Comparison of Solar Collection Geometries for Application to Photocatalytic Degradation of Organic Contaminants

A comparative study between four different solar collectors was carried out using oxalic acid and the pesticide carbaryl as model contaminants. The comparison was performed by means of a figure-of-merit developed for solar driven Advanced Oxidation Technology systems by the International Union of Pure and Applied Chemistry (IUPAC) for standardization purposes. It was found that there is a relationship between the photocatalyst concentration and the overall solar collector performance. Compound parabolic concentrator was the geometry with the highest turnover rate in the photocatalytic process of oxalic acid, followed by the V trough collector, the parabolic concentrator, and, finally, the tubular collector. When a comparative analysis was carried out using the figure of merit (collector area per order, $ACO$⁠), the parabolic trough concentrator (PTC) showed the highest efficiency (lower $ACO$ values) at low photocatalyst loads. The V trough collector and the compound parabolic collector showed similar $ACO$ values, which decreased as the photocatalyst concentration increased. The tubular collector was the worst in all catalyst concentration ranges, with the higher collection surface by the order of oxalic acid. Photocatalytic degradation of the carbamic pesticide was tested using the same experimental arrangement used for oxalic acid. In this case, the use of the figure-of-merit allowed us to observe the same trend as that displayed for oxalic acid, but with slightly higher $ACO$ values. Results of this work demonstrate that a comparison between different reactor geometries for photocatalytic processes is viable using this figure-of-merit approach and that the generated results can be useful in the standardization of a methodology for solar driven processes comparison and provide important data for the scaling up of the process.