Aurora López-Delgado

Sorption of heavy metals on blast furnace sludge

An investigation into the use of sludge, a by-product of the steel industry, as an adsorbent for the removal of heavy metals from liquid effluents was carried out. Gases produced in the blast furnace were washed and led towards a Dorr thickener where the sludge was obtained as a suspension. The sorption of Pb2+, Zn2+, Cd2+, Cu2+ and Cr3+ on the sludge was investigated by determination of adsorption isotherms. The effects of time, equilibrium temperature and concentration of metal solution on sludge adsorption efficiency was evaluated. The adsorption process was analyzed using the theories of Freundlich and Langmuir and the thermodynamic values of ΔG, ΔH and ΔS corresponding to each adsorption process were calculated. Blast furnace sludge was found to be an effective sorbent for Pb, Zn, Cd, Cu and Cr–ions within the range of ion concentrations employed.

The effect of the starting solution on the physico-chemical properties of zinc ferrite synthesized at low temperature

Abstract Fine particle zinc ferrite powders (ZnFe2O4) were synthesized by co-precipitation of a bi-ionic Fe3+/Zn2+ solution with 1 M n-butylamine at low temperature. Ferric nitrate and ferrous sulphate solutions were used as the starting material to investigate the effect of the source of iron on particle size, morphology, thermal behaviour and surface area of the final products. ZnFe2O4. In both cases, Zn2+ ions were provided by ZnO. The ferrous ions of the sulphate solution were previously oxidized with H2O2 in sulphuric medium. The cubic spinel-type structure of the ferrite product was obtained at a lower temperature when nitrate solution was used. Zinc ferrite of smaller particle size and higher surface area was obtained when ferrous sulphate was used as the starting solution. The ferrite precursors produced at room temperature and final products were characterized by X-ray powder diffraction, Fourier transformed infrared spectroscopy, thermal analyses, scanning and transmission electron microscopy and nitrogen adsorption volumetry.

Removal of copper ions from aqueous solutions by a steel-making by-product

A study is made of the use of a steel-making by-product (rolling mill scale) as a material for removing Cu(2+) ions from aqueous solutions. The influence of contact time, initial copper ion concentration and temperature on removal capability is considered. The removal of Cu(2+) ions from an aqueous solution involves two processes: on the one hand, the adsorption of Cu(2+) ions on the surface of mill scale due to the iron oxides present in the latter; and on the other hand, the cementation of Cu(2+) onto metallic iron contained in the mill scale. Rolling mill scale is seen to be an effective material for the removal of copper ions from aqueous solutions.

Pseudo-emulsion membrane strip dispersion (PEMSD) pertraction of chromium(VI) using CYPHOS IL101 ionic liquid as carrier

The transport of chromium(VI) from hydrochloric acid medium by pseudoemulsion membrane strip dispersion (PEMSD), using CYPHOS IL101 (phosphonium salt) as ionophore, is investigated under various experimental variables in the feed phase [hydrodynamic conditions, concentration of Cr(VI) (0.01-1 g/L), concentration of HCl (0.01-1M)], in the organic phase [carrier concentration (1-10% v/v)], and in the strip phase (stripping agent). Other variables investigated were the volume organic/strip phase ratios in the pseudoemulsion phase and also the type of membrane support. Under given experimental conditions, i.e., [Cr(VI)](0) = 0.01 g/L and [HCl](0) = 0.01 M in the feed phase and organic solution of 10% v/v CYPHOS IL101 in cumene, extractions exceeding 95% are obtained, and it is possible to strip using 1 M NaoH solution (also with recoveries in the 60% range). The performance of the system is also compared against other membrane operational configurations.

Uphill permeation of Cr(VI) using Hostarex A327 as ionophore by membrane-solvent extraction processing.

The transport of chromium by the emulsion pertraction technology (EPERT) using Hostarex A327 (tertiary amine) as a carrier has been investigated. The permeation of the metal is studied as a function of various experimental variables: hydrodynamic conditions, concentration of Cr(VI) and HCl in the source phase, carrier concentration and diluent in the organic phase, strippant concentration in the stripping phase and support characteristics of the membrane. The mass transfer coefficient and the thickness of the aqueous source boundary layer were estimated from the experimental data. Furthermore, the selectivity of the Hostarex A327-bases EPERT towards different metal ions and the behaviour of the system against other carriers are presented.

Concerns on liquid mercury and mercury-containing wastes: a review of the treatment technologies for the safe storage.

Due to the adverse effects of mercury on human health and the environment, restrictive legislations and world-wide common efforts are now under way to reduce both the supply and demand of mercury. As a result, all excess Hg must be stored in safe conditions in secure places. This paper is an attempt to review the various treatment technologies types of liquid mercury (Hg(0)) and mercury-containing wastes, which can be used to store these residues in a safe way. The different treatments were classified as a function of the waste treated. The main treatments described are amalgamation, formation of sulfides, thermal treatments, vitrification, soil washing, sulfur polymer stabilization solidification, chemically bonded phosphate ceramics and other encapsulation processes, being highlighted the stabilization/solidification processes that are the treatments that provide better results, according to the consulted bibliography.

Can hazardous waste become a raw material? The case study of an aluminium residue: a review

The huge number of research studies carried out during recent decades focused on finding an effective solution for the waste treatment, have allowed some of these residues to become new raw materials for many industries. Achieving this ensures a reduction in energy and natural resources consumption, diminishing of the negative environmental impacts and creating secondary and tertiary industries. A good example is provided by the metallurgical industry, in general, and the aluminium industry in this particular case. The aluminium recycling industry is a beneficial activity for the environment, since it recovers resources from primary industry, manufacturing and post-consumer waste. Slag and scrap which were previously considered as waste, are nowadays the raw material for some highly profitable secondary and tertiary industries. The most recent European Directive on waste establishes that if waste is used as a common product and fulfils the existing legislation for this product, then this waste can be defined as ‘end-of-waste’. The review presented here, attempts to show several proposals for making added-value materials using an aluminium residue which is still considered as a hazardous waste, and accordingly, disposed of in secure storage. The present proposal includes the use of this waste to manufacture glass, glass-ceramic, boehmite and calcium aluminate. Thus the waste might effectively be recovered as a secondary source material for various industries

Gasification of the char derived from distillation of granulated scrap tyres

This work reports the effect of pressure on the steam/oxygen gasification at 1000°C of the char derived from low temperature-pressure distillation of granulated scrap tyres (GST). The study was based on the analysis of gas production, carbon conversion, cold gas efficiency and the high heating value (HHV) of the product. For comparison, similar analyses were carried out for the gasification of coals with different rank. In spite of the relatively high ash (≈12 wt.%) and sulphur (≈3 wt.%) contents, the char produced in GST distillation can be regarded as a reasonable solid fuel with a calorific value of 34MJkg(-1). The combustion properties of the char (E(A)≈50 kJ mol(-1)), its temperature of self-heating (≈264°C), ignition temperature (≈459°C) and burn-out temperature (≈676°C) were found to be similar to those of a semi-anthracite. It is observed that the yield, H(2) and CO contents and HHV of the syngas produced from char gasification increase with pressure. At 0.1 MPa, 4.6 Nm(3)kg(char)(-1) of syngas was produced, containing 28%v/v of H(2) and CO and with a HHV around 3.7 MJ Nm(-3). At 1.5 MPa, the syngas yield achieved 4.9N m(3)kg(char)(-1) with 30%v/v of H(2)-CO and HHV of 4.1 MJ Nm(-3). Carbon conversion significantly increased from 87% at 0.1 MPa to 98% at 1.5 MPa. It is shown that the char derived from distillation of granulated scrap tyres can be further gasified to render a gas of considerable heating value, especially when gasification proceeds at high pressure.

A hazardous waste from secondary aluminium metallurgy as a new raw material for calcium aluminate glasses

A solid waste coming from the secondary aluminium industry was successfully vitrified in the ternary CaO-Al(2)O(3)-SiO(2) system at 1500 degrees C. This waste is a complex material which is considered hazardous because of its behaviour in the presence of water or moisture. In these conditions, the dust can generate gases such as H(2), NH(3), CH(4), H(2)S, along with heat and potential aluminothermy. Only silica sand and calcium carbonate were added as external raw materials to complete the glasses formula. Different nominal compositions of glasses, with Al(2)O(3) ranging between 20% and 54%, were studied to determine the glass forming area. The glasses obtained allow the immobilisation of up to 75% of waste in a multicomponent oxide system in which all the components of the waste are incorporated. The microhardness Hv values varied between 6.05 and 6.62GPa and the linear thermal expansion coefficient, alpha, varied between (62 and 139)x10(-7)K(-1). Several glasses showed a high hydrolytic resistance in deionised water at 98 degrees C.

Quality of ferrous scrap from MSW incinerators: a case study of Spain

Abstract The recovery of packaging steel from municipal solid waste (MSW) plays an important role in scrap recycling. Post-consumer packaging steel quality depends strongly on the procedure and the technology employed for its collection and recovery. Household refuse management systems include classification, compost and incineration plants. In Spain, MSW incineration is carried out by nine incinerators that generate a total of around 40 000 t of ferrous scrap every year. Two types of furnace are used for the incineration process, namely mobile grate furnaces (MGF) and fluidised bed furnaces (FBF). Slag from the process is comprised by the incombustible materials of MSW (vitreous materials, ceramic materials, ferrous and nonferrous metals). Slag accounts for 85–95% of the total solid waste mass. About 95% of the metallic fraction corresponds to ferrous scrap. The objective of this paper was to determine the current quality of scrap from incinerators and to study the causes of alteration of steel, i.e. of the corrosion of its surface, attempting to relate these parameters with the technology used in the combustion of MSW and the cooling treatment applied to the slag. A process for enhancing the quality of ferrous scrap from MSW is described, which includes fragmentation and magnetic separation stages.