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We examined the national mine waste registries from seven European countries, created to fulfil the requirements of the &ldquo, Mine Waste Directive&rdquo, (2006/21/EC), for their potential use as an initial source of information for the valorisation of specific mine waste deposits for their resource recovery. A set of parameters for mine waste valorisation was defined and divided into three groups: the &ldquo, basic&rdquo, the &ldquo, metal-centric&rdquo, and the &ldquo, material-centric&rdquo, group. The &ldquo, group of 19 parameters considers properties of the mine waste deposit, including the location, history, homogeneity and quantity, among others, while the other two groups relate to the two desired material recovery types. The &ldquo, group of parameters contains the six parameters needed to preliminarily assess the potential to valorise mine waste for metal extraction, while the &ldquo, group contains the nine parameters needed to consider the use of mine waste for the production of different construction materials. National mine waste registries from Slovenia, France, Spain, Italy, UK, Hungary and Portugal were reviewed to determine whether they contain information about each of the parameters. In line with the objectives of the Mine Waste Directive, the national mine waste registries were developed to reduce or prevent environmental damage, and not to enable resource recovery from mine waste. The registries contain most of the information for the parameters in the &ldquo, group, less information for the parameters in the &ldquo, group and almost no information to define the parameters in the &ldquo, group. The conclusion is that national mine waste registries could serve only as an initial source of information, and more detailed information must be obtained from other sources. This misses an opportunity to see these sites as a resource, and not only as a potential source of pollution, given the urgent need to find alternative stocks of metals within the EU (European Union).

Froth flotation is a widely used process for the beneficiation of complex sulphide ores. Thiol collectors (mostly xanthates) are usually effective collectors for sulphide minerals but may have a low selectivity between different sulphide minerals when associated in complex sulphide ores. Additionally, a concern is their suggested harmfulness on human health and impact on the environment. In this study, a green sustainable reagent, butyl-amine cellulose (BAC), was synthesized from hardwood kraft pulp, a renewable abundant resource, for the selective separation of chalcopyrite and sphalerite. The performance evaluation was made using samples of two ores containing chalcopyrite and sphalerite, one was from Panasqueira mine (Portugal) and the other with a different mineral association (from the massive sulphide deposits of the Iberian Pyrite Belt). The study demonstrated that when chalcopyrite is associated with sphalerite, BAC is selective for chalcopyrite, i.e., it is a collector for this mineral and not for sphalerite. The recovery of chalcopyrite in the floated product was a function of interaction between BAC concentration and pulp pH. The study showed that the novel cellulose-based collector had a better performance than the reagents used in the industrial flotation of Panasqueira ore.

Selective collection is a common practice in many countries. However, even in some of those countries there are recyclable materials, like packaging glass, erroneously deposited in the Mixed Municipal Solid Waste (MMSW). In the present paper, a solution is proposed to recover glass from the inert reject of Mechanical and Biological Treatment (MBT) plants treating MMSW aiming at its recycling. The inert reject of MBT (MBTr) plants is characterized by its small particle size and high heterogeneity. The study was made with three real samples of diverse characteristics superimposed mainly by the different upstream MBT. One of the samples (VN) had a high content in organics (approximately 50%) and a particle size smaller than 16 mm. The other two were coarser and exhibited similar particle size distribution but one (RE) was rich in glass (almost 70%) while the other (SD) contained about 40% in glass. A flowsheet was developed integrating drying, to eliminate moisture related with organic matter contamination; magnetic separation, to separate remaining small ferrous particles; vacuum suction, to eliminate light materials; screening, to eliminate the finer fraction that has a insignificant content in glass, and to classify the >6mm fraction in 6-16 mm and >16 mm fractions to be processed separately; separation by particle shape, in the RecGlass equipment specifically designed to eliminate stones; and optical sorting, to eliminate opaque materials. A pilot plant was built and the tests were conducted with the three samples separately. With all samples, it was possible to attain approximately 99% content in glass in the glass products, but the recovery of glass was related with the feed particle size. The finer the feed was, the lower the percentage of glass recovered in the glass product. The results show that each one of the separation processes was needed for product enrichment. The organic matter recovered in the glass product was high, ranging from 0.76% to 1.13%, showing that drying was not sufficient in the tests but that it is a key process for the success of the operation.

Solid waste are today new ores needing innovative separation techniques or adaptations of the current ones used, for instance in mineral processing, for the recovery of materials. “RecGlass” is a device developed to separate materials with similar density but exhibiting different particle shape. It is inspired in the “vanner” and in the “Bartles cross belt” processes but it is applied in dry conditions to separate materials with specific weight slightly above 2 g/cm 3 and particles in the range size 4 to 12 mm. In the work presented, it was applied to the processing of the heavy reject of Mechanical Biological Treatment of mixed Municipal Solid Waste aiming at the recovery of glass, the main constituent of this product, which is landfilled today, and to eliminate the stones, generally the second main inert constituent. The glass particles are predominantly flat while stones are sub-spherical. The core of the equipment is an inclined belt moving upwards. The particles are continuous and steadily fed by a vibrating feeder placed above the belt. Depending on the operational variables such as belt speed and slope and feed position, and also on the belt surface material, the flat particles move upwards and the round ones roll down. In the present paper the equipment is described and the physical principles of the concentration process are explained. Using samples of two different plants it was shown that it is possible to achieve a significant upgrading in glass. With a sample from one plant the glass content was increased from 88% to 92% while with a completely different sample, from another plant, the glass content in the process feed was 59%, attaining 71% in the glass concentrate. The recovery of the glass in the glass concentrate reached more than 80% by removing about 80% of the stones.

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.

The aim of this work is the valorisation of the heavy residual fraction of Mechanical Biological Treatment (MBT) plants fed with mixed Municipal Solid Waste. This product contains a significant amount of glass. In the present work, it was found that the glass content in this product varies from plant to plant. Minimum and maximum values of 33 and 67% were determined. This material is not recycled today, being instead landfilled, because the contamination with other materials is so high that is not possible to process it by optical sorting, which is the end-of-line technology used in glass recycling. Nevertheless, it is possible to upgrade this product by removing a significant percentage of the stones, the main inert contaminant, with a simple and cheap process, RecGlass, which exploits the differences in the shape of glass particles and stones. This paper presents the results of a study carried out with samples of 5 Portuguese MBT plants of different characteristics. The fraction

Mechanical and Biological Treatment (MBT) is an important strategy to manage Municipal Solid Waste (MSW) in Europe. The presence of recyclable materials on MSW depends on different factors such as inefficiencies in the Municipal Solid Waste collecting schemes and to the low level of citizenship environmental education. Among other products, MBT plants produce a residual fraction, named here as heavy residual fraction, that contains a significant amount of packaging glass which in Portugal is currently landfilled. This material is not recycled because it is heavily contaminated with other materials, preventing its processing in Material Recovery Facilities (MRF). In this paper the characterization, including particle size and composition, of the residual fraction of six Portuguese MBT plants is presented. The relevant variables that determine the heavy residual fraction characteristics were identified. It was observed that the MBTr particle size distribution is different and depends mainly on the place on the flowsheet where the MBTr exits the process, which is determined by the type of biological process and by the aperture of the last screen where the product passes through. The content in glass varies from 33 to 83%. These values are mainly related with the upstream glass sorting and with the efficiency of the recovery of the organic fraction which is the glass main contaminant. The second main contaminant is “stones”. The quantity of glass contained in this product in all the plants that will be in operation in Portugal in 2014 was estimated. The work shows that if all the 48,000 of glass could be recovered the Portuguese recycling rate would increase by 4.4%.

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.

Mechanical Biological Treatment inert reject (MBTr) is mostly composed by recyclable glass. Yet, it is usually sent to landfills because, due to the small particle size and high level of particle surface organic contamination, the processes commonly used in glass recycling, like optical sorting, are inefficient in the separation of glass from contaminants. This paper presents the results of a study undertook to characterize MBTr, aiming at the subsequent separation of recyclable glass from contaminants. A representative sample of the reject from a MBT plant was collected. The particle size analysis was carried out and the composition of the different size fractions was determined. It was found that the MBTr sample was composed by almost 80% of recyclable glass. The product is quite fine. About 80% in weight of the product has a particle size lower than 10 mm. However, the size fraction below 2 mm is insignificant since it represents less than 3% in weight and contains less than 1% of the recyclable glass in MBTr. Using methods of image analysis, the shape of each individual particle, separated by material class and by size fraction, was evaluated. It was observed that the average shape of the particles of “stone”, the main contaminant, is significantly different from the shape of other materials, including recyclable glass. Gravity concentration methods may take advantage of the shape of the particles and are thus potentially adequate to recover recyclable glass from MBT.

This article addresses the separation of polyethylene terephthalate (PET) from ternary blends with polyvinyl chloride (PVC) and polystyrene (PS) by froth flotation. The experimental work was carried out with representative samples from post-consumer waste packages collected at drop-off-points. Previous to froth flotation, PET selective wetting was achieved by alkaline treatment followed by surfactant adsorption. For this purpose, an aqueous solution of NaOH and an industrial detergent commonly used for waste plastic washing were tested as alkaline treatment, and calcium lignosulphonate and Hostaphat were tested as surfactants. An enriched product with 98.9% grade in PET and only 0.6% in PVC was recovered in the nonfloated product. The PET recovery in this product was 97% while 96% of PVC and 91% of PS were recovered in the floated product. An analytical method was developed for the quantification of the waste plastic composition. The method was based on the selective dissolution of the plastics in the mixture., Fundação para a Ciência e a Tecnologia (FCT) - POCTI/ECM/60335/2004

The objective of the experimental work described in this paper is the study of the separation of PS (polystyrene) from PET (polyethylene terephthalate) and PVC (polyvinyl chloride) from drop-off points using a fluidized bed separator. This is a low-cost process commonly used in the hydro-classification of mineral ores. Firstly, experimental tests were carried out with artificial granulated samples with different grain sizes, types and sources of plastic ("separability tests"). The particle settling velocities were determined under different operating conditions. Then, based on the results, the laboratory tests continued with real mixtures of waste plastics ("separation tests") and the efficiency of the process was evaluated. From a PET-rich mixture, a concentrate of PS with a 75% grade in PS was produced while the underflow was quite clear from PS (grade less than 0.5% in PS).

With the purpose of reducing the waste generated by end-of-life vehicles (ELVs) by enhancing the recovery and recycling of nonferrous metals, an experimental study was conducted with the finest size fraction of nonferrous stream produced at an ELV shredder plant. The aim of this work was to characterize the nonferrous stream and to evaluate the efficiency of a gravity concentration process in separating light and heavy nonferrous metal particles that could be easily integrated in a ELV shredder plant (in this case study the separation explicitly addressed copper and aluminum separation). The characterization of a sample of the 0-10mm particle size fraction showed a mixture of nonferrous metals with a certain degree of impurity due to the present of contaminants such as plastics. The majority of the particles exhibited a wire shape, preventing an efficient separation of materials without prior fragmentation. The gravity concentration process selected for this study was the wet shaking table and three operating parameters of the equipment were manipulated. A full factorial design in combination with a central composite design was employed to model metals recovery. Two second order polynomial equations were successfully fitted to describe the process and predict the recovery of copper and aluminum in Cu concentrate under the conditions of the present study. The optimum conditions were determined to be 11.1° of inclination, 2.8L/min of feed water flow and 4.9L/min of wash water flow. All three final products of the wet shaking table had a content higher than 90% in relation to one of the metals, wherein a Cu concentrate product was obtained with a Cu content of 96%, and 78% of Cu recovery and 2% of Al recovery.

This paper describes a fuzzy controller that was developed for the control, in real time, of three main variables of the column flotation process. Column flotation is a solid-solid separation process based on the physical and chemical properties of mineral particle surfaces. It is applied to the concentration of low grade ores and to ores that require very fine grinding to achieve mineral liberation. The economic exploitation of the process, guaranteeing the desired final product characteristics from a feed of varying composition, requires a stable operation, which is accomplished through the automatic control of some key process variables. The difficulties encountered in the development of process controllers for this process are related to the lack of reliable measuring devices for the process variables involved, with the non-existence of mathematical dynamical models that can be used in a controller synthesis and with its non-linear and time-varying behaviour. The process and the problems related with its control are briefly explained and the main reasons for fuzzy logic control application are discussed. The real time control system and the fuzzy controller structure and parameters are presented. A general overview of the pilot plant where the experimental work was performed is presented. Finally, results of the experimental work, carried out with the two-phase system (air and water), are summarised and the conclusions are drawn.

The paper describes a software tool, called MSWSampling , to support the evaluation of the solid wastes sampling quality. The software is a random sample generator program that simulates the sampling process of solid wastes, calculating the size of the sample that assures a desired representativeness level with respect to the content of a critical component of the lot to be sampled or the variance of the fundamental error associated to a sample of given size. The solid wastes consists of very different active classes of solid components, which are characterized by their size distribution, specific gravity, weight proportions and shape factors. The results of a case study, the municipal solid wastes that feed a composting plant nearby Lisbon, are presented.

This paper describes a supervisor fuzzy controller of a pilot flotation column. The flotation column processes a clay composed mainly of kaolinite and quartz, reducing the iron grade of the final product to be used in the preparation of ceramic pastes. The main control objective (top level control) is to keep the iron content in the underflow stream close to target specification. At the intermediate level, three process variables are controlled by fuzzy logic inference: collection zone height, air holdup in the collection zone and bias water flow rate. The lower level of control manipulates the process stream flow rates by means of PID controllers.

The objective of the research was to apply froth flotation to separate post-consumer PET (Polyethylene Terephthalate) from other packaging plastics with similar density, in a continuously operated pilot plant. A representative sample composed of 85% PET, 2.5% PVC (Polyvinyl Chloride) and 11.9% PS (Polystyrene) was subjected to a combination of alkaline treatment and surfactant adsorption followed by froth flotation. A mineral processing pilot plant, owned by a Portuguese mining company, was adapted for this purpose. The experimentation showed that it is possible to produce an almost pure concentrate of PET, containing 83% of the PET in feed, in a single bank of mechanical flotation cells. The concentrate grade attained was 97.2% PET, 1.1% PVC and 1.1% PS. By simulation it was shown that the Portuguese recycling industry specifications can be attained if one cleaning and one scavenger stages are added to the circuit.

This paper describes a project under development in Portugal aiming the design of a pilot plant that will be used in the mechanical separation of granulated plastics from packaging waste. The objective of the project is to minimize or, if possible, to eliminate the current practice of manual sorting. The flow-sheet will use mineral processing based techniques, namely gravity concentration and froth flotation. The project also seeks the development of a procedure for the quick and inexpensive analysis of plastics mixtures allowing the future automation of equipment and process control.