Solar Photocatalytic Oxidation of Hydroxy Phenols in a CPC Reactor with Thick TiO2 Films

Solar Photocatalysis is an advanced oxidation process that is involved on water detoxification as a very promising technology. This process has been used for polishing industrial and municipal wastewaters, mainly with titanium dioxide (TiO2) as a catalyst. Most of the reactors use TiO2 as a powder and need a pump in order to have the water moving through the system. A novel photocatalytic reactor, based on Compound Parabolic Collectors (CPC), was developed. The reactor has TiO2 fixed as a thick film in the CPC tubes and water flows inside by density differences exclusively. This reactor is designed to avoid catalyst separation and water pumping, steps that are energy – demanding and expensive. The films were prepared by conventional sol – gel method on 13 mm diameter Pyrex tubes. The films were firmly bounded to tubes and used for several test with good efficiencies. Films had a mix of anatase and rutile crystalline phases and its particles are nanoscopic. A CPC reactor with 20 tubes connected to the tank by its upper side only was developed and used. Resorcinol was effectively removed from water, either with or without persulfate as electron acceptor, at laboratory bench (one CPC tube experiments) and at pilot scale (20 tubes in the reactor). Main reaction sub-products (tri – hydroxy benzenes) were also oxidized in reasonable solar irradiation times.