A review of toxicity assessment procedures of solar photovoltaic modules

Environmental management of solar photovoltaic (PV) modules is attracting attention as a growing number of field-operated PV modules approach end of life (EoL). PV modules may contain small amounts of toxic metals, and the procedures for assessing and regulating the toxic metal content and release of such materials at EoL differ widely across nations. This paper provides an overview of the metal composition of PV modules and common procedures for toxicity assessment through extensive research and review of technical literature and legislative documents. This review focuses on three primary aspects: first, it explores the distribution of toxic elements within current and emerging PV module designs, with a specific focus on obtaining representative samples for proportional toxicity testing within different module laminate areas. Second, it examines a sampling standard and the diverse toxicity testing methods and regulations employed in various regions, encompassing standards like the Environmental Protection Agency (EPA) Test Method 1311 (Toxicity Characteristic Leaching Procedure, TCLP) in the U.S., Restriction of Hazardous Substances (RoHS) in Europe, and the Waste Extraction Test (WET) in California. Third, the review examines the sources of variability in toxicity testing outcomes, including techniques for securing homogeneous samples from non-uniform PV modules, selecting particle sizes representative of landfill conditions in extracted samples, determining appropriate leachate characteristics such as leaching agents and pH levels, and considering factors like test duration and temperatures. In summary, this review summarizes relevant regulations and offers a comprehensive overview of the strengths and limitations associated with several toxicity assessment procedures currently in practice.

Thermoelectrically-Cooled InAs/GaSb Type-II Superlattice Detectors as an Alternative to HgCdTe in a Real-Time Mid-Infrared Backscattering Spectroscopy System

We report on the development of thermoelectrically cooled (TE-cooled) InAs/GaSb type-II superlattice (T2SL) single element infrared (IR) photodetectors and exemplify their applicability for real-time IR spectroscopy in the mid-infrared in a possible application. As the European Union's Restriction of Hazardous Substances (RoHS) threatens the usage of the state-of-the-art detector material mercury cadmium telluride (MCT), RoHS-compatible alternatives to MCT have to be established for IR detection. We use bandgap engineered InAs/GaSb T2SLs to tailor the temperature-dependent bandgap energy for detection throughout the required spectral range. Molecular beam epitaxy of superlattice samples is performed on GaAs substrates with a metamorphic GaAsSb buffer layer. Photolithographic processing yields laterally-operated T2SL photodetectors. Integrated in a TE-cooled IR detector module, such T2SL photodetectors can be an alternative to MCT photodetectors for spectroscopy applications. Here, we exemplify this by exchanging a commercially available MCT-based IR detector module with our T2SL-based IR detector module in a real-time mid-infrared backscattering spectroscopy system for substance identification. The key detector requirements imposed by the spectroscopy system are a MHz-bandwidth, a broad spectral response, and a high signal-to-noise ratio, all of which are covered by the reported T2SL-based IR detector module. Hence, in this paper, we demonstrate the versatility of TE-cooled InAs/GaSb T2SL photodetectors and their applicability in an IR spectroscopy system.

Determination of metal content in industrial powder ink and paint thickness over steel plates using X-Ray Fluorescence

The Energy Dispersive X-Ray Fluorescence (EDXRF) is a well stablished technique that may be used in quality control of industrial processes. In this study, it was proposed an analysis of a two commercial powder inks widely used in the industry. The goals were to determine the composition of the ink by quantifying its inorganics elements by EDXRF, and check if the amount of toxic elements matches with Restriction of Certain Hazardous Substances (RoHS) and with "Norma Brasileira" (NBR) regulations. Moreover, to build Partial Least Squares Regression (PLSR) models to predict the thickness of the ink layer applied over steel plates using EDXRF data. Evaluating the quantitative results, it was found that some samples presented toxic elements, such as Cr and Pb. The PLSR results ranged from 54 μm to 97 μm with an average relative deviation of 1% compared to the conventional method used for thickness determination (magnetic method). The results show that EDXRF is a reliable alternative technique to determine the metal elements on the powder ink composition. Furthermore, a (PLSR) model can be used to determine the thickness of the ink applied over steel plates.

Polybrominated diphenyl ethers listed as Stockholm Convention POPs, other brominated flame retardants and heavy metals in e-waste polymers in Nigeria

Polybrominated diphenyl ethers (PBDEs) were the first brominated persistent organic pollutants (POPs) listed in the Stockholm Convention. Parties to the convention are currently establishing inventories for developing action plans for the environmentally sound management of PBDE-containing materials. The major use of commercial octabromodiphenyl ether (c-OctaBDE) has been in casings from cathode ray tube (CRT) TVs and computer monitors. Large quantities of used e-waste and electronic equipment have been exported to developing countries with Nigeria being a major importer in Africa. The casings from 382 TVs and computers imported from major world regions to Nigeria were sampled in backyards and waste dumps. The samples were screened with X-ray flourescence (XRF) for bromine and analysed by gas chromatography/ electron capture detection (GC/ECD) for brominated flame retardants (BFRs). A high proportion of the CRT casings (61 %) contained more than 10,000 ppm bromine from BFRs. Decabromodiphenyl ether (DecaBDE) was the major flame retardant used in TV sets and tetrabromobisphenol A (TBBPA) for computer CRTs.The screening suggests that average PBDE levels (of c-OctaBDE + DecaBDE) in Nigerian-stockpiled CRT casings were 1.1 % for TV and 0.13 % for PC CRTs. These are above the Restriction of Hazardous Substances (RoHS) limit and should be separated for RoHS compliant recycling. The Nigerian e-waste inventory of 237,000 t of CRT plastic would therefore contain approx. 594 t c-OctaBDE and 1,880 t of DecaBDE. In Nigeria, as for most developing countries, there is currently no adequate e-waste management, plastic separation or destruction capacity. The data highlight the urgent need to develop environmentally sound management for this large material flow.