Experimental studies on water matrix and influence of textile effluents on photocatalytic degradation of organic wastewater using Fe-TiO2 nanotubes: Towards commercial application.

The application of photocatalysis for the effective removal of textile dyes is dependent on various parameters related with both water quality and different chemicals discharge during the dying process. Because the oxidation rates of the particular mixtures mainly influenced by the elements of the water matrix. These elements comprised of organic, inorganic salts, heavy metals, and ions. The impact of water matrices (Tap water, DI water, seawater, surface water, and ultra-pure water) on the Congo red decolorization, total organic carbon, and chemical oxygen demand removal efficacy has been assessed using Fe-TiO2 nanotubes as a photocatalyst. The photocatalytic degradation rate decreased in unclean water due to the interferences of dissolved organics and minerals. However, all the environmental water matrices depict the significant decrease in turbidity and conductivity after treating with photocatalytic process. The photoactivity and capacity for decantation are the two crucial elements that have an impact on the "practical efficiency" of photocatalysts. Moreover, the textile wastewater contains a large quantity of dyes mixed with number of detrimental chemicals and other effluents discharged into the water which consequently pollute ecosystem and cause serious risks to human health. For environmental applications, we investigated individually the impact of various harmful chemicals commonly discharged from each step of textile wet processing which can have inhibiting or promoting effect on the azo dye photocatalytic degradation.

Optimization of hydrothermal synthesis of Fe-TiO2 nanotube arrays for enhancement in visible light using an experimental design methodology.

We designed an experiment to optimize the hydrothermal modification of iron on anodized TiO2 nanotubes. A central composite design that included five design points was used to determine the condition parameters for hydrothermal reaction time (1-5 h) and hydrothermal temperature (120-180 °C). A statistical method was used to observe the effects of hydrothermal conditions on the material properties and photocatalytic activity of a Fe-TiO2 nanotube catalyst. Scanning electron microscopic (SEM) analysis shows the iron is doped on the TNTs, which is further confirmed by energy-dispersive X-ray spectroscopy. X-ray diffraction indicate the existing states of iron in the form of iron oxide on the TNT. The maximum degradation efficiency (92.3%) was achieved at a hydrothermal temperature of 150 °C and time of 3 h. It is found that the optimal medication of the Fe-TNT catalyst occurred at a particular combination of temperature (150 °C) and reaction time (3 h), that provide the more active sites for iron to enter the crystal lattice of TNT, and that the maximum CR degradation could be achieved.

Effect of HCl treatment on physico-chemical properties and photocatalytic performance of Fe-TiO2 nanotubes for hexavalent chromium reduction and dye degradation under visible light.

In this study, we prepared Fe2O3/TNT composite (Fe-TNT) foil by combining anodization with the hydrothermal method. Photocatalytic reaction was restricted by a cluster of iron particles accumulated on the foil surface and the photocatalytic reaction sites reduces. Herein, using XPS determined that these iron particles are composed of iron oxide. An acid treatment, hydrochloric acid (HCl) was used to successfully remove the surface accumulation of iron oxide particles on the photocatalyst. Using cleaned Fe-TNT foil, the photocatalytic activity of 5 mg/L Congo red (CR) and hexavalent chromium reduction was significantly increased under visible irradiation. In addition, the influence of different aspects such as pH, the concentration of Fe, and the effect of different acid treatment time was evaluated. Removing the surface accumulated iron oxide and adjusting the pH in acidic medium, 73% hexavalent chromium reduction achieved within 180 min. The reusability was also explored by monotonous CR degradation. The CR degradation using Fe0.25-TNT was lessened from 78% in the first cycle to 71% in the 3rd cycle. It was also confirmed experimentally that photocatalytic activity improvement of HCl treated Fe-TNT was not due to alternation in nanotube structure.