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Ceramic sanitaryware products are produced using inorganic and non-metallic raw materials such as clay, kaolin, quartz and feldspar at certain rates. After mixing and grounding process, the slip is obtained. The products are shaped in gypsum or synthetic resin moulds. Green bodies are fired at 1250 °C for 16–18 h, and their water absorption values are less than 0.5%. Nowadays the most important issues are raw materials and energy costs. In this study, the sintering behaviour of Na-feldspar and K-feldspar, which are widely used in ceramic sanitaryware, is analysed by reducing to different grain sizes. The grain sizes of the samples containing Na-feldspar were reduced under 63 µm. It was found that the decrease in grain size of Na-feldspar contributed to the decrease in sintering temperature. Potassium feldspar was also added instead of Na-feldspar in order to develop deformation behaviour at higher temperature. The increase in the amount of K-feldspar contributed to the decrease in deformation values. However, the flexural strength of the bodies decreased. A decrease in grain size of Na-feldspar resulted in a reduction of 10 °C at the sintering temperature. The decrease in sintering temperature will provide a cost advantage of around 3%. It was also found that technical properties such as firing shrinkage, bulk density, and flexure strength increased as the grain size of Na-feldspar decreased. [ABSTRACT FROM AUTHOR]

Soil salinity is one of the major limiting factors for poor crop yield in the world. Increasing salinity in the soil is a challenge for agriculture. In the recent past, plant growth-promoting rhizobacteria (PGPR) are being used to enhance plant growth in various conditions. However, the saline-tolerant PGPR are of great use for plant growth under saline condition. In the present study, saline-tolerant E. hormaechei(MF957335) was isolated from saline water. E. hormaechei(MF957335) was tested for its potassium and calcium solubilizing efficiency using Scanning Electron Microscopy–Energy Dispersive X-Ray (SEM–EDX). E. hormaechei(MF957335) and K-Feldspar treatments significantly increased plant growth as compared to untreated plants (negative control). E. hormaechei(MF957335) significantly increased fresh biomass, shoot and root length of tomato plants. Among all the NaCl treatments, maximum fruits (9.66) were achieved in 250 mM NaCl + E. hormaechei treatment. Similar results with increased fruit numbers were obtained in K-Feldspar-treated plants. Apart from the plant growth, fresh biomass and fruit numbers, tomatoes from K-Feldspar-treated plants were large, fleshy and deep red colored. The study could demonstrate bioavailability of potassium from K-feldspar for tomato cultivation. Control plants tomato were small, non-fleshy, yellowish red, and infected with calcium deficiency disease blossom-end rot. The present study demonstrates the role of E. hormaechei(MF957335) in plant growth, yield promotion and disease tolerance by potassium and calcium solubilization, respectively. The study showed that E. hormaechei(MF957335) could be applied to saline and non-saline soils to enhance tomato yield. [ABSTRACT FROM AUTHOR]

The development of potash materials from local K-bearing resources such as aluminosilicate minerals is desirable to overcome reliance on imported fertilizers in tropical countries. However, the nutrient release from such materials follows a time-dependent profile that is not well-understood and that is significantly different if probed at agronomic or geological timescales. This work investigates the nutrient release from a calcium–aluminum–silicate-hydrate (C–A–S–H) material obtained via hydrothermal alteration of K-feldspar ore and CaO. The C–A–S–H hydrothermal material is subjected to sequential leaching cycles with diluted HNO3 (initial pH = 5), renewing the leaching solution at every cycle. X-Ray Powder Diffraction (XRD) is used to monitor changes in the material mineralogy as the leaching progresses, showing a relative increase of calcite (up to 7 wt%) and amorphous phase (up to 23 wt%). Inductively Coupled Plasma Mass Spectrometry (ICP-MS) of the leachates is used to monitor the release of K, Ca, Si and Al, and shows that the material releases K nutrient at every leaching cycle. The pH of the leachates shows that as the content of calcite in the material increases a buffering capacity at pH ≈ 9.6 is developed by the material. The mineralogy, nutrient release, and pH results presented in this study suggest a potential application of the material as a slow release fertilizer when compared to KCl. Experimental results also imply that kinetic parameters rather than solubility are more suited to describe the fertilizer value of silicate materials. [ABSTRACT FROM AUTHOR]

This work focuses on extraction of potassium from feldspar through pyro-hydrometallurgical route. Calcium chloride was used as roasting agent for feldspar. Effect of various operating variables, viz. time, roasting temperature and CaCl2 dose on extent of roasting, were thoroughly studied. Roasting 10 g of feldspar with 17 g of CaCl2 at 900 °C for 1 h resulted in 99.9% conversion of K2O to KCl. Order of feldspar roasting was found to be around 2, and activation energy requirement was 136.6 kJ/mol. Calcium and sodium were leached along with potassium from chloride-roasted K-Feldspar with water at room temperature. To generate a pure solution of potassium from the leach liquor containing K, Ca and Na, it was selectively extracted from leach liquor by using dibenzo-18-crown-6 ether as extractant and m-cresol as diluent. Loading of potassium was carried out at an A/O ratio of 2:1, while stripping was carried out in water at O/A ratio of 2:1. 99.5% pure crystals of KCl were obtained on evaporation of the strip solution. A schematic flowsheet has been provided for the preparation of pure KCl from feldspar. [ABSTRACT FROM AUTHOR]

Reducing energy and sustainable using of natural mineral resources offer challenges in energy production and environment. In this study, an efficient methodology is proposed for using K-feldspar as fluxing agent instead of silica in phosphorus furnace. Thermodynamic analysis of the process indicated the decomposition temperature of phosphate could be reduced by as much as 103 ∘C using K-feldspar. A series of experiments were conducted at the same acidity of 0.8. At the same potassium gasification rate of 96%, the high temperature melting results showed operating temperature of the silica system was 1300 ∘C while K-feldspar system operated at 1200 ∘C When phosphorus conversion rate was close, the residual flow temperature of the K-feldspar system was 180 ∘C lower than the silica. This was due to the residual quantity and different fluxing agents. The viscosity results indicated the spread out areas were similar at 1253 ∘C for K-feldspar while at 1432 ∘C for silica. This illustrated operating temperature was reduced about 180 ∘C and potash fertilizer was produced using K-feldspar in phosphorus furnace. The significance of this result will mean improved energy and cost savings for this process. [ABSTRACT FROM AUTHOR]

A glass ceramic material was obtained from the beneficiation tailings of lead-zinc ores. The strength of the control samples was 22.26 MPa in bending and 90.22 MPa in compression. After 100 cycles of testing the samples for frost resistance, these characteristics changed to 9.61 MPa in bending and 35.30 MPa in compression. [ABSTRACT FROM AUTHOR]

In the Amba Dongar sub-volcanic complex, nephelinite plugs and dikes of phonolites were emplaced before the carbonatites. The fenitizing fluids released from carbonatite magma caused extensive fenitization in nephelinites with intensity varying from mild carbonatization (CO metasomatism accompanied by hematitization) in the distal outcrops, to a high degree of K-fenitization (feldspathization, phlogopitization) in outcrops closer to the carbonatite bodies. The intensely fenitized rocks are the xenoliths of nephelinites within the sövite. The primary texture of the nephelinites is mostly preserved, but the highly feldspathised nephelinites look more like nepheline syenite with water clear poikilitic K-feldspar in the groundmass. Invariably, nepheline is largely replaced by hydromuscovite and to lesser extent by zeolite (mainly natrolite and phillipsite). Cancrinite is also noticed in some thin sections. Pyroxene has been partially or totally replaced by phlogopite while the groundmass has been feldspathised with formation of poikilitic Kfeldspar (Or>90%). On the basis of mineralogical study, back scattered electron images and elemental mapping on microprobe, three processes of fenitization, namely, K-metasomatism (formation of hydromuscovite, phlogopite and Kfeldspar), zeolitization and CO2-metasomatism along with hematitization are identified. K-feldspar in the norms of fenitized nephelinite varies from 9% to 36%. Fenitized nephelinites show enrichment in trace and rare earth elements over the unfenitized nephelinites. [ABSTRACT FROM AUTHOR]

K-feldspar crystals >5 cm in greatest dimension are common in calc-alkaline granites and granodiorites worldwide. Such megacrysts are generally interpreted as having grown to large sizes early in a magma's crystallization history while they were largely molten, owing to field relations such as megacryst alignment and megacryst-rich clusters and to crystallographic features such as zonally arranged inclusions and sawtooth Ba zoning. These features are consistent with early growth but do not require it. In contrast, experimental petrology, mineral compositions, and natural examples of partial melting of granite demonstrate that K-feldspar is typically the last major phase to crystallize and that most K-feldspar growth occurs after the magma crosses the rheologic lock-up threshold of ~50 % crystals. The near-absence of K-feldspar phenocrysts in dacite lavas and tuffs, even in highly crystalline ones, demonstrates that natural magmas do not precipitate significant K-feldspar while they are mobile. The highly potassic compositions of megacrysts (and indeed, of K-feldspar in non-megacrystic granites as well) require exsolution of albite component down to temperatures of ~400 °C. The low Ca contents of megacrysts cannot result from exsolution of anorthite and must represent recrystallization of the crystals at low temperature. These mineralogical and experimental constraints require that K-feldspar megacrysts indicate widespread and thorough recrystallization of the host granites and granodiorites. [ABSTRACT FROM AUTHOR]

K-feldspar megacrysts are common in granitoids, but relatively rare in chemically equivalent volcanic rocks. Dacites from Taapaca volcano have euhedral sanidine megacrysts up to 5 cm long. Small crystals, where present, are rounded. Growth of the megacrysts engulfed plagioclase and amphibole crystals. Crystal size distributions (CSD) of sanidine megacrysts are hump shaped. All these data show that megacrysts developed from the host magma by coarsening: this was enabled by the cycling of magma temperature around the sanidine liquidus temperature in response to injections of more mafic magma and subsequent magmatic overturns. Plagioclase crystals enclosed in the megacrysts are small and have short, steep, straight CSDs, which contrasts with the CSDs of plagioclase in the groundmass which are shallower and extend to larger sizes. This shows that plagioclase was also coarsened approximately synchronously with sanidine, in response to the same temperature conditions. [ABSTRACT FROM AUTHOR]

In intermediate-acid magmatic rocks, alkaline magmatic rocks, gneisses and migmatitic rocks K-feldspar is a rock-forming rock in which the contents of Pb are highest, just 2 - 10 times those of the whole rock, 3 - 16 times those of mica minerals and 6 - 32 times those of quartz. The lowest contents of K-feldspar are recognized in Early Proterozoic and Achaean rocks, with Pb in the K-feldspar accounting for less than 10% of that in the whole rock; in post-Middle Proterozoic alkaline magmatic rocks, K-feldspar-rich granites and metamorphic rocks the contents of K-feldspar tend to increase, with the proportion of Pb over that in the whole rock being obviously increased. In the alkaline rocks in which K-feldspar accounts for 50% - 70% of the total in the whole rock, the contents of Pb in K-feldspar account approximately for 70% - 95% of the total lead in the whole rock. Being accessible to hydrothermal alteration in the late periods, K-feldspar was conversed to sericite, calcite, quartz, etc. In the process of such conversion the lead would be leached out and then find its way into fluid phase. This kind of transformation can provide sufficient ore-forming material for later Pb metallogenesis. [ABSTRACT FROM AUTHOR]

Many points of evidence, especially igneous microstructures and structures resulting from solid-state deformation, indicate that K-feldspar megacrysts in deformed granites of the Papoose Flat pluton are residual phenocrysts, not porphyroblasts. Evidence of an igneous origin includes features such as crystal shapes, simple twinning, zonally arranged euhedral plagioclase inclusions, oscillatory compositional zoning, and local occurrence in microgranitoid enclaves. Evidence of solid-state deformation of the megacrysts (which is consistent with their existence prior to the mylonitic deformation) includes marginal recrystallization and neocrystallization, microcline twinning, marginal replacement by myrmekite, and recrystallized/neocrystallized “tails”. Evidence of porphyroblastic growth, such as overgrown inclusion trails, is absent. This appears to be the situation in most felsic augen gneisses and mylonites. [ABSTRACT FROM AUTHOR]

Crushed rocks and mine tailings containing biotite, K-feldspar and nepheline as K-bearing minerals were applied as K fertilizers in a series of 15 grassland field trials. A treatment with KCl as K-source outyielded treatments with rock based fertilizers in the first and the second experimental year. In the third and last year of the study when no K fertilizers were supplied, previously added carbonatite and biotite concentrate supported grass growth as much as previously added KCl did. Although it is concluded that a substantial part of the K bound in biotite and/or nepheline in crushed carbonatites, biotite concentrate and epidote schists is plant available, these rock/mineral products weathered too slowly to replenish the native pool of plant available K within a three year period with five harvests. The K bound in K-feldspar seemed to be nearly unavailable for the grass plants. [ABSTRACT FROM AUTHOR]

29Si,27Al MAS NMR and IR spectra of rnonophase K-feldspars (sanidine, orthoclase and microcline) and Na-feldspars (monalbite, anorthoclase and low albite) in different structural states have been studied. The NMR and IR spectra of K-feldspars and Na-feldspars vary regularly along with their degrees of Si/Al ordering evolution. Si in orthoclase occupies T 2m, T2o and T1m, and the high-temperature Na-feldspar (monalbite and anorthoclase) coincides in29Si,27Al NMR and IR spectra. Moreover, all the high-temperature Na-feldspars and sanidine have the same27Al NMR and IR spectra. [ABSTRACT FROM AUTHOR]

Sn-polymetallic ores at Dachang, Guangxi Autonomous Region, China, are hosted in Middle-Upper Devonian reef limestones, siliceous rocks, banded and lenticular limestones, etc. Two types of orebodies can be distinguished according to their relations to the bedding: one is distributed along the bedding and the other cuts across the bedding. Sn and sulfide orebodies associated with K-feldspars are mostly characterized by laminated ore structure. Microscopic examinations of K-feldspar-bearing rocks, in conjunction with X-ray diffraction, chemical composition and cathodoluminescence data for K-feldspars, as well as their relations to mineralization, the authors consider that the K-feldspars are of authigenic origin, subordinate to the epigenetic stage of diagenesis. They resulted from the reaction of mixed, deep-seated, circulating underground hot waters rich in K, Al and Si with argillaceous carbonates during the Indo nesianorogenic movement. It is suggested that more attention should be paid to the effect of authigenic K-feldspars on Sn mineralization. In the meantime the events related to circulating underground hot waters should also be taken into account so as to provide new clues to blind ore prospecting. [ABSTRACT FROM AUTHOR]

A creative approach for the hydrothermal decomposition of K-feldspar for the extraction of potassium (K) in mixed alkaline solutions containing NaOH and CaO pretreated by microwave was studied. Under the same processing conditions, a systematic comparison of microwave pretreatment and traditional hydrothermal reaction showed that K+ dissolution efficiency was 95% when the mixture was pretreated by microwave. In the test range, the optimum conditions for dissolution of K-feldspar were found to be K-feldspar/H2O of 50 g/L, NaOH concentration of 5.625 mol/L, CaO/NaOH mass ratio of 1:3, reaction temperature of 200 °C and time of 3 h. The changes of K-feldspar before and after reactions were determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). SEM analysis indicates perfectly that microwave heating is volumetric and inside-out compared to conventional heating being outside-in. Analysis of XRD spectra results showed that the mechanism of potassium extraction was ion exchange. The anorthite or hydroxyl-cancrinite was precipitated from solution. [ABSTRACT FROM AUTHOR]