BiVO4 powder 0.10 g added into 100 mL methylene blue (MB, C16H18N3ClS, Ajax, Australia)
with a concentration of 5 mg.L-1. This suspension was sonicated, stirred, and left in the dark for 24h
for the adsorption-desorption equilibrium of MB and oxygen on the surface of BiVO4 powder to be
achieved.