Phenomenological kinetic model for biosorption of cesium (Cs) by poly-γ-glutamic acid sodium salt (γ-PGANa)

A phenomenological biosorption kinetic model was developed for cesium (Cs) biosorption from radioactive wastewaters by poly-γ-glutamic acid sodium salt (γ-PGANa). The biosorption by non-living biosorbent γ-PGANa is controlled by the ion-exchange mechanism and the proposed kinetic model is based on the ion-exchange mechanism, which is disassembled in two steps, i.e., Step 1 in which Na⁺ from the functional group (–COONa) in γ-PGANa is released and Step 2 in which Cs⁺ and H⁺ are competitively adsorbed on negatively charged functional group −COO⁻. The validation of the proposed phenomenological kinetic model was conducted using the present experimental data for dynamic changes in Cs concentration obtained with the wide ranges of operation conditions at pH from 3 to 9, the dosage of γ-PGANa from 0.1 to 0.6 gL⁻¹, the initial Cs concentration from 0.0001 to 0.1 gL⁻¹, and temperature from 298 to 318 K. The capability of the proposed kinetic model was proved by reasonable agreement between the model predictions and the experimental results.