Sustainable biochar-MOF composites for the removal of tetracycline: Insights into batch and continuous studies

This study focuses on the development of advanced biochar-based composite materials for the efficient removal of tetracycline (TC) from aqueous systems. Bread waste was repurposed as a sustainable biomass source to produce biochar, which was further modified with ZIF-67, a cobalt-based metal-organic framework (MOF), to enhance its adsorption performance. Two synthesis routes were employed: direct calcination to produce non-activated biochar (NAC) and chemical activation with potassium carbonate to produce activated biochar (AC). Batch adsorption studies revealed that NAC-30MOF exhibited the highest adsorption capacity, achieving nearly 100 % TC removal with a maximum capacity of 2033 mg⋅g −1 and a BET surface area is 514.78 m 2 ⋅g −1 with a pore size of 3.83 nm. Adsorption kinetics were best described by the pseudo-second-order model (R 2 = 0.995), indicating chemisorption as the dominant mechanism. Thermodynamic analysis confirmed the endothermic and spontaneous nature of the adsorption process, with positive enthalpy (ΔH°) and entropy (ΔS°) values. Column studies demonstrated the superior performance of NAC-30MOF, with longer breakthrough and exhaustion times compared to AC and NAC, highlighting its potential for continuous water treatment applications. Additionally, NAC-30MOF retained excellent reusability, maintaining nearly 100 % removal efficiency over three adsorption-desorption cycles. This work highlights the effectiveness of MOF-modified biochar composites, particularly NAC-30MOF, as cost-effective and sustainable adsorbents for water treatment. The integration of biochar with MOFs significantly enhances adsorption capacity and efficiency, offering a promising approach to the development of advanced materials for environmental remediation. • Sustainable biochar produced from bread waste using non-activated and activated methods. • ZIF-67 MOF modification significantly enhanced biochar's adsorption capacity for tetracycline. • NAC-30MOF achieved the highest adsorption capacity of 2033 mg·g −1 with 100 % removal efficiency. • NAC-30MOF demonstrated excellent reusability over three adsorption-desorption cycles. • Column studies confirmed NAC-30MOF's superior performance for continuous water treatment applications.