Optimization of physico-chemical parameters for the photo-oxidation of neutral red on the spinel Co2SnO4

• The spinel Co2SnO4 is characterized for the oxidation of neutral red under sunlight.
• The spinel Co2SnO4 is elaborated by nitrate route.
• The conduction band of Co2SnO4 (0.16 VSCE) permits the formation of O2− radicals.
• The kinetic follows a pseudo second order with a rate constant of 11.5 × 10−3 L/mg/min.

The spinel Co2SnO4 is prepared by chemical route to assess its feasibility for the oxidation of neutral red under visible illumination. The diffuse reflectance gives a band gap of 1.72 eV, properly matched to the sun spectrum. The electrons in the conduction band (0.16 VSCE), determined from the capacitance measurement, permit the formation of O2− radicals, responsible of the neutral red oxidation. The dye concentration, catalyst dose, agitation speed and light flux are optimized. A degradation of 85% is obtained under sunlight within 45 min for 10 mg/L concentration. The oxidation follows a pseudo second order kinetic with an apparent rate constant of 11.5 × 10−3 L/mg/min according to the Langmuir–Hinshelwood model.

The spectra of NR solutions at pH ∼5: initially (10 mg/L) after adsorption, photolysis and photocatalysis under both artificial and natural lights.Figure optionsDownload as PowerPoint slide