Instantaneous oxidation of levofloxacin as toxic pharmaceutical residuals in water using clay nanotubes decorated by ZnO (ZnO/KNTs) as a novel photocatalyst under visible light source.

Kaolinite nanotubes were synthesized by a simple scrolling process and decorated by ZnO nanoparticles as a novel nanocomposite (ZnO/KNTs). The synthetic ZnO/KNTs composite was characterized as an effective photocatalyst in the oxidation of levofloxacin pharmaceutical residuals in the water resources. The composite displays a surface area of 95.4 m2/g, average pore diameter of 5.8 nm, and bandgap energy of 2.12 eV. It is of high catalytic activity in the oxidation of levofloxacin in the presence of visible light source. The complete oxidation for 10 mg/L of levofloxacin was recognized after 55 min, 45 min, and 30 min with applying 30 mg, 40 mg, and 50 mg of ZnO/KNTs as catalyst dosage, respectively. Additionally, it achieved complete oxidation for 20 mg/L and 30 mg/L of levofloxacin after 45 min and 75 min, respectively using 50 mg as catalyst dosage. The degradation efficiency was confirmed by detecting the residual TOC after the treatment tests and the formed intermediate compounds were identified to suggest the degradation pathways. In addition to the oxidation pathway, the mechanism was evaluated based on the active trapping tests that proved the dominance of hydroxyl radicals as the essential active species. Finally, the ZnO/KNTs composite is of promising recyclability properties and achieved better results than several studied photocatalysts in literature.

Promoting the decontamination of different types of water pollutants (Cd2+, safranin dye, and phosphate) using a novel structure of exfoliated bentonite admixed with cellulose nanofiber.

Exfoliated bentonite sheets admixed with nano-cellulose fibers (EXB/CF) were prepared as advanced bio-composite of enhanced decontamination properties for different species of water pollutants (Cd2+, safranin dye, and phosphate). The composite achieved promising adsorption capacities with experimental values of 206.8 mg/g (Cd2+), 336 mg/g (safranin), and 296 mg/g (phosphate); and predicted maximum capacities of 212.9 mg/g (Cd2+), 341 mg/g (safranin), and 305 mg/g (phosphate). The adsorption systems for the three species follow the Freundlich isotherm model and Pseudo-First order as kinetic model considering both the linear and nonlinear fitting demonstrating heterogeneous and multilayer uptake properties of physisorption type. The operation of physisorption mechanisms was supported by the obtained adsorption energies from D-R model that are less than 8 kJ/mol as well as the calculated free energies and enthalpies. The thermodynamic investigation revealed the nature of the adsorption reactions of the three pollutants by EXB/CF as exothermic, favorable, and spontaneous reactions. The EXB/CF composite also is of significant recyclability value and applied in five decontamination reusing runs for Cd2+, safranin dye, and phosphate achieving promising removal percentages.