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The separation of plastic wastes in mechanical recycling plants is the process that ensures high-quality secondary raw materials. An innovative device employing a wet technology for particle separation is presented in this work. Due to the combination of the characteristic flow pattern developing within the apparatus and density, shape and size differences among two or more polymers, it allows their separation into two products, one collected within the instrument and the other one expelled through its outlet ducts. The kinematic investigation of the fluid flowing within the apparatus seeded with a passive tracer was conducted via image analysis for different hydraulic configurations. The two-dimensional turbulent kinetic energy results strictly connected to the apparatus separation efficacy. Image analysis was also employed to study the behaviour of mixtures of passive tracer and plastic particles with different physical characteristics in order to understand the coupling regime between fluid and solid phases. The two-dimensional turbulent kinetic energy analysis turned out to be fundamental to this aim. For the tested operating conditions, two-way coupling takes place, i.e., the fluid exerts an influence on the plastic particle and the opposite occurs too. Image analysis confirms the outcomes from the investigation of the two-phase flow via non-dimensional numbers (particle Reynolds number, Stokes number and solid phase volume fraction).

This chapter presents an original device for the hydraulic separation of plastic polymers from mixtures. The separation process that takes place within the separator involves the interaction between two phases, that is, solid particles acting as the dispersed (or dense) phase and water acting as the continuous phase. Due to the combination of the fluid flow pattern developing within the apparatus and density, shape, and size differences among plastic particles, the device allows their separation into two products, one collected within the instrument and the other one expelled through its outlet ducts. An extensive experimental campaign was conducted to investigate the effectiveness of the apparatus, using two geometric arrangements, nine hydraulic configurations, and three selections of polymers at three stages of a material life cycle. The experimental data were also employed to validate a numerical model developed within the framework of Computation Fluid Dynamics. For the tested operating conditions, two-way coupling takes place, that is, the fluid exerts an influence on the plastic particle and the opposite occurs too. Image analysis confirms the outcomes from the investigation of the two-phase flow via nondimensional numbers (particle Reynolds number, Stokes number, and solid phase volume fraction). The separation results were evaluated in terms of grade and recovery of a useful material. Under the proper hydraulic configurations, the experimentation showed that it is possible to produce an almost pure concentrate of polyethylene terephthalate (PET) from a mixture of 85% PET and 15% polycarbonate (PC) (concentrate grade and recovery equal to 99.5% and 95.1%), 85% PET and 15% polyvinyl chloride (PVC) (concentrate grade and recovery equal to 97.9% and 100.0%), and 85% PET and 15% polylactic acid (PLA) (concentrate grade and recovery equal to 91.4% and 86.1%).

This paper presents an original device for the separation of plastic polymers from mixtures. Due to the combination of a characteristic flow pattern developing within the apparatus and density, shape and size differences among two or more polymers, this device allows their separation into two products, one collected within the instrument and the other one expelled through its outlet ducts. Experimental tests have been conducted to investigate the effectiveness of the apparatus, using two geometric arrangements, nine hydraulic configurations and three selections of polymers at three stages of a material life cycle. Tests with samples composed of a single typology of polymer have been used to understand the interaction between the particles and the carrying fluid within the apparatus in different hydraulic configurations and geometric arrangements. Multi-material tests are essential to simulate the real conditions in an industrial recycling plant. The separation results have been evaluated in terms of grade and recovery of a useful material. Under the proper hydraulic configurations, the experimentation showed that it is possible to produce an almost pure concentrate of Polyethylene Terephthalate (PET) from a mixture of 85% PET and 15% Polycarbonate (PC) (concentrate grade and recovery equal to 99.5% and 95.1%) and a mixture of 85% PET and 15% Polyvinyl Chloride (PVC) (concentrate grade and recovery equal to 97.9% and 100.0%). It is further demonstrated that almost pure concentrates of PVC and PC can be produced from a mixture of 85% PVC and 15% PC (PVC grade and recovery equal to 99.9% and 99.7%) and a mixture of 85% PC and 15% PVC (PC grade and recovery equal to 99.0% and 99.5%).

The separation process within a mechanical recycling plant plays a major role in the context of the production of high-quality secondary raw materials and the reduction of extensive waste disposal in landfills. Traditional plants for plastic separation employ dry or wet processes that rely on the different physical properties among the polymers. The hydraulic separator is a device employing a wet technology for particle separation. It allows the separation of two-polymer mixtures into two products, one collected within the instrument and the other one expelled through its outlet ducts. Apparatus performance were analyzed as a function of fluid and solid flow rates, flow patterns developing within the apparatus, in addition to the density, shape, and size of the polymers. For the hydraulic configurations tested, a two-way coupling takes place where the fluid exerts an influence on the plastic particles and the opposite occurs too. The interaction between the solid and liquid phases determines whether a certain polymer settles within the device or is expelled from the apparatus. Tests carried out with samples of increasing volumes of solid particles demonstrate that there are no significant differences in the apparatus effectiveness as far as a two-way interaction takes place. Almost pure concentrates of Polyethylene Terephthalate (PET), Polyvinyl Chloride (PVC), and Polycarbonate (PC) can be obtained from a mixture of traditional polymers. Tests conducted on Polylactic Acid (PLA) and Mater-Bi® samples showed that the hydraulic separator can be effectively employed to separate bio-plastics from conventional plastics with remarkable grade and recovery.

Traditional plants for plastic separation in homogeneous products employ material physical properties (for instance density). Due to the small intervals of variability of different polymer properties, the output quality may not be adequate. Sensing technologies based on hyperspectral imaging have been introduced in order to classify materials and to increase the quality of recycled products, which have to comply with specific standards determined by industrial applications. This paper presents the results of the characterization of two different plastic polymers--polyethylene terephthalate (PET) and polyvinyl chloride (PVC)--in different phases of their life cycle (primary raw materials, urban and urban-assimilated waste and secondary raw materials) to show the contribution of hyperspectral sensors in the field of material recycling. This is accomplished via near-infrared (900-1700 nm) reflectance spectra extracted from hyperspectral images acquired with a two-linear-spectrometer apparatus. Results have shown that a rapid and reliable identification of PET and PVC can be achieved by using a simple two near-infrared wavelength operator coupled to an analysis of reflectance spectra. This resulted in 100% classification accuracy. A sensor based on this identification method appears suitable and inexpensive to build and provides the necessary speed and performance required by the recycling industry.

This paper proposes the use of factorial experimental design as a standard experimental method in the application of froth flotation to plastic separation instead of the commonly used OVAT method (manipulation of one variable at a time). Furthermore, as is common practice in minerals flotation, the parameters of the kinetic model were used as process responses rather than the recovery of plastics in the separation products. To explain and illustrate the proposed methodology, a set of 32 experimental tests was performed using mixtures of two polymers with approximately the same density, PVC and PS (with mineral charges), with particle size ranging from 2 to 4 mm. The manipulated variables were frother concentration, air flow rate and pH. A three-level full factorial design was conducted. The models establishing the relationships between the manipulated variables and their interactions with the responses (first order kinetic model parameters) were built. The Corrected Akaike Information Criterion was used to select the best fit model and an analysis of variance (ANOVA) was conducted to identify the statistically significant terms of the model. It was shown that froth flotation can be used to efficiently separate PVC from PS with mineral charges by reducing the floatability of PVC, which largely depends on the action of pH. Within the tested interval, this is the factor that most affects the flotation rate constants. The results obtained show that the pure error may be of the same magnitude as the sum of squares of the errors, suggesting that there is significant variability within the same experimental conditions. Thus, special care is needed when evaluating and generalizing the process.

Froth flotation is a promising technique to separate polymers of similar density. The present paper shows the need for performing kinetic tests to evaluate and optimize the process. In the experimental study, batch flotation tests were performed on samples of ABS and PS. The floated product was collected at increasing flotation time. Two variables were selected for modification: the concentration of the depressor (tannic acid) and airflow rate. The former is associated with the chemistry of the process and the latter with the transport of particles. It was shown that, like mineral flotation, plastics flotation can be adequately assumed as a first order rate process. The results of the kinetic tests showed that the kinetic parameters change with the operating conditions. When the depressing action is weak and the airflow rate is low, the kinetic is fast. Otherwise, the kinetic is slow and a variable percentage of the plastics never floats. Concomitantly, the time at which the maximum difference in the recovery of the plastics in the floated product is attained changes with the operating conditions. The prediction of flotation results, process evaluation and comparisons should be done considering the process kinetics.

The recycling of e-waste in general allows the recovery of valuable materials, which can be reused as secondary raw materials. This implies, however, to adopt reliable treatment processes to achieve specific standard characteristics. Actually, the market standards are very strict and strongly affect the economic value of recovered materials. In particular, waste refrigerators recycling allows the recovery of different plastic materials together with metallic fractions (ferrous and non ferrous), which economic value is considerably increasing in the last years. Only in Italy, in 2010 approximately 66,000 t of waste refrigerators were collected for recycling. An efficient recycling treatment could assure about 85% of recovery rate. In this paper, a model to control and characterize the materials recovered from mechanical recycling of cabinets dismantled from of waste refrigerators is proposed. The treatment flow sheet consists of various separation and comminution operations. A mathematical model was implemented to determine a partition function, utilizing data obtained from the treatment of 100 waste refrigerator carcasses, carrying out mass balance of recovered materials. The partition function was adopted to determinate control parameter to assess the quality of the recovered products, and, therefore, of the applied technologies. The results shown as the best recovery rate of waste refrigerator carcasses were reached for ferrous metals (97.5%) together with high purity (more than 98%). Also other metals reached a good quality (about 87% for non-ferrous metals, 92% for mixed recyclable plastics), but with lower recovery rates.

Recycling of plastic materials is a rapidly developing discipline because of environmental awareness, the need to conserve materials and energy, and the growing demand to increase the production economy. The main problem in plastics recovery and recycling is related to the variety of plastic wastes, even if selective collection occurs. Therefore, plastic materials can be recycled either as mixtures or as single types, separating the different typologies by their physical (size, specific mass, etc.) and/or chemical properties. However, separation of plastics in single typologies by traditional processes and devices is difficult due to their typical low variability in properties. This paper presents a new research development for recycling industry: the Multidune separator. This is a device constructed from a sequence of parallel semi-cylindrical tubes of transparent plastic welded together in a plane. The lower half is shifted laterally and then fixed relative to the upper half. Flow is then induced in the lateral direction normal to the axis of the tubes, creating a main flow channel and two recirculation zones. This apparatus creates a differential transport of particles of low specific mass, near to 1 g/cm 3 , allowing their separation. The flow field in the Multidune separator is studied via Particle Tracking Velocimetry (PTV). Eulerian analysis of the data is performed to gather information about the fluid-dynamics features established by different hydraulic heads at the inlet of the Multidune. Preliminary tests on monomaterial samples have been performed, varying several operative parameters to determine the best set of values. Therefore, separation tests have been executed on composite samples, obtaining satisfactory results in terms of plastic separation feasibility.

Worldwide legislation coming into force requires considering new waste streams in order to achieve higher targets for material recovery and recycling. It is necessary, therefore, to manage waste materials in which different components are linked together and contaminants of various origins are present. Waste materials thus need to be treated that have a complex and often unknown composition and present different structural, morphological, and chemical properties. The physical and chemical characterization of solid waste is an essential step for the development of suitable treatment strategies, aimed at the recovery of one or more waste components. Scanning electron microscopy appears to be in most cases very helpful for waste characterization, providing information on material size, shape, structure, texture, distribution, and composition. Examples of waste characterization through scanning electron microscopy, finalized to material recovery, are reported. The waste materials taken into consideration incl...

ERECON (2014) Strengthening the European rare earths supply chain: Challengesand policy options. Kooroshy, J., G. Tiess, A. Tukker, and A. Walton (eds.).; Policy recommendations:1.Maintaining and strengthening the European Rare Earth Elements (REE) skills and knowledge base through research funding, science and technology education and international cooperation.Without cutting-edge research and technical expertise, a European high-tech REE industry cannot flourish. The EC and Member States should support funding for research grants, scholarships, and training networks, and enhance European and international cooperation through coordinated calls, researcher exchanges, and joint high-level conferences.2.Creating the basis for informed decision-making on REEs through a European Critical Materials Observatory.Mapping and monitoring of REE supply chains is necessary for informed decision-making. Expertise in Europe could be pooled in a virtual Critical Materials Observatory that provides the public with consistent and authoritative knowledge on REEs (e.g., information on advanced exploration projects, prices, key demand and supply trends, and the urban mine potential).3.Support promising technologies through funding industry-led pilot plants for innovative HREE processing.The EC, industry and Member States should accelerate the commercialization and scaling up of key technologies through co-financing industry-led pilot plants. This should include pilots for REE recovery from heavy rare earths-rich minerals, direct-alloy recycling routes, process and sensor equipment for REE recycling, and REE recovery from industrial residues.4.Levelling the playing field for European HREE exploration through co-funding for prefeasibility and bankable feasibility studies.Support from federal and state governments in the U.S., Australia and Canada has played a critical role in advancing project exploration. The EC and Member States should evaluate possibilities for supporting the extensive R&D necessary for pre-feasibility and bankable feasibility studies, to avoid high quality deposits in Europe simply going unexplored.5.Making waste management REE-friendly through eco-design, incentive schemes for collecting priority waste products, and streamlining policy and waste regulation.The EC and Member States should promote recycling-friendly design to help identify and recover REE components in waste more easily. Potential incentives for stimulating REE waste collection should be evaluated and the shipment of REE wastes should be facilitated. More consistency should also be created in implementing and applying existing waste regulations.6.Boost supply security and de-risk strategic REE investment cases through enhanced cooperation among European end-users and other stakeholders.Leading end-users should engage in strategic cooperation across industry and with governments. This could include setting up a voluntary European ‘critical raw materials fund’, establishing a ‘European Resource Alliance’ similar to the German Rohstoffallianz, and convening a high-level taskforce to examine ways in which public funding could support resilient REE supply chains for Europe.

The results of a vitrification test carried out on potentially contaminated sediment samples collected in different Italian coastal areas (Lazio, Sardinia, and Tuscany Regions) are presented. One sample has physical and chemical properties compatible with reuse for production of industrial hollow glass. Other three samples were selected and mixed in a batch simulating a composition close to that of mineral wool products. The results of the present investigation indicate that the inertization of these hazardous material is possible and their reuse as secondary raw material for the production of

Overall sampling of the sediments in the Adriatic Sea at the mouth of the Isonzo (Soca) River in Italy has permitted updating of the extent and level of mercury contamination. The lsonzo River transports mercury-bearing residues from the ldrija mine (Slovenia); that area is contaminated due to the mining of cinnabar (HgS). The mercury mine started operations in the 15th century and was finally shut down in the 1980s because of the decreased demand for mercury. An attempt was made to remove mercury from the contaminated sediments by thermal desorption, with the aim of ascertaining whether low temperature and short residence time could be suitable parameters for sediment cleanup if future needs should so require. To date, no studies have been done on the health of the Italian population living in the Gulf of Trieste area; hence there is no known correlation between the anomalous mercury content of the sediments and symptoms attributable to the ingestion of even small quantities of mercury. Desorption times of about 20 to 30 minutes, at temperatures ranging from 325° C to 350° C, yielded residues with a mercury content below the limit imposed by Italian regulations for contaminated soils and sediments (5 ppm). The air and the mercury vapors driven off during roasting were treated before being released to the atmosphere.

Recycling of plastics is a big issue in terms of environmental sustainability and of waste management. The development of proper technologies for plastic recycling is recognised as a priority. To achieve this aim, the technologies applied in mineral processing can be adapted to recycling systems. In particular, the improvement of comminution technologies is one of the main actions to improve the quality of recycled plastics. The aim of this work is to point out suitable comminution processes for different types of plastic waste. Laboratory comminution tests have been carried out under different conditions of temperature and sample pre-conditioning adopting as refrigerant agents CO2 and liquid nitrogen. The temperature has been monitored by thermocouples placed in the milling chamber. Also different internal mill screens have been adopted. A proper procedure has been set up in order to obtain a selective comminution and a size reduction suitable for further separation treatment. Tests have been performed on plastics coming from medical plastic waste and from a plant for spent lead batteries recycling. Results coming from different mill devices have been compared taking into consideration different indexes for representative size distributions. The results of the performed tests show as cryo-comminution improves the effectiveness of size reduction of plastics, promotes liberation of constituents and increases specific surface size of comminuted particles in comparison to a comminution process carried out at room temperature.

The proper design of a product life cycle may contribute both to the optimization of primary raw material uses and to the reduction of waste environmental impacts. Recycling may enter the life cycle of materials in the contexts of production of secondary raw materials and in the reduction of waste extensive disposal in landfills. Tradition plants for plastic separation in homogeneous products employ material physical properties (for instance density). Due to the variability of the properties of various polymers in reduced intervals, the output quality may not be adequate enough. Sensing technologies based on hyperspectral imaging enter this framework being suitable to separate materials and increase the quality of recycled products, which have to comply with specific standards determined by industrial applications. This paper presents the results of the characterization of two different typologies of plastics, namely PET and PVC, in some phases of their life cycle (raw materials, waste and regenerate conditions) to show the contribution of hyperspectral methods in the field of material recycling. This is accomplished via near-infrared (900-1700 nm) reflectance spectra acquired with a linear spectrometer. Though reflectance values depend on many factors such as the characteristics and the thickness of the materials, the lighting conditions, the characteristics of the instrumentation used, and the background, characteristic spectral profiles of PET and PVC samples have been obtained allowing a robust statistical analysis to be developed. Wavelengths 1200 nm and 1650 nm result to be the most suitable for sample classification.

This research pointed out a methodology for selecting flowing items by optical sensors following each object during its movement, recording changes in optical properties and recognizing the class of each object. The possibility of distinguishing two metals was proven as a function of selective response to illumination with different wavelengths. The prediction of the trajectory of an object was assessed by a procedure that calculates the position of an object after leaving the field of vision. A ray-tracing software was produced and tested by an experimental phase. The methodology for object recognition and trajectory prediction was set-up and verified.

Recovery of useable plastics from post-consumer and manufacturing waste remains a major recycling challenge. The global consumption of plastics was reported to be 230 million tonnes in 2005 (PlasticsEurope 2007a) of which 47.5 million tonnes were produced in Europe (25 European Union countries + Norway and Switzerland). Of the European production, only 22 million tonnes were reported as having been collected. Of this collected waste, 4 million tonnes were recycled as a manufacturing feedstock (18%) and 6.4 million tonnes went into energy recovery (29%), with the balance (11.6 million tonnes) probably being disposed in landfills (PlasticsEurope 2007b). The recycling of plastics is a process essential to reduce the efflux of materials to landfills and to decrease the production of raw materials. In recent years awareness of the importance of environmental protection has led to the development of different techniques for plastic recycling. One issue related to the recycling of this material is the presence in the market of many types of plastics (polymers with additives), often with similar characteristics that make them difficult to differentiate in the recovery phase. The separator “Multidune” is a hydraulic separator by density. Its name derives from the characteristic undulate profile of the channel where separation occurs. The channel is constructed from a sequence of closed parallel cylindrical tubes welded together in plane which are then sliced down the lateral mid-plane and the lower complex is laterally shifted relative to the upper complex. The Multidune allows solid particle separation according to their specific weight and the velocity field establishing within the apparatus. Previous investigations (De Sena et al., 2008; Moroni et al. 2008) suggested the flow within the Multidune is organized into three main patterns. Principally, a longitudinal transport flow takes place, where the velocity is high. A particle belonging to this region can move from one camera to another. The second region is the lower recirculation zone with high values of the vorticity field. Particles belonging to this region undergo the vertical impulse of the fluid. The thrust is proportional to the vertical velocity component and, in conjunction with gravity and buoyancy, determines the destiny of a particle. If the thrust is larger than the net weight of the particle, an interaction with the principal transport flow occurs and, consequently, the particle will move to the following chamber. The third region is the upper recirculation zone whose dimensions are smaller than the other recirculation zone. If a

Hazardous waste management should fulfil the following three main goals: (i) to protect human health and the environment, (ii) to reduce waste while conserving energy and natural resources and (iii) to reduce or eliminate the volume of waste to dispose of. The last two of these goals may derive from recycling, which aims at reducing raw materials and energy consumption and decreasing the volume of waste materials that must be treated and disposed of.

The recovery of high-quality plastic materials is becoming an increasingly challenging issue for the recycling sector. Technologies for plastic recycling have to guarantee high-quality secondary raw material, complying with specific standards, for use in industrial applications. The variability in waste plastics does not always correspond to evident differences in physical characteristics, making traditional methodologies ineffective for plastic separation. The Multidune separator is a hydraulic channel allowing the sorting of solid particles on the basis of differential transport mechanisms by generating particular fluid dynamic conditions due to its geometric configuration and operational settings. In this paper, the fluid dynamic conditions were investigated by an image analysis technique, allowing the reconstruction of velocity fields generated inside the Multidune, considering two different geometric configurations of the device, Configuration A and Configuration B. Furthermore, tests on mono- and bi-material samples were completed with varying operational conditions under both configurations. In both series of experiments, the bi-material samples were composed of differing proportions (85% vs. 15%) to simulate real conditions in an industrial plant for the purifying of a useful fraction from a contaminating fraction. The separation results were evaluated in terms of grade and recovery of the useful fraction.

A new approach is suggested for the purposes of obtaining a proper character-distribution pattern of a particle set. Different methods of modeling the series of size characterization data are examined. Fourier analysis is applied to detail new parameters (features) for enhancing the differences between size distributions under different comminution operating conditions. Size distribution relating to a set of comminuted particles is processed as a signal (size vector) to extract the feature set. The results are compared to provide an insight into the effectiveness of each data analysis method. In particular, some of the Fourier series sine-coefficient values, relating to the size vector of a particle set, can represent the post-comminution size-distribution pattern. For example, size distribution following cryogenic comminution under different temperature conditions can be modeled using a second-order equation function of four selected Fourier analysis sine coefficients.

Minimisation of waste to landfilling is recognised as a priority in waste management by European rules. In order to achieve this goal, developing suitable technologies for waste recycling is therefore of great importance. To achieve this aim the technologies utilised for mineral processing can be taken into consideration to develop recycling systems. In particular comminution and separation processes can be adopted to recover valuable materials from composite waste. In this work the possibility of recycling pharmaceutical blister packaging has been investigated. A suitable comminution process has been applied in order to obtain the liberation of the plastic and aluminium components. Experiments of electrical separation have been carried out in order to point out the influence of the process parameters on the selections of the different materials and to set up the optimum operating conditions.

The exponential growth of photovoltaic (PV) installations highlights the necessity to cope with the environmental impacts which could raise from wrong practices for disposal of end-of-life PV modules. In fact, their possible disposal in landfills would represent a loss of materials and energy, as PV modules are goods that can become very useful even at the end of their life. In order to improve the valorisation of waste coming from end-of-life PV modules and of materials they contain, high value recycling processes are needed. These solutions differ from other end-of-life management alternatives, that are generally more simple and economical, like for example the treatment of the PV modules in a recycling plant for laminated glass or their disposal at a landfill after the recovery of the aluminium frame and a pre-treatment in a municipal incineration plant. All these low value approaches have in common the loss of valuable resources, represented by high value materials and components contained in PV modules (wafer/silicon, indium, tellurium and so on), which inevitably would end their life cycle in a landfill, without being adequately recovered. Differently, some separation and treatment processes have been recently developed, adopting machines and also plants deriving from traditional mineral processing, which allow recovering and recycling of precious metals and materials.