Clay chemistry

Clay chemistry is an applied subdiscipline of chemistry which studies the chemical structures, properties and reactions of or involving clays and clay minerals. It is a multidisciplinary field, involving concepts and knowledge from inorganic and structural chemistry, physical chemistry, materials chemistry, analytical chemistry, organic chemistry, mineralogy, geology and others.

The study of the chemistry (and physics) of clays and clay minerals is of great academic and industrial relevance as they are among the most widely used industrial minerals, being employed as raw materials (ceramics, pottery, etc.), adsorbents, catalysts, additives, mineral charges, medicines, building materials and others.

The unique properties of clay minerals including: nanometric scale layered construction, presence of fixed and interchangeable charges, possibility of adsorbing and hosting (intercalating) molecules, ability of forming stable colloidal dispersions, possibility of tailored surface and interlayer chemical modification and others, make the study of clay chemistry a very important and extremely varied field of research.

Many distinct fields and knowledge areas are impacted by the phisico-chemical behavior of clay minerals, from environmental sciences to chemical process engineering, from pottery to nuclear waste management.

Their cation exchange capacity (CEC) is of great importance in the balance of the most common cations in soil (Na+, K+, NH4+, Ca2+, Mg2+) and pH control, with direct impact on the soil fertility. It also plays an important role in the fate of most Ca2+ arriving from land (river water) into the seas. The ability to change and control the CEC of clay minerals offers a valuable tool in the development of selective adsorbants with applications as varied as chemical sensors or pollution cleaning substances for contaminated water, for example.

The understanding of the reactions of clay minerals with water (intercalation, adsorption, colloidal dispersion, etc.) are indispensable for the ceramic industry (plasticity and flow control of ceramic raw mixtures, for example). Those interactions also influence a great number of mechanical properties of soils, being carefully studied by building and construction engineering specialists.

The interactions of clay minerals with organic substances in the soil also plays a vital role in the fixation of nutrients and fertility, as well as in the fixation or leaching of pesticides and other contaminants. Some clay minerals (Kaolinite) are used as carrier material for fungicides and insecticides.

The weathering of many rock types produce clay minerals as one of its last products. The understanding of these geochemical processes is also important for the understanding of geological evolution of landscapes and macroscopic properties of rocks and sediments. Presence of clay minerals in Mars, detected by the Mars Reconnaissance Orbiter in 2009 was another strong evidence of the existence of water on the planet in previous geological eras.

The possibility to disperse nanometric scaled clay mineral particles into a matrix of polymer, with the formation of an inorganic-organic nanocomposite has prompted a large resurgence in the study of these minerals from the late 1990s.

In addition, study of clay chemistry is also of great relevance to the chemical industry, as many clay minerals are used as catalysts, catalyst precursors or catalyst substrates in a number of chemical processes, like automotive catalysts and oil cracking catalysts.[1][2][3][4][5][6]

See also


  1. ^ "What is clay". Science Learning Hub. University of Waikato. Retrieved 10 January 2016.
  2. ^ Grim, Ralph. "Clay mineral". Encyclopædia Britannica. Retrieved 10 January 2016.
  3. ^ "Why study clays?". Geo Drilling Fluids. Retrieved 10 January 2016.
  4. ^ "University College London Geology on Campus: Clays". Earth Sciences department. University College London. Retrieved 10 January 2016.
  5. ^ Faiza Bergaya, Gergard Lagaly (editors): Handbook of Clay Science. Elsevier, Amsterdam, 2013 (2nd Ed.).
  6. ^ Karl Jasmund, Gerhard Lagaly (editors): Tonminerale und Tone. Struktur, Eigenschaften, Anwendungen und Einsatz in Industrie und Umwelt. Steinkopf Verlag, Darmstadt, 1993.
Alexander Boden

Alexander Boden (28 May 1913 – 18 December 1993) AO Hon DSc FAA, was a: Philanthropist, industrialist (manufacturing chemist), publisher (including education author and researcher), founder of the Boden Chair of Human Nutrition at the University of Sydney, a Fellow Australian Academy of Science 1982, a founder of Bioclone Australia, Hardman Chemicals and Science Press and was awarded Leighton Medal of Royal Australian Chemical Institute in 1986. He was educated at the University of Sydney (BSc 1933, Hon DSc 1984) and received an Order of Australia (AO) and he was also the author of A Handbook of Chemistry, initially published by the Shakespeare Head Press and later by his own Science Press. After he graduated, he joined a research laboratory, which he soon took over, and renamed it Hardman Australia. Hardman Australia was turned into a manufacturing company producing in particular DDT. In 1981 he formed Bioclone Australia, which exports diagnostic products. Alex was elected to the Australian Academy of Science on the nomination of Professor John Swan, upon nomination Professor Swan said:

"Alex Boden was a man of remarkable talents, concealed by a modest, even humble, exterior. I never saw him angry. He was greatly admired as a man who had achieved much in life but whose ambition was to contribute to family, social and community welfare, to give rather than take, to be supportive of others, and above all to foster the advancement of science."


Clay is a finely-grained natural rock or soil material that combines one or more clay minerals with possible traces of quartz (SiO2), metal oxides (Al2O3 , MgO etc.) and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure. Clays are plastic due to particle size and geometry as well as water content, and become hard, brittle and non–plastic upon drying or firing. Depending on the soil's content in which it is found, clay can appear in various colours from white to dull grey or brown to deep orange-red.

Although many naturally occurring deposits include both silts and clay, clays are distinguished from other fine-grained soils by differences in size and mineralogy. Silts, which are fine-grained soils that do not include clay minerals, tend to have larger particle sizes than clays. There is, however, some overlap in particle size and other physical properties. The distinction between silt and clay varies by discipline. Geologists and soil scientists usually consider the separation to occur at a particle size of 2 µm (clays being finer than silts), sedimentologists often use 4–5 μm, and colloid chemists use 1 μm. Geotechnical engineers distinguish between silts and clays based on the plasticity properties of the soil, as measured by the soils' Atterberg limits. ISO 14688 grades clay particles as being smaller than 2 μm and silt particles as being larger.

Mixtures of sand, silt and less than 40% clay are called loam. Loam makes good soil and is used as a building material.

Clay minerals

Clay minerals are hydrous aluminium phyllosilicates, sometimes with variable amounts of iron, magnesium, alkali metals, alkaline earths, and other cations found on or near some planetary surfaces.

Clay minerals form in the presence of water and are important to life, and many theories of abiogenesis involve them. They are important constituents of soils, and have been useful to humans since ancient times in agriculture and manufacturing.

Gerhard Lagaly

Gerhard Lagaly (born 14 October 1938, in Ludwigshafen am Rhein) is a German chemist and retired university professor.

Quantum chemistry

Quantum chemistry is a branch of chemistry whose primary focus is the application of quantum mechanics in physical models and experiments of chemical systems. It is also called molecular quantum mechanics.

Trithionic acid

Trithionic acid is an polythionic acid consisting of three sulfur atoms. It can be viewed as two bisulfite radicals bridged by a sulfur atom.

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