Synergistic Effect of pH and Phase in a Nanocrystalline Titania Photocatalyst

Titanium dioxide is a semiconducting material that has been studied for many years as a photocatalytic material to degrade organics in water. This study investigated the effect of anatase-rutile mixtures and pH on the photocatalytic degradation of the dye Methylene blue as the target analyte. Anatase-rutile mixtures between 0 and 90% rutile that were synthesized from a water-soluble precursor were suspended at pH 4, 7, and 10. Suspension pH significantly affected the reactivity and efficiency of the photocatalysts because of the particle–particle and sorbate–surface interactions. The highest removal percentage of MB by 240 min at pH 4, 7, and 10 was 35, 99, and 93%, respectively. pH 7 was ideal to observe the affect of percent rutile on the degradation rate, where 91% was removed within 120 min by the material composed of 20% rutile, which is attributed to the synergistic charge transfer of holes from rutile to anatase.