Abstract
The removal of iron ion from leaching solution is critical for the recovery of value metals, with the method of choice commonly being crystallization (precipitation). This paper summarized the new improvements in iron removal by precipitation methods in recent years and proposed a novel process, magnetic seeding and separation. The new process can promote iron precipitate aggregation and growth on the surface of the magnetic iron ore seeds. A core-shell structure was formed of iron precipitate and magnetic iron ore seeds, which can be magnetized and coalesced in magnetic field, accelerating the solid-liquid separation. The efficient magnetic flocculation and separation offset the poor settleability and filterability of the residues, contributing to the development of the hydrometallurgy process. Moreover, magnetic seeding and separation was also used for the removal of organic and inorganic contaminants from wastewater, significantly improving the purification efficiency. Therefore, iron ore not only played an important role in mining and steel manufacture, but also can be used to solve some problems in crossing fields.
Highlights
IntroductionIron is one of the most abundant elements in the earth’s crust. It always coexists with metals in the ore, mainly exists in the form of hematite, magnetite and muscovite on the surface of particles or in the inclusions inside crystals [1]
The iron removal method of the hydrometallurgical leachate is still dominated by the goethite process
The goethite process faces the disadvantages of high loss rate of valuable metals and difficulty in separation and filtration, which must be solved to get qualitative improvement
Summary
Iron is one of the most abundant elements in the earth’s crust. It always coexists with metals in the ore, mainly exists in the form of hematite, magnetite and muscovite on the surface of particles or in the inclusions inside crystals [1]. In order to ensure the effect and efficiency of iron removal, the goethite process must strictly control the concentration of Fe3+ below 1 g/L, and developed the two commonly used processes - VM method and EZ method [8–9, 11] The former firstly reduces all the iron ions to Fe2+, and slowly oxidizes the Fe2+ to Fe3+ under hydrolysis conditions to control the content of Fe3+ [9], and the latter slowly adds the concentrated pressure leachate containing Fe3+ in the precipitation vessel with addition rate of less than the Fe3+ hydrolysis rate, thereby forming goethite precipitation [11]. The pH in goethite process is common lower than 4.0, and calcium hydroxide or calcium carbonate is usually used as neutralizer, which will result in a large amount of calcium sulfate mixed with the goethite residue [12] These mixed residues reduce the filtration efficiency and cause the loss of valuable metals such as Zn and Ni [5, 13–14]. Magnetic seeding and separation processes have been successfully used in the removal of iron from hydrometallurgical leachate, and shown good application prospects in wastewater and soil pollution treatment
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