Leaching of waste battery paste components. Part 1: Lead citrate synthesis from PbO and PbO2


Sönmez M. Ş. , Kumar R. V.

HYDROMETALLURGY, cilt.95, ss.53-60, 2009 (SCI İndekslerine Giren Dergi) identifier identifier

Özet

In this study, as part of developing a new process which can avoid smelting and electro-winning, citric acid based reagents in aqueous media were reacted with PbO and PbO2. These two oxides are important components in the spent lead-acid battery paste and together account for up to 50% of the paste by weight. PbSO4, the main component in a spent battery paste accounting for the remaining 50%, is dealt with in Part 2 in a separate paper. Reaction between PbO and C6H8O7 center dot H2O or PbO2 with a mixture of C6H8O7 center dot H2O and H2O2 yielded lead citrate, Pb(C6H6O7)center dot H2O, which was characterised by XRD, SEM and FT-IR analysis. Optimal synthesis conditions were determined by investigating the effect of time, temperature, concentration, and the starting Pb oxide/water ratio. The optimal condition for leaching a mol of PbO at room temperature (20 degrees C) was found to be: 1 mol of (C6H8O7)center dot H2O solution; 1/3 as the starting PbO/water ratio and 15 min of reaction time. Pure citrate product, Pb(C6H6O7)center dot H2O was rapidly crystallized from the solution, in the leaching process. Leaching of PbO2 required the use of a mild reducing agent. For each mole of PbO2, the optimum condition at 20 degrees C was found to be: a solution containing 4 mol of C6H8O7 center dot H2O and 2 mol of H2O2; 1/5 as the starting solid PbO2/water ratio; and 60 min of reaction time. The product, as with PbO, was pure Pb (C6H6O7)center dot H2O compound. The remaining lead content of the filtrate solution was 0.017% and 1% corresponding to recoveries of 99.98% and 99% of lead as citrate, after the leaching/crystalization/filtration process with PbO and PbO2, respectively. Asymmetric stretching vibrations between 1599 and 1662 cm(-1), whereas symmetric vibrations between 1520 and 1327 cm(-1) for lead citrate synthesised from PbO and asymmetric stretching vibrations between 1600 and 1642 cm(-1) as well as symmetric vibrations between 1517 and 1326 cm(-1) for the product obtained from PbO2 revealed the strong IR adsorptions associated with a carboxylate structure. XRD data was identical to the well documented crystalline Pb(C6H6O7)center dot H2O compound from both the oxides, SEM revealed the formation of plate/sheet like morphologies. The difference in the column size of the Pb(C6H6O7)center dot H2O formed from the two lead oxides can be related to difference in the rate of the respective reactions. (C) 2008 Elsevier B.V. All rights reserved.