CO2 sensing properties of electro-spun Ca-doped ZnO fibres.

The availability of low-cost, high-performing sensors for carbon dioxide detection in the environment may play a crucial role for reducing CO2 emissions and limiting global warming. In this study, calcium-doped zinc oxide nanofibres with different Ca to Zn loading ratios (1:40 or 1:20) are synthesised via electro-spinning, thoroughly characterised and, for the first time, tested as an active material for the detection of carbon dioxide. The results of their characterisation show that the highly porous fibres consist of interconnected grains of oxide with the hexagonal wurtzite structure of zincite. Depending on the Ca:Zn loading ratio, calcium fully or partly segregates to form calcite on the fibre surface. The high response of the sensor based on the fibres with the highest Ca-doping level can be attributed to the synergy between the fibre morphology and the basicity of Ca-ion sites, which favour the diffusion of the gas molecules within the sensing layer and the CO2 adsorption, respectively.

Effects of carbon-based conductive materials on semi-continuous anaerobic co-digestion of organic fraction of municipal solid waste and waste activated sludge.

Organic fraction of municipal solid waste (OFMSW) and waste activated sludge (WAS) are the most produced organic waste streams in urban centres. Their anaerobic co-digestion (AcoD) allows to generate methane (CH4) and digestate employable as renewable energy source and soil amendment, respectively, fully in accordance with circular bioeconomy principles. However, the widespread adoption of such technology is limited by relatively low CH4 yields that fail to bridge the gap between benefits and costs. Among strategies to boost AcoD of OFMSW and WAS, use of conductive materials (CMs) to promote interspecies electron transfer has gained increasing attention. This paper presents one of the few experimental attempts of investigating the effects of four different carbon(C)-based CMs (i.e., granular activated carbon - GAC, graphite - GR, graphene oxide - GO, and carbon nanotubes - CNTs) separately added in semi-continuous AcoD of OFMSW and thickened WAS. The presence of C-based CMs has been observed to improve CH4 yield of the control process. Specifically, after 63 days of operation (concentrations of GAC and GR of 10.0 g/L and of GO and CNTs of 0.2 g/L), 0.186 NL/gVS, 0.191 NL/gVS, 0.203 NL/gVS, and 0.195 NL/gVS of CH4 were produced in reactors supplemented with GAC, GR, GO, and CNTs, respectively, compared to 0.177 NL/gVS produced in the control process. Likewise, at the end of the test (i.e., after 105 days at concentrations of C-based CMs half of the initial ones), CH4 yields were 0.193 NL/gVS, 0.201 NL/gVS, 0.211 NL/gVS, and 0.206 NL/gVS in reactors supplemented with GAC, GR, GO, and CNTs, respectively, compared to 0.186 NL/gVS of the control process. Especially with regard to GR, GO, and CNTs, results obtained in the present study represent a significant advance of the knowledge on the effects of such C-based CMs to realistic and scalable AD process conditions respect to previous literature.

Hybrid Fluoro-Based Polymers/Graphite Foil for H2/Natural Gas Separation.

Membrane technologies and materials development appear crucial for the hydrogen/natural gas separation in the impending transition to the hydrogen economy. Transporting hydrogen through the existing natural gas network could result less expensive than a brand-new pipe system. Currently, many studies are focused on the development of novel structured materials for gas separation applications, including the combination of various kind of additives in polymeric matrix. Numerous gas pairs have been investigated and the gas transport mechanism in those membranes has been elucidated. However, the selective separation of high purity hydrogen from hydrogen/methane mixtures is still a big challenge and nowadays needs a great improvement to promote the transition towards more sustainable energy source. In this context, because of their remarkable properties, fluoro-based polymers, such as PVDF-HFP and NafionTM, are among the most popular membrane materials, even if a further optimization is needed. In this study, hybrid polymer-based membranes were deposited as thin films on large graphite surfaces. Different weight ratios of PVDF-HFP and NafionTM polymers supported over 200 µm thick graphite foils were tested toward hydrogen/methane gas mixture separation. Small punch tests were carried out to study the membrane mechanical behaviour, reproducing the testing conditions. Finally, the permeability and the gas separation activity of hydrogen/methane over membranes were investigated at room temperature (25 °C) and near atmospheric pressure (using a pressure difference of 1.5 bar). The best performance of the developed membranes was registered when the 4:1 polymer PVDF-HFP/NafionTM weight ratio was used. In particular, starting from the 1:1 hydrogen/methane gas mixture, a 32.6% (v%) H2 enrichment was measured. Furthermore, there was a good agreement between the experimental and theoretical selectivity values.

ESCAPE approach for the sustainability evaluation of spent lithium-ion batteries recovery: Dataset of 33 available technologies.

Recovering critical raw materials from end-of-life batteries is mandatory to limit the need of virgin resources in the long-term. However, most of the recycling of lithium-ion batteries (LIBs) technologies are still in an infancy stage. As a result, to date, only few studies focus on Life Cycle Assessment (LCA) of the proposed processes, presenting limited results. This paper reports the methodology and data resulting from sustainability evaluation of 33 different technologies for spent LIBs recovery, on the basis of the availability of information, identified in literature. The ESCAPE (standing for Evaluation of Sustainability of material substitution using CArbon footPrint by a simplified approach) method is based on the use of only two parameters: the embodied energy and the carbon footprint. These parameters are calculated for all the process steps of each technology. Using the ESCAPE approach, the data about energies and emissions associated with the electricity consumption for thermal and mechanical treatments and chemicals and water use are calculated for all the 33 selected technologies, referring to a recent work (Fahimi et a., 2022), which only presents the results. In addition, ESCAPE tool is used to evaluate and discuss the parameters that can affect the technologies sustainability, to better highlight the most onerous and impactful steps of each technology. Then, this paper also shows that ESCAPE approach allows to propose some strategies to improve the recovery processes, with the aim to support eco-design.

Sustainability Analysis of Processes to Recycle Discharged Lithium-Ion Batteries, Based on the ESCAPE Approach.

There are several recycling methods to treat discharged lithium-ion batteries, mostly based on pyrometallurgical and hydrometallurgical approaches. Some of them are promising, showing high recovery efficiency (over 90%) of strategic metals such as lithium, cobalt, and nickel. However, technological efficiency must also consider the processes sustainability in terms of environmental impact. In this study, some recycling processes of spent lithium-ion batteries were considered, and their sustainability was evaluated based on the ESCAPE "Evaluation of Sustainability of material substitution using CArbon footPrint by a simplifiEd approach" approach, which is a screening tool preliminary to the Life Cycle Assessment (LCA). The work specifically focuses on cobalt recovery comparing the sustainability of using inorganic or organic acid for the leaching of waste derived from lithium-ion batteries. Based on the possibility to compare different processes, for the first time, some considerations about technologies optimization have been done, allowing proposing strategies able to save chemicals. In addition, the energy mix of each country, to generate electricity has been considered, showing its influence on the sustainability evaluation. This allows distinguishing the countries using more low-carbon sources (nuclear and renewables) for a share of the electricity mix, where the recycling processes result more sustainable. Finally, this outcome is reflected by another indicator, the eco-cost from the virtual pollution model 99' proposed by Vogtländer, which integrates the monetary estimation of carbon footprint.

The Improvement of Durability of Reinforced Concretes for Sustainable Structures: A Review on Different Approaches.

The topic of sustainability of reinforced concrete structures is strictly related with their durability in aggressive environments. In particular, at equal environmental impact, the higher the durability of construction materials, the higher the sustainability. The present review deals with the possible strategies aimed at producing sustainable and durable reinforced concrete structures in different environments. It focuses on the design methodologies as well as the use of unconventional corrosion-resistant reinforcements, alternative binders to Portland cement, and innovative or traditional solutions for reinforced concrete protection and prevention against rebars corrosion such as corrosion inhibitors, coatings, self-healing techniques, and waterproofing aggregates. Analysis of the scientific literature highlights that there is no preferential way for the production of "green" concrete but that the sustainability of the building materials can only be achieved by implementing simultaneous multiple strategies aimed at reducing environmental impact and improving both durability and performances.

Nafion electro-spun reinforced membranes for polymer electrolyte fuel cell.

The introduction of different reinforcement materials (yarns, fibrils, etc) into the membranes has been investigated with the aim of maintaining adequate membrane properties in terms of mechanical strength, good chemical stability, low swelling at critical temperatures and a stable electrochemical performance in PEFC. An innovative technique for the development of membranes is based on polymeric films containing polymeric nanofibres obtained through electrospinning. The electrospinning of Nafion blends with polyvinylpirrolidone (PVP) and polystyrene (PS) was investigated in this work. In particular, the morphology and diameter of electrospun fibres as a function of the electrospinning parameters and solution preparation have been studied and in both cases, a critical concentration of blend solution was found. Beaded fibres were obtained above such a concentration and, below it, only fibre mats were observed. Reinforced Nafion-based membranes were realised by using the obtained spun films. Preliminary proton conductivity and fuel cell results have shown the capability of operating in a fuel cell environment with a slightly higher performance than pure Nafion but having an improved stability at high temperatures.

Self Standing Mats of Blended Polyaniline Produced by Electrospinning.

Conducting nanofibers of polyaniline (PANI) doped with camphor-10-sulfonic acid (HCSA) and blended with different polymers, such as polymethyl methacrylate (PMMA) and polyvinyl acetate (PVAc), have been fabricated using the electrospinning technique. Scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA) were utilized to characterize the morphology and the thermal stability of PANI-blended fibers. An extensive study was performed to understand the copolymer influence on both the structural and surface properties of the realized conductive thin films. Samples main electrical characteristics, as conductivity, specific capacitance and electrochemical performances were tested. The better mats were obtained with the use of PVAc copolymer, which showed a conductivity value two orders of magnitude higher than the PMMA system. Aiming at further improving the electrochemical features of these blended mats, hybrid fibers based on PANI/PVAc/graphene oxide and PANI/PVAc/iron oxide were also produced and characterized. The obtained mats were potentially addressed to numerous practical fields, including sensors, health applications, smart devices and multifunctional textile materials.

Hybrid Zeolite SAPO-34 Fibres Made by Electrospinning.

A new generation of compressor-free heat pumps based on adsorption technology and driven by solar energy is available. Performance and costs are, however, the main obstacles to their commercial diffusion, and more material and system developments are required. In this work, a new coating made of microfibres produced by the electrospinning of polymer/zeolite mixtures is presented. Three different polymer carriers, polyvinyl acetate, polyethylene oxide and polystyrene, have been used together with zeolite SAPO-34 as an adsorbing material. Electrospun microfibres showed a mean diameter ranging from 0.75 µm to 2.16 µm depending on the polymer carrier, with a zeolite content from 60 wt.% to 87 wt.%. Thermal analysis (TGA-DSC) results showed that water desorption from microfibres at T = 150 °C was close to 17 wt.%, a value in agreement with the adsorption capacity of pure SAPO-34. The morphology characterization of coatings demonstrated that the microfibre layers are highly porous and have an elevated surface area.

Binders alternative to Portland cement and waste management for sustainable construction-part 1.

This review presents "a state of the art" report on sustainability in construction materials. The authors propose different solutions to make the concrete industry more environmentally friendly in order to reduce greenhouse gases emissions and consumption of non-renewable resources. Part 1-the present paper-focuses on the use of binders alternative to Portland cement, including sulfoaluminate cements, alkali-activated materials, and geopolymers. Part 2 will be dedicated to traditional Portland-free binders and waste management and recycling in mortar and concrete production.

Binders alternative to Portland cement and waste management for sustainable construction - Part 2.

The paper represents the "state of the art" on sustainability in construction materials. In Part 1 of the paper, issues related to production, microstructures, chemical nature, engineering properties, and durability of mixtures based on binders alternative to Portland cement were presented. This second part of the paper concerns the use of traditional and innovative Portland-free lime-based mortars in the conservation of cultural heritage, and the recycling and management of wastes to reduce consumption of natural resources in the production of construction materials. The latter is one of the main concerns in terms of sustainability since nowadays more than 75% of wastes are disposed of in landfills.