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

Abstract

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 TiO 2 -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.

Efficient Advanced Oxidation Process (AOP) for Photocatalytic Contaminant Degradation Using Exfoliated Metal-Free Graphitic Carbon Nitride and Visible Light-Emitting Diodes

“…Figure 9 shows the influence of pH on phenol degradation. The photodegradation efficiency of phenol at acidic pH (2)(3)(4)(5) was better than at basic pH (9)(10)(11)(12). Almost 97% of phenol degradation was achieved in 60 min of reaction time at acidic pH compared with 100% for natural pH in 90 min and 80% at basic pH in 180 min, a similar pH dependency was shown in the literature [47,54].…”

“…Heterogeneous photocatalysis has proven to be an effective and feasible method for removing organic contaminants, producing CO 2 and mineral salts as byproducts [8]. Many research efforts have been devoted to the development of advanced oxidation processes (AOPs) using ultraviolet (UV) and visible light [9]. Sunlight has limitless energy, which can be used for the activation of photocatalysts; however, it has a wide wavelength range.…”

Hydrothermal synthesis of BiOBr and BiOBr/CNT composites, their photocatalytic activity and the importance of early Bi6O6(OH)3(NO3)3·1.5H2O formation

“…Several classes of visible light photocatalyst are being investigated and modified [17,30,[33][34][35][36][37], but bismuth oxyhalides, (BiOX, X = Cl, Br, I), due to their unique layered structure [38,39], suitable band gap values, and stability [40,41] has shown promising visible light response [28,42]. They have relative stability under UV/visible light irradiation, show visible light active response and superior performance compared to Evonik Aeroxide P25 (titania) under UV irradiation [31,43].…”

An overview: recent development of semiconductor/graphene nanocomposites for photodegradation of phenol and phenolic compounds in aqueous solution

“…Since all phenolic compounds are aromatic compounds with one or more hydroxyl groups attached to the aromatic ring, are commonly found in wastewater discharged from different industries like petroleum refineries, plastics, chemical synthesis, dyes, coke plants, pulp and paper, detergents, textiles, pharmaceutics, pesticides, and herbicides synthesis. On the other hand, phenol along with its nitrophenol and chlorophenol derivatives are significantly soluble in water (Table 2) [28,29]. It should be noted that these hazardous compounds can also arise from natural sources in the aquatic environment (at low concentration), like lignin transformation, algal secretion, hydrolyzable tannins, and flavanoids, and humidification processes [30][31][32][33].…”

“…2,4-Dinitrophenol (0.01 mg L −1 ) Table 2. Solubility of phenol and its derivatives in water [28,29]. Moreover, some of the intermediate products formed during photocatalytic degradation of phenol.…”