Metal solution preparation
Solutions of Cu2+ and Cr3+ ions were prepared by dissolving predefined amounts of CuSO4 and Cr(NO3)3, respectively, in distilled water, so as to achieve concentrations of 1000 mg/L in each flask. Different initial concentrations of metal ions were prepared by diluting the stock solution. The pH of the solutions was adjusted using 0.1 N HCl and 0.1 N NaOH to achieve the desired values.
2.3. Isotherm experiments
Experiments were carried out in batch mode. 100 mL samples of aqueous solutions of metal ions at different initial concentrations (10–1000 mg/L) and at adjusted pHs were transferred into 250 mL Erlenmeyer flasks. Pre-defined amounts of the sorbent were added to these solutions. After 24 h, solutions were filtered and metal ion concentrations in the filtrate were determined. Concentrations of metal ions in samples were determined by atomic absorption spectroscopy (AAS). Concentration of metal retained in the sorbent phase (qe, mg/g) was calculated from the expression:
equation(1)
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