Isotope chemistry is a branch of chemistry that studies the distribution of isotopes in nature, isotope analysis, isotope separation, isotope effect and isotope application.With the development of nuclear science and technology, especially the development of nuclear weapons and nuclear power plants, the development of isotope chemistry has been further promoted.Isotope chemistry is a branch of chemistry that studies the distribution of isotopes in nature, isotope analysis, isotope separation, isotope effect and isotope application.
At the end of the 19th century, due toElectronics、X-rayandradioactivityThe discovery that human understanding can go deep into the atomic interior.Through the study of radioactivity, not only poloniumradium、Actiniumetc.radioactive elementMore than 30 new radioactive "elements" have been separated from these radioactive elementsperiodic tableThere was no vacancy in the table that could accommodate them, and some new elements with different radioactivity were identical in chemical properties and could not be separated from each other, which caused doubts at that time: was the periodic table applicable to radioactive elements?Through further study of these facts, in 1913, F. Sody and K. Fayans found the displacement law of radioactive elements at the same time, and put forward the concept of isotope, thus solving the position problem of many new elements on the periodic table.
Stable isotope geochemistry
1913 JJ. Thomson and F. W. Aston discovered two isotopes of neon -- neon 20 and neon 22 -- when they studied neon with magnetic analyzers.This is the first timestable isotope 。Made in Aston in 1919Mass spectrometerLater, he found 202 isotopes in 71 elements and measured theabundance。In 1920, G · C · de Hervey and LK. Tsechmester studiedIsotope exchange reaction。In 1931, H. C. Yuri and others found thatDeuterium；Used by G · N · Lewis, etc. in 1933Electrolytic methodPureheavy water；In 1934, Norway used its cheap hydropower to build the first heavy water plant.In 1942, the United States builtElectromagnetic separatorAnd uranium 235 was separated;In 1943, the United States established three moreUranium hexafluorideThe gas diffusion plant produces uranium 235;1944Oak Ridge National LaboratoryFirst produced kg of uranium 235, and manufactured the firstAtomic bomb。
Heavy water is not only an important raw material for reactor construction, but also a thermonuclear fuel andThermonuclear weaponRaw materials.the Second World WarLater, some countries competed to study new methods for heavy water production, including hydrogen sulfide dual temperature exchange method, liquid hydrogen distillation method, etc., which achieved industrial production.
Since the 1950s, in order to find better isotope separation methods, new scientific and technological achievements have been continuously applied to isotope separation technology.For example, breakthroughs have been made in the research of chromatography in the 1960s and laser isotope separation in the 1970s.By the mid-1980s, isotopes produced by isotope separation in the world mainly included:deuterium、tritium、helium3、lithium6、boron10、carbon13、nitrogen15、oxygen18 and uranium 235, etc.Among them, the annual output of heavy water is in thousands of tons.For example, Canada, the world's largest heavy water producer, used the dual temperature exchange method to produce heavy water, with an annual production capacity of 4000 tons in 1982.The annual output of boron 10 in the world is 100 kg.With the development of nuclear science and technology, especially the development of nuclear weapons and nuclear power plants, the development of isotope chemistry has been further promoted.
distribution
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The study of isotope distribution law has the following four aspects: ① isotope stability law, study the stability range and stability law of more than 300 nuclides on the earth (see stable isotope); ②Isotope abundanceTo study the general law of isotope abundance of various elements in earth materials; ③The fluctuations of isotope distribution on the earth, in nature,elementWhetherfreeStatus orcompoundIts isotope composition is basically constant, and its fluctuation law is one of the research topics of isotope chemistry; ④The origin and evolution of elements must be studied in order to understand the distribution of various isotopes in the universe.
separate
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According to the separation principle, it can be divided into five categories: ① separation according to the mass difference of molecules or ions, includingElectromagnetic method、Centrifugal separation②The separation is carried out according to the different movement speeds of molecules or ions, includingPore film diffusion、Mass diffusion, thermal diffusionNozzle diffusion、molecular distillation、electrophoresis③Separation is carried out according to thermodynamic isotope effect, including distillationChemical exchange, gas chromatographyIon exchange、absorb, solvent extractionFractional crystallization、Superfluidity④according todynamicsIsotope effect separation, including electrolytic method, isotope chemical exchange method, photochemical methodLaser separationMethod, etc. ⑤according tobiologyIsotope effect.(See isotope separation, uranium isotope separation)
Analytical method
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Isotope Chronology and Geochemistry of the Chinese Academy of Sciences
The methods used for isotope analysis are: ① Mass spectrometry, the most important isotope analysis method, has high precision and can analyze many kinds of isotopes. ②spectrumThe precision for deuterium analysis is 0.0002%, which is comparable to that of mass spectrometry;It is the most convenient method to analyze nitrogen 15, and there are special spectrometers;For the analysis of uranium 235 and 238, largeGrating spectrograph。③Gas chromatography, used to analyze protium and deuterium, which is fast and sensitive, and can measure deuterium content in all concentration ranges. ④Nuclear magnetic resonance spectrumThe method can be used to measure trace protium in concentrated heavy water with a precision of ± 0.01%, and can also be used to analyze carbon 13, nitrogen 15 and other isotopes. ⑤neutron activation analysis, which can be used to determine boron 10, lithium 6, uranium 235 and other isotopes. ⑥The isotope analysis of water occupies a unique position in the isotope analysis, which is not only for the need of controlling the heavy water production process, but also to solve the problem ofIsotope geochemistryAnd other problems in the research work of using deuterium and oxygen 18 as tracers.The most effective method in water isotope analysis is density method, which not only has simple instruments and equipment, but also has high measurement accuracy. In additionInfrared spectrometry。
effect
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It can be divided into four research aspects: ① Spectral isotope effect, due to the different mass of isotope nucleienergy levelChanges, resulting in spectral line displacement.This effect is not only used to analyze isotopes, but also to study molecular structure. ②Thermodynamic isotope effectThe greater the mass difference of isotopes, the greater the difference in their physical and chemical properties, which is the theoretical basis for light isotope separation. ③Dynamic isotope effect, isotope substitution changes the energy state of reactants, which may causeChemical reaction rateDifferences.This effect can be used to separate isotopes, study chemical reaction mechanism and solution theory. ④Biological isotope effectAmong the biological isotope effects, deuterium is the most significant, and the heavy isotopes of important life elements such as carbon 13, nitrogen 15 and oxygen 18 have not been observed to have significant biological isotope effects.(See isotope effect).
research contents
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isotopeChemistryThe main contents of the study include isotope distribution, isotope analysis, isotope separation, and isotope effect.
Isotope chemistry is a branch of chemistry that studies the distribution of isotopes in nature, isotope analysis, isotope separation, isotope effect and isotope application.Isotope geochemistry is a discipline that studies the isotopic content and changes in various rocks, minerals, sediments, atmosphere and water bodies in the crust or on the surface. According to the types of isotopes, it mainly includesstable isotope (such as carbon, hydrogen, oxygen, nitrogen, sulfur, etc.) andradio isotope。Because of its high geological stability, isotopes have been widely used in the determination of geological age, the tracing of ore-forming materials and the source of ore-forming materials.China Isotope Geochemistry Database, Guangzhou, Chinese Academy of SciencesGeochemistryKey Laboratory of Isotope GeochemistryOrganic geochemistryThe main data sources are carbon, hydrogen, oxygen isotopes and lead, rubidium, strontium, potassium and argon isotopes of various rocks, minerals, ores, inclusions, water bodies, soils, sediments and atmospheric samples accumulated by the State Key Laboratory, Petrology Laboratory, Petrochemistry Analysis Laboratory and Deposit Laboratory, and the research literature at home and abroad is collected.The database can be used for fuzzy query of these data.It can be widely used in geological age determination, mineral resource assessment, sedimentology, oil and gas, geochemistry, environmental protection and research and other fields.
RadiochemistryIt is a branch of chemistry that studies radioactive materials and chemical problems related to nuclear transformation.Radiochemistry and nuclear physics are correspondingly related and intertwined, becoming two brother disciplines of nuclear science and technology.Major radiochemistry researchRadionuclideThe preparation, separation, purification and identification of radionuclides, their chemical state at very low concentrations, the nature and behavior of nuclear transformation products, and the application of radionuclides in various disciplines.Since the 1960s, radiochemistry has mainly focused on the development, production and application of nuclear energy, as well as the accompanying environmental issues, and carried out basic, developmental and applied research.
