Phosphate-assisted remediation of Pb(II) from Jarosite

Jarosite is an essential solid industrial waste material which is generated during the hydrometallurgical processing of zinc in smelters. Besides zinc and iron, Jarosite also contains toxic heavy metals like Pb, Cd, Al, Cr, Cu etc. due to which it is environmentally hazardous. Due to the presence of heavy metals, the useful Zn, Fe components cannot be utilized safely. Therefore, it is necessary to remove Pb(II), a major toxic element, to make it useful. In this report, a green process for immobilization of Pb(II) using phosphate materials (physiochemical adsorption) is discussed. Jarosite was used as a precursor for synthesis of the Zn Fe binary nano-composite.  Mitigation of Pb(II) by this process was assessed by the batch experiments, which showed significant reduction in leaching of Pb(II). The mechanism of Pb(II) immobilization involve the dissolution of phosphate materials (KH2PO4, NH4H2PO4 and CaH2PO4) to a lower pH≤3 followed by precipitation of Pb(II) in the form of pyromorphite complex. The results indicated that the concentration of Pb(II) was reduced by 90–95% which was pH dependent with a high uptake (325 ppm) of lead ion in the pH range of 5.5–6.0. This physicochemical process brings new perspectives for reuse of a polluting solid industrial waste.