G. Plantard

Kinetics and efficiency displayed by supported and suspended TiO2 catalysts applied to the disinfection of Escherichia coli

TiO2-mediated photocatalysis is widely used in a variety of applications and products in the environmental and energy fields, including photoelectrochemical conversion, self-cleaning surfaces, and especially water purification systems. The dimensionality of the structure of a TiO2 material can affect its properties, functions, and more specifically, its photocatalytic performance. In this work, the photocatalytic inactivation of Gram-negative Escherichia coli using three photocatalysts, differing in their structure and other characteristics, was studied in a batch reactor under UVA light. The aim was to establish the disinfection efficiency of solid TiO2 compared with that of suspended catalysts, widely considered as reference cases for photocatalytic water disinfection. The bacterial inactivation profiles obtained showed that: (1) the photoinactivation was exclusively related to the quantity of photons retained per unit of treated volume, irrespective of the characteristics of the photocatalyst and the emitted light flux densities; (2) across the whole UV light range studied, each of the photocatalytic solids was able to achieve more than 2 log bacterial inactivation with less than 2 h UV irradiation; (3) none of the used catalysts achieved a total bacterial disinfection during the treatment time. For each of the catalysts the quantum yield has been assessed in terms of disinfection efficiency, the 2D material showed almost the same performance as those of suspended catalysts. This catalyst is promising for supported photocatalysis applications.

Biosensor-based real-time monitoring of paracetamol photocatalytic degradation.

This paper presents for the first time the integration of a biosensor for the on-line, real-time monitoring of a photocatalytic degradation process. Paracetamol was used as a model molecule due to its wide use and occurrence in environmental waters. The biosensor was developed based on tyrosinase immobilization in a polyvinylalcohol photocrosslinkable polymer. It was inserted in a computer-controlled flow system installed besides a photocatalytic reactor including titanium dioxide (TiO2) as photocatalyst. It was shown that the biosensor was able to accurately monitor the paracetamol degradation with time. Compared with conventional HPLC analysis, the described device provides a real-time information on the reaction advancement, allowing a better control of the photodegradation process.

Effective coupling of phenol adsorption and photodegradation at the surface of micro-and mesoporous TiO2-activated carbon materials

Novel titania supported activated carbon catalysts were prepared by a straightforward titania coating route of a microporous activated carbon (AC) derived from shea nut shells, and investigated in phenol photocatalytic degradation. The proposed coating method enables a fixation of the preformed titania anatase nanoparticles (TiO2 NPs) in the external porosity thus allowing their accessibility towards UV irradiation, without causing any reduction of the AC specific area. Interestingly, the coating treatment reshapes the porous texture of the as-prepared TiO2–AC composite materials resulting in an improvement of the adsorption capacity and the formation of an additional mesoporosity on the TiO2-AC surface. Photocatalytic experiments carried out in a batch reactor led to 97% elimination rate of phenol in an aqueous solution with the AC catalysts containing TiO2 NPs in the range from 11 to 34 wt%. The photodegradation performance of the TiO2–AC catalysts was maintained over several successive cycles, without the need of any regeneration treatment. Considering both the textural and microstructural features of the composite materials and their associated phenol removal kinetics, in this paper, we provide new insights into phenol photodegradation pathway involving an effective coupling of adsorption and photodegradation functionalities, resulting in a photo-assisted regeneration mechanism of the catalyst.

Combining micelle-clay sorption to solar photo-Fenton processes for domestic wastewater treatment

A tertiary treatment of effluent from a biological domestic wastewater treatment plant was tested by combining filtration and solar photocatalysis. Adsorption was carried out by a sequence of two column filters, the first one filled with granular activated carbon (GAC) and the second one with granulated nano-composite of micelle-montmorillonite mixed with sand (20:100, w/w). The applied solar advanced oxidation process was homogeneous photo-Fenton photocatalysis using peroxymonosulfate (PMS) as oxidant agent. This combination of simple, robust, and low-cost technologies aimed to ensure water disinfection and emerging contaminants (ECs, mainly pharmaceuticals) removal. The filtration step showed good performances in removing dissolved organic matter and practically removing all bacteria such as Escherichia coli and Enterococcus faecalis from the secondary treated water. Solar advanced oxidation processes were efficient in elimination of trace levels of ECs. The final effluent presented an improved sanitary level with acceptable chemical and biological characteristics for irrigation.