Novel calcium-rich biochar synthesis and application for phosphorus and amoxicillin removal from synthetic and urban wastewater: Batch, columns, and continuous stirring tank reactors investigations

This work examines the synthesis of a novel calcium rich biochar (MB-900) and its application for phosphorus (P) and amoxicillin removal from synthetic and treated urban wastewaters under static and dynamic conditions (laboratory column and continuous stirring tank reactors (CSTRs)). Characterization techniques show that MB-900 has an enhanced structural, textural and surface chemical properties. Besides, batch adsorption tests indicate that MB-900 has important P recovery capacity in comparison with various engineered biochars available in the literature. Furthermore, under dynamic conditions, MB-900 efficiently recovers P from both synthetic solutions and real wastewater effluent. Due to a higher residence time, P recovery in CSTR mode are 94.9 and 82.3 mg g⁻¹ for synthetic and urban wastewater, respectively. These values are 1.4, and 6.1 times higher than those obtained in column tests. Mechanism investigations shows that P recovery occurs through electrostatic interactions, complexation, and especially precipitation as hydroxyapatite. Under column and CSTR modes, AMX behaves like a conservative tracer and was not adsorbed by MB-900. Therefore, the resulting P-loaded biochar can be applied in agriculture as a slow release fertilizer without risks related to AMX adsorption/leaching by plants.