Effect of Oxyfluorination of Activated Carbon on the Adsorption of Tetracycline from Aqueous Solutions

Oxyfluorination treatment was used to enhance the capacity for adsorption of tetracycline (TC) from aqueous systems by activated carbon (AC). The AC was oxyfluorinated at room temperature for 5 min in a batch reactor, and the ratio of O₂ and F₂ gas was used as a variable. The oxyfluorination treatment increased the oxygen functional group content on the AC by up to 19.4%. The specific surface area of the oxyfluorinated AC was decreased by up to 31.7% and the micropore volume was decreased by up to 30.6% due to strong etching by fluorine radicals. AC-O7F3 with a 19.4 at% oxygen group content showed the best TC adsorption performance because the increased number of oxygen functional groups enabled hydrogen bonding. However, the AC-O5F5 sample treated with a high fluorine partial pressure showed poor TC adsorption, which was attributed to the collapse of the pore structure and a decrease in the specific surface area due to perfluorination. Meanwhile, the TC adsorption process showed pseudo second-order kinetics and a good fit with the Langmuir model.