Generalisation of the solution of the inverse Richards' problem

In inverse problems defined by models that include partial differential equations, a part of the boundary conditions are unknown and are to be estimated from experimental measurements. We have shown in a previous contribution that the solution of the inverse Richards' problem can allow estimating percolation rates at the bottom of landfills through the use of measurements at the surface only. This can be a useful complement of the information furnished by the vadose measurement system, pointing to the possible presence of biases of in-situ equipment, and making it possible to use inexpensive mobile equipment to carry out surface measurements. In this article, we consider a generalisation which makes it possible to consider the presence of unknown nonlinear parameters, such as the effective hydraulic conductivity and the root uptake coefficients. This is accomplished using the method of separation of variables in the resulting estimation problem. Thanks to the linearity of the model, all these conditions can be expressed as linear functions of the unknown lower boundary condition. Otherwise, the relevant non-linear parameters are to be estimated from the data as well. Obviously, the correlation between the linear parameters contained in the unknown lower boundary conditions and the non-linear parameters can reduce the reliability of the monitoring procedure and hence the necessity of limiting the number of the latter

New trends in the synthesis of nanoparticles by green methods

In this brief survey, we deal with green processes concerning the synthesis of zerovalent nanoparticles, enlighting some aspects motivating their choice with respect to traditional techniques generally relying upon toxic or noxious reactants and stabilizing agents. After a short discussion about health and environmental safety related to the use of standard reductants, we run through several green methods for metal nanoparticle synthesis and we split them into two basic classes, according to the electropositivity of the elements which the nanoparticles are made of. This classification has been proposed in order to account for strengths and weaknesses of processes based on active substances of biological origin that, though being effective in the production of noble metal nanoparticles, proved to be much less suitable when tested in the synthesis of nanoparticles made of more electropositive elements. The goal of this work is essentially oriented to stimulating new research trends for the eco-friendly production of nanosized non-noble elements deserving more attention by current nanobiotechnology

A Novel Graphite-Based Sorbent for Oil Spill Cleanup

The performance of an innovative material based on expanded graphite, Grafysorber\uae G+ (Directa Plus), has been tested through laboratory, tank, and confinement tests for oil removal in case of an oil spill and water treatment. In addition to the ability to retain oil, the possibility of reusing this material after regeneration via squeezing was also evaluated. As a comparison, the same experimental tests were conducted using polypropylene flakes (PP), the material currently most used to deal with spill accidents. Oils with different chemical and physical properties were used, namely kerosene, diesel, and crude oil. From the laboratory tests, the capacity of Grafysorber\uae G+ to retain oil was found to be directly proportional to the viscosity of the latter, with adsorption values ranging from 76.8 g/g for diesel to 50.8 g/g for kerosene, confirming the potential of the innovative material compared to the PP. Cyclical use tests have confirmed certain reusability of the material, even if its adsorbent capacity decreases significantly after the first cycle and continues to decrease in subsequent cycles, but a less marked manner. Finally, some considerations based on the adsorption capacities were found to suggest that the adoption of the new material is also economically preferable, resulting in savings of 20 to 40% per kg of hydrocarbon treated

Chromium(III) Removal from Wastewater by Chitosan Flakes

Chitosan is very effective in removing metal ions through their adsorption. A preliminary investigation of the adsorption of chromium(III) by chitosan was carried out by means of batch tests as a function of contact time, pH, ion competition, and initial chromium(III) concentration. The rate of adsorption was rather rapid (t1/2 < 18 min) and influenced by the presence of other metal ions. The obtained data were tested using the Langmuir and Freundlich isotherm models and, based on R2 values, the former appeared better applicable than the latter. Chitosan was found to have an excellent loading capacity for chromium(III), namely 138.0 mg Cr per g of chitosan at pH = 3.8, but metal ions adsorption was strongly influenced by the pH. About 76% of the recovered chromium was then removed simply by washing the used chitosan with 0.1 M EDTA (Ethylenediaminetetraacetic acid) solution. This study demonstrates that chitosan has the potential to become an effective and low-cost agent for wastewater treatment (e.g., tannery waste) and in situ environmental remediation

A Simple and Inherent Safe Mechanosynthesis Method for Producing Tin Metal Nanoparticles Dispersions

A method for the synthesis of Sn nanoparticles (NPs) is presented, whose technique is based on a reagentless comminution process, where bulky Sn metal undergoes a surface abrasion with release of zerovalent metal NPs produced by metal-ceramic balls collisions in a liquid medium embedding and dispersing the as-formed NPs. Two different techniques have been adopted and compared, according to the geometry of the pristine bulky metal. In a former case, a Sn metal precursor is shaped in foil form covering the surface of a magnetic stirring device, keeping abrading spheres in agitation in a liquid phase. In a latter case, the metal precursor, in form of spheres, is kept in agitation in a liquid phase together with the abrading balls, whose hits and friction with the Sn spheres lead to the formation of the corresponding NPs. Three different capping agents, one of which of natural origin, have been dissolved in the liquid phase to prevent NPs aggregation, with positive effects in long-term stabilization. The particles have been characterized for shape and diameter by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The technique here proposed may represent a promising method, in line with the paradigms of inherent safety, for the synthesis of stable Sn NPs dispersions as a valid alternative to Ag NPs in pharmacology and other biomedical applications

Soil Remediation: Towards a Resilient and Adaptive Approach to Deal with the Ever-Changing Environmental Challenges

Pollution from numerous contaminants due to many anthropogenic activities affects soils quality. Industrialized countries have many contaminated sites; their remediation is a priority in environmental legislation. The aim of this overview is to consider the evolution of soil remediation from consolidated invasive technologies to environmentally friendly green strategies. The selection of technology is no longer exclusively based on eliminating the source of pollution but aims at remediation, which includes the recovery of soil quality. \u201cGreen remediation\u201d appears to be the key to addressing the issue of remediation of contaminated sites as it focuses on environmental quality, including the preservation of the environment. Further developments in green remediation reflect the aim of promoting clean-up strategies that also address the effects of climate change. Sustainable and resilient remediation faces the environmental challenge of achieving targets while reducing the environmental damage caused by clean-up interventions and must involve an awareness that social systems and environmental systems are closely connected

Alkali–Silica Reactivity Potential of Aggregates from Different Sources in Pakistan

This paper aims to support stakeholders in the sustainable construction sector by exploring the potential of unexamined aggregates from five distinct origins: the Jandol River, the Swat River, the Panjkorha River, the Kitkot Drain, and the Shavey Drain situated in Malakand division, North Waziristan, Pakistan, concerning Alkali–Silica Reaction (ASR) prior to their incorporation into large-scale construction practices. Petrographic examination for the determination of the mineralogical composition of all collected aggregates revealed that aggregates stemming from the Swat River, Panjkorh River, Kitkot Drain, and Shavey Drain exhibited no reactive minerals. In contrast, those from the Jandol River showed reactive mineral content. Physical analysis of the aggregates revealed that Jandol River aggregates had superior resistance to impact, crushing, and abrasion, having values of 18.53%, 18.53%, and 20.10%, respectively. Moreover, the chemical analysis exhibited the highest silica content (SiO2) in Jandol River aggregates, i.e., 94.7%, respectively. Samples in the form of cubes, prisms, and mortar bars were prepared to study both the mechanical properties and the expansion tendencies of specimens prepared from different aggregate sources. Validation of the reactive nature of the Jandol River aggregates was corroborated by the expansion results obtained from the mortar bars and the reduction in compressive strength and flexure strength by 8.2% and 9.2%, respectively, after 90 days, higher than that of aggregates exposed to ASR sourced from the other four origins. It can be asserted that aggregates from the Jandol River source are more susceptible to ASR as compared to other aggregates. To mitigate the potential of ASR, various strategies, such as using low reactivity, natural, or processed aggregates; low alkali-containing cement; inducing pozzolanic substances in concrete; etc., are recommended. Simultaneously, an economic feasibility study and environmental assessments are recommended as future developments

Enhanced Oil Spill Remediation by Adsorption with Interlinked Multilayered Graphene

The performances of an innovative material based on graphene multilayers in a 3D structure similar to expanded graphite, Grafysorber\uae G+ (Directa Plus), have been tested via in field applications on a real contaminated site. Several experimental tests were performed using Grafysorber\uae inside adsorbent devices (booms and pillows) to treat waters polluted by oil. The experimental campaign was carried out with the aim of comparing the performances of Grafysorber\uae with those of polypropylene (PP), which is the material used worldwide in case of water oil spill clean-up activities. The results achieved have confirmed a considerably higher selective adsorption capacity of Grafysorber\uae compared to PP, and configure the new material as a promising alternative to standard materials in enhancing oil spill remediation by selective adsorption

Characterization and Sustainability Assessment of Water-based Metal Oxide Nanofluids

The development of nanofluids (NFs) as advanced thermal carriers has attracted considerable attention due to their potential to improve the heat transfer efficiency in a variety of industrial applications. This study focuses on the properties of water-based nanofluids containing CuO and Al2O3 nanoparticles and evaluates the environmental sustainability of the produced prototypes through life cycle analysis (LCA). The synthesis process involved the preparation of nanofluids by dispersing nanoparticles in base fluids, followed by a characterization of their thermophysical properties. Key parameters, such as nanoparticle concentration, morphology, and stability to achieve superior thermal conductivity and minimal flocculation were considered. The environmental impact of the produced nanofluids was evaluated using an LCA procedure (CO2 footprint analysis), encompassing the entire lifecycle from raw material extraction to disposal. While nanofluids offer substantial improvements in thermal performance, the analysis revealed that their environmental footprint is influenced by factors such as energy consumption during synthesis, nanoparticles potential toxicity, and waste management practices. The study underscores the importance of adopting green synthesis methods and sustainable practices to mitigate the ecological impact of nanofluids. These findings provide valuable insights into the trade-offs between enhanced thermal efficiency and environmental sustainability, paving the way for the development of eco-friendly nanofluids for industrial applications

Computer-aided Investigation of the Performance of Water-based Metal Oxide Nanofluids

Computational Fluid Dynamics (CFD) has emerged as a powerful tool for simulating the behavior of nanofluids in thermal systems, providing a cost-effective alternative to experimental studies. This contribution presents a comprehensive computational modelling approach to study the flow and heat transfer characteristics of nanofluids, based on experimental data from synthesized prototypes of CuO (1 wt %, 5 wt %) and Al2O3 (1 wt %, 5 wt %) nanoparticles in water. The modeling was performed using OpenFOAM, an open-source CFD Software that allows a high degree of customization of simulation parameters. The study involved the development of detailed CFD models to investigate the influence of nanoparticle morphological properties on the thermal performance of nanofluids. Different multiphase schemes were used to accurately simulate the complex interactions between nanoparticles and base fluids. The simulation results were compared with experimental and literature data to validate the models and ensure their reliability. The validated models were then used to extend the experimental campaign, exploring the potential of different nanoparticle compositions and concentrations to optimize thermal efficiency. The results demonstrate that CFD modeling can effectively predict the behavior of nanofluids, providing a robust framework for optimizing their performance in real-world applications. The study underscores the importance of integrating experimental and computational approaches to achieve a comprehensive understanding of nanofluid dynamics. The insights gained from this research contribute to the advancement of nanofluid technology, offering practical solutions for enhancing heat transfer efficiency in industrial processes