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    A brief overview of mineral and metallurgical processing of marine ores
    (Canadian Institute of Mining, Metallurgy and Petroleum, 2016) Ehsani, A.
    Seas and oceans constitute about 70% of the earth’s surface. They contain an enormous stock of various mineral resources such as sedimentary (marine placers), massive sulfide ore deposits, manganese nodules and cobalt-rich ferromanganese crusts. Sea and ocean floor ore deposits could well contribute to the meeting of ever-rising demand for raw materials in the metal industry. In this regard, more research and development in science and technology appear to be required to ensure maximum benefit from the mineral resources of seas and oceans. Since the 1960s, a variety of mineral and metallurgical processes have been studied and developed to deal with marine ores and to extract metals such as gold, nickel, copper, cobalt, manganese, tin, platinum group metals (PGM), zirconium, thorium, etc. In marine environments, there are many parameters which can affect the selection of the mineral and metallurgical processes. These include the extent and grade of the deposit, mineralogical and chemical properties of the deposit, and physical properties of minerals present with particular reference to particle size distribution and mineral liberation size. In this paper, we briefly review the latest trends in processing and extraction of marine mineral resources. Mineral processing technology is mostly applied for recovery of precious metals i.e. gold and PGM, in particular, from marine placers. In general, pre-treatment (sizing, classification, dewatering), gravity concentration techniques (shaking tables, spirals, jigs, etc.,), flotation, magnetic, and electrostatic separation are the options for enrichment of marine placer ore deposits. In the case of massive sulfides, manganese nodules/cobalt-rich crusts, hydrometallurgical and pyrometallurgical methods (as proven technological methods) can be exploited for extraction of metals from concentrates after physical separation or directly from marine ores. The hydrometallurgical treatments involve acid (e.g., sulfuric-hydrochloric) and alkaline (e.g., ammonia) leaching with different reducing agents and pre-treatments such as roasting. Alternatively, pyrometallurgical treatments involve mostly smelting, chlorination and segregation processes. © 2017 TAPPI Press. All rights reserved.
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    Effects of grinding time on morphology and collectorless flotation of coal particles
    (Elsevier, 2022) Guven, O.; Kaymakoglu, B.; Ehsani, A.; Hassanzadeh, A.; Sivrikaya, O.
    The impact of particle shape and surface properties has been mainly overlooked in the literature for different mineral systems. In this study, to investigate the effects of morphological variations, samples of clean coal parti-cles (-0.212 + 0.075 mm) were used and the flotation experimental in a batch condition (2 L Denver cell) were conducted in the absence of collectors by keeping the particle size constant. Binocular microscopic images were used to determine the shape factors of coal particles. A dry ball milling process was carried out as a function of grinding time (60-960 s) and representative samples were taken for determining both shape and floatability of particles. Further, particle-bubble attachment, zeta potential, roundness, surface roughness values and flotation kinetics were measured. It was indicated that by increasing milling duration from 60 s to 960 s, the round-ness and roughness increased from 0.792 to 0.809 and 23 nm to 57 nm, respectively. This led to increasing flotation rate constant from 0.4482 +/- 0.02 to 0.4856 +/-& nbsp;& nbsp;0.03 1/min. In addition, the theoretical calculations for energy barrier showed that upon increasing the roughness degree from 0 to 57 nm, the energy barrier signifi-cantly decreased from 2.79E-16 to 6.51E-17 J/m(2), which also proved our findings from a theoretical point of view. Thus, it was finally concluded that the more the roughness, the higher the flotation kinetics and the lower the energy barrier.(c) 2021 Elsevier B.V. All rights reserved.