Search Results (273)

The bioactive properties of a phenolic extract (PE) obtained from olive mill vegetation water (OVW) in powder formulation were utilized to enrich a meat analog composed of lentils and champignon mushrooms. The primary phenolic compounds in this extract were oleacein, verbascoside, and hydroxytyrosol. The effects on the final product were assessed over eight days of storage at 4 °C ± 2 under 12 h of light. The control samples were compared with two meat analogs enriched with ascorbic acid (AA) at 5 g kg⁻¹ and one enriched with PE at 30 g kg⁻¹. The physicochemical parameters (pH, aw, color, texture, and total phenol content), antioxidant activity, microbial assessment, and sensory evaluations of meat analog samples were evaluated at three different time points (T0, T4, T8) during shelf life. The PE-enriched meat analogs maintained a relatively high and stable phenolic concentration throughout their shelf life, significantly enhancing the antioxidant activities of the final product. The addition of PE also influenced the growth of Enterococcus spp., Lactococcus spp., and Lactobacillus spp. during storage. The results of the triangular test indicated perceptible differences between AA and PE meat analogs. Meanwhile, the quantitative descriptive analysis (QDA) emphasized notable enhancements in odor and texture characteristics for PE-enriched samples. Plant-based meat analogs can benefit from the effective use of PE (antioxidant and sensory properties), supporting the sustainable reuse of olive oil by-products. Full article

p-toluenesulfonic acid (pTSA) was used for the synthesis of porous silica xerogels while applying different synthesis conditions. Key parameters included acid concentration, drying temperature and the method of acid removal. The resulting organic–inorganic composites were investigated by nitrogen physisorption, X-ray powder diffraction (XRD), solid-state NMR and thermal analysis. The results demonstrated that both the drying temperature and quantity of the pTSA significantly influenced the pore structure of the xerogels. The utilization of such strong acids like pTSA yielded high surface area and pore volume, as well as narrow pore size distribution. Environmentally friendly template removal by solvent extraction produced materials with superior textural properties compared to traditional calcination, enabling the recovery and reuse of pTSA with over 95% efficiency. A selected mesoporous silica xerogel was modified by a simple two-step post-synthesis procedure with 1-(2-Hydroxyethyl) piperazine (HEP). High CO₂ adsorption capacity was determined for the HEP-modified material in dynamic conditions. The isosteric heat of adsorption revealed the stronger interaction between functional groups and CO₂ molecules. Total CO₂ desorption could be achieved at 60 °C. Leaching of the silica functional groups could not be detected even after four consecutive adsorption cycles. These findings provide valuable insights into the sustainable synthesis of tunable piperazine-modified mesoporous silica xerogels with potential applications in CO₂ capture. Full article

Valorisation of spent yeast biomass post-fermentation requires energy-intensive autolysis or enzymatic hydrolysis that reduces the net benefit. Here, we present a simple and reproducible method for generating functional yeast extract recycled from Komagataella phaffii biomass without a requirement of a pre-treatment process. Spent yeast pellets from fermentations were freeze-dried to produce a fine powder that can be used directly at low concentrations, 0.0015% (w/v), together with 2% peptone (w/v), to formulate complete media ready for secondary fermentations. This media formulation supported growth rates of yeast culture that were statistically indistinguishable (p-value > 0.05) from cultures grown in standard YPD media containing commercial yeast extract, and these cultures produced equivalent titres of recombinant β-glucosidase (0.998 Abs_405nm commercial extract vs. 0.899 Abs_405nm recycled extract). Additionally, nutrient analyses highlight equivalent levels of sugars (~23 g/L), total proteins, and cell yield per carbon source (~2.17 g) with this recycled yeast extract media formulation when compared to commercial media. This method reduces process complexity and cost and enables the circular reuse of yeast biomass. The protocol is technically straightforward to implement, using freeze drying that is commonly available in research laboratories, representing a broadly applicable and sustainable alternative to conventional media supplementation that achieves a circular approach within the same fermentation system. Full article

Coal gangue, an industrial byproduct of coal mining, was traditionally utilized in concrete production as a coarse aggregate. However, recent advancements have expanded its application by processing it into fine powder for use as a supplementary cementitious material (SCM), partially replacing cement. This approach not only enhances the sustainable reuse of coal gangue but also contributes to reducing cement consumption and associated carbon emissions. Nevertheless, the incorporation of coal gangue may adversely affect the mechanical strength and long-term durability of concrete. This review provides a systematic analysis of recent research on coal gangue-modified concrete. It begins by classifying the functional roles of coal gangue in concrete mixtures, followed by a critical evaluation of its impact on mechanical properties and durability—both as an aggregate an as a mineral admixture. When 30% of the aggregate is replaced with activated coal gangue, the average compressive strength of concrete increases by 15%. When coal gangue replaces less than 20% of the cement, the compressive strength of concrete can reach 95% of the reference strength. Second, the review evaluates the modification effects of various mineral admixtures, elucidating their mechanisms for enhancing mechanical properties and durability in coal gangue-based concrete. Finally, it examines the underlying interaction mechanisms between these admixtures and coal gangue, while identifying key future research directions for optimizing admixture formulations. By providing a comprehensive and critical analysis of current research, this paper serves as a valuable reference for developing high-performance coal gangue concrete with increased substitution rates and tailored admixture systems. Ultimately, this work advances the design of sustainable, low-cement concrete using industrial byproducts, enabling performance-driven applications and supporting next-generation green construction materials. Full article

The dual benefit of wastewater and microalgal biomass is a major advantage of high-rate algal ponds, enabling the environmental valorization of these byproducts. This research explored the effect of treated wastewater on the agri-food species Hordeum vulgare (L.) and its associated weed, Emex spinosa (L.) Campd., along with the effects of algal biomass (primarily composed of Closterium, Chlorella, and Scenedesmus spp.) and Diplotaxis harra leaf powder. Initial pot trials applied microalgae and D. harra at 2, 4, and 6 g·kg⁻¹ soil, also confirming that the treated wastewater met reuse standards and did not affect plant growth. The combined treatment at 4 g·kg⁻¹ led to the highest H. vulgare increases in fresh weight (162.71%), root length (73.75%), and shoot length (72.87%), while reducing E. spinosa shoot and root lengths by 30.79% and 52.18%, and fresh weight by 68.24%. Subsequent field experiments using 1.26 t ha⁻¹ of 0.5-cm-applied D. harra and microalgae powders enhanced H. vulgare growth, while reducing the growth of E. spinosa. The reduction in E. spinosa growth was associated with increased electrolyte leakage and malondialdehyde content. These results support the integration of high-rate algal ponds into agriculture, promoting water reuse and reducing reliance on synthetic fertilizers and herbicides in barley production. Full article

Replacing virgin raw materials with recycled waste in construction products is a key strategy for advancing sustainable development. This study explores the partial substitution of commercial gypsum with powdered waste brick (WB) in gypsum mortars, assessing its impact on mechanical performance, water absorption, and environmental footprint. Mortars were prepared with 0%, 5%, 10%, 20%, and 30% WB by weight. Results indicate that a 20% replacement level enhances flexural strength by 56% and compressive strength by 33% at 28 days, compared to the reference mix. SEM and XRD analyses revealed no formation of new crystalline phases, suggesting that the performance improvement is primarily due to physical interactions and microstructural effects. However, at 30% WB, a significant reduction in adhesion strength was observed, falling below the typical threshold for gypsum-based coatings, which may constrain practical application at higher replacement levels. Environmental assessment showed that both CO₂ emissions and energy consumption decreased by up to 20% with a 30% substitution. A 20% WB content is therefore proposed as the optimal compromise between mechanical performance and environmental benefit. This approach supports circular economy principles by promoting the reuse of ceramic construction waste in the development of new sustainable materials. Full article

The construction industry is a major source of environmental degradation as it is responsible for a significant share of global CO₂ emissions, especially from cement and aggregate consumption. This study fills the need for sustainable construction materials by developing and evaluating a low-carbon fiber-reinforced concrete (FRC) made of steel slag powder (SSP), processed recycled concrete aggregates (PRCAs), and waste steel rivet fibers (WSRFs) derived from industrial waste. The research seeks to reduce dependency on virgin materials while maintaining high values of mechanical performance and durability in structural applications. Sixteen concrete mixes were used in the experimental investigations with control, SSP, SSP+RCA, and RCA, reinforced with various fiber dosages (0%, 0.2%, 0.8%, 1.4%) by concrete volume. Workability, density, compressive strength, tensile strength, and water absorption were measured according to the appropriate standards. Compressive and tensile strength increased in all mixes and the 1.4% WSRF mix had the best performance. However, it was found that a fiber content of 0.8% was optimal, which balanced the improvement in strength, durability, and workability by sustainable reuse of recycled materials and demolition waste. It was found by failure mode analysis that the transition was from brittle to ductile behavior as the fiber content increased. The relationship between compressive, tensile strength, and fiber content was visualized as a 3D response surface in order to support these mechanical trends. It is concluded in this study that 15% SSP, 40% PRCA, and 0.8% WSRF are feasible, specific solutions to improve concrete performance and advance the circular economy. Full article

This article presents an innovative approach as a potential alternative for the reuse of discarded green mussel shells from the fishing and food sectors. This technique entails the use of harmless chemicals and the consumption of energy in an efficient manner to generate shell powder of different dimensions. The shell powder was categorized into three distinct sizes to investigate changes after heat treatment. SEM-EDS was used to analyze particle sizes before calcination and examine the microstructure of heated shell powder. FTIR spectroscopy was conducted to assess the purity of all sizes before and after calcination, showing excellent cleanliness suitable for practical applications. XRD spectroscopy was used to examine the crystal structure, while thermal characteristics and surface color changes during heat treatment were also analyzed due to their impact on final product quality. The variety in particle size enhances the potential for diverse industrial applications. Each size may be suitable for different artificial sand uses, as noted in the conclusion. The proposed method provides both environmental and economic advantages by converting shell waste into a sustainable substitute for artificial sand. It utilizes low-cost, readily available materials and aligns with circular economy principles by reducing shell waste accumulation and dependence on natural aggregates. Full article

The dairy industry generates significant amounts of wastewater, including microfiltration (MF) retentate, a byproduct thickened with organic and inorganic pollutants. This study focuses on the treatment of two times concentrated MF retentate using a hybrid system based on biological treatment in a sequential batch reactor (SBR) and adsorption on activated carbon. The first stage involved cross-flow microfiltration using a 0.2 µm PVDF membrane at 0.5 bar, resulting in reductions of 99% in turbidity and 79% in chemical oxygen demand (COD), as well as a partial reduction in conductivity. The second stage involved 24-h biological treatment in a sequential batch reactor (SBR) with activated sludge (activated sludge index: 80 cm³/g, MLSS 2500 mg/dm³), resulting in further reductions in COD (62%) and TOC (30%), as well as the removal of 46% of total phosphorus (TP) and 35% of total nitrogen (TN). In the third stage, the decantate underwent adsorption in a column containing powdered activated carbon (PAC; 1 g; S_(BET) = 969 m² g⁻¹), reducing the concentrations of key indicators to the following levels: COD 84%, TOC 70%, TN 77%, TP 87% and suspended solids 97%. Total pollutant retention ranged from 24.6% to 97.0%. These results confirm that the MF–SBR–PAC system is an effective, compact solution that significantly reduces the load of organic and biogenic pollutants in MF retentates, paving the way for their reuse or safe discharge into the environment. Full article

Asphalt plant reclaimed powder is a common solid waste in road engineering. Reusing reclaimed powder as filler holds significant importance for environmental protection and resource conservation. The key factors affecting the feasibility of reclaimed powder reuse are its acidity/alkalinity and cleanliness. Traditional evaluation methods, such as the methylene blue test and plasticity index, can assess reclaimed powder properties to guide its recycling. However, these methods suffer from inefficiency, strong empirical dependence, and high variability. To address these limitations, this study proposes a rapid and precise evaluation method for reclaimed powder properties based on Fourier transform infrared spectroscopy (FTIR). To do so, five field-collected reclaimed powder samples and four artificial samples were evaluated. Scanning electron microscopy (SEM), X-ray fluorescence spectroscopy (XRF), and X-ray diffraction (XRD) were employed to characterize their microphase morphology, chemical composition, and crystal structure, respectively. Subsequently, FTIR was used to establish correlations between key acidity/alkalinity, cleanliness, and multiple characteristic peak intensities. Representative infrared characteristic peaks were selected, and a quantitative functional group index (Is) was proposed to simultaneously evaluate acidity/alkalinity and cleanliness. The results indicate that reclaimed powder primarily consists of tiny, crushed stone particles and dust, with significant variations in crystal structure and chemical composition, including calcium carbonate, silicon oxide, iron oxide, and aluminum oxide. Some samples also contained clay, which critically influenced the reclaimed powder properties. Since both filler acidity/alkalinity and cleanliness are affected by clay (silicon/carbon ratio determining acidity/alkalinity and aluminosilicate content affecting cleanliness), this study calculated four functional group indices based on FTIR absorption peaks, namely the Si-O-Si stretching vibration (1000 cm⁻¹) and the CO₃²⁻ asymmetric stretching vibration (1400 cm⁻¹). These indices were correlated with conventional testing results (XRF for acidity/alkalinity, methylene blue value, and pull-off strength for cleanliness). The results show that the Is index exhibited strong correlations (R² = 0.89 with XRF, R² = 0.80 with methylene blue value, and R² = 0.96 with pull-off strength), demonstrating its effectiveness in predicting both acidity/alkalinity and cleanliness. The developed method enhances reclaimed powder detection efficiency and facilitates high-value recycling in road engineering applications. Full article

To reduce the carbon footprint of the concrete industry and promote a circular economy, this study explores the reuse of waste materials such as glass powder (GP) and nitrile rubber (NR) fibres in concrete. However, the inclusion of these waste materials results in lower compressive strength compared to conventional concrete, limiting their application to non-structural elements. To overcome this limitation, this study adopts the concept of confined concrete by developing concrete-filled steel tube (CFST) stub columns. In total, twelve concrete mix variations were developed, with and without steel tube confinement. GP was utilised at replacement levels of 10–30% by weight of cement, while NR fibres were introduced at 0.5% and 1% by volume of concrete. The findings demonstrate that the incorporation of GP and NR fibres leads to a reduction in compressive strength, with a compounded effect observed when both materials are combined. Steel confinement within CFST columns effectively mitigated the strength reductions, restoring up to 17% of the lost capacity and significantly improving ductility and energy absorption capacity. All CFST columns exhibited consistent local outward buckling failure mode, irrespective of the concrete mix variations. A comparison with predictions from existing design codes and empirical models revealed discrepancies, underscoring the need for refined design approaches for CFST columns incorporating sustainable concrete infill. This study contributes valuable insights into the development of eco-friendly, high-performance structural systems, highlighting the potential of CFST technology in facilitating the adoption of waste materials in the construction sector. Full article

This study explored the potential of reusing eggshell powders as a renewable activating agent for producing porous carbon materials from coffee husk. Carbonization and activation experiments were conducted by heating the samples at a rate of 10 °C/min up to 850 °C under a nitrogen atmosphere. A custom-designed double steel-mesh sample holder was used to hold approximately 2.0 g coffee husk on the top, with varying masses of eggshell at the bottom to achieve eggshells to coffee husk mass ratios of 2:1, 4:1, 6:1 and 8:1. The results demonstrated that CO₂ released from the thermal decomposition of the eggshell powder significantly enhanced pore development at 850 °C. Compared to the pore properties of carbon material produced without eggshell (e.g., BET surface area of 321 m²/g), the activated carbon samples exhibited substantially improved pore properties (e.g., BET surface area in the range of 592 to 715 m²/g). Furthermore, the pore characteristics improved consistently with increasing eggshell content. Observations by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Fourier-transform infrared spectroscopy (FTIR) confirmed the structural and chemical transformations of the resulting carbon materials. Under optimal carbonization-activation conditions, the resulting carbon materials derived from coffee husk exhibited microporous structures and slit-shaped pores, as indicated by the Type I isotherms and H4 hysteresis loops. Full article

The Scalable and Expeditious Additive Manufacturing (SEAM) process is an advanced additive manufacturing (AM) technique that relies on the optimization of metal powder suspensions to achieve high-quality 3D-printed components. This study explores the critical role of dispersants in enhancing the performance of stainless steel (SS) 420 metal powder suspensions for the SEAM process by improving powder loading, recyclability, flowability, and consequent final part density. The addition of dispersant allows for increased powder contents while preserving stable rheological properties, thereby enabling higher powder loading without compromising the rheological characteristics required in the SEAM process. Previously, our team implemented a two-step printing strategy to address the segregation issues during printing. Nonetheless, the semi-cured layer was not recyclable after printing, resulting in a significant amount of waste in the SEAM process. This, in turn, leads to a considerable increase in material costs. On the other hand, the addition of a dispersant has been shown to enhance suspension stability, enabling multiple cycles of reuse. This novel approach has been demonstrated to reduce material waste and lower production costs. The enhanced flowability guarantees uniform suspension spreading, resulting in defect-free layer deposition and superior process control. Moreover, the dispersant’s ability to impede particle agglomeration and promote powder loading contributes to the attainment of a 99.33% relative density in the final sintered SS420 parts, thereby markedly enhancing their mechanical integrity. These findings demonstrate the pivotal role of dispersants in refining the SEAM process, enabling the production of high-density, cost-effective metal components with superior material utilization and process efficiency. Full article

Polymer residues can be reused in civil construction by partially replacing mineral aggregates in concrete, thereby reducing the extraction of natural resources. This study aimed to evaluate the use of powdered poly (ethylene terephthalate) (PET) and polyethylene (PE) residues, accumulated in shaving-mill filters during the extrusion of multilayer films used in food packaging, in the production of sealing masonry blocks. The PET/PE residues were characterized by Fourier Transform Infrared Spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Cylindrical specimens were produced in which part of the sand, by volume, was replaced with 10, 20, 30, 40 and 50% polymer residue. The cylindrical specimens were evaluated for specific mass, water absorption and axial and diametral compressive strengths. The 10% content provided the highest compressive strength. This formulation was selected for the manufacture of concrete blocks, which were evaluated and compared with the specifications of ABNT NBR 6136:2014. The concrete blocks showed potential for applications without structural function and were classified as Class C. The results, in line with previous investigations on the incorporation of plastic waste in concrete, underscore the promising application potential of this strategy. Full article

This study systematically investigates the utilization of marble industry waste—waste marble powder (WMP) as partial cement replacement and waste marble aggregates (WMA) as partial fine aggregate replacement—in self-compacting concrete (SCC). A detailed experimental program evaluated the effects of various replacement levels (5%, 10%, and 20% for WMP; 20%, 30%, and 40% for WMA) on compressive strength and durability, particularly resistance to aggressive sulfuric acid environments. Results indicated that a 5% WMP replacement increased compressive strength by 4.9%, attributed primarily to the filler effect, whereas higher levels (10–20%) led to strength reductions due to limited pozzolanic activity and cement dilution. In contrast, WMA replacement consistently enhanced strength (maximum increase of 11.5% at 30% substitution) due to improved particle packing and aggregate-paste interface densification. Durability tests revealed significantly reduced compressive strength losses and mass loss in marble-containing mixtures compared to control samples, with optimal acid resistance observed at 20% WMP and 40% WMA replacements. A comprehensive life cycle assessment demonstrated notable reductions in environmental impacts, including up to 20% decreases in Global Warming Potential (GWP) at 20% WMP replacement. A desirability-based eco-cost-mechanical optimization—simultaneously integrating mechanical strength, environmental indicators, and production cost—identified the 10% WMP substitution mix as the most sustainable option, achieving optimal balance among key performance criteria. These findings underscore the significant potential for marble waste reuse in SCC, promoting environmental sustainability, resource efficiency, and improved concrete durability in chemically aggressive environments. Full article