Phototreatment of Water by Organic Photosensitizers and Comparison with Inorganic Semiconductors

Abstract

Phototreatment of water is drawing the attention of many as a promising alternative to replace methods like chlorination, ozonization, and other oxidation processes, used in current disinfection methods limiting harmful side-products and by-products that can cause damage to the fauna and flora. Porphyrins, phthalocyanines, and other related organic dyes are well known for their use in photodynamic therapy (PDT). These photosensitizers cause cell death by generating reactive oxygen species (ROS) especially singlet oxygen in the presence of light. Such molecules are also being explored for photodynamically treating microbial infections, killing of unwanted pathogens in the environment, and oxidation of chemical pollutants. The process of photosensitisation (phototreatment) can be applied for obtaining clean, microbe-free water, thus exploiting the versatile properties of photosensitizers. This review collects the various attempts carried out for phototreatment of water using organic photosensitizers. For comparison, some reports of semiconductors (especially TiO2) used in photocatalytic treatment of water are also mentioned.

Disinfection and Mechanistic Insights of Escherichia coli in Water by Bismuth Oxyhalide Photocatalysis

“…The photodisinfection action, depending on the nature of the photosensitizer/photocatalyst, can proceed through type‐I or type‐II mechanism or both. Where type‐I mechanism involves electron transfer from excited sensitizer to substrate molecule or oxygen yielding free radicals as HO• and superoxide ion while in type‐II mechanism, energy transfer between the photosensitizer and oxygen produces singlet oxygen ( 1 O 2 ) . Photosensitizers were shown to be very effective in photodynamic killing of bacteria , however employing either the photocatalyst or photosensitizer as a suspension or a homogenous solution is problematic for water treatment as they must be removed from the water.…”

“…Photocatalytic disinfection involves three components that are individually harmless to the biological environment, specifically the photosensitizer, light and molecular oxygen. The term photosensitizers, however, generally refers to organic catalyst (as methylene blue, rhodamine B and porphyrins) whereas the term photocatalyst refers to inorganic catalysts (as titanium dioxide (TiO 2 ), zinc oxide (ZnO), ferric oxide (Fe 2 O 3 )) .…”

Hybrid nickel-free graphene/porphyrin rings for photodegradation of emerging pollutants in water

“…10,11 In this context, porphyrins represent one of the most used class of light-induced catalysts, nding applications in many elds including water remediation. [9][10][11][12][13][14][15][16] Nevertheless, the ISC for such kind of materials is strongly limited by rapid electron-hole recombination between the singlet excited state and the ground state, mainly due to aggregation phenomena. 13,16 To turn this limitation, the combination of porphyrins with carbon-based nanostructures, such as carbon nanotubes and graphene [17][18][19][20][21][22][23] was exploited.…”

Une porphyrine comme photosensibilisant des eaux d'irrigation, photostabilité et efficacité

“…Ces trois composants sont responsables de la formation des espèces réactives de l'oxygène (oxygène singulet et/ou des espèces radicalaires), qui conduisent à la photoinactivation des microorganismes (ALVES et al, 2009;TAVARES et al, 2010). L'efficacité de la désinfection de l'eau potable (BONNETT et al, 2006) et des eaux usées (JEMLI et al, 2002;CARVALHO et al, 2007) par photosensibilisation a été prouvée par des tests de laboratoire en utilisant les bactéries indicatrices de pollution fécale, les kystes de protozoaires et les oeufs d'helminthes (ACHER et al, 1990;ALOUINI et JEMLI, 2001;THANDU et al, 2015). Pour les applications environnementales sur terrain, la lumière solaire peut être utilisée comme source de lumière.…”