Purification of specularite by centrifugation instead of flotation to produce iron oxide red pigment
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Purification of specularite by centrifugation instead of flotation to produce iron oxide red pigment Xi Zhang 1,2), Shun-wei Zhu 3), Yu-jiang Li 2), Yong-li Li 1), Qiang Guo 1), and Tao Qi 1) 1) National Engineering Laboratory of Hydrometallurgical Cleaner Production Technology, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China 2) School of Environmental Science and Engineering, Shandong University, Qingdao 266200, China 3) Zhengzhou Institute of Emerging Industrial Technology, Zhengzhou 450003, China (Received: 18 October 2019; revised: 3 February 2020; accepted: 10 February 2020)
Abstract: This study used specularite, a high-gradient magnetic separation concentrate, as a raw material in reverse flotation. An iron concentrate with a grade of 65.1wt% and a recovery rate of 75.31% were obtained. A centrifugal concentrator served as the deep purification equipment for the preparation of iron oxide red pigments, and its optimal rotating drum speed, feed concentration, and other conditions were determined. Under optimal conditions, a high-purity iron oxide concentrate with a grade of 69.38wt% and a recovery rate of 80.89% were obtained and used as a raw material for preparing iron oxide red pigment. Calcining with sulfuric acid produced iron red pigments with different hues. Simultaneously, middlings with a grade of 60.20wt% and a recovery rate of 17.51% were obtained and could be used in blast furnace ironmaking. High-value utilization of specularite beneficiation products was thus achieved. Keywords: specularite; reconcentration; centrifugal concentrator; iron oxide red pigment
1. Introduction Specularite is a sheet-like aggregate with a metallic luster on its surface. Its chemical composition is α-Fe2O3, and the theoretical grade of iron is 70wt%. At present, specularite is mainly used in blast furnace ironmaking, and the added value of its products is low. Specularite has stable physical and chemical properties and is a high-quality natural iron oxide red raw material. In terms of production, natural iron oxide red pigment has the advantages of low production cost [1], simple process requirements [2–3], and environmental friendliness [4] over synthetic iron oxide red. Deep purification is a critical step in the production of natural iron oxide red pigment. The deep desiliconization of iron oxide, which is widely recognized by the public, is a fine grinding–reverse flotation process [5–7]. Santana and Peres [8] used ether amine as a collector in a crude two-fine closedcircuit test to reduce the SiO2 content in the ore from 0.30wt% to 0.17wt%. Nevertheless, flotation has its limitations because it consumes a considerable amount of energy and reagents, and also pollutes the environment [9]. In addition, the magnetic-reverse flotation process used in the separation of specularite presents disadvantages with regard to
mineral processing indicators and its poor adaptation to changes in the nature of the ore. By contrast,
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