Search Results (413)

The increasing demand for sustainable construction materials has driven research into the reuse of plastic waste for renewable building applications. This study introduces a new lightweight insulating mortar for floor and roof systems, utilizing recycled rigid polyurethane (PU) foam as the primary aggregate. The binder mainly consists of Portland cement, with no added sand, and includes minor additives to enhance mechanical, physical, and thermal properties. Initial tests demonstrated that key performance metrics—density, compressive strength, and thermal conductivity—are significantly influenced by the PU content. As the proportion of PU increased, all three parameters decreased. The optimized formulation, comprising 92.25 vol.% PU foam, 6.75 vol.% cement, and 1 vol.% additives, achieved a low bulk density of 420 kg/m³, a compressive strength of 1 MPa, and a thermal conductivity of 0.07 W/m·K. A pilot-scale production system with a capacity of 1500 L/h (equivalent to 20 bags of 75 L) was subsequently designed, implemented, and validated. These findings underscore the potential of PU-based lightweight insulating mortars to reduce environmental impact and support the development of sustainable construction practices globally. Full article

The global pursuit of a sustainable and decarbonized energy landscape requires the development of novel materials capable of supporting lightweight construction, advanced energy conversion, storage, and thermal management technologies. Among these, metal foams have emerged as a versatile class of porous materials, offering a unique combination of low density, high surface area, three-dimensional (3D) interconnected porosity, and favorable thermal and electrical conductivities. These attributes make them highly suitable for a broad range of applications critical to the ongoing energy transition, assuming an increasingly central role in enabling clean, efficient, and resilient energy infrastructures. From this key perspective, the present review highlights the relevance of the adoption of metal foams in several fields crucial for the energy transition. By presenting methodologies and outcomes of research results, mainly from the last five years, the paper underscores the potential of low-weight, high-surface, and high-performance porous materials in contemporary and future industry, supporting sustainable development and, more generally, energy transition and circular economy. The approach also aims to minimize negative impacts and promote sustainability, for example, by recycling and transforming waste materials. Full article

The development of industry and technology, despite making everyday life easier, generates large amounts of various wastes that negatively affect the environment. Unexpected leaks of substances such as oils, petroleum substances, and chemicals also contribute to the degradation of aquatic and terrestrial ecosystems. Long-term effects of environmental pollution require the development of advanced materials and technologies to collect and neutralize pollutants. Sorbents obtained from waste, including banana peels, coconut fibers, and polyurethane foams from recycling the thermal housing of refrigeration devices, allow a reduction in the amount of generated waste and the development of appropriate sorbents. This work focuses on comparing the sorption and neutralization properties of these materials for two types of oil, machine and diesel, and the possibility of using them in rescue and firefighting operations conducted by firefighters. The results obtained indicate that the viscose–cellulose sorbent and the polyurethane foam sorbent are characterized by better performance parameters than sorbents from coffee grounds or coconut fibers. The best parameters were obtained after the first 10 min of the sorbent–contaminant reaction, whereas in the case of contamination with machine oil, the absorption capacity was better than for diesel oil for each sorbent subjected to analysis. Full article

In light of the environmental impact of disposable products made from petroleum-based plastics, this study focused on developing biodegradable foam trays made from a starch (PS) derived from potato waste and beer malt flour (BMBF). The objective of this study was to evaluate the effect of the concentration of BMBF on the physical and mechanical properties of potato starch-based foam trays prepared by the thermoforming process at temperatures of 150 °C (upper plate) and 145 °C (lower plate) for 5 min and 40 s. The results showed that increasing the BMBF concentration from 0 to 40% reduced the moisture content from 4.68% to 3.42%, increased the thickness from 2.63 cm to 4.77 cm, and decreased the density from 0.28 g.cm⁻³ to 0.15 g.cm⁻³. Meanwhile, the water absorption capacity increased from 38.7% to 69.7%. In terms of mechanical properties, increasing the BMBF concentration in the PS foam tray resulted in a decrease in hardness from 5.61 N to 2.87 N, a decrease in tensile strength from 2.92 MPa to 0.85 MPa, and a decrease in elongation from 1.42% to 0.59%. Meanwhile, fracturability increased from 2.04 mm to 3.68 mm. FTIR analysis revealed interactions between BMBF and PS in the composite foam tray. Thermogravimetric analysis (TGA) showed two thermal events: one between 20.96 °C and 172.89 °C, and another between 189.14 °C and 517.69 °C, with weight losses of 5.53% and 74.23%, leaving an ash residue of 20.24%. Differential calorimetry analysis (DSC) showed a glass transition at 152.88 °C and a melting at 185.94 °C, with an enthalpy of fusion of 74.11 J.g⁻¹. Higher concentrations of BMBF (>10%) decreased the water resistance, mechanical strength, and flexibility of the PS foam trays. Therefore, a formulation of 90% PS and 10% BMBF was better for producing a foam tray with improved mechanical properties and water resistance, which could be used as a sustainable alternative to conventional single-use plastic. Full article

In the context of the growing need to reduce greenhouse gas emissions and to develop sustainable solutions for the construction industry, foamed geopolymers represent a promising alternative to traditional binders and insulation materials. This study investigates the thermal properties of novel low-emission, insulating geopolymer binders made from fly ash with diatomite, chalcedonite, and wood wool aiming to assess their potential for use in thermal insulation systems in energy-efficient buildings. The stability of the foamed geopolymer structure is also assessed. Measurements of thermal conductivity, specific heat, microstructure, density, and compressive strength are presented. The findings indicate that the selected geopolymer formulations exhibit low thermal conductivity, high heat capacity and low density, making them competitive with conventional insulation materials—mainly load-bearing ones such as aerated concrete and wood wool insulation boards. Additionally, incorporating waste-derived materials reduces the production carbon footprint. The best results are represented by the composite incorporating all three additives (diatomite, chalcedonite, and wood wool), which achieved the lowest thermal conductivity (0.10154 W/m·K), relatively low density (415 kg/m³), and high specific heat (1.529 kJ/kg·K). Full article

Due to its lightweight and superior adsorption properties, carbon foam is frequently employed for the removal of heavy metal pollutants from aqueous solutions. In this study, a novel modified carbon foam (M-CF) was successfully synthesized for the effective removal of Pb²⁺ and Cd²⁺ from water. The synthesis involved partially substituting phenol with the liquefaction product of bamboo powder, followed by modification with a silane coupling agent (KH560) and foaming with n-hexane-loaded activated carbon (H/AC). The prepared carbon foam was comprehensively characterized, and its adsorption performance and mechanism for Pb²⁺ and Cd²⁺ in aqueous solution were investigated. The results showed that M-CF possessed a uniform and well-developed spherical pore structure and demonstrated excellent removal capacity for Cd²⁺ and Pb²⁺. The adsorption process conformed to the Sips isotherm model and the pseudo-second-order kinetic equation, with maximum adsorption capacities of 22.15 mg·g⁻¹ and 61.59 mg·g⁻¹ for Cd²⁺ and Pb²⁺, respectively. Mechanistic analysis revealed that the removal of Cd²⁺ and Pb²⁺ was a result of the synergistic effect of physisorption and chemisorption, accompanied by complexation. Furthermore, precipitates formed during the adsorption process were found to be mainly composed of hydroxides, carbonates, and PbS. This research demonstrates the efficacy of carbon foam prepared from bamboo powder waste as a partial phenol substitute for the efficient removal of Pb²⁺ and Cd²⁺ from water, thus expanding the preparation pathways for novel heavy metal adsorption materials. Full article

Plastic (P) and microplastic (MP) pollution in marine and freshwater environments is an increasingly urgent issue that needs to be addressed at many levels. The Seabin (an easily operated and cost-effective floating debris collection device) can help clean up buoyant plastic debris in calm waters while monitoring water pollution. A Seabin was used to conduct a comparative analysis of plastic and microplastic concentrations in northern Lake Garda (Italy) during peak and low tourist seasons. The composition of the litter was further investigated using Fourier-Transform Infrared (FTIR) spectroscopy. The analysis showed a decreased mean amount of plastic from summer (32.5 mg/m³) to autumn (17.6 mg/m³), with an average number of collected microplastics per day of 45 ± 15 and 15 ± 3, respectively. Packaging and foam accounted for 92.2% of the recognized plastic waste products. The material composition of the plastic mass (442 pieces, 103.0 g) was mainly identified as polypropylene (PP, 47.1%) and polyethylene (PE, 21.8%). Moreover, 313 microplastics (approximately 2.0 g) were counted with average weight in the range of 1–16 mg. A case study of selected plastic debris was also conducted. Spectroscopic, microscopic, and thermal analysis of specimens provided insights into how aging affects plastics in this specific environment. The purpose of this study was to establish a baseline for further research on the topic, to provide guidelines for similar analyses from a multidisciplinary perspective, to monitor plastic pollution in Lake Garda, and to inform policy makers, scientists, and the public. Full article

Mycelium-based composites (MBCs) are an emerging category of cost-effective and environmentally sustainable materials that are attracting significant research and commercial interest across various industries, including construction, manufacturing, agriculture, and biomedicine. These materials harness the natural growth of fungi as a low-energy bio-fabrication method, converting abundant agricultural by-products and waste into sustainable alternatives to energy-intensive synthetic construction materials. Their affordability and eco-friendly characteristics make them attractive for both research and commercialisation. Currently, mycelium-based foams and sandwich composites are being actively developed for applications in construction. These materials offer exceptional thermal insulation, excellent acoustic absorption, and superior fire safety compared to conventional building materials like synthetic foams and engineered wood. As a result, MBCs show great potential for applications in thermal and acoustic insulation. However, their foam-like mechanical properties, high water absorption, and limited documentation of material properties restrict their use to non- or semi-structural roles, such as insulation, panelling, and furniture. This paper presents a comprehensive review of the fabrication process and the factors affecting the production and performance properties of MBCs. It addresses key elements such as fungal species selection, substrate choice, optimal growth conditions, dehydration methods, post-processing techniques, mechanical and physical properties, termite resistance, cost comparison, and life cycle assessment. Full article

Per- and polyfluoroalkyl substances (PFAS) have been reported to contaminate soil as a result of improper management of waste, wastewater, landfill leachate, biosolids, and a large and indiscriminate use of aqueous film-forming foams (AFFF), posing potential risks to human health. However, their high chemical and thermal stability pose a great challenge for remediation. As a result, there is an increasing interest in identifying and optimizing very effective and sustainable technologies for PFAS removal. This review summarizes both traditional and innovative remediation strategies and technologies for PFAS-contaminated soils. Unlike existing literature, which primarily focuses on the effectiveness of PFAS remediation, this review critically discusses several techniques (based on PFAS immobilization, mobilization and extraction, and destruction) with a deep focus on their sustainability and scalability. PFAS destruction technologies demonstrate the highest removal efficiencies; however, thermal treatments face sustainability challenges due to high energy demands and potential formation of harmful by-products, while mechanical treatments have rarely been explored at full scale. PFAS immobilization techniques are less costly than destruction methods, but issues related to the regeneration/disposal of spent sorbents should be still addressed and more long-term studies conducted. PFAS mobilization techniques such as soil washing/flushing are hindered by the generation of PFAS-laden wastewater requiring further treatments, while phytoremediation is limited to small- or medium-scale experiments. Finally, bioremediation would be the cheapest and least impactful alternative, though its efficacy remains uncertain and demonstrated under simplified lab-scale conditions. Future research should prioritize pilot- and full-scale studies under realistic conditions, alongside comprehensive assessments of environmental impacts and economic feasibility. Full article

The sustainable utilization of solid waste is crucial for environmental protection. This work investigates the fabrication of foamed ceramics from Cr slag and municipal solid waste incineration (MSWI) fly ash, focusing on the effects of three inhibitors—NH₂SO₃H, ZnO·TiO₂, and (NH₄)₂HPO₄—on material properties and Cr leaching behavior. Experimental analysis, chemical thermodynamic calculations, and material characterization were all employed. Results show that the prepared foamed ceramics meet the JG/T 511-2017 standard for building materials, exhibiting excellent physical properties but significant Cr leaching. Among the inhibitors, (NH₄)₂HPO₄ with a molar ratio of n(P)/n(Cr) = 1 shows the best performance, achieving a bulk density of 205 kg/m³, compressive strength of 0.850 MPa, Cr leaching concentration of 188 μg/L, and a 70.0% of Cr leaching inhibition rate. The improvement is attributed to the AlPO₄ formation that enhancing the strength, and Ca₂P₂O₇ that stabilizing Cr during sintering. This work provides a feasible method for the safe resource utilization of Cr-containing waste. Full article

Additive manufacturing has recently become popular and more cost-effective for building construction. This study presents a prospective life cycle assessment (LCA) of 3D-printed foamed geopolymer composites (3D-FOAM materials) incorporating construction and demolition waste. The materials were developed using fly ash, slag, sand, and a foaming agent, with recycled clay brick waste (CBW) and autoclaved aerated concrete waste (AACW) added as alternative raw materials. The material formulations were evaluated for their compressive strength and thermal conductivity to define two functional units that reflect structural and thermal performance. A prospective life cycle assessment (LCA) was conducted under laboratory-scale conditions using the ReCiPe 2016 method. Results show that adding CBW and AACW reduces environmental impacts across several categories, including global warming potential and ecotoxicity, without compromising material performance. Compared to conventional wall systems, the 3D-FOAM materials offer a viable low-impact alternative when assessed on a functional basis. These findings highlight the potential of integrating recycled materials into additive manufacturing to support circular economy goals in the construction sector. Full article

Nowadays, there is wide advocacy for a transition to circular economic models. Fly Ash (FA) in particular is a major by-product of coal combustion and its annual waste has reached one million tonnes. Cenospheres (CSs) are considered as possibly the most valuable element within FA. Thus, in this research, polymeric foam replication was employed to fabricate ceramic foams based on a CS matrix, for potential biomedical applications. For the fabrication of foams, four types of natural marine sponges were used as templates along with a binder agent. The specimens were sintered at 1200 °C for 1 h. The results were encouraging as the specimens obtained retained the given shape and geometry. Further research will enhance the potential of such materials for future use in biomedical engineering. Full article

The structure of microbial communities in sponge-sand filters, used for the treatment of real domestic sewage with elevated ammonium nitrogen concentrations (approximately 155 mg·dm⁻³), was characterized using 16S rRNA gene sequencing. Analyses using the Illumina technique allowed us to perform a comparison of filters by layer (two or three layers) and type of fill (waste PUR foams with 95% open porosity, sand). Proteobacteria, actinobacteria, and firmicutes were shown to be the most abundant phyla. The number and type of fill layers had a significant impact on the diversity of nitrifying bacteria. The presence of Nitrosomonas and Nitrospira was observed in every sponge fill sample, but the abundance of autotrophic nitrifiers was negligible in the two-layer filter. The conditions there proved more favorable for the growth of aerobic heterotrophic bacteria. Also in the Schmutzdecke layer, a dominance of heterotrophic nitrifiers was found. The abundance of bacteria with nitrifying activity (AOB, comammox, HNAD) in the biomass of spongy fill placed in casings was 1.7 times lower than in foams without casings. In addition, anammox bacteria (unidentified Planctomycetes), found mainly in the sponge fill and Schmutzdecke of the three-layer filters, may have been responsible for NH4⁺-N removal exceeding 70%. In the case of the two-layer filter, the removal of this pollutant reached 92%. Burkholderia and Sphingopyxis were identified as the predominant denitrifying bacteria. The foam-filled filter in the casings showed an increase in o_Caldilineaceae, involved in nitrate removal as non-denitrifiers. Actinomycetes Pseudonocardia and Amycolatopsis, as well as Proteobacteria Devosia, Acinetobacter, and Bdellovibrio, were found to be involved in phosphorus removal in the waste PUR foams. Full article

The type of foaming agent significantly influences the pore structure and properties of foam ceramics, particularly their compressive strength. This study used quartz sand tailings and waste glass powder as raw materials to fabricate foam ceramic materials. The effects of different foaming agents (SiC, CaCO₃, and MnO₂) on the phase evolution, microstructure, pore size distribution, and physical properties of the foam ceramics were investigated, and the foaming mechanisms were elucidated. The results indicated that when SiC was employed as the foaming agent, the viscosity was high at elevated temperatures and pores with irregular shapes tended to form because of the anisotropy of the quartz crystals. CaO generated from CaCO₃ decomposition reduced the melt viscosity by disrupting the [SiO₄] tetrahedra, whereas the formation of anorthite and diopside stabilized the pore morphology, resulting in regular circular pores. When MnO₂ was used as the foaming agent, the pressure from the gas produced during oxidation exceeded the surface tension of the molten phase owing to its viscosity, leading to the formation of larger, irregular, and interconnected pores. The foam ceramic material exhibited optimal properties when 2% CaCO₃ was used as the foaming agent, with a water absorption rate of 30%, bulk density of 0.62 g/cm³, porosity of 68.4%, compressive strength of 9.67 MPa, and thermal conductivity of 0.26 W/(m·K). Full article

Sawdust is receiving increasing attention as a promising green adsorbent. However, due to its powder nature, it is difficult to recover after adsorbing heavy metals and may even cause secondary pollution. To solve this problem, a novel sawdust/foamed geopolymer (SFG) adsorbent was prepared by using sawdust as a raw material, geopolymer as a binder, and hydrogen peroxide as a foaming agent. This study discussed the effect of SFG dosage, solution temperature, solution pH, contact time, and initial Cu²⁺ solution concentration on the adsorption capacity and removal rate. The results showed that a desirable SFG adsorbent with the SFG dosage of 0.5 g, temperature of 25 °C, pH of 5, contact time of 720 min, and initial Cu²⁺ solution concentrations of 90 mg/L is recommended, of which the adsorption capacity is 31.5 mg/g with the removal rate being 92.76%. In addition, the adsorption performance of the SFG adsorbent is superior to that of pure sawdust and similar to that of the foamed geopolymer adsorbent, and it has the characteristics of higher strength, lower cost, and more environmental friendliness. This study indicated that the SFG adsorbents are feasible as adsorbents; meanwhile, this work can provide a scientific reference for the development of new bio-composite adsorbent materials, especially in the field of the treatment of heavy metal ions in wastewater. Full article