Solar Photocatalytic Detoxification and Disinfection of Water: Recent Overview

Abstract

During the last few years, there has been a plethora of research and development in the area of solar photocatalysis (TiO2 and photo-Fenton). This overview, of the most recent papers on the use of sunlight to produce the O∙H, comments on those most relevant to the development of the technology and summarizes most of the recent research related to the degradation of water contaminants, and how solar photocatalysis (coupled with biotreatment) could significantly contribute to the treatment of very persistent toxic compounds. Various solar reactors for photocatalytic water treatment based mainly on nonconcentrating collectors developed during the last few years are also described in detail. This review also reports the use of the photocatalytic processes (TiO2) to inactivate microorganisms present in water, placing special emphasis on those applications that make use of sunlight. Work on water disinfection mechanisms in the last decade is summarized in the last part of this overview, with attention to some experimental systems developed to optimize this disinfection technology.

Photolysis and TiO2-catalysed degradation of diclofenac in surface and drinking water using circulating batch photoreactors

“…Inconsistencies in optimum TiO 2 loadings reported have been linked to the geometry of the chosen photoreactor and the nature of the compound under investigation. [44,45] Thus far, the optimal TiO 2 loading for DCF photocatalysis reported in related studies was 1, [41] 0.624 [34] and 0.25 g L À1 . [31] The much lower TiO 2 loading determined in this study can be attributed to the very effective circulation in the immersion-well setup chosen, which ensured optimal distribution of photocatalyst throughout the entire reaction mixture (Fig.…”

Solar photocatalysis for water disinfection: materials and reactor design

“…Proposed mechanisms of cell death 30 include, DNA/RNA damage 28 , membrane rupture 28 , interruption of respiratory pathways 32 and increased ion permeability. 33 These mechanisms are summarized schematically in Figure 2.…”

“…Faecal coliforms achieved inactivation in 30 minutes in photocatalytic bottles whereas standard bottles did not achieve inactivation in the measured time period (80 minutes). Another 30 remarkable finding is that both total and faecal coliforms were incapable of regrowth in the photocatalytic bottles. After SODIS treatment, the closed bottles were stored for seven days in ambient light at room temperature.…”

“…Such reactors are an engineered advancement of the SODIS protocol, applicable to treating greater volumes of water for household use. Hereafter, in this review, the two different configurations will be labeled as 30 'bottles' and 'reactors'. The other key development of SODIS bottles and reactors is the increase in disinfection efficacy by incorporation of a photocatalyst, typically titanium dioxide (TiO 2 ), into the process.…”

“…The first report of TiO 2 photocatalytic inactivation of bacteria was in 1985 by Matsunaga et al 27 , and since then a large number of microorganisms have been reported to be photocatalytically 20 inactivated. A number of reviews address different aspects of the process such as application of photocatalysis for disinfection of water contaminated with pathogenic micro-organisms 28,29 , decontamination of water by solar photocatalysis 30 and proposed mechanisms and modeling. 31 The majority of photocatalytic 25 studies cite the hydroxyl radical ( • OH) as the reactive oxygen species (ROS) responsible for microorganism inactivation, although other ROS such as hydrogen peroxide (H 2 O 2 ) and the superoxide anion radical (O 2…”