Influence of Temperature and Ion Concentration on Sedimentation Characteristics of Tricalcium phosphate (TCP) and Tristrontium phosphate (TSP) Precipitates

Physical and chemical variables of insoluble salts generally affect sedimentation characteristics of precipitates. In this research study, the effects of temperature and ion concentration on the sedimentation of tricalcium phosphate (TCP) and tristrontium phosphate (TSP) were studied. The focus was to determine the sedimentation kinetics such as rate, order and rate constant of TCP and TSP at varying temperatures using the modified initial rate (Isolation) method. It was observed that whereas effect of temperature was not significant, low concentrations (< 0.04M) of the metal and phosphate ions markedly influenced the initial sedimentation rates of TCP and TSP precipitates.TCP sedimentation order ranged between 0.63 and 1.23 at constant phosphate ions concentration and between 1.52 and 2.10 at constant calcium ions concentration. TSP sedimentation order also ranged between 0.58 and 1.31 at constant phosphate ions concentration and between 1.55 and 1.81 at constant strontium ions concentration. Furthermore, ranges of sedimentation rate constants were obtained. At constant phosphate ions concentration, 1.80 × 10^-4 - 1.57 × 10^-3 and 1.51 × 10^-4 - 2.45 × 10^-3 were obtained for TCP and TSP, respectively. At constant metal ions concentration 1.71 × 10^-5 - 9.54 × 10^-5 and 5.70 × 10^-5 - 1.12 × 10^-4 were respectively obtained for TCP and TSP. Data may be employed as additional design information for modeling physiochemical phosphate removal in water treatment technology.

Keywords
sedimentation rate; sedimentation characteristics; tricalcium phosphate; tristrontium phosphate.