Recycling crayfish shell and waste activated sludge as biochar to in-situ enhance antibiotics removal from wastewater: Linking structure properties and reaction kinetics

Aquaculture water represents a substantial source of antibiotics in the environment, thereby implicating potential hazards to human health and ecological stability. Additionally, the cultivation of crayfish in such water exacerbates concerns regarding the management of shell waste. In this investigation, crayfish shells and waste activated sludge were repurposed as biochar for the in-situ mitigation of antibiotics elimination from aquaculture wastewater. Compared to crayfish biochar (C-BC) solely from crayfish shell, crayfish sludge biochar (CS-BC) significantly enhances the adsorption of typical antibiotics like tetracycline and ciprofloxacin by 50.3–77.1 %. Findings from kinetic and isotherm experiments suggest that antibiotics adsorption mainly involves physical pore filling, but sludge introduction shifts CS-BC towards chemical adsorption. Further analysis reveals that sludge introduction reduces biochar pore size, boosts specific surface area, and offers more active adsorption sites. Additionally, hydrogen bonding on hydroxyl groups and increased oxygen-containing functional groups enhanced antibiotic adsorption onto CS-BC surfaces. This research presents a promising strategy for addressing antibiotic pollution in aquatic environments while also improving the utilization of organic solid waste resources.