Immobilization of borates and phosphates anions with saturated lime solutions

Abstract

Portland cements are currently used in the nuclear industry in order to immobilize and to stock the nuclear wastes. The low radio-element concentrations are associated in aqueous solutions with high borate and phosphate anions amounts. When mixed with cements, those anions will hugely influence the cement setting and hardening. The aim of this study is to characterize the precipitated phases obtained when adding borate and phosphate anions to alkaline lime-saturated solutions simulating the interstitial phase of cement pastes. The experiments have been carried out at two temperatures: 20°C and 55°C. For both, the precipitates obtained, as a function of p H, have been identified and their solubility products determined according to a thermodynamical treatment developed here.