Modeling Phosphate Anions Biosorption by Green Marine Algae Biomass

This study presents the modeling of phosphate anions retention by green marine algae (Ulva intestinalis), which provides information related to the mechanism of the biosorption process. The isotherm models used for the mathematical analysis of the experimental data were the Langmuir, Freundlich and Temkin models, while pseudo-first order, pseudo-second order and intra-particle diffusion models were used for the kinetic modeling. The results of the isotherm modeling show that the retention of phosphate anions occurs in a monomolecular layer, according to the Langmuir model <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mathrm{R}^{2}=0.9789, \mathrm{q}_{\max}=181.81$</tex> mg/g). From a kinetic point of view, biosorption is best described by the pseudo-second order kinetic model <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mathrm{R}^{2}=0.9994, \mathrm{c}_{0}=47.58$</tex> mg/L, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{k}_{2}=3.008\min^{-1},\mathrm{q}=10.52$</tex> mg/g close in value to the experimentally determined qexp = 10.50 mg/g).