Inositol Residue Preparation Of Food Grade Calcium Hydrogen Phosphate Technology Research

This work used inositol slag residue as raw material and dissolved it in hydrochloric acid to prepare the food grade calcium hydrogen phosphate.the refining NaOH and CaCl₂ solutions were selected as the neutralization agent after the trace fluoride was removed to discuss the optimized reaction conditions,such as extraction,purification,defluorination,neutralization.Finally the food grade product was obtained and met the national standard GB1889-2004.This work provided a practicable way to consume the inositol slag residue and at the same time obtain the high grade calcium hydrogen phosphate,which is beneficial to the sustainable development of economy.The extraction process of hydrochloric acid were designed to explore the various impact factors?such as hydrochloric acid concentration,dosage,reaction time,reaction temperature?to deep understand the reaction,in respectively.The final results showed that the hydrochloric acid concentration was 6mol·L-1;acid dosage was 1.35 times the amount of the theory;reaction temperature was 35?;reaction time was 65 min,under this condition the extraction rate will be reached to 99.51%.Using chemical precipitation to purify the crude phosphoric acid,in which Na2 S was selected to remove heavy metal ions,and BaCl₂ for SO₄^2-,the following step used active carbon to decolore the pigments in turn and obtained pure phosphoric acid.CaCl₂ and NaOH were treated by physical adsorption with various of adsorbents,such as activated carbon,activated clay,fly ash and ?-Al₂O₃.According to the experimental results,the best fluoride removal solution was determined,the fluoride impurity in CaCl₂ solution was carried out with ?-Al₂O₃,while the fluoride impurity was removed from NaOH solution by alkali modified activated carbon.Using defluorization refined CaCl₂ and NaOH solution reaction with refined phosphoric acid for neutralization reaction,the best value of parameters affecting the quality of products were got through a series of experiments eventually.This work prepared the food grade calcium hydrogen phosphate with large-uniform crystalline morphology and high-purity in quality,which meet the national standards.The product parameters as follows: fluoride content was 0.00464%;phosphorus conversion rate was 94.61% in the preparation process.This work shown the food grade calcium hydrogen phosphate technology was practicable and beneficial to the economic development.