Remediation of tetracycline from aqueous solution through adsorption on g-C3N4-ZnO-BaTiO3 nanocomposite: Optimization, modeling, and theoretical calculation

•Removal of tetracycline using the g-C3N4-ZnO-BaTiO3 nanocomposite.•The novel developed material has a maximum adsorption capacity of 218.59 mg g−1.•DFT calculation used to clarify some properties of nanocomposite.•The g-C3N4-ZnO-BaTiO3 nanocomposite is reusable for 4 consecutive cycles. This study's goal is to treat atetracycline (TC) antibiotic containing water with a graphitic carbon nitride (g-C3N4) based composite zinc oxide (ZnO)-barium titanate (BaTiO3) nanoparticles (g-C3N4-ZnO-BaTiO3) prepared from the extract of Olea Europaea leaves as an initiator under the ultrasound method. The FTIR, XRD, XPS, SEM, and TEM analyses were used for g-C3N4-ZnO-BaTiO3 nanocomposite. Response surface methodology-Box-Behnken design (RSM-BBD) was used to design the experiment and optimize the process parameters. TCadsorption ability of theg-C3N4-ZnO-BaTiO3was evaluated and optimized by varying the pH, contact time, and initial TC solution concentration. RSM results demonstrated thatg-C3N4-ZnO-BaTiO3nanocompositeeffectively improves the adsorption performance ofg-C3N4-ZnO-BaTiO3with optimal adsorption capacity of209.19 mg g−1atpH = 4.59 and for 180 min of contact time, and 60 mgL–1of TC concentration.The whole adsorption process applies to the pseudo-second-order kinetics and theFreundlichisotherm model describes the best adsorption behavior of g-C3N4-ZnO-BaTiO3. Various characterization methods and zeta potential show the mechanism of adsorption of g-C3N4-ZnO-BaTiO3toward TC, involving hydrogen bonds, electrostatic action, and π-π interactions. The quantum chemical calculations based on electrostatic potential maps, HOMO–LUMO distributions, and energy gaps showed that TC forms a stable cluster with g-C3N4-ZnO-BaTiO3, indicating its favorable adsorption. This indicates that theg-C3N4-ZnO-BaTiO3nanocomposite is an admirable adsorbent to remove antibiotics from water.