• Energy Research

Modifying bitumens to improve their characteristics is one of the ways to increase road pavement durability reducing maintenance costs and environmental issues. In this study the structural and mechanical characteristics of a 50/70 bitumen modified by two different char samples are presented. The choice of char as bitumen modifier fulfils the recent needs for environmental protection. The two char samples come from the pyrolysis of Refuse Derived Fuel (RDF) and waste tyres (WT), respectively. They differ in composition and morphology and their production took place with different yields. Char-modified bitumens revealed increased shear modulus and resistance to mechanical stress as found by rheometry. Artificial aging of these char-modified bitumens unveiled that the bitumen modified by char from WT (WT-char) possessed a certain resilience against aging, with a reduced increase in rigidity upon aging. The anti-aging effect showed by WT-char was attributed to its higher carbon content, which confers higher compatibility with the bitumen chemical nature and presumably a more uniform dispersion within the bituminous structure thanks to the establishment of more effective interactions.

Here we report on the fabrication of a new low-cost transparent cathode based on platinum nanoparticles prepared by a bottom-up synthetic approach. Scanning Electron Microscope (SEM) images showed the platinum nanoparticles homogeneously distributed on a fluorine doped tin oxide conductive glass surface. We demonstrated that, with such a type of cathode, the solar energy conversion efficiency is the same as that obtained with a platinum sputtered counter-electrode, and is more than 50% greater than that obtained with a standard electrode, i.e. one prepared by chlorine platinum acid thermal decomposition, in similar working conditions. Using a special back-reflecting layer of silver, we improved upon the performance of a counter-electrode based on platinum sputtering, achieving an overall solar conversion efficiency of 4.75% at 100 mW cm-2 (AM 1.5) of simulated sunlight.

We review the most advanced methods for the fabrication of cathodes for dye-sensitized solar cells employing nanostructured materials. The attention is focused on metal nanoparticles and nanostructured carbon, among which nanotubes and graphene, whose good catalytic properties make them ideal for the development of counter electrode substrates, transparent conducting oxide, and advanced catalyst materials.

Urban waste management is a hard task: more than 30% of the world’s total production of Municipal Solid Wastes (MSW) is not adequately handled, with landfilling remaining as a common practice. Another source of wastes is the road pavement industry: with a service life of about 10–15 years, asphalts become stiff, susceptible to cracks, and therefore no longer adapted for road paving, so they become wastes. To simultaneously solve these problems, a circular economy-based approach is proposed by the ReScA project, suggesting the use of pyrolysis to treat MSW (or its fractions as Refuse Derived Fuels, RDFs), whose residues (oil and char) can be used as added-value ingredients for the asphalt cycle. Char can be used to prepare better performing and durable asphalts, and oil can be used to regenerate exhaust asphalts, avoiding their landfilling. The proposed approach provides a different and more useful pathway in the end-of-waste (EoW) cycle of urban wastes. This proof of concept is suggested by the following two observations: (i) char is made up by carbonaceous particles highly compatible with the organic nature of bitumens, so its addition can reinforce the overall bitumen structure, increasing its mechanical properties and slowing down the molecular kinetics of its aging process; (ii) oil is rich in hydrocarbons, so it can enrich the poor fraction of the maltene phase in exhaust asphalts. These hypotheses have been proved by testing the residues derived from the pyrolysis of RDFs for the improvement of mechanical characteristics of a representative bitumen sample and its regeneration after aging. The proposed approach is suggested by the physico-chemical study of the materials involved, and aims to show how the chemical knowledge of complex systems, like bituminous materials, can help in solving environmental issues. We hope that this approach will be considered as a model method for the future.

The production and maintenance of road pavements consume resources and produce wastes that are disposed of in landfills. To make more sustainable this activity, we have envisioned a method based on a circular use of residues (oil and char) from municipal solid waste pyrolysis as useful additives for producing improved asphalts and for recycling old asphalts to generate new ones, reducing at the same time the consumption of resources for the production of new road pavements and the disposal of wastes to landfills. This work aims to show the feasibility of the integration of two processes (thermal treatment of municipal solid waste on one side, and that of road pavement production on the other side) where the products deriving from waste pyrolysis become added-value materials to improve the quality of road pavements. In this contribution, we presented the effect of pyrolysis product addition on asphalt binder (bitumen) preparation and aging. Solid and liquid products, deriving from the pyrolysis of two kinds of wastes (refused derived fuel (RDF) and granulated rubber tyre waste), have been used for the preparation of asphalt binder samples. Rheological tests have been performed to determine the mechanical properties of neat asphalt binder (bitumen) and those enriched with pyrolysis derived products. Measurements to evaluate possible anti-aging effects have been also performed. The collected results indicate that char addition strengthens the overall bitumen intermolecular structure while bio-oil addition exerts a rejuvenating activity.