Process development for recovery of copper and precious metals from waste printed circuit boards with emphasize on palladium and gold leaching and precipitation

A novel hydrometallurgical process was proposed for selective recovery of Cu, Ag, Au and Pd from waste printed circuit boards (PCBs). More than 99% of copper content was dissolved by using two consecutive sulfuric acid leaching steps in the presence of H₂O₂ as oxidizing agents. The solid residue of 2nd leaching step was treated by acidic thiourea in the presence of ferric iron as oxidizing agent and 85.76% Au and 71.36% Ag dissolution was achieved. The precipitation of Au and Ag from acidic thiourea leachate was investigated by using different amounts of sodium borohydride (SBH) as a reducing agent. The leaching of Pd and remained gold from the solid reside of 3rd leaching step was performed in NaClO-HCl-H₂O₂ leaching system and the effect of different parameters was investigated. The leaching of Pd and specially Au increased by increasing the NaClO concentration up to 10 V% and any further increasing the NaClO concentration has a negligible effect. The leaching of Pd and Au increased by increasing the HCl concentration from 2.5 to 5 M. The leaching of Pd and Au were endothermic and raising the temperature had a positive effect on leaching efficiency. The kinetics of Pd leaching was quite fast and after 30 min complete leaching of Pd was achieved, while the leaching of Au need a longer contact time. The best conditions for leaching of Pd and Au in NaClO-HCl-H₂O₂ leaching system were determined to be 5 M HCl, 1 V% H₂O₂, 10 V% NaClO at 336 K for 3 h with a solid/liquid ratio of 1/10. 100% of Pd and Au of what was in the chloride leachate were precipitated by using 2 g/L SBH. Finally, a process flow sheet for the recovery of Cu, Ag, Au and Pd from PCB was proposed.     

The effects of familiarity and gender on spatial representation

This paper reports a study of how familiarity and gender may influence the frames of reference used in memory to represent a real-world regularly shaped environment. Familiar and unfamiliar participants learned the locations of three triads of buildings by walking on a path which encircled each triad. Then they were shown with maps reproducing these triads at five different orientations (from 0° to 180°) and had to judge whether each triad represented correctly the relative positions between the buildings. Results showed that unfamiliar participants performed better when the orientation of triads was closer to the learning perspective (0° and 45°) and corresponded to front rather than to back positions. Instead, familiar participants showed a facilitation for triads oriented along orthogonal axes (0°–180°, 90°) and no difference between front and back positions. These findings suggested that locations of unfamiliar buildings were mentally represented in terms of egocentric frames of reference; instead, allocentric frames of reference defined by the environment were used when the environment was familiar. Finally, males were more accurate and faster than females, and this difference was particularly evident in participants unfamiliar with the environment.     

Mytilus galloprovincialis as bioindicator in embryotoxicity testing to evaluate sediment quality in the lagoon of Venice (Italy)

The possibility of using Mytilus galloprovincialis from natural populations of the lagoon of Venice in toxicity bioassays based on embryo development, according to international standard methods, was investigated. In order to valuate this method for the lagoon, iterative steps including evaluation of reproducibility, sensitivity and discriminatory capacity towards some pure substances and environmental samples were performed. Evaluation of sensitivity towards a reference toxicant (copper) evidenced good replicability and repeatability. Results showed that natural population is better than hatchery population for performing bioassays. Evaluation of applicability to elutriates revealed that the method is able to discriminate among sediments of the lagoon of Venice at different typologies and levels of contamination, showing an important effect for almost all study sites.     

Screening of POP pollution by AChE and EROD activities in Zebra mussels from the Italian Great Lakes

The increase of ethoxyresorufin dealkylation (EROD) and the inhibition of acetylcholinesterase (AChE) as biomarkers have been commonly used in vertebrates for the persistent organic pollutants (POPs) biomonitoring of aquatic environments, but very few studies have been performed for invertebrates. Previous researches demonstrated the interference due to some chemicals on EROD and AChE activities of the freshwater bivalve Zebra mussel (Dreissena polymorpha) in laboratory and field studies, showing its possible use for the screening of POP effects. We investigated the contamination of the Italian sub-alpine great lakes (Maggiore, Lugano, Como, Iseo, Garda) by the biomarker approach on Zebra mussel specimens collected at 17 sampling sites with different morphometric characteristics and anthropization levels. Results showed a homogeneous contamination of AChE inhibitors in Lake Garda, Maggiore, Como and Iseo with values ranging from 0.5 to 3 nmol/min/mg proteins and with an average inhibition of about 66% to controls. The planar compounds pollution, able to activate the EROD activity, seems higher in some sampling stations of Lake Garda, Como and Iseo (2-4 pmol/min/mg proteins) than that measured in Lake Lugano (1.5-3 pmol/min/mg proteins). On the contrary, the enzyme activity in Lake Maggiore showed an interesting opposite effect of AhR-binding compounds and trace metals. Finally, the possible use of Zebra mussel specimens maintained at laboratory conditions as controls against the selection of the less polluted sampling site is discussed.     

An Eco-balance of a Recycling Plant for Spent Lead–Acid Batteries

This study applies Life Cycle Assessment (LCA) methodology to present an eco-balance of a recycling plant that treats spent lead–acid batteries. The recycling plant uses pyrometallurgical treatment to obtain lead from spent batteries. The application of LCA methodology (ISO 14040 series) enabled us to assess the potential environmental impacts arising from the recycling plants operations. Thus, net emissions of greenhouse gases as well as other major environmental consequences were examined and hot spots inside the recycling plant were identified. A sensitivity analysis was also performed on certain variables to evaluate their effect on the LCA study. The LCA of a recycling plant for spent lead–acid batteries presented shows that this methodology allows all of the major environmental consequences associated with lead recycling using the pyrometallurgical process to be examined. The study highlights areas in which environmental improvements are easily achievable by a business, providing a basis for suggestions to minimize the environmental impact of its production phases, improving process and company performance in environmental terms.     

Variation in biometry and population density of solitary corals with solar radiation and sea surface temperature in the Mediterranean Sea

The correlation between two environmental factors (solar radiation and sea surface temperature), biometry, and population density was assessed along a latitudinal gradient in the zooxanthellate coral Balanophyllia europaea and in the azooxanthellate coral Leptopsammia pruvoti. With increasing polyp size, the oral disc of B. europaea assumed an oval shape, while that of L. pruvoti retained a circular shape. In both species, biometric parameters varied more with temperature than with solar radiation. In the zooxanthellate species, temperature explained a higher percentage of biometric parameter variance than in the azooxanthellate species. While environmental factors did not co-vary with demographic characteristics in L. pruvoti, temperature was negatively related to the population density of B. europaea. It is hypothesized that the negative effect of temperature on biometry and population density of B. europaea depends on photosynthesis inhibition of symbiotic zooxanthellae at high temperatures, which would lower the calcification rate and availability of energetic resources.     

Erratum to: Patterns of spatial variability of seagrass epiphytes in the north-west Mediterranean Sea

This study aimed to gain insight on patterns of spatial variability of seagrass epiphytes of both leaves and of rhizomes in three different habitats, continental coasts, offshore banks and islands. Moreover, we tried to discriminate between habitat-dependant variability and scale-dependant variability of Posidonia oceanica epiphytic assemblages. Results showed the absence of significant differences in the structure of assemblages of epiphytes both on leaves and on rhizomes among continental coasts, offshore banks and islands, even if the patterns of spatial variability changed among habitats. In fact, although a high variability at small scales appeared a constant pattern in epiphytic assemblages, large-scale variability resulted higher in continental coasts and offshore banks than in islands. In conclusion, epiphytic assemblages of Posidonia oceanica appear homogeneous among habitats, showing a similar structure and species composition in the same geographic area. On the contrary, differences between meadows appeared linked to local differences in environmental factors that are more evident in habitats influenced by human disturbance. An erratum to this article can be found at     

Scaling parameters for vented gas and dust explosions

Results of experiments or calculations for vented explosions are usually presented by expressing a term containing the peak (reduced) pressure as a function of a vent parameter. In gas explosions, the reactivity of the system has been typically characterized through an effective burning velocity, u_f. In the case of dust explosions, a normalized peak rate of pressure rise, K(=V^1/3(dp/dt)_max), has been used instead. Depending on the chosen approach, comparisons between systems with the same “reactivity” take different meanings. In fact, correlation formulas resulting from these two approaches imply different scaling between important system parameters. In the case of a constant-u_f system, and for sufficiently large vent areas, the reduced pressure, Δp_r, is approximately proportional to the square of the peak unvented pressure, Δp_m. On the other hand, correlations developed for constant-K systems imply proportionality of Δp_r with Δp_m raised to a power between −5/3 and −1, with the exact value depending on the assumptions made on the shape of the pressure profile. While the ultimate resolution of the details of the scaling may require recourse to experiments, this theoretical analysis offers a tool for the planning of such experiments and for the interpretation of their results. The paper provides a discussion of these scaling issues with the help of predictions from an isothermal model of vented explosions.     

Workshop report on the extraction of foetal DNA from maternal plasma

Objective Cell free foetal DNA (cff DNA) extracted from maternal plasma is now recognized as a potential source for prenatal diagnosis but the methodology is currently not well standardized. To evaluate different manual and automated DNA extraction methods with a view to developing standards, an International Workshop was performed. Methods Three plasma pools from RhD-negative pregnant women, a DNA standard, real-time-PCR protocol, primers and probes for RHD were sent to 12 laboratories and also to one company (Qiagen, Hilden, Germany). In pre-tests, pool 3 showed a low cff DNA concentration, pool 1 showed a higher concentration and pool 2 an intermediate concentration. Results The QIAamp DSP Virus Kit, the High Pure PCR Template Preparation Kit, an in-house protocol using the QIAamp DNA Blood Mini Kit, the CST genomic DNA purification kit, the Magna Pure LC, the MDx, the M48, the EZ1 and an in-house protocol using magnetic beads for manual and automated extraction were the methods that were able to reliably detect foetal RHD. The best results were obtained with the QIAamp DSP Virus Kit. The QIAamp DNA Blood Mini Kit showed very comparable results in laboratories that followed the manufacturer's protocol and started with ≥ 500 µL plasma. One participant using the QIAamp DNA Blood Midi Kit failed to detect reliably RHD in pool 3. Conclusions This workshop initiated a standardization process for extraction of cff DNA in maternal plasma. The highest yield was obtained by the QIAamp DSP Virus Kit, a result that will be evaluated in more detail in future studies. Copyright © 2007 John Wiley & Sons, Ltd.