Enhanced adsorption of Levofloxacin and Ceftriaxone antibiotics from water by assembled composite of nanotitanium oxide/chitosan/nano-bentonite.

A novel NBent-NTiO2-Chit nanocomposite has been synthesized from the crosslinking combination of nanotitanium oxide-chitosan (NTiO2-Chit) and nanotitanium oxide-bentonite (NTiO2-Bent) via formaldehyde. The characterization of NBent-NTiO2-Chit was confirmed by different instrumentations. The particle size (34-97 nm) and surface area (16.385 m2 g-1) were confirmed from the scanning electron microscopy and BET measurement, respectively. The FT-IR of NBent-NTiO2-Chit confirmed the presence of OH, N-H, Si-O-Al and Si-O-Si functional groups. Four thermal degradation steps were characterized from the TGA of NBent-NTiO2-Chit with a total loss = 23.514% in the temperature range 30-600 °C. The assembled nanocomposite enhanced the removal of two important classes of antibiotics including Levofloxacin (LEVO) Ceftriaxone (CFT) in the forms of Fluoroquinolone and Cephalosporin, respectively. The various factors that affected the percentage of extraction were applied and optimized such as pH, dosage, initial concentration of LEVO and CFT, contact time and interfering ions. Maximum percentage values of 90.2% (pH 4) and 93.5% (pH 5) for LEVO and CFT, respectively, were achieved at 10 min. The enhancement in removal percentage of LEVO to 92.4% was mainly established by increasing the dose of NBent-NTiO2-Chit to 60.0 mg. The extraction mechanisms of LEVO and CFT were positively explained by three models of adsorption isotherm including Langmuir, Freundlich and Temkin. The obtained correlation coefficients (R2) by Langmuir model were 0.952 and 0.987 for LEVO and CFT, respectively to offer excellent fit to the adsorption processes. The thermodynamics parameters of NBent-NTiO2-Chit were evaluated and referred that the reaction is spontaneous and endothermic. The kinetic studies of NBent-NTiO2-Chit with LEVO and CFT antibiotics were better fitted by the pseudo-second-order based on the acquired R2 values as 0.999 and 0.997 for LEVO and CFT, respectively. The results proved that the designed NBent-NTiO2-Chit was successively implemented for extraction of LEVO and CFT from industrial wastewater providing percentage values 83.2 and 79.0% using 10.0 and 150.0 ± 1.0 mg NBent-NTiO2-Chit, respectively.