Quantitative Determination of Crystalline Na5P3O10 –I (Form-I) in Commercial Tripolyphosphate using X-ray Diffraction Patterns

The presence of Al3+, as an impurity, on the temperature of the polymorphic transformation of pentasodium tripolyphosphate Na5P3O10-II (low-temperature Form-II) into Na5P3O10-I (high-temperature Form-I) has been investigated using X-ray powder diffraction, IR spectroscopy, and scanning electron microscopy methods. The effect of Al3+ on the phase transformation was recorded between ignition temperatures of 350 and 450 °C. Al-free powders, ignited up to 450 °C, did not contain Form-I, while powders containing 0.5 or 1.0 wt % of Al were mixtures of Form-I/Form-II indicating that the presence of Al acted in favor of Form-I formation. Phase composition at temperatures of ignition higher than 500 °C was not dependent on Al presence. Na5P3O10 in all of the products ignited at 500−550 °C, whether Al-free or containing Al, was in Form-I. The presence of Al caused lower crystallinity and inhibited the grain growth of pentasodium tripolyphosphate while powder was ignited. Both phenomena are believed to act in favor of phase transformation at lower ignition temperatures.

Section: Resultsmentioning

confidence: 99%

Effect of Aluminum on Na₅P₃O₁₀ (Form-II → Form-I) Thermal Transformation

Kijkowska

Kowalski

Pawłowska-Kozińska

et al. 2004

“…That could imply that at high temperatures the STP structure is developed at even a short residence time of 15 min. Although the transformation temperature of phase II to phase I is reported to be in the range of 450 to 500 °C, it has been discussed that the transformation process is a complex phenomenon and is frequently not complete even in the compound calcinated above 500 °C . However as it was discussed with applied conditions in our case pure STP with phase I is achievable.…”

Section: Resultsmentioning

confidence: 74%

Analysis of Crystalline Structure of Sodium Tripolyphosphate: Effect of pH of Solution and Calcination Conditions

Sadeghi

Fayazi²

2012

Phosphoric acid and caustic soda were reacted in a controlled environment to obtain a solution of orthophosphates. Three solutions were prepared at three different pHs. The solutions were dried and calcinated to produce STP (sodium tripolyphosphate). The calcination process was performed at two temperatures. The evolution of STP formation (phase characterization) with time during calcinations was studied. The type of crystalline phase as well as impurity formation during the calcination process were investigated using WAXD (Wide-angle X-ray diffraction) and FTIR (Fourier transform spectroscopy) techniques. At lower pH of 6.48 STP could be formed purely in either phase I or II by setting the calcination temperature at 560 °C for the former and 340 °C for the later. Impurities such as Na4P2O7 and NaPO3 in product were developed as the pH of the solution was increased. At high temperature such as 560 °C, STP formation was fast, and therefore the phase development was less time dependent. At a lower temperature of 340 °C and specially lower pH, the phase development for STP was noticeably time dependent. At pH of 6.57 and 6.77 both phases I and II were observed for low calcinations temperature of 340 °C; however, at higher calcination temperature of 560 °C only phase I was observed. Although WAXD is usually used as a conventional method to study the phase characterization, it was found that FTIR can be considered a reliable technique to study such phase development.

“…Phase 2 is transformed into phase 1 at ∼417 °C. 1,[8][9][10][11][12] Sodium tripolyphosphate phase 1 undergoes hydration very quickly forming small hydrated salt crystals. Its solubility reaches the value characteristic for hexahydrate, starting from an initial value of ∼32 g/100 g solution.…”

Section: Introductionmentioning

confidence: 99%

“…Sodium hydroxide and thermal phosphoric acid can result in forming a product of a high purity level. 8,9,14,15 Sodium tripolyphosphate is usually produced by the sprayfurnace method. Sodium orthophosphates solution undergoes spray drying at the first stage of this process, and the dried mixture is calcinated in a rotary kiln at the second stage.…”

Section: Introductionmentioning

confidence: 99%

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Design and Analysis of Experiments for Obtaining High Bulk Density Sodium Tripolyphosphate

Banach

Kowalski

2010

The results of experiments for obtaining granulated sodium tripolyphosphate with bulk density adjustable within 1.00-1.05 kg/dm 3 and expected content of STPP crystalline phases are presented. The scope of experiments included the identification of factors with statistically significant impacts on the study object and the estimation of response surface. Because of the application of the Plackett-Burman design, 15 input factors could be evaluated regarding their impact significance and insignificant factors could be eliminated. Moreover, the Hartley design enabled the determination of a response surface based on the general regression equation in the form of a second degree polynomial with double interactions. The input factor values, determined on the basis of the prediction profile and desirability function, were used to perform a series of experiments to achieve STPP expected bulk density within the range of 1.00-1.05 kg/dm 3 .