Synthesis, structural and leaching studies of phospho-silicates: Bi1/3M1/6Zr2(PO4)(8/3)(SiO4)(1/3); M = Cd2+, Pb2+

Phospho-silicates compounds of zirconium, bismuth and lead or cadmium were prepared according to a sol-gel process. Lead compound crystallizes in a Na sicon type structure where bismuth and lead only occupy every second M1 sit e, i.e. the 3b site of R (3) over bar space group. A leaching study at room temperature was performed in acid or basic medium. The maximum value of me tal concentration is low even at low pH, and this concentration decreases r apidly when the pH increases. A surface process involving the release of me tal and phosphate ions is proposed. (C) 2001 Elsevier Science Ltd, All righ ts reserved.