Physical and chemical processing of printed circuit boards waste

A recycling process for PCB’s is being studied, based on physical processing and hydrometallurgical treatment. PCB’s waste was shredded in a lab cutting mill, resulting a grinded material with 90% (weight) with particle size less than 2.1 mm and an average particle diameter of 1.2 mm. Chemical analysis of granulometric fractions showed that the base metals like Cu, Zn, Pb and Sn concentrated mainly in intermediate size fractions (0.4-1.7 mm) being fines very rich in epoxy resin composite. About 80-90% of the principal metals were recovered in that size range. The first step of chemical treatment was the acid leaching of metals. The use of nitric acid solutions at appropriate conditions allowed the efficient solubilization of base metals like Cu, Ni, Zn, Pb and Ag. More than 90% recovery of Cu, Zn and Ni were achieved at 90ºC using 1 M HNO3. Dissolution of silver required higher concentrations (only 70% yield using 2 M HNO3). Tin leaching was inefficient in nitric media, being always lower than 20%. The leaching conditions here reported were adequate to the base metals solubilization, allowing further processing of leachates for separation and recovery using hydrometallurgical operations. Precious metals recovery would be attained in a subsequent leaching step using highly concentrated acidic solutions

Leaching studies for metals recovery from printed circuit boards scrap

In this paper, the leaching behavior of the major metals present in printed circuit boards waste is evaluated, aiming at its recycling by hydrometallurgy. Several leachants were compared (sulfuric, hydrochloric and nitric acids, at 2 M H+ concentration), at temperatures of 25ºC and 90ºC and 4 hours of reaction time. Sulfuric acid leaching was not very promising concerning metals dissolution being only effective for iron. Hydrochloric acid allowed the leaching up to 60% of tin and about 50% of lead, as well as the iron. Nitric acid was the most efficient leachant due to its oxidizing properties. Recoveries of 90% or more for copper, iron, nickel and zinc were achieved at the higher temperature. Lead was also dissolved (up to 80%), as well as silver (more than 70%). These results show that the hydrometallurgical recovery of most of the metals present in PCB’s scrap is a technically feasible alternative that shall be considered and evaluated

Form invariance symmetry generates a large set of FRW cosmologies

We show that Einstein's field equations for spatially flat Friedmann-Robertson-Walker (FRW) space times have a form invariance symmetry (FIS) realized by the form invariance transformations (FIT) which are indeed generated by an invertible function of the source energy density. These transformations act on the Hubble expansion rate, the energy density, and pressure of the cosmic fluid; likewise such transformations are endowed with a Lie group structure. Each representation of this group is associated with a particular fluid and consequently a determined cosmology, so that, the FIS defines a set of equivalent cosmological models. We focus our seek in the FIT generated by a linear function because it provides a natural framework to express the duality and also produces a large sets of cosmologies, starting from a seed one, in several contexts as for instance in the cases of a perfect fluid source and a scalar field driven by a potential depending linearly on the scalar field kinetic energy density.Comment: 11 pages, 3 figures. Accepted for publication in Modern Physics Letters A (2012

Subacute combined degeneration of the cord secondary to nitrous oxide misuse:No laughing matter

Nitrous oxide (N(2)O) has several traditional uses as a surgical and dental anaesthetic, as well as in aerosol spray propellants. It is the combination of analgesic and euphoric qualities coupled with accessibility as an over-the-counter household item that lends N(2)O to recreational use. Despite increasing evidence that prolonged use of N(2)O both medically and as a drug of abuse can cause disabling neurological side-effects, it remains widely used. We present the case of an 18-year-old male who was diagnosed with subacute combined degeneration of the cord (SCDC) secondary to acute, heavy recreational use of N(2)O. The patient presented with progressive paraesthesia affecting his hands and feet associated with distal weakness. MRI of the cervical spine revealed symmetric bilateral high T2 signal within the dorsal columns extending from the level of C2 to T2 with the inverted ‘V’ sign on axial T(2)-weighted slices indicative of SCDC. Although vitamin B12 levels were within normal range, marked elevation of methylmalonic acid and homocysteine support the diagnosis of B12 inactivation and functional B12 deficiency, which fully resolved with treatment

Stormwater Contaminant Load Monitoring (2016) and Modelling of the Heathcote Catchment and Six Representative Subcatchments

Adverse effects from sediment and heavy metals have been observed in the Heathcote catchment, which is diverse in its land use activities. Stormwater management improvements are planned for the catchment through the Heathcote Stormwater Management Plan. Contaminant load monitoring and modelling for subcatchments in the Heathcote were undertaken to help inform the stormwater management policies and planning. The UC’s event-based contaminant load model, MEDUSA (Modelled Estimates of Discharges for Urban Stormwater Assessments), that predicts the amount of total suspended solids (TSS), and total and dissolved copper and zinc generated by individual roof, road and carpark surfaces, was employed for the modelling. Stormwater monitoring of key impermeable surfaces was used to calibrate the model and also quantify the chemical speciation of the contaminants (i.e. particulate or dissolved form), important for assessing appropriate future treatment or mitigation strategies. Stormwater runoff monitoring and predictive modelling (using MEDUSA) was previously conducted in the Okeover and Addington subcatchments of the Avon Catchment. In those studies, four roof types, three road types and three carpark classifications were monitored and modelled. In this study, stormwater runoff quality was monitored from eight different impermeable surfaces in the Heathcote catchment over 9 rainfall events from July to November 2016. These sites represented typical surfaces in the catchment: a new Coloursteel® roof, an older Coloursteel® roof, a concrete roof, a galvanized painted roof, three roads (local, collector, minor arterial) and a commercial/light industrial carpark. First flush (first 1 L of runoff) and steady state samples were analysed for TSS and total and dissolved zinc and copper. Data from the monitoring campaign was analyzed and then used to refine MEDUSA to Heathcote conditions. The model was applied to estimate zinc loads from roofs for the Heathcote catchment as a whole, as well as from six individual subcatchments representing industrial areas (Curries and Jardens Drains; Awatea), mixed use areas (Curletts Drain; Waltham) and mostly residential areas (Jacksons Creek; Wilderness Drain). Predictions of contaminant loads were obtained for each rainfall event sampled in 2016. Additionally, predictive simulations were conducted for all events for years between 2011-2016 to ascertain differences as a function of variable weather conditions. The galvanized roof surfaces produced significantly more zinc than other surfaces. Coloursteel® Old and Galvanised Painted first flush runoff contributed some of the highest zinc concentrations measured in recent Christchurch untreated stormwater sampling. First flush concentrations from the new Coloursteel® roof were consistently lower than the steady state concentrations from the old Coloursteel® roof. Similarly, zinc concentrations from the galvanised painted roof were higher than the new Coloursteel® roof, but lower than the old Coloursteel® roof. The data also clearly show that the majority of zinc from the four roof types is in the dissolved form, substantiating previous monitored data in Christchurch. These data confirm that the key mechanism for zinc generation from roofs is direct dissolution of the roof material, enhanced and sustained by the exposure and breakdown of the galvanizing layer through weathering. Zinc measured in concrete roof runoff is believed to originate from galvanised components in the guttering and downpipes rather than from atmospheric deposition alone. Therefore, while concrete and other non-metallic roofs may not contribute large zinc loads to stormwater runoff, some zinc is dissolved from their galvanised drainage components, which may be something to consider in management decisions about roof replacements along with roof condition. Because zinc was defined as the focus of the study, total zinc loads were predicted using MEDUSA. Modelling results revealed that there is a clear difference in the rate at which total zinc is derived from each roof type, with concrete and Coloursteel® roofs yielding the least amount of zinc (per area) in roof runoff. Zincalume® and painted Galvanised roofs released more than double the amount (per area) of concrete and Coloursteel® roofs, but not as much as unpainted galvanised roofs. The data highlight the availability of zinc from roofs (with metallic surfaces) to stormwater runoff and the positive effect of painting these surfaces to immobilize some of the zinc. The yearly scenario results reveal the influence of variable wet weather conditions (including rainfall pH, antecedent dry days, rainfall intensity and duration) on zinc runoff from roofs. Despite the relatively low proportion (7 %) of roofs within the Heathcote Catchment that are defined as poorly painted or unpainted, they consistently contribute more than 30 % of the total zinc load from roofs in each year. Waltham (mixed landuse) roofs, which make up 29 % of the catchment and comprise the highest proportion (16 ha) of unpainted galvanized roofs, contribute between 2.2 and 7.6 net kg TZn/event to stormwater runoff. Similarly, Wilderness Drain (residential landuse) roofs, which make up 26 % of the catchment and comprise 12 ha of unpainted galvanized roofs, 34 ha of painted galvanized roofs and 27 ha of Coloursteel® roofs, produces nearly the same net zinc loads (2.0 -7.9 TZn kg) per rain event as Waltham. These disaggregated data are important because they highlight that the proportional area of specific roof types (e.g. unpainted galvanized) is a clear determinant of how much total zinc can be expected in roof runoff rather than assuming greater contributions from a more industrial/commercial area alone. Furthermore, depending on the condition of that roof material, a range of lower or higher zinc loads can be expected from roof runoff during rain events. Changes (as modelled scenarios) in proportional roof areas from the current status would result in significant reductions of total zinc runoff from roofs in the Heathcote subcatchments across all the modelled years, with some variability between years due to the influence of rainfall parameters. This reduction is more pronounced at the higher ranges for each scenario. A change in proportional zinc loads in different subcatchments results from the change in their proportional areas (and condition), highlighting the value in examining specific subcatchment responses to variable modelling scenarios

Influence of groundwater condition on nutrient dynamics in urban waterways

Excess nutrients in waterways contribute to eutrophication and decrease aquatic ecosystem health, a problem affecting both rural and urban catchments. In order to address excess nutrient problems in urban waterways, authorities have been developing strategies to mitigate impacts by using in-channel and landbased stormwater treatment to remove pollutants via settling and other physical, chemical and/or biological processes. However, little is known about how pollutants are transported and transformed in urban in-channel systems under the influence of different groundwater conditions. Therefore, this research aims to understand nutrient dynamics (nitrogen and phosphorus) in waterway channels under the influence of seepage, neutral, and drainage conditions. It was hypothesized that groundwater and bed material characteristics affect the concentration and form of surface pollutants, as well as their mobility. This understanding could help guide stream management decisions

Generation Y and sparkling wines: a cross-cultural perspective

The aim of this study was to investigate and compare the engagement of Generation Y consumers with champagne and sparkling wine across five Anglophone countries. A qualitative approach was adopted using focus groups with young consumers, including images and wine tasting as projective stimuli. There were significant trans-cultural similarities between consumption behaviour (sparkling wine is a women’s drink, and a separate category from still wine, and that they will ‘grow into’ drinking it) but also noticeable differences (responses to images and colours varied substantially, as did attitudes to price and the particular status of champagne). Research into the behaviour of Generation Y as a cohort needs to take account of cultural as much as generational context. However, as a qualitative study the findings need further quantitative validation. Marketers cannot view Generation Y as a single group; even within countries marketing strategies may need to be refined depending on where a product is being sold

Comparison of engagement and emotional responses of older and younger adults interacting with 3D cultural heritage artefacts on personal devices

The availability of advanced software and less expensive hardware allows museums to preserve and share artefacts digitally. As a result, museums are frequently making their collections accessible online as interactive, 3D models. This could lead to the unique situation of viewing the digital artefact before the physical artefact. Experiencing artefacts digitally outside of the museum on personal devices may affect the user's ability to emotionally connect to the artefacts. This study examines how two target populations of young adults (18–21 years) and the elderly (65 years and older) responded to seeing cultural heritage artefacts in three different modalities: augmented reality on a tablet, 3D models on a laptop, and then physical artefacts. Specifically, the time spent, enjoyment, and emotional responses were analysed. Results revealed that regardless of age, the digital modalities were enjoyable and encouraged emotional responses. Seeing the physical artefacts after the digital ones did not lessen their enjoyment or emotions felt. These findings aim to provide an insight into the effectiveness of 3D artefacts viewed on personal devices and artefacts shown outside of the museum for encouraging emotional responses from older and younger people

The folding of knotted proteins: insights from lattice simulations

We carry out systematic Monte Carlo simulations of Go lattice proteins to investigate and compare the folding processes of two model proteins whose native structures differ from each other due to the presence of a trefoil knot located near the terminus of one of the protein chains. We show that the folding time of the knotted fold is larger than that of the unknotted protein and that this difference in folding time is particularly striking in the temperature region below the optimal folding temperature. Both proteins display similar folding transition temperatures, which is indicative of similar thermal stabilities. By using the folding probability reaction coordinate as an estimator of folding progression we have found out that the formation of the knot is mainly a late folding event in our shallow knot system