Feldspar, alkaline

The actual name dry scrubbing was first publicized by Teller [U.S. Patent no. 3,721,066 (1973)]. He worked both with classical Army-type soda-lime and with his patented water-activated form of the alkaline feldspar nepheline syenite as a flow agent and feedstock sorbent for HF and SO9 in hot, sticky fumes from glass melting furnaces. He claimed capture of more than 99 percent of 180 ppm HF and SO9 for more than 20 hours in a packed bed of 200 X 325 mesh hydrated nephehne syenite at 42,000/hr. 

Gays are an essential component of soils, to which we owe our survival, and they are also the raw materials for some of mankind s most ancient and essential artefacts pottery, bricks, tiles, etc. Clays are formed by the weathering and decomposition of igneous rocks and occur typically as very fine panicles e.g. kaolinite is formed as hexagonal plates of edge. 1-3 p m by the weathering of alkaline feldspar... 

Granite A crystalline intrusive igneous rock consisting of alkaline feldspar and quartz. 

Sr 10-100 ppm 100-5000 ppm In alkaline feldspars of pegmatites. In other occurrences. Marked correlation with Na in comagmatic series (Steele and Smith, 1982). 

The unmixing products of alkaline feldspars are usually defined as perthites, which are further subdivided as follows ... 

Figure 5,62 Experimentally observed distribution of NaAlSi30g component between plagioclases and alkaline feldspars (Seek, 1971) compared with results of Wohl s and Kohler s models. Reproduced from Barron (1976), with modifications.

Table 10.2 Upper concentration limits for Henry s law behavior in silicates and oxides. Abbreviations Ab = albite Sa = sanidine PI = plagioclase Pel = alkaline feldspar Rb-fel = Rb-feldspar Ne = nepheline Mu = muscovite 01 = olivine Di = diopside Cpx = clinopyroxene Oxp = orthyporoxene Amph = amphibole Par = pargasite Gr = garnet Ilm = ilmenite ...

BOSTONITE. A rather rare rock type, dense, with an occasional feldspar phenocrysl and grayish in color, II is composed almosl wholly of alkaline feldspar, being analogous to aplites. The type locality is Salem Neck, Massachusetts, close to Boston, for which it was named. 

Figure 7. Upper Diffractogram of the sample MJ0240, representative of the unaffected Sevillian pottery. Lower Diffractogram of the sample MJ0237, representative of the affected Sevillian pottery, anl analcime cal calcite gh gehlenite hm hematite ill illite-muscovite kfs alkaline feldspar pg plagioclase px pyroxene qtz quartz...

In the intermediate layer a surplus of negative charge arises. This is compensated by cations of the O layer [2,3,4], initially Mg2+ and Fe2+. The thus formed vacancy in the O layer is filled with a Si4+ from the T layer [4] or an Al3+ from the O layer. By now the disintegration has reached an advanced stage. An example of erosion in a chemical equation is the formation of the clay mineral kaolinite from orthoclase, an alkaline feldspar. 

Alkaline feldspar - This is feldspar with chemistry ranging between the potassium and sodimn end members. 

The fine mica fraction is deslimed over 0.875—0.147-mm (80—100-mesh) Trommel screens or hydrocylcones, or is separated with hydrosi2ers. The deslimed pulp (<0.589 mm (—28 mesh)) of mica, feldspar, and quart2 is then fed to a froth flotation circuit where these materials are separated from each other either by floating in an acid circuit with rosin amine and sulfuric acid (2.5—4.0 pH), or an alkaline circuit (7.5—9.0 pH) with tall oil amine, goulac, rosin amine acetate, and caustic soda (see Eig. 2). 

Clays are composed of extremely fine particles of clay minerals which are layer-type aluminum siUcates containing stmctural hydroxyl groups. In some clays, iron or magnesium substitutes for aluminum in the lattice, and alkahes and alkaline earths may be essential constituents in others. Clays may also contain varying amounts of nonclay minerals such as quart2 [14808-60-7] calcite [13397-26-7] feldspar [68476-25-5] and pyrite [1309-36-0]. Clay particles generally give well-defined x-ray diffraction patterns from which the mineral composition can readily be deterrnined. 

Egyptian faience A non-ceramic material made from a mixture of quartz, lime, soda, alumina, and feldspar, which is fired and covered with a layer of usually blue, alkaline glaze. 

At least four different explanations have been proposed to account for parabolic kinetics. The oldest and best established is the "protective-surface-layer" hypothesis. Correns and von Englehardt (6) proposed that diffusion of dissolved products through a surface layer which thickens with time explains the observed parabolic behavior. Garrels ( 12, 1 3) proposed that this protective surface consists of hydrogen feldspar, feldspar in which hydrogen had replaced alkali and alkaline earth cations. Wollast (j>) suggested that it consists of a secondary aluminous or alumino-silicate precipitate. In either case, a protective surface layer explains parabolic kinetics as follows If the concentration of any dissolved product at the boundary between the fresh feldspar... 

One additional aspect of laboratory dissolution experiments is the question of stoichiometric vs. non-stoichiometric dissolution. Many of the studies cited above analyzed only a few of the elements released by feldspar that is, although alkalis, alkaline earths, silica, and aluminum may be released during dissolution of feldspar, few studies report analyses for all elements. Often, only silica was analyzed. Where multiple elements are analyzed, they are often released to the solution in proportions which do not correspond to the bulk stoichiometry of the feldspar ( ] ). 

The morphology of weathered feldspar surfaces, and the nature of the clay products, contradicts the protective-surface-layer hypothesis. The presence of etch pits implies a surface-controlled reaction, rather than a diffusion (transport) controlled reaction. Furthermore, the clay coating could not be "protective" in the sense of limiting diffusion. Finally, Holdren and Berner (11) demonstrated that so-called "parabolic kinetics" of feldspar dissolution were largely due to enhanced dissolution of fine particles. None of these findings, however, addressed the question of the apparent non-stoichiometric release of alkalis, alkaline earths, silica, and aluminum. This question has been approached both directly (e.g., XPS) and indirectly (e.g., material balance from solution data). 

All dykes are K-rich (up to 7.75 wt. % K2O) and mostly sub alkaline (calcic to alkali-calcic), with however a few quartz-feldspar porphyry dykes plotting In the alkalic field (Fig. 3). The Na K contents vary among dyke sets. Felsic dykes are... 

The IRAC can be intrusive subunits, emplacement these feldspar-free layered mafic (LMSC), (2) a large carbonatite lens, (3) a zoned nepheline syenite sub-complex (ZSSC), and (4) a dyke suite consisting of syenitic dykes, carbonatites, and alkaline... 

Quartz is an important network silicate (Section 12.10). A number of additional tetrahedral silicate-like materials possess some AIO4 tetrahedra substituted for the Si04 tetrahedra. Such structures offer a little larger hole in comparison to the entirely Si04 structures allowing alkali and alkaline-earth cations to be introduced. Feldspar (orthoclase) is one such mineral. The alumino-silicate networks are almost as hard as quartz. For feldspar and other tetrahedral networks the number of oxygen atoms is twice the summation of silicon and other MO4 cations. 

After the experiments, significant quantities of newly formed minerals were observed at the cold extremity of the tube, pointing to a fast material transport by diffusion from the hot to the cold end of the tube. The following spatial distribution of newly formed phases, reflecting the temperature profile, was observed in both runs (Fig. 8) quartz + K-feldspar + plagioclase + Mg-rich saponites (hot extremity) quartz + K-feldspar + plagioclase (middle of the tube) and alkaline or Ca-rich clays + quartz + plagioclase (cold extremity). The cation composition of the phyllosilicates was similar in both experiments. Some newly fonned quartz crystals... 

Zone two can be defined by the absence of montmorillonite and by the tie-line mica-opal (Figure 37). Zone one, which contains montmorillonite shows the coexistence of feldspar and montmorillonite (Figure 37a). Trona and halite found in the sediments are considered to indicate higher alkalinity and alkali content of the pore fluids that effected the crystallization of the feldspar "facies" in zone two at the lake center. Here the evaporated fluids became more concentrated. 

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