Neutralization method for tricalcium phosphate production: Optimization using response surface methodology

The tricalcium phosphate Ca-3(PO4)(2) (TCP) has been synthesizing in an optimized condition based on the surface modeling methodology; this material has been produced using the neutralization synthesis reaction and extensively characterized by XRD, FT-IR, and ICP. Based on those characterizations, the obtention of this material was strongly depending on the final molar ratio of the reagents, which is influenced by a couple of hydrodynamic and static factors. For an efficient optimization of the TCP production, the central composite design (CCD) was established regarding the acid flow(20-100 mL.min(-1)), the maturation time (10-240 min), and the reaction pH (5.3-7.6) as they are the most influents factors. The combination of the response surface methodology and the central composite design was used to assess the influence and magnitude of each factor contribution. The CCD results and their subsequent analysis of variance (ANOVA) provides an empirical equation on the expected response; the proposed empirical model provides a value of R-2 and R-Adjusted(2) more than 0.92 and 0.82 respectively. In fact, the analysis of the residuals shows that the experimental response follows a Henry line and present a perfect normality. Among the model factors, The Pareto analysis reveals that the acid flow and the pH and some of their interactions have a significant contribution to the desired molar ratio. The optimization with the Centrale composite design had illustrated both that the optimal conditions for the obtention of a pure TCP, are as the following: an acid flow (60 mL. min(-1)), a maturation time (60 min) and reaction pH of (6). And also, it was proved that the model can predict the results of other experiments in the same experimental domain.