Optimization and kinetic analysis of food dyes biosorption by Spirulina platensis

The biosorption of food dyes acid blue 9 and FD&C red no. 40 onto Spirulina platensis was studied. A full factorial design was used to analyze the effects of pH (2–4), stirring rate (50–400 rpm) and contact time (20–100 min) on biosorption capacity. In the best conditions, biosorption kinetics was analyzed and the experimental data were fitted with four kinetic models. The best conditions were: pH 2, 400 rpm and 100 min for acid blue 9, and pH 2, 225 rpm and 100 min for FD&C red no. 40. In these conditions, the biosorption capacities were 1653.0 mg g−1 for acid blue 9 and 400.3 mg g−1 for FD&C red no. 40. For both dyes, the Avrami kinetic model was the more appropriate to represent the experimental data. These results showed that the S. platensis is a suitable biosorbent for removal of food dyes from aqueous solutions.