Repurposing mineral processing waste offers both environmental and economic benefits, reducing the disposal burden while enabling mineral resource recovery. A magnetic adsorbent, with an Fe3O4 content of 71.0%, collected from waste copper converter slag was utilized to recover gold (Au3+) from chloride solution. The adsorbent was separated from the slag samples by crushing, grinding to an average particle size of 30 mu m, and magnetic separation. Batch adsorption experiments were performed to evaluate the effects of pH, contact time, chloride concentration, and initial gold concentration on gold uptake amount. The material recovered over 99% of gold from chloride solution under acidic conditions and in the near-neutral pH range. The gold sorption rate was also relatively fast and over 98% recovery was achieved after just 15 min of contact time. Increasing chloride concentration did not influence gold uptake. Parameter studies and spectrometric analyses suggest that chalcocite (Cu2S) and metallic copper present in magnetite slag reduced the gold chloride complex to metallic gold. These results suggest that converter magnetite slag is a potentially effective sorbent to recover gold from secondary sources due to its selectivity and low cost. Moreover, gold-loaded magnetite slag can be easily separated from the solution by magnetic separation and then recirculated to the smelting stage of copper processing to recover the deposited gold and other precious metals. Overall, this work highlights a pathway to transform waste into opportunity, reinforcing sustainability in mineral processing operations.

Acid mine drainage (AMD) is characterized by persistent acidity, high sulfate and dissolved metal concentrations. Sulfate-reducing bacteria (SRB) are attractive candidates for AMD remediation because dissimilatory sulfate reduction generates alkalinity while producing sulfide that can facilitate metal removal through precipitation. Extending these processes to acidic conditions has increased interest in acidophilic and acid-tolerant SRB (aSRB and atSRB), yet evidence from cultivation, molecular surveys and treatment systems has often been interpreted separately. This systematic review synthesized 53 culture-dependent, culture-independent, and treatment system studies from 2014 to 2024 to examine relationships among taxonomic occurrence, physiological capability, demonstrated low-pH sulfate reduction and treatment performance. Phylogenetic analysis showed that low-pH sulfate-reducing phenotypes were distributed across multiple lineages and 16S rRNA relatedness alone did not predict acid tolerance. Desulfosporosinus was the most consistently represented genus across studies, although its recurrence was influenced by cultivation strategies. Sulfate reduction was demonstrated below pH 3, with sustained low-pH activity most strongly supported by controlled reactor studies; approximately pH 4.0–5.5 emerged as a comparatively well-supported range, while activity at lower pH was more dependent on microbial physiology and experimental conditions. Low-pH sulfate reduction also emerged as a community-level process shaped by electron-donor use, metabolite turnover and complementary microbial functions, while treatment performance additionally depended on biomass retention, hydraulic conditions and sulfide management. The reviewed studies support a distinction between taxonomic presence, demonstrated activity and treatment contribution. Future work should prioritize standardized reporting of active sulfate-reduction conditions, stronger taxon-function validation and long-term field testing of low-pH sulfidogenic systems.

Microplastics (MPs) are emerging pollutants widespread in aquatic environments; however, their effects across the different life stages of aquatic organisms remain poorly understood. This systematic review integrates recent experimental results on the developmental, physiological, and neurobehavioral effects of MP exposure on zebrafish (Danio rerio), a popular model organism for ecotoxicology research. A PRISMA-guided search using Web of Science (WoS) and Scopus as databases generated 581 articles, which were screened to 60 eligible articles. The collated results showed that MP toxicity at various life stages of zebrafish was strongly related to the physicochemical properties of MPs and exposure conditions. In terms of developmental toxicity, peer-reviewed publications assessing specific MP physicochemical properties—polymer type, size, concentration, shape, and degree of aging—reported concentration-dependent effects, with increasing MP concentrations generally associated with growth inhibition, cardiac dysfunction, increased malformations, and lower hatching rate, particularly at ≥10 mg/L to ≥100 mg/L. However, several studies noted that under particle-based exposure scenarios, MP toxicity exhibited threshold-like or non-monotonic responses, attributed to aggregation, bioavailability, and uptake dynamics. Weathered and artificially aged MPs exhibited higher embryotoxicity and neurodevelopmental toxicity, including changes in gene expression of neurons, decreased integrity of motor neurons, and impaired retinal development, compared with “virgin” MPs. In terms of physiological endpoints, oxidative imbalance like changes in the activity of antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx)), lipid peroxidation, inflammation, and disruption of tight junctions have been reported as key toxicity pathways. Chronic MP exposure in zebrafish also caused changes in the gut microbiota, hepatic metabolism, endocrine disruption, reproductive damage, thyroid function disruption, and genotoxicity in zebrafish. In terms of neurobehavioral effects, changes in locomotor activity, anxiety response, neurotransmitter homeostasis, and acetylcholinesterase function, have been observed, in both larvae and adults, with a potentiation effect in aged MP exposure. Finally, this systematic review found major limitations for inter-study comparisons because of inconsistencies and differences in methodology applied related to MP concentration, simulation of natural MP aging, and MP dose measurements.

Municipal solid waste incineration fly ash (MSWI-FA), a by-product of burning wastes at high temperatures for volume and mass reduction, is a promising, cost-effective, and sustainable adsorbent for phosphate (PO43–) removal due to its significant calcium oxide (CaO), silicon dioxide (SiO2), aluminum oxide (Al2O3), and iron oxide (Fe2O3) contents, which facilitate phosphate removal via adsorption and chemical precipitation reactions. This study investigates the efficiency of MSWI-FA for phosphate removal from wastewater through batch and continuous flow column experiments, with a particular focus on the influence of particle size, pH, contact time, and hydraulic retention time (HRT). Batch experiments showed that the –75  µm fraction achieved the highest phosphate removal (∼70%) at pH 6, with adsorption behavior controlled by chemisorption. Continuous flow column experiments revealed that a 25  mm bed provided 91.3% removal, while a 15  mL/min flow rate achieved ∼ 99% removal within 480 min. Fourier transform infrared spectroscopy (FTIR) analysis supported a dual removal mechanism of phosphate: (i) surface adsorption through hydroxyl and metal oxide functional groups (e.g., Al–OH, Fe–OH, Si–OH) (IR bands at ∼ 1050, ∼560  cm–1; ∼3000–3700  cm–1), and (ii) chemical precipitation with calcium ions forming calcium phosphate compounds (IR band at ∼ 1300–1600  cm–1). These findings underscore the practical potential of MSWI-FA in wastewater treatment and support its alignment with circular economy goals through waste valorization.

Rare Earth Elements (REEs) are crucial components driving technological advancements due to their unique properties, and are currently confronted with a growing demand crisis and supply constraints. This study investigates the recovery of REEs using modified diglycolamide and carbamide resin TK221 through extraction chromatography. The extraction behaviour of Nd(III) and Fe(III) from hydrochloric acid, nitric acid, and sulfuric acid was studied as a function of various parameters such as acid concentration, extraction kinetics, concentration of metal in the aqueous phase, amount of resin, resin acid stability after prolonged acid exposure, and influence of interfering ions. The results revealed that resin TK221 showed extremely fast kinetics that fit a pseudo-second order model, along with a high Langmuir adsorption capacity (40 mg.g−1). The high selectivity and enrichment of REE over other metal ions, together with the efficient recovery from real permanent magnet leachate and simulated coal fly ash leachate solution, indicate that TK221 is a promising candidate for the recovery of REE from leachate solutions.

The transition to clean energy, driven by the urgent need to mitigate climate change and achieve carbon neutrality, has become a major driver of high global demand for critical metals and minerals, including lithium, cobalt, copper, graphite, nickel, and rare earth elements (REEs). These minerals are essential for low-carbon technologies, including electric vehicles, advanced batteries, solar photovoltaic systems, grid storage, and wind turbines. However, this transition often involves overlooked environmental, social, and public health impacts associated with the mining, processing, transportation, and end-of-life management of clean energy systems and associated components containing critical metals and minerals. Evidence from diverse research fields and global case studies, including lithium brine extraction, copper and nickel mining, REE processing, and cobalt production, demonstrates that while critical metals/minerals support low-carbon energy, their production frequently creates serious challenges for public health, local livelihoods, and the environment. In many cases, these challenges are transferred from energy consumers in developed countries to vulnerable communities in resource-rich nations. To address these “hidden costs”, this study proposes integrated strategies to mitigate risks and promote sustainable, resilient, and ethical mineral supply chains. Key measures include robust regulatory frameworks and enforcement, cleaner production technologies, circular economy practices, enhanced transparency and traceability, and strengthened policy and multilateral cooperation. The findings revealed that a truly sustainable energy transition requires more than the adoption of low-carbon technologies, since such a transition does not automatically guarantee low-impact production; instead, it must balance mineral development with environmental protection, public health, and socio-economic resilience.

This study investigates the enhanced thermal stability performance of a laboratory-developed intumescent fire-retardant (IFR) coating through the incorporation of mineral-based fillers, namely dolomite (CaMg(CO₃)₂), talc (Mg₃Si₄O₁₀(OH)₂), and chicken eggshell-derived calcium carbonate (CaCO₃), into a conventional ammonium polyphosphate-melamine-expandable graphite (APP-MEL-EG) system. Fire resistance performance was evaluated in accordance with ASTM E119, where the optimized formulation exhibited the lowest back-substrate temperature of 104 °C among seven tested compositions, indicating superior thermal insulation capability. Thermogravimetric analysis (TGA) further confirmed the effectiveness of the composite fillers, demonstrating a significant increase in residual mass of up to 39.3%, indicative of improved thermal stability. Post-fire characterization of the resulting char was conducted to elucidate the underlying stabilization mechanisms. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX) revealed the formation of a dense, homogeneous, and compact char layer, predominantly composed of carbon (C), phosphorus (P), and oxygen (O), which is essential for effective thermal shielding. Complementary analyses using attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) identified the presence of key functional groups and cross-linked structures, including C-N, C-O-H, P-O-P, and C-H bonds. These findings suggest the formation of stable, highly cross-linked aromatic carbon networks, driven by the interaction of free radical species during thermal degradation. The synergistic interaction between the mineral fillers and the APP-MEL-EG matrix significantly enhances char integrity and stability, thereby improving fire resistance and suppressing flame propagation. Finally, this work demonstrates a sustainable and effective approach for enhancing the thermal performance of intumescent coatings through the use of naturally derived and mineral-based additives, offering promising applications for passive fire protection of steel structures.​

The global push towards renewable energy and low-carbon technologies has increased global demand for critical metals, including copper (Cu) and zinc (Zn). High-grade primary resources, however, are becoming scarce; highlighting the need to explore alternative, low-grade secondary resources. Unfortunately, conventional and existing recovery methods of metals from low-grade resources remain prohibitively expensive, thereby offsetting their overall sustainability and economic feasibility. In this study, a novel strategy to repurpose scrap aluminum (Al) filings—an industrial waste excluded in conventional aluminum recycling due to high melt loss—into aluminum-iron (Al-Fe) bimetallic materials for the recovery of Cu and Zn from simulated acid mine drainage (AMD) is investigated. Al-Fe bimetals were synthesized via a modified cementation method using scrap Al as precursor, and characterized using XRF, SEM-EDS, and XPS, confirming successful deposition of zero-valent iron (ZVI) on Al. Batch experiments demonstrated high performance of synthesized Al-Fe bimetals, achieving 100% Cu and 98% Zn recovery from simulated AMD within 20–120 minutes at 10–20 g/L dosage. Furthermore, the Al-Fe bimetal neutralized the solution, raising the pH from 2.1 to 5.7, highlighting its dual role in AMD valorization and treatment. Mechanistic evaluation, supported by SEM-EDS and XPS analyses of reacted bimetals, confirmed that Cu2+ and Zn2+ were recovered via galvanic interactions and direct reduction. For Zn, a secondary recovery mechanism is present—adsorption/co-precipitation onto in-situ formed Al/Fe oxyhydroxides. This work demonstrated a promising waste valoriz ation pathway, transforming scrap Al filings and metal-laden AMD into a valuable resource contributing to circular economy and cleaner production.

Microplastics (MPs) are widespread pollutants in aquatic environments, but their impacts throughout the life cycle remains of organisms are still not well understood. This systematic review integrates recent experimental results on the developmental, physiological, and neurobehavioral effects of MPs exposure on zebrafish (Danio rerio), a popular model organism for ecotoxicology research. A PRISMA-guided search using Web of Science (WoS) and Scopus as databases generated 371 articles, which was screened to 60 eligible articles. The collated results showed that MP toxicity strongly related to concentration, size, and extent of weathering or aging at various life stages of zebrafish. For developmental toxicity, a concentration-dependent yielded peer-reviewed publications assessing specific MPs properties, such as polymer identity, size, concentration, shape, and aging status. At various life stages, the toxicity of MPs was most affected by concentration, size, and aging. The developmental toxicity showed a concentration-dependent decrease in the rate of hatching, growth inhibition, and cardiac dysfunction, while, an increase in malformations, especially at concentrations of ≥100 µg/L or ≥10 mg/L has been reported. Non-monotonic and threshold effects have also been observed, the complexity of particle-based versus mass-based concentrations. Weathered and photo-aged MPs were found to exhibit higher embryotoxicity and neurodevelopmental toxicity, including changes in gene expression of neurons, decreased integrity of motor neurons, and impaired retinal development, compared with virgin MPs. Furthermore, physiological endpoints showed that oxidative imbalance was a key mechanistic process, which included changes in the activity of antioxidant enzymes (SOD, CAT, GPx), lipid peroxidation, inflammation, and disruption of tight junctions. Chronic MP exposures caused changes in the gut microbiota, hepatic metabolism, endocrine disruption, reproductive damage, thyroid function disruption, and genotoxicity in zebrafish. Neurobehavioral alterations, such as changes in locomotor activity, anxiety response, neurotransmitter homeostasis, and acetylcholinesterase function, occurred in both larvae and adults, with a potentiation effect in aged MP exposure. Previous, experimental data have also shown that zebrafish are very sensitive to MPs exposure in various biological systems, with toxicity being a function of physicochemical properties and exposure conditions. Finally, this review found major limitations for inter-study comparisons because of inconsistencies and differences in methodology related to MP concentration, simulation of MP aging, and MP dose measurements.

The exposure of microplastics (MPs) to ultraviolet (UV) light in the environment can affect their flotation behavior and removal efficiency. This study investigated the effects of UVC irradiation on the physical and surface characteristics of polypropylene (PP), polyethylene (PE), acrylonitrile butadiene styrene (ABS), polystyrene (PS), polyethylene terephthalate (PET), and polyvinyl chloride (PVC), and evaluated their removal using agglomeration-micro-flotation. MPs were irradiated with UVC for 7 days, and they were characterized using particle size distribution analysis, CIE L*a*b* color analysis, and contact angle measurements. Flotation experiments were conducted using kerosene as a hydrophobic bridging liquid. The results showed that UVC irradiation induced polymer-dependent changes, including fragmentation, apparent shape-related changes, and redistribution behavior, resulting in changes in particle size distribution. Surface discoloration and reduced contact angle were also observed after UV exposure, suggesting photooxidative surface modification and increased surface hydrophilicity. These surface modifications reduced flotation performance at low kerosene dosages, particularly for PET and PVC. However, increasing kerosene dosage improved removal efficiency by enhancing agglomeration and particle-bubble attachment. The results indicated that agglomeration-micro-flotation is a promising approach for removing UV-aged MPs and provided insights into the influence of UV-induced surface modifications on flotation behavior.

Phosphogypsum (PG), a by-product of phosphate fertilizer production, poses several environmental risks including heavy metal contamination, geotechnical stability of tailing ponds, and radioactivity levels. Only 15% of PG is being utilized for cement and agricultural applications. Current developments have been exploring PG for mineral carbonation (MC). In this study, the calcium extraction process from Philippine PG was established and optimized via salt and acid leaching. Optimal Ca extraction efficiencies of 18.3% (2.5 M NaCl, 38 degrees C, 60 min, and 26 mL/g L/S ratio) and 93.0% (2.3 M HCl, 62 degrees C, 60 min, and 26 mL/g L/S ratio) were obtained for salt and acid leaching, respectively. Life cycle impact assessment of a theoretical MC plant utilizing acid leaching for Ca extraction showed that while constructing an MC plant offsets benefits brought by carbon capture, mineral and resources use, reduced landfill, and process water recirculation can still be achieved. This study proves that local PG can be a potential feedstock for indirect MC with manageable environmental impacts that can be further worked on with green extraction methods and possible resource recovery.

Conservation of architectural heritage structures (AHS) requires compatible built her-itage materials with aesthetic, physical, chemical, and mechanical properties similar to those of the original materials. In recent years, however, urbanization, land reclamation, depletion of stone quarries, anti-mining and anti-quarrying legislation have limited access to original heritage materials. In the absence of the original heritage materials, ce-ment-based alternatives have been developed and widely applied for conservation. Major drawbacks of concrete- and cement-based materials include their large carbon footprint and long-term damage to the original rock or substrate, due to inadvertent promotion of salt efflorescence. This study systematically reviewed geopolymer-based materials as a sustainable, greener alternative to concrete- and cement-based materials for tuff- and coral rock-built heritage structures. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were implemented for the literature review, using Scopus, Web of Science (WoS), and Google Scholar (supplementary) as databases, between 2013 and 2024. Inaccessible items, non-English, reviews, conference proceedings, book chapters, errata, and papers unrelated to geopolymers, tuff, and coral rock were excluded, resulting in a total of 103 articles. These works were classified into geopolymers (34 arti-cles), tuff-built heritage structures (60 articles), and coral rock-built heritage structures (9 articles). This review included 103 items in the qualitative analysis; however, only 34 arti-cles contained meaningful data for content analysis. These 34 articles were categorized in terms of the (i) main precursors; that is, metakaolin, fly ash, slag, and pyroclastic materi-als (i.e., pumice, volcanic ash, and volcanic soil), ceramic, others (i.e., tuff waste, silica fume, and mine wastes), (ii) formulations (i.e., precursors, activators, admixtures, and ag-gregates), and (iii) compressive strength. Furthermore, critical factors for compatibility were reviewed and classified into aesthetics (e.g., color, presence of efflorescence, and tex-ture) and physical, chemical, and mechanical properties. This review also explored recent applications of geopolymers in heritage structures, indicating that geopolymers are typi-cally used as repair mortar and consolidants. Finally, a bibliometric analysis was con-ducted to evaluate research trends on geopolymers, including a critical assessment of their aesthetic compatibility with heritage structures in the Philippines built with volcanic tuff and coral rock.

Acid mine drainage (AMD) is generally managed via active or passive treatment strategies. Between the two, passive treatment is explored as a more sustainable alternative, especially for abandoned and legacy mines due to their low energy, manpower and material requirements. Recent studies of the authors have explored the use of limestone and waste materials like low-grade ores (LGO), fly ash (FA), and concrete wastes (CW) for AMD treatment and found that although these materials generated alkalinity individually, they could only partially remove sulfate (SO4 2-) and some heavy metals. To address this limitation, a mixed media approach using these four materials is proposed to neutralize the pH of AMD and maximize metal and SO4 2- removal. A total of twenty (20) mixtures of the four materials were identified based on the response surface methodology (RSM) experimental design. Laboratory-scale experiments using simulated AMD were performed to assess the performance of each mixture by monitoring the pH, oxidation-reduction potential (Eh), electrical conductivity (EC), and concentrations of metals and SO4 2-. Based on the results, three optimized mixed media compositions were identified. Overall, simulated AMD passively treated by the optimized mixed media compositions met the Philippine effluent standards except for SO4 2-.

Prolonged exposure to teratogens is known to cause neural tube defects (NTDs), a severe malformation of the central nervous system (CNS) that significantly contributes to global infant mortality. In recent years, exposure to nanoplastics (NPs) has been linked to faulty neural crest closure and altered neurulation by altering cellular adhesion molecules and accumulation of plastic particles in the neural tube leading to NTDs. However, research on the influence of various types of microplastics (MPs) on malformations of the CNS are still limited. In this study, we investigated whether MPs of polytetrafluoroethylene (PTFE)da type of plastic commonly used as non-stick coatings of cooking utensils can affect angiogenesis and CNS development using ducks as model organisms. PTFE MPs were administered on Day 3 of duck embryo development at varying concentrations (0.01 mg/ml, 0.1 mg/ml, 1 mg/ml, and 5 mg/ml), and angiogenesis was evaluated using a chorioallantoic membrane (CAM) assay. Gross morphology and histology of the spinal column and brain were analyzed on Days 8 and 18, respectively. FTIR confirmed PTFE's structure, while SEM and DLS analyses showed particle sizes between 300 nm and 5 m m, classifying them as MPs. High concentrations (5 mg/ml) of PTFE MPs treated on duck embryos resulted in a 35% mortality rate and reduced vascular density, suggesting anti-angiogenic effects. Brain and spinal abnormalities, such as encephalomalacia and spinal cord discontinuities were observed in the PTFE-treated embryos. Based on these results, PTFE is an anti-angiogenic and teratogenic agent affecting the development of duck embryos. (c) 2024 The Authors. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

Microplastic (MP) pollution is a global concern due to its persistence, ubiquity, and potential ecological and health risks. Although various MP separation techniques exist, flotation has gained attention as a promising approach adapted from mineral processing. This study provides a systematic review, bibliometric analysis, and meta-analysis of MP removal using flotation, covering 31 papers published between 2015 and 2024. Research output has grown rapidly since 2020, with China (including Hong Kong) as the leading contributor with strong international collaborations. Bibliometric mapping highlighted hotspots such as polymer type, particle size, contact angle, and nanobubbles. Meta-analysis showed that flotation achieved high removal efficiencies across water and solid matrices, though performance varies with polymer properties, surfactants used, and experimental design. Studies focused on solid particles remain limited, reflecting greater methodological challenges than in water systems. Critical discussion emphasized the need for standardized protocols, scaling from laboratory to field applications, and integration with wastewater treatment. This review identified knowledge gaps and emerging trends that can inform the future development of flotation as an effective technology for mitigating MP pollution.

This study investigates the removal of microplastics (MPs) from simulated freshwater, brackish water, and seawater using a novel agglomeration–micro-flotation technique. This method combines particle size enlargement, facilitated by kerosene as a bridging agent, with bubble size reduction through column flotation to enhance the removal rate. Six common MP types—polypropylene (PP), polyethylene (PE), acrylonitrile butadiene styrene (ABS), polystyrene (PS), polyethylene terephthalate (PET), and polyvinyl chloride (PVC)—were evaluated under varying salinity levels and kerosene dosages. Results showed that increasing kerosene dosage significantly improved removal rates, achieving up to ~99% recovery at 10 µL for low- and medium-density MPs (PP, PE, ABS, and PS), while a higher dosage of 30 µL was required for high-density MPs (PET and PVC). Elevated salinity levels (50–100%) promoted bubble stabilization and reduced coalescence, enhancing particle–bubble collisions and the overall flotation performance. This work addresses a key research gap in flotation-based MP removal under saline conditions and highlights the dual benefits of using kerosene—not only to enhance the removal rate but also to enable energy recovery, as both kerosene and plastics are combustible. The proposed technique presents a promising approach for microplastic remediation in aquatic environments, supporting sustainable water treatment and circular resource utilization.

This review explores the integration of Indigenous Knowledge and Skills (IKS) in mining operations, aimed at developing a comprehensive understanding of how these knowledge systems are embedded throughout the mining life cycle. The study systematically reviewed relevant literature from three electronic databases using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Eighteen articles that met the inclusion criteria were included in the final analysis. Key findings reveal that qualitative methods, particularly interviews, are predominantly used to capture Indigenous perspectives. The research is regionally concentrated in Australia, with significant contributions from Canada, Papua New Guinea, and the USA. The studies encompass various Indigenous groups, highlighting varied cultural contexts and knowledge systems. Traditional ecological knowledge, a subset of IKS, is frequently integrated into mine planning and rehabilitation, demonstrating its practical value in sustainable mining practices. Factors facilitating the integration of IKS include supportive policies and laws, community leader involvement, and alignment with community expectations. Our findings contribute to the understanding of IKS in mining operations by providing a detailed overview of IKS integration in the mining life cycle, emphasising the importance of qualitative research, regional and cultural diversity, and their practical benefits.

Coal fly ash (CFA) is a promising secondary resource for rare earth element (REE) recovery. This study characterized CFA using XRF, SEM-EDS, ICP-MS, and XRD, revealing critical REE concentrations of 26.3 ppm (Nd), 4.84 ppm (Dy), 2.89 ppm (Er), 1.69 ppm (Eu), and 0.85 ppm (Tb). REEs are distributed in Al-Si-Mg-Ca-rich aluminosilicates, except Dy, which is associated with Fe-rich phases. Leaching optimization using response surface methodology (RSM) with a central composite design (CCD) identified optimal conditions at 59.5% HCl:40.5% citric acid, 85 °C, and 720 min, achieving recoveries of 94.8% (Dy), 85.2% (Er), 73.1% (Eu), 79.1% (Nd), and 85.7% (Tb). These conditions provided the best balance between recovery, acid use, and selectivity, demonstrating potential scalability for industrial applications. The quadratic model accurately predicted REE recoveries, with accuracies of 95.61% (Dy), 97.76% (Er), 97.30% (Eu), 99.07% (Nd), and 99.17% (Tb). Thermodynamic analysis showed that mineral dissolution influenced REE selectivity, with anorthite (ΔG358K = −348.1 kJ·mol−1) dissolving readily, while ankerite (ΔG358K = 5.49 × 106 kJ·mol−1) contributed to high selectivity, particularly for Mg. Element selectivity followed Mg > Al > Si > Fe ≥ Ca, indicating Mg- and Al-bearing phases were more susceptible, while Fe- and Ca-bearing minerals remained more resistant under mixed-acid conditions.

This study utilized grab and strip testing methods to examine the relationship between three weave structures—plain, twill, and satin—and their tensile strengths in both warp and weft directions. In addition, microplastic fiber (MPF) emissions from these three weave structures were quantified at different states of the laundry process using filtration and microscopy. The grab and strip tests revealed that twill- and satin-woven fabrics exhibited higher tensile strengths in the warp direction compared to the weft orientation. In contrast, the plain weave structure showed similar tensile strengths in both warp and weft directions. During laundry in the washing machine, MPF emissions in the first drainage were the highest regardless of the weave structure. Moreover, the satin weave pattern released the most MPFs among the three common weave structures at 5054 particles/L. This weave pattern also had the weakest tensile strength of 3.1 N/cm2 in the weft direction of the three weave structures evaluated. The results demonstrated a strong inverse correlation between higher tensile strengths in the weaker direction (warp or weft) and MPF emissions. Among the weave structures investigated, the twill pattern had the lowest MPF emission, followed by plain weave, with the satin-woven fabric emitting the highest levels.

Bimetals—materials composed of two metal components with dissimilar standard reduction–oxidation (redox) potentials—offer unique electronic, optical, and catalytic properties, surpassing monometallic systems. These materials exhibit not only the combined attributes of their constituent metals but also new and novel properties arising from their synergy. Although many reviews have explored the synthesis, properties, and applications of bimetallic systems, none have focused exclusively on iron (Fe)- and aluminum (Al)-based bimetals. This systematic review addresses this gap by providing a comprehensive overview of conventional and emerging techniques for Fe-based and Al-based bimetal synthesis. Specifically, this work systematically reviewed recent studies from 2014 to 2023 using the Scopus, Web of Science (WoS), and Google Scholar databases, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, and was registered under INPLASY with the registration number INPLASY202540026. Articles were excluded if they were inaccessible, non-English, review articles, conference papers, book chapters, or not directly related to the synthesis of Fe- or Al-based bimetals. Additionally, a bibliometric analysis was performed to evaluate the research trends on the synthesis of Fe-based and Al-based bimetals. Based on the 122 articles analyzed, Fe-based and Al-based bimetal synthesis methods were classified into three types: (i) physical, (ii) chemical, and (iii) biological techniques. Physical methods include mechanical alloying, radiolysis, sonochemical methods, the electrical explosion of metal wires, and magnetic field-assisted laser ablation in liquid (MF-LAL). In comparison, chemical protocols covered reduction, dealloying, supported particle methods, thermogravimetric methods, seed-mediated growth, galvanic replacement, and electrochemical synthesis. Meanwhile, biological techniques utilized plant extracts, chitosan, alginate, and cellulose-based materials as reducing agents and stabilizers during bimetal synthesis. Research works on the synthesis of Fe-based and Al-based bimetals initially declined but increased in 2018, followed by a stable trend, with 50% of the total studies conducted in the last five years. China led in the number of publications (62.3%), followed by Russia, Australia, and India, while Saudi Arabia had the highest number of citations per document (95). RSC Advances was the most active journal, publishing eight papers from 2014 to 2023, while Applied Catalysis B: Environmental had the highest number of citations per document at 203. Among the three synthesis methods, chemical techniques dominated, particularly supported particles, galvanic replacement, and chemical reduction, while biological and physical methods have started gaining interest. Iron–copper (Fe/Cu), iron–aluminum (Fe/Al), and iron–nickel (Fe/Ni) were the most commonly synthesized bimetals in the last 10 years. Finally, this work was funded by DOST-PCIEERD and DOST-ERDT.