Effect of the Implementation of Static Mixers in a CPC Solar Reactor for the Photocatalytic Degradation of Paracetamol

In the present work, the paracetamol degradation is reported, carried out by heterogeneous photocatalysis, using TiO2 as a catalyst at the scale of 30 L in a Compound Parabolic Collector (CPC) solar reactor. The hydrodynamics effect on the paracetamol degradation produced by static mixers (SM) inside the CPC pipes was evaluated for three different operating conditions: 0 SM, 3 SM, and 6 SM. The initial paracetamol concentration was 25 mg L−1 with 0.25 and 0.50 g L−1 of catalyst dosage and pH 5; the accumulated solar radiation (QUV\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${Q}_{UV}$$\end{document}) was measured. Photodegradation experiments were performed using natural sunlight and the reaction was monitored by High Performance Liquid Chromatography and by Total Organic Carbon evaluation. The hydrodynamics performance was analyzed by solving the Navier–Stokes equations and the Standard k-ε turbulence model using finite element simulations in 3D domains. The mean flow velocity, vorticity and turbulence intensity (TI) fields for all conditions were studied. Although results showed that contaminant was degraded in the three mixing conditions achieving over 96% of degradation at QUV\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${Q}_{UV}$$\end{document}= 4 kJ L−1, faster reaction rates were identified at the beginning of the process when the 3 SM were used (kapp = 0.7640), compared to 6 SM (kapp = 0.4489), and 0 SM (kapp = 0.5796) using 0.25 g L−1. This effect could be explained by the eddies in the vicinity of the irradiated outer walls, and more TI levels produced by the SM, which promoted irradiation and contact between the catalyst and the organic molecules.