Exploration of the initial photocatalytic activity parameters of αFe2O3–rutile for methylene blue discoloration in water through the OFAT process

Abstract

The photocatalyst response is related to experimental conditions that improve effectiveness in removing contaminants. A parameter analysis of αFe2O3–rutile and water contaminated with methylene blue (MB) was carried out to obtain initial factors that impact reaction conditions. Moreover, the following factors were tested: the αFe2O3–rutile load, the initial MB concentration, and the initial pH solution. These one-factor-at-a-time variations were made to explore the conditions of each variable with the other two fixed. Above all, a significant change was identified in the initial discoloration rate from 5.2 to 35.56 10−9 mol g−1 s−1, with 34 and 91 % removal effectiveness, respectively. These results were achieved with an αFe2O3–rutile load of 1.0 g L−1, an initial MB concentration of 8.0 10−6 mol L−1, and a pH of 8.8, after 540 min of irradiation. This high discoloration effectiveness with αFe2O3–rutile had not been previously reported. The parameter that most influenced the photocatalytic activity was the initial pH solution due to the interaction of the point of zero charge of αFe2O3–rutile and the contaminated water; the pH of the solution exceeds the isoelectric point, it causes electrostatic forces and hydrogen bonds with MB to increase its effectiveness. The combination of αFe2O3–rutile and the removal of methylene blue in water improves adsorption on the surface of the αFe2O3–rutile, providing the highest discoloration rate.