Innovative technologies for the recovery of materials from Weee have been developed by Enea on the basis of hydrometallurgical processes, considered advantageous in comparison with traditional pyrometallurgical systems, especially in terms of environmental compatibility.
Alessandro Binetti Traverso
The market globalization, with the widening of consumptions and the emergence of new producers in rising Countries, has accentuated the focus of scholars on a problem that had already been highlighted in the second half of last century but that today cannot be set aside anymore: the shortage of available resources for the sustainability of the industrial development. Scarcity that in the international competition damages Europe and especially Italy in comparison with rising Countries. The domestic indexes of autonomy of materials, that’s to say the ratios between local consumptions and availabilities report a value that, as far as metals are concerned, is on average equal to 0.25 for Europe, therefore with the need of importing three-quarters of what is necessary for one’s own industry. This index even corresponds to 0.01 for Italy, which is compelled to import the almost totality of metals that it uses. The same index, referred to fossil fuels, underlines Europe’s dependence on abroad by 50% of its consumptions, while once more Italy is more severely affected in comparison with the other Community Countries, with an autonomy index equal to 0.15 (85% of consumptions of fossil fuels are satisfied by imports). The problem of the scarcity of resources is going to worsen in the future owing to the convergence of two phenomena: the growing economic development of rising Countries and the success of new industrial players just in those same nations that are also the major producers of some of the main raw materials whose scarcity emerges today. Concerning this, it is worth reminding that today China is the biggest consumer of raw materials, and especially of metals, in the world, with absolute values and percentages constantly growing. The Chinese consumption of copper, for instance, in the course of ten years has grown in impressive way, from 12% of the world total in 1998, to about 40% today.
Europe and critical materials
The European Commission has attentively assessed the problem of the criticality of its raw material provisioning, not only in terms of their absolute availability but also of difficult imports owing to the various aspects of industrial policy with which producer Countries can hinder the free circulation of goods. Concerning this, it is emblematic the case of Rare Earths, a whole of elements today become of strategic importance for the manufacturing of high added value products, including those of the electronic industry, from portable phones to PC and to optical fibres, up to photovoltaic panels and lithium batteries for electrical cars. The fact that China is by far the biggest producer of rare earths in the world, with 97% of the total production, can nothing but worry for the possible consequences on the fair competition, just in the productions with highest added value, between the whole of Western nations and China. Concern that has already caused, in the recent past, various denunciations to China for the violation of the free trade rules of WTO by USA, EU and Japan. But rare earths are only one among the strategic raw materials for western industry that show provisioning criticalities. The purposely created work team, entrusted by the European Commission with the execution of a study about raw materials of strategic importance for industry, has in fact identified 14 elements and groups of elements in all of which today the provisioning criticality is perceived, coupled with their difficult replacement with other materials. Besides rare earths, platinoids are included in the same category of critical materials together with cobalt, tantalum, gallium, indium, antimony, beryl, tungsten, fluorite, germanium, graphite, magnesium and niobium. For all these materials, the critical supply is ascribable both to their objective scarcity and to the extraction difficulties, together with problems concerning the protectionist strategies accomplished by some producers of raw materials to favour local manufacturing enterprises. Moreover, in other cases provisions are menaced by the particular political situations of some Countries, like Congo, which is the major producer of cobalt and tantalum, troubled by fierce internal wars.
In comparison with rising Countries that produce raw materials, Europe is disadvantaged, not only for the minor availability of its natural resources, but also for the troubles met in the extraction activities owing to the high urbanization and to the complex structures of transports that make the territory unsuitable for the exploitation of the subsoil, as well as due to the more severe environmental regulations that the Community has adopted. For all these reasons, the recovery and the recycling of materials starting from worn-out products represent for Europe the most important open pit mine on which the Community can rely. It is therefore natural that the European strategy on raw materials has paid utmost attention to the separate collection of wastes and to the recovery of materials, especially of those coming from waste electrical and electronic equipment (Weee). Concerning this, to evaluate the importance that the recovery of Weee can assume, it is worth noticing that the quantity of electronic cards recoverable at the product life end is, in Italy only, in the order of 3,500-4,000 tons. Nevertheless, to make the recovery process efficient, it is necessary to improve the organization of the collection that today, still regarding Italy, reaches only 30% of wastes, against 70% of Finland. At the same time we must also improve the efficiency of the process of waste treatment and of recovery of materials, which is around 30%, too. The overall result of the waste collection and of the material recovery corresponds then to the product of the two percentages and reaches around 10% in comparison with the materials used in the initial production, showing how high is the margin for further progresses towards this direction. The most advanced European Countries have decidedly worked at the exploitation of wastes, having developed effective technologies for the recovery of materials, to the extent that some of them, like Germany, import Weee coming from other Countries, including Italy. This demonstrates that the recovery and recycling industry can be a business with high added value, able in addition to produce employment. Also for this reason and with the target of promoting a sustainable economy, the European Community has fixed for 2050 a set of targets that provide for a recycling amounting to 15% for industrial wastes, to 34% of urban wastes and 100% for electrical and electronic wastes.
Moreover, with the Framework Directive 2008/98/EC they have indicated the measures aimed at orienting the production of goods towards the direction of the so called 4 R:
– Reduction of produced wastes (improving the organization of productive processes)
– Reuse of wastes (through the repair and reuse of still functioning products)
– Recycling of wastes (converting the recovered materials into new products)
– Recovery of wastes (for instance using them for the energy generation)
As explains Roberto Morabito, manager of Environmental Technologies Technical Unit of Enea, the most used technology for the extraction, production and purification of metals is the pyrometallurgical, a traditional process through which you supply thermal energy to the base material to obtain a determinate transformation or chemical-physical reaction. Cutting-edge pyrometallurgical plants have been implemented in several European Countries and especially in Germany where there are big poles of this type for the waste treatment, which process several Weee coming from Italy, too. Besides the relative simplicity of these treatment processes, it is however worth underlining the problems of environmental compatibility for pollution, which is generated with the typically “hot” use of this technology. It is also for this reason that Enea has staked on the development of “cold” innovative technologies recalling another treatment modality known for a long time: hydrometallurgy. This technology, compared to pyrometallurgy that is an open loop process, is instead a closed loop process, not polluting and environment-friendly. Hydrometallurgy, in fact, includes a whole of technical-chemical and chemical-physical techniques, in liquid phase and at low temperature, used for the treatment of industrial machining residues or wastes of various kinds, finding an interesting application field with notable development potentialities in the recovery of critical materials from Weee, such as precious metals and rare earths.
– The hydrometallurgical process, once the material has been reduced to a small size with crushing and grinding operations, includes two main phases:
– Dissolution of the solid material (leaching) that occurs by making the solid to be treated react with an opportune solution able to dissolve some or all chemical elements contained in the starting material
– Separation and purification of the metals contained in the liquid solution obtained through the leaching process, acting also through the variation of some parameters like temperature or the pH of the solution.
– These two phases can be completed by other operations such as precipitation/crystallization, ion exchange, extraction with solvent and electrodeposition, in order to accomplish a recovery process characterized by a range of advantages in comparison with the more traditional pyrometallurgical technology:
– High selectivity that allows the separation of metals with similar properties
– Possibility of treating wastes, rejects and industrial residues
– Possibility of obtaining products with high purity degree
– Simple, flexible, versatile and easily automated plants
– Plants with low environmental impact
– Low energy consumption
– Low operation temperature
– Possibility of treating economically low metal concentrations
Innovative hydrometallurgy solutions have been developed by Enea in the ambit of its research activities. In the Enea Research Centre at Trisaia (Matera-Italy) they have in fact implemented a pilot plant for the extraction of rare earths from rough mineral, which uses an extraction process with solvent. This solution is interesting from the technological point of view, because it fills a national gap, since previous plants of this type did not exist in Italy and we missed hydrometallurgical competences. The pilot plant at Trisaia is not however the only solution based on the use of hydrometallurgy at which Enea researchers have worked. As Roberto Morabito explains, within next year it will be operating in the Casaccia Research Centre of Enea an experimental hydrometallurgy plant applied to Weee, it too implemented by Enea, whose project was funded by Miur (Education University and Research Ministry) amounting to over 4 million Euros. Besides a part concerning the sustainable tourism, the project includes also interventions for the recovery of “second raw materials” from Weee. The plant implementation occurs after the development of a hydrometallurgical process for the recovery of materials from electronic cards, for which patent application has been recently submitted and which describes a methodology for the recovery from these matrixes of gold, silver, tin and lead, metals with high intrinsic and strategic value. “The target at which our unit has been working for years”, adds Roberto Morabito, “is the integrated management of electronic wastes through the implementation of an industrial symbiosis platform and of a pilot plant for the recovery of raw materials from Weee through the hydrometallurgical technology”. The “cold” extraction process, developed by Enea, shows absolutely innovative characteristics permitting, unlike conventional plants with pyrometallurgical technology prevailingly used in Germany, the recovery of a high number of metals with high purity degree, as well as with low energy costs and zero emissions into the atmosphere. The plant under implementation is designed with modules, so that it can be used also for the development and the optimization of useful process technologies for the treatment of matrixes of other nature (worn-out fluorescence lamps, LCD monitors etc). It appears then as the ideal testing bench for the development of recovery processes of metals of strategic interest at disposal of the enterprises operating in the waste treatment sector.