Removal of high-level Fe from aqueous solution using natural inorganic materials: Bentonite (NB) and quartz (NQ)

Decontamination of high-level Fe³⁺ ions from a model aqueous solution using natural inorganic Quartz (NQ) and Bentonite (NB) has been studied. The adsorption equilibrium studies are performed with a constant initial Fe³⁺ ion concentrations (namely 100, 200, 300 and 400 mg.L^-1) and varying adsorbent weight. The adsorption percentages of Fe³⁺ ions increase sharply by increasing adsorbent doses, in which the adsorption percentage of Fe³⁺ using NB (approx. 60%) is found higher than in case of NQ (approx. 40%) in whole adsorption dosages. The maximum adsorption percentages of Fe³⁺ using both adsorbents are achieved within the first 60 minuets, and then desorption process is taken place. As the initial concentration of ions increases the percentage removal using NB decreases, while the adsorption using NQ is less affected by the initial concentration; it is found 40% in whole different initial concentration (50 - 400 mg.L^-1). The best temperature for the maximum adsorption is found 30 - 40°C for both adsorbents. The obtained experimental data has well described by Freundlich isotherm model into both NQ and NB. The Freundlich constant K_f for the adsorption of Fe³⁺ using NB is greater than using of NQ for the initial concentration 400 mg.L^-1. The negative value of ?G° confirms the feasibility of the process and the spontaneous nature of adsorption with a high preference for metal ions to adsorb onto NB (ΔG° = -13.9) more easily than NQ (ΔG° = -13.4).