The aqueous solution of sodium tripolyphosphate is weakly alkaline (the PH value of 1% aqueous solution is about 9.7), and it forms a suspension (similar to emulsion) in water with a PH of 4.3-14, i.e. dispersion. Sodium tripolyphosphate can also enable liquid and solid particles to be better dissolved in liquid (such as water) medium, making the solution completely transparent in appearance, like a real solution, which is solubilization. As sodium tripolyphosphate has the above unique properties, it becomes an important ideal raw material in washing powder. 
Sodium tripolyphosphate is prepared by neutralizing phosphoric acid with soda ash to form sodium orthophosphate, and then condensing. There are two methods to produce phosphoric acid: wet method and thermal method. Wet process is to react phosphate rock with inorganic acid (usually sulfuric acid or hydrochloric acid), then extract and refine to obtain phosphoric acid. The thermal method is to roast phosphate rock together with coke and silica in an electric furnace, reduce phosphate rock to phosphorus, and then oxidize and hydrate to obtain phosphoric acid.
The process of preparing sodium tripolyphosphate from orthophosphate is relatively simple, with short process and convenient control operation. There are mainly two methods.
(1) spray drying-converter polycondensation two-stage method: the spray dryer is a cylinder, the upper part of which is connected with a horizontal burner with a gas nozzle. Gas with a temperature of 400-500 deg c is introduced into the upper part of the spray drying tower through a burner, and meanwhile, orthophosphate solution is injected by a high-pressure (4.2MPa) pump. Dried products containing less than 5% water are continuously taken out from the lower part of the dryer. The orthophosphate mixture is dehydrated and polycondensed into sodium tripolyphosphate in a rotary furnace. The method is characterized in that the product does not need to be crushed, the spray dryer has high drying efficiency, the dried materials are uniform, and delamination phenomenon does not occur. The disadvantage is that drying and polycondensation are carried out in two stages, and dust loss is large when directly heating and dehydrating.
(2) drying-dehydration one-stage method: slurry is sprayed into a rotary furnace, and hot gas or petroleum is burnt in the furnace to heat. The annular baffle divides the furnace into a flame section and a heating section. In the heating section, the material is finally dehydrated and polycondensed to be converted into sodium tripolyphosphate. The cooling cylinder is connected with the rotary furnace as a whole, the granular products coming out of the cooling cylinder are ground in a grinding machine, and a small amount of powder brought out of the furnace is recovered in a cyclone separator. This method combines drying, dehydration and cooling in one unit equipment, which greatly simplifies the process, has high heat utilization rate, and can reduce infrastructure investment and improve working conditions.
1. Appearance: white particles or powder
2. Industrial sodium tripolyphosphate shall meet the following requirements (GB9983-2004)
Excellent products, first-class products, qualified products
Whiteness,% ≥ 90.085.080
Phosphorus pentoxide (P2O5),% ≥ 57.0 56.5 55.0
Sodium tripolyphosphate (Na5P3O10) content,% ≥ 96.0 90.0 85.0
Water insoluble content,% ≤ 0.10 0.10 0.15
Iron content (Fe),% ≤ 0.007 0.015 0.030
PH value (1% solution) 9.2-10.0
The sieving rate of the particle size passing the 1.00mm test sieve is not less than 95%
I preparation of reagents
1。 Potassium acetate buffer (pH5.0) Take 78.5g of potassium acetate, dissolve it in 1000mL of water, and adjust the solution to pH5.0 with acetic acid. Add several milligrams of mercury iodide to inhibit mold growth.
2。 Take 22.35g of potassium chloride from 0.3 mol/L potassium chloride solution, dissolve in water, add 5mL of the above potassium acetate buffer, dilute with water to 1000mL, and mix well. Add mercury iodide, mg.
3。 Take 4.7g of potassium chloride from 0.6 mol/L potassium chloride solution, dissolve in water, add 5mL of the above potassium acetate buffer, dilute with water to 1000mL, and mix well. Add mercury iodide, mg.
4。 Take 74.5g of potassium chloride from 1mol/L potassium chloride solution, dissolve it with water, add 5mL of the above potassium acetate buffer, dilute it with water to 1000mL, and mix. Add mercury iodide, mg.
II. Chromatographic Columns
Using a standard chromatographic column with a length of 20-40 cm and an inner diameter of 20-28 mm, seal a coarse-hole sintered plate. If there are no stoppers respectively, connect a short polyethylene hose at the outlet of the column, and then connect a stopcock with an aperture of 3-4 mm.
Close the stopcock, fill the space between the sintered plate and the stopcock with water, and connect a vacuum line to the stopcock. Using 100-200 mesh or 200-400 mesh strong alkali anion exchange resin (Dowex 18) or styrene/divinylbenzene ion exchange resin of similar grade, and water according to the ratio of 1:1 to make each slurry. Decant the extremely fine particles and foam, and repeat this for 2-3 times, or until there is no fine suspended matter or foam. Fill the chromatographic column with slurry, open the stopcock, and vacuum the tree bed until the water level is slightly higher than the top of the resin bed, then immediately close the stopcock. Under no circumstances should the water level be lower than the resin level. This is repeated until the resin is 15cm higher than the sintered plate. Take a piece of filter paper closely attached with glass fiber and place it on the top of the resin bed, then take a perforated polyethylene dish and place it on the filter paper. A layer of loose glass wool can also be installed on the top of the resin bed. Plug the top of the column with a rubber stopper, insert a 7.6cm long capillary tube (inner diameter 1.5mm, outer diameter 7tnm) in the center of the rubber stopper, and extend about 12mrn below the stopper. Connect the capillary tube to the lower tube of a 500mL separatory funnel with a length of polyethylene hose. Place the separatory funnel in the iron ring above the column. Close all stoppers and add 100mL of water to the separatory funnel to wash the chromatographic column. First unscrew the stopcock of the separatory funnel, and then release the stopcock of the chromatographic column at a flow rate of about 5mL/min. When the separatory funnel is completely emptied, first close the column stopcock, and then close the separatory funnel stopcock.
Accurately weigh about 500mg of test sample that has been dried at 105℃ for 4 hours, put it into a 250mL volumetric flask, dissolve it with water and mix it after constant volume. Take 10.0mL of this solution and transfer it to the separatory funnel. Open the two stoppers to allow the solution to flow into the chromatographic column. Rinse the separatory funnel with water and discard the eluate.
370mL of 0.3mol/L potassium chloride solution was added to a separatory funnel, and the solution was passed through a chromatographic column, and the eluate was discarded. Add 250mL of 0.6mol/L potassium chloride solution to the separatory funnel, let the solution pass through the chromatographic column, and collect the eluate in a 400mL beaker. (In order to ensure a clean chromatographic column during the next round of operation, 100mL of 1mol/L potassium chloride solution can be passed through the chromatographic column, with several drops of solution (TS-148), and the solution is neutralized with concentrated ammonia test solution (TS-14). Add 1g ammonium nitrate to crystallize, stir to dissolve, and cool. Add 15mL ammonium molybdate test solution (TS-22) under stirring, and stir strongly for 3min, or place for 10 ~ 15 min under intermittent stirring. The contents of the beaker were filtered by suction filtration, and a 25 mm high porcelain funnel was used, in which a 6 ~ 7mrn thick pulp cushion was placed, and the cushion was covered with a layer of diatomite suspension. After the contents of the beaker are transferred to the filter, the beaker is washed with 1% sodium nitrate or potassium nitrate solution for 5 times and 10mL each time, and the washing liquid is passed through the filter. Then use this lotion to wash the filter 5mL each time 5 times. Return the filter pad and sediment to the beaker, rinse the funnel with water and flow into the beaker, then dilute to about 150mL with water. 0.1mol/L sodium hydroxide is added dropwise through a burette until the yellow precipitate is dissolved, and then 5 to 6 RNL is added. Add several drops of phenolphthalein test solution (TS-167) and titrate excess alkali with 0.1mol/L nitric acid. Finally, it was titrated with 0.1mol/L sodium hydroxide until pink appeared for the first time. The difference between the total amount of 0.1mol/L sodium hydroxide added minus the amount consumed by titration of nitric acid is the amount of 0.1mol/L sodium hydroxide consumed by phosphomolybdate (V; In mL). Finally, the amount of sodium tripolyphosphate (Na5P3O10) in the sample is calculated according to the formula of 0.533×25V, in mg.
The aqueous solution of sodium tripolyphosphate is weakly alkaline (the PH value of 1% aqueous solution is about 9.7), and it forms a suspension (similar to emulsion) in water with a PH of 4.3-14, i.e. dispersion. Sodium tripolyphosphate can also enable liquid and solid particles to be better dissolved in liquid (such as water) medium, making the solution completely transparent in appearance, like a real solution, which is solubilization. As sodium tripolyphosphate has the above unique properties, it becomes an important ideal raw material in washing powder.