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.