Effects of concentration of chloride anion on the morphology and microstructure of precipitates from lead nitrate solutions

Lead nitrate mixed with alkali in solution generates insoluble precipitates. The morphology and microstructure of the precipitates are dramatically influenced by the chloride anion concentration in the lead nitrate precursor solution. To intensively investigate the effect of the chloride anion concentration, we performed a series of controllable experiments with different concentrations of chloride anions (the concentration ratios of Pb ²⁺:Cl^- = 1:0, 1:0.2, 1:0.5, 1:1, 1:2, and 1:3 in the solution) at different solution temperatures of 90 and 80 °C. The results reveal that, with the increasing concentration of chloride anions, the colour of the precipitates changes from yellow to red and finally to white; the morphology of the precipitates changes from plate-like to rod-like; the crystal structure of the precipitates changes from β-PbO to a mixture of β- and α-PbO (or α-PbO), and finally to lead hydroxide. These results suggest that adding chloride could lead to the formation of rod-like morphology and simultaneously could restrain the dehydration of Pb(OH)₂.