Response surface modeling of bioremediation of acid black 52 dye using Aspergillus flavus.

Bioremediation is an efficient process to remove metals and dyes from solutions using different micro-organisms. In the present study, the efficiency of growing Aspergillus flavus (isolated from the effluent of an electroplating industry) to treat a synthetic solution of acid black 52 dye (a trivalent chromium complex dye) was investigated. Maximum removal of dye and chromium was observed to be 390 and 17.22 mg/L, respectively, at an initial dye concentration of 750 mg/L and at pH 4.5 in 50 hours in a batch bioreactor. The biomass concentration was reduced from 4.1 to 0.4 g/L with increasing dye concentration from 100 to 2,000 mg/L. The response surface modeling for color removal was performed using the range of initial dye concentration 200-400 mg/L, pH 4-6 and time 35-50 hours. The optimum conditions for maximum color removal (76.52%) were observed at initial dye concentration: 200 mg/L, pH: 4.75 and time: 50 hours. The deviation (-0.02%) showed a close agreement between the experimental and predicted values of color removal. The scanning electron microscopic and energy dispersive X-ray analyses indicated bioremediation of the dye.

Response surface optimization of bioremediation of Acid black 52 (Cr complex dye) using Aspergillus tamarii.

Bioremediation of the Cr complex dye (Acid black 52) was performed in batch and continuous modes using growing Aspergillus tamarii. The removal of Cu which may be present as an impurity was 100% at 100 mg/L initial dye concentration. The removal of color and Cr decreased from 87% to 4% and from 92% to 8%, respectively, by increasing dye concentration from 100 to 5000 mg/L in batch mode. The removal of color and Cr increased from 27% to 67.8% and from 32% to 72%, respectively, with increasing hydraulic retention time from 28 to 220 h at 100 mg/L dye concentration in continuous mode. For optimization of color removal using response surface methodology (RSM) the ranges of parameters were kept at dye concentration: 200-500 mg/L; pH: 4-6 and time: 35-50 hours. Maximum color removal suggested by the model was 85.6809% at initial dye concentration 200 mg/L, pH 5.25 and time 50 h. The validation experiments in batch and continuous modes were conducted at the optimum conditions as suggested by the RSM model. The theoretical and experimental responses of color removal were in close agreement in batch mode. The scanning electron microscopy, energy dispersive X-ray analysis, transmission electron microscopy and gas chromatography-mass spectroscopy analyses indicated biosorption and biodegradation of dye.