Background and overview[1]
The natural mineral of zinc phosphate is called “paraphosphozincite”, which has two types: α-type and β-type. α-type: relative density 3.04, loses crystal water above 105°C; β-type: relative density 3.03, loses crystal water above 140°C. Zinc phosphate is insoluble in water or ethanol, but soluble in dilute acid, ammonia and ammonium salt solutions. Preparation method: obtained from the reaction of phosphoric acid solution and zinc oxide, or from the reaction of trisodium phosphate and zinc sulfate. Usage: Used as base material for phenolic, epoxy, alkyd and other coatings, as flame retardant for pigments, chlorinated rubber and organic polymer materials, as chemical reagent, and as preservative, astringent and dental cement powder in medicine. wait.
Preparation[2-3]
Report 1,
A method for preparing zinc phosphate, comprising the following steps:
(a) Synthesis of zinc phosphate, specifically including the following steps:
(1) Dilute 0.2 mole of concentrated phosphoric acid into a phosphoric acid solution with a concentration of 15wt% and add it to the reactor;
(2) Add 0.3 mole of citric acid to the phosphoric acid solution described in step (1) to dissolve;
(3) Add 0.3 mol of zinc oxide to quickly dissolve for 2-3 minutes under stirring conditions;
(4) Raise the temperature of the reactor to 55°C and react for 20 minutes to generate a reaction solution of zinc phosphate dihydrate crystals;
(5) Filter the reaction solution described in step (4), and set the filtrate aside for use. The filter cake is washed with hot water, pulverized, and dried at 90°C to obtain 422g of finished zinc phosphate dihydrate;
(b) Application of filtrate, including the following steps:
1) Cool the filtrate described in step (5) below 30°C and add 2g of citric acid to dissolve it; maintain an equimolar ratio with the added zinc oxide;
2) Then add concentrated phosphoric acid in the stoichiometric ratio required to react with zinc oxide, stir and dilute evenly;
3) Add zinc oxide to quickly dissolve for 2-3 minutes under stirring conditions;
4) The reactor is heated to 55°C and reacts for 20 minutes to generate a reaction solution of zinc phosphate dihydrate crystals;
5) Filter the reaction solution described in step 4), and set aside the filtrate. The filter cake is washed with hot water, crushed, and dried at 90°C to obtain the finished zinc phosphate dihydrate. After cooling the filtrate, it can be processed according to the above process. Continue to apply;
The purity of zinc phosphate dihydrate described in steps (4) and 4) is >99.9%, and it is rod-shaped crystals with a particle size of 5 to 10 μm.
This method can quickly dissolve zinc oxide to generate zinc phosphate, and the complexing reaction system solution can be applied, with higher reaction efficiency and less wastewater discharge; without adding citric acid, if the temperature control is not good, the dissolution of zinc oxide and zinc phosphate Precipitates tend to appear at the same time, a solution cannot be formed, it takes a long time, and the efficiency is low.
Report 2,
Stir and mix the zinc-containing waste residue and concentrated sulfuric acid until the pH value is 5.1, continue stirring for 5 minutes, then add hydrogen peroxide until the material liquid no longer begins to precipitate, continue stirring for 1 hour, then filter, and use 20% mass fraction of sulfuric acid aqueous solution to Adjust the pH value of the feed liquid to 3.2; mix and stir the phosphoric acid with a mass fraction of 20% and solid sodium hydroxide until the pH value is 8.0; dilute the previously prepared zinc sulfate solution with water to a concentration of 20°Bé, and add the previously prepared dihydrogen phosphate Dilute the sodium with water to a concentration of 15°Bé. Add a 20% caustic soda solution and the diluted disodium hydrogen phosphate solution to the diluted zinc sulfate solution, stir and mix until the pH value is 6.5, 20% The mass dosage ratio of caustic soda solution and diluted disodium hydrogen phosphate solution is 0.35:1, then stir, let stand, solid-liquid separation, wash to remove water-soluble salt, dry, and grind to obtain the product zinc phosphate.
Apply[4]
CN201810182429.5 reports an in-situ autothermal synthesis method of graphene oxide/zinc phosphate composite anti-corrosion pigment. The in-situ autothermal synthesis method adopted by the present invention cleverly utilizes the heat released during the reaction of phosphate radicals and zinc ions to generate zinc phosphate to increase the temperature of the reaction system, thereby greatly improving the dispersion of graphene oxide; and the dispersed graphene oxide adheres to On the surface of the zinc phosphate crystal nucleus, the growth of zinc phosphate crystals is effectively inhibited; when the reaction between zinc nitrate and sodium phosphate is completed, the temperature of the reaction system drops, and the dispersion of graphene oxide also decreases with the decrease of temperature, and the system The precipitation in the medium firmly adheres to the zinc phosphate material.�’s surface, finally obtained graphene oxide/zinc phosphate composite anti-corrosion pigment, providing a high-performance, low-cost anti-corrosion pigment for the field of metal anti-corrosion.
