Pankaj Chowdhury

Sacrificial hydrogen generation from aqueous triethanolamine with Eosin Y-sensitized Pt/TiO2 photocatalyst in UV, visible and solar light irradiation.

In this paper, we have studied Eosin Y-sensitized sacrificial hydrogen generation with triethanolamine as electron donor in UV, visible, and solar light irradiation. Aeroxide TiO2 was loaded with platinum metal via solar photo-deposition method to reduce the electron hole recombination process. Photocatalytic sacrificial hydrogen generation was influenced by several factors such as platinum loading (wt%) on TiO2, solution pH, Eosin Y to Pt/TiO2 mass ratio, triethanolamine concentration, and light (UV, visible and solar) intensities. Detailed reaction mechanisms in visible and solar light irradiation were established. Oxidation of triethanolamine and formaldehyde formation was correlated with hydrogen generation in both visible and solar lights. Hydrogen generation kinetics followed a Langmuir-type isotherm with reaction rate constant and adsorption constant of 6.77×10(-6) mol min(-1) and 14.45 M(-1), respectively. Sacrificial hydrogen generation and charge recombination processes were studied as a function of light intensities. Apparent quantum yields (QYs) were compared for UV, visible, and solar light at four different light intensities. Highest QYs were attained at lower light intensity because of trivial charge recombination. At 30 mW cm(-2) we achieved QYs of 10.82%, 12.23% and 11.33% in UV, visible and solar light respectively.

CHAPTER 2:Photocatalytic Processes for the Removal of Toxic Metal Ions

Semiconductor photocatalytic processes have been studied extensively in recent years due to their considerable advantages in environmental remediation. In this chapter, we address the treatment of hazardous wastewater containing toxic heavy metals using photocatalysis. The chapter reviews the effects of various factors such as catalyst loading, initial concentration of metal ions, presence of electron or hole scavenger, solution pH and light intensity. We start with the appraisal of the fundamental principles and mechanisms of the photocatalytic degradation process, followed by thermodynamic analysis, reaction kinetics and mass transfer effects. In addition to this, the design features, challenges and efficiencies of various photoreactors along with their possible scaling-up options are discussed. Moreover, assessment of harvesting of the solar energy for photoreactions to make photocatalysis a cleaner and a cost-effective treatment method is analysed. Finally, the chapter concludes with the status, efficacy and challenges ahead for the treatment of drinking water and wastewater containing different heavy metals through heterogeneous photocatalysis.

Degradation of Phenolic Compounds Through UV and Visible- Light-Driven Photocatalysis: Technical and Economic Aspects

Phenolic compounds are found in surface and groundwater as well as wastewater from several industries. It is necessary to eliminate phenols and phenolic compounds from contaminated water before releasing into water bodies due to their toxicity to human beings. Photocatalytic degradation seems to be a promising technology for the degradation of several phenolic compounds. Complete mineralization of phenol and phenolic compound has been achieved with TiO2-based photocatalysts under both UV and visible-light irradiation. This chapter will evaluate the conventional processes and advanced oxidation processes for the degradation of phenol and phenolic compounds. The process economics and efficiencies of different advanced oxidation processes will also be discussed. The main focus of the chapter is photocatalytic degradation processes under UV and visible light along with a detailed review of several factors affecting degradation of phenol and phenolic compounds. Photocatalytic degradation process is governed by reactions with hydroxyl radical or superoxide ion. The extent of degradation depends on light sources (UV, visible, and solar), the type of photocatalyst, and experimental conditions (pH, photocatalyst dosage, initial concentration of phenolic compounds, light intensity, electron donor concentration, etc.). Visible-light-active photocatalysts are applied by several researchers to exploit sunlight and to make the photocatalysis process sustainable. In the future, using sunlight in place of UV could make photocatalysis economically more efficient.