Removal of Cr(VI) and Humic Acid by Heterogeneous Photocatalysis in a Laboratory Reactor and a Pilot Reactor

In this work heterogeneous photocatalysis has been used in order to eliminate Cr(VI) as well as humic acid in a laboratory reactor and in a pilot reactor. The reactors have been constructed with proportional geometric properties and similar nominal powers. In the laboratory reactor a kinetic study of the reduction of Cr(VI) to Cr(III) has been done for different concentrations of the catalyst at pH 4 and 7. The influence in the increase of the reduction of chromium(VI) that is obtained by the presence of humic acid has been determined. It has been verified that all the reactions possess pseudo-first-order kinetics, and the values of the apparent kinetic constants obtained for all systems studied have been compared. These values have allowed selection of the values of the variables to be used in the pilot reactor as it is desired to eliminate Cr(VI) by reduction and precipitation and humic acid by oxidation. A comparative evaluation of the efficiencies of the reactors was based on kinetic determinations.