Background and overview[1-3]
Sodium orthophosphate is also called “sodium orthophosphate”. Chemical formula Na3PO4. There are two types of hydrates. Its decahydrate is a colorless octahedral crystal with a melting point of 100°C and a relative density of 2.536. It is soluble in water. Its dodecahydrate is a colorless triangular crystal with a relative density of 1.02 and a refractive index of 1.446 and 1.452. It is soluble in water and insoluble in ethanol and CS2. It decomposes when heated to 73-77°C and loses 12 molecules of water when heated to 100°C. Uses: used as chemical reagents, water softeners, phosphating agents for steel containers, etc.
Sodium orthophosphate is used as water softener and detergent, metal descaler, boiler anti-scaling agent, water softener in paper dyeing, and glue for the production of waxed paper in the chemical, textile, printing and dyeing, papermaking, power generation and other industries. It is a pH buffer for adhesives, a fixing agent for printing and dyeing, an enhancer for fabric mercerization, and a coagulant for rubber latex; it can improve the complex metal ions, pH value, and ionic strength of food, and can also improve the texture of food. Strength and water retention.
Sodium orthophosphate, also known as sodium phosphate, sodium orthophosphate, etc., appears as colorless or white crystals and is an inorganic salt with a wide range of uses. Sodium orthophosphate is used as water softener, boiler cleaner and detergent in metallurgy, chemical industry, textile, printing and dyeing, papermaking, mechanical and electrical industries, etc. It can also be used as metal rust inhibitor. Sodium orthophosphate can also be used as a rust inhibitor for metals, a juice purifier in the sugar industry, a cleaning agent and detergent in the daily chemical industry, a developer in the film industry, a coagulant in the rubber industry, and a coagulant in the printing and dyeing industry. Penetrant, desiccant and fabric mercerizing enhancer, etc.
In addition, sodium orthophosphate has the function of passivating and inactivating viruses, and can be used for the treatment of seeds and utensils. Food-grade sodium orthophosphate can be widely used in food, biocomposite materials, antibacterial materials, high-end handicrafts, synthetic plastics, toothpaste, pharmaceuticals and other fields. The global annual consumption of food-grade sodium orthophosphate is more than 50,000 tons.
Preparation[2]
(1) Impurity removal by wet phosphoric acid:
Use centrifugation or pressure filtration to remove solid impurities contained in wet phosphoric acid with a concentration of 15% to obtain phosphoric acid for later use;
(2) Synthesis reaction of intermediates:
Put the phosphoric acid obtained in step (1) into the intermediate synthesis tank, adjust the phosphoric acid concentration, and heat to 60°C. Under stirring conditions, add carbon amide and phosphoric acid to carry out the synthesis reaction. The amount of carbon amide added is according to the amount of the carbon amide and the phosphoric acid. The molar ratio of phosphoric acid is determined to be 1.06:1. Stir, dissolve, and incubate the reaction. The reaction time is 80 minutes;
(3) Cooling and crystallization to obtain the intermediate:
After the synthesis reaction is completed, put the obtained intermediate slurry into a cooling crystallization tank and cool it to a temperature of 20°C for crystallization. After precipitation, centrifuge and retain the filter cake. The filter cake is the intermediate and is placed in the intermediate storage bin. , for later use; the filtrate is phosphoric acid mother liquor containing a certain amount of impurities, which is transported to the ammonium phosphate compound fertilizer device as a raw material for the production of compound fertilizer;
(4) Preparation of sodium orthophosphate:
Send the intermediate into the synthesis tank, add a certain amount of water, dissolve it completely under stirring, and slowly add a measured amount of solid sodium hydroxide for mixing reaction. The molar ratio of the intermediate to sodium hydroxide is 0.95:3, control the addition speed of sodium hydroxide to adjust the temperature in the synthesis tank to 50°C, and stir the reaction for 100 minutes; after the reaction is completed, cool the sodium orthophosphate slurry to a temperature of 20°C, cool and crystallize, and put the crystals after precipitation. Enter the centrifuge for centrifugal separation. The filtrate is a slurry containing carbon amide. The carbon amide is recovered and returned to the intermediate synthesis tank in step (2) for the production of intermediates. The filter cake is a sodium orthophosphate product. The product quality reaches First-class industrial grade sodium orthophosphate standard, dried and packaged.
Purification method[3]
In the reaction device equipped with a stirrer and temperature controller, add 500ml of high-purity water with a resistivity value greater than 17MΩ·cm and 100g of industrial sodium orthophosphate (Na3PO4·12H2O). After stirring and dissolving at room temperature, add organic amine 1g modified starch chelating agent, 2g sodium sulfide, stir at room temperature for 6 hours, filter out the chelating agent, the resulting liquid acrylic resin is filtered through a cellulose acetate membrane with a pore size of 0.22 μm, and the filtrate is decompressed at a temperature of 40 to 60°C Most of the water was distilled off, cooled to 0°C for crystallization, and then suction filtered. The solid obtained was vacuum dried at 40°C for 12 hours to obtain 92g of purified sodium orthophosphate.
The test results show that all indicators of the product comply with the standard GB25565-2010 (food additive trisodium phosphate). See the table below for specific test data.
Apply[4]
Used to prepare potassium dihydrogen phosphate.
1) Dissolution of sodium orthophosphate:
Mix the sodium orthophosphate solid and water in a certain proportion until the sodium orthophosphate solid is completely dissolved;
2) Add phosphoric acid to adjust acidity:
Filter the obtained solution, initially remove impurities, calculate the required phosphoric acid based on the trisodium content in the filtrate, add phosphoric acid to the filtrate and stir for 30 minutes to obtain a disodium hydrogen phosphate solution;
3) Sodium dihydrogen phosphate for impurity removal:
Add sodium hypochlorite solution to disodium hydrogen phosphate solution for disinfection;
Add an oxidizing agent to oxidize the impurities in the solution from low-valence elements to high-valence elements, and add corresponding impurity removers to remove impurities;
4) Preparation of potassium dihydrogen phosphate:
Remove impurities from what are antioxidants?Add potassium chloride to the �� disodium hydrogen phosphate solution to obtain a potassium dihydrogen phosphate solution;
5) Potassium dihydrogen phosphate crystal:
Cool the potassium dihydrogen phosphate solution to separate sodium chloride and avoid iron elements, then crystallize and dry it to become a solid potassium dihydrogen phosphate product.
