Removal of heavy metals and cyanide from gold mine wastewater

This paper reviews the technology and biotechnology to remove heavy metals (such as copper, arsenic, lead and zinc) and cyanide from contaminated wastewater. The paper places special emphasis on gold mine wastewater and the use of low cost materials as sorbent. Various biological as well as physicochemical treatment processes are discussed and compared on the basis of costs, energy requirement, removal efficiency, limitations and advantages. Sorption using natural plant materials, industrial and agricultural waste has been demonstrated to have the potential to replace conventional methods for the removal of heavy metals because of its cost effectiveness, efficiency and the local availability of these materials as biosorbent. The parameters affecting sorption, such as initial ion concentration, pH, sorbent dosage, particle size and temperature, are discussed. The overall treatment cost of metal and cyanide contaminated wastewater depends on the process employed and the local conditions. In general, technical applicability, cost‐effectiveness and plant simplicity are the key factors in selecting the most suitable treatment method. Copyright © 2010 Society of Chemical Industry     

The effect of phosphorus on the HDN reaction of piperidine,decahydroquinoline and ortho-propylaniline over Ni-MoS2/Al2O3 catalysts

The hydrodenitrogenation (HDN) of piperidine, decahydroquinoline (DHQ) and orthopropylaniline (OPA) has been studied over NiMo(P)/Al₂O₃ catalysts at 593 K and 3.0 MPa in order to understand the effect of phosphorus on the elementary HDN reaction steps. Phosphorus exhibited a negative effect on the HDN of piperidine and DHQ, both on the C-N bond cleavage reaction and on the subsequent hydrogenation reaction of alkene to alkane. A P/Al₂O₃ catalyst showed no HDN activity at all, neither with piperidine, nor with DHQ. A positive effect of phosphorus was observed in the HDN of OPA, where hydrogenation of the aromatic ring is needed and is rate limiting. It is suggested that introduction of phosphorus to NiMo/Al₂O₃ catalysts on the one hand decreases the available support surface area, and as a consequence the dispersion of the Ni-Mo-S phase and thus the capacity for C-N bond breaking and olefin hydrogenation. On the other hand, phosphorus induces either new or more active sites for the hydrogenation of aromatics.     

The effect of pretreatment on the reactivity of Fe-ZSM-5 catalysts for N2O decomposition: Dehydroxylation vs. steaming

The N₂O decomposition activity of the Fe-ZSM-5 catalysts, prepared by chemical vapor deposition (CVD) and aqueous ion exchange (IE), was studied after steaming and high temperature treatment at 1218 K (HT) and compared with the activity of the corresponding non-steamed catalysts after pretreatment at 873 K. FTIR spectra showed that dehydroxylation and/or dealumination took place during steaming and high temperature treatment of the catalysts, which leads to the formation of oxygen vacancies (i.e. lattice defect). These lattice defects leads to a change in electronic properties of the iron sites, which are associated with electron withdrawing Al Lewis centers. The iron sites in close proximity of defects are responsible for the initial higher N₂O decomposition (transient activity) of the steamed and HT catalysts. The increase in steady-state activity over steamed and HT catalysts can be mainly attributed to an increase in the number of active sites created by autoreduction of the iron centers during steaming and high temperature treatment. The above-mentioned trends are valid for both CVD and IE samples.     

Automated 3-D PDM construction from segmented images using deformable models

In recent years, several methods have been proposed for constructing statistical shape models to aid image analysis tasks by providing a priori knowledge. Examples include principal component analysis of manually or semiautomatically placed corresponding landmarks on the learning shapes [point distribution models (PDMs)], which is time consuming and subjective. However, automatically establishing surface correspondences continues to be a difficult problem. This paper presents a novel method for the automated construction of three-dimensional PDM from segmented images. Corresponding surface landmarks are established by adapting a triangulated learning shape to segmented volumetric images of the remaining shapes. The adaptation is based on a novel deformable model technique. We illustrate our approach using computed tomography data of the vertebra and the femur. We demonstrate that our method accurately represents and predicts shapes.     

A2thOS: availability analysis and optimisation in SLAs

Information technology (IT) service availability is at the core of customer satisfaction and business success for today's organisations. Many medium‐ to large‐size organisations outsource part of their IT services to external providers, with service‐level agreements describing the agreed availability of outsourced service components. Availability management of partially outsourced IT services is a non‐trivial task since classic approaches for calculating availability are not applicable, and IT managers can only rely on their expertise to fulfil it. This often leads to the adoption of non‐optimal solutions. In this paper we present A ²thOS , a framework to calculate the availability of partially outsourced IT services in the presence of SLAs and to achieve a cost‐optimal choice of availability levels for outsourced IT components while guaranteeing a target availability level for the service. Copyright © 2011 John Wiley & Sons, Ltd.     

Metal complexation properties of freshwater dissolved organic matter are explained by its aromaticity and by anthropogenic ligands

Dissolved organic matter (DOM) in surface waters affects the fate and environmental effects of trace metals. We measured variability in the Cd, Cu, Ni, and Zn affinity of 23 DOM samples isolated by reverse osmosis from freshwaters in natural, agricultural, and urban areas. Affinities at uniform pH and ionic composition were assayed at low, environmentally relevant free Cd, Cu, Ni, and Zn activities. The C-normalized metal binding of DOM varied 4-fold (Cu) or about 10-fold (Cd, Ni, Zn) among samples. The dissolved organic carbon concentration ranged only 9-fold in the waters, illustrating that DOM quality is an equally important parameter for metal complexation as DOM quantity. The UV-absorbance of DOM explained metal affinity only for waters receiving few urban inputs, indicating that in those waters, aromatic humic substances are the dominant metal chelators. Larger metal affinities were found for DOM from waters with urban inputs. Aminopolycarboxylate ligands (mainly EDTA) were detected at concentrations up to 0.14 μM and partly explained the larger metal affinity. Nickel concentrations in these surface waters are strongly related to EDTA concentrations (R2=0.96) and this is underpinned by speciation calculations. It is concluded that metal complexation in waters with anthropogenic discharges is larger than that estimated with models that only take into account binding on humic substances.     

The copper-mobilizing-potential of dissolved organic matter in soils varies 10-fold depending on soil incubation and extraction procedures

Copper is mobilized in soil by dissolved organic matter (DOM) but the role of DOM quality in this process is unclear. A one-step resin-exchange method was developed to measure the Cu-Mobilizing-Potential (CuMP) of DOM at pCu 11.3 and pH 7.0, representing background values. The CuMP of DOM was measured in soil solutions of 13 uncontaminated soils with different DOM extraction methods. The CuMP, expressed per unit dissolved organic carbon (DOC), varied 10-fold and followed the order water extracts > 0.01 M CaCl2 extracts > pore water. Soil solutions, obtained from soils that were stored air-dry for a long time or were subjected to drying-wetting cycles, had elevated DOC concentration, but the DOM had a low CuMP. Prolonged soil incubations decreased the DOC concentration and increased the CuMP, suggesting that most of the initially elevated DOM is less humified and has lower Cu affinity than DOM remaining after incubation. A significant positive correlation between the specific UV-absorption of DOM (indicating aromaticity) and CuMP was found for all DOM samples (R(2) = 0.58). It is concluded that the DOC concentration in soil is an insufficient predictor for the Cu mobilization and that DOM samples isolated from air-dried soils are distinct from those of soils kept moist.     

Ethanol's energy return on investment: a survey of the literature 1990-present

Various authors have reported conflicting values for the energy return on investment (rE) of ethanol manufacture. Energy policy analysts predisposed to or against ethanol frequently cite selections from these studies to supporttheir positions. This literature review takes an objective look at the disagreement by normalizing and comparing the data sets from ten such studies. Six of the reviewed studies treat starch ethanol from corn, and four treat cellulosic ethanol. Each normalized data set is also submitted to a uniform calculation of rEdefined as the total product energy divided by nonrenewable energy input to its manufacture. Defined this way rE > 1 indicates that the ethanol product has nominally captured at least some renewable energy, and rE > 0.76 indicates that it consumes less nonrenewable energy in its manufacture than gasoline. The reviewed corn ethanol studies imply 0.84 < or = rE < or = 1.65; three of the cellulosic ethanol studies imply 4.40 < or = rE < or = 6.61. The fourth cellulosic ethanol study reports rE= 0.69 and may reasonably be considered an outlier.