In this study, a self-organized nanotubular titanium dioxide (TiO₂) array was successfully produced by anodizing pure titanium in a mixture of glycerol, distilled water (8 vol.), and ammonium fluoride using a dual electrode system. The size control and distribution of the nanopores were performed in a DC voltage range varying from 30V to 60V. The diameter of TiO₂ nanopores varies from 59 to 128nm depending on the anodizing voltage. Energy-dispersive X-ray spectroscopy (EDX) analysis reveals that the as-prepared films are essentially composed of TiO₂. According to the X-ray diffraction (XRD) and Raman spectroscopy analysis, the nanotubular arrays of TiO₂ annealed at 600C for 2 hours are composed of a phase mixture of anatase and rutile. Mott-Schottky analysis showed that the TiO₂ nanotubes are consistent with an n-type semiconductor with a donor density of about 10¹⁷cm^-3. Preliminary results on the photocatalytic degradation of a pharmaceutical pollutant showed that the TiO₂ nanotubes can be used as a promising material for application in wastewater treatment.

Walnut shells were used to produce highly microporous activated carbon. The prepared activated walnut shells were found to be an efficient adsorbent for removing Cr(VI). The study used the response surface methodology to investigate four independent variables effect: Cr(VI) concentration, pH, AC-Ws dose, and temperature on the Cr(VI) removal efficiency, which was studied in the concentration range of 0.1 to 0.3 g/L, 4 to 10, 15 to 35 °C and 1 to 5 mg/L, respectively. Through experiments designed, the optimum conditions were determined to be 4, 0.23 g/L, 298 k, and 2 g/L, respectively. At these conditions, the efficiency of removal was found to be 93%. The thermodynamic study of the adsorption process showed a spontaneous and exothermic nature. The kinetic model that explains the experimental data is the pseudo-second-order model. Furthermore, the Langmuir isotherm model was estimated to be an excellent representation of the equilibrium data. Quantum calculations and NCI analyses were also performed to get more light on the adsorption mechanism of the Cr(VI) atom and its complex form on the prepared AC-Ws surface.