Photocatalytic dye decomposition by bio-enzyme enriched TiO2/g-C3N4 nanocomposite and assessment of toxicity of resultant water using Catla catla fish

Abstract

Nanocomposite of TiO2/g-C3N4 enriched with enzyme prepared from bio-wastes (fruit and vegetable peels) was synthesized for the photocatalytic decomposition of toxic dye solution and the toxicity, if any, of the resultant water obtained after treatment was tested by exposing freshwater Catla catla fish to the treated water. The result was compared with the toxicity of the untreated test dye solution. The bio-enzyme powered TiO2/g-C3N4 nanocomposite exhibits enhanced degradation efficiency of 99% for methylene blue (MB) and 95% for methyl orange (MO) in 45 min, whereas the bare TiO2/g-C3N4 exhibits efficiencies of only 92% for MB and 90% for MO. The quantitative study showed that enzymes present in the system viz., protease, peroxidase, cellulase, amylase and lipase act as supporting catalyst and thereby improve the photocatalytic ability of the synthesized nanocomposite for effective dye degradation. The results showed the combined effects of composite partners and the bio-cocatalyst. Characterization of the prepared samples was performed using XRD, FTIR, SEM, RAMAN, UV, EDS and XPS and the results are correlated with the application concerned. The histology study was performed through paraffin wax method to evaluate the toxic effects of the industrial dyes on Catla catla fish by exposing the fish to different aquarium systems (Dye, Control and Treated water).