Pyrophyllite (Al2Si4O10(OH)2) is a phyllosilicate often associated with quartz, mica, kaolinite, epidote, and rutile minerals. In its pure state, pyrophyllite exhibits unique properties such as low thermal and electrical conductivity, high refractive behavior, low expansion coefficient, chemical inertness, and high resistance to corrosion by molten metals and gases. These properties make it desirable in different industries such as refractory; ceramic, fiberglass, and cosmetic industries; as filler in the paper, plastic, paint, and pesticide industries; as soil conditioner in the fertilizer industry; and as a dusting agent in the rubber and roofing industries. Pyrophyllite can also serve as an economical alternative in many industrial applications to different minerals as kaolinite, talc, and feldspar. To increase its market value, pyrophyllite must have high alumina (Al2O3) content, remain free of any impurities, and possess as much whiteness as possible. This paper presented a review of pyrophyllite’s industrial applications, its important exploitable properties, and the specifications required for its use in industry. It also presents the most effective and economical techniques for enriching low-grade pyrophyllite ores to make them suitable for various industrial applications.
The Kingdom of Saudi Arabia covers an area of approximately 2 million km2 and is rich in natural resources that are necessary for industrial development. The estimated mineral wealth beneath the Kingdom’s soil is approximately USD 1.33 trillion, as reported by the Ministry of Industry and Mineral Resources. The Kingdom’s vision for 2030 is to develop the mining sector to become the third pillar of the domestic economy. Therefore, exploration and mining activities are expected to accelerate over the next decade, which will lead to increased waste production. New executive regulations issued in January 2021 contain several sustainable elements related to the environment, social responsibility, and occupational health and safety. Therefore, this study aims to promote an example of sustainable mining activities in the Kingdom that could be adapted to meet the regulatory requirements. Cemented paste backfill samples of varying composition were made with waste materials from a Saudi copper mine for re-injection into underground mining cavities to minimize waste exposure to the environment. The samples were tested for unconfined compressive strength (UCS) after 7, 14, 28, 56, and 90 days of curing. Results from a statistically designed experiment technique show that the samples developed sufficient strength to be used in mine backfilling applications. Strong negative relationships were detected between the UCS and the water-to-binder ratio. There is strong potential for mine backfill technology to be applied to a wide range of Saudi Arabian mines to enhance the sustainability of the mining sector.
The effectiveness of mine backfilling depends on the properties of its constituents. The high cost of cement, which is commonly used as a binder in mine backfill, has led researchers to seek alternatives to partially replace it with other binders. This study investigated the potential to use nano-calcium carbonate (NCC) and natural pozzolans (zeolite and pumice) along with Portland cement (PC) in mine backfill. Two types of experimental samples were prepared: (1) gold tailings and silica sand to investigate the effect of NCC and (2) nickel tailings to investigate the effect of natural pozzolans. The unconfined compressive strength (UCS) was measured for samples cured for up to 56 days. Moreover, selected samples were subject to mercury intrusion porosimetry to investigate microstructural properties. Results show that addition of NCC did not improve the UCS of backfill prepared with gold tailings and cured for 28 days, whereas a dosage of 1% NCC in backfill samples prepared with silica sand improved UCS by 20%, suggesting that the gold tailings negatively affected strength development. Natural pozzolans, in particular, 20% zeolite, had 24% higher UCS after 56 days of curing compared to samples prepared with PC and thus have the potential to partially replace cement in mine backfill.
Purpose: Due to the importance of pyrophyllite as an economical alternative to several minerals such as kaolin, talc, and feldspar in different industrial applications, there is an intention in Saudi Arabia to exploit pyrophyllite in the industry. Since there were no sufficient studies conducted to characterize pyrophyllite in Saudi Arabia, this paper aims to study the chemical and mineralogical characterization of Saudi pyrophyllite ore grades and propose its potential applications besides proposing beneficiation strategies for the low-grade one. Method: In this study, two different grades pyrophyllite ore samples, from a pyrophyllite deposit in western Saudi Arabia, were characterized for their potential applications. Microscopic studies, X-ray fluorescence (XRF), scanning electron microscope coupled with energy dispersive X-ray (SEM-EDX), X-ray diffraction (XRD) were used for chemical and mineralogical characterization of the studied samples. Results: Microscope and XRD results have shown that the ore samples (labeled grade A and grade B) consist mainly of pyrophyllite associated with quartz and feldspar in addition to minor amounts of muscovite, chlorite, and siderite as impurity minerals. Moreover, the results indicated that the impurities are oxide and sulfide minerals (i.e., pyrite, hematite). According to XRF analysis results, grade A contains high alumina (27.03% Al2O3) and low iron (0.4% Fe2O3) whereas; grade B contains a high iron content (2.06% Fe2O3) and lower alumina (24.05 % Al2O2). It is predicted that the grade A with high alumina content can be used directly in fillers, refractories, fiberglass, whiteware ceramics, white cement, porcelain, and cosmetic applications. As for grade B, high iron content limits its industrial applications. Therefore, it needs to be treated to remove ferrous impurities before supply to pyrophyllite market. Conclusion: Based on analytical results, grade A with high alumina content can be used directly in fillers, refractories, fiberglass, whiteware ceramics, white cement, porcelain, and cosmetic applications. Furthermore, grade B needs to upgrade due to high iron content before being used in the industry.
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