Photoreactor slurry

The idea of using fluidized bed as both uniform light distribution and an immobilizing support for photocatalysts has been originally proposed and theoretically evaluated by Yue and Khan [3]. Experimental application of this idea has been demonstrated by Dibble and Raupp [4] who designed a bench scale flat plate fluidized bed photoreactor for photocatalytic oxidation of trichloroethylene (TCE). Recently, Lim et al. [5,6] have developed a modified two-dimensional fluidized bed photocatalytic reactor system and determined the effects of various operating variables on decomposition of NO. Fluidized bed photocatalytic reactor systems have several advantages over conventional immobilized or slurry-type photocatalytic reactors [7,8]. The unique reac-... 

When the Ti02 in slurry is used, no regrowth was found after a specific dark period. However, it is not clear whether solar photocatalysis with supported Ti02 avoid the E. coli regrowth once the zero is achieved. The interaction between the catalyst and the bacteria is the determinant factor in addition, the interaction is depending on the chemical matrix of water and geometrical characteristics of the photoreactors. This subject should be studied in more detail. 

For TOC determinations 2cm of the irradiated slurry was withdrawn from the photoreactor every 30 min and, after filtration over the Millipore filter, analyzed by a TOC Shimadzu analyzer. 

Photocatalytic reactions are promoted by solid photocatalyst particles that usually constitute the discrete phase distributed within a continuous fluid phase in the reactor. Therefore, at least two phases, that is, liquid and solid, are present in the reactor. The solid phase could be dispersed (SPD) or stationary (SPS) within the reactor. SPD photoreactors may be operated with the catalyst particles and the fluid phase(s) agitated by mechanical or other means. Depending on the means of agitation, the photoreactor resembles that of slurry or fluidized bed reactors. In numerous investigations, an aqueous suspension of the catalyst particles in immersion or annular-type photo reactors has been used. However, the use of suspensions requires the... 

Different types of solar photocatalytic reactors have been developed over time. Two main distinctions have been made (i) concentrating versus nonconcentrating reactors and (ii) slurry versus fixed catalyst reactors. These two classifications are not mutually exclusive, and other categories may also be established, for instance, a very important is the one of tubular solar photoreactors. 

COMPARING Ti02 SLURRY PHOTO REACTORS AND Ti02 IMMOBILIZED PHOTOREACTORS... 

The general methodology for modeling slurry photoreactors has been reviewed by Cassano and Alfano (2000). We will apply these concepts to the evaluation of absolute, true values of quantum yields. 

Kamble SP, Sawant SB, Pangarkar VG. (2006) Photocatalytic degradation of m-dinitro-benzene by UV illuminated TiO in slurry photoreactor. J. Chem. Technol. BiotechnoL, 81 365-373. 

These show the largest photocatalytic activity compared with the immobilized photocatalyst and provide a high total surface area of photocatalyst per unit volume which is one of the most important factors configuring a photoreactor. However, these reactors require an additional downstream separation unit for the recovery of photocatalyst particles [116, 137]. Table 7.4 summarizes the advantages and disadvantages of both slurry and immobilized systems. 

For the photocatalytic reduction of CO2, in 1979, Inoue et al. introduced a slurry reactor in which catalysts were suspended in water [143]. Until 2000, slurry-type reactors were widely considered for reduction of CO2 under UV or visible irradiation. On the other hand, Tahir and Amin suggested that this type of reactor is not efficient for enhancing the photocatalytic activity due to the low surface area and complicated separation process required to isolate the miniature catalyst grains [144]. Furthermore, one of the UmitatirHis for CO2 photoreduction in the liquid phase is due to its low solubility in water. Therefore, Rossetti et al. developed an innovative cmicept of photoreactor, allowing to operate under high pressure (up to... 

Fig. 7.3 Main types of photoreactors used for water and wastewater treatment (irradiated by sun or UV lamps) (a) compound parabolic collector (CPC) (b) parabolic trough reactors (PTR) (c) double-skin sheet reactor (DSSR) (d) slurry, wall, fixed bed reactor (e) batch reactor with outer source of irradiation and (f) batch reactor with inner source of irradiation...

Ola O, Maroto-Valer M, Liu D, Mackintosh S, Lee C-W, Wu JC (2012) Performance comparison of CO2 conversion in slurry and monolith photoreactors using Pd and Rh-Ti02 catalyst under ultraviolet irradiation. Appl Catal Environ 126 172-179... 

Nishio J, Xokumura M, Znad HT, Kawase Y (2006) Photocatalytic decolorization of azo-dye with zinc oxide powder in an external UV light irradiation slurry photoreactor. J Hazard Mater 138 106-115... 

Pahnisano G, Loddo V, Augugliaro V, Bellardita M, Camera Roda G, Parrino F (2015) Validation of a twodimensional modeling of an externally irradiated slurry photoreactor. Chem Eng J 262 490-498... 

---