Lead, Chromium and Cadmium Removal from Contaminated Water Using Phosphate Sorbents

Sorption of 3 poisonous metal ions (Pb2+, Cd2+, Cr3+) in aqueous solutions by two phosphate sorbents under dynamic and static conditions was studied. Phosphate sorbents (MgNH4PO4. H2O, Mg3(PO4)2. 6H2O) were synthesized by known procedures. The resulting crystalline samples were analyzed for the contents of Mg2+, Pb2+, P, N using spectrophotometric and elemental analysis methods. Likewise, the amounts of Pb2+, Cd2+, Cr3+ in solutions were determined before and after the sorption process using the atomic absorption method. The relative standard deviations for Pb2+, Cd2+, Cr3+ were 4.7%, 2.17%, and 1.61% and the detection limits were 5 g/L, 0.05 mg/L, and 0.1 mg/L, respectively. The sorbents showed a high performance in the purification of contaminated solutions under static conditions. The sorption capacity levels of Mg3 (PO4)2. 6H2O and MgNH4 PO4. H2O were 9.8m.mol/gr and 8.9m.mol/gr for Pb2+; 10.5m.mol/gr and 9m.mol/gr for Cd2+; and 6.6m.mol/gr and 5.3m.mol/gr for Cr3+, respectively. Pb2+ , Cd2+, Cr3+. sorption by inorganic phosphate sorbents from solutions is associated with complicated chemical transformations of the sorbents. A proper account of these transformations allows for the sorption process to be optimized. The data on Pb2+, Cd2+, Cr3+ sorption under static conditions (24-h contact of Mg3 (PO4)2. 6H2O, MgNH4PO4. H2O, with solutions at 20oC) and under dynamic conditions were obtained and the sorption behaviors of the metal ions were investigated in response to the sorbents used. It was found that Mg3 (PO4)2. 6H2O was the best sorbent for Pb2+, Cd2+, Cr3+ under dynamic conditions