Clay semiconductor hetero-system of SnO2/bentonite nanocomposites for catalytic degradation of toxic organic wastes

SnO2/Bentonite (SBT) nanocomposites containing varying amounts of SnO2 (10, 20 & 30 wt%) were prepared by co-precipitation method and characterized. X-ray diffraction studies indicated the tetragonal rutile structure of SnO2 nanoparticles located on the surface bentonite layers. FTIR analysis data confirmed the presence of SneO bonds. TGA indicated higher thermal stability of the SBT nanocomposites. FESEM studies ascertained the incorporation of globular SnO2 crystallites into the numerous nano-flakes of clay particles. The tau plot from UV-Visible DRS studies revealed that the greater loading of SnO2 reduced the band gap energy and might be due to defects in the crystal system. The reduced intensity of PL peaks in SBT composites compared to SnO2 indicated the greater catalytic activity of the nanocomposites. Pristine SnO2 causes photodegradation on UV irradiation where as SBT nanocomposites degrade these dyes in visible light itself. It is interesting to note that the SBT nanocomposites show photocatalytic degradation of cationic and anionic dyes by 5 min whereas SnO2 nanoparticles take 3 h for complete discolouration. The results showed that modification of SnO2 nano metal oxide with bentonite increased the percentage discoloration of the dyes from 70 to 100%. Hence nano sized SnO2 supported bentonite acts as an efficient and environmentally benign photocatalyst.