sulfate

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Sulfate, which is composed of Sulfate radical Ions (SO four 2- ）Compounds with other metal ions are electrolyte And most of them are soluble in water. Sulfate minerals are formed by the combination of metal cations (including ammonium) and sulfate salt Class. Since sulfur is a variable valence element, it can be different in nature Valence state Different minerals are formed. When it has the highest valence S 6+ And four O's 2- Combined into SO four 2- And then forms sulfate with metal element cation. In sulfate minerals, there are more than 20 kinds of metal cations combined with sulfate. That is to say, the salt containing sulfate is sulfate.

Chinese name: sulfate
Foreign name: sulphate/sulfate(ion)
Chinese name Pinyin: liú su ā n yán

Type: chemical compound ， electrolyte
Content: Ca 2+ 、Mg 2+ 、K + 、Na + 、Ba 2+
Category: Calcium sulfate, barium sulfate, ferrous sulfate, etc

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Sulfate radical

The most important one is Ca 2+ 、Mg 2+ 、K + 、Na + 、Ba 2+ 、Sr 2+ 、Pb 2+ 、Fe 3+ 、Al 3+ 、Cu 2+ 。 There are more than 170 known sulfate minerals. Although they only account for 0.1% of the total weight of the crust, gypsum, anhydrite Barite , mirabilite, etc. can be enriched into deposits of industrial significance. Sulfate minerals are mostly complex salts, so crystal structure The ones with low degree of symmetry mainly belong to monoclinic system and Orthorhombic system 。 And because most sulfate minerals contain water, their most outstanding physical properties are low hardness, generally between 2-3.5. In addition, the color is generally colorless and white, proportion It is generally not big, between 2-4. The formation of sulfate minerals requires the conditions of high oxygen concentration and low temperature, so the surface part is the most suitable place for the formation of sulfate minerals. In this class of minerals, exogenic causes are far more important than endogenic causes. Among them, sulfate minerals formed by the oxidation of primary metal sulfides account for almost half of the minerals in this category. But in the sea basin Chemical deposition The sulfate minerals of K, Na, Ca, Mg, Ba and Al are mainly hydrous sulfate. As for endogenous Hydrothermal fluid The origin of sulfate minerals is mainly anhydrous sulfate such as barium, calcium, strontium, aluminum, etc., which can be found in the middle and low temperature hydrothermal veins or as the product of low-temperature hydrothermal wall rock alteration.

origin

Volcano eruption Will emit sulfur, and then sulfur will be generated by combustion sulfur dioxide , sulfur dioxide meets steam Forming sulfite, which is exposed to oxygen Oxidation to sulfuric acid, sulfuric acid and metallic oxide React to generate sulfate.^[1]

Several important sulfates

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calcium sulfate

Calcium sulfate in nature exists in the form of gypsum ore. Contains two Crystal water Calcium sulfate (CaSO four ·2H two O) It is called gypsum (also called gypsum). If the gypsum is heated to 150 ℃, it will lose most of the crystal water and become mature gypsum (2CaSO four ·H two O）。 After being mixed with water to form a paste, the plaster will solidify quickly and turn into hard gypsum. Because of this nature of plaster, people often use it to make various models and medical plaster bandages. In cement production, gypsum can be used to adjust the setting time of cement. Gypsum can be used to produce sulfuric acid where there are abundant gypsum resources.

barium sulfate

The natural barium sulfate, called barite, is an important raw material for preparing other barium salts. Barium sulfate is not easily penetrated by X-rays, and can be used as an oral medicine for gastrointestinal examination in medical treatment, commonly known as "barium meal". Barium sulfate can also be used as white pigment, and as raw material and filler for high-grade paint, ink, paper making, plastic, rubber.

ferrous sulfate

ferrous sulfate The crystal hydrate is commonly known as alum (FeSO four ·7H two O）。 Ferrous sulfate can be used for production control in medical treatment iron-deficiency anemia In industry, ferrous sulfate is also used to produce iron series water purifying agent and pigment red iron oxide (mainly composed of Fe two O three ）Raw materials.

copper sulphate

Copper sulfate, commonly known as gallus, molecular formula CuSO four ·5H two O。 The molecular weight is 249.68. The water content is 36%. It is formed after anhydrous copper sulfate absorbs water. Cholalum is a chemical raw material for pigments, batteries, pesticides, wood preservation, etc. Copper sulfate pentahydrate It is stable under normal temperature and pressure, does not deliquescence, will gradually weathering in dry air, and will lose its dimer when heated to 45 ℃ Crystal water At 110 ℃, tetramolecular crystalline water is lost, called Copper sulfate monohydrate 。 At 200 ℃, all crystal water is lost to form anhydrous substance. Anhydrous substance It is also easy to absorb water and change into copper sulfate pentahydrate. Anhydrous copper sulfate (white or off white powder) reacts after absorbing water to produce cupric sulfate pentahydrate (blue), which is often used to test whether some liquid organic substances contain trace water. Pay attention to the distinction between the two. Anhydrous copper sulfate can be decomposed into black when heated to 650 ℃ Cupric oxide , sulfur dioxide and oxygen (or three Sulfur oxide ）。

Aluminium potassium sulfate

alum

Aluminum potassium sulfate, commonly known as alum. Molecular formula KAl (SO four ) two ·12H two O. Colorless crystal or powder. Odorless, slightly sweet, astringent and astringent. The crystal water is lost by weathering in dry air, and it dissolves and drips in humid air. Easily soluble in glycerin, soluble in water, and the aqueous solution is acidic, hydrolysis Later Aluminium hydroxide Colloidal sediment. Insoluble in alcohol and acetone 。 The melting point is 92.5 ℃. When the sulfuric acid is dried at 60~65 ℃, 9 molecules of water are lost, and at 200 ℃, 12 molecules of crystal water are lost completely, which can be decomposed at higher temperature Sulfur trioxide 。 Alum has a strong adsorption capacity, which can absorb suspended impurities in water and form precipitation to make water clear. Therefore, alum is a better Water purifying agent 。 Alum can be made from alunite through calcination, extraction and crystallization.

sodium sulphate

Sodium sulfate (Na two SO four ）， inorganic compound , also known as mirabilite, white, odorless, bitter crystal or powder, hygroscopic. The shape is colorless, transparent, large crystal or small granular crystal. Mainly used for manufacturing water glass , glass Enamel , pulp, refrigeration mixture Detergent , desiccant, dye diluent, analytical chemical reagent, pharmaceuticals, etc.

aluminum sulfate

White lustrous crystals, granules or powders. It tastes sweet. Stable in air. Some crystallization water will be lost at 86.5 ℃, and all crystallization water will be lost at 250 ℃. When heated, it expands violently and becomes spongy. It decomposes into sulfur trioxide and aluminum oxide when burned to red heat. Weathering occurs when the relative humidity is about 25% lower. It is easily soluble in water, almost insoluble in ethanol, and the solution is acidic. Insoluble alkali salt precipitates after long boiling. The relative density is 1.62. Aluminum sulfate is a widely used industrial reagent, which is often confused with alum (i.e. aluminum potassium sulfate dodecahydrate). Aluminum sulfate is usually used as a flocculant in drinking water purification and sewage treatment equipment, as well as in paper industry.

Application scope of aluminum sulfate:

1. As a coagulant for sewage treatment, it has good decolorization ability, and also has the functions of removing heavy metal ions, degreasing, phosphorus removal, sterilization, etc., especially for the decolorization of printing and dyeing wastewater, COD removal, ferrite coprecipitation of electroplating wastewater, etc.

2. As a precipitator, it can generate sediment with sulfide, phosphate, etc. to remove sulfide, phosphate, etc.

3. Aluminum sulfate is easily soluble in water, and its aqueous solution is slightly acidic. It is widely used for the purification treatment of drinking water and industrial water. It is suitable for the treatment of wastewater with low alkalinity; As a precipitator, it can remove sulfur ions, phosphate ions, etc.

It is used as a precipitator for rosin size, wax emulsion and other sizing materials in the paper industry, as a flocculant in water treatment, and also as a Foam extinguisher It is used as an internal retention agent for producing alum and aluminum white, as well as raw materials for petroleum decolorization, deodorant and some medicines. It can also produce artificial gemstones and high-grade ammonium alum. Products with arsenic content no more than 5mg/kg can be used for Water-treatmemt Flocculants 。^[2]

harm

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Environmental hazard

There are many metal ions in the environment, which can combine with sulfate to form stable sulfate. Sulfate formed in the atmosphere aerosol It is corrosive to materials, endangers the health of animals and plants, and can Catalysis , aggravated Sulfuric acid fog Toxicity; After reaching the ground with precipitation soil structure , reduce soil fertility, and have adverse effects on the water system.

Harm to people

The concentration of sulfate in natural water varies greatly, from several mg/L to thousands of mg/L (in seawater).

Sulfate often exists in drinking water, and its main source is the sulfate of formation minerals, mostly in the form of calcium sulfate and magnesium sulfate; Dissolution of gypsum and other sulfate deposits; Seawater intrusion ， Sulfite and Thiosulfuric acid Salt is oxidized in fully aerated surface water, as well as domestic sewage, fertilizer, sulfur-containing geothermal water Mine wastewater , tanning, paper manufacturing industrial wastewater using sulfate or sulfuric acid can increase the sulfate content in drinking water.

Diarrhoea, dehydration and gastrointestinal disorders are the main physiological reactions after a large amount of sulfate intake. People often magnesium sulphate Water containing more than 600mg/L is used as cathartic. When calcium sulfate and magnesium sulfate in water mass concentration When it reaches 1000mg/L and 850mg/L respectively, 50% of the respondents think the taste of water is disgusting and unacceptable.^[3]

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