Kinetics, Equilibrium and Thermodynamic Studies on Fe3+ Removal from Aqueous Solutions by Chemically Modified Brown Algae

Sargassum Vulgare was used as an effective biosorbent for the removal of Fe3+ from aqueous solutions. Results for batch operation are presented for biosorption onto algal biomass, raw and modified with HNO3, HCl, NaCl, and CaCl2. NaCl was selected as the best modifier for the algae surface for the improvement of the sorption capacity. Optimum biosorption conditions were determined as a function of contact time, biomass dosage, initial metal concentration, and temperature.
The Langmuir isotherm yields high regression values for a maximum monolayer sorption capacity of the modified biomass of 30.52 mg/g at optimum conditions (pH = 2, dose = 5 g/L, t = 120 min, and T= 298 K). This represents an increase of more than 50 % concerning the raw algae. The kinetics of sorption followed the pseudo-first-order rate equations and is fast enough to prove the technique feasible. The thermodynamic parameters showed that the adsorption of Fe3+ using algal biomass was feasible, spontaneous, and exothermic. Modified algae could be regenerated once using 0.001M EDTA solution, and a recovery of 90% of Fe3+ was obtained. Fourier Transform InfraRed (FT-IR) spectroscopy and Scanning Electron Microscopy (SEM) were used to characterize the surface of modified algae.