Iron: a versatile element to produce materials for environmental applications

Abstract

Ferro é um elemento versátil que forma várias fases com diferentes estados de oxidação e estruturas, tais como Fe 0 , FeO, Fe 3 O 4 , γ-Fe 2 O 3 , α-Fe 2 O 3 e FeOOH. Todas estas fases têm propriedades físico-químicas únicas que podem ser usadas para diferentes aplicações. Neste trabalho, descreve-se o uso de diferentes compostos de ferro, sintéticos e também naturais ou de rejeitos, em aplicações ambientais e tecnológicas. Duas áreas principais de pesquisa são descritas. A primeira é relacionada às estratégias para aumentar a reatividade de fases de ferro pela formação de compósitos Fe 0 /Fe óxido e pela introdução de novos metais na estrutura de óxidos de ferro para promover novas reações superficiais. A segunda área de pesquisa é o uso das propriedades magnéticas de algumas fases de ferro para produzir materiais magnéticos versáteis com aplicações focadas em adsorção, catálise e emulsões.Iron is a versatile element forming several phases with different oxidation states and structures, such as Fe 0 , FeO, Fe 3 O 4 , γ-Fe 2 O 3 , α-Fe 2 O 3 and FeOOH. All these phases have unique physicochemical properties which can be used for different applications. In this work, it is described the use of different iron compounds, synthetic and also from natural and waste sources, in environmental and technological applications. Two main research areas are described. The first one is related to strategies to increase the reactivity of Fe phases, mainly by the formation of Fe 0 /iron oxide composites and by the introduction of new metals in the iron oxide structure to promote new surface reactions. The second area is the use of the magnetic properties of some iron phases to produce versatile magnetic materials with focus in adsorption, catalysis and emulsions.

Catalytic oxidation of aqueous sulfide in the presence of ferrites (MFe2O4, M=Fe, Cu, Co)

“…The XRD data suggests that maghemite sample is composed mainly of ␥-Fe 2 O 3 (maghemite) (JCPDF 39-1346) and some hexagonal hematite phase ␣-Fe 2 O 3 (JCPDF 13-534). This structural change maghemite-hematite at 400 • C has been observed before [26].…”

Climate engineering by mimicking natural dust climate control: the iron salt aerosol method

“…By expanding the aqueous interface, accelerations of the reaction velocity up to 3 orders of magnitude has been measured (Enami et al, 2014). This may be one of the reasons why ironcontaining solid surfaces made of fractal iron oxides, pyrite, activated carbon, graphite, carbon nanotubes, vermiculite, pillared clays and zeolites have been tested as efficient Fenton reagents (Pignatello et al, 2006;Pinto et al, 2012;Teixeira et al, 2012).…”

Magnetic N-doped carbon nanotubes: A versatile and efficient material for the determination of polycyclic aromatic hydrocarbons in environmental water samples

“…These Fe nanoparticles are formed during CVD process by the reduction of the iron oxide by the carbon sources at high temperatures. As the carbon nanostructures grow around these nanocatalysts encapsulation takes place and trap these magnetic metallic nanoparticles inside the CNT [24] The presence of these metal cores encapsulated (5.0% w/w) allows these materials to be removed from the medium by a magnetic field [25][26][27]. It can also be observed the presence of internal caps due to defects caused by the presence of N atoms in the CNT structure [20].…”