Radiation Absorption and Optimization of Solar Photocatalytic Reactors for Environmental Applications

Abstract

This study provides a systematic and quantitative approach to the analysis and optimization of solar photocatalytic reactors utilized in environmental applications such as pollutant remediation and conversion of biomass (waste) to hydrogen. Ray tracing technique was coupled with the six-flux absorption scattering model (SFM) to analyze the complex radiation field in solar compound parabolic collectors (CPC) and tubular photoreactors. The absorption of solar radiation represented by the spatial distribution of the local volumetric rate of photon absorption (LVRPA) depends strongly on catalyst loading and geometry. The total radiation absorbed in the reactors, the volumetric rate of absorption (VRPA), was analyzed as a function of the optical properties (scattering albedo) of the photocatalyst. The VRPA reached maxima at specific catalyst concentrations in close agreement with literature experimental studies. The CPC has on average 70% higher photon absorption efficiency than a tubular reactor and requires 39% less catalyst to operate under optimum conditions. The "apparent optical thickness" is proposed as a new dimensionless parameter for optimization of CPC and tubular reactors. It removes the dependence of the optimum catalyst concentration on tube diameter and photocatalyst scattering albedo. For titanium dioxide (TiO(2)) Degussa P25, maximum photon absorption occurs at apparent optical thicknesses of 7.78 for CPC and 12.97 for tubular reactors.

Modelado y evaluación experimental de un reactor solar fotocatalítico no isotérmico: efecto de la temperatura sobre la cinética de la velocidad de reacción

“…For this reactor, it was assumed perfect mixing and removal percentages of MB (%Degr) as response variable (19):…”

“…Typically, the interpretation of the experimental results is based on t 30w (19), the treatment time (20), the incident radiation within the reactor, and the photon flux absorbed by the catalyst. However, these parameters interact and yield erroneous conclusions, which is impractical given that the reactor is comprised of illuminated and non-illuminated areas.…”

Industrial synthesis and characterization of nanophotocatalysts materials: titania

“…Such nanophotocatalysts have also been used for the treatment of winery wastewater using a photocatalytic reactor [68]. Today, the use of photoreactors of pilot plants has grown quickly in the development and use of different kinds of photocatalytic reactors, especially to be used with solar radiation [69][70][71].…”

Assessment of solar driven TiO2-assisted photocatalysis efficiency on amoxicillin degradation

“…This pH value was chosen given that several authors have already reported the influence of pH on TiO2-mediated photocatalytic degradation of AMX and found minimal influence in the near-neutral pH range (Elmolla and Chaudhuri 2010b;Klauson et al 2010;Dimitrakopoulou et al 2012). The suspended catalyst load for photocatalysis was 0.5 g L −1 of TiO2, which is able to absorb all solar UV photons considering an internal photoreactor tube diameter of 46.4 mm (Colina-Márquez et al 2010). Thirty minutes after TiO2 addition, another sample was taken to determine the AMX adsorption onto the catalyst surface (which was found out to be less than 2 % in average), and then the CPCs were uncovered in order to begin the photocatalytic experiments.…”

“…However, to the best of our knowledge, none so far have neither applied compound parabolic collectors (CPC) as photoreactors, nor have studied the influence of the individual presence of common occurring inorganic ions on the degradation of amoxicillin in aqueous solution. Theoretical and experimental studies (Fernández et al 2005;González et al 2009;Vilar et al 2009;Colina-Márquez et al 2010) have shown that CPCs are highly efficient on collecting solar radiation, so they are considered the best choice for different solar photocatalytic processes (Malato et al 2002). Thus, the main objective of this work was to study the enhancement of the photocatalytic degradation of AMX in a CPC pilot plant, promoted by the presence of suspended TiO2 and natural sunlight, when compared with solar photolysis.…”