Red Mud-Blast Furnace Slag-Based Alkali-Activated Materials

The aluminum Bayer production process is widespread all over the world. One of the waste products of the Bayer process is a basic aluminosilicate bauxite residue called red mud. The aluminosilicate nature of red mud makes it suitable as a precursor for alkali-activated materials. In this work, red mud was mixed with different percentages of blast furnace slag and then activated by sodium silicate solution at different SiO2/Na2O ratios. Obtained samples were characterized by chemical–physical analyses and compressive strength determination. Very high values of compressive strength, up to 50 MPa, even for high percentage of red mud in the raw mixture (70 wt.% of RM in powder mixture), were obtained. In particular, the higher compressive strength was measured for cubic samples containing 50 wt.% of RM, which showed a value above 70 MPa. The obtained mixtures were characterized by no or scarce environmental impact and could be used in the construction industry as an alternative to cementitious and ceramic materials

Development of geopolymer materials for sustainable design

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A New Generation of Hydrogen-Fueled Hybrid Propulsion Systems for the Urban Mobility of the Future

The H2-ICE project aims at developing, through numerical simulation, a new generation of hybrid powertrains featuring a hydrogen-fueled Internal Combustion Engine (ICE) suitable for 12 m urban buses in order to provide a reliable and cost-effective solution for the abatement of both CO2 and criteria pollutant emissions. The full exploitation of the potential of such a traction system requires a substantial enhancement of the state of the art since several issues have to be addressed. In particular, the choice of a more suitable fuel injection system and the control of the combustion process are extremely challenging. Firstly, a high-fidelity 3D-CFD model will be exploited to analyze the in-cylinder H2 fuel injection through supersonic flows. Then, after the optimization of the injection and combustion process, a 1D model of the whole engine system will be built and calibrated, allowing the identification of a “sweet spot” in the ultra-lean combustion region, characterized by extremely low NOx emissions and, at the same time, high combustion efficiencies. Moreover, to further enhance the engine efficiency well above 40%, different Waste Heat Recovery (WHR) systems will be carefully scrutinized, including both Organic Rankine Cycle (ORC)-based recovery units as well as electric turbo-compounding. A Selective Catalytic Reduction (SCR) aftertreatment system will be developed to further reduce NOx emissions to near-zero levels. Finally, a dedicated torque-based control strategy for the ICE coupled with the Energy Management Systems (EMSs) of the hybrid powertrain, both optimized by exploiting Vehicle-To-Everything (V2X) connection, allows targeting H2 consumption of 0.1 kg/km. Technologies developed in the H2-ICE project will enhance the know-how necessary to design and build engines and aftertreatment systems for the efficient exploitation of H2 as a fuel, as well as for their integration into hybrid powertrains

Eco‑design of geopolymer‑based materials recycling porcelain stoneware wastes: a life cycle assessment study

A comparative “cradle to grave” Life Cycle Analysis between the production processes of ceramic stoneware products and geopolymeric materials obtained by valorizing ceramic wastes is reported. This study presents an effective eco-design approach to obtain sustainable materials through a low energy consumption manufacturing process, a feature that is essential in a historical period of high geopolitical instability which makes the supplying of fossil fuels difficult and particularly expensive. In particular, the possibility of lowering production costs (saving on the cost of waste disposal, using a raw-second material, and a low-temperature production process) could represent a strong contribution to the environmental and economic sustainability of the Italian ceramic industry, which is going through a time of severe financial crisis which due to the unprecedent high cost of raw materials and energy. Finally, the new geopolymeric systems proposed in this paper could be profitably used in the field of green building, art, eco-design, and technical-artistic value-added applications, such as restoration, conservation, and/or rehabilitation of historic monuments, or simply as materials for building revetments

Alkali-Activated Red Mud and Construction and Demolition Waste-Based Components: Characterization and Environmental Assessment

The aluminum Bayer production process is the most diffused process in the world, but it creates a high amount of basic waste material known as red mud (RM). The use of RM as a precursor of alkali-activated materials is one of the best opportunities for both the ecosystem and the economy. In the present work, mortar samples were obtained by alkali activation of RM with various percentages of blast-furnace slag (BFS) and inert construction and demolition sands. This process creates samples that have a low environmental impact and that can be used as an alternative in the construction industry to cement materials or ceramic ones. The development of these new materials could also represent a way to reduce the CO2 emissions linked to cement and ceramic brick production. In the present study, cubic 40 mm samples reported very interesting values in compressive strength, with a maximum of about 70 MPa for low environmental impact mortars. With such a material, it is possible to create solid bricks for structural use and concrete tiles for road paving or use it for other purposes. Mortar specimens were prepared and characterized, and an LCA analysis with a “cradle-to-gate” approach was carried out for a comparison of the environmental impact of the studied mortars with other materials currently marketed

Development of Geopolymer-Based Materials with Ceramic Waste for Artistic and Restoration Applications

This contribution presents the preparation and characterization of new geopolymer-based mortars obtained from recycling waste deriving from the production process and the “end-of-life” of porcelain stoneware products. Structural, morphological, and mechanical studies carried out on different kinds of mortars prepared by using several types of by-products (i.e., pressed burnt and extruded ceramic waste, raw pressed and gypsum resulting from exhausted moulds) point out that these systems can be easily cast, also in complex shapes, and show a more consistent microstructure with respect to the geopolymer paste, with a reduced amount of microcracks. Moreover, the excellent adhesion of these materials to common substrates such as pottery and earthenware, even for an elevated concentration of filler, suggests their use in the field of technical-artistic value-added applications, such as restoration, conservation, and/or rehabilitation of historic monuments, or simply as materials for building revetments. For all these reasons, the proposed materials could represent valuable candidates to try to overcome some problems experienced in the cultural heritage sector concerning the selection of environmentally friendly materials that simultaneously meet art and design technical requirements

A novel method of iron oxalate production through the valorization of red mud

Bauxite residues known as “Red Mud” (RM) are the principal waste of caustic digestion of bauxite from the Bayer Process, whose costs of disposal are expensive and cover 5 % of the total costs of extraction and processing for aluminum production. Nevertheless, this material can be considered an important source of high-value elements, such as rare earths (REEs) and metals, Fe, Ti, Al and others. In this work, the focus has been on the recovery of iron in the form of the compound Fe(II) oxalate. Four types of acids have been used (HCl, H2SO4, H3PO4, H2C2O4) for iron extraction from RM coming from Montenegro. Hydrochloric acid shows a higher iron extraction capacity, reaching an iron extraction yield in solution of 22.6 %. Sulfuric and phosphoric acid, instead, interacted with RM leading to the formation of sulfonate and phosphate species, inhibiting the leaching ability of individual species. Oxalic acid showed the least amount of iron ions extracted but formed a stable ionic complex in solution, Fe2(C2O4)3∙2 H2O. Starting from this complex it was possible to recover the corresponding salt by a reduction and precipitation process. Through a pre-treatment with HCl and a subsequent treatment with oxalic acid, it was possible to obtain a better yield of iron oxalate. Starting from the laboratory scale, a CHEMCAD plant was conceptualized with a yield higher than 16 % per pass (repeatable 3 times with a global iron yield>50 %) and obtaining iron(II) oxalate dihydrate with purity up to 96%wt. In a holistic view of the problem, the proposed process can operate in parallel with other procedures proposed in the literature for the recovery of other valuable substances from red mud