Study on the adsorption performance of modified kaolin/corn straw biochar for oxytetracycline and chlortetracycline

Abstract

As typical antibiotic pollutants, oxytetracycline (OTC) and chlortetracycline (CTC) are widely present in water bodies and difficult to degrade naturally, posing potential threats to ecosystems and human health. To address this issue, this study successfully prepared two novel types of kaolin/corn straw biochars through high-temperature pyrolysis and nanoparticle modification, and investigated their adsorption performance for OTC and CTC in water. The characterization results showed that the two modified biochars had a high specific surface area and developed pore structures, which were conducive to improving adsorption efficiency. The batch adsorption experiments showed that the nano-CuFe₂O₄ modified biochar (KLBCCF) was superior to the nano-CuO modified biochar (KLBCC) in terms of adsorption capacity, interference resistance, and regeneration performance. The pseudo-second-order kinetic model and the Langmuir model can better fit the OTC and CTC adsorption processes by KLBCCF. At 318.15 K, the adsorption capacities of KLBCCF for OTC and CTC were determined to be 170.21 and 316.26 mg g⁻¹, respectively. The thermodynamic analysis showed that the adsorption process was spontaneous, heat-absorbing, and entropy-increasing. The adsorption mechanisms of OTC and CTC on KLBCCF included pore filling, hydrogen bonding, surface complexation, electrostatic interactions, and π–π interactions. This study promotes the development process of efficient adsorbents and provides a theoretical basis for the effective removal of antibiotics.