Preparation of a microbial char adsorbent from polyethyleneimine-modified and nickel-loaded microorganisms for efficient removal of metronidazole

Abstract

Biochar has become a frontier of research in recent years and has broad potential for application in antibiotic adsorption. In this work, we used a polyethyleneimine-modified microbial residue as a carrier and synthesized a microbial char adsorbent (Ni-MMC) for removing metronidazole (MNZ) by adsorption of Ni(II) and pyrolysis reduction. We investigated the effects of pyrolysis conditions, initial pH value, reaction time and temperature, MNZ concentration, anion species and concentration on the adsorption performance of Ni-MMC and studied its desorption and cycling performance. The results showed that Ni-MMC could adsorb MNZ rapidly, and the adsorption efficiency reached 87.62% in the 3rd min and 93.78% in the 15th min, and the adsorption capacity reached 46.73 mg g⁻¹ in the 15th min. Methanol showed the best desorption of MNZ on Ni-MMC with 99.99% desorption within 6 h. After five adsorption–desorption cycles, Ni-MMC could maintain 95.65% of its initial adsorption capacity. The pseudo-second-order kinetic model and Langmuir model well described the adsorption process of MNZ on Ni-MMC. Thermodynamic studies have shown that the adsorption process was exothermic and spontaneous. We used various analytical techniques to characterize Ni-MMC. Overall, as a product recycled from waste microbial residues, Ni-MMC is a promising adsorbent for efficient and reproducible removal of antibiotics.