Chemical-free fabrication of carbon fiber aerogels from egg boxes for the removal of pharmaceutically active compounds in aqueous solution

Abstract

The presence of pharmaceuticals and personal care products (PPCPs) in aquatic environments extremely concerns to human health and the ecosystem; thus, their removal is essential. This work produced carbon fiber aerogels from egg box waste using a chemical-free fabrication process. The pyrolyzed egg box aerogel (PEBA) exhibited three-dimensional interconnected carbon nanofibers with high surface area and pore volume. The adsorption capacity and removal efficiency of four PPCPs, namely, diclofenac (DIC), caffeine (CF), tetracycline (TC), and ciprofloxacin (CIP), from water were high and comparable to other carbon-based adsorbents, and the adsorption time was much faster (within 20 min). The Redlich-Peterson and the pseudo-second-order models were the best-fitted isotherm and kinetic models, respectively, which imply multilayer adsorption at high concentrations and the chemisorption process. Furthermore, mechanisms responsible for the adsorption of all PPCPs were elucidated. PEBA was applied in the fixed-bed column experiment to mimic the continuous adsorption process. In addition, PEBA was recyclable after low-temperature heat treatment. The adsorption capacity (8.1 mg/g) and removal efficiency (94.03 %) for TC was still high after three cycles. Metabolomics analysis revealed that no secondary pollution is released into water after thermal treatment. Therefore, PEBA has the potential as an efficient adsorbent for removing PPCPs from water.