Activated carbon embedded alginate beads for removing nonsteroidal anti-inflammatory drug naproxen from wastewater: Equilibrium, kinetics, thermodynamics, desorption, and reusability

In the present study, activated carbon/alginate (AC/ALG) beads were successfully synthesized with different AC:ALG ratios of 1.0-3.0 (w/v) and used for the adsorption of the nonsteroidal anti-inflammatory drug naproxen from wastewater. The beads were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) analysis, and adsorbent dosage, initial pH, initial naproxen concentration, and contact time in removal efficiency were investigated. Maximum naproxen removal percentage was achieved using 350 mg of AC/ALG beads with a ratio of 3.0% (w/v) within six hours and naproxen removal performance was determined to be 98.0%. Freundlich, Temkin, and Dubinin-Radushkevich (D-R) isotherm models were fitted to the equilibrium data better than the Langmuir model. According to kinetics results, the equilibrium time for the AC/ALG beads was reached in four hours and the kinetic model was determined by the pseudo-second-order equation. The thermodynamic parameters were calculated and enthalpy of naproxen adsorption was found to be positive for all AC/ALG beads. After the adsorption process the beads can easily be regenerated by ethanol and reused within seven cycles.