Preparation of micro-mesoporous carbon from seawater-impregnated sawdust by low temperature one-step CO2 activation for adsorption of oxytetracycline

Porous carbons (PCs) were prepared from seawater (SW)-impregnated sawdust (SD) by CO2 activation at 700 °C. The preparation process was investigated on-line by thermogravimetric analyzer coupled with FTIR (TG-FTIR). PCs were characterized by N2-adsorption/desorption and Fourier transform infrared spectroscopy. The adsorption abilities of PCs for oxytetracycline (OTC) were compared and the adsorption isotherms of OTC on the optimum sample were studied. Results showed that SW impregnation led to the release of more CO from SD at 700 °C, indicating a higher degree of CO2 activation, thus a 81% higher BET surface area (SBET) can be achieved under the same activation condition. Mesopore volume of PC increased from 0.089 to 0.301 cm3 g−1 with the activation time increasing from 5 to 60 min. PC obtained after 60-min activation with a SBET of 490 m2 g−1 and an average pore diameter of 3.78 nm had the highest adsorption ability for OTC. Its adsorption equilibrium data for OTC followed Langmuir model with a maximum monolayer adsorption capacity up to 100 mg g−1.