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Electrical Double Layers in Aqueous Systems
Published in James F. Pankow, Aquatic Chemistry Concepts, 2019
In many true clay minerals, an atom of lower oxidation state replaces an atom of a higher oxidation state in the crystal lattice. On average, the Si4+ in a tetrahedral sheet has its charge balanced by two O2− (as is also true for SiO2(s).) Because of the size similarity between Al3+ and Si4+, an Al3+ can replace an Si4+. The substituting Al3+ ion completely fills the lattice site of the Si4+ ion. This is “isomorphous substitution”. The lower charge of the Al3+ relative to the Si4+ causes a deficit of positive charge, that is, a negative charge on the lattice. Negative lattice charge can also result from isomorphous substitution of Mg2+, Fe2+, or Cr3+ in the octahedral sheet. Given the many different ways in which the sheets can be layered and in which isomorphous substitution can occur, clay chemistry/mineralogy is a complicated and richly diverse field.
Experimental development of clay liners for waste containment in arid and semi arid regions
Published in Journal of the Chinese Institute of Engineers, 2018
The synthetic leachate on untreated soil increased the VS which was mainly due to increase in Na and also Al, and Si elements. The increase in clay minerals has increased the plasticity of MRC; which is evident from its enhanced stickiness thus increased volumetric shrinkage by 8.58%. With constant OMC, increased plasticity has decreased the unconfined compression strength by 14.54%. According to clay chemistry sodium montmorillonite has the highest swell potential. Large sodium molecules between clay particles cause clay to swell and plates to disperse; therefore high sodium clays have low permeability. After interaction of soil with leachate, Na percentage was doubled which reduced its permeability. The increase in Na element can be noted from Figure 2(b). Also when top and bottom caps of specimen molds were detached; rotten eggs smell from specimen was sensed, which was an indicator of hydrogen sulfide (H2S) gas and presence of sulfur. This gas causes environmental pollution.
Late Quaternary history of the Gumants catchment, Papua New Guinea
Published in Australian Journal of Earth Sciences, 2023
Gardening, tephra additions and the activity of pigs are all important in mixing the garden soils. The interplay of tephra additions, alluviation/sedimentation from the southern catchments and from Ep Ridge, clay chemistry (i.e. allophane and other clays fixing organic matter), gardening and the abandonment/cessation of gardening may all be central in determining the character of the garden soils. Variations in water level in the swamp, both natural and induced by humans, in the last few thousand years as well as abandonment and the reestablishment of gardening may also have been important in developing the characteristics of the garden soils.
Effect of industrial by-products on the strength of stabilized dispersive soil
Published in International Journal of Geotechnical Engineering, 2021
SAMAPTIKA MOHANTY, Nagendra Roy, Suresh Prasad Singh, Parveen Sihag
Dispersive soil is a generally high swell-shrink problem, which means when this type of soil comes in contact with water, it gets severe erosion. The dispersive soil is stabilized either mechanically or chemically, in such condition stabilization of soil is required. Dispersive soil has been found in many parts of the world, including India, Australia, the USA, Latin America, South Africa, Greece, and Thailand. Clay in the alluvial region and clayey soil are collected from mud rocks when spread in the marine atmosphere can be dispersive. These soils are usually found in the bed of the lakes and submerge plains deposits. These soils show opposite nature in erosion in comparison to ordinary clay soils. The erosion of the dispersion of soil is based on the dissolved salts in pore water, clay chemistry, and mineralogy. The addition of flyash (class C) to the dispersive soil, for the pozzolanic reaction, the strengths of stabilized specimens increase as a function of curing (Indraratna, Nutalaya, and Kuganenthira 1991). With the addition of aluminium sulphate to the dispersive soil, the dispersivity is reduced (Ouhadi and Goodarzi. 2006). The effect of stabilization of dispersive soil with lime and flyash is studied by conducting a pinhole test, double hydrometer test, crumb test, and pinhole test. (Bhuvaneshwari et al., 2007). The use of cement and lime mix with the soil decreases the dispersivity (Umesha, Dinesh, and Sivapullaiah.,2006 2009). Sodium chloride, sodium carbonate, sodium sulphate, and sodium polyphosphate are used to reduce the dispersion of natural soil (Abbasi and Nazifi 2013). The MgCl2 solution is effective in decreasing the dispersivity of expansive and dispersive clay soils (Turkoz et al. 2014). Granulated blast furnace slag (GBFS) and basic oxygen furnace slag (BOFS) stabilized with dispersive soil has reduced percentage of dispersion. With the addition of lime and natural zeolite to the dispersive soil, there is decreasing in swelling potential and dispersivity (Savas 2015). The effect of the amount of hydrated lime reduces the dry unit weight, and the curing period in the assessment of changes in the non-dispersive state by lime treatment, as well to improve in the durability, strength and stiffness properties of the clay-lime blends (Consoli, Samaniego., and Villalba 2016). Dispersive soil treated with brown coal flyash and hydrated lime, the dispersion ratio is reduced (Premkumar et al. 2016). The addition of 1.5% lignosulfonate to the dispersive soil with the electroosmos is application, the dispersion ratio is decreased (Vakili et al. 2013).