Application of the preparation method of trisodium phosphate

Trisodium Phosphate

[Physical and chemical properties] The chemical formula of trisodium phosphate is Na ₃ PO ₄ (anhydrous grade), and the relative molecular mass is 164

[Preparation]

(1) Neutralize phosphoric acid with soda ash to obtain disodium hydrogen phosphate solution, concentrate, add liquid caustic soda, continue to concentrate, wait for all CO ₂ generated during the reaction to escape, filter on a filter press

(2) Xu Zhangsong and others used sodium tripolyphosphate neutralization waste residue as raw materials to prepare trisodium phosphate

The main components of alkali slag are iron, aluminum, calcium, magnesium phosphate, fluoride and soluble phosphate, etc.

During the neutralization process of magnesium phosphate, Mg ₃ (PO ₄ ) _{2 is} partially generated due to partial over-alkali , and this substance is difficult to be decomposed by NaOH

MgHPO ₄ +3NaOH→Mg(OH) ₂ +Na ₃ PO ₄ +H ₂ O

In addition, Al(OH) _{3 is} partially dissolved by NaOH to form sodium aluminate:

Al(OH) ₃ +NaOH→NaAl(OH) ₂ +2H ₂ O

According to the solubility product theory, since the hydroxide solubility product of iron and aluminum is much larger than their phosphate solubility product, most of the water-insoluble P ₂ O ₅ in the waste residue can be transferred to the aqueous solution and removed through the filtration process.

The specific operation method is: mix the waste residue with hot water or mother liquor into 30%-40% slurry, heat it to 85°C, add liquid caustic soda (30%), react for a period of time, and add the amount of alkali to control the end of the reaction.

[Application] Trisodium phosphate has a slippery feeling when dissolved in water, can increase the wetting ability in water, has a certain emulsification effect, and is an excellent detergent for removing dirt on hard surfaces and metal surfaces

In chemical cleaning, there are two common alkaline cleaning solution formulations: one is to prepare a mixed solution of trisodium phosphate (0.

① Trisodium phosphate is a strong alkali and weak acid salt.

②The use of phosphate is conducive to the softening of hard water.

③Sodium tripolyphosphate is relatively unstable and will gradually hydrolyze into simpler phosphates such as trisodium phosphate and sodium pyrophosphate after being heated

④ Sodium pyrophosphate has obvious surface activity when used in alkaline cleaning.

⑤ In addition to the above-mentioned effects, phosphate also has significant properties of inhibiting metal corrosion

⑥ Although the price of phosphate is not very expensive, it is more expensive than other alkaline substances, and is generally not used as the main agent of alkaline cleaning agents

Related Links: Application of Hydrofluoric Acid