Characterization of industrially pre-treated waste printed circuit boards for the potential recovery of rare earth elements

Rare earth elements (REE) are classified as critical raw materials and the environmental impact of mining them is of growing concern. The recovery of REE from electronic waste (e-waste) could offer a more sustainable practice. Waste printed circuit boards (WPCBs) are an important resource in the e-waste stream due to their content of valuable materials. However, data regarding the concentration and distribution of REE in WPCBs is very limited. The aims of this research were: (a) to analyse the chemical composition of comminuted WPCBs prior to processing (industrially pre-treated) with emphasis on REE, and (b) to determine the distribution of REE and other metals in different size fractions of the pre-treated WPCBs. The samples were supplied by commercial e-waste recycling companies, which makes them representative of the e-waste processing industry in the UK. Correlation between elemental concentrations and particle size was analysed using Spearman’s rank correlation. Most REE concentrations were inversely correlated to the particle size. Concentrations of Y, La and Gd were found up to a thousand times higher in the smaller particle size compared with coarser particles. However, most of base metals including Cu, Sn, Pb and Zn did not show this trend. The present study highlights the occurrence of REE in comminuted WPCBs, and fine fractions as potential sources of these critical elements, currently not recovered during recycling process. A cost-effective sieving step is proposed to enrich the REE content for further recovery, prevent the possible loss of REE and maximize the total material recovered from WPCBs

Characterisation of “flushable” and “non-flushable” commercial wet wipes using microRaman, FTIR spectroscopy and fluorescence microscopy: to flush or not to flush

The introduction to the market of wet wipes, advertised and labelled as “flushable”, has been the subject of controversy due to their perceived potential to block sewer systems as observed with other non-woven cloths such as traditional non-flushable wipes. Non-woven cloths that enter wastewater systems can find their way into the aquatic environment via wastewater effluents and it has been suggested that the breakdown of these fabrics can release materials such as microplastics into the environment. Worldwide research has revealed the alarming number of aquatic organisms affected by the presence of plastic debris in the aquatic environment harbouring a potential risk to humans through the introduction of microplastics into the food chains. However, the actual material composition of flushable wipes, their fate and impacts in the aquatic environment have not yet been scientifically studied. This paper investigates the fibre composition of flushable and non-flushable wipes, specifically with regard to synthetic polymer material, using Fourier transform infrared (FTIR) and microRaman spectroscopy along with fluorescence microscopy. The study demonstrated the presence of polyester (polyethylene terephthalate, (PET)), high-density polyethylene (HDPE) and polyethylene/vinyl acetate (PEVA/EVA) in some flushable wipes and PET in all non-flushable. Other polymers such us polypropylene (PP), low-density polyethylene (LDPE), expanded polystyrene (EPS) and polyurethane (PU) were also identified as potential components in the flushable material. Hence, commercially available wet wipes labelled as flushable could also be considered as a possible source of microplastic fibres in the wastewater streams and, if not retained, in the environment

Release of microplastic fibres and fragmentation to billions of nanoplastics from period products: preliminary assessment of potential health implications

Health effects related to the plastic content of disposable period products have not been recognized or scientifically addressed. To begin to understand their potential impact on the environment and human health, this study employed standardised in vitro tests (Syngina), infrared spectroscopy (FTIR), confocal Raman microscopy, scanning electron microscopy (FEG-SEM) and nanoparticle tracking analysis (NTA) to characterize the bulk chemical composition of different components in period products, and quantified the amount of fibres released using in vitro experiments, and measured their fragmentation into smaller particles (nanoplastics) under conditions that mimic vaginal fluids. It was found that 12 out of 24 of the tested products contain synthetic polymers (plastics) that would be in direct contact with the vaginal wall when in use. Many of the products released fibres during in vitro tests and also fragmented to release up to 17 billion nanoplastics per tampon. These micro fibres and nanoplastics could be released into the environment upon disposal. The health implications within the body are unknown, but due to the large quantity of nano size plastics being released, public health concern could manifest in three ways: from the nanoplastics themeselves, from release of contaminants adsorbed to the nanoplastics and finally, from leaching of additives associated with the production of the plastics

Degradation of scrapie infected brain homogenate by a novel bacterial keratinase.

Prion protein is central to Transmissible Spongiform Encephalopathy (TSE) pathogenesis. Characteristically prion is resistant to conventional methods of sterilization and the most effective means of its degradation are incineration and alkaline hydrolysis. These methods are limited by environmental acceptability, application compatibility, cost and loss of reusable materials. Enzymatic degradation provides a viable alternative for decontaminating animal carcasses, specified risk materials, as well as surgical and dentistry instruments. The objective of this research was to isolate and characterise microbial keratinases and to investigate their ability to degrade keratinaceous materials and possibly scrapie prions. Microbial isolates from farmyard waste were grown on feather meal medium and the synthesised keratinase characterised by MALDI-MS and SDS-PAGE. Keratinolytic activity was determined using keratin azure, casein and melanised feather as substrates. Degradation of scrapie prion was evaluated by western blotting analysis. One specific isolates, identified as a strain of Bacillius licheniformis, demonstrated considerable promise. The molecular weight of the enzyme produced by this bacteria was found to be ≈28KDa, with optimum pH and temperature at 8.0 and 50 °C respectively. This novel keratinase demonstrated significant activity on keratin azure (11 U/mL) and casein substrates, and completely degraded melanised feather within 48h. Western blotting analysis shows significant reduction in prion signal and immunoreactivity for scrapie infected mouse (ME7) brain homogenate after incubation with this keratinase. Inclusion of a biosurfactant also further enhanced degradation of scrapie prion. The ability of this novel bacterial keratinase to degrade keratin materials and scrapie prion suggests its potential use as an environmental alternative in prion decontamination and other applications

The mechanisms of detoxification of As(III), dimethylarsinic acid (DMA) and As(V) in the microalga Chlorella vulgaris

The response of Chlorella vulgaris when challenged by As(III), As(V) and dimethylarsinic acid (DMA) was assessed through experiments on adsorption, efflux and speciation of arsenic (reduction, oxidation, methylation and chelation with glutathione/phytochelatin [GSH/PC]). Our study indicates that at high concentrations of phosphate (1.62 mM of HPO42−), upon exposure to As(V), cells are able to shift towards methylation of As(V) rather than PC formation. Treatment with As(V) caused a moderate decrease in intracellular pH and a strong increase in the concentration of free thiols (GSH). Passive surface adsorption was found to be negligible for living cells exposed to DMA and As(V). However, adsorption of As(III) was observed to be an active process in C. vulgaris, because it did not show saturation at any of the exposure periods. Chelation of As(III) with GS/PC and to a lesser extent hGS/hPC is a major detoxification mechanism employed by C. vulgaris cells when exposed to As(III). The increase of bound As-GS/PC complexes was found to be strongly related to an increase in concentration of As(III) in media. C. vulgaris cells did not produce any As-GS/PC complex when exposed to As(V). This may indicate that a reduction step is needed for As(V) complexation with GSH/PC. C. vulgaris cells formed DMASV-GS upon exposure to DMA independent of the exposure period. As(III) triggers the formation of arsenic complexes with PC and homophytochelatins (hPC) and their compartmentalisation to vacuoles. A conceptual model was devised to explain the mechanisms involving ABCC1/2 transport. The potential of C. vulgaris to bio-remediate arsenic from water appeared to be highly selective and effective without the potential hazard of reducing As(V) to As(III), which is more toxic to humans

Measurement of direct photon production at Tevatron fixed target energies

Measurements of the production of high transverse momentum direct photons by a 515 GeV/c piminus beam and 530 and 800 GeV/c proton beams in interactions with beryllium and hydrogen targets are presented. The data span the kinematic ranges of 3.5 < p_T < 12 GeV/c in transverse momentum and 1.5 units in rapidity. The inclusive direct-photon cross sections are compared with next-to-leading-order perturbative QCD calculations and expectations based on a phenomenological parton-k_T model.Comment: RevTeX4, 23 pages, 32 figures, submitted to Phys. Rev.