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.

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