Synthesis and characterization of functionalized carbon nanofibers for efficient removal of highly water-soluble dextromethorphan and guaifenesin from environmental water samples

Abstract

Pharmaceutical residues in water and wastewater cause several environmental problems as well as health issues in living beings. This study demonstrates the preparation and functionalization of low-cost carbon nanofiber for the simultaneous removal of dextromethorphan (Dex) and guaifenesin (Gua) from aqueous solutions and real water samples. A batch procedure was followed to optimize the adsorption conditions, such as contact time, solution pH, sorbent mass, and temperature. The results showed a significant similarity among these drugs in terms of their adsorption behaviour. For pristine carbon nanofiber, the adsorption capacities were 119.0 mg/g and 73.5 mg/g for Dex and Gua, respectively. The adsorption capacities of functionalized carbon nanofiber were estimated to be 172.4 mg/g and 250.0 mg/g for Dex and Gua, respectively. Their adsorption kinetics were observed to fit well with the pseudo-second-order model. In addition, their adsorption isotherms were in good agreement with the Langmuir model. Furthermore, the thermodynamic parameters, including free energy, enthalpy, and entropy, were calculated and discussed. The carbon nanofibers exhibited significant potential in the removal of these pollutants from aqueous solutions and real environmental samples, especially at low temperatures. The removal efficiency from bottled water, tap water, and the Red Sea water were estimated at 96 %, 94 %, and 94 %, respectively. The recyclability of the adsorbents was investigated and discussed.