Stability of formed calcium carbonate crystals during the second carbonation at purification of sugarbeet raw juice

In this research، effects of different concentrations of carbon dioxide (to reach pHs 10. 5، 10. 2، 9. 9، 9. 6، 9. 3، 9، 8. 7، 8. 4 and 8. 1) and different temperatures (90، 95 and 100℃) on quality characteristics of the first carbonation juice were studied. For this purpose، stability of formed calcium carbonate crystals during the process of the first carbonation juice were evaluated by measuring effective alkalinity، total hardness، color، purity and conductivity total ash of the second carbonation juice. The appropriate effective alkalinity (1. 2 g CaO/100 mL) and lowest total hardness (30 gCaO/100 mL at 100 ℃) obtained at pH 9. 3 and 9 for the second carbonation، respectively. It was also observed that the color value of 2th carbonation juice decreased by reduction of pH and the lowest color value (1121. 15 IU at 100 ℃) obtained at pH 8. 7. The lowest conductivity total ash (90. 81 IU at 100 ℃) and highest purity of the second carbonation juice obtained at pHs 9. 3، respectively. By regarding the different physicochemical parameters at different pHs، it could be concluded that higher temperature (100℃) had more effects on studied characteristics. Finally it could be mention that most effective treatment was pH 9. 3 at 100 ℃. According to results of the research، pH≥9. 3 were suggested for stability of formed calcium carbonate crystals (stable form) because at pH≤9. 3 resulted in formation of calcium bicarbonate (unstable form) from calcium carbonate (stable form).