Abstract
This study has investigated the solvent extraction of cadmium and lead ions from an aqueous solution in nitrate medium using aminooctyldiphosphonic acid (AODPA) as extractant in chloroform. In order to establish spectrophotometrically the concentration of metal ion in the aqueous phase before and after extraction, the Arsenazo III method was used. The effects of several extraction parameters on the extraction of these metals ions including volume ratio between the aqueous and organic phases (1–5), extraction kinetic time (0–30 min), molar ratio Q (1–5), addition of HNO3 (pH =2–6), addition of KNO3 (0.01 – 1M), temperature (10–40°C) and the synergetic effect by adding TOPO (solvating agent) were evaluated. Thermodynamic parameters including the Gibbs free energy (ΔG0),enthalpy (ΔH0), and entropy (ΔS0) were calculated. Performed experiments showed that Pb (II) can be extracted till 73% when Cd (II) can be recovered completely after two cycles. The extraction of both metallic ions was spontaneous, endothermic and with a slight randomness. Positive synergetic effect was observed at a chelating agent/TOPO ratio of 3. It is a very encouraging result which can lead us to recover cadmium and lower the concentration of lead from wastewater.
Highlights
The most rejected heavy metals are very polluting and dangerous
Cadmium, used in several industrial and agricultural processes as well as mining activities and designed carcinogenic by the United States (US) National Toxicology Program can increase the contamination of water and wastewaters around the world.[4,5]
Reagents and apparatus The reagents used in this study were: Lead nitrate tetrahydrate Pb (NO3)2 4H2O (99%, Riedel De Haen, 10099-74-8), Cadmium nitrate tetrahydrate Cd (NO3)2 4H2O (99%, Riedel De Haen, 10022-68-1), Arsenazo III C22H18AS2N4O14S2 (99%, Aldrich, 216-788-6), Nitric acid (65%, Panreac, 7697 37 2), Acétic acid CH3COOH (80%, prolabo, 64-19-7), Sodium Acétate CH3COONa (98%, prolabo, 6131-90-4), Potassium nitrate KNO3 (99%, Riedel De Haen, 7757-79-1),Chloroform CHCl3 (99% Riedel De Haen, 67-66-3), Aminooctane C8H19N (Aldrich, 111-86-4), Phosphorus acid (H3PO3, Aldrich, 13598-36-2), Hydrochloric acid (HCl, Riedel de Haen, 7647-01-0), Formaldehyde (HCHO, Aldrich, 50-00-0), Acetone (C3H6O, Aldrich, 67-64-1), Tri octyl phosphine oxide TOPO ((C8H17)3PO, 78-50-2) and aminooctyldiphosphonic acid (AODPA).[14]
Summary
Lead and its inorganic derivatives are classified as category 2B (potentially carcinogenic to humans).[1] Lead modifies the cellular functioning by disrupting different physiological processes. It can cause blood anemia and renal effects (renal failure). Inhalation, ingestion or skin penetration, even in very small quantities, can cause irritation in the stomach, leading to vomiting and diarrhea, renal insufficiency and, at high doses, chronic bronchitis, fibrosis, emphysema, damage to the bone system, kidney stones and increased blood pressure.[7,8,9,10]
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