Chemical preparation, kinetics of thermal behavior and infrared studies of Pb3(P3O9)2.3H2O and Cd3(P3O9)2.14H2O

Abstract

Chemical preparation, thermal behavior, kinetic and IR studies are given for the cyclotriphosphates Pb3(P3O9)2.3H2O and Cd3(P3O9)2.14H2O. The later cyclotriphosphates have never been studied except their crystallographic characterization and are stable in the conditions of temperature and pressure of our laboratory until 343K. The final products of the dehydration and calcination of Pb3(P3O9)2.3H2O and Cd3(P3O9)2.14H2O, under atmospheric pressure, are respectively their long chain polyphosphates, [Pb(PO3)2]∞ and β[Cd(PO3)2]∞. The intermediate product of the dehydration of Cd3(P3O9)2.14H2O, under atmospheric pressure, is its long chain polyphosphate form α, α[Cd(PO3)2]. [Pb(PO3)2]∞ and β[Cd(PO3)2]∞ are stable until their melting points at respectively 946K and 1153K. Two different methods, Ozawa and KAS have been selected in order to study the kinetics of thermal behavior of the cyclotriphosphates Pb3(P3O9)2.3H2O and Cd3(P3O9)2.14H2O for the first time. The kinetic and thermodynamic features of the dehydration, of the cited cyclotriphosphates, were determined and discussed on the basis of their crystalline structure. [Pb(PO3)2]∞, α[Cd(PO3)2] and β[Cd(PO3)2] have many applications in industry such as corrosion inhibitors.