3·g−1, an average pore size of 5.14 nm, and an enormous surface area of 797 m2·g−1. PBC had been shown to incorporate a substantial quantity of functional groups containing oxygen by FTIR and XPS investigations. With these surface chemical and physical characteristics, PBC adsorbed 325 mg·g−1 of ERY and 216 mg·g−1 of SMX, which was tenfold higher compared to that of unmodified biochar and industrial-activated carbons. Quantitative analysis of adsorption mechanisms showed that the adsorption of ERY by PBC mainly included oxygen-containing functional group complexation and pore filling, whereas, the π-π interaction and pore filling were the leading mechanisms in the adsorption process of SMX. This research offers insights into the preparation of plant biochar with excellent antibiotic adsorption performance. [Display omitted]