Magnetic study of a mixture of magnetite and metallic iron in indoor dust samples

Abstract

Magnetite in mixture with metallic iron in indoor dust samples was examined using several magnetic analyses, thermomagnetic curves of the magnetic susceptibility and the induced magnetization vs. temperature, hysteresis loops, and first-order reversal curves. The study of the magnetic properties was supplemented by the analysis of chemical elements and electron microscopic observation. The metallic iron in the mixture affects the values of hysteresis parameters, decreasing coercivity (B c) and increasing saturation magnetization (M s), and it is responsible for the magnetic enhancement of magnetic susceptibility. The thermomagnetic curves show several distinct features: the first Curie temperature of magnetite, the second one (∼764 °C) of iron, and the rapid decrease on the heating curves (between 600 and 750 °C) caused by the oxidation of iron to magnetite. Two magnetochemical processes appear during the thermal treatment of indoor dust: the oxidation of iron to magnetite and the neo-formation of magnetite as a result of chemical transformation of non-magnetic minerals. The shift of the hysteresis parameter ratios from the multi-domain (MD) region towards the single-domain (SD) region on the Day-Dunlop plot is controlled by the oxidation of iron in the thermally induced process and the grain size of the new formed magnetite. The magnetic properties of indoor dust are a potential indicator of indoor air pollution. Elemental iron plays an important role in the development of inflammation in humans via oxidative stress, so that the presence of metallic Fe in indoor dust can affect human health.

Barking up the Right Tree: Using Tree Bark to Track Airborne Particles in School Environment and Link Science to Society

“…The mean I/O for EC for both sampled season periods equals 0.6 in both schools, similar to the one obtained from total magnetic PM measured on bio‐sensors (0.6 and 0.9, respectively for School 1 and 2). The magnetic fraction of PM found indoors also points to external sources, hence traffic sources, in agreement with previous studies that found that magnetic particles on household dust are derived from traffic and industrial activities (Beata Górka‐Kostrubiec & Iga Szczepaniak‐Wnuk, 2017 ; Jelenska et al., 2017 ; Kelepertzis et al., 2019 ). Other known potential sources of magnetic PM indoors are cooking, combustion processes, smoking (Jordanova et al., 2006 ) and laser printing (ink composed of nanoparticles, Pirela et al., 2015 ), all of which are absent in the studied schools.…”

“…( 2009 ) and Sagnotti and Winkler ( 2012 ) from exhaust residues from gasoline and diesel motors as well from brake wear dust collected directly in situ. This could result from different sources of particles, meaning different magnetic mineralogy such as high coercivity minerals like hematite(of geological origin e.g.,) or metallic iron (linked to abrasion of combustion cylinder, pads and disk brakes), which influences SIRM and coercivity values (Gorka‐Kostrubiec & Szczepaniak, 2017 ; Gorka‐Kostrubiec et al., 2019 ) and therefore impact the S‐Ratio and/or grain sizes parameters.…”

Characteristics of iron-containing magnetic particles in household dust from an urban area: A case study in the megacity of Shanghai

“…S1 d-f) further confirm metallic Fe particles in the household dust, which is consistent with the thermomagnetic results. These metallic Fe particles are irregular sheetlike or blocky and reported by other studies (Zhang, 2011;Moreno et al, 2015;Gόrka-Kostrubiec et al, 2015;Jeleńska et al, 2017;Gόrka-Kostrubiec and Szczepaniak, 2017). Jeleńska et al, (2017) found angular, metallic Fe particles in office dust in Warsaw (Poland) and considered that these particles were possibly generated by the abrasion of vehicle suspension components.…”

Integrated Magnetic Analyses for the Discrimination of Urban and Industrial Dusts

“…Meanwhile, a continuous decrease of magnetic susceptibility up to 700 • C for sample 19 can be observed, suggesting the presence of a high-temperature magnetic phase. According to previous studies on the magnetic mineralogy of street dust from Warsaw [27,28], this tail on the curve of κ(T) between 600 and 700 • C indicates the presence of metallic iron, which exhibits a Curie temperature of 780 • C [50,[60][61][62]. The heating curve of κ(T) for sample 32 does not show metallic Fe as the value of κ above the T C for magnetite is almost zero.…”