Highly efficient liquid-phase photooxidation of an azo dye methyl orange over novel nanostructured porous titanate-based fiber of self-supported radially aligned H2Ti8O17•1.5H2O nanorods

Novel nanostructured porous fibers of self-supported, radially aligned H(2)Ti(8)O(17)(.)1.5H(2)O nanorods were prepared from layered H(2)Ti(4)O(9)(.)1.2H(2)O tetratitanate fibers by novel solvothermal reaction in glycerine at 150-250 degreesC. The H(2)Ti(8)O(17)(.)1.5H(2)O fibers with diameters of 0.5-1.5 mum and lengths of 10-20 mum consist of multi-scale nanopores and nanostructures. They also are of high crystallinity, large surface area of 127 m(2) g(-1), and stable phase up to 350 degreesC. Photocatalytic activity of the H(2)Ti(8)O(17)(.)1.5H(2)O fibers was evaluated in aqueous photooxidation of an azo dye methyl orange in the presence of UV irradiation and O-2, using P-25 as the standard sample. Both the photocatalytic activity and the dispersity-agglomeration property of H(2)Ti(8)O(17)(.)1.5H(2)O fibers are pH-controllable. Highly photooxidative activity, superior to that of P-25, occurs at pH 6.0-11.0 due to certain distinguishable material characteristics and to large amounts of adsorbed reactants of surface active OH. free radicals, surface hydroxyl OH, O-2(.-), (OOH)-O-., and methyl orange. The agglomeration of H(2)Ti(8)O(17)(.)1.5H(2)O fibers becomes more serious from pH 2.0 to pH 5.0 and from pH 6.0 to pH 11.0. Well-dispersed H(2)Ti(8)O(17)(.)1.5H(2)O fibers occur at pH 6.0. Both the total photodegradation of waste chemicals and the entire sedimentation of H(2)Ti(8)O(17)(.)1.5H(2)O fibers can be timed to end simultaneously at suitable pH value. The photocatalyst-free reaction solution is then easily removed, and the fresh wastewater is added again. Standard unit operation processes of chemical engineering are used to design a continuous, low-cost, large-scale, liquid-phase photocatalysis technique based on the H(2)Ti(8)O(17)(.)1.5H(2)O fibers.