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Cost-effective solar collector to promote photo-Fenton reactions: A case study on the treatment of urban mature leachate

Gomes, Ana I., Silva, Tânia F.C.V., Duarte, Miguel A., Boaventura, Rui A.R., Vilar, Vítor J.P.
Journal of cleaner production 2018 v.199 pp. 369-382
aluminum, case studies, coatings, cost analysis, cost effectiveness, decontamination, durability, finishes, leachates, lighting, mineralization, photocatalysis, reflectance, solar collectors, solar radiation, stainless steel, wastewater
Photocatalytic processes, like photo-Fenton (PF), are being successfully employed in the decontamination of diverse wastewaters. However, some drawbacks associated with solar collectors' cost and efficiency loss over time (due to the soiled of the reflective surface) are blocking their application at industrial scale. In this work, aiming the cost reduction and durability increase of the solar collectors', different reflector materials (anodized aluminum with (MS) and without (R85) protective coating, soiled aluminum (R85s) and stainless steel (SS)) and geometries (flat (F), simple double parabola (SP) and traditional double parabola (DP)) were tested and their efficiency assessed. Ferrioxalate actinometry was performed, at lab-scale under simulated sunlight, and the optical concentration ratio (CRO) followed the sequence: SS-F (0.59) ≈ R85-F (0.60) < R85s-DP (0.67) ≈ SS-SP (0.70) ≈ SS-DP (0.72) < MS-DP (0.84) < R85-DP (0.93). These results agree with the ray-trace and specular reflectance analysis. The impact of 8-years of outdoor aging on the R85 aluminum reflectors was clearly shown. For the photo-Fenton lab-trials with an urban mature leachate, the time to achieve 60% mineralization decreased as follows: SS-F (158′) > R85-F and R85s-DP (153′) > SS-SP (141′) > SS-DP (127′) > R85-DP (121′) > MS-DP (117’). According to the cost analysis, for the same investment required to build 100 m2 of an R85-DP collector, it is possible to construct 126 m2 of an SS-F collector, containing 1.6 times more absorber tubes per square meter, which leads to a treatment rate increment of 51%. The reflectors performance was also validated at pilot-scale, under natural sunlight.