Solid Residue Research Articles

Selective leaching and recovery of phosphorus from incinerated sewage sludge ash with CaO addition.

Incinerated sewage sludge ash (ISSA) with high P2O5 content is a potential phosphorus resource that can replace the non-renewable phosphorus rocks. However, extracting phosphorus from ISSA using hydrometallurgical methods also dissolves a large amount of impurity metals into the leachate. Therefore, this study proposes a new method combining high-temperature reaction with CaO addition, selective leaching, and chemical precipitation for efficient and low-cost phosphorus recovery from ISSA. During thermal treatment at 1050°C, the addition of CaO significantly influenced the types and amounts of phosphate mineral phases in ISSA. When 20% CaO was added, the Al/Fe-phosphate phases were completely converted into acid-soluble Ca-phosphate phases, while Al and Fe were retained in acid-insoluble phases (e.g., Al- and Fe-containing oxides and silicates). Subsequently, by controlling the pH of acidic leachate (2.0 to 1.5), Ca-phosphate phases were selectively dissolved. At a pH of 1.5, better selective leaching was achieved, with a leaching efficiency of 94.71% for P and less than 10% for Al, Fe and Si. The XRF results showed that the majority of SiO2 (38.39%), Al2O3 (33.26%) remained in the post-leaching solid residue, which was expected to be further resource utilization. Without purification treatment to remove Al, Fe and Si, almost all phosphate ions were precipitated at pH=8.5, with P recovery efficiency of 94.07%. XRD results showed that the precipitate was mainly composed of HAP, with a P2O5 content of 37.51% and low level of contaminants, thereby realizing the effective recovery of phosphorus from ISSA.

Extraction and Characterization of Antioxidants and Cellulose from Green Walnut Husks

The ultrasound-assisted extraction process with microwave pretreatment was modeled and optimized to maximize the yield of antioxidants from green walnut husks using a response surface methodology with Box–Behnken design. In this design, the ultrasound-assisted extraction time (10–40 min), ultrasound-assisted extraction temperature (40–60 °C), and microwave pretreatment time (20–60 s) were selected as the factors, while the total antioxidant content was defined as the response. The solvent of choice for extracting antioxidants was 50% (v/v) ethanol. After optimization using the desirability function, an ultrasound-assisted extraction time of 23 min, ultrasound-assisted extraction temperature of 60 °C, and microwave pretreatment time of 60 s were proposed as the optimal conditions and their validity was verified. Under these conditions, the experimentally determined total antioxidant content was 3.69 g of gallic acid equivalent per 100 g of dry matter. In addition to phenolics, UHPLC–ESI–MS/MS analysis indicated the presence of lipids, quinones, terpenoids, and organic acids in the extract. After the antioxidant extraction, the solid residue was further processed to isolate cellulose in line with the concept of sustainable manufacturing. The structural characterization and hydration properties of cellulose were analyzed to identify its key features and assess its potential for value-added applications. The results demonstrate that green walnut husks are a valuable and cost-effective agro-industrial byproduct for extracting antioxidants and isolating cellulose. This aligns with the principles of a circular economy and the sustainable production of natural compounds.

Dry Magnetic Separation and the Leaching Behaviour of Aluminium, Iron, Titanium, and Selected Rare Earth Elements (REEs) from Coal Fly Ash

Coal fly ash (CFA) is a commercially viable source of alumina comparable to traditional bauxite deposits. Due to its high silica content and alumina in the refractory mullite phase, the most suitable processing technique is the sinter-H2SO4 leach process. However, this process is energy-intensive, has low selectivity for Al, and generates a secondary solid waste residue. To develop a sustainable process that is economically attractive, Al can be extracted with REEs, Ti, and Fe as saleable products, while secondary solid waste is regenerated for further applications to achieve high-value and high-volume utilisation of CFA. This study focused on the potential extraction of selected REEs (Ce, La, Nd, Y, and Sc), Al, Ti, and Fe, using dry magnetic separation and the sinter-H2SO4 leach process. XRD analysis showed that CFA is predominantly amorphous with crystalline mullite, quartz, and magnetite/hematite. Further analysis using SEM-EDS and TIMA showed Al-Si-rich grains as the predominant phase, with discrete REE-bearing grains (phosphates and silicates) and Fe-oxide (magnetite/hematite) grains. Traces of REEs, Ti, Ca, Si, and Fe were also found in the Al-Si-rich grains. Discrete Fe-oxide was recovered using dry magnetic separation, and up to 65.9% Fe was recovered at 1.05 T as the magnetic fraction (MF). The non-magnetic fraction (non-MF) containing quartz, mullite, and amorphous phase was further processed for preliminary leaching studies. The leaching behaviour of Al, Ti, Fe, and the selected REEs was investigated using the direct H2SO4 and sinter-H2SO4 leaching processes. The maximum extraction efficiency was observed using the sinter-H2SO4 leach process at 6 M H2SO4, a 1:5 solid-to-liquid ratio, 70 °C, and a residence time of 10 h, yielding 77.9% Al, 62.1% Fe, 52.3% Ti, and 56.7% Sc extractions. The extraction efficiencies for Ce, La, Nd, and Y were relatively lower at 23.2%, 27.6%, 11.3%, and 11.2%, respectively. Overall, the results demonstrate that the extraction of REEs using the sinter-H2SO4 leach process is strongly influenced by the complex CFA phase composition and the possible formation of insoluble calcium sulphates. Appreciable extraction of Al, Fe, Ti, and Sc was also observed, suggesting a potential two-step leaching process for the extraction of REEs as a feasible option for the industrial recovery of multiple saleable products.

Fractionation of High-Yield Noncondensed Lignin and Glucan Oligomers from Lignocellulose in a Novel Biphasic System.

Effective fractionation of lignocellulose into hemicellulose, cellulose, and lignin is the precondition for full-component valorization. Generally, harsh reaction conditions are used to improve fractionation efficiency, which leads to severe lignin condensation and inhibits its value-added applications. To address this issue, a novel biphasic system consisting of molten salt hydrates (MSHs) and n-butanol was developed for birch fractionation. After the removal of hemicellulose in dilute acid, the solid residue composed of cellulose and lignin was carried out in biphasic system conversion. Cellulose was selectively converted into 73.3% yield of glucan oligomers and 16.8% glucose in the MSH phase, while lignin was in situ-extracted into the n-butanol phase with a high yield of 98.1%. Mechanism studies revealed that the in situ extraction together with Cα-OH group modification by n-butanol synchronously protected lignin β-O-4 linkages from cleavage, resulting in a high β-O-4 content of 53.7%, indicating that 87.7% of β-O-4 linkages in birch has been preserved. After depolymerization, a promising monophenol yield of 22.4% was obtained, which was 81.5% of the theoretical maximum monophenol yield obtained from birch. This fractionation strategy can also be used in softwood and herbaceous, showing a splendid separation efficiency as well as a high yield of noncondensed lignin production.

Profiling Key Phytoconstituents in Screw-Pressed Nigella Solid Residue and Their Distribution in Products and Byproducts During Oil Processing

Nigella sativa L. (generally known as black cumin) is a medicinal plant prized for its therapeutic and nutritional benefits. Its seed oil is used extensively in pharmaceuticals, nutraceuticals, cosmetics, and cooking. However, extracting oil to satisfy the world’s needs leaves behind plenty of solid residues. The seeds of Nigella are loaded with health-benefiting phytoconstituents, but so might their extraction residues. While much research on seeds and oil has been carried out, there is relatively little information about solid residue, particularly regarding health-benefiting phytoconstituents. Additionally, there is a knowledge gap relating to how phytoconstituents transfer from seeds to solid residue during oil extraction and any loss of key phytoconstituents that may occur during this transfer. Understanding the health-benefiting phytoconstituents in Nigella solid residue is crucial for unlocking its full potential for value-added applications in health and nutrition. Moreover, understanding the dynamics of these phytoconstituent transfers is essential for optimizing extraction processes and preserving the nutritional and therapeutic value of the derived products. Therefore, this study investigated the composition of the screw-press solid residues of different Nigella genotypes grown under similar environmental conditions. The results showed moderate variation in the levels of potential health-benefitting phytoconstituents in Nigella solid residues regarding total phenolic content (TPC) (720.5–934.8 mg GAE/100 g), ferric reducing antioxidant capacity (FRAP) (853.1–1010.5 mg TE/100 g), cupric reducing antioxidant capacity (CUPRAC) (3863.1–4801.5 mg TE/100 g), thymoquinone (TQ) (156.0–260.1 mg/100 g), saturated fatty acid (SFA) (2.0–2.2 mg/g), monounsaturated fatty acid (MUFA) (2.0–3.6 mg/g), and polyunsaturated fatty acid (PUFA) (8.2–12.1 mg/g). Notably, TPC, FRAP, and CUPRAC had high transfer rates into the solid residue (78.1–85.9%, 65.4–75.7%, and 84.5–90.4%, respectively), whereas TQ, SFA, MUFA, and PUFA showed lower transfer rates (15.9–19.3%, 7.5–8.9%, 12.0–18.3%, and 6.5–7.5%, respectively). When summing the values of individual phytoconstituents transferred into oil and solid residue from their respective seeds during processing, it was found that only 80.6–88.3% of TPC, 74.2–84.4% of FRAP, 86.3–92.3% of CUPRAC, 54.4–64.9% of TQ, 68.5–92.4% of SFA, 76.2–90.6% of MUFA, and 51.6–76.6% of PUFA were transferred from the total value present in their respective seeds.

A ternary deep eutectic solvent for efficient biomass fractionation and lignin stabilization.

The efficient isolation and lignin stabilization are critical to the fractionation process of lignocellulosic biomass, enabling the subsequent valorization of both carbohydrates and lignin. In this study, a ternary deep eutectic solvent pretreatment system with outstanding reusability has been developed. Under optimal conditions (ChCl: MT: p-TsOH=1:1:0.5, 120°C, 60min), the system efficiently removed 94.66% of hemicellulose and 95.74% of lignin while retaining 84.50% of cellulose. Glucose was obtained from the cellulose-rich solid residue via enzymatic hydrolysis, achieving an 87.12% yield. This DES system inhibits lignin condensation through a dual mechanism of α-etherification and intermolecular forces (π-π stacking and hydrophobic interaction). The recovered lignin exhibits a low molecular weight (922-1049g/mol), high phenolic hydroxyl content (2.57-3.37mmol/g), low polydispersity (1.54-1.61), and high purity (93.02%). Combined with its superior antioxidant activity and UV shielding properties, this lignin represents a promising new resource with potential applications.

Effect of wood chips and wood board-ends of Gmelina arborea on yields and process of slow pyrolysis using a semi-industrial reactor prototype

Pyrolysis of biomass residues can generate savings in the value chains of forest products due to the potential uses of its products in the forestry sector. The aim of this study was to determine the performance during slow pyrolysis process and the yields of different products of two types of residues, wood chips and solid wood board-ends from Gmelina arborea. Results showed no significant differences in yields of charcoal (26 to 28%), wood vinegar (28 to 30%) and non-condensable gases (37%), but bio-oil yield was higher for the solid wood board-ends residues (7.7%). The evaluation of energy charcoal characteristics and wood vinegar was similar for two types of residues. So, results suggest that two types of residues provided similar charcoal, condensable and non-condensable gases yields, but solid board-ends are recommended to obtain higher yield of bio-oil and complete the process in less time. Charcoal and vinegar characteristic were affected by type of residues.

Grape Pomace: A Review of Its Bioactive Phenolic Compounds, Health Benefits, and Applications.

The wine industry generates high amounts of waste, posing current environmental and economic sustainability challenges. Grape pomace, mainly composed of seeds, skins, and stalks, contains significant amounts of bioactive compounds and constitutes the main solid residue of this industry. Various strategies are being explored for its valorization, from a circular economy perspective. This review provides an updated overview of the composition of grape pomace from winemaking, highlighting sustainable methodologies for extracting phenolic compounds and their potential health benefits, including antioxidant, antimicrobial, antidiabetic, cardioprotective, antiproliferative, anti-aging, and gut health properties. Furthermore, this review explores the potential applications of this agro-industrial waste and its extractable compounds across the food, cosmetic, and pharmaceutical sectors.

Green coal and lubricant via hydrogen-free hydrothermal liquefaction of biomass

Biocrude derived from biomass via hydrothermal liquefaction (HTL) is a sustainable substitute for petroleum to obtain energy and biochemicals. Upgrading biocrude inevitably faces the trade-off between consuming large amounts of hydrogen via hydrotreating and high yield of solid residue without additional hydrogen. In this work, we report a non-hydrogenated refinery paradigm for nearly complete valorization (~90%), via co-generating green coal and bio-lubricant. The obtained green coal has higher heating values comparable to commercial coals, with a lower fuel ratio and reduced ash content. Viscosity of upgraded vacuum distillate is comparable to that of a lubricant oil. A life cycle assessment confirms 28% reduction in greenhouse gas emission and 35% reduction in energy input of this paradigm compared with conventional hydrotreating biorefinery. This approach presents an environmentally friendly, safe and convenient paradigm for biocrude refining from huge biowaste towards carbon-neutral society.

Potential of Ionizing Radiation Application for Reducing Environmental Risks Related to Solids Residues

The enormous amount of solids residues and related cost for a suitable disposal have increased in megacities as São Paulo and Buenos Aires. Inovative technologies may be used in order to face managing progams with inovative techniques for for recycling or recover of materials. Gamma radiation was applied in laboratory scale for two different types of residues: fungi control in vehicular air filters, and for rat bedding waste (RBW) disinfection. Both materials may be used after irradiation and the radiation doses required will be discussed. Part of experiments carried out in Argentina evidenced the suitable use of vermicomposting for growing Calendula officinalis. Radiation doses from 10 kGy up to 30 kGy were tested for controlling microorganisms during the projects and were very effective. For filters disinfection experiments, DNA sequencing analysis for the fungi that survived after irradiation not only confirmed the presence of Penicillium, Fusarium and Aspergillus (toxigenic), fungi but also improved the data: the contamination included Aspergillus niger, Aspergillus flavus, Penicillium glabrum specie complex and Fusarium incarnatum-equiseti specie complex.

Rapid electrothermal upcycling hexachlorobutadiene (HCBD) polluted distillation residue into turbostratic graphene for enhanced electromagnetic wave absorption.

The trichloroethylene production industry generates high-boiling-point solid residues during rectification, which contain high concentrations of chlorinated contaminants, particularly hexachlorobutadiene (HCBD). Traditionally, these distillation residues are managed through co-incineration or landfilling, leading to environmental and economic challenges. In this study, we present a rapid and environmentally friendly electrothermal approach for both detoxifying and upcycling distillation residue into graphene-based electromagnetic wave (EMW) absorbing materials. By employing a DC power pulse discharge with a 10 s duration, we achieved over 99 % HCBD degradation efficiency. Characterization results indicate that the thermal shock transforms the distillation residue into high-value turbostratic pulse graphene (tPG). This tPG, featuring a unique structure, demonstrates substantial potential as an EMW absorber, with an effective absorption bandwidth of 3.9 GHz and a reflection loss of -42.0 dB at a minimal matching thickness of 1.6 mm. The method offers a sustainable, cost-effective solution for hazardous waste management, combining rapid processing with high-value material production.

Effect of Elemental Iron Containing Bauxite Residue Obtained After Electroreduction on High-Pressure Alkaline Leaching of Boehmitic Bauxite and Subsequent Thickening Rate.

The use of reduction leaching in the production of alumina from bauxite by the Bayer process in order to decrease the amount of waste (bauxite residue) by adding elemental iron or aluminum, as well as Fe2+ salts and organic compounds in the stage of high-pressure leaching, requires the purchase of relatively expensive reagents in large quantities. The aim of this study was to investigate the possibility of the use of electrolytically reduced bauxite residue (BR) as a substitute for these reagents. Reduced BR was obtained from Al-goethite containing BR using a bulk cathode in alkaline suspension. The degree of deoxidation of Fe3+ compounds was 55% after 2 h of electrolysis with a current yield of more than 73%. The addition of reduced BR according to the shrinking core model leads to a change in the limiting stage of the high-pressure boehmitic bauxite leaching from a surface chemical reaction to internal diffusion. The activation energy decreased from 32.9 to 17.2 kJ/mol by adding reduced red mud. It was also shown that the addition of reduced BR increased the rate of thickening of the slurry after leaching by a factor of 1.5 and decreased the Na2O losses by 15% without the addition of lime. The solid residue was examined by means of X-ray diffraction analysis and scanning electron microscopy to confirm the presence of magnetite and elemental iron. A preliminary techno-economic analysis was carried out to assess the applicability of the proposed process.

Effect of Hydrolysate Derived from Subcritical Seawater Treatment of Buckwheat Waste on the Growth of Lettuce (Lactuca sativa L.).

This study explores the effects of a subcritical seawater treatment (SST) on buckwheat waste (BW), and the use of the hydrolysate as a liquid fertilizer to improve the growth of lettuce (Lactuca sativa L.). Three temperature treatments (110 °C, 170 °C, 230 °C) were used for the SST, and the ionic composition in the seawater achieved the depolymerization and degradation of BW. The X-ray diffraction of the residual solids showed that the structure of BW was destroyed. Compared with seawater, the hydrolysate contained higher amounts of elements beneficial to plant growth, such as N, P, K, and organic compounds such as phenolics and sugars, as a result of the degradation of BW caused by the SST. The hydrolysate was tested as a liquid fertilizer (treatments H110°C, H170°C, H230°C) to irrigate lettuce. The content of proteins, phenolics, and chlorophyll, as well as the weight of the lettuce in the H110°C and H170°C treatments, were significantly higher than those in the seawater and the H230°C irrigation treatments (p < 0.05). The hydrolysate from the SST of BW, being rich in various organic and inorganic nutrients, can act as a liquid fertilizer that promotes the growth of lettuce, whereas hydrolysate from higher SST temperatures might inhibit the growth of lettuce, because of the excessive total nitrogen and organic acid.

Optimization of the production of grade A liquid smoke from Patchouli solid residue using a distillation-adsorption process

&lt;p&gt;Patchouli cultivation in Lhokseumawe, Aceh Province, produces a significant amount of biomass, with approximately 96%–98.5% of the raw material ending up as solid residue after the oil distillation process. This waste is often discarded or burned, leading to environmental problems. However, this residue is rich in compounds derived from the breakdown of lignocellulose and can be pyrolyzed to produce liquid smoke. Liquid smoke contains valuable phenols, acids, and carbonyls but may also generate harmful byproducts such as polycyclic aromatic hydrocarbons (PAHs). This study aimed to optimize the production of grade A liquid smoke through purification using a distillation and adsorption process. Pyrolysis of patchouli residue was conducted at 400 ℃ to produce liquid smoke. Furthermore, the raw liquid smoke was purified by distillation and adsorption. The distillation process was conducted at a temperature range (X&lt;sub&gt;1&lt;/sub&gt;) of 150–200 ℃ for 30–90 min (X&lt;sub&gt;2&lt;/sub&gt;). The weight of activated biochar used during the adsorption process varied between 5 and 15 g (X&lt;sub&gt;3&lt;/sub&gt;). The experimental design was carried out using Design Expert version 13. Research findings indicate that the optimal condition for liquid smoke was achieved with the equation Y = 1.26 + 0.53X&lt;sub&gt;1&lt;/sub&gt; + 0.0319X&lt;sub&gt;2&lt;/sub&gt; + 0.8023X&lt;sub&gt;3&lt;/sub&gt; – (4.91X&lt;sub&gt;1&lt;/sub&gt;)&lt;sup&gt;2&lt;/sup&gt; – (0.0015X&lt;sub&gt;2&lt;/sub&gt;)&lt;sup&gt;2&lt;/sup&gt; – (0.2147X&lt;sub&gt;3&lt;/sub&gt;)&lt;sup&gt;2&lt;/sup&gt; – 0. 0644 X&lt;sub&gt;1&lt;/sub&gt;X&lt;sub&gt;2&lt;/sub&gt; – 0.0327X&lt;sub&gt;1&lt;/sub&gt;X&lt;sub&gt;3&lt;/sub&gt; + 2.15X&lt;sub&gt;2&lt;/sub&gt;X&lt;sub&gt;3&lt;/sub&gt;. The best results were obtained at a distillation temperature of 175 ℃, a duration of 90 minutes, and using 13.4 g of activated carbon, which resulted in a high total phenol yield of 8.06%. The produced liquid smoke was classified as grade A, with a yield of 74.33%, a density of 0.9928 g/m³, a viscosity of 1.6203 cP, and a pH of 3.32. This research highlights an eco-friendly solution for valorizing patchouli waste, transforming it into a product with a wide range of applications as a food preservative, flavor enhancer, and medicinal agent.&lt;/p&gt;

Produção de biogás com resíduos sólidos gerados na produção de bioetanol utilizando biomassa da bananicultura

ABSTRACT Santa Catarina is a significant banana producer, responsible for 722 tons annually. For every 1,000 kg of bananas harvested, approximately 3,000 kg of pseudostem, 650 kg of peels, and 350 kg of rejected fruit are generated. Studies have evaluated the use of banana residues for bioethanol production. Solid residues like banana pseudostem bagasse, banana peels, and vinasse (fermented broth residue) are produced during this process. This study aimed to quantify and characterize these residues for biogas and methane production. Banana peels and vinasse were more suitable for containing lower total solids content and favorable C:N (carbon:nitrogen) ratios (10-30:1), yielding higher biochemical potential of methane (260 mLCH4 gvs -1) compared to banana pseudostem bagasse (201 mLCH4 gvs -1). However, vinasse had a high hydrogen sulfide content (0.0783%), necessitating desulphurization for safe biogas use. The results indicate that banana pseudostem bagasse, banana peels, and vinasse have substantial potential for biogas and methane production due to their high degradation rates. The biogas composition meets the criteria for use, with adequate methane and carbon dioxide concentrations, highlighting the viability of these residues for energy generation and contributing to sustainability in banana cultivation.

Roasting-Water Leaching-Slag Cleaning Process for Recovery of Valuable Metals from Li-ion Battery Scrap

Abstract Waste lithium-ion batteries (LIBs) are important secondary sources of valuable materials, including Critical Raw Materials (CRMs) like lithium, cobalt, manganese, and graphite, as defined by the European Union (EU). LIBs also contain nickel and copper, classified as Strategic Raw Materials by the EU since 2023. Significant efforts have been made to develop efficient recycling processes for waste LIBs, with pyrometallurgical processes playing a key role. These technologies are relatively mature, with high adaptability for different raw materials and involve smelting waste batteries above the melting points of battery components, followed by separating metals through reduction reactions. This method efficiently recovers cobalt, copper, and nickel as a metal alloy or matte, while lithium and manganese are lost in the slag phase. The goal of this work was to enhance the recovery of valuable battery metals by combining hydro- and pyrometallurgical processes. Mechanically prepared battery black mass underwent selective sulfation roasting to convert LiCoO2 and Mn-oxides into Li, Co, and Mn sulfates. After roasting, the battery scrap was leached in distilled water at 60 °C, recovering 95% of lithium, 61% of manganese, and 35% of cobalt. The solid leaching residue was then mixed with industrial Ni-slag and biochar. Two experimental series were carried out, one with the addition of industrial Ni-concentrate and one without. The smelting experiments were conducted at 1350 °C in flowing argon atmosphere as a function of time (5–60 min) to investigate the reduction behavior of battery metals. The results show that Co and Ni from the slag and leach residue can be efficiently recovered in the slag cleaning stage. Graphical Abstract

Geochemistry and Mineralogy of Precipitates from Passive Treatment of Acid Mine Drainage: Implications for Future Management Strategies

Traditional mining activities in Zaruma-Portovelo (SE Ecuador) have led to high concentrations of pollutants in the Puyango River due to acid mine drainage (AMD) from abandoned waste. Dispersed alkaline substrate (DAS) passive treatment systems have shown efficacy in neutralizing acidity and retaining metals and sulfates in acidic waters, achieving near a 100% retention for Fe, Al, and Cu, over 70% for trace elements, and 25% for SO42−. However, significant solid residues are generated, requiring proper geochemical and mineralogical understanding for management. This study investigates the fractionation of elements in AMD precipitates. Results indicate that Fe3+ and Al3+ predominantly precipitate as low-crystallinity oxyhydroxysulfate minerals such as schwertmannite [Fe3+16(OHSO4)12–13O16·10–12H2O] and jarosite [KFe3+3(SO4)2(OH)6], which retain elements like As, Cr, Cu, Pb, and Zn through adsorption and co-precipitation processes. Sulfate removal occurs via salts like coquimbite [AlFe3(SO4)6(H2O)12·6H2O] and gypsum [CaSO4·2H2O]. Divalent metals are primarily removed through carbonate and bicarbonate phases, with minerals such as azurite [Cu(OH)2·2CuCO3], malachite [Cu2(CO3)(OH)2], rhodochrosite [MnCO3], and calcite [CaCO3]. Despite the effectiveness of DAS, leachates from the precipitates exceed regulatory thresholds for aquatic life protection, classifying them as hazardous and posing environmental risks. However, these residues offer opportunities for the recovery of valuable metals.

Strategic Resource Extraction and Recycling from Waste: A Pathway to Sustainable Resource Conservation

This study examines calcium extraction from Bottom Ash (BA) and the use of Solid Residue (SR) as a substitute for White Lump Clay (WLC) in brick production. Experimental analyses identified calcium and silicon as the main elements in BA, with 50% of calcium carbonate recovered through leaching. SR was a viable alternative to WLC in ceramic bricks, as SEM-EDS and FTIR analyses revealed changes in composition and microstructure. This approach promotes circular economy principles by recovering resources and reducing waste. Calcium extraction from BA can produce 29,000 tons of CaCO3 annually for industrial use, while substituting SR for WLC in brick production could replace 30% of clay, saving 1500 tons of clay and producing millions of bricks annually. Less than 50% of incinerated Municipal Solid Waste (MSW) would require landfilling. The process supports sustainable construction by conserving natural resources, reducing landfill waste, and lowering CO2 emissions. It offers annual cost savings of 2,639,250 USD and preserves 74,812.5 tons of resources through waste and clay reduction. By demonstrating a scalable model for waste valorization, this research aligns with global goals for sustainable development, resource efficiency, and ecological balance.

Comparative Analysis of Freeze-Dried Pleurotus ostreatus Mushroom Powders on Probiotic and Harmful Bacteria and Its Bioactive Compounds.

Pleurotus ostreatus (oyster mushroom) holds excellent promise worldwide, bringing several opportunities and augmenting the tool sets used in the biotechnology field, the food industry, and medicine. Our study explores the antimicrobial and probiotic growth stimulation benefits of freeze-dried P. ostreatus powders (OMP-TF, oyster mushroom powder from the total fresh sample; OMP-CSR, oyster mushroom powder from the cooked solid residue; OMP-CL, oyster mushroom powder from the cooked liquid), focusing on their bioactive compounds and associated activities. Our research examined polysaccharide fractions-specifically total glucans and α- and β-glucans-alongside secondary metabolites, including polyphenols and flavonoids, from freeze-dried mushroom powders. Additionally, carbon nanodots (CNDs) were also characterized. The growth inhibition was tested against Escherichia coli and Staphylococcus epidermidis, while the capacity for stimulating probiotic growth was evaluated using Lactobacillus plantarum and Lactobacillus casei. Evidence indicates that OMP-CL and OMP-CSR exhibit significant antimicrobial properties against S. epidermidis Gram-positive bacteria. OMP-CL notably promoted the growth of L. casei. OMP-CL, containing the most significant number of CNDs, has shown to be a valuable source for gut microbiota modulation, with its antimicrobial and probiotic-stimulating efficacy. However, further in vitro and in vivo studies should be performed to explore CNDs and their behavior in different biological systems.

Processing of chalcopyrite concentrate by sulfating roasting

Chalcopyrite (CuFeS2) is one of the primary minerals processed on an industrial scale for copper production and often dominates copper concentrates sent for pyrometallurgical processing. This study demonstrates the efficient and selective extraction of copper from chalcopyrite concentrate through sulfating roasting, sulfuric acid leaching, and solvent extraction. At a roasting temperature of 700 °C for 1.5 h, chalcopyrite fully decomposes into hematite (Fe2O3) and chalcanthite (CuSO4). Leaching the calcine with a 0.02 M sulfuric acid solution transfers most of the copper to the aqueous phase, while iron concentrates in the solid residue. Additionally, precious metals concentrate in the residue after leaching of the calcine, with the following content in g/t: Pd – 41.61, Pt – 5.65, Ag – 96.22, Au – 4.81. The removal of iron from the leach solution using solvent extraction with di-2-ethylhexyl phosphoric acid was highly effective: with a 25 % extractant solution and an organicto-aqueous ratio of 1:1 over two stages, the iron concentration in the aqueous phase dropped from 3.05 to 0.01 g/dm3, and with an organic-toaqueous ratio of 1:2 over four stages, it decreased to 0.006 g/dm3. After iron purification and solution evaporation, copper sulfate was obtained with the following composition (%): CuSO4·5H2O – 99.84 (equivalent to 25.42 % copper), Ni – 0.014, Al – 0.007, Fe – 0.0003, As – 0.0002.