Determination of iron, cobalt and nickel ions from aqueous media using the alkali modified miswak

This paper describes a simple, rapid, inexpensive method for the preparation of a new biosorbent based on the modification of miswak fibers by NaOH (AT-Miswak-F). The synthesized AT-Miswak-F sorbent was utilized as an efficient sorbent for the extraction and preconcentration of iron group metal ions from various water samples. In this study, it was found that Fe(III), Co(II) and Ni(II) ions were completely extracted (100%) at pH range of 3–7 and flow rate of 0.3–2.0 mL min⁻¹. Also, the sorption capacity of AT-Miswak-F for Fe(III), Co(II) and Ni(II) are 0.54, 0.24 and 0.15 mmol g⁻¹, respectively. Equilibrium was best described by Freundlich isotherm model (R² = 0.793) and the initial rate constants were 0.077, 0.054 and 0.035 mmol g⁻¹ min⁻¹, respectively. Under the optimized conditions, the method exhibited a detection limit of 1.4, 2.8 and 2.1 ng mL⁻¹ for Fe(III), Co(II) and Ni(II) ions in water samples with relative standard deviations of 2.6% (n = 4). The method was successfully applied for the determination of Fe(III), Co(II) and Ni(II) ions in sea, ground and contaminated water samples.