Analysis of mass transfer kinetics in the biosorption of synthetic dyes onto Spirulina platensis nanoparticles

In this research, the mass transfer kinetics for the biosorption of synthetic dyes (acid blue 9 and FD&C red no. 40) by Spirulina platensis nanoparticles was analyzed under different experimental conditions. The external mass transfer model (EMTM) and the homogeneous solid diffusion model (HSDM) were employed to study the mass transfer kinetics and also to estimate the values of external mass transfer coefficient (kf) and intraparticle diffusion coefficient (Dint). The Biot number (Bi) was used to verify the importance of external mass transfer in relation to intraparticle diffusion. The values of external mass transfer coefficient (kf) ranged from 1.67 × 10−6 to 11.40 × 10−6 cm s−1 and the intraparticle diffusion coefficient (Dint) ranged from 0.70 × 10−14 to 4.30 × 10−14 cm2 s−1. The Biot numbers (0.53 ≤ Bi ≤ 10.33) showed that, for both dyes, the biosorption onto S. platensis nanoparticles was controlled simultaneously by external mass transfer and intraparticle diffusion.

► The mass transfer mechanism of dyes biosorption by Spirulina platensis nanoparticles was studied. ► The external mass transfer model and the homogeneous solid diffusion model were applied. ► The external mass transfer coefficients ranged from 1.67 × 10−6 to 11.40 × 10−6 cm s−1. ► The intraparticle diffusion coefficients ranged from 0.70 × 10−14 to 4.30 × 10−14 cm2 s−1. ► Biosorption was controlled by the external mass transfer and intraparticle diffusion mechanisms.