Antibiotics are the most common pharmaceutical compounds, and they have been extensively used for the prevention and treatment of bacterial diseases for more than 50 years. However, merely a small fraction of antibiotics is metabolized in the body, while the rest is discharged into the environment through excretion, which can cause potential ecological problems and human health risks. In this study, the elimination of seventeen antibiotics from real livestock wastewater effluents was investigated by UV/TiO₂ advanced oxidation process. The effect of process parameters, such as TiO₂ loadings, solution pHs, and antibiotic concentrations, on the efficiency of the UV/TiO₂ process was assessed. The degradation efficiency was affected by the solution pH, and higher removal efficiency was observed at pH 5.8 and 9.9, while the catalyst loading had no significant effect on the degradation efficiency at these experimental conditions. UV photolysis showed a good removal efficiency of the antibiotics. However, the highest removal efficiency was shown by the UV/photocatalyst system due to their synergistic effects. The results showed that more than 90% of antibiotics were removed by UV/TiO₂ system during the 60 min illumination, while the corresponding TOC and COD removal was only 10 and 13%, respectively. The results of the current study indicated that UV/TiO₂ advanced oxidation process is a promising method for the elimination of various types of antibiotics from real livestock wastewater effluents.

Organochlorine compounds (OCs) are very toxic, highly persistent, and ubiquitous contaminants in the environment. Degradation of lindane, a selected OC, by simulated solar light-activated TiO₂ (SSLA-TiO₂) photocatalysis was investigated. The film types of the TiO₂ photocatalyst were prepared using a dip-coating method. The physical properties of the films were investigated using X-ray diffraction, transmission electron microscopy, and environmental scanning electron microscopy. The SSLA-TiO₂ photocatalysis led to a lindane removal of 23% in 6 h, with 0.042 h⁻¹ of an observed pseudo first-order rate constant (k_obs). The SSLA-TiO₂ photocatalysis efficiency was greatly enhanced by adding hydrogen peroxide (H₂O₂), persulfate (S₂O₈²⁻), or both combined, corresponding to a 64%, 89%, and 99% lindane removal in the presence of 200 µM of H₂O₂, S₂O₈²⁻, or equimolar H₂O₂-S₂O₈²⁻, respectively. The hydroxyl and sulfate radicals mainly participated in lindane degradation, proven by the results of a radical scavenger study. The degradation kinetics were hindered in the presence of the water constituents, indicated by a 61%, 35%, 50%, 70%, 88%, and 91% degradation of lindane in 6 h, using a SSLA-TiO₂/S₂O₈²⁻/H₂O₂ photocatalysis system containing 1.0 mg L⁻¹ humic acid (HA), or 1 mM of CO₃²⁻, HCO₃⁻, NO₃⁻, SO₄²⁻, and Cl⁻, respectively. The TiO₂ film demonstrated high reusability during four runs of lindane decomposition experiments. The SSLA-TiO₂/S₂O₈²⁻/H₂O₂ photocatalysis is very effective for the elimination of a persistent OC, lindane, from a water environment.

Photocatalysis is a promising process for decomposing harmful organic pollutants in water. In this study, solar/photocatalytic degradation of two model azo dyes, i.e., methylene blue (MB) and methyl red (MR), in water usinga nanostructured chitosan-modified nickel magnetite (CS-NM) bio-composite was investigated. The CS-NM bio-composite was synthesized through a co-precipitation method and characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), thermogravimetry (TGA), and UV-Vis spectroscopy. FTIR analysis showed the uniform incorporation and conjugation of nickel magnetite (NM) into the chitosan (CS) polymer matrix. SEM showed that the average particle size was 0.5 μm. The TGA results revealed the good thermal stability of the prepared bio-composite at 300 °C. The point of zero charge was calculated as 7.5. The effect of water quality and process parameters, such as concentration of dyes, catalyst dose, solution pH, and temperatures, was investigated, for application purposes. The solar/CS-NM photocatalysis resulted in 99 and 96% degradation of individual MB and MR (C₀ = 50 ppm), respectively, in 90 min. The degradation of MB and MR by solar/CS-NM photocatalysis followed pseudo-first-order kinetics, with observed rate constants (k) of 0.077 and 0.072 min⁻¹, respectively. The CS-NM photocatalyst showed high recyclability, represented by only a 4–6% loss in the photocatalytic efficiency, after four cycles. The results showed that solar/CS-NM photocatalysis is an efficient technique for degrading recalcitrant organic pollutants, such as azo dyes, in water environments.