Removal of Copper Ions from an Aqueous Solution Using Salvia officinalis and Alchemilla vulgaris Leaves as Natural Materials

This study demonstrated the use of two plant leaves, Salvia officinalis (SO) and Alchemilla vulgaris (AV), as natural absorbents to remove the copper ions (Cu2+) from an aqueous solution. The adsorption process was investigated under different operating conditions, including the initial concentration of the Cu2+ ion, contact time, pH, particle size, and adsorbent dose, at room temperature. The adsorbent materials were characterised using Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) and scanning electron microscope (SEM) tests. The best Cu2+ ion removal efficiency was 95.864% on SO leaves under the following optimal conditions: pH 6, a contact time of 75 min, an adsorbent material dose of 10 g/L, an initial Cu2+ ion concentration of 10 mg/L and a particle size of 75 µm. The maximum removal efficiency for Cu2+ ions was 91.566% on AV leaves with optimum parameters of pH 6, a contact time of 90 min, an adsorbent material dose of 15 g/L, an initial Cu2+ ion concentration of 10 mg/L and a particle size of 75 µm at 25 ± 5°C temperature. It was also found that the equilibrium results from the adsorption procedure were well fitted by the Freundlich isotherm model. The maximum adsorption capacity for Cu2+ ions was 16.949 mg/g on SO leaves and 10.101 mg/g on AV leaves. It was observed that the pseudo-second-order model provided a good fit to the Cu2+ ion removal rate per dry mass of plant leaves. The results conclude that both SO and AV leaves can be effectively applied as adsorbents for the removal of Cu2+ ions from an aqueous solution.