Preparation method of zinc sulfate heptahydrate

Zinc Sulfate Heptahydrate

[Physical and chemical properties] Also known as zinc alum and halo alum, it is a colorless or white crystalline powder with a density of 1.

[Preparation method] Generally, it is prepared by acid hydrolysis

(1) Preparation of zinc sulfate heptahydrate from waste zinc-iron alloy

①Add 30% dilute sulfuric acid in an acid-resistant reactor with agitation, and then add the crushed and excessive scrap zinc-iron alloy parts to start the reaction.

②After the filtration reaction is terminated, filter while hot (in the filter) to filter out the insoluble black flocculent impurities mixed with Cu and As.

③ Purify and remove iron by yellow iron vanadium method.

4FeSO ₄ +NaCIO ₄ +4H ₂ SO ₄ →2Fe ₂ (SO ₄ ) ₄ +NaCl+4H ₂ O

④Evaporation and crystallization: Pour the final filtered pure zinc sulfate solution into the evaporator, heat and evaporate until the concentration of the solution is 49～52°Be.

(2) Extract zinc sulfate heptahydrate by using zinc ore

The main component of zinc chalcedony is ZnCO ₃ , and oxide is obtained after roasting, which is then leached with sulfuric acid.

ZnO+H2SO ₄ →ZnSO ₄ +H ₂ O

After the siderite is roasted, the ferrous iron is oxidized to high iron, and the manganese is oxidized to manganese dioxide

(3) Refining crude zinc sulfate by electrolysis

The roasted zinc concentrate or crude zinc is dissolved in sulfuric acid to obtain a crude zinc sulfate solution

[Technical index] HG/T2326-2005 industrial zinc sulfate

[Application] In the cooling water system, zinc salt is the most commonly used cathodic corrosion inhibitor, and zinc ions play a major role in corrosion inhibition

Zinc salts are generally compounded with polyphosphates, organic phosphonates, polyol phosphates, molybdates, etc.

Related links: Sodium sulfide physicochemical properties and preparation methods