Biosorption of Reactive Red 120 dye from aqueous solution using Saccharomyces cerevisiae: RSM analysis, isotherms and kinetic studies

Reactive Red 120 (RR 120) dye is widely used for textile dyeing in many countries. Most of the dye can cause skin reactions such as allergy, dermatitis and skin irritation, and are therefore considered as hazardous materials and toxic compounds for humans. Harvested cells of Saccharomyces cerevisiae were locally obtained from an Iranian Research Organization for Science and Technology. To provide an optimum condition for RR 120 removal by the response surface methodology, input factors contained the initial concentration of RR 120 5-50 mg L-1, dose of S. cerevisiae 3-10 g L-1, pH 3-10 and contact time 10-180 min. After completing each run, the suspensions were centrifuged at 10,000 rpm for 7 min. Finally, the absorbance of sample was read using UV-visible spectrophotometer at the wavelength of 511 nm. Based on the results, the obtained values from the adsorption of RR 120 were variables ranging from 23 to 96. The highest adsorption rate of RR 120 (99.97%) was obtained at RR 120 concentration of 16.25 mg L-1, yeast dose of 8.25 g L-1, pH 4.75 and contact time of 52.5 min. The dye removal efficiency was better in acidic pH. The Langmuir model was better described in the equilibrium biosorption data. The pseudo-second-order model was the suitable model to fit the experimental data.