Ferrous ion

Metal cation

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Ferrous ion Fe 2+ （ferrous iron Or ferrous ion, more than 60% of research articles use the former), metal cation, ion symbol Fe 2+ 。 It is generally light green with strong Reducibility , can react with many oxidants, such as chlorine , oxygen, etc. Therefore, it is better to prepare and use the ferrous ion solution, and add some iron powder into it during storage（ Iron ion Have strong Oxidizability And can react with iron to generate ferrous ion) ferrous ion is also oxidizing, but it is relatively weak, and can react with magnesium aluminum , zinc and other metals Displacement reaction 。

Chinese name: Ferrous ion
Foreign name: Ferrous ion

Alias: Fe 2+
Color: Hydrated ferrous ion is light green
Nature: Strong reducibility

catalog

ten Ferrous ion test
eleven Inspection of iron ion and ferrous ion

Material characteristics

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Of substances called "sub" in chemistry Valence Must be higher than its highest Chemical valence Low (such as ferrous ion, iron ion; Ferrous oxide 、 ferric oxide ）, but not necessarily in the middle of the valence; Or it is lower than the most stable chemical valence (for example, the chemical valence of chlorine is - 10+1+3+5+7, with+7 being its highest chemical valence and+5 being its most stable chemical valence. Only+3 is called "inferior").

Note: Most ferrous saline solutions are light green, but Ferrous hydroxide [Fe(OH) two ]It is a white solid that is insoluble in water.

Production method

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1、 sulphuric acid Method: sulfuric acid and mother liquor Mix, heat to 80 ℃ with steam iron filings Dissolve in the reaction solution, and make the reaction slightly acidic ferrous sulfate After the solution is clarified and impurities are removed, it is cooled and crystallized Centrifugal dewatering , to produce ferrous sulfate. Its Fe+H two SO four →FeSO four +H two ↑。

2、 Titanium white By product method: decompose sulfuric acid ilmenite manufacture Titanium dioxide Ferrous sulfate, a by-product of precipitation, freezing and separation during production Recrystallization Refining to produce finished ferrous sulfate. Its FeTiO two +2H two SO four →FeSO four +TiOSO four +TiOSO four +2H two O。

3. Slow Oxidation method : Put iron in humid air, and iron will be oxidized to ferrous ion by oxygen in the air. Its Fe-2e - ＝Fe 2+

Research experiment

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for example Hydrogen chloride (HCI), water (H two O) Etc.

Sample name

chemical composition

Fresh filter membrane

Fe two O three ·5H two O or Fe (OH) three ·H two O

Internal material Fe of rust ball two O three ·H two O or Fe (OH) three Fresh filter membrane Fe two O three ·5H two O or Fe (OH) three ·2H two O

Is the test result. Rust ball with fresh filter membrane has good iron reduction effect. However, the rust ball washed off the filter membrane has poor iron removal effect and has the same characteristics as the new filter material, which indicates that only the filter membrane material with loose rust ball surface has catalytic activity However, the total dense material in the rust ball has no catalytic activity. The loose iron filter membrane with catalytic activity on the surface of filter material is called iron active filter membrane.

The experiment shows that the catalytic activity of the fresh iron activated filter membrane is the strongest. With the extension of time, the iron activated filter membrane gradually ages, and its catalytic activity gradually decreases. The experiment was carried out with mature filter media. After shutdown for several days, the iron removal efficiency of mature filter media has been greatly reduced, indicating that the iron filter membrane will gradually age with time and lose its catalytic activity. The dense material inside the rust ball is formed by the long-term accumulation of aging iron filter membrane. Therefore Catalysis It can only be realized during continuous iron removal. The iron active filter membrane on the surface of the filter material is supplemented in the process of iron removal, so that the original filter membrane is continuously covered with new filter membrane, which keeps the filter membrane fresh and has high catalytic activity. The old filter membrane gradually ages and loses catalytic activity, and becomes dense on the surface of filter material Attachment 。 The iron active filter membrane on the surface of the filter material is continuously renewed, which is rust sand Iron removal by contact oxidation Normal process necessary condition 。

It has been known that the process of iron removal by contact oxidation of iron active filter membrane is first the filter membrane Ion exchange adsorption Ferrous ions in water can be expressed as follows:

Fe( OH ) three ·2H two O+Fe 2+ =Fe(OH)2(OFe) ·2H two O + +H +

When there is dissolved oxygen in the water, the adsorbed ferrous ions are rapidly hydrolyzed and oxidized under the catalysis of the active filter membrane, so that the catalyst can be regenerated and reacted Product It is also used as a catalyst to participate in the reaction, so the contact oxidation of ferric active filter membrane is an automatic catalytic process.

Fe(OH) two (OFe) ·2H two O+1/4·O two +9/2 ·H two O= 2Fe(OH)3·2H two O+ H +

The iron sludge in the backwash water was collected and analyzed, and it was found that there was basically no ferrous compound in it. It shows that ferrous ions adsorbed by the active filter membrane can be rapidly oxidized to high iron.

conclusion

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According to iron active filter membrane Iron removal by contact oxidation It is a concept of autocatalytic process Iron removal Process is intercepted in Filter bed The iron in Catalysis The contact oxidation iron removal capacity of the filter layer shall be improved. This is indeed the case. During iron removal, the iron concentration of water along the filter layer depth Directional distribution Change of. Where curve 1 is the filter layer Backwash After 1 hour concentration distribution Curve 2 shows 36 hours after backwashing. The position of curve 2 moves up from that of curve 1, which shows that the contact oxidation iron removal capacity of the filter layer is significantly improved with the accumulation of iron in the filter layer, which confirms the conclusion that the contact oxidation iron removal of the iron active filter membrane is an automatic catalytic process.

Mature filter

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mature Filter bed Of Iron removal by contact oxidation Rate.

The ferrous ion in the water is removed in the mature filter layer through the following steps:

In the above steps, reaction rate The slowest will become Iron removal Rate control steps. The experiment shows that the ferrous ion Surface diffusion It may be the rate of iron removal Control factors 。 The experiment also shows that the active filter membrane on the filter material Surface adsorption Ferrous ions in water.

according to Fick's law , when ferrous ion diffuses to the surface of filter membrane, Diffusion rate It is proportional to the concentration difference of ferrous ion (C-C ') between the water and the filter membrane surface Boundary layer thickness σ is inversely proportional. If the diffusion rate is taken as the iron removal rate and C 'is considered to be small and negligible, then

-dc/dt=DS/D(C-C’)≈DS/σ·C　(1)

Where t -- time, t=ml/u;

L - thickness of filter layer;

M - filter layer porosity ；

U -- filtration rate;

D—— diffusion coefficient ；

S -- External surface area of filter membrane in unit volume filter layer, S=6a (1-m)/d;

D - particle size of filter material;

A -- filter material Shape factor ；

σ - thickness of boundary layer;

C '- concentration of ferrous ion on the surface of filter membrane.

Substitute the above parameters into equation (1)

-dc/dι=βC　(2)

β=6Dam(1-m)/ σdu　(3)

In the formula, β is called the Contact catalysis Activity coefficient 。

When water is in the filter layer laminar flow In case of state flow, the thickness of boundary layer can be considered as a certain value (σ=const)

Ferrous preparation

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Preparation and use of ferrous.

preparation

In the laboratory, you can use Copper sulfate solution It is obtained by reacting with iron.

1. Steel is being plated Or plus Before coating, it will be put into sulfuric acid for pickling to produce a large amount of ferrous sulfate By products.

2. With ilmenite production titania It will also produce a large amount of ferrous sulfate.

3、 sulphuric acid Ferrous can also Pyrite Or iron reacts with sulfuric acid to prepare Dilute sulfuric acid join iron filings And get).

It is made by adding dilute sulfuric acid to iron filings.

When the temperature of aqueous solution during crystallization is<56.6 "C, it is heptahydrate; when the temperature is 56.6~64.4 ℃, it is tetrahydrate; when the temperature is>64.4 ℃, it is monohydrate.

Application

Used to make ferric salt 、 Iron oxide pigment 、 Mordant 、 Water purifying agent 、 preservative 、 disinfectant Etc;

Pharmaceutical works Antianemic drug , Local Astringent And blood tonic, which can be used for fibroid Chronic blood loss caused by;

Analytical reagent And Ferrite Raw materials;

As feed additive Iron fortifier;

It can be used as pesticide in agriculture to control wheat Smut ， Apples and pears Scab of fruit trees Canker disease ； Food grade is used as nutritional supplement, such as iron fortifier, fruits and vegetables Chromogenic agent 。

It can also be used as fertilizer to remove trunk Of Lichen and Lichens 。 Is to make magnetism ferric oxide , iron oxide red and Iron blue Inorganic pigment 、 Iron catalyst And poly ferric sulfate Raw materials.

In addition, it is also used as chromatographic reagent.

Iron content of water

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Iron concentration in groundwater.

Iron concentration of groundwater is 14mg/l; dissolved oxygen Concentration 7 ～ 8mg/l; Filtration rate 10m/h。

Ferrous experiment

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Fe 2+ PH of the solution (at normal temperature) from the beginning of precipitation to the completion of precipitation: 7.6~9.6.

Fe(OH) two The precipitation is oxidized to Fe (OH) three Hour Color change White to grayish green to reddish brown.

If you want to make Fe (OH) in the laboratory two , you can use FeCl two and NaOH Is the raw material. First boil FeCl two And NaOH solution, and then Dropper Inhale NaOH solution and stretch it into FeCl two Fe (OH) can be prepared below the liquid level two 。

matters needing attention

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danger

Health hazard: for respiratory tract Irritating, caused by inhalation cough And shortness of breath. Irritating to eyes, skin and mucous membrane. Weakness caused by misuse abdominal pain , nausea, hematochezia, lung and liver damage, shock, coma, etc., which can lead to death in serious cases.

Environmental hazards : It is harmful to the environment and may cause pollution to the water body.

First aid measures

Skin contact: Take off contaminated clothes and wash with plenty of flowing water.

Eye contact: lift the eyelid, use flowing water or normal saline rinse. Get medical attention.

Inhalation: quickly leave the site to a place with fresh air. Keep the respiratory tract unobstructed. as dyspnea , give oxygen. as Apnea , perform artificial respiration immediately. Get medical attention.

Ingestion: Rinse with water and drink milk or egg white. Get medical attention.

Fire fighting measures

Harmful Combustion products ： Sulfur oxide 。

Fire extinguishing method: fire fighter Must wear full body fire protection Antivirus clothing , on Upwind Fire fighting. When putting out a fire, try to move the container from the fire site to an open place. Then select appropriate extinguishing agent to extinguish the fire according to the cause of fire.

Emergency Management

Emergency Management : Isolate the leakage contaminated area and restrict access. It is recommended that emergency handling personnel wear Anti-dust masks , wear general work coverall 。 No direct contact Leakage.

Small amount of leakage: avoid raising dust, carefully sweep it up and collect it in a dry, clean and covered container.

Large amount of leakage: collect, recycle or transport to waste disposal Site disposal.

Packaging and storage

In summer quality guarantee period 30 days, cheap price, good decolorization effect, flocculation Alum flower Large, fast settling. Outer packaging 50 kg and 25 kg respectively Woven bag Ferrous sulfate is widely used in bleaching, dyeing Electroplating wastewater Is an efficient water purification flocculant , especially for bleaching and dyeing wastewater Decolorization treatment , better effect; Available as Ferrous sulfate monohydrate Its raw material, ferrous sulfate monohydrate, is widely used in the feed industry; It is an efficient flocculant for electroplating wastewater Polymeric ferric sulfate The most important raw materials of. Operation precautions: closed operation, Local exhaust 。 Prevent dust from releasing into the workshop air. Operators must be specially trained and strictly abide by Operating Procedures 。 Recommended for operators Self suction filtering dust mask , Dai Chemical Safety goggles , wear rubber acid and alkali resistant clothes, wear rubber Acid and alkali resistant gloves 。 Avoid dust generation. Avoid contact with oxidants and alkalis. equipment Leakage emergency treatment Equipment. Empty containers may leave harmful substances. Precautions for storage: store in a cool and ventilated warehouse. Keep away from kindling and heat sources. Protect from direct sunlight. The package must be sealed to prevent moisture. It should be stored separately from oxidants, alkalis, etc., and should not be mixed. The storage area shall be equipped with appropriate materials to contain leakage.

Ferrous ion test

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Method 1: Observation method 。 The aqueous solution of ferrous ion is light green

Method 2: Add potassium thiocyanate solution without obvious phenomenon, and then add Chlorine water , the solution shows blood red, which indicates that it contains ferrous ion

reaction Ionic equation ：

2Fe 2+ +Cl two ==2Fe 3+ +2Cl -

Fe 3+ +3SCN - ==Fe(SCN) three （ Complexation reaction , is reversible, is a characteristic reaction to test iron ion; Ferrous ion has no such characteristic)

Method 3: Add sodium hydroxide The solution generates white precipitate, then the white precipitate quickly turns to grayish green, and finally turns to reddish brown. This proves that there is ferrous ion.

Method 4: Add acid to the solution potassium permanganate If the color fades, there will be ferrous ions. If the color does not fade, it will completely deteriorate.

Method 5: Add to the solution Sodium acetate , because ferrous ion has no phenomenon when it encounters sodium acetate, while ferrous ion occurs Double hydrolysis , sediment is generated, Recombine Method 3 or 4 can be used to judge.

Method 6: Add iron Potassium cyanate Solution with blue precipitation (Fe three [Fe(CN) six ] two ）, it indicates that there is ferrous ion

with Ferrous chloride For example, take a small amount of the solution to be tested in the test tube, Dropwise addition Potassium ferricyanide solution, with blue precipitation, indicates that it contains ferrous ion

reaction Chemical equation

3FeCl two +2K three [Fe(CN) six ] == Fe three [Fe(CN) six ] two ↓+6KCl

Inspection of iron ion and ferrous ion

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Purpose: cognition test Iron ion And ferrous ion.

Supplies: test tubes test tube rack 、 Test tube clamp 、 Measuring cylinder , dropper.

Ferric chloride 、 ferrous sulfate 、 Potassium thiocyanate 、 Potassium ferrocyanide 、 Potassium ferricyanide 。

Principle: iron ion and ferrous ion can react with some compounds to form different complex compound Iron ion and ferrous ion can be identified from the color of these complexes.

Operation:

1. Reaction with potassium thiocyanate solution Take two test tubes, one containing 0.1 mol/l FeCl three Solution 2ml, another one containing newly prepared 0.1 mol/L FeSO four 2 ml of solution, 1~2 drops of potassium thiocyanate solution are added respectively, the former is red, and the latter is not red. This is because Fe three +Can generate with SCN coordination number A series of red from 1 to 6 Iron thiocyanate Complex ion Because of.

2. The reaction with potassium ferrocyanide and potassium ferrocyanide is filled with 0.1 mol/l FeCl in two test tubes respectively three Solution and freshly prepared 0.1 mol/l FeSO four 2ml of each solution, add a few drops of potassium ferrocyanide solution respectively, and there is blue in the ferric chloride solution prussian blue Precipitation generation.

Do the same experiment with potassium ferricyanide instead of potassium ferrocyanide. In ferrous sulfate solution, there are dark blue Teng's blue Sedimentation and potassium sulphate Build. On three Ferric chloride There is no precipitation in the solution, but the color of the solution turns brown.

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