Irene García-Díaz

Microencapsulation of phosphogypsum into a sulfur polymer matrix: Physico-chemical and radiological characterization

The aim of this work is to prepare a new type of phosphogypsum-sulfur polymer cements (PG-SPC) to be utilised in the manufacture of building materials. Physico-chemical and radiological characterization was performed in phosphogypsum and phosphogypsum-sulfur polymer concretes and modeling of exhalation rates has been also carried out. An optimized mixture of the materials was obtained, the solidified material with optimal mixture (sulfur/phosphogypsum=1:0.9, phosphogypsum dosage=10-40 wt.%) results in highest strength (54-62 MPa) and low total porosity (2.8-6.8%). The activity concentration index (I) in the PG-SPC is lower than the reference value in the most international regulations and; therefore, these cements can be used without radiological restrictions in the manufacture of building materials. Under normal conditions of ventilation, the contribution to the expected radon indoor concentration in a standard room is below the international recommendations, so the building materials studied in this work can be applied to houses built up under normal ventilation conditions. Additionally, and taking into account that the PG is enriched in several natural radionuclides as (226)Ra, the leaching experiments have demonstrated that environmental impact of the using of SPCs cements with PG is negligible.

The removal of chromium (III) from aqueous solution by ion exchange on Amberlite 200 resin: batch and continuous ion exchange modelling

Abstract The use of ion exchange technology is studied for the removal of chromium (III) from acidic waste solution by Amberlite 200 resin. Batch and column experimental tests were conducted to provide data for theoretical models and verify the system performance of the removal process. Results of batch equilibrium tests indicated that Langmuir isotherm describes well the adsorption process, whereas experimental data also provide evidence that, under the present experimental conditions, the rate law which controlled chromium (III) adsorption by Amberlite 200 resin depends of the resin particle size; on the other hand, the theoretical model used in the present investigation was found to predict reasonably well the ion exchange breakthrough performance.

Valorisation of waste ilmenite mud in the manufacture of sulphur polymer cement

This paper reports the preparation of sulphur polymer cements (SPCs) incorporating waste ilmenite mud for use in concrete construction works. The ilmenite mud raw material and the mud-containing SPCs (IMC-SPCs) were characterised physico-chemically and radiologically. The optimal IMC-SPC mixture had a sulphur/mud ratio (w/w) of 1.05 (mud dose 20 wt%); this cement showed the greatest compressive strength (64 MPa) and the lowest water absorption coefficient (0.4 g cm(-2) at 28 days). Since ilmenite mud is enriched in natural radionuclides, such as radium isotopes (2.0·10(3) Bq kg(-1)(228)Ra and 5.0·10(2) Bq kg(-1)(226)Ra), the IMC-SPCs were subjected to leaching experiments, which showed their environmental impact to be negligible. The activity concentration indices for the different radionuclides in the IMC-SPCs containing 10% and 20% ilmenite mud met the demands of international standards for materials used in the construction of non-residential buildings.

Transport of Cr(VI) from HCl Media Using (PJMTH+Cl−) Ionic Liquid as Carrier by Advanced Membrane Extraction Processing

The transport of Cr(VI) from acidic media through pseudo-emulsion based membrane strip dispersion (PEMSD) containing the ionic liquid (PJMTH+Cl−) as carrier in the form of a pseudo-emulsion with sodium hydroxide has been investigated. The ionic liquid was generated in situ by reaction of the primary amine Primene JMT and HCl. The transport of Cr(VI) is evaluated as a function of various experimental variables: stirring speed in the feed phase, concentration of Cr(VI) and HCl in the feed phase, carrier concentration, and organic diluents in pseudo-emulsion, and NaOH concentration in pseudo-emulsion as strippant. In PEMSD, pseudo-emulsion is an emulsion that is formed temporarily between the organic and the stripping solutions. Both solutions are separated when the stirring device is stopped. The value of the overall permeation coefficient obtained under standard experimental conditions was 3.1 × 10−3 cm s−1, whereas the transport process is controlled by diffusion of chromium species in the stagnant film of the feed phase. The performance of the system against other carriers (amines, quaternary phosphonium salt and quaternary ammonium salt) was also evaluated.

Membrane-based extraction with strip/organic dispersion methodologies for metals removal and recovery from wastewaters

Abstract The generation of liquid effluents containing organic and inorganic residues from industries presented a potential hazardousness for environment and human health, being mandatory the elimination of these pollutants from the respective solutions containing them. In order to achieve this goal, several techniques are being used, and among them, supported liquid membranes technologies are showing their potential for their application in the removal of metals contained in liquid effluents. Supported liquid membranes are a combination between conventional polymeric membranes and solvent extraction. Several configurations are used: flat-sheet supported liquid membranes, spiral wounds and hollow fiber modules. In order to improve their effectiveness, smart operations have been developed: pseudo-emulsion membrane based strip dispersion (PEMSD), pseudo-emulsion based hollow fiber strip dispersion (PEHFSD), hollow fiber renewal liquid membrane (HFRLM) and double strip dispersion hybrid liquid membrane (SDHL...

Sorption of indium (III) onto carbon nanotubes.

Indium has numerous applications in different industrial sectors and is not an abundant element. Therefore appropriate technology to recover this element from various process wastes is needed. This research reports high adsorption capacity of multiwalled carbon nanotubes (MWCNT) for In(III). The effects of pH, kinetics, isotherms and adsorption mechanism of MWCNT on In(III) adsorption were investigated and discussed in detail. The pH increases improves the adsorption capacity for In(III). The Langmuir adsorption model is the best fit with the experimental data. For the kinetic study, the adsorption onto MWCNT could be fitted to pseudo second-order. The adsorption of indium(III) can be described to a mechanism which consists of a film diffusion controlled process. Metal desorption can be achieved with acidic solutions.

Recycling of copper flue dust via leaching-solvent extraction processing

AbstractA laboratory-/bench-scale investigation relating to copper recovery from Chilean copper flue dust is described. Since the dust contained a high amount of copper (nearly 24%), the considered option consisted in the leaching of the metallic material with ammonium chloride solution, thus enabling the dissolution of copper via its ammoniacal complexes, and also rendering, due to the almost neutral conditions of the leaching solution, a near complete lean solution with respect to the presence of other metal accompanying in the dust. Results obtained show that with ammonium chloride solutions, nearly 90% of the copper contained in the dust can be leached at 20°C. Copper enters the solvent extraction-electrowinning circuit due to the following equilibria:regenerating both the leaching and the solvent extraction reagents. In the above equation, HR represented the active substance of the extractant (Acorga PT5050) used in the solvent extraction circuit; the first of the above equilibria is related to the e...

Transport of Cr(VI) using an advanced membrane technology and (PJMTH+NO3−) ionic liquid derived from amine Primene JMT as green chemicals

AbstractThe extraction of Cr(VI) from acidic solutions through pseudo-emulsion-based membrane strip dispersion (PEMSD) was conducted in a microporous hydrophobic polyvinylidenedifluoride (PVDF) membrane support and permeation cell. As organic extractant ionic liquids derived from the primary amine Primene JMT in cumene was used. The acidic feed solution containing Cr(VI) was placed in one side of the permeation cell, whereas the pseudo-emulsion of Primene JMT/cumene and acidic solution was placed in the other side of the cell, using a single microporous hydrophobic PVDF membrane support for extraction and stripping. In PEMSD the aqueous acidic (HNO3) solution was dispersed into the organic (Primene JMT/cumene) membrane solution with a mixing arrangement (impeller stirrer) designed to form a strip dispersion. This operation mode provides a constant supply of the ionic liquid extractant/cumene solution to the membrane pores. Various hydrodynamic and chemical parameters, either in the feed or in the pseudo-e...

Oxidation and waste-to-energy output of aluminium waste packaging during incineration: A laboratory study

This work reports the oxidation behaviour and waste-to-energy output of different semi-rigid and flexible aluminium packagings when incinerated at 850°C in an air atmosphere enriched with 6% oxygen, in the laboratory setting. The physical properties of the different packagings were determined, including their metallic aluminium contents. The ash contents of their combustion products were determined according to standard BS ISO 1171:2010. The net calorific value, the required energy, and the calorific gain associated with each packaging type were determined following standard BS EN 13431:2004. Packagings with an aluminium lamina thickness of >50μm did not fully oxidise. During incineration, the weight-for-weight waste-to-energy output of the packagings with thick aluminium lamina was lower than that of packagings with thin lamina. The calorific gain depended on the degree of oxidation of the metallic aluminium, but was greater than zero for all the packagings studied. Waste aluminium may therefore be said to act as an energy source in municipal solid waste incineration systems.

Luminescence and gas-sensing properties of ZnO obtained from the recycling of alkaline batteries

The great amount of wasted alkaline batteries produced nowadays constitutes a driving force for obtaining valuable materials from the recycling process. Zn is one of the major components of the batteries residues; hence, the possibility to obtain good quality ZnO appears very attractive. In this work, we have characterized ZnO obtained by different synthesis routes from the black mass produced during the mechanical recycling process. The luminescent behaviour has been studied and compared to that of the commercial ZnO. Chromaticity has been analysed through the corresponding CIE [Commission Internationale d’Eclairage (CIE) 1931] coordinates, obtained from the emission spectra. The possible response to gases from the ZnO obtained from the different sources has been also investigated. While ZnO from recycling does not show an appreciable gas sensitivity, the possibility to follow different calcination routes and hence obtaining ZnO with different defect structures and luminescent behaviour open the way to tailor the colour of the emitted light.