The use of electrolyte redox potential to monitor the Ce(IV)/Ce(III) couple

Mathematical modelling of the oxidation reduction redox potential (ORP) of an electrolyte has been carried out for a batch system comprising an electrochemical reactor and an electrolyte circuit containing a redox couple. The ORP can be useful to monitor the environmental impact of chemical species in solution that represent a risk to the environment. Considerations of four fundamental equations, namely, the Nernst equation, a mass balance, Faraday's laws of electrolysis and a first order kinetic equation, leads to an expression for the electrolyte redox potential as a function of the batch time, the electrical charge and the redox concentration. Such an expression facilitates graphical plots which can be used to estimate kinetic parameters, current efficiency and the relative redox concentration. The Ce(IV)/Ce(III) system has been chosen as a model reaction for electrolyte redox potential measurement in a batch recycle system consisting of a pumped flow through a divided FM01-LC parallel-plate electrochemical reactor (64cm(2) projected electrode area) and a well mixed tank (3600cm(3)). The differences between experimental and model predictions are discussed.     

A Systematic Framework for the Design and Implementation of a Quality Management Practice: The Case of a Consulting Engineering Company

Company productivity and competitiveness in today's marketplace requires creative design, innovation, and the reduction of nonconformances, which require costly rework and can damage a firm's reputation with its customers and potential customers. Using the International Organisation of Standardization's (ISO) 9000 and 14000 series of standards, the authors of this article walk readers through the rigorous process of obtaining upper management buy‐in and sponsorship and engaging workers in a bottom‐up approach to establish the procedures necessary to perform world‐class engineering services.     

Natural attenuation of residual heavy metal contamination in soils affected by the Aznalcóllar mine spill, SW Spain

Non-amended soils affected by pyritic sludge residues were monitored for 7 years to assess the long-term natural attenuation ability of these soils. The decrease in both the total concentration of elements (particularly As) and (NH(4))(2)SO(4)-extractable fractions of Mn, and Zn, below the maximum permissible levels indicate a successful natural ability to attenuate soil pollution. Soil acidification by pyrite oxidation and rainfall-enhanced leaching were the largest contributors to the reduction of metals of high (Mn, Cu, Zn and Cd) and low (Fe, Al, and As) availability. Periodic use of correlation and spatial distribution analysis was useful in monitoring elemental dispersion and soil property/element relationships.     

Associations between forest characteristics and socio-economic development: a case study from Portugal

The integration of socio-economic and environmental objectives is a major challenge in developing strategies for sustainable landscapes. We investigated associations between socio-economic variables, landscape metrics and measures of forest condition in the context of Portugal. The main goals of the study were to 1) investigate relationships between forest conditions and measures of socio-economic development at national and regional scales, 2) test the hypothesis that a systematic variation in forest landscape metrics occurs according to the stage of socio-economic development and, 3) assess the extent to which landscape metrics can inform strategies to enhance forest sustainability. A ranking approach and statistical techniques such as Principal Component Analysis were used to achieve these objectives. Relationships between socio-economic characteristics, landscape metrics and measures of forest condition were only significant in the regional analysis of municipalities in Northern Portugal. Landscape metrics for different tree species displayed significant variations across socio-economic groups of municipalities and these differences were consistent with changes in characteristics suggested by the forest transition model. The use of metrics also helped inform place-specific strategies to improve forest management, though it was also apparent that further work was required to better incorporate differences in forest functions into sustainability planning.     

Water management in the world of globalization

Water management is changing its paradigm. The millennia of economic indoctrination are to be replaced by the logic of ecology. The economic sector satisfying the demands for water and water‐related services guided until now by its own ideology and institutions, is gradually becoming an integral part of environmental protection and eco‐economy. Within the great diversity of national water policies, efforts towards sustainability are a dominant common objective. Discussions of the World Water Fora and other initiatives indicate that ecologically oriented water management is the emerging new challenge for achieving this objective. Ecological orientation emphasizes the unified system of the world water balance processes as transmitters of various human impacts leading to economic externalities. Water management is becoming a component of the processes of globalization primarily through its externalities requiring a comprehensive informational infrastructure as well as adequate institutional competence for their management. The paper analyzes fundamental features of the conceptual models incorporating such informational and institutional arrangements. The outlook of water is inseparably tied to the world order of the future, and water management in the world of globalization can either promote a genuine worldwide collaboration or can become a source of dangerous international tensions and conflicts.     

Biodegradation of LDPE/Modified Starch Blends Sterilized with Gamma Radiation

Blends of LDPE/modified starch were prepared, sterilized by gamma radiation and investigated with respect to their microbial degradation by a mixture of fungal strains in liquid medium after 90 days, was analyzed by carbon dioxide (CO₂) production (Sturm test). Biodegradation of blends was evaluated by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction; mechanical testing, scanning electron microscopy (SEM). The biodegradation of LDPE/modified starch blends was attributed to microbiological attack, with alterations in the chemical structure of the blend with an increase in the carbonyl and vinyl indices and the appearance of new crystalline symmetry generating a crystalline domain not existing before in the blend and decrease in the mechanical properties.     

Effect of contact time on the release of contaminants from granular waste materials during column leaching experiments

When reusing or disposing of contaminated granular waste materials there is a need to evaluate how the contaminants will interact on the pathway soil–groundwater and the effect this interaction will have on the surrounding environment. While column testing can provide a closer approximation to field percolation conditions than batch testing, there is still a need to develop column testing procedures that consider the requirements of practical testing time frames. This study evaluates the effect of different column contact times (2.5, 5, and 16 h) on the release of inorganic constituents from bottom ash and demolition waste, two commonly reused granular materials. Leaching data for representative constituents of concern, such as copper, chromium, sulfate and chloride, as well as pH and electrical conductivity was compared for all different contact times studied.Results for the materials investigated in this study showed that variations in contact time have no significant effect on the release of the selected constituents and leaching parameters at low liquid to solid ratios. However, after a liquid to solid ratio of 1 L/kg, the effect is more noticeable, and higher contact times show lower pH values as well as a reduction in the release of constituents of concern from bottom ash. In the case of demolition waste, the variation of contact time did not have a strong effect on the leaching behavior.     

Natural materials for treatment of industrial effluents: comparative study of the retention of Cd, Zn and Co by calcite and hydroxyapatite. Part I: batch experiments

This work explores the heavy metal retention capacity of materials developed from minerals that are abundant in nature, with low cost and minimum environmental impact. To accomplish this objective we have: (a) characterized commercial samples of calcite (CA) and hydroxyapatite (HAP)--including their surface properties (BET area, electrophoretic mobility, SEM, and X-ray energy dispersive spectroscopy); and, (b) qualified and quantified the interaction of Cd, Zn and Co with calcite (CaCO3) and hydroxyapatite [Ca5(PO4)3OH] through batch experiments, in a range of metal concentrations (4Zn>Co and Cd>Zn approximately Co, respectively. Retention increased with pCa and pH and could be modeled by: (a) a non-ideal ion exchange mechanism (Me/Ca) for the adsorption of Cd, Zn and Co onto CA; and, (b) a mechanism of non-ideal ion exchange and specific adsorption (Me/Ca and identical with PO4O-Me) in the case of HAP. The pH dependence is indirect in CA and is related to its solubility changes (pCa increases with pH, and so does sorption of Cd, Zn and Co). Both materials, HAP and CA, can be used for heavy metal retention. The former has better performance for water treatment due to its greater efficiency for the retention of Cd, Zn and Co (over two orders of magnitude per gram of material) and its lower solubility in a wide range of pH (6相似文献