Oxidation of niobium and titanium for semiconducting porous/tubular oxide formation for photocatalytic reduction of chromium
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Date
2019-05
Authors
Aiman Safwan Bin Azman
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Abstract
Nb foil was anodised in ethylene glycol electrolyte at 40V for 30 minutes in order to produce nanoporous Nb2O5. Effect of pH, amount of NH4F and temperature of the electrolyte were investigated in order to identify the best parameter to produce nanoporous Nb2O5. It was found that increase in pH of the electrolyte resulted in formation of more compact oxide while increase in amount of NH4F does not result significant changes in the structure of the anodised Nb. On the other hand, increase in temperature of the electrolyte bath increases the rate of chemical dissolution of the oxide layer resulting in higher rate of pores formation. Nanoporous Nb2O5 with pore diameter of average 83.46nm was successfully produced by anodising Nb in ethylene glycol electrolyte with 0.5wt% NH4F at 40V for 30 minutes with temperature of electrolyte bath at 80ºC. Comparative studies were done by anodising Ti to form TiO2 nanotubes with the average nanotube diameter formed was 97.32 nm and average length of 573 μm .As-anodised porous Nb2O5 successfully reduced 54% 10ppm Cr(VI) while the annealed Nb2O5 only reduced 42% 10ppm Cr(VI) after 150 minutes UV light irradiation. TiO2 nanotubes on the other hand reduced 48% 10ppm Cr(VI) after 150 minutes UV light irradiation. The addition EDTA hole scavenger increases the reduction of Cr(VI) from 42% reduction to 98% reduction in a shorter duration of UV light irradiation at 90 minutes.