Photocatalytic Degradation of Organic Pollutants in Water

Abstract

Additional information is available at the end of the chapter http://dx.doi.org/10.5772/53699. Introduction " photocatalyst is defined as a substance which is activated by adsorbing a photon and is capable of accelerating a reaction without being consumed [ ]. These substances are invariably semiconductors. Semiconducting oxide photocatalysts have been increasingly focused in recent years due to their potential applications in solar energy conversion and environmental purification. Semiconductor heterogeneous photocatalysis has enormous potential to treat organic contaminants in water and air. This process is known as advanced oxidation process "OP and is suitable for the oxidation of a wide range of organic compounds. "mong "OPs, heterogeneous photocatalysis have been proven to be of interest due to its efficiency in degrading recalcitrant organic compounds. Developed in the s, heterogeneous photocatalytic oxidation has been given considerable attention and in the past two decades numerous studies have been carried out on the application of heterogeneous photocatalytic oxidation process with a view to decompose and mineralize recalcitrant organic compounds. It involves the acceleration of photoreaction in the presence of a semiconductor catalyst [ ]. Several semiconductors TiO , ZnO, Fe O , CdS, ZnS can act as photocatalysts but TiO has been most commonly studied due to its ability to break down organic pollutants and even achieve complete mineralization. Photocatalytic and hydrophilic properties of TiO makes it close to an ideal catalyst due to its high reactivity, reduced toxicity, chemical stability and lower costs [ ]. Fujishima and Honda [ ] pioneered the concept of titania photocatalysis also known as Honda-Fujishima effect . Their work showed the possibility of water splitting in a photoelectrochemical cell containing an inert cathode and rutile titania anode. The applications of titania photoelectrolysis has since been greatly focused in environmental applications including water and wastewater treatment. This chapter provides insight into the fundamentals of the TiO photocatalysis, discusses the effect of variables af-

Stability and Synergistic Effect of Polyaniline/TiO2 Photocatalysts in Degradation of Azo Dye in Wastewater

“…Thus, the aforementioned PANI-TiO 2 interactions result in the PANI-TiO 2 synergistic effect that hinders the recombination process and increases TiO 2 activity under ultraviolet (UV) and Vis irradiation [13]. Photocatalysis then proceed by the typical mechanism, known for TiO 2 : e CB − and h VB + transform H 2 O and O 2 into OH radicals, which in turn degrade the organic pollutants [14,15]. …”

Effective Removal of Humic Acid Using Strontium-Doped TiO2 Coated on Porous Ceramic Filter Media in Water Resource

“…Many reports about the effect of pH on photocatalytic degradation of organic compounds in water resource have been written [20,[28][29]. In fact, the interpretation of the pH-dependent photodegradation of HA on TiO 2 is a very difficult task because of its multiple roles.…”

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“…According to Akpan and Hameed [16] most study confirmed that the use of catalysts such as TiO2(SY) is effective for degradation at lower pHs, similar to the ones reported elsewhere, which is attributed to the strong electrostatic field of the Cs-TiO2(SY)/Glass photocatalyst enhancing photocatalytic performance between the surface of TiO2(SY) catalyst with positive charges, and the charges from solution, which is mostly negative [13,17]. However, lower pHs could adversely affect the catalyst during the photocatalytic process [16] making it necessary that the adsorption characteristics of MO on the surface of Cs-TiO2(SY)/Glass photocatalyst is investigated prior to the extended photodegradation process. According to Liu, et al [10] Cs could be used as an adsorbent at an optimal pH of between 3-6.…”