Use of modified hydroxy-aluminum bentonites for chromium(III) removal from solutions

The retention of chromium(III) from a 2000ppm chromium basic sulfate and tannery waste solution at pH 4.5 using modified hydroxy-aluminum bentonites (OH-Al bentonites) as adsorbents was studied. OH-Al bentonite was prepared by mixing clay with a hydrolyzed commercial chlorohydroxy Al solution. The modified Al bentonites were obtained by (a) a treatment with 0.5M sodium chloride and (b) a treatment with a Na-hexametaphosphate solution (HMP) after adding sodium chloride. The effect of heating the adsorbents at 100, 500, 700 and 800 degrees C on Cr retention as a function of time was also analyzed. Cr retention by modified OH-Al bentonite with HMP increased with time (up to 100mgCr/g) where modified OH-Al bentonite was twice that of untreated bentonite. The relatively high uptake of metal from the salt solution by modified OH-Al bentonite treated at 800 degrees C, in which a complete interlayer collapse occurred, indicated the importance of the contribution of external surface sites to the retention capacity. The maximum Cr uptake from a water waste was 24mg/g, due to interferences and different chromium species in the industrial solution.     

Factors that affect the quality of the bio-waste fraction of selectively collected solid waste in Catalonia

The present study determines the composition of the bio-waste fraction of waste and establishes correlations between the quality of this fraction and socio-economic/demographic variables. According to the Catalan Waste Agency [Agència de Residus de Catalunya (2004). Statistical data. Available from: ], the quantities of glass, paper/cardboard, light packaging and biodegradable material (those components of municipal waste that can be recovered, and have a separate collection) that were selectively collected in 2004 represent 25.6% by weight of the total municipal waste generated. There is a large spread of values from different cities. It is important to bear in mind that this percentage was calculated using the total weights of all of the materials present in the different bins used for selective solid waste collection, without taking account of the fact that many of these bins contain a certain amount of other, undesirable waste. In order to be able to determine the actual quantities that are recovered, it is necessary to establish the quality of the waste collected. To establish the quality of the waste collected, 350 samples were analysed, corresponding to the bins for the bio-waste fraction of solid waste in 193 different cities in Catalonia. Seven levels of quality were established for the study, depending on the amount of undesirable waste present. The results show certain correlations between the socio-economic/demographic factors studied and the percentage of undesirable waste present in the samples. The correlations presented here are not intended to be predictive, but rather indicative of a tendency, which should help us gain a better understanding of the behaviour of the society studied with respect to the separation of solid household waste at origin.     

Effect of temperature, gas phase composition, pH and microbial activity on As, Zn, Pb and Cd mobility in selected soils in the Ebro and Meuse Basins in the context of global change

This study estimates the effect of environmental parameters on the mobility of four inorganic contaminants (As, Zn, Pb and Cd) in soils from three areas in the Ebro and Meuse River basins, within the context of global change. An experimental method, applicable to various soil systems, is used to measure the effect of four global-change-sensitive parameters (temperature, gas phase composition, pH and microbial activity). The aqueous phase of batch incubations was sampled regularly to monitor toxic element concentrations in water. Statistical processing enabled discrimination of the most relevant variations in dissolved concentrations measured at different incubation times and under different experimental conditions. Gas phase composition was identified as the most sensitive parameter for toxic element solubilization. This study confirms that total soil concentrations of inorganic pollutants are irrelevant when assessing the hazard for ecosystems or water resource quality.     

Metal availability and uptake by sorghum plants grown in soils amended with sludge from different treatments

Several factors depending on the sludge, the soil, or the combination of both substrates, may affect element availability to plants. In this study, an assessment was done of the effect of two sludges obtained by different processes (activated sludge and facultative stabilization pond) on heavy-metal availability and uptake by sorghum plants in soils with high and low copper contents. Results obtained for DTPA-extractable metal indicated higher metal availability in sludge-amended soils. In addition, sludges caused changes in copper and zinc distribution in soil, indicating in most cases a discrete increase in the more labile metal forms. However, observed changes did not increase heavy metal concentration in plant leaves, indicating that assessment of metal availability by a chemical procedure (single extraction or metal fractionation) would not permit a good prediction of metal bioavailability. On the other hand, sludge application at a rate of 100 t ha⁻¹ to high-copper agricultural soils would not imply greater mobility of this metal on account of a greater sorbing capacity provided by the sludges. Such results would indicate that sludges from wastewater treatment plants, meeting the standards of heavy metal contents, regardless of the process by which they were obtained, may be applied to several kinds of soil, even to high-copper soils, with no risk of increasing heavy metal bioavailability to phytotoxic levels in the short range.     

Electrochemical combustion of herbicide mecoprop in aqueous medium using a flow reactor with a boron-doped diamond anode

The anodic oxidation of 1.8l of solutions with mecoprop (2-(4-chloro-2-methylphenoxy)-propionic acid or MCPP) up to 0.64 g l(-1) in Na2SO4 as background electrolyte within the pH range 2.0-12.0 has been studied using a flow plant containing a one-compartment filter-press electrolytic reactor with a boron-doped diamond (BDD) anode and a stainless steel cathode, both of 20-cm2 area. Electrolyses carried out in batch under steady conditions and operating at constant current density between 50 and 150 mA cm(-2) always yield complete mineralization due to the great concentration of hydroxyl radical generated at the BDD anode. The degradation rate is practically independent of pH and Na2SO4 concentration, but it becomes faster with increasing MCPP concentration, current density, temperature and liquid flow rate. The effect of these parameters on current efficiency and energy cost has also been investigated. Generated weak oxidants such as H2O2 and peroxodisulfate ion have little influence on the mineralization process. The kinetics for the herbicide decay follows a pseudo first-order reaction with a higher rate constant when current density increases. Aromatic products such as 4-chloro-o-cresol, 2-methylhydroquinone and 2-methyl-p-benzoquinone, and generated carboxylic acids such as maleic, fumaric, lactic, pyruvic, tartronic, acetic and oxalic, have been identified as intermediates by chromatographic techniques. The initial chlorine is completely released in the form of chloride ion, which is slowly oxidized to Cl2 at the BDD anode. A reaction pathway for MCPP mineralization involving all products detected is proposed.     

Effect of pH on the aggregation of a gray humic acid in colloidal and solid states

The potential of triethylenetetramine (TETA) to inhibit the oxidation of three pyrrhotites, Garson, McCreedy and Po-97 has been studied systematically and confirmed by comparing the release of Fe and SO4(2-) from samples with and without coating treatment. Each sample, original or coated by TETA, was exposed to oxygen, 1 x 10(-3) M FeCl3, and Acidithiobacillus ferrooxidans, respectively, for specific oxidation periods. Both abiotic and biotic oxidation of samples treated by this passivating agent has been reduced significantly in this study. Under the aerobic condition, lower concentrations of ferric, total Fe or SO4(2-) were obtained from the coated samples than those from the uncoated samples. In the presence of 1 x 10(-3) M FeCl3 at 30 degrees C, TETA was able to reduce oxidation rates of Garson, McCreedy and Po-97 by 83%, 79%, and 81% (based on Fe release), respectively. A higher pH, lower Eh, and lower concentrations of total Fe and SO4(2-) were also observed in the biotic oxidation of coated Garson by Acidithiobacillus ferrooxidans. The protection of pyrrhotite surface from oxidant attack by TETA barrier and the alkaline property of this coating agent can be used to interpret the inhibition of oxidation.     

Lindane toxicity range-finding test in Senegal sole (Solea senegalensis) juvenile: note on histopathological alterations

The purpose of this study was to examine the sublethal and/or lethal effects produced by exposure of teleostean fish Solea senegalensis to γ isomer of lindane, γ-hexachlorocyclohexane (γ-HCH). S. senegalensis was exposed to 0.1, 1 or 10 mg L^?1 of lindane for 96 h. Samples of different tissues (gills, liver and kidney) were extracted and processed for histopathological observations. The 72 h LC₅₀ value of pesticide was found to be 0.16 ± 0.04 mg L^?1 γ-HCH. Histological observations including aneurysms and hypertrophy of lamellar epithelia in gills, blood stagnation and vacuolization in liver and alterations in the hematopoietic tissue in kidney were observed. The results of the study show the sensitivity of juvenile of S. senegalensis to lindane and histology as a reliable tool to detect the sublethal effects of pollutants on the environment and aquatic biota. The toxicological implications arising from these results are the subject for further multi-concentration tests useful in establishing water quality criteria.     

A proposed framework to assess upstream supply chain sustainability

There are few methods that are suitable for assessing the sustainability of companies and supply chains in an integrated way, taking into consideration the economic, social and environmental dimensions. This paper proposes a framework for assessing the sustainability of individual companies and their corresponding upstream supply chain. The framework consists of a set of steps to evaluate the sustainability of both the individual company and their upstream supply chain. The linear aggregation technique is suggested to combine the set of indicators from the economic, environmental and social dimensions of sustainability into a unique value, giving rise to a composite index for the company and corresponding supply chain. The proposed framework represents a contribution in the area of index construction and could be used as a valuable component of sustainability reporting and sustainability management practices. It also represents an important benchmarking tool, offering managers the possibility of identifying the supply chain partners that are best and worst performers in terms of sustainability while at the same time making it possible to improve company performance. Managers can adjust their company’s behaviour according to their sustainability index score and improve economic, social and environmental performance.     

Using the Framework for Integrated Sustainability Assessment (FISA) to expand the Multiregional Input–Output analysis to account for the three pillars of sustainability

Decision makers interested in promoting sustainable development must simultaneously consider the environmental, economic and social implications of any action. This article proposes the Framework for Integrated Sustainability Assessment (FISA), a methodological framework for conducting a sustainability impact assessment of any investment project. Based on a Multiregional Input–Output (MRIO) framework, FISA links the extended MRIO results with social risk data from the Social Hotspots Database (SHDB) in order to integrate the social with the environmental and economic pillars. Resulting impacts are simultaneously considered and reported by means of FISA charts, making it possible to assess the different impacts within the three sustainability pillars across countries involved in the whole supply chain of investment projects. This methodological framework can be applied not only to compare the sustainability impacts of two alternative projects, but also to derive specific recommendations aimed at minimizing the harmful social, environmental and economic effects along the whole project supply chain.     

Modelling the influence of peri-urban trees in the air quality of Madrid region (Spain)

Tropospheric ozone (O(3)) is considered one of the most important air pollutants affecting human health. The role of peri-urban vegetation in modifying O(3) concentrations has been analyzed in the Madrid region (Spain) using the V200603par-rc1 version of the CHIMERE air quality model. The 3.7 version of the MM5 meteorological model was used to provide meteorological input data to the CHIMERE. The emissions were derived from the EMEP database for 2003. Land use data and the stomatal conductance model included in CHIMERE were modified according to the latest information available for the study area. Two cases were considered for the period April-September 2003: (1) actual land use and (2) a fictitious scenario where El Pardo peri-urban forest was converted to bare-soil. The results show that El Pardo forest constitutes a sink of O(3) since removing this green area increased O(3) levels over the modified area and over down-wind surrounding areas.