Félix A. López

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 extraction of mineral acids by the phosphine oxide Cyanex 923

The distribution equilibria of mineral acids: H2SO4, H3PO4, HCI, HClO4 and HNO3 between aqueous solutions and organic solutions of the phosphine oxide Cyanex 923 in toluene or decane are described. Partition studies have shown that the organic diluent only slightly influences the acid extraction. The extraction mechanism can be related to the solvation of the acid and formation of the L · Hm+Xm−1 (m = 1, 2 or 3) species in the organic phase, where L is the extractant; only in the case of initial high HNO33 concentrations is the formation of the L · (HNO3)2 species apparent in this phase. The effect of temperature on the acid extraction is also evaluated.

Distillation of granulated scrap tires in a pilot plant

This paper reports the pyrolytic treatment of granulated scrap tires (GST) in a pilot distillation unit at moderate temperature (550°C) and atmospheric pressure, to produce oil, char and gas products. Tire-derived oil is a complex mixture of organic C(5)-C(24) compounds, including a very large proportion of aromatic compounds. This oil has a high gross calorific value (∼ 43 MJ kg(-1)) and N and S contents of 0.4% and 0.6%, respectively, falling within the specifications of certain heating fuels. The distillation gas is composed of hydrocarbons; methane and n-butane are the most abundant, investing the distillation gas with a very high gross calorific value (∼ 68 MJ Nm(-3)). This gas is transformed into electric power by a co-generation turbine. The distillation char is mostly made of carbon but with significant inorganic impurities (∼ 12 wt%). The quality of the solid residue of the process is comparable to that of some commercial chars. The quantity of residual solids, and the qualities of the gas, liquid and solid fractions, are similar to those obtained by conventional pyrolytic treatments of waste tires. However, the simplicity of the proposed technology and its low investment costs make it a very attractive alternative.

A comparative study on copper corrosion originated by formic and acetic acid vapours

The copper corrosion rate and products originated by the action of formic and acetic acid vapours at a 100% relative humidity were studied. Copper specimens were exposed to formic and acetic acid vapours for a period of 21 days. Five formic and acetic acid vapour concentrations (10, 50, 100, 200 and 300 ppm) were tested. Copper corrosion rates of up to 1300 mg m−2 d−1 (mmd) for formic acid and up to 2300 mmd for acetic acid were measured using a gravimetric method. The corrosion-product layers were characterised using electrochemical, X-ray powder diffraction and scanning electron microscopy techniques. Some of the compounds identified were: cuprite (Cu2O), for both acids; cupric hydroxide monohydrate (Cu(OH)2 · H2O) and copper formate tetrahydrate (Cu(HCOO)2 · 4H2O), for formic acid; and copper acetate dihydrate (Cu(CH3COO)2 · 2H2O) and copper hydroxide acetate dihydrate (Cu4(OH)(CH3COO)7 · 2H2O), for acetic acid.

Copper Corrosion Mechanism in the Presence of Formic Acid Vapor for Short Exposure Times

The rate of copper corrosion originated by the action of formic acid vapors at 100% relative humidity was studied. Five formic vapor concentration levels (10, 50, 100, 200, and 300 ppm) were used. A copper corrosion rate of up to 1,300 mg/m{sup 2} d was measured for a period of 21 days using a gravimetric method. The patina layers were characterized using cathodic reduction, X-ray powder diffraction. Fourier transform infrared spectrometry, and scanning electron microscopy techniques. Some of the components identified in the corrosion-product layers were cuprite (Cu{sub 2}O), cupric hydroxide hydrate [Cu(OH){sub 2}{sm_bullet}H{sub 2}O], and copper formate hydrate [Cu(HCOO){sub 2}{sm_bullet}4H{sub 2}O]. The latter was formed by both cupric hydroxide and formic acid-cuprous ion complex mechanisms.

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.

Study of the extraction of gold(III) in aqueous hydrochloric acid media by the phosphine oxide Cyanex 925

Abstract The extraction of gold(III) from hydrochloric acid solutions by means of the phosphine oxide Cyanex 925 was studied as a function of different variables: equilibration time, temperature, organic diluent, and concentration of gold, Cyanex 925, HCl, etc.; the system is selective with respect to the extraction of a number of metals. Gold(III) equilibrium loading isotherms were also obtained at 20°C. Experimental data were treated numerically showing that gold extraction can be explained assuming the formation of a complex with the general stoichiometry: HAuCl 4 L 2 , where L represents the extractant. For the extraction reaction log K ext o = 8.1. The stripping of gold from loaded organic phases can be achieved with water. Data on the extraction of HCl by Cyanex 925 are also presented.

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.