C. Fernández Pereira

Stabilization/solidification of a municipal solid waste incineration residue using fly ash-based geopolymers.

The stabilization/solidification (S/S) of a municipal solid waste incineration (MSWI) fly ash containing hazardous metals such as Pb, Cd, Cr, Zn or Ba by means of geopolymerization technology is described in this paper. Different reagents such as sodium hydroxide, potassium hydroxide, sodium silicate, potassium silicate, kaolin, metakaolin and ground blast furnace slag have been used. Mixtures of MSWI waste with these kinds of geopolymeric materials and class F coal fly ash used as silica and alumina source have been processed to study the potential of geopolymers as waste immobilizing agents. To this end, the effects of curing conditions and composition have been tested. S/S solids are submitted to compressive strength and leaching tests to assess the results obtained and to evaluate the efficiency of the treatment. Compressive strength values in the range 1-9 MPa were easily obtained at 7 and 28 days. Concentrations of the metals leached from S/S products were strongly pH dependent, showing that the leachate pH was the most important variable for the immobilization of metals. Comparison of fly ash-based geopolymer systems with classical Portland cement stabilization methods has also been accomplished.

The importance of metallic elements in wine. A literature survey

ZusammenfassungEine Untersuchung über die Rolle der metallischen Elemente im Wein wurde abgeschlossen. Das Ziel dieser Untersuchung war, die Bedeutung der Elemente bei der Herstellung des Weines, hauptsächlich ihren Einfluß auf die sensorischen Eigenschaften, zu beweisen. In erster Linie wurden bei dieser Arbeit die verschiedenen Phasen der Weinherstellung, wie Düngung, Gärung oder Altern, betrachtet, um schließlich auch andere interessante Aspekte, z. B. hygienische und diätische oder die mögliche Differenzierung der Weine aufgrund ihrer metallischen Elemente zu behandeln.SummaryA review of the current literature concerning the role played by metallic elements present in wine is presented. The aim is to show the importance of these elements in the entire wine-making process, mainly through their influence on the organoleptic properties of wine. The study takes into consideration the individual stages of the process such as fertilization, fermentation and aging and also deals with other interesting aspects related to hygiene and dietetic properties, as well as the possibility of differentiating wines according to their metal contents.

Differential partitioning and speciation of Hg in wet FGD facilities of two Spanish PCC power plants

This paper evaluates the speciation and partitioning of mercury in two Spanish pulverised coal combustion power plants (PP1 and PP2), equipped with wet limestone-based flue gas desulphurisation facilities (FGD) operating with forced oxidation and re-circulation of FGD water streams. These plants are fed with coal (PP1) and coal/pet-coke blends (PP2) with different mercury contents. The behaviour, partitioning and speciation of Hg were found to be similar during the combustion processes but different in the FGD systems of the two power plants. A high proportion (86-88%) of Hg escaped the electrostatic precipitator in gaseous form, Hg2+ being the predominant mercury species (68-86%) to enter the FGD. At this point, a relatively high total Hg retention (72% and 65%) was achieved in the PP1 and PP2 (2007) FGD facilities respectively. However, during the second sampling campaign for PP2 (2008), the mercury removal achieved by the FGD was much lower (26%). Lab-scale tests point to liquid/gas ratio as the main parameter affecting oxidised mercury capture in the scrubber. The partitioning of the gaseous mercury reaching the FGD system in the wastes and by-products differed. In the low mercury input power plant (PP1) most of the mercury (67%) was associated with the FGD gypsum. Moreover in PP2 a significant proportion of the gaseous mercury reaching the FGD system remained in the aqueous phase (45%) in the 2007 sampling campaign while most of it escaped in 2008 (74%). This may be attributed to the scrubber operating conditions and the different composition and chemistry of the scrubber solution probably due to the use of an additive.

Stabilization of a Chromium-Containing Solid Waste: Immobilization of Hexavalent Chromium

This article describes the stabilization/solidification (S/S) of a steel industry waste, using a common type-F fly ash from a coal power station as the main binder. The waste, which contains hazardous levels of metals, may be stabilized by a conventional S/S to achieve permissible Pb, Cd, and Zn concentrations in the Toxicity Characteristic Leaching Procedure (TCLP) leachates of S/S solids. On the other hand, the stabilization of Cr(VI), also present in the waste, requires a reducing pretreatment stage with ferrous sulfate to attain TCLP leachates within limits. A bibliographic study on the stabilization of Cr(VI)-contain-ing wastes is included in the paper, along with a discussion on the lowest Cr concentration in TCLP and aqueous (DIN) leachates.

Stabilization/solidification of hazardous metallic wastes: prediction of leach test performance to optimize S/S mixtures

The main tool available for ascertaining the effectiveness attained by a hazardous waste stabilization/solidification (S/S) process is the chemical analysis of the leachate of the solid product obtained. Moreover, it is a well-known fact that the pH of the leachate is the most significant factor in con trolling the leachability of solidified metal bearing wastes, so the lowest concentrations in the leachate of many important metals appear within an optimum range of this pH. In this paper, a methodology is proposed for predicting the final pH of the leachate of different formulations used in the treatment of metallic industrial wastes. This methodology allows us to adjust the proportion of agents used in the S/S processes. In this method, the neutralization curves must first be obtained by acetic acid titration (GANC) of the mixture components. Based on the GANC curves of the components, the alkaline buffer capacity of the S/S solid can be defined and the final pH of the leachate can be predicted. Excellent concordance has been seen between predicted values and test results. How ever, we have also noticed discrepancies for some wastes and S/S agents. These discrepancies can be attributed to internal alkali-consuming reactions that produce lower final leachate pHs than predicted. The methodology proposed helps iden tify the reactions responsible for this process and helps study the evolution over time of the solids obtained.

Waste Stabilization/Solidification (S/S) of EAF dust using fly ash-based geopolymers. Influence of carbonation on the stabilized solids

The effect of the curing in a carbonated ambient of the solids obtained after the stabilization/solidification (S/S) of metallurgical waste using geopolymerization technology is described in this paper. The electric arc furnace (EAF) dust to stabilize contains hazardous metals such as Pb, Cd, Cr, or Zn. Different geopolymeric agents such as potassium hydroxide, potassium silicate, metakaolin, and blast furnace slag have been used. Mixtures of EAF waste with these geopolymeric materials and class F fly ash as main silica and alumina source have been processed. Samples were submitted to an accelerated carbonation test. Compressive strength tests and different leaching tests for determining the efficiency of heavy metal immobilization have been carried out. Comparison of fly ash-based geopolymer systems with classical Portland cement (OPC) stabilization methods has also been accomplished. Compressive strength values far better than those achieved by hydraulic S/S methods were easily obtained by geopolymer solids at 28 days. Carbonation produced a great increment of compressive strength in samples containing a higher K2O proportion. The geopolymer S/S solids also manifested better leachability behavior in general, showing very promising results. Carbonation effects on pH and on Zn and Pb leachabilities are more marked for OPC than for geopolymer S/S solids. f 2010 The University of Kentucky Center for Applied Energy Research and the American Coal Ash Association All rights reserved. A R T I C L E I N F O Article history: Received 14 October 2009; Received in revised form 5 January 2010; Accepted 5 January 2010

Spectrophotometric Determination of Manganese with 4(5)-Imidazolealdoxime (Imalox)

Abstract A method is described for the spectrophotometric determination of manganese by means of its complex with 4(5)-imidazolealdoxime, IMALOX, formed in alkaline medium. The colour system has its absorption maximum at 350 nm and obeys Beers law over the range 0.8–8.0 μg of Mn per ml. The optimum range is 1–5 μg m−1. The molar absorptivity is 7850 1 mol−1 cm−1. Relatively few ions interfere, and these can be masked with cyanide, tartrate and NTA. The experimental results have been critically analyzed and a comparison with the main spectrophotometric reagents for manganese is presented.

Derivatives of imidazole as spectrophotometric analytical reagents

Derivatives of Imidazole as Spectrophotometric Analytical Reagents The synthesis, characteristics and metal-ion reactions of three imidazole derivatives, namely 4(5)-D-arabinotetrahydroxybutylimidazoline-2-thione (THBIT), and the oxime (IMALOX) and rhodanine (IMAR) of 4(5)-imidazolecarboxaldehyde, have been studied. IMALOX and IMAR exhibit three pK values in aqueous solution, but THBIT exhibits only one. All the reagents form stable complexes with only a small number of cations and some of them show promise as Spectrophotometric reagents.SummaryDerivatives of Imidazole as Spectrophotometric Analytical Reagents The synthesis, characteristics and metal-ion reactions of three imidazole derivatives, namely 4(5)-D-arabinotetrahydroxybutylimidazoline-2-thione (THBIT), and the oxime (IMALOX) and rhodanine (IMAR) of 4(5)-imidazolecarboxaldehyde, have been studied. IMALOX and IMAR exhibit three pK values in aqueous solution, but THBIT exhibits only one. All the reagents form stable complexes with only a small number of cations and some of them show promise as Spectrophotometric reagents.

4(5)-D-Arabinotetrahydroxybutylimidazoline-2-thione (THBIT), a new reagent for the spectrophotometric determination of palladium

Summary4(5)-D-Arabinotetrahydroxybutylimidazoline-2-thione, THBIT, is proposed as a new reagent for the spectrophotometric determination of Pd(II). Pd(II) forms 1∶1, 1∶2 and 1∶4 complexes with THBIT. The system conforms to Beers law up to 5μg/ml palladium concentration in aqueous medium (molar absorptivity, 1.99×104 l· mole−1·cm−1 at 338 nm). The most serious interference is from Hg(II), Os(VIII), Ru(IV), Cr(VI), V(V) and S2O32−. The method has been used successfully for the determination of palladium in catalysts and synthetic samples.4(5)-D-Arabinotetrahydroxybutylimidazoline-2-thione, THBIT, is proposed as a new reagent for the spectrophotometric determination of Pd(II). Pd(II) forms 1∶1, 1∶2 and 1∶4 complexes with THBIT. The system conforms to Beers law up to 5μg/ml palladium concentration in aqueous medium (molar absorptivity, 1.99×104 l· mole−1·cm−1 at 338 nm). The most serious interference is from Hg(II), Os(VIII), Ru(IV), Cr(VI), V(V) and S2O32−. The method has been used successfully for the determination of palladium in catalysts and synthetic samples.