Components, rocks, soil processes

In general, soil is an unconsolidated combination of inorganic and organic materials. The inorganic components of soil are principally the products of rocks and minerals that have been gradually broken down by weather, chemical action, and other natural processes. Soil particles, also known as soil separates, are divided into three main size groups sand, silt, and clay minerals [14]. 

The main reactor (treatment cell or module) is the critical component of each process. Pretreatment is sometimes necessary to allow the material to fit in the treatment cell. For example, large rocks may be separated from soils, soils may be dried of excess water, and other substrates may be shredded. The preprocessing of soils usually involves sieving the soil matrix to remove rocks, large stones, and debris. Some soils and sludges may also require drying prior to treatment with solvated electrons. 

Soil is a key component of the rock cycle because weathering and soil formation processes transform rock into more readily erodible material. Rates of soil formation may even limit the overall erosion rate of a landscape. Erosion processes are also a key linkage in the rock cycle... 

Infiltrating water, passing the soil zone, becomes loaded with C02 formed in biogenic processes. The water turns into a weak acid that dissolves soil components and rocks. The nature of these dissolution processes varies with soil and rock types, climate, and drainage conditions. Dissolution ceases when ionic saturation is reached, but exchange reactions may continue (section 6.8). 

As mentioned earlier, the composition of natural groundwaters depends on the composition of the geological formations where they originate from they contain dissolved rock and soil components that were soluble under the conditions (such as temperature and pressure) of their formation. Their dissolution is governed by the law of thermodynamics that is, dissolution occurs when the solution is undersaturated with respect to components such as rocks and soils. Provided that the solid components are present in sufficient quantity and there is no kinetic barrier, this process may lead to a thermodynamic equilibrium. The reversed process of dissolution is precipitation, that is, the formation of a solid phase from the dissolved components of a supersaturated solution. The composition of the... 

On the surfaces of geological formations, different precipitation processes can be observed. The first one occurs when the concentration of some components reaches the value of the solubility product, the solution becomes oversaturated, and a new solid phase is precipitated (Section 1.2.3). The quantity of the precipitate depends only on the concentration of the solution. The precipitation takes place in a solution without the necessary presence of a solid surface. When, however, a solid phase, rocks, or soil is originally present, the precipitate is formed on it, and thus the total composition of the solid phase changes. When the precipitation forms colloidal particles, especially in diluted solutions, they can be adsorbed on the solid, if it is present. This process is governed by the so-called theory of colloid adsorption (Derjaguin and Landau 1941 Verwey and G. Overbeek 1948). 

As a result of the interfacial processes on rocks and soils, the structure and chemical bonds of the sorbed compounds can be changed. For this reason, different chemical reactions can be initiated in which the components of rocks or soils act as catalysts. The most important mineral catalysts are zeolites and clay minerals. Naturally, the different oxides also have catalytic effects, and nowadays some of them are being artificially produced for catalytic purposes such as framework silicates (zeolites), the most effective and selective catalysts in organic syntheses. The catalytic applications of zeolites are too wide to summarize in this book, so we deal with the catalytic effects of clay minerals. 

Specific adsorption on well defined materials has been the subject of many reviews [8-13]. Specific adsorption plays a key role in transport of nutrients and contaminants in the natural environment, and many studies with natural, complex, and ill defined materials have been carried out. Specific adsorption of ions by soils and other materials was reviewed by Barrow [14,15]. The components of complex mineral assemblies can differ in specific surface area and in affinity to certain solutes by many orders of magnitude. For example, in soils and rocks, (hydr)oxides of Fe(IH) and Mn(IV) are the main scavengers of metal cations and certain anions, even when their concentration expressed as mass fraction is very low. Traces of Ti02 present as impurities are responsible for the enhanced uptake of U by some natural kaolinites. In general, complex materials whose chemical composition seems very similar can substantially differ in their sorption properties due to different nature and concentration of impurities , which are dispersed in a relatively inert matrix, and which play a crucial role in the sorption process. In this respect the significance of parameters characterizing overall sorption properties of complex materials is limited. On the other hand the assessment of the contributions of particular components of a complex material to the overall sorption properties would be very tedious. 

The importance of this mineral is perhaps best demonstrated by the diversity of its sources. Assuming that nearly all of the P present is in the form of apatite, igneous rocks contain between 0.02 and 1.2% apatite. Apatite is also produced by organisms (including man) as structural body parts such as teeth, bones, and scales. After an organism dies, these components tend to accumulate in sediments and soils. In some locations, these constituents are reworked and concentrated by physical processes to form economically important deposits. By far the largest accumulations of P on the Earth s... 

Solid residues with final storage quality should have properties very similar to the Earths crust (natural sediments, rocks, ores, soil). This can be achieved in several ways, for example by assortment or thermal, chemical and biological treatment. In most cases, this standard is not attained by simple incineration of municipal solid waste - that is, by only the reduction of organic fractions. There is, in particular, the problem of easily soluble minerals such as sodium chloride. Future efforts should be aimed at optimizing the incineration process in a sense that critical components are concentrated in the filter ash and in the washing sludge, whereas the quality of the bottom ash is improved in such a way that deposition is facilitated and even reuse of this material is possible due to either the low concentrations or chemically inert bonding forms of metals. 

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