Hydrolysis chemical weathering

As the rock cycle continues, the calcium silicate minerals are eventually uplifted onto land where they imdergo chemical weathering. This reaction involves acid hydrolysis driven by carbonic acid. The latter is derived from the dissolution of the magmatic CO2 in rainwater ... 

Many technical-chemical processes take maximum benefit of similarities with ongoing processes in Nature, with increased purity or reaction speed as the most important differences. The production of carbonates is a typical example of this, and the process of C02 mineralization for carbon capture and storage (CCS) (see Section 14.4) is in fact the accelerated version of what is known as the natural weathering of minerals. This is a combination of the interacting processes of mechanical and chemical weathering, and relevant to the current discussions are the chemical weathering processes of dissolution and hydrolysis that involve C02 [6, 7]. A dissolution equilibrium reaction that proceeds in Nature with dissolved C02 in water and calcite gives a bicarbonate solution ... 

The four basic processes involved in chemical weathering are (i) formation of carbonic acid from water and carbon dioxide, (ii) ionization, (iii) hydrolysis and (iv) oxidation. 

The chemical weathering of silicates and carbonates occurs through hydrolysis... 

Acid Hydrolysis. The water that enters soil as rain or snow is in equilibrium with CO2 in the atmosphere, which dissolves to form carbonic acid. Unpolluted rainwater has a pH of approximately 5.7, whereas water in soil pores may be exposed to air containing a higher partial pressure of CO2 than the free atmosphere, and hence soil water may be more acidic (see Section 5.4). It is the attack on soil minerals by this weak carbonic acid that is the major chemical weathering process in most soils. For example, acid hydrolysis of calcium carbonate yields calcium and bicarbonate ions ... 

Continental water contains dissolved species that render it acidic. The acidity comes from a variety of sources from the dissociation of atmospheric C02 in rainwater—and particularly from dissociation of soil-zone C02 (Section 4.4.2)— to form H2C(and natural and anthropogenic sulphur dioxide (S02) to form H2S03 and H2S04 (see Boxes 3.7 3.8). Reaction between a mineral and acidic weathering agents is usually called acid hydrolysis. The weathering of CaCO, demonstrates the chemical principle involved ... 

It is primarily formed by weathering or low-temperature hydrothermal alteration of feldspars, muscovite and other Al-rich silicates of acidie igneous rooks (granite, rhyolite, quartz diorite ete.). Hydrolysis is the chemical weathering reaction that brings about this transformation. 

Chemical weathering in a natural process that occurs under the prevailing environmental conditions, resulting in the transfer of matter from unstable minerals to more stable minerals and soluble species. Chemical weathering reactions include dissolution, precipitation, adsorption, and desorption of elements adsorbed on the mineral surfaces, ion exchange, oxidation, reduction and hydrolysis reactions. 

As in dissolution, a chemical and structural change can occur from hydrolysis as the ions replaced by or OH may be of a different size so that the crystal structure is stressed and weakened. An example of this is the weathering of feldspar or goethite by H ... 

All the tannins readily react with proteins, forming insoluble, stable compounds when they react with collagen, the main constituent of animal skin, they form leather, a material that is resistant to hydrolysis, oxidation, and biological attack and therefore stable to weathering and resistant to decomposition. Since tannins from different plant sources have different chemical compositions, each tannin used for tanning skin produces a leather having slightly different properties and color. Tannins that have... 

Weathering, oxidation, hydrolysis and other forms of chemical attack are complex mechanisms, which depend on environmental conditions such as temperature and humidity as well as on the intensity of radiation, the availability of oxygen or chemical concentration. In recent years these mechanisms have been studied and better understood, the principal success of which has been the development of stabiliser systems which greatly prolong the lifetime of plastics and which have extended their use to a much wider range of applications. 

The geological environments which form clay minerals can be basically divided into five types weathering, sedimentation, burial, diagenetic and hydrothermal alteration. The weathering environment frequently presents a chemical system where T,P are constant and many chemical elements are mobile, usually they enter solution from the rocks present at the earth s surface through the process of hydrolysis. The major problems are (a) Determination of rates of reaction among the minerals present,... 

As a chemical phenomenon, weathering can be viewed as the result of the tendency of the rock-water-mineral system to attain equilibrium. This occurs through the usual chemical mechanisms of dissolution and precipitation, acid-base reactions, complexation, hydrolysis, and oxidation-reduction. 

Persistence is the net result of many interacting factors, but chemical properties of the pesticide can play a dominant role. Volatility, solubility, stability to ultraviolet irradiation, tendency to adsorb onto or dissolve into tissue surfaces, ease of hydrolysis, sensitivity to humidity, potentiality to polymerize with or without ultraviolet irradiation, possible isomerization or other molecular rearrangement are all important chemical properties which play a significant role in persistence. Weather conditions such as wind, rain, amount and intensity of light, air temperature, and humidity play important roles. Rainfall is usually con-... 

Weathering degradation—sun, water, heat, wind Chemical reactions—oxidation, hydrolysis Mechanical—erosion... 

The effect of temperature on weathering is the easiest climate parameter to predict on a fundamental basis. The rates of most chemical reactions, including silicate hydrolysis, increase exponentially with temperature according to the Arrhenius expression. This relationship can be represented as the ratio of reaction rates R/Rq at different temperatures T and Tq (K) (Brady and Carroll, 1994) ... 

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