Aeration-assisted removal of tetracycline from wastewater by biochar: mechanisms and cost-benefit analysis

Abstract

The synergistic removal of antibiotics from wastewater by biochar adsorption and degradation under aeration-driven conditions is limited so far, and its feasibility has not been evaluated through a cost-benefit analysis. This study systematically investigated the removal of tetracycline by four biochars such as peanut shell biochar (PSB), rice straw biochar (RSB), sewage sludge biochar (SSB), and putrescible waste biochar (PWB) from wastewater under aeration conditions, then explored their mechanisms and key influence factors. Furthermore, a rigorous cost-benefit analysis was conducted to assess the economic feasibility of the aeration-assisted biochar method. Results showed that the tetracycline removal efficiency of biochar under aeration was significantly higher than that under anaerobic conditions, with SSB achieving the highest efficiency (86.9 %). Tetracycline underwent substantial degradation with the rate of SSB (16.7 %) > RSB (10.7 %) > PWB (7.8 %) > PSB (4.4 %), which was primarily driven by aeration-induced hydroxyl radicals (·OH) through oxidation of double bonds, loss of dimethylamino groups, dehydration, oxidation of aromatic rings, and cleavage of carbon rings. The impacts of aeration intensity, biochar dosage, pH, ionic strength, ammonium nitrogen, and oxygen-consuming organic compounds on the removal varied with biochar types. The tetracycline removal by SSB was minimally affected by solution composition, with high efficiency in simulated wastewater and stable regeneration performance. Furthermore, the aeration-assisted SSB method exhibited the highest economic benefits for tetracycline removal, costing 49.8 USD kg⁻¹ compared to chemically modified biochar (77.9–1791.7 USD kg⁻¹) and biochar-based advanced oxidation (78.9–202.4 USD kg⁻¹). This study highlights the viability of aeration-assisted biochar for tetracycline removal in wastewater.