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Reusing materials in the field of construction is an aspect of European environmental goals that cannot be overlooked. Construction & Demolition Waste (CDW) is on the increase and its poor management contributes to climate change and pollution, thus affecting our health and wellbeing. The use of secondary materials in construction has hence been raised as a key circularity measure to reduce the impact of CDW on the environment. Consequently, citizens need to be willing to support its regulations and accept the use of those materials in buildings, particularly housing. Little is currently known about public opinion as regards the use of those materials in construction; accordingly, this study seeks to establish citizen perception in that respect, but the aim is also to consolidate an instrument and an approach with which to expand the study focus to other European countries in the future. Six hundred and five citizens of the Basque Country were interviewed for that purpose. The results show that there is a gap between attitudes and behaviour; there is majority acceptance of the circularity of construction products, but that is no guarantee that the majority of the population are going to behave in such a way to support it. Therefore, there is a clear need to work on the most appropriate methodology to promote that behaviour. The data indicate that information and awareness-raising are the most influential aspects in that regard. • Limited literature on citizen perceptions of building with recycled material. • Case study in southern Europe and proposal of questionnaire. • Increasing societal knowledge needed for accepting circularity in construction. • 90 % would benefit from knowledge campaigns by scientific and construction sectors. • All profiles, even denialist, would increase acceptance through incentives. [ABSTRACT FROM AUTHOR]

• WEEE were used as secondary raw material to produce gold nanoparticles. • Gold was selectively extracted from microprocessors by hydrometallurgical methods. • Nanoparticles synthesis was developed according to the obtained Au (III) solution. • Obtained nanoparticles are pure, stable and can be used as optical sensors. One of the current challenges in circular economy is the ability to transform waste into valuable products. In this work, waste of electrical and electronic equipment (WEEE) was used as a gold source to prepare stable gold nanoparticles (AuNP). The proposed methodology involves a series of physical and chemical separation steps, carefully designed according to the complex nature of the selected WEEE and the targeted product. In a first step, pins from microprocessors were separated by mechanical treatments, allowing to concentrate gold in a metallic fraction. A two-step hydrometallurgical method was subsequently performed, to obtain a Au (III) enriched solution. Such solution was used as a secondary raw material to obtain AuNP. For that purpose, a specific synthetic method was developed, adapted to the high acidity and ionic strength of the solution. Thanks to the use of two easily available reducing agents (sodium citrate and ascorbic acid) and a polymeric stabilizer (PVP), it was possible to obtain high purity AuNP presenting a mixture of well-defined spherical and triangular shapes. These AuNP were finally deposited onto glass substrates and present a sensitive response to refractive index changes in the environment, a necessary condition towards application in optical sensors. In summary, this upcycling case study demonstrates that e-waste can successfully replace primary raw materials to obtain highly valuable and useful nanomaterials. These results highlight the potential of urban mining as a sustainable and circular approach to the development of nanotechnologies. [ABSTRACT FROM AUTHOR]

Red Mud (RM) is a byproduct of the Bayer Process, used to extract alumina from bauxite. This residue contains valuable metals and rare earth elements (REEs), which can be bioleached under acidic conditions and later recovered, eventually reducing the RM pollution potential. The focus of this study was to extract metals through bioleaching using biostimulated biomass. A sequencing batch reactor (SBR) was operated at two different solid to liquid ratios (S/L, 2% and 1.5%) under aerobic conditions, using a feeding strategy based on pH evolution over time. The lowest pH obtained at 2% S/L was 3.8. Metals extraction efficiencies were 68 ± 18% for Mn, 58 ± 4.5% for Mg, 51 ± 2.9% for Al, 0.6 ± 0.07% for Ti and < 0.1% for Fe. At 1.5% S/L, a slightly lower pH was achieved (3.4), with metals extraction efficiencies similar to those obtained at 2% S/L, but more stable over time. At 1.5% S/L, REEs (i.e., Nd, Ce, Y, Sc and La) extraction efficiencies were also evaluated, and the highest value was obtained for Nd (around 65%). The results were promising and provided useful information for further enhancing the efficiency of metals extraction, in the perspective of process scale-up. • Bioleaching of valuable metals and REEs from red mud was achieved in an SBR. • Biomass was properly stimulated and naturally enriched without inoculum addition. • Significant extraction efficiencies for Al, Mg, and Mn were obtained. • Promising extraction efficiency of around 65% was reached for Nd. • Similar extraction results were obtained at 2% and 1.5% S/L. [ABSTRACT FROM AUTHOR]

Prevention and mitigation of acid rock drainage (ARD) from mine wastes are crucial for limiting environmental impact. However, preventive measures are often too expensive, potentially harmful to the environment or not applied early enough. This study aimed to test the potential of different secondary raw materials for maintaining a circumneutral pH (6–7) in a sulfide oxidation environment, allowing secondary minerals to form on reactive sulfide surfaces to prevent release of acid, metals and metalloids, and thereby ARD generation. Five materials (blast furnace slag, granulated blast furnace slag, cement kiln dust, bark ash, lime kiln dust) were selected based on their alkaline properties, availability and yearly yield. High sulfidic (>50 wt%, sulfide) waste rock from an active Cu–Zn–Au–Ag open pit mine in northern Sweden was leached in small-scale laboratory test cells under ambient condition for 4–8 weeks before adding secondary raw materials on the surface in an attempt to prevent ARD generation. During 52 subsequent weeks of leaching, the pH and electrical conductivity in the leachate from the waste rock varied between 1.7-4.6 and 2.1–22.8 mS/cm, respectively. All secondary raw materials were able to increase the pH to circumneutral. However, blast furnace slag, granulated blast furnace slag and cement kiln dust were not able to maintain a circumneutral pH for an extended time due to self-cementation or carbonation, whereas bark ash (1 wt%) and lime kiln dust (5 wt%) prevented acidity, metal and metalloid leaching. Materials such as cement kiln dust and bark ash contained elevated concentrations of, e.g., Cd and Zn, but the release of metals and metalloids was generally low for most elements, except for Cl, K and Na, most likely due to salt dissolution. • Addition of secondary raw materials decreased metal and metalloid concentrations. • Lime kiln dust maintained a circumneutral pH throughout leaching. • Salt dissolution had a negative effect on the leachate quality. [ABSTRACT FROM AUTHOR]

Abstract Poor storage of industrial wastes has been a cause of land contamination issues. These wastes or by-products have the potential to be used as secondary raw materials in construction, promoting the concept of a circular economy that will avoid land contamination. Here we evaluate radiological environmental impacts when wastes that contain elevated levels of naturally occurring radionuclides (NORs) such as red mud, fly ash and ground granulated blast furnace slag are made into 'green cements' such as geopolymers or alkali-activated materials (AAMs). During the study, three AAM concrete and mortar series with various mixing ratios were prepared and investigated. The NOR content, I-Index, radon emanation and exhalation of the precursor waste materials and their cement products were measured and calculated and the strength of the cement products was compared. The emanation and the exhalation properties were calculated for the final products, weighing the data of the components as a function of their mixing ratio. The I-index alone suggested that the AAMs would be suitable products. AAMs containing ground granulated blast furnace slag exhibited the lowest radon exhalation and higher compressive strength, while the fly ash and red mud AAMs had increased final radon exhalation. In the case of fly ash, alkaline activation of fly ash dramatically increased the radon exhalation; the highest measured fly ash exhalation was 1.49 times of the theoretically calculated exhalation value. This highlights the increased risk of using fly ash as a component in AAMs and the need to carry out testing on the final products as well as individual secondary raw materials. Graphical abstract Unlabelled Image Highlights • Three alkali-activated materials were prepared using secondary raw materials. • The radiological properties of the secondary raw materials and AAMs were determined. • The fly ash content increased the radon exhalation during alkali activation. • Increasing GGBFS content resulted in better radiological and strength property. [ABSTRACT FROM AUTHOR]

• Solar panels can be effectively dismantled by Electro-Hydraulic Fragmentation (EHF). • Both crushing and EHF produce a wide fraction distribution between <0.25 to >4 mm. • Crushing followed by sieving results in a high level of metals in all fractions. • EHF and sieving concentrates metal elements into two main fractions <0.5 and >4 mm. • Over 98% of Cu in a PV panel is found in the >4 mm fraction produced by impulse EHF. Currently, the first generation of solar panels are reaching their end-of-life, however so far, there is no best available technology (BAT) to deal with solar panel waste in terms of the optimized circular economy of metals. In this brief communication, electro-hydraulic fragmentation (EHF) is explored as an initial conditioning stage of photovoltaic (PV) modules to facilitate the recovery of valuable metals with the main goal to produce liberated fractions that are suitable for the retrieval of materials like Si, Ag, Cu, Sn, Pb, and Al. When compared to traditional crushing, the results suggest that dismantling of PV panels using EHF shows more selectivity by concentrating metals among well-defined particle size fractions. Using this method, the subsequent recovery of metals from PV panels can be achieved in a straightforward manner by simple means like sieving. The fragmentation achievable with EHF technology allowed approximately 99% Cu, 60% Ag, 80% of Pb, Sn and Al total elemental weight within the solar panels to be concentrated solely within the >4 mm size range, whereas high purity (>99%) Si could be found in the fractions between >0.50 mm and <2 mm. To the best of the authors' knowledge, this paper presents for the first time a comparative analysis on the use of EHF technique and conventional crushing for the processing of PV solar panel waste. [ABSTRACT FROM AUTHOR]

• Pioneering valorization of sulfidic mine tailings into cold-bonded granules. • Minimal heavy metal leaching endorses safe use in second-life applications. • Granule content versus concrete performance (workability, strength and durability). Repurposing sulphidic tailings in construction products offers a sustainable solution for this mining waste. Aggregates (1–4 mm and 2–8 mm) were produced at pilot scale using cold granulation with minimal cement content (6 wt% CEM III/B + 94 wt% tailings). Superplasticizer dose was optimized in mortar and concrete mixes replacing 17 % and 32 % of natural aggregates. The concretes benefit from the additional buffering capacity from cement hydrates in granules (relevant for carbonation and chloride penetration), but their increased porosity lower freeze–thaw resistance. Cement-based mixes offer a sustainable solution for this waste in applications with moderate or non-structural requirements. [ABSTRACT FROM AUTHOR]

Waste materials and industrial by-products are increasingly used in the production of cement clinker and cement, serving as secondary fuels, secondary raw materials, and supplementary cementitious materials. As these waste-derived materials are partially or fully incorporated into the product, they are technically recycled. Consequently, a certain proportion of the cement consists of recycled materials. This paper presents a method to calculate this recycled content in cement not only based on mass streams, but also based on valuable chemical components and compares the results for both calculation methods in the course of a case study of two Austrian cement plants. It is demonstrated that one metric ton of cement consists of 365 kg and 387 kg of secondary materials, respectively. This results in an average recycled content of 37.6 %. In addition, the contribution of primary and secondary materials to the heavy metal content of cement is assessed. [Display omitted] [ABSTRACT FROM AUTHOR]

There is low utilisation of plastic waste in the Nordic region and only a fraction of plastic materials go back into production processes through reuse and recycling practices. This paper aims to increase knowledge concerning factors that inhibit demand for recycled plastics, and to identify critical barriers for plastic recycling across the regional plastics value chain. A literature review and targeted interviews with key actors across the plastics value chain enabled the mapping of interactions between the major actors and identified hotspots that act as barriers to the flow of plastic materials. Barriers identified include the lack of both supply and demand of recycled plastic and are mainly attributed to the fragmented market of secondary materials. The main hotspots identified are the low demand due to price considerations, insufficient traceability and transparency in value chain transactions, and general design deficiencies in the recyclability of products. Value chain coordination is considered as the most important intervention by the interviewees, followed by the need for increased investment in innovation and technology development. Complementary measures that could counteract the identified barriers include public procurement for resource efficiency, ban on the incineration of recyclable materials, and specifications on the design of plastic products for reducing the number of different polymers, and the number and usage of additives. [ABSTRACT FROM AUTHOR]

Increasing problems associated with sewage sludge disposal are observed nowadays. As the thermal conversion of sewage sludge (combustion, co-combustion, gasification and pyrolysis) appears to be the most promising alternative for its management, the solid residues left after gasification were examined. The present study evaluates the potential of this waste as an alternative phosphorus source in the context of phosphorus recovery. The obtained solid gasification residues were characterised (chemical and phase composition, thermal properties, surface properties and technological parameters used for phosphorus raw materials) and compared to commercial phosphate raw materials. It was revealed that gasification residue is a valuable source of phosphorus and microelements, comparable to sewage sludge ash (SSA) considered nowadays as secondary phosphorus raw materials. Chemical properties as well as technological parameters characteristic for natural phosphate ores are different. Solid gasification residue was leached with mineral acids (phosphoric and nitric) according to the patented method of phosphorus recovery - PolFerAsh, developed by Cracow University of Technology. It was revealed that phosphorus can be selectively leached from solid gasification residue with high efficiency (73–82%); moreover, most of the iron and heavy metals stay in the solid phase due to the low concentration of acids and proper solid to liquid phase ratio. The obtained leachates are valuable products that can be considered for the production of fertilisers. Combining the gasification process with nutrient recovery provides the opportunity for more environmentally efficient technologies driven by sustainable development rules. [ABSTRACT FROM AUTHOR]

Waste incineration bottom ash is considered a secondary resource for valuable trace elements (TE), which is currently neglected in most European countries. Phytomining could potentially recover valuable TE from such waste materials but is still at an exploratory stage with many challenges. The use of bioaugmentation to improve plant growth and TE accumulation of metal-tolerant high biomass plants growing on waste incineration bottom ash was evaluated. Bacterial strains that were previously isolated from rhizosphere, roots and contaminated soil were selected according to their plant growth promoting characteristics and tolerance to the bottom ash substrate. Those selected bacterial strains were tested for their beneficial effects on Nicotiana tabacum and Salix smithiana with regards to phytomining. The rhizobacterial strain Rhodococcus erythropolis P30 enhanced the shoot dry weight of N. tabacum by on average 57% compared to the control plants. Several bacterial inoculants enhanced biomass production and the nutritional status of S. smithiana . Moreover, those bacterial strains previously described to enhance biomass production of N. tabacum and members of the Salicaceae on TE-contaminated soils, also enhanced biomass production of these species on bottom ash. However, bacterial inoculants could not enhance trace element accumulation in plants. [ABSTRACT FROM AUTHOR]

The main idea of this research was to evaluate rice and sunflower hulls, sawdust and their ashes, as additives in clay brick production using mathematical analysis. All available papers, containing the parameters of interest, were used in the study, which consisted of total 316 cases, obtained from the literature. The major oxide content of clays and mixtures, then weight percent addition and particle size ranges of secondary raw materials, and process parameters (firing temperature, soaking time and average heating rate) were selected as inputs to mathematical models. Shaping moist was the only parameter characterizing transition state of the products analyzed as an output parameter. The other parameters described the fired product quality: linear shrinkage, bulk density, water absorption, compressive and bending strength. The main goal was to find the relationships and the main influences between raw material properties, process parameters, and the quality of the obtained products and mixtures, by using mathematical tools. Statistical and mathematical analyses were applied for prediction of final product quality. Developed artificial neural network empirical models (ANNs) give a reasonable fit to experimental data and successfully predict the most of the observed output variables, showing the good prediction capabilities (coefficient of determination varied between 0.714 and 0.998). Sensitivity analysis showed that, among all the studied parameters concerning raw materials and process parameters, the dominant influence belonged to loss on ignition. [ABSTRACT FROM AUTHOR]

While gypsum can effectively be recycled, most gypsum waste (GW) is currently landfilled in the European Union. In order to achieve higher recovery rates and promote a closed-loop supply chain, it is necessary that stakeholders can implement best practices, in particular from waste production to waste processing, processes that are part of the end-of-life (EoL) stage. In this stage, waste production cannot be reduced, and therefore the priority should be to appropriately collect and recover EoL products. The aim of the paper is to investigate best practices for the management of EoL gypsum in a circular economy. To achieve this, best practices for the management of EoL construction products are selected from the literature, adapted to the case of EoL gypsum and subjected to stakeholder consultation. Results revealed significant differences in the waste management practices between two target groups: gypsum recycling and non-gypsum recycling countries. It is concluded that three best practices are fundamental to promote a circular economy for gypsum products: on-site segregation of GW, clear waste acceptance criteria and clear recycled gypsum quality criteria. [ABSTRACT FROM AUTHOR]

At the earth dams, malfunctions, leaks and loss of stability can occur during use. Chemical grouting of the dams is one of the repair options. It is possible to use fly ash within this technology. The use of fly ash in the grout significantly improves the rheological properties of the mixture, reduces costs to repair and also fulfils environmental requirements. It has been shown that, thanks to a suitable granulometry and mineralogical composition of the fly ash, using it in the grout can partially replace clay, which is a base material, while maintaining the technical characteristics of the mixture. [ABSTRACT FROM AUTHOR]

The issue of resource security has come to the forefront of the debate as Critical Materials (CRM) and Raw Materials (RM) supply is fundamental to maintain and develop EU economy. Considering the increasing scarcity and raising prices of RM, their recycling and recovery from anthropogenic deposits is essential. To date there is no homogeneous inventory available of SRM and CRM present in EU landfills, and best management practices to recover SRM from landfill activities are inefficient. In this context, the EU SMART GROUND project intends to foster resource recovery in landfills by improving the availability and the accessibility of data and information on SRM in the EU. [ABSTRACT FROM AUTHOR]

• Coal combustion bottom ash was used for synthesis of belite–sulfoaluminate clinkers. • Clinker phases, microstructure and reactivity was studied at 1200, 1250 and 1300 °C. • Various raw material derived impurities incorporated in main clinker phases. • Ti stabilized β-belite and alkalis lowered optimal sintering temperature. • Sintering at 1200 °C resulted in the most reactive and the easiest grindable clinker. The incorporation mechanism of impurities derived from raw materials into a belite-sulfoaluminate cement clinker with bottom ash was investigated in two raw mixtures. Alkalis lowered the sintering temperature by 50 °C. Ti stabilized β belite and prevented the formation of γ-belite. Sodalite solid solution showed an incomplete substitution of Si by Al. At a higher Ti content ferrite solid solution trended towards perovskite composition. Although calcium sulfoaluminate only fully developted at 1300 °C, the clinkers sintered at 1200 °C were the most reactive, as the presence of anhydrite at 1200 °C accelerated early hydration. Clinker reactivity decreased with an increase in sintering temperature. [ABSTRACT FROM AUTHOR]

[Display omitted] • Alkaline cements can be prepared from mixtures of sulfate-bearing clay and Pietra Serena sludge. • CaO deriving from Pietra Serena sludge takes part in alkali activation process to form hybrid cement. • SO 4 2- from kaolinitic clay can be trapped in the cement. • SO 4 2- can drive CAN-type zeolites formation. The feasibility of transforming the residues of cultivation of two rocks into secondary raw materials through the alkali activation process has been assessed. Mixtures of a sulfate-bearing kaolinitic clay (L02-K) and a sludge derived by the sewing of Pietra Serena stone (sPS) have been investigated. These materials were preliminarily treated at high temperature to improve their reactivity (heat-treated samples are hereafter labelled as L02-MK and sPS-800). Pastes were prepared with mixtures of L02-MK and sPS-800 in different weight proportions by using 8 M NaOH solutions as alkaline activator and cured at 85 °C for 24 h. Mechanical strength was determined after 1, 7 and 28 days and the reaction products were characterized by XPRD, SEM/EDX and MAS-NMR. Sulfate solubility was quantified by leaching tests. The alkali activation of the sole sulfate-bearing clay gives a material with developed mechanical strength of 4(1) MPa. Some N-A-S-H gel forms together with gibbsite and thenardite, which can be easily leached. Better results are obtained by the activation of mixtures of the two precursors, and mixed alkali cements or hybrid cements are obtained. The presence of CaO from heat-treated Pietra Serena sludge improves the mechanical strength of the resulting pastes up to 11.8(9) MPa. In this case, a mixture of gels forms, specifically, a calcium-rich gel (C-A-S-H-type) co-exists with (N,C)-A-S-H-type gel. U-phase and CAN-type zeolites also form. They trap sulfate from the clay and considerably reduce sulfate solubility. In conclusion, L02-MK and sPS-800 are promising raw materials for alkaline cements, whose properties may suggest application in soil stabilization or in waste confinement. [ABSTRACT FROM AUTHOR]

The demand for building and construction materials increases as the world population keeps growing, thus increasing the need of shelter, as a basic human need. This increasing demand for building and construction materials not only leads to higher demand for primary raw materials, such as clay or sand, but also to higher emissions of carbon dioxide that contribute to the greenhouse effect, leading us to the biggest and ongoing threat to life on earth: global warming. The potential use of secondary raw material sources, such as mining waste, in building and construction products not only minimises the ecological footprint of this sector but also minimises the pressure on the primary raw material sector, hence fostering the transition towards a more resource efficient and sustainable world. The goal of this study is to evaluate the potential use of uncleaned sulphidic mining tailing material from two inactive Pb-Zn (Plombières, Belgium) and Cu-Zn-Pb (Freiberg, Germany) mines, and uncleaned sulphidic mining waste rock material from an active Cu-Zn mine (Neves-Corvo, Portugal), in ceramic roof tiles and blocks taking into account production parameters (shaping, drying, and firing processes), product quality (technical, aesthetical, and chemical properties) and environmental compliance of secondary raw materials for use as building products. After a detailed physical, mineralogical, chemical, and thermal characterisation of the materials, blends for ceramic roof tiles and blocks were made by partly or totally replacing some primary raw materials (mainly clay and sand) by 4 different mining waste materials. Roof tile and block blends containing 5 wt% and 10 wt% mining waste materials, respectively, were produced on a lab scale. The required technical, aesthetical, and chemical properties for each ceramic product were evaluated. Freiberg tailing and Neves Corvo waste rock materials presented considerable amounts of sulphur and metal(loid)s. Moreover, technical, aesthetical, and chemical properties of the blends using these mining waste materials were not satisfying and the Neves Corvo waste rock materials have the disadvantage of needing a mechanical treatment (grinding and sieving) before integrating them into the ceramic blends. Therefore, the Freiberg tailing and both of the Neves Corvo waste rock materials are less suitable to replace primary raw materials in ceramic roof tile and block blends, even in smaller amounts (5 wt% and 10 wt%, respectively). In contrast, the Plombières fine tailing material was characterised by a low sulphur and metal(loid) content, as well as satisfying environmental performance. The roof tile and block blends, in which the Plombières tailing material was integrated, showed satisfying technical, aesthetical, and chemical properties. Consequently, the Plombières tailing material can be considered as the best fit to partly or totally replace primary raw materials in both ceramic roof tile and block blends. • Replacement of raw materials in ceramic roof tiles and blocks by mining waste was investigated. • High sulphur content in mining waste leads to technical and aesthetical problems in ceramics. • Mining waste with high sulphur and metal(loid) content requires pre-treatment before being incorporated in ceramics. • Plombières tailing shows the best fit to be incorporated in ceramic roof tile and block mixtures. [ABSTRACT FROM AUTHOR]

A successful transition to a Circular Economy, as promoted by the European Commission, requires solid information on the future availability of anthropogenic resources. Anthropogenic resources are human-made material stocks and flows, such as old landfills, buildings or different waste streams. A case study approach was adopted in this paper to investigate the role of the classification of anthropogenic resources in supporting the transition to a Circular Economy. The first objective is to identify the motivation and scope of the reviewed case studies. The second objective is to investigate to what extent they address the challenges linked to anthropogenic resource recovery. The third objective is to elicit in how far resource classification can contribute to promote anthropogenic resource recovery and to support the EU Action Plan for the Circular Economy. This paper includes case studies that classify materials recovered from old landfills, built infrastructure, national secondary metal stocks, electrical and electronic waste and waste incineration residues. With respect to anthropogenic resource recovery, five areas were identified, in which resource classification can have a meaningful contribution in the future, namely in knowledge management, research and development, policy support, (pre-) feasibility studies, and marketing. In a wider Circular Economy context, resource classification can play a key role in assessing anthropogenic resources in analogy to natural resources for integrated resource management. Further, it can be useful to improve communication along the value chain, e.g., to optimize waste management operations, processes and products for enhanced resource recovery and recyclability. Resource classification can also help compare different Circular Economy options. The paper concludes that a standardized classification, which encompasses guidance on detailed assessment of different types of anthropogenic resources, is necessary. This should take into account the fact that the availability of resources does not solely depend on the material quantities, but also on the technical, operational, economic, social, environmental and regulatory conditions which cumulatively enable or prevent recovery of these resources. • Information on available anthropogenic resources is key for a Circular Economy. • Anthropogenic resources can be assessed in analogy to natural resources. • Reviewed studies classify old landfills, built infrastructure, metal stocks, e-waste and waste incineration residues. • Different Circular Economy options could be compared in the future. • A standardized classification methodology for different types of anthropogenic resources is necessary. [ABSTRACT FROM AUTHOR]

The management of huge amounts of waste deriving from several anthropogenic activities, such as manufacturing, construction, mining and quarrying, dredging, represents a great contemporary environmental challenge for many countries worldwide. Among the different recycling possibilities, the use of the excavated soils, obtained from operations such as tunneling, excavations, mining, dredging etc., which are generally considered as soil waste, in the production of innovative eco-sustainable building materials represents an interesting alternative to their disposal. In fact, considering especially their chemical composition, low cost and easy availability, soil wastes seem to be the ideal candidates to be used as secondary raw materials for the manufacture of geopolymer-based materials. The paper intends to present a review of the recent scientific literature regarding the use of different types of soil waste to produce geopolymeric binders. Particular attention is focused on mining waste (deriving from various types of mining industries) and dredged sediments coming from marine harbors and natural and artificial water reservoirs, in order to understand and critically discuss the limits of their disposal approach and, at the same time, show perspectives and challenges for possible future research activities in this field. The production of geopolymer-based building components, starting from mining waste and reservoir sediments, is widely discussed thanks to the numerous scientific findings, while the recycling of marine dredged sediments through geopolymerization represents a completely new and innovative trend in research activity, in fact only few related papers were found in literature. It can be strongly stated that geopolymerization can significantly contribute to a sustainable improvement of soil waste management systems. Image 1 • The need to replace cement with more green binders promoted geopolymer production. • Chemical-mineralogical features made soil waste suitable as geopolymer precursors. • The combination of soil waste with other kinds of waste was an interesting option. • Geopolymers synthesis was promising to reduce soil waste environmental impact. [ABSTRACT FROM AUTHOR]

Carbon fibers reclamation from waste composites by pyrolysis is developing fast. Pyrolysis allows the reclamation of the fibers by thermal decomposition of the polymeric resin, but the material value of these resins is not yet recovered. In this research work, the possibility of obtaining high-value gaseous fractions by treating the vapors generated in the decomposition of a poly(benzoxazine) containing carbon fiber waste composite has been studied. The experiments have been carried out in a lab-scale facility consisting of two reactors in series. In the first reactor, the pyrolysis of the waste is carried out at 500 °C, while in the second reactor the vapors coming from the first reactor are treated at 900 °C. Such treatment enables to triple the amount of gas in comparison to conventional pyrolysis. Besides, this gas contains 56% by volume of H 2 , which means the recovery of approximately 60% of the hydrogen contained in the resin. On the other hand, clean carbon fibers with mechanical properties within commercial values have been also obtained. • Clean recycled carbon fibers are obtained from waste composites by pyrolysis. • The pyrolysis process is upgraded by thermal treatment of the vapors generated. • The material value of the polymeric resin is recovered by H 2 rich gases production. • The thermal treatment is optimized by using refractory material as reactor filler. • Optimizing the process increases economic and environmental profitability. [ABSTRACT FROM AUTHOR]

This research explores the material recovery from bottom-ash, which is a residue from municipal solid waste incineration. The investigations aimed to characterize, evaluate, categorize and classify the development status of the recovery projects in the Canton of Zürich, including two technology pathways, i.e. dry and wet bottom-ash recovery. The temporal scale commenced with the exploration phase in 2003 and concluded with two technological pathways, both operating commercial projects in 2017. A retrospective view allowed the identification of enablers and barriers that affected the development status of the recovery projects. Further the recovery perspective allowed the results to be communicated to the United Nations Framework Classification for Resources (UNFC). The investigation showed two main trends. Firstly, the development status of the recovery projects from exploration to commercial project phase was mainly driven by the knowledge increase regarding sampling and metal characterization in bottom-ash, the readiness and effectiveness of the recovery technologies and the changes of the legal and financial environment. Secondly, the amount of recovered material (dry matter content) increased from about 6900 tons in 2003 to 16,500 tons in 2017, which is congruent with an increase in the recovery rate from 5 to 14 percent per weight. In particular, the amount of elements recoverable with an economic and environmental benefit, such as copper, gold and silver, increased. Correspondingly, the residual particular metal content in the disposable bottom-ash (fraction 2–16 mm) decreased to < 1 percent per weight dry matter and therefore reduced the risk for environmental at the sanitary landfills. The findings provide 'lessons learned' for companies, authorities and investors who intend to develop material recovery projects. Even though the recovery potentials depend on site-specific conditions, the UNFC allows comparing individual recovery projects under different boundary conditions. Image 1 • Raw material recovery projects were characterised and evaluated. • The recovery from bottom-ash in the Canton of Zurich was chronicled by milestones. • Key factors that influence the development of metal recovery were identified. • Recovery projects were assessed and classified based on the UNFC. • Bottom-ash was categorised into sales and non-sales quantities. [ABSTRACT FROM AUTHOR]

• A method to track the fate of materials in e-waste flows in EU is presented. • An extension to the current indicators to assess WEEE treatment systems is proposed. • Recovery performance of waste screens in France is assessed per target elements. • The type of screens collected impact the materials potentially available for recycling. • Tracking the quality of WEEE flows can boost (critical) raw materials recovery. Currently, in the European Union (EU), e-waste chain performance is assessed by technical indicators that aim to ensure system compliance with collection and recovery targets set by the WEEE Directive. This study proposes indicators to improve WEEE flow monitoring beyond the current overall weight-based approach, including complementary flows and treatment performance. A case study focused on the screen category in France is presented. In 2017, the collection rate of cathode-ray tube screens (CRT) was 68%, while for flat panel display (FPD) generated only 14% was collected. CRT screens have less precious and critical materials than FDP. Thus, elements like cobalt and gold highly concentrated in FPD, have a collection rate two to four times lower than elements such as copper (37%) which represents a high proportion in CRTs. Recycling is the main treatment in France. Nevertheless, the recycling rate per element varies significantly due to the low collection, and also the lack of technology and/or secondary raw materials market. The elements with higher recycling rates are base metals such as copper (28%), followed by precious metals like silver (23%), and gold (13%). Except for palladium, the recycling rate of the critical raw materials targeted in the study ranged from 6% (cobalt) to 0% (e.g. neodymium and indium). The results stress the need for indicators to support the development of WEEE chain from waste management to secondary (critical) raw materials suppliers. [ABSTRACT FROM AUTHOR]

Cities are becoming one of the greatest generators of waste and thus a potential source of secondary materials. One of the most attractive waste streams in cities is waste electrical and electronic equipment (WEEE) as they contain many valuable metals, mainly in the printed circuit board (PCB), with a high risk of a disruption in their supply. Many of the PCBs contained in small WEEE are separated by destructive operations, as the economic feasibility of their separation using non-destructive operations remains unclear. This paper examines the feasibility of separating the PCB and the permanent magnets (PMs) contained in hard disk drives (HDD) using non-destructive operations. The economic cost of separating these parts is evaluated by the disassembly sequences, the disassembly schemes, and using the 'ease of Disassembly Metric' (eDiM). In HDD, the economic cost for the non-destructive separation of the PCB is €0.05 while the cost to harvest the PCB as well as the PMs is €0.39. In both cases, such cost is well below the estimated economic value of the gold, silver, and palladium contained in the PCB (€0.85). As a result, the paper concludes that the separation of the PCB and the PMs of HDDs is economically profitable. Measures for promoting the non-destructive separation of the PCBs and the PM of HDDs should be further promoted, as they could help improve the supply of secondary raw materials. [ABSTRACT FROM AUTHOR]

Phosphogypsum (PG) is an attractive secondary raw material for rare earth elements (REEs) because it is abundant and contains significant amounts of REEs. Herein, the resin-in-leach (RIL) process for REE recovery from PG was studied, and the factors affecting the yield and selectivity of conventional leaching and RIL are discussed based on the batch equilibrium data obtained using four different lixiviants, H 2 SO 4 , HCl, H 3 PO 4 , and NaCl. It was found that the chelating resin enabled the use of a low H 2 SO 4 concentration (1 g/L) in the RIL process. The REE recovery yield and purity in the single-stage RIL process were higher when the chelating resin was used than when strong acid resins were used. The difference was significant in the multistage cross-current RIL process, where a loading of 19.2 g(REE)/kg(resin) and up to 20% purity were obtained with the chelating resin (vs. 3% in strong acid resin) after four stages. It is concluded that neither the breaking of the PG structure, nor the adsorption of calcium by the resin is necessary to enhance REE recovery. Considering the available literature and patents, this is a promising finding. REEs can be eluted from strong cation exchangers using a saturated sodium chloride solution, while EDTA or concentrated hydrochloric acid is required in the case of a chelating resin. However, Ca and REE can be further separated during elution of the chelating resin. • A resin-in-leach process for recovery of rare earths from phosphogypsum was studied. • The yield (up to 75%) and REE purity obtained are very good compared to previous literature. • Chelating resin provides higher selectivity and loading than strong acid resins. • With chelating resin 19.2 g(REE)/kg and 14.7 g(Ca)/kg loadings were obtained. • Chelating resin allows using as low as 1 g/L H 2 SO 4. [ABSTRACT FROM AUTHOR]