Ag/Cr-TiO2 and Pd/Cr-TiO2 for Organic Dyes Elimination and Treatment of Polluted River Water in Presence of Visible Light

Abstract

In this work, photocatalytic materials constituted by Cr-doped TiO2 (Cr-TiO2) decorated with noble metals show high effectiveness in the mineralization of Acid Orange 7 (AO7) and in the disinfection of real river water. The materials were firstly obtained by sol-gel method to get Cr-TiO2 that was subsequently modified by photochemical deposition of Ag or Pd nanoparticles (Ag/Cr-TiO2, Pd/Cr-TiO2). Chemical-physical characterization results evidenced that the noble metals were homogeneously distributed on the Cr-TiO2 surface. By using Pd(0.25%)/Cr-TiO2, the AO7 discoloration efficiency was about 91.4% after only 60 min of visible irradiation, which can be due to the lowest band gap of this material. Moreover, nitrates, chlorides, total hardness, and coliform bacteria content significantly decreased after the treatment of real river water samples (that is contaminated by industrial and domestic effluents) under UV and visible light irradiation in the presence of TiCrOx decorated with noble metals. One hundred percent of elimination rate for E. coli, total coliforms, and other enterobacteriaceae (without regrowth) was achieved by using Ag/Cr-TiO2 as photocatalyst.

Characterization and Photocatalytic and Antibacterial Properties of Ag- and TiOx-Based (x = 2, 3) Composite Nanomaterials under UV Irradiation

“…To achieve a silver loading of 0.25 wt.% over BaTiO 3 particles, 6.25 mL of isopropanol, as a sacrificial agent, and the remaining amount of the MilliQ water were added to a 250 mL flask [35]. The resulting suspension was then transferred to a beaker containing the required amount of the photocatalyst and subjected to sonication for 10 min at 20 • C in an ultrasonic bath at 99% power.…”

“…In particular, to evaluate the concentration of the azo dye, a UV-vis spectrophotometer (Thermo Scientific Evolution 201, Waltham, MA, USA) was used to analyze the absorbance's value at 663 nm for the collected samples [37]. Furthermore, to calculate the mineralization of the pollutant and its intermediates formed during its photocatalytic oxidation, the TOC of the samples was determined by measuring the parts per million of CO 2 produced through combustion using a high-temperature catalytic combustion method with a Pt/Al 2 O 3 catalyst in a cylindrical fixed-bed reactor operating at 680 • C [35].…”

“…However, not all these signals are visible because of overlapping with the strong anatase signals. For a detailed attribution of the Raman bands, refer to [35].…”