Oxidation of microcystin-LR and cylindrospermopsin by heterogeneous photocatalysis using a tubular photoreactor packed with different TiO2 coated supports

Abstract

The photocatalytic degradation of cyanotoxins in aqueous solutions using slurry suspensions of TiO2 implies a post-filtration step to retain the photocatalyst. In this work, 2D and 3D TiO2 thin films sup-ported in inert surfaces was proposed for the solar photocatalytic removal of cyanotoxins microcystin-LR (MC-LR) or cylindrospermopsin (CYN) in distilled and natural water under neutral pH conditions. The photocatalytic experiments were performed in a lab-scale tubular photoreactor with a compound parabolic collector (CPC) using simulated and natural solar radiation. The tubular photoreactor was packed with transparent cellulose acetate monoliths (CAM) coated with a P25 paste or sol-gel 2D TiO2 film or with a photocatalytic 3D TiO2-loaded exterior paint (PC500, VLP7000 and P25). The efficiency of the TiO2 photocatalytic system in the presence of hydrogen peroxide was also assessed. PVC or glass tubes and glass spheres, coated with a photocatalytic 3D TiO2-loaded exterior paint, were also tested as inert surfaces. The supports used in this work were chosen according to some characteristics, such as cost, surface resistance, surface area and transmissibility to UV radiation. The 2 toxins MC-LR and CYN were purified from Microcysts aeruginosa and Cylindrospermopsis raciborskii cultures, respectively. The photocatalytic system P25-CAM/H2O2 can be considered the most effective process, considering the cyanotoxins removal efficiency, the cost and the simplicity of the preparation.

Flow Photochemistry: Shine Some Light on Those Tubes!

“…For photochemical applications, the reactor must be made of transparent material, and care should be taken to minimize the pressure drop over the bed. Whereas packed-beds or similar have been employed in wastewater treatment [45,46], few synthetic photochemical applications have appeared. Interesting examples are the synthesis of artemisinin from DHAA with supercritical CO 2 and O 2 feeds using a packed-bed of a porphyrin catalyst, reported by George, Poliakoff, and Rossen [47], and the TiO 2 -catalyzed synthesis of disulfides under aerobic conditions, reported by Noë l [48].…”

A review of solar and visible light active TiO2 photocatalysis for treating bacteria, cyanotoxins and contaminants of emerging concern

“…Microcystins are stable, water-soluble molecules and are rapidly absorbed by the liver resulting in harmful results such as cell necrosis, haemorrhage and death [189]. In recent years, significant attention has been given to the ever rising problem of these cyanotoxins occurring in aquatic sources, especially those that serve as sources of drinking water supply [189][190][191][192][193][194][195][196][197][198][199][200][201]. Choi et al [202] in 2007 reported that when using a visible light active (VLA) N-TiO 2 material under acidic conditions (pH 3.5), the adsorption and photocatalytic degradation of MC-LR is greatly improved.…”

Photocatalytic Reactors Dedicated to the Degradation of Hazardous Organic Pollutants: Kinetics, Mechanistic Aspects, and Design – A Review

“…In addition, the high photoactivity of TiO 2 and metal-doped TiO 2 nanocatalysts supported over monolith channels for dyes photoreduction is obviously due to large illuminated surface area in monolith channels (Pinho et al, 2015), fast electron transfer with hindered recombination rates (Tahir et al, 2015a), high mobility of electron on the catalyst surface, efficient desorption of products and high photonic efficiency (Tahir et al, 2015b).…”