Assessment of two solar photo-reactors’ performance for photo Fenton applications: the role of the reflective surface shape and the diameter tube

• A new design of tubular solar photo-reactor, called “U-trough”, was evaluated. • A larger photo-reactor diameter results in a lower optimum concentration of iron. • Change of the reflective surface in the U-trough did not decrease photon absorption. • U-trough has an optical efficiency for photo-Fenton very similar to that of the CPC. • The U-trough reactor has a more favorable cost-benefit ratio than the CPC. In this work, a design of tubular solar photo-reactor, called “U-trough”, for water or wastewater photocatalytic treatment is presented as a promising alternative to reduce CPCs’ capital and operating costs. The modifications proposed are: (i) changing the shape of the reflecting aluminum surface to a simpler flat U-shaped reflector and (ii) increasing the external diameter of the tubes to 75 mm. CPC (50 mm outer diameter) and U-trough photoreactors (75 mm outer diameter) have been compared using the conventional solar photo-Fenton reaction (at pH = 2.8) in natural water spiked with sulfamethoxazole as model contaminant. CPC has a radiation concentration ratio of 1, while the U-trough ratio is <1. As photo-Fenton process is affected by water temperature, results were confirmed with experiments done during summer and winter. The results showed that the best iron concentration is around 10 mg L −1 , half of the amount previously optimized for CPC photo-reactors (20 mg L −1 ). These results are consistent with well-known statements, as a larger photo-reactor diameter results in a lower optimum concentration of iron due to a longer optical path length to absorb all the incident photons. In this work, it has been confirmed that the U-trough reactor has an optical efficiency for applying photo-Fenton process very similar to that of the CPC by a proper selection of catalyst concentration, using a simpler reflector surface. These findings encourage further investigation of the application of U-trough photo-reactors to remove organic micropollutants and microbial pathogens in real wastewater.