Graduation Year

2010

Document Type

Thesis

Degree

M.S.Ch.E.

Degree Granting Department

Chemical Engineering

Major Professor

John T. Wolan, Ph.D.

Keywords

Indium vanadate, InVO4, Titania, TiO2, Amorphous precursor, Methyl orange, Taguchi methods

Abstract

The effects of various catalyst synthesis parameters on the photocatalytic degradation kinetics of aqueous methyl orange dye are presented. The four factors investigated were: i) InVO4 concentration, ii) nickel concentration, iii) InVO4 calcination temperature, and iv) ballmilling time. Three levels were used for each factor. Due to the large number of possible experiments in a full factorial experiment, an orthogonal-array experimental design was used. UV-vis spectrophotometry was used to measure the dye concentration. The results show that nickel concentration was a significant parameter, with 90% confidence. The relative ranking of importance of the parameters was nickel concentration > InVO4 concentration > InVO4 calcination temperature > milling time. The results of the orthogonal array testing were used to make samples of theoretically slowest and fastest catalysts. Curiously, the predicted-slowest catalyst was the fastest overall, though both samples were faster than the previous set. The only difference between the slowest and fastest catalysts was the milling time, with the longer-milled catalyst being more reactive. From this result, we hypothesize that there is an interaction effect between nickel concentration and milling time. The slowest and fastest catalysts were characterized using energy-dispersive spectroscopy (EDS), scanning electron microscopy (SEM), x-ray powder diffractometry (XRD), BET surface area analysis, and diffuse-reflectance spectroscopy (DRS). The characterization results show that the fastest catalyst had a lower band gap than the slowest one, as well as a slightly greater pore volume and average pore diameter. The results indicate that fast kinetics are achieved with low amounts of nickel and a long ball milling time. Under the levels tested, InVO4 concentration and the calcination temperature of the InVO4 precursor were not significant.

Share

COinS