Rational design of in-situ-modified resorcinol formaldehyde aerogels for removing chlortetracycline antibiotics from aqueous solutions

Organic resorcinol formaldehyde aerogels with distinct pore sizes/surface areas in different ratios of (resorcinol/catalyst) R/C = 300, 400, 600 and (resorcinol/water) R/W = 2 were prepared utilizing sol-gel technique and in-situ modified by incorporating 1 wt% meta-phenylenediamine. The porous nanostructure, surface area, and pore size of the aerogels were characterized by scanning electron microscopy, Brunauer-Emmett-Teller, and Barrett-Joyner-Halenda techniques. Raman spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction were employed to get understanding into the chemical structure. Furthermore, we investigated the removal percentage of antibiotic via UV-vis spectroscopy. The ability of modified aerogels in removing chlortetracycline (CTC) at different pH values (2-12), contact times (2-24 h), initial concentrations of CTC (50-100 mg L-1), and the adsorbent dose (2-10 mg) was evaluated. Consequently, the adsorption optimum conditions were found, the adsorption isotherms were measured, and isotherm models were fitted to the results to interpret the kinetics of adsorption. The obtained fitting parameters using the pseudo-second-order model revealed a well alignment with the experimental data. Finally, we demonstrated that the modified-aerogels have a high capacity in CTC antibiotics removal up to 90% and an adsorption capacity of 440 mg g(-1) as well as an efficient regeneration capacity for five consecutive cycles without significant degradation of the adsorption properties.