synonymFerrous ion(ferrous ion) generally refers to ferrous ion
Ferrous ion Fe2+(ferrousironOr ferrous ion, more than 60% of research articles use the former), metal cation, ion symbol Fe2+。It is generally light green with strongReducibility, can react with many oxidants, such aschlorine, oxygen, etc.Therefore, it is better to prepare and use the ferrous ion solution, and add some iron powder into it during storage(Iron ionHave strongOxidizabilityAnd can react with iron to generate ferrous ion) ferrous ion is also oxidizing, but it is relatively weak, and can react with magnesiumaluminum, zinc and other metalsDisplacement reaction。
Of substances called "sub" in chemistryValenceMust be higher than its highestChemical valenceLow (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, butFerrous hydroxide[Fe(OH)two]It is a white solid that is insoluble in water.
Production method
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1、sulphuric acidMethod: sulfuric acid andmother liquorMix, heat to 80 ℃ with steamiron filingsDissolve in the reaction solution, and make the reaction slightly acidicferrous sulfateAfter the solution is clarified and impurities are removed, it is cooled and crystallizedCentrifugal dewatering, to produce ferrous sulfate.Its Fe+HtwoSOfour→FeSOfour+Htwo↑。
2、Titanium whiteBy product method: decompose sulfuric acidilmenitemanufactureTitanium dioxideFerrous sulfate, a by-product of precipitation, freezing and separation during productionRecrystallizationRefining to produce finished ferrous sulfate.Its FeTiOtwo+2HtwoSOfour→FeSOfour+TiOSOfour+TiOSOfour+2HtwoO。
3. SlowOxidation method: Put iron in humid air, and iron will be oxidized to ferrous ion by oxygen in the air.Its Fe-2e-=Fe2+
Internal material Fe of rust balltwoOthree·HtwoO or Fe (OH)threeFresh filter membrane FetwoOthree·5HtwoO or Fe (OH)three·2HtwoO
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 hascatalytic activityHowever, 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.ThereforeCatalysisIt 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 materialAttachment。The iron active filter membrane on the surface of the filter material is continuously renewed, which is rust sandIron removal by contact oxidationNormal processnecessary condition。
It has been known that the process of iron removal by contact oxidation of iron active filter membrane is first the filter membraneIon exchange adsorptionFerrous ions in water can be expressed as follows:
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 reactedProductIt 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.
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 membraneIron removal by contact oxidationIt is a concept of autocatalytic processIron removalProcess is intercepted inFilter bedThe iron inCatalysisThe 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 depthDirectional distributionChange of.Where curve 1 is the filter layerBackwashAfter 1 hourconcentration 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.
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 becomeIron removalRate control steps.The experiment shows that the ferrous ion is transferred to the filter materialSurface diffusionIt may be the rate of iron removalControl factors。The experiment also shows that the active filter membrane on the filter materialSurface adsorptionFerrous ions in water.
according toFick's law, when ferrous ion diffuses to the surface of filter membrane,Diffusion rateIt is proportional to the concentration difference of ferrous ion (C-C ') between the water and the filter membrane surfaceBoundary layer thicknessσ is inversely proportional.If the diffusion rate is taken as the iron removal rate and C 'is considered to be small and negligible, then
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.
It can be used as pesticide in agriculture to control wheatSmut,Apples and pearsScab of fruit treesCanker disease;Food grade is used as nutritional supplement, such as iron fortifier, fruits and vegetablesChromogenic agent。
Fe2+PH of the solution (at normal temperature) from the beginning of precipitation to the completion of precipitation: 7.6~9.6.
Fe(OH)twoThe precipitation is oxidized to Fe (OH)threeHourColor changeWhite to grayish green to reddish brown.
If you want to make Fe (OH) in the laboratorytwo, you can use FeCltwoandNaOHIs the raw material.First boil FeCltwoAnd NaOH solution, and thenDropperInhale NaOH solution and stretch it into FeCltwoFe (OH) can be prepared below the liquid leveltwo。
matters needing attention
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danger
Health hazard: forrespiratory tractIrritating, caused by inhalationcoughAnd shortness of breath.Irritating to eyes, skin and mucous membrane.Weakness caused by misuseabdominal 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 ornormal salinerinse.Get medical attention.
Inhalation: quickly leave the site to a place with fresh air.Keep the respiratory tract unobstructed.asdyspnea, give oxygen.asApnea, perform artificial respiration immediately.Get medical attention.
Ingestion: Rinse with water and drink milk or egg white.Get medical attention.
Fire extinguishing method:fire fighterMust wear full body fire protectionAntivirus clothing, onUpwindFire 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.
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 towaste disposalSite disposal.
Packaging and storage
In summerquality guarantee period30 days, cheap price, good decolorization effect, flocculationAlum flowerLarge, fast settling.Outer packaging50 kg and 25 kg respectivelyWoven bagFerrous sulfate is widely used in bleaching, dyeingElectroplating wastewaterIs an efficient water purificationflocculant , especially for bleaching and dyeing wastewaterDecolorization treatment, better effect;Available asFerrous sulfate monohydrate Its raw material, ferrous sulfate monohydrate, is widely used in the feed industry;It is an efficient flocculant for electroplating wastewaterPolymeric ferric sulfateThe 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 byOperating Procedures。Recommended for operatorsSelf suction filtering dust mask, Dai ChemicalSafety goggles, wear rubber acid and alkali resistant clothes, wear rubberAcid and alkali resistant gloves。Avoid dust generation.Avoid contact with oxidants and alkalis.equipmentLeakage emergency treatmentEquipment.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 addChlorine water, the solution shows blood red, which indicates that it contains ferrous ion
Fe3++3SCN-==Fe(SCN)three(Complexation reaction, is reversible, is a characteristic reaction to test iron ion;Ferrous ion has no such characteristic)
Method 3: Addsodium hydroxideThe 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 solutionpotassium permanganateIf the color fades, there will be ferrous ions. If the color does not fade, it will completely deteriorate.
Method 5: Add to the solutionSodium acetate, because ferrous ion has no phenomenon when it encounters sodium acetate, while ferrous ion occursDouble hydrolysis, sediment is generated,RecombineMethod 3 or 4 can be used to judge.
Method 6: Add ironPotassium cyanateSolution with blue precipitation (Fethree[Fe(CN)six]two), it indicates that there is ferrous ion
withFerrous chlorideFor example, take a small amount of the solution to be tested in the test tube,Dropwise additionPotassium ferricyanide solution, with blue precipitation, indicates that it contains ferrous ion
Principle: iron ion and ferrous ion can react with some compounds to form differentcomplex compoundIron 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 FeClthreeSolution 2ml, another one containing newly prepared 0.1 mol/L FeSOfour2 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 Fethree+Can generate with SCNcoordination numberA series of red from 1 to 6Iron thiocyanateComplex ionBecause of.
2. The reaction with potassium ferrocyanide and potassium ferrocyanide is filled with 0.1 mol/l FeCl in two test tubes respectivelythreeSolution and freshly prepared 0.1 mol/l FeSOfour2ml of each solution, add a few drops of potassium ferrocyanide solution respectively, and there is blue in the ferric chloride solutionprussian blue Precipitation generation.
Do the same experiment with potassium ferricyanide instead of potassium ferrocyanide. In ferrous sulfate solution, there are dark blueTeng's blueSedimentation andpotassium sulphateBuild.On threeFerric chlorideThere is no precipitation in the solution, but the color of the solution turns brown.