Synthesis, characterization, and tetracycline adsorption behavior of activated carbon dopped alginate beads: Isotherms, kinetics, thermodynamic, and adsorption mechanism

The main aim of the current work is to test the tetracycline adsorption behavior of activated carbon (AC) dopped alginate (ALG) beads. In this way, synthesis and characterization of activated carbon dopped alginate beads using Fourier-transform infrared, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy, Brunauer–Emmett–Teller, X-ray photoelectron spectroscopy analysis, adsorption equilibrium, kinetics, thermodynamics, adsorption mechanism, desorption, and reusability experiments were carried out. Maximum tetracycline removal percentage was achieved using 200 mg of AC-ALG beads with a ratio of 3.0% (w/v) within 6 h at pH 7.0, and tetracycline removal performance was determined to be 100.0%. The Langmuir, Freundlich, Dubinin– Radushkevich, Temkin, Halsey, and Harkins–Jura isotherm models were applied to experimental data. AC-ALG-(1.0 and 2.0) beads were found to fit the Langmuir model well, while AC-ALG-3.0 beads fitted the Freundlich model. Adsorption kinetics were investigated by pseudo-first-order, pseudo-second-order, Elovich, Weber–Morris intraparticle diffusion, and Bangham models and the pseudo-second-order kinetic model fitted the adsorption data well. The thermodynamic parameters were calculated, and the enthalpy of tetracycline adsorption was endothermic for all beads. After the adsorption process, the beads can easily be regenerated by NaOH and effectively reused within five cycles. It can be concluded that activated carbon dopped alginate beads have a considerable potential on the adsorption of pharmaceutical compounds from wastewater.