Sustainable and solar light assisted photocatalytic degradation of methylene blue and malachite green dyes by Co3O4/g-C3N4 nanocomposite

Co3O4 nanoparticles were prepared by a simple co-precipitation method and subsequently hybridized with various weight percentages of g-C3N4 by a facile mixing method. The Co3O4/(x)g-C3N4 (where, x = 10, 20 and 30%) composites were analysed by several analytical techniques (XRD, TEM, FE-SEM, EDS, FT-IR, UV–Vis -DRS, XPS, PL, and BET surface area) to investigate their chemical composition, as well as morphological and optical characteristics. The photocatalytic degradation of methylene blue (MB) and malachite green (MG) was investigated by the Co3O4/(x)g-C3N4 with changing parameters, such as pH, catalyst dose, initial dye concentration and agitation time under solar light irradiation. Amongst the tested catalysts Co3O4/(20)g-C3N4 exhibited highest photo-degradation of MB dye (97%) at pH ∼ 11 and for MG (98%) at pH ∼ 9 in 60 min compared to 85 and 88% respectively for neat Co3O4 and 89 and 86% respectively for pure g-C3N4. The radical detection test was carried out with trapping agents Na2-EDTA, BQ and IPA that established the vital role of hydroxyl radicals in the photo-degradation of dyes. Eventually, the high stability and recyclability of the Co3O4/(20)g-C3N4 photocatalyst was confirmed after five consecutive runs. The mechanistic pathway of the dye degradation was explained by Z-scheme model on the basis of p-n hetero-junction.