Study of coal cleaning rejects by FIB and sample preparation for HR-TEM: Mineral surface chemistry and nanoparticle-aggregation control for health studies

Abstract

Nano-minerals and amorphous nanoparticles play a vital role in the contexts of human health and environmental sustainability. For instance, aerosols generated by the process of coal beneficiation adversely affect human health as well as the environment. These are called Coal Cleaning Rejects (CCRs). They mainly contain clay minerals, nano-quartz, different particles of Fe/Al, and other Hazardous Elements (HEs) and compounds in minute quantities. In this work, we studied the CCRs of industrial facilities in Brazil for the presence of nanoparticles/nanominerals and HEs. CCRs were characterized using Focused Ion Beam (FIB) to evaluate nano-compound assemblages with high resolutiontransmission electron microscopy/energy dispersive spectroscopy (HR-TEM/EDS) to assess the extent of risk to human health. In the present work, the importance of nanogeoscience in the description of CCRs and HEs in several secondary phases deposits (e.g. Fe and Al-sulfates, oxides and hydroxides minerals) has been emphasized and the presence of HEs in Brazilian coal abandoned area has been confirmed. This innovative study used an advanced characterization that will be useful in understanding the extent of environmental risk as well as a threat to human health, associated with CCRs.

Geochemical and Morphological Evaluations of Organic and Mineral Aerosols in Coal Mining Areas: A Case Study of Santa Catarina, Brazil

“…The morphology and geochemical conformations of the PM in the accumulated samples were examined by FE-SEM fitted with EDS under secondary electron (SE) and backscattered electron modes [32,33]. The SEM was operated at 15 kV accelerating voltage and 0.1 nA beam current.…”

A review of the mineralogical and chemical composition of nanoparticles associated with coal fires

“…However, these polar solutions dissolve the soluble salt minerals (polar phases) that occur in the nano‐size fraction of materials collected in the thermal alteration aureole of coal fires (see below). Hence, the deposition of NPs containing a mixture of polar and non‐polar phases is commonly conducted with nonpolar or weakly polar solutions such as methanol or a mixture of acetone and hexane (Gieré et al., 2006; Oliveira et al., 2018; Oliveira et al., 2019; Ribeiro et al., 2010).…”

“…Although mineralogical samples from coal fires have been prepared with the focused ion beam (FIB) technology (Oliveira et al, 2018(Oliveira et al, , 2019Silva, Crissien, Schneider, et al, 2020), the most common preparation technique for TEM is the deposition of PM on TEM grids (see above). However, this technique does not preserve the textural relationship between NPs of different origin or formed under different conditions.…”

Geochemical and environmental assessment of potential effects of trace elements in soils, water, and sediments around abandoned mining sites in the northern Iberian Peninsula (NW Spain)

“…However, it contains significant levels of As, Cd, Hg, Pb, and Sb in average concentrations of 1.5, 0.2, 0.08, 13, and 0.2 mg/kg, respectively, in the earth's crust [ [7] , [8] , [9] ]. The composition of water resources can be affected by different factors, one of which can be acid mine drainage and leachate, suspended solids, soil erosion, mining waste in surface waters [ 10 ], dispersion in rivers rainfall, and other hydrological processes [ 11 , 12 ]. Acidic solutions produced by mine drainage and industrial activities can reach the surface water or groundwater according to the hydrogeology of the site, leading to the deterioration of water quality by accumulation and transport of sediment that is detrimental to health [ 13 , 14 ].…”