Strong adsorption of tetracycline on carbon blacks: An in-depth study of the adsorption mechanism

The adsorption process of tetracycline (TC) on different types of carbon black (CB) was investigated. The CB materials were characterized in detail to determine their physicochemical properties. BET analysis yielded specific surface areas of 842.99 m 2 /g and 1362.92 m 2 /g for CB-A and CB-B, respectively. The results were fitted using kinetic and isothermal models, and then assessed using AICc. It was found that, the pseudo-second-order kinetic model provided a satisfactory fit, with R 2 values of 0.9840 for CB-B and 0.8759 for CB-A. The Langmuir adsorption isotherm was the best fit, with R 2 values of 0.9683 for CB-B and 0.9906 for CB-A, and saturated adsorption amounts of 654.06 mg/g and 427.46 mg/g, respectively. Density Functional Theory (DFT) was used to analyze the electrostatic potential distribution and the magnitude of the adsorption energy, with a theoretical adsorption energy of −0.526 Ha and an interaction distance of 3.835 Å. Specific surface area and pore size also had an effect on the adsorption amount. The strong adsorption properties found in CB make it a very promising adsorbent, and this study provides a new idea for the study of antibiotic adsorption by CB and its mechanism.