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Food grade and medicine grade ferrous sulfate monohydrate powder in wet production Processes
Stability :Pale,blue-green crystals or granules that are efflorescent in dry air.In moist air,it oxidizes readily to form a brown-yellow,basic ferric sulfate. It’s soluble in water, insoluble in ethanol.
| NO. | Item | Specification |
| 1 | Appearance | Gray-white Powder |
| 2 | Main content | 91.3% min |
| 3 | Fe2+ | 30% min |
| 4 | Fe3+ | 0.2% max |
| 5 | Water insoluble | 0.5% max |
| 6 | Water | 1% max |
| 7 | Pb | 15 mg/kg max |
| 8 | As | 2 mg/kg max |
| 9 | Cd | 3 mg/kg max |
| 10 | Hg | 0.1 mg/kg max |
| 11 | Size(80mesh) | 95% min |
Ferrous sulfate can be classified into the following types according to different classification criteria:
1, Classification based on moisture content
Ferrous sulfate heptahydrate (FeSO ₄· 7H ₂ O): the most common form, appearing as light green crystals and containing 7 crystalline water molecules.
Ferrous sulfate monohydrate (FeSO ₄· H ₂ O): containing a crystalline water molecule, usually in the form of a white powder.
Ferrous sulfate pentahydrate (FeSO ₄· 5H ₂ O): contains five crystalline water molecules, rarely 12.
Drying ferrous sulfate: After drying treatment, it does not contain crystal water and usually appears as a white powder.
2, Classified by purpose
Industrial grade ferrous sulfate: used for industrial wastewater treatment, including electroplating wastewater treatment, printing and dyeing wastewater treatment, etc. It can also be used to manufacture iron salts, inks, mordants, bleaching agents, wood preservatives, etc.
Food grade ferrous sulfate: used in the food processing industry, usually ferrous sulfate heptahydrate, mainly used as a nutritional supplement and fruit and vegetable coloring agent.
Agricultural grade ferrous sulfate: used for soil improvement and plant nutrition supplementation, and can also be used as a pesticide to prevent and control wheat smut, apple and pear scab, and fruit tree rot.
Feed grade ferrous sulfate: As a feed supplement, it provides livestock with nutritional iron, prevents livestock anemia diseases, and enhances livestock resistance.
Pharmaceutical grade ferrous sulfate: mainly manifested in iron supplementation and treatment of iron deficiency anemia, but attention should be paid to possible side effects such as upper abdominal discomfort.
Ferrous sulfate is mainly manufactured through two processes: dry and wet methods.
Dry manufacturing process:
The dry production of ferrous sulfate mainly involves converting heptahydrate ferrous sulfate into monohydrate ferrous sulfate through a drying process. This method has a simple process, stable performance, and no secondary pollution. During the drying process, it is necessary to isolate oxygen to ensure the stability of the product. The dried ferrous sulfate monohydrate may need further processing, such as crushing, before it can be bagged. The equipment currently available on the market for preparing ferrous sulfate monohydrate using the drying method includes high-temperature rotary kiln dryers and drum dryers.
Wet manufacturing process:
The process of wet production of ferrous sulfate is relatively complex. Firstly, dissolve ferrous sulfate heptahydrate in water, heat to a certain temperature, and filter to remove impurities. Then, the solution is sent into a reaction kettle and a certain amount of ferrous sulfide (FeS) and iron powder are added to reduce trivalent iron to divalent iron. Next, a flocculant is added for precipitation, and the supernatant is crystallized in a crystallization tank to obtain pure ferrous sulfate heptahydrate. Finally, after centrifugal dehydration and specialized drying machine drying, it becomes ferrous sulfate monohydrate. Wet production of ferrous sulfate monohydrate has high main element content, good solubility, pure color, no clumping, good flowability, and is free from crushing and sieving
