Enhanced Photocatalytic Removal of Methylene Blue From Seawater Under Natural Sunlight Using Carbon-Modified n-TiO2 Nanoparticles

Abstract

In this study, photocatalytic removal of methylene blue (MB) from natural seawater was examined using carbon-modified titanium oxide (CM-n-TiO 2 ) nanoparticles under illumination of real sunlight. CM-n-TiO 2 nanoparticles exhibited significantly higher photocatalytic degradation efficiency compared to unmodified n-TiO 2 . Photocatalytic removal studies were carried out at different initial dye concentrations (5-30 µM), catalyst dose (0.5-1.5 gL -1 ), and pH (3-9). The highest removal rate of MB was obtained at the optimal conditions of pH 8 and 1.0 gL -1 of CM-n-TiO 2 . The solar photocatalytic removal of MB from seawater using CM-n-TiO 2 obeyed a pseudo-first order kinetics according to the Langmuir-Hinshelwood model.

Influence of Dissolved Ions on the Water Purification Performance of TiO2-Impregnated Porous Silica Tubes

“…As this was expected to be due to the presence of ions, the Contrex water was treated by passing it through various ion-exchange resins to remove anions, cations, or all ions from the solution, thus influencing the solution pH. As it has been previously reported that solution pH is a critical factor in determining the photocatalytic adsorption and degradation of organic compounds [7,[16][17][18], we expected that the large difference between the pH values of the anion-free and cation-free Contrex solutions (see Table 1) would influence the photocatalytic ability of the TiO 2 in our system. As shown in Figure 5, the photocatalytic degradation of 20 µM methylene blue in each solvent system was determined by measurement of the absorbance at 663 nm, which corresponds to the adsorption peak of methylene blue.…”

“…It was also reported that, at high pH values (>8), the formation of carbonate ions (OH • radical scavengers) was increased, which also reduced the efficiency of the photodegradation process. Thus, an optimum pH of 8 was recommended [17]. Furthermore, Guillard et al reported that the increase in the photocatalytic efficiency of TiO 2 at basic pH values was mainly attributable to an increase in the surface density of TiO − adsorption sites, which attract methylene blue because of its cationic character [4].…”