Sulfate, also called sulfate ion, is a kind ofInorganic ionThe chemical formula is SO ₄ ² ⁻.In SO ₄ ² ⁻ ion, S atom adoptsSp3 hybrid, ions presentRegular tetrahedronStructure, sulfur atoms are located at the center of the tetrahedron, and four oxygen atoms are located at the four vertices of the tetrahedron.The length of S-O bond is 149pm, which has a great degree of double bond property.The bonds between the four oxygen atoms and the sulfur atoms are exactly the same.[1]It exists in aqueous sulfuric acid solution, solid and aqueous solutions of sulfate, bisulfate, etc.
Chinese name
Sulfate radical
Foreign name
Sulfate
Interpretation
Negative ions from secondary ionization of sulfuric acid
[Ionic structure] Sulfate is a tetrahedral structure formed by covalent bonding of one sulfur atom and four oxygen atomsHybrid orbitThe sulfur atom is located at the center of the tetrahedron, while the four oxygen atoms are located at its four vertices. The bond angle of a group of S-O-S bonds is 109 ° 28 ', and the bond length of S-O bonds is 1.49 pm.Since sulfate can form a stable structure only after getting two electrons, it is negatively charged and easy to interact with metal ions orAmmonium radicalThey combine to form ionic bonds and stabilize.
The structure of sulfate ion is different.according toHigher Education PressInorganic Chemistry (Fourth Edition), Volume II, p503-505“SO ₄⁻⁻₄⁻⁻⁻₄⁻⁻₄⁻⁻₄⁻⁻⁻⁻⁻⁻⁻₄8324.The bonds between the four oxygen atoms and the sulfur atoms are exactly the same.”[1]
Sulfate will decompose intosulfur dioxideAnd oxygen.Therefore, the total sulfur content of coal must be measured before combustion to reduce the emission of harmful gases.
commonlysulfateAre easily soluble in water.Slightly soluble silver sulfate,alkaline-earth metal(except for Be and Mg) and lead are slightly soluble in sulfate.The crystals of soluble sulfate precipitated from the solution often contain crystal water, such as CuSO ₄ · 5H ₂ O, FeSO ₄ · 7H ₂ O, etc.Except alkali metals and alkaline earth metals, other sulfates have hydrolysis in varying degrees.
Generation process
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1. Sulfur dissolved in waterAcid radical ionIs due to sulfuric acid or solublesulfateSoluble in water.Sulfuric acid isStrong electrolyte, soluble in water will quickly occurionization, producing two hydrogen ions and one sulfate ion (according to the textbook description in the middle school, it can be considered as such, but in fact, its second ionization is about 10%).
2、SulfiteRoot ions are oxidized orSulfur trioxideSoluble in water will also produce sulfate radical.
3. Sulfate radical will also be generated from the oxidative decomposition of sulfur-containing amino acids, andCysteineMetabolism is the main source of sulfate in human body.[2]
test
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There are many methods to detect sulfate content at home and abroad, mainly including gravimetric methodTitrimetry、Spectrophotometry, ion chromatography (IC method), turbidimeter method, atomic absorption spectrometry (AAS), ICP-AES method, etc.Among them,Gravimetric methodIC method and turbidimeter method are three recommended methods for detecting sulfate content in oilfield water;Titration and spectrophotometry are widely used in oil fields;Spectroscopy is a new detection method.
The combination of sulfate radical and metal barium ion will produce white precipitate of barium sulfate, but many insoluble barium salts are also white, but they are mostly soluble in acid, while barium sulfate is insoluble in acid.Therefore, hydrochloric acid is usually used to test sulfate ionenvironmental acidification , ExcludeCarbonateAnd then add soluble barium salts such asBarium chlorideTo determine whether the liquid contains sulfate ion.At the same time, it should be noted that hydrochloric acid must be added first, followed by barium chloride, otherwise it is vulnerable toSilver ionInterference, resulting in white sediment, affecting the inspection.Therefore:
(1) Add hydrochloric acid, and then filter out the precipitate;
Detection of sulfate ion
(2) Add barium chloride and observe whether there is white precipitate.
The best barium salt to be added during inspection is barium chloride. Barium nitrate is not good, because hydrogen ion andNitrateWhen ions meet, they will have strong oxidation, which will makeSulfiteIt is oxidized to sulfate, so it is impossible to check whether there is sulfate in the original solution.However, dilute nitric acid should be added to the white precipitate generated. If the white precipitate is insoluble, it is more likely that sulfate ion is contained.
Therefore, acid environment can be used to eliminate carbonate interference.[3]
application area
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Sulfate is very common, and the ion appearing in its solid salt often carries anionic crystal water, because the water molecule is connected with the oxygen atom above through hydrogen bond.
(1) Agricultural use
Potassium sulfate is a common potash fertilizer,ammonium sulphateIt is a common ammonium nitrogen fertilizer, which should not be applied together with alkaline properties, otherwise ammonia will be released and fertilizer efficiency will be reduced.copper sulphateThe solution is blue and can be used to prepare pesticidesBordeaux liquidSulfate radical.
(2) Medical use
Barium sulfatebarium mealIn medicine, it can be used for X-ray examination of digestive system;Barium sulfate is also a good protective coating.Calcium sulfate dihydrate Commonly known as gypsum, it can be used in medicine for fixation, home decoration, and concrete manufacturing to control the setting time.
(3) Life use
ferrous sulfateThe solution is light green and is often used as an iron supplement.Anhydrous copper sulfateIt can be used to absorb water or detect the presence of water.Copper sulfate pentahydrateIt is also called bile alum or blue alum, a blue solid, which can be decomposed into anhydrous copper sulfate and crystal water.Potassium aluminum sulfate dodecahydrate Commonly known as alum, it is often used for water purification in daily life.[4]
harm
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Sulfate often exists in water, and its main source issulfate, mostly withcalcium sulfate, magnesium sulfate;Dissolution of gypsum and other sulfate deposits;Seawater intrusion, sulfite andThiosulfuric acidThe oxidation of salt in the air, as well as domestic sewage, fertilizer, sulfur-containing geothermal water, mine wastewater, tanning, and industrial wastewater using sulfate or sulfuric acid in paper manufacturing can increase the sulfate content in the water.
(1) Harm to human body
The main physiological reactions after a large amount of sulfate intake arediarrhea, dehydration and gastrointestinal disorders.People often use water containing more than 600 mg/L magnesium sulfate as a drainage agent.When calcium sulfate andmagnesium sulphateWhen the mass concentration of water reaches 1000 mg/L and 850 mg/L respectively, half of the people think that the taste of water is disgusting and unacceptable.
(2) Hazards to the environment
There are many metal ions in the environment that can combine with sulfate to form stable sulfate. The sulfur dioxide gas formed by sulfate in the atmosphere hascorrosionIt is destructive, endangers the health of animals and plants, and can play a catalytic role, aggravatingsulphuric acidFog toxicity, as the precipitation reaches the ground, it will destroy the soil structure, reduce the soil fertility, and cause corrosion to the water delivery system.
If the sulfate radical content in the water exceeds a certain value, the concrete will suffer from crystalline corrosion, that is, sulfate radical andcalcium hydroxideReact to generate dihydrate gypsum crystal, which then reacts with calcium aluminate hydrate to generate hydrationCalcium sulphoaluminateThis is a composite sulfate of aluminum and calcium, which is customarily calledBacillus cement。Due to the combination of a lot of crystal water with Bacillus cement, the volume of Bacillus cement is much larger than that before the combination, which is more than twice of the original volume. Therefore, great internal stress is generated in the concrete, causing damage to the concrete structure.Accurately determine the content of sulfate radical in underground water, so as to take corresponding measures to avoid or reduce the corrosion of sulfate radical on concrete.[4]
