Lead removal from synthetic wastewater by crystallization in a fluidized-bed reactor

A fluidized-bed reactor (FBR) was employed in the study to remove lead from the synthetic wastewater by crystallization of metal carbonate precipitates on surfaces of the sand grains. For the influent concentration up to 40 mg/L, lead removal efficiency reached 99% and the effluent concentration was less than 1 mg/L when the system was operated with a series of optimum conditions. Feed ratio C-T/[Pb2+] and recycle ratio should be maintained at 3 mol/mol and 0.67, respectively, and the hydraulic load should not be more than 22 m/h. The optimum pH for lead carbonate crystallization was 8 to 9, while the ratio of bed height to total height of the FBR was 0.25 to 0.3. In addition, the stable operation in terms of lead removal and solution turbidity was observed after a 380-minute operation. Analysis of the composition of crystals deposited on the sand grains surface showed that nearly 99% was lead salt. Furthermore the lead ions can be easily recovered by adding hydrochloride acid. This lead solution could be suitable for further industrial purposes.