Photocatalytic degradation of reactive blue-4 dye from wastewater with α-Bi2O3 microrods under natural sunlight

alpha-Bi2O3 microrods were synthesized by co-precipitation method at pH 13 and temperature 80 degrees C. The synthesized sample shows crystallite size 36.02 nm, a specific surface area 1.865 m2/g, and pore size 15 nm. SEM and TEM images show formation of microrods with dimension of 3 mu m (diameter) x 23 mu m (length). HRTEM reveals lattice fringes with interplanar spacing of 0.197 nm corresponding to the (041) plane. Optical and electrochemical studies reveal band gap 2.53 eV, a flat-band potential + 0.56 V, conduction and valence band position at + 0.36 V, + 2.89 V respectively. alpha-Bi(2)O(3 )was used to degrade reactive blue dye-4 (RB-4) under natural sunlight irradiation, achieving 97% removal within one hour. Dye degradation decreased with the increasing pH of the solution, showing maximum efficiency at pH 3. The degradation follows first order kinetics with a rate constant 0.561 min-1. The degradation efficiency varies in the presence of anions, following order: Br- < Cl- < NO3- < COO- < PO43-. Scavenger experiments indicates that OH & sdot; and h(+) are active species involved in the RB-4 degradation. Regeneration of the photocatalyst was carried out by washing with distilled water shows 10% decrease in the degradation efficiency after four consecutive runs.