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The major challenge in the current context of the rising world energy demand is to limit the global temperature increase for mitigating climate change. This goal requires a large reduction of CO2 emissions, mainly produced by power generation and industrial processes using fossil fuels. In this study, a novel methodology for K2CO3-doped Li4SiO4 sorbents production for CO2 capture at high temperatures was adopted based on the Design of Experiments (DoE). This innovative approach systematically tested different synthesis (temperature and K2CO3 content) and adsorption conditions (sorption temperature and CO2 concentration), allowing for the assessment of individual and interactive effects of process parameters. The Response Surface Methodology (RSM) was employed to obtain non-linear predictive models of CO2 uptake and Li4SiO4 conversion. The results of RSM analysis evidenced a maximum adsorption capacity of 196.4 mg/g for a sorbent produced at 600 °C and with 36.9 wt% of K2CO3, tested at 500 °C and 4 vol% of CO2. Whereas at 50 vol% of CO2, the best uptake of 295.6 mg/g was obtained with a sorbent synthesized at 600 °C, containing less K2CO3 (17.1 wt%) and tested at a higher temperature (662 °C). These findings demonstrate that K2CO3-doped Li4SiO4 sorbents can be tailored to maximize CO2 capture under various operating conditions, making them suitable for use in industrial processes. [ABSTRACT FROM AUTHOR]

Myriophyllum aquaticum (Vell.) Verdc., an invasive aquatic plant from South America, is to date worldwide distributed. In Tuscany M. aquaticum has colonized much of the surface water network of reclamation channels, forcing the reclamation authority to its removal, with the production of a huge amount of wet biomass to be disposed as a biological waste. In the present study the hydrothermal carbonization (HTC) process was proposed and investigated as a path for the valorisation of this waste biomass. Performed in aqueous conditions at moderate temperatures, HTC does not require energy-intensive pre-drying steps, making HTC applicable to biomass feedstocks with high moisture contents. HTC leads to a carbonaceous solid product, referred to as hydrochar, with different potential applications, such as solid biofuel, or soil-improving material. An experimental investigation was carried out performing HTC tests in a laboratory-scale reactor. The joint effect of operating parameters (temperature, residence time and solid load) on process yields and hydrochar properties was investigated by Design of Experiments – Response Surface Methodology (DoE-RSM), a statistical and mathematical approach for process analysis, prediction, and optimization. The results obtained demonstrated the feasibility of HTC for M. aquaticum, suggesting HTC as a promising treatment path. Beyond the use as biofuel, the suitability of the hydrochar produced from M. aquaticum as organic growth medium for vegetable seedlings in horticulture and gardening or soil amendment was evaluated. Potential phytotoxic effects of M. aquaticum hydrochar were evaluated through bioassays using cress seeds (Lepidium sativum L.) as a model species. [ABSTRACT FROM AUTHOR]

Hydrothermal Carbonization (HTC) represents a promising green technology for converting various biomass feedstocks into valuable hydrochar and liquid products. In this study, the HTC process of Myriophyllum aquaticum Verd., highly diffused in Tuscany (Italy), was investigated varying the process temperatures and the holding times. Indeed, it is one of the world's most troublesome invasive aquatic weeds, impacting not only the quality of water but also contributing to habitat deterioration; therefore, several management practices are required to address the problem. This research focused on obtaining preliminary experimental data to be further implemented in a lumped kinetic model to elucidate the reaction pathways leading to the formation of primary hydrochar and liquid compounds responsible for secondary hydrochar production. To figure out the HTC liquid phase composition and the organic compounds responsible for secondary hydrochar formation, the HighPerformance Liquid Chromatography (HPLC) analytical technique was employed. This technique allowed to identify and quantify some of key chemical components present in the HTC liquid phase, i.e., sugars and furans. Moreover, the future integration of a lumped kinetic model and advanced analytical techniques not only will enhance the understanding of the Myriophyllum aquaticum HTC process but will also provide valuable insights into the optimization of HTC conditions for biomass conversion and resource recovery. [ABSTRACT FROM AUTHOR]

Post-combustion capture technologies based on regenerable solid sorbents are attracting increasing attention as ways to reduce CO2 emissions. The present study focused on the fabrication at industrial lab-scale of lithium orthosilicate (Li4SiO4) sorbents for CO2 capture at high temperature and low concentration. The ball milling process was used during the reagents mixing phase to modify the microstructure of the obtained Li4SiO4 powders. The CO2 sorption properties of the sorbents were studied in a controlled gas flow environment at low CO2 concentration (4 vol%). The effect of different milling times (0-120 min) on the sorption performance of the sorbents was investigated together with the effect of the adsorption temperature (470-570 °C) by using the Response Surface Methodology, and predictive models for the Li4SiO4 conversion and the adsorption rate were developed. The results evidenced that the ball milling process increased the pure Li4SiO4 sorption performance, reaching a maximum sorption capacity of 156 mg CO2/g sorbent for 80 min of milling and adsorption temperature of 515 °C. [ABSTRACT FROM AUTHOR]

Recycling lithium-ion batteries (LIBs) is becoming an imperative task given the large flow of spent batteries that in the next future will have to be managed. Among the current three main recycling routes to convert spent LIBs into recycled products, that is, pyrometallurgy, hydrometallurgy, or direct recycling, the co-precipitation route lies between the last two routes: its key unit operations are the leaching of battery materials and the co- precipitation of a precursor for the re-synthesis of the cathode active material (CAM). High susceptibility to impurities in the leached solution and a strong link between high-quality CAM precursors and the composition of the dissolved metal salts, makes experimental analysis on spent LIBs a crucial step to find the best operating conditions. For this reason, we present an experimental campaign to study the co-precipitation and formation of the complex chemical compounds involved in the process. Moreover, we also exploit the support that rigorous models are giving in many industrial fields, also benefiting chemical engineering and laboratory analysis. Therefore, in this study we also present a rigorous simulation model on UniSim Design® with the thermodynamic package OLI® that enables the possibility to consider most of the different liquid-solid equilibria needed. A validation of the model is performed with experimental data and a sensitivity analysis on metal concentrations, pH, and chelating agent is performed to find the critical parameters that regulate the co-precipitation outcomes. The aim is to optimize the choice of operating conditions to limit the number of laboratory tests and complex analyses that are often expensive and time-consuming. [ABSTRACT FROM AUTHOR]

Hydrothermal carbonization (HTC) has received considerable attention in recent years for its potential to process heterogeneous organic wastes with high moisture contents. Unlike other thermochemical processes, HTC does not require drying of the feedstock as a pre-treatment. Performed in aqueous conditions at moderate temperatures under autogenous pressure, HTC produces a carbon rich solid phase, referred to as hydrochar, which can be directly used as a solid fuel, or it can be better exploited for new applications. In the present work the potential valorization by HTC of a waste stream from mechanical biological treatment of mixed municipal solid waste, namely the under-sieve fraction from the mechanical treatment stage, was explored. This stream does not have any potential for material recovery, and it is usually landfilled after aerobic biostabilization. HTC tests were carried out in a laboratory-scale reactor. The joint effect of different process parameters on the yield and physicochemical properties of the hydrochar produced was investigated. The design of experiments (DoE) / response surface methodology (RSM) approach was used for the analysis of the influence of temperature, time and solid load on the mass yield and properties of hydrochar. Quantitative relationships between responses and process parameters were determined. The results obtained demonstrated the feasibility of HTC for mixed municipal solid waste, suggesting HTC as a promising alternative treatment path to current waste management. [ABSTRACT FROM AUTHOR]