Extraction of Cu(II) Ions Using Chloroform Solution of 4,4 ́-(1E,1E ́)-1,1 ́-(Ethane-1,2- Diylbis(Azan-1-YL- 1ylidene))BIS(5-Methyl-2- Phenyl-2,3-Dihydro-1H-Pyrazol-3-OL) (H2BuEtP) Under the Influence of Acids, Anions and Complexing Agents

The influence of selected acids, anions, and complexing agents on the removal of Cu(II) ions from aqueous solutions was studied using chloroform solutions of H2BuEtP both alone and in combination with HBuP. Chloroform solutions of the single Schiff base alone or in the presence of the synergist were added to the Cu (II) solutions containing known concentrations of the studied acids, anions, or complexing agents buffered at pH 6.0 and pH 8.75 and allowed to separate after an equilibration time of one hour. The absorbances of the aqueous raffinates were measured using AAS at 324.8 nm and compared with a standard Cu(II) absorbance to determine the percentage extraction (%E), distribution ratios (D), and the number of extraction batches (n), required for 99.9% Cu(II) removal. For the single ligand system for instance at pH 6.0, 0.005 mol/L H2SO4 among the acids exhibited the highest releasing effect, with a distribution ratio of 35.59 and an extraction efficiency of 97.28%, requiring two batches only to attain 99.9% Cu(II) extraction. Those exhibiting the highest releasing at the same pH, are 0.01 mol/L Cl- among the anions (D = 83.74, %E = 98.82%) and 0.05 mol/L SCN− among the complexing agents (D = 88.44, %E = 98.88%) also requiring only two batches for 99.9% Cu(II) ions extraction. The binary ligand system (H2BuEtP/HBuP) showed slightly improved extraction efficiency compared to H2BuEtP alone, in all studied systems requiring ≤ 2 batches only for 99.9% Cu(II) recovery, except for 0.1 mol/L tartrate at pH 8.75, 0.01 mol/L Cl− at pH 6.0, 0.05 mol/L HNO3, and 0.001 mol/L CH3COOH at pH 8.75, which required three batches. Statistical analysis of their distribution ratios showed significant differences (P ≤ 0.05) between single H2BuEtP and the mixed ligand systems in most cases, except for CH3COOH at pH 6.0 (P > 0.05). When compared to previous studies on Pb(II), U(VI), Fe(II), Ni(II), Cd(II) and Zn(II), the results indicated strong extraction potential for both single and multi-metal systems, with selective releasing effects supporting potential multi-metal separations. These findings highlight the efficiency of H2BuEtP and the synergistic effect of HBuP in Cu(II) extraction and provide insights for optimizing metal recovery from aqueous solutions.