A comparative study on the degradation of azo dyes by fungal strain and silver nanoparticles

Abstract

Synthetic textile dyes have found to be recalcitrant and xenobiotic compounds in nature. Development of ecofriendly and efficient processes for biodegradation of these azo dyes is an important step in field of applications of nanotechnology. Present research work is focused on the treatment of two commonly used textile azo dyes acid red 151 (monoazo) and orange II (diazo) by silver nanoparticles (AgONPs) synthesized by A. niger. In present study silver nanoparticles (AgONPs) were used as photocatalyst in degradation process and were compared with its plain culture (A. niger) and also with commercial silver nanoparticles (AgONPs). Combined treatment was also applied to determine the extent of decolorization in which culture and nanoparticles both were used synergistically. First, different physiological reaction conditions (e.g. pH, temperature, initial concentration of dye and catalyst dosage) were optimized for maximum degradation of both dyes As a result the optimum conditions for degradation of dye obtained were pH 3 & 9, 30°C, 50 mg/l for AR 151 , 20 mg/l for Or II and 200 mg/l of Silver nanoparticles (AgONPs). The laboratory synthesized A. niger silver nanoparticles (AgONPs) efficiently decolorized the both dyes within 24 hours of incubation time while its plain culture (A . niger) takes more than 48 hours for the same practice. Laboratory synthesized silver nanoparticles (10- 20 nm) showed similar decolorization abilities as commercial silver nanoparticles. When dye decolorization was tested for both dyes, maximum decolorization was observed in case of AR151. Degradation of both azo dyes was investigated by UV Vis Spectrophotometer and Fourier Transform Infrared Spectroscopy (FTIR) and high performance liquid chromatography (HPLC). Cytotoxicity and phytotoxicity assessment of biodegradation products were carried out using brine shrimp bioassay and radish seed germination bioassay which confirmed that the treated dye samples were very slight toxic to water and soil organism.