Alizarin red-S removal from aqueous solutions using Saccharomyces cerevisiae: kinetic and equilibrium study

Alizarin red-S (ARS) is a type of azo dye that is widely used for dyeing of wool and nylon. It is toxic and carcinogenic and can cause a serious hazard to aquatic ecosystems. The ARS removal was experimentally conducted using the Saccharomyces cerevisiae biomass under various parameters of pH (3-11), contact time (20-180 min), the ARS concentration (25-100 mg L-1), and yeast dose (0.1%-1.3% w v(-1)). After completing each run, the suspensions were centrifuged at 10,000 rpm for 7 min. Finally, the absorbance of samples was read by UV-visible spectrophotometer at the wavelength of 427 nm. The maximum removal efficiency of ARS (68.51%) occurred at the conditions of ARS concentration of 50 mg L-1, S. cerevisiae dose of 0.4% w v(-1), solution pH of 3, and contact time of 120 min. Biosorption process is desired at low pH under acidic conditions. The equilibrium data of the biosorption process were well fitted with the Langmuir model (R-2 = 0.99). Results indicated that the removal efficiency of ARS has an increasing rate from 10 to 80 min. The best kinetic model to fit experimental data was the pseudo-second-order. The results of the current study confirmed that S. cerevisiae could be used as a low-cost biosorbent for eliminating ARS from aqueous solutions.