J.L. Rico

Hydrogen production from methane in the presence of red mud –making mud magnetic

Red mud, a waste product of the aluminium industry, has been shown to possess significant activity for the decomposition of methane, a by-product of oil refining and landfill, generating hydrogen and a carbon containing magnetic material. It is envisaged that the latter material could be of interest in terms of downstream purification processes and that its magnetic properties may facilitate separation/handling. In this way, two valuable end products can be generated from two waste products.

Carbon deposition and phase transformations in red mud on exposure to methane

A characterization study detailing the phase transformations and microstructural nature of the carbon deposited during methane decomposition over red mud has been undertaken. In situ XRD was carried out to study the phase transformation sequences of red mud during the reaction. Scanning electron microscopy, high resolution transmission electron microscopy, thermogravimetric analysis, BET surface area determination and CHN analysis were carried out to investigate the properties of the post-reaction samples. Exposure to methane with increasing temperature caused a stepwise reduction of iron oxides in red mud and promoted methane cracking leading to carbon deposition. The presence of carbon nanostructures was confirmed by HRTEM observations. The carbon formed was graphitic in nature and the spent red mud, rich in Fe and Fe(3)C formed as a result of the reduction of the iron oxide, was magnetic in nature. The surface area of the material was enhanced upon reaction. In addition, reactivity comparisons between goethite and red mud were carried out to study the formation of carbon oxides during reaction.

Carbonised red mud – A new water treatment product made from a waste material

Proposals to use red mud, the waste produced by the extraction of alumina from bauxite ore in the Bayer process, as a material for treatment of heavy metal-contaminated water are limited by its inherent alkalinity and variability. Attempts to lower its pH have been largely unreliable. However, an alternative strategy is carbonisation of red mud by catalytic hydrocarbon cracking, which results in a magnetic material of greater surface area. The efficacy of this material has been compared with that of the untreated parent red mud and acidified red mud for the sorption of CrO(4)(2-), Cu(2+) and Pb(2+). Carbonised red mud does not remove CrO(4)(2-) from solution, but shows enhancement of Cu(2+) and Pb(2+) removal. There is an approximate ten-fold increase in removal of Cu(2+) and Pb(2+) by carbonised red mud compared with acidified red mud.

Potential Routes to Obtain Value-Added Iron-Containing Compounds from Red Mud

Red mud, an aluminum industry large-scale waste, was used as a precursor to prepare sodium ferrate(VI) and sodium ferrite following different reaction pathways. Ferrous oxalate extracted from red mud has been used as an intermediate for the preparation of these compounds. The conversion rate to sodium ferrate(VI) from ferrous oxalate was as high as 64% in sodium hydroxide solution with sodium hypochlorite. Furthermore, sodium ferrite was formed after performing the solid–solid reaction at 600xa0°C using a 1:1 weight ratio of iron oxide (prepared via the ferrous oxalate extraction route from red mud) and sodium peroxide. In contrast, sodium iron silicon oxides were formed when red mud was reacted directly, following similar experimental procedures. These results present an interesting alternative to convert an environmentally unfriendly waste to new value-added products. It is envisaged that sodium ferrate(VI) might be of great interest in terms of wastewater treatment, whereas sodium ferrite and NawFexSiyOz might be of interest in the development of new materials for energy storage.

Synthesis and characterization of iron and iron nitride microtubes obtained from biogenic iron oxide

AbstractnWith the aim to obtain iron tubular microstructures attractive for various applications, we have used a natural biogenic iron ochre as a raw material and explore various procedures and experimental conditions to achieve our goal. Our experiments included reduction, nitridation and characterization of microtubes derived from biogenic iron ochre. Various temperatures of reduction under streams of H2/N2 or NH3 were tested. Our results show that the tubular structure is maintained after reduction of the natural material under H2/N2. In addition, ammonia was not produced under our experimental conditions, and as expected, hydrogen reduced the material. However, the treatment under NH3 reduces the material and allows the incorporation of nitrogen into the structure of the solid yielding iron nitride microtubes. Reduced and nitrided microstructures were successfully obtained from natural biogenic iron ochre. A temperature of 500xa0°C seems to be suitable to expose the calcined biogenic iron ochre under H2/N2 for 4xa0h or under ammonia for 8xa0h to obtain reduced or nitrided microtubes, respectively. The stability of the tubular structure during reduction/reduction–nitridation is maintained under both treatments. Further interesting applications of this natural biomaterial could be envisaged.

Methane Cracking over Cobalt Molybdenum Carbides

The catalytic behaviour of Co3Mo3C, Co6Mo6C, Co3Mo3N and Co6Mo6N for methane cracking has been studied to determine the relationship between the methane cracking activity and the chemical composition. The characterisation of post-reaction samples showed a complex phase composition with the presence of Co3Mo3C, α-Co and β-Mo2C as catalytic phases and the deposition of different forms of carbon during reaction.Graphical Abstract