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Petroleum Geological Survey
Published in Muhammad Abdul Quddus, Petroleum Science and Technology, 2021
Calcareous (containing calcium) and siliceous (containing silicon) materials of biological origin composed of calcite (CaCO3) and chert (SiO2) minerals contribute to the formation of organic sedimentary rock. Calcium carbonate and silica are the constituents of calcareous and siliceous shelled marine living organisms (zooplankton). They build their shells through the assimilation of dissolved calcium and silicon compounds. The remaining materials of the dead zooplankton continue to be accumulated in the aquatic bottom forming layers of sedimentary rock With the passage of geological time, overburden pressure increases, the accumulated material is converted to a calcite and chert sedimentary rock. Additionally chemical alterations of calcite rock take place in the presence of subsurface saturated magnesium solution. A double salt mineral, known as dolomite (CaCO3MgCO3), is formed.
Deterioration of Brickwork Retaining Walls as a Result of Thaumasite Formation
Published in Christer Sjöström, Durability of Building Materials and Components 7, 2018
Salts were collected from either on or below the surface of the garage retaining walls and three different compounds were detected using XRD analysis. These were (i) sodium sulphate (thenardite), (ii) a double salt containing potassium and sodium sulphate (aphthitalite) and (iii) a double salt containing potassium and calcium sulphate (syngenite). Whereas the precipitation of sodium or calcium salts as crypto-efflorescence is relatively harmless, the occurrence of crypto-efflorescent salts containing potassium can seriously damage the front face of brickwork [1] [2].
Mechanisms of Concrete Deterioration
Published in Satish Chandra, Yoshihiko Ohama, in Concrete, 2020
Hydrochloric acid attacks hardened concrete through a dissolution process, soluble salts are formed, and leaching takes place. During this process the pH of the acid solution is increased; consequently hydrolysis is resumed, and eventually Si, Al, and Fe gels are produced. Chandra78 has described HC1 attack as a reaction that occurs in layers forming distinct zones (Figure 4.9). In the first zone, dissolution takes place, soluble salts are formed and leach out. It is a rather porous zone having no strength. A mixture of hydroxides formed during hydrolysis are found next to the porous zone, which encapsules the undamaged concrete. This layer is very hard and protects the concrete from further deterioration. It is dark brown in color due to the precipitation of Mn and Fe compounds, which give a very dark matrix around the mineral grains. The presence of a mineral called iddingsite, a Fe-Si complex, is also suggested. The tendency to rim formation around the aggregates, which can be aluminum silicates, has also been noticed; it creates intense swelling. In the outer zone no iron precipitate could be detected, due to the formation of soluble iron chloride, giving yellow color. However rim formation around the aggregates was visible here also. Besides this, there were indications for formation of expansive double salt with C3A (Friedel’s salt). The hardened concrete thus loses its strength owing to the dissolution of hardened cement paste components and to the destruction of the hydrosilicate matrix. These were evident from the X-ray diffraction analyses on concrete done by Mullick et al.79
A Simple Process for the Recovery of Rare Earth Elements and Iron from Sulfuric Acid Leaching Solution of NdFeB Magnets by Double Salt Precipitation
Published in Mineral Processing and Extractive Metallurgy Review, 2023
Thi Thu Huong Nguyen, Man Seung Lee
Since dehydration of the chemical species is necessary to form double salt, temperature would affect the precipitation percentage of Nd(III) double salt. Therefore, reaction temperature was varied from 40°C to 120°C at the molar ratio of Na(I) to Nd(III) of 100. The concentrations of Nd(III) and H2SO4 were fixed at 1.2 g/L and 0.05 M, respectively. The experiments were done at a stirring speed of 400rpm for 60 min. As expected, the precipitation percentage of Nd(III) double salt increased from 76% to 99% as temperature increased from 40°C to 120°C (see Figure 7). However, the reaction rate is too fast at higher temperatures, leading to the inclusions of some impurities which would reduce the purity of the double salts. For this reason, 80°C was selected as the best temperature for the precipitation of double salt.
Production and characterisation of sodium and potassium carbonate salts from carbonation alkaline aluminate liquor
Published in Mineral Processing and Extractive Metallurgy, 2021
Shima Barakan, Mehdi Noroozi Ayaluey, Somayeh Shayanfar, Valeh Aghazadeh
Figure 4 shows the experimental results for the variation of the grade (purity of the recovered salt) and recovery (the percentage of the intended salt in the initial alkaline carbonate solution that is recovered) of sodium carbonate as a function of the solution density. The results indicate that an increase in solution density causes a decrease in the sodium carbonate grade. This is due to the presence of the double salt Na2CO3.K2CO3. Moreover, the sodium carbonate recovery increased with increasing solution density. The potassium carbonate grade and recovery (Figure 5) also increased with increasing solution density. The grade and recovery curves for sodium carbonate indicate that a solution density of 1.50 g/cm3 could be suitable for sodium carbonate production as at this condition the grade and recovery of potassium carbonate are at an acceptable level.
Structural changes on hydrous and anhydrous potash alum caused by mechanical milling
Published in Particulate Science and Technology, 2019
Hiroaki Kishimura, Hitoshi Matsumoto
Potassium aluminum sulfate dodecahydrate (KAl(SO4)2 ･ 12H2O), commonly known as potash alum, is a so-called double salt. Potash alum is α -alum with a cubic structure and a space group of Pa3(Th6) (Nyburg et al. 2000; Barashkhov, Komyak, and Shashkov 2004; Sakuntala et al. 2000). It has been used as a food additive and in various cosmetic formulations, such as antiperspirants, as well as in cleansing and skin care products.