Comparative studies on biosorption of Zinc Oxide and Iron Oxide nanoparticles using marine macro algae Kappaphycus alvarezii

Batch absorption experiments were carried out in order to examine the effect of various parameters such as pH, contact time, biomass concentration, and initial metal ion concentration. Absorption process was strongly dependent on the pH value and the initial metal concentration. The equilibrium absorption capacity varied with the concentration of metal oxide nanoparticles and maximum removal efficiency was observed at pH 3.5 in both the materials. Equilibrium experimental data were tested using the most common isotherms and the results are best fitted by Langmuir model for Fe2O3 and Freundlich model for ZnO. Theoretical absorption capacities for metal oxide nanoparticles were 70% and 80% respectively for both Fe2O3 and ZnO. Absorption kinetics were fitted by models including pseudo-first-order and pseudo-second-order models and the results demonstrated that pseudo-second-order kinetic model best describes the biosorption of metal oxide nanoparticles from aqueous solutions. Characterization of the biomass was done using FTIR, SEM along with EDX. The functional group of amino, carboxyl, phenolic hydroxyl, sulphonic group and C-O, -NH stretch showed a shift in the bands which might have involved in absorption.