The present contribution is to synthesize and characterize a new material photocatalyst. It also explores the possibility of using it to remove organic and inorganic pollutants in water. In this context, the sillenite Bi 12 CoO 20 (BCO) in pure phase was synthesized by the combustion sol–gel method. The phase was identified by X-ray diffraction (XRD) then it was refined in the cubic symmetry in the space group (I23 N°197) using the Rietveld refinement method; the lattice constant was accurately determined. A direct optical bandgap of 2.56 eV was evaluated using the UV–Visible diffuse reflectance. The electrochemical properties were investigated for the first time. A flat band potential of E fb  = 0.62 V SCE was found with a p -type character; the hole density N d  = 54.2 × 10 17  cm −3 extends the depletion width at 27 nm. The photocatalytic activity of BCO nanoparticles was tested to eliminate organic and inorganic pollutants namely the Basic red 46 (BR46) and hexavalent chromium Cr(VI). An acceptable rate was observed within 3 h for both contaminants.