Preparation of Chitosan-Modified Bentonite and Its Adsorption Performance on Tetracycline

[Image: see text] In this study, chitosan-modified bentonite was synthesized using the coprecipitation method. When the Na(2)CO(3) content was 4% (weight of soil) and the mass ratio of chitosan to bentonite was 1:5, the adsorption performance of the chitosan/bentonite composite was best. The adsorbent was characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and Brunauer–Emmett–Teller measurement. Various characterization results demonstrate that chitosan successfully entered the bentonite interlayer and increased layer spacing but did not modify bentonite’s laminar mesoporous structure, and the −CH(3) and −CH(2) groups of chitosan appeared on chitosan-modified bentonite. Tetracycline was used as the target pollutant in the static adsorption experiment. The adsorption capacity was 19.32 mg/g under optimal conditions. The adsorption process was more consistent with the Freundlich model and the pseudo-second-order kinetic model, indicating that it was a nonmonolayer chemisorption process. The adsorption process is a spontaneous, endothermic, entropy-increasing process, according to thermodynamic characteristics.