Biosorption of food dyes onto Spirulina platensis nanoparticles: Equilibrium isotherm and thermodynamic analysis

► Spirulina platensis nanoparticles were used as dyes biosorbent. ► The maximum biosorption capacity was 1619.4 mg g−1, obtained at pH 4 and 298 K. ► The Sips model was the best to represent the equilibrium experimental data. ► Biosorption was exothermic, spontaneous and favorable. ► The biosorption of both dyes onto nanoparticles occurred by chemisorption.