Serpentine is a versatile mineral family rich in Mg silicate with several polymorphic phases, mainly antigorite and lizardite, all of them with similar chemical composition (Mg 3 Si 2 O 5 (OH) 4 ). Their structures are generally composed of octahedral layers rich in Mg[MgO 2 (OH) 4 ] 6− , attached to a tetrahedral silicate [Si 2 O 5 ] 2− sheet. The unique physicochemical properties of serpentinites and the existence of large reserves in Brazil create new important opportunities for research and technological applications. In this work, serpentinites structures and properties are reviewed, as well as its occurrence and literature describing its applications in construction/ceramics, agriculture, as a silica source, in steel production, as an additive/filler in polymers, in the production of composites, adsorption of cations and organics contaminants, CO 2 capture and catalysis. The presence of harmful chrysotile associated with serpentinites, some of its properties and uses are also described.

Currently, approximately 1.4 billion tons per year of iron ore tailing wastes (IOT) are generated, mainly in Australia, Brazil, and China. This work describes the characterization and application of two typical IOT, i.e., fine and coarse wastes. The physicochemical characterization of these IOT by different techniques such as XRF (X-ray fluorescence), XRD (X-ray diffraction), Mössbauer spectroscopy, and granulometry, indicates for the fine tailing a composition of Fe2O3/FeOOH (10-55%), SiO2 (18-65%) and Al2O3 (up to 15%) with particles of 6-40 μm, whereas the coarse tailing presents 40-150 μm particles with the composition of 8-48% Fe2O3/FeOOH, 30-90% SiO2 and Al2O3 (up to 20%). The main IOT applications discussed in this review are related to civil construction (aggregates for concrete, mortar, Portland cement additives), ceramic industry, geopolymer, synthesis of new materials such as zeolites, mesoporous silica, carbon nanotubes, adsorbents, catalysts for different reactions, in batteries and in fuel cells. It was also carried out an analysis of patents related to IOT applications and the main technological and market barriers that hinder the industrial and commercial uses of these wastes.

The iron mine tailings accumulation in dams is an environmental and economic problem. The composite based on high-density polyethylene/iron mine tailing production for the application of wood plastic and some items of domestic plastic industry can be a good alternative to reduce the rejects in the environment. This work presents the influence of the processing methodology in the mechanical, thermal and morphological properties of composites based on the high-density polyethylene/iron mine tailing. Four methodology processing by continuous and/or batch mixing were available. The iron mine tailing particles in the polymer matrix promoted an increase in mechanical strength and thermal stability. Besides, the particles acted as flame retardant. The iron mine tailing materials produced using batch mixing showed more significant modifications in the properties due to the better dispersion of the filler as shown by scanning electron microscopy.

Este trabalho caracterizou uma amostra de serpentinito in natura e após calcinação em forno mufla a 1200ºC. Foram utilizadas as técnicas analíticas: análise química, difratometria de raios-X (DRX), microestruturas por MEV e EDS. A DRX confirmou os minerais filossilicatos, lizardita e talco, como os principais constituintes desta amostra, e a magnetita em menor quantidade. Foi feita termogravimetria (TG e DTG) até 1450ºC e os resultados mostraram uma perda de massa total de 12,15%, além de dois picos: da lizardita a 645ºC e do talco a 729ºC. Para analisar as fases ricas em ferro, utilizou-se a espectroscopia Mössbauer, com espectros registrados à temperatura ambiente. Além disso, a amostra calcinada foi também analisada na temperatura muito baixa de 25K. Estes resultados completaram a composição de fases, com a diminuição da quantidade de magnetita e a presença significativa de magnesioferrita. As fases dominantes foram forsterita e enstatita, ambas contendo ferro na composição. Pela análise microestrutural, observou-se a mudança morfológica das partículas, com diminuição expressiva das fibras finas, para formas mais arredondadas de bastonetes indicando o início do processo de sinterização.

In this work, a potassium magnesium silicate mineral based on phase K 2 MgSiO 4 was prepared from serpentinite rock and studied as a potential K and Mg slow-release fertilizer. The material was prepared by impregnation of serpentinite/KOH and calcination at 700 °C to produce K 2 MgSiO 4 phase, olivine and forsterite. The release patterns of K and Mg in the stirred-flow trial and leaching through the soil columns showed that K 2 MgSiO 4-based materials released K on lower rates than KCl and MgSO 4 .7H 2 O, however, there was no evidence of Mg release. The extraction with 1 mol L-1 NH 4 OAc showed a considerable content of Mg and K for K 2 MgSiO 4-based materials, due to exchange of NH 4 + and Mg 2+. X-ray diffraction (XRD) analysis of materials impregnated with K and calcined showed peaks relative to K 2 MgSiO 4. After leaching, the peaks intensity diminished, supporting that part of K leached. Therefore, the samples showed great potential as slow-release K-fertilizers when compared with KCl source.

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Pelletizing iron ore fines is an agglomeration process that through a thermal treatment converts the ultra-fines fraction thereof into small balls ranging in size from 8mm (0.31 in.) to 18mm (0.71 in.)

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