Efficient Recycling Research Articles

Current State of Chemical Recycling of Plastic Waste: A Focus on the Italian Experience

With a value of 400.3 Mt, the global plastics production increased in 2022 with a plus of 2.5 wt% compared to the previous years. Unfortunately, plastic waste is often disposed of inappropriately, causing environmental problems and an avoidable waste of resources. In 2019, the European Circular Economy Action Plan was issued to encourage plastic recycling. Nevertheless, at the end of 2022, post-consumer mechanically recycled plastics in Europe accounted only for 13.2 wt% of the European plastic production (58.8 Mt). Mechanical recycling fails to recycle mixed, partially degraded, or contaminated plastic waste. Then, there is an acute demand for new, efficient, and cost-effective recycling technologies to fill the gap left by mechanical recycling. Chemical recycling is considered a complementary alternative because it can process waste streams composed of heterogenous and difficult plastics. Currently in Europe, around 58.8 kt (0.1 wt%) of plastic production was obtained by chemically recycled plastics, but the road is marked. The Plastic Europe association announces that its members are going to produce 2.8 Mt of chemically recycled plastics by 2030. Mixed plastic waste is the main target, and pyrolysis and gasification, identified as the suitable technologies for its treatment, represent 80 wt% of the planned capacities.

Analyzing Organic Electrolyte Solvents from Spent Lithium-Ion Batteries as a Basis for Distillative Value Component Recovery

The rapid expansion of lithium-ion batteries (LIBs), largely driven by the rising demand for electric vehicles, will lead to a significant increase in end-of-life (EOL) batteries, necessitating efficient recycling processes, which must be accompanied by equally efficient purification steps. This study addresses the challenge of reusing organic electrolyte solvents from spent LIBs, a key component often overlooked in existing recycling strategies. To address this issue, we developed a gas chromatography (GC) method. A variety of spent electrolyte samples of different origin, including mechanical-thermal pretreatment or direct cell recovery, were analyzed by quantification of common solvents and identified organic impurities. Results demonstrated that the composition of the recovered electrolytes was highly variable, with concentrations fluctuating. Impurities were identified, which may originate from various sources throughout the lifespan of an LIB and have the potential to reduce the performance of second-life LIBs by reusing the electrolyte without any purification. The findings highlight the necessity for advanced purification methods like a distillation process to remove these impurities and ensure the viability of recycled electrolytes in maintaining the performance and safety standards required for LIBs. This research contributes to the broader goal of enhancing the sustainability and reuse of battery materials.

Development of Multipurpose Supported Asymmetric Salen Catalysts by Cu(0)‐Mediated Reversible Deactivation Radical Copolymerization

Designing heterogeneous catalysts that ensure efficient recycling and reuse of the catalyst in a wide range of transformations remains a real challenge. In this contribution, targeted copolymers are used as supports for the development of heterogeneous asymmetric catalysts. They are made up of two methacrylate monomers, 3‐azidopropylmethacrylate (AZMA), and 2‐methoxyethyl methacrylate (MEMA) used as a diluting agent. Polymerization was carried out using Cu(0)‐mediated reversible deactivation radical polymerization (RDRP), yielding two copolymers with controlled MEMA/AZMA compositions of 70/30 and 30/70 with moderate dispersity control (Ð = 1.32‐1.54), targeting polymers with a similar molar mass, which is important to achieve precise control of the catalyst loading to implement asymmetric catalysis. The copolymers were post‐functionalized using click chemistry with two salen complexes containing a chromium or a cobalt center, these species being recognized for their broad range of applications. The supported catalysts were evaluated in two reactions and recovered by precipitation and filtration techniques. The first reaction involved the asymmetric ring opening (ARO) of cyclohexene oxide with trimethylsilylazide, catalyzed by the chromium sites, the second reaction was the dynamic kinetic resolution (DKR) of epibromohydrin with water, promoted by the cobalt sites. The recycling was effective, demonstrating the robustness and viability of the procedure.

Carbon Emission Assessment During the Recycling Phase of Building Meltable Materials from Construction and Demolition Waste: A Case Study in China

The improper disposal of construction and demolition waste (CDW) exacerbates the consumption of raw materials and emissions of greenhouse gasses. In this study, due to the high recycling rate, focusing on the meltable materials of CDW, the recycling phase of CDW is divided into four stages, namely the on-site disposal stage, the transportation stage, the reprocessing stage, and the reproduction stage. Second, based on these four stages, a carbon emission accounting model (CEAM) is established to evaluate the carbon emission benefits of meltable materials during these stages. Third, the CEAM is applied to a typical old residential area to evaluate the carbon emission reduction benefits of the CDW recycling. The results indicate that (1) the full-process carbon emissions of recycled steel, recycled flat glass, and recycled aluminum per unit mass are 677.77 kg/t, 1041.54 kg/t, and 845.39 kg/t, respectively, which are far lower than their corresponding ordinary meltable building materials (OMBMs); (2) the carbon emissions during the reproduction stage represent the primary component of carbon emissions in the MW recycling phase, accounting for 88.52% to 97.45% of the total carbon emissions; and (3) the carbon emissions generated by the recycling of cullet per unit mass are very high, reaching 1768 kg/t, which is 4.3 times that of scrap steel (409.05 kg/t) and 3.6 times that of scrap aluminum (483.76 kg/t). The research findings could provide theoretical methods and experimental data for decision-makers to formulate treatment plans for meltable materials in CDW, thereby empowering urban carbon emission reduction and promoting sustainable development. Construction parties engaged in demolition tasks should enhance on-site sorting and collaborate with recycling companies to ensure its efficient recycling. Recycling companies need to focus on high-carbon-emission stages, such as the reproduction stage, and strengthen technological research to improve carbon reduction benefits.

Magnetically recyclable CoFe2O4 nanocatalysts for efficient glycolysis of polyethylene terephthalate

Efficient and sustainable recycling of polyethylene terephthalate (PET) is essential in mitigating its environmental impacts on climate, human health, and global ecosystems. Glycolysis, a closed-loop recycling method that converts PET into bis(2-hydroxyethyl) terephthalate (BHET), stands out as one of the most promising methods due to its mild operating conditions and environmentally friendly nature. However, the complete convert PET into BHET with a high stability are still challenging. In this study, magnetically recyclable CoFe2O4 nanocatalysts were synthesized by the solvothermal method and surface-modulated with Na3Cit·2H2O as a modifier. When utilizing an optimized CoFe2O4 catalyst, conversion of PET achieved 100 %, with a BHET yield of 91.7 % at 210 °C for 1 h. The excellent catalytic performance of CoFe2O4 is attributed to its smaller particle size, improved dispersion, higher surface Co/Fe ratio, and increased oxygen vacancies, all of which can be achieved through straightforward surface modulation. DFT calculations of M−O distance (M = Co or Fe), adsorption energy, and Bader charges confirm that a higher surface Co/Fe ratio enhanced PET glycolysis, consistent with experimental results. Additionally, a modified energy economy coefficient (εm) was proposed to characterize the catalytic efficiency. The εm value of CoFe2O4-60 % was 0.624, indicating promising applications in efficient PET glycolysis. This work presents a versatile approach for easily manipulating the surface properties of magnetic catalysts and identifies key factors for achieving high performance in PET-to-BHET conversion. It offers valuable guidelines for the future design of nanoparticle catalysts with magnetic properties for chemocatalytic reactions.

An automated waste classification system using deep learning techniques: Toward efficient waste recycling and environmental sustainability

An automated waste classification system using deep learning techniques: Toward efficient waste recycling and environmental sustainability

Assessment of the Applicability of Waste Concrete Fine Powder as a Raw Material for Cement Clinker

The cement industry is responsible for a significant portion of global CO2 emissions, primarily due to the decarbonatization of limestone during clinker production. To mitigate this environmental impact, this study investigated the feasibility of using waste concrete fine powder, produced during the recycling of waste concrete, as a decarbonized raw material in cement clinker production. As a decarbonized material, waste concrete fine powder presents a valuable opportunity to reduce CO2 emissions typically produced during the decarbonatization of limestone in clinker production. In addition, its use supports the recycling of construction waste, contributing to both emissions reduction and resource sustainability. In this study, samples were collected from 20 intermediate treatment plants in South Korea, where the chemical composition, particle size distribution, and carbonation rate of the fine powders were analyzed. The experimental results show that the properties of waste concrete fine powder vary significantly depending on the recycling process. Road construction aggregate production plants, which typically involve two to three crushing stages, produce fine powders with higher CaO content (28–31%) and consistent particle size distributions. In contrast, plants producing aggregates for concrete, which involve four to six crushing stages, produce powders with lower CaO content (around 20%) and greater variability in particle size. The average carbonation rate of 7.44% suggests that these fine powders can replace limestone in clinker production. It is estimated that substituting 5% of limestone with waste concrete fine powder could reduce CO2 emissions from limestone decarbonatization by approximately 952,560 tons in 2023, representing a 3.34% decrease in total emissions from clinker production. However, it is important to note that the CO2 emissions reduction calculation is not from a lifecycle perspective, without considering the energy-related emissions from recycling waste concrete fine powder. Nevertheless, this study highlights the potential for waste concrete fine powder to serve as a sustainable raw material for the cement industry, contributing to both CO2 reduction and efficient recycling of construction waste.

Tolerance mechanisms in polysaccharide biosynthesis: Implications for undecaprenol phosphate recycling in Escherichia coli and Shigella flexneri.

Bacterial polysaccharide synthesis is catalysed on the universal lipid carrier, undecaprenol phosphate (UndP). The cellular UndP pool is shared by different polysaccharide synthesis pathways including peptidoglycan biogenesis. Disruptions in cytosolic polysaccharide synthesis steps are detrimental to bacterial survival due to effects on UndP recycling. In contrast, bacteria can survive disruptions in the periplasmic steps, suggesting a tolerance mechanism to mitigate UndP sequestration. Here we investigated tolerance mechanisms to disruptions of polymerases that are involved in UndP-releasing steps in two related polysaccharide synthesis pathways: that for enterobacterial common antigen (ECA) and that for O antigen (OAg), in Escherichia coli and Shigella flexneri. Our study reveals that polysaccharide polymerisation is crucial for efficient UndP recycling. In E. coli K-12, cell survival upon disruptions in OAg polymerase is dependent on a functional ECA synthesis pathway and vice versa. This is because disruptions in OAg synthesis lead to the redirection of the shared lipid-linked sugar substrate UndPP-GlcNAc towards increased ECA production. Conversely, in S. flexneri, the OAg polymerase is essential due to its limited ECA production, which inadequately redirects UndP flow to support cell survival. We propose a model whereby sharing the initial sugar intermediate UndPP-GlcNAc between the ECA and OAg synthesis pathways allows UndP to be redirected towards ECA production, mitigating sequestration issues caused by disruptions in the OAg pathway. These findings suggest an evolutionary buffering mechanism that enhances bacterial survival when UndP sequestration occurs due to stalled polysaccharide biosynthesis, which may allow polysaccharide diversity in the species to increase over time.

Optimising resource recovery from construction waste material reverse supply chain coordination games

The inefficiency of government, recycling, and recovery companies in managing construction waste, especially after an earthquake, highlights the operational challenges of reverse supply chain (RSC) in effectively recycling materials. This study aims to address these inefficiencies by proposing a decision-making supply chain model that enhances coordination within the RSC, and focusing on optimising the management of post-disaster construction waste. Grounded in market demand functions, the model explores three subsidy models to examine their impact on recycling efficiency, the recycling ratio, retail pricing of materials from recycled waste, and overall profit. The study uses manufacturing enterprises-leadership and subsidy-specific Stackelberg game models to find optimal strategies for minimising waste and maximising supply chain profit. The results show that government subsidies significantly influence recycling and pricing strategies within RSC operations, and governments should offer subsidies according to waste dispersion prioritisation and quantity of recoverable construction debris. Based on the study findings, the proposed RSC model substantially enhances recycling efficiency and profitability for both recycling and manufacturing firms. These findings validate the effectiveness of the model and emphasise the prospects for future research on an RSC framework for construction waste material.

Unraveling the influence of microbial Necromass on subsurface microbiomes: metabolite utilization and community dynamics

Abstract The role of microbial necromass (nonliving microbial biomass), a significant component of belowground organic carbon, in nutrient cycling and its impact on the dynamics of microbial communities in subsurface systems remains poorly understood. It is currently unclear whether necromass metabolites from various microbes are different, whether certain groups of metabolites are preferentially utilized over others, or whether different microbial species respond to various necromass metabolites. In this study, we aimed to fill these knowledge gaps by designing enrichments with necromass as the sole nutrient source for subsurface microbial communities. We used the soluble fraction of necromass from bacterial isolates belonging to Arthrobacter, Agrobacterium, and Pseudomonas genera, and our results indicate that metabolite composition of necromass varied slightly across different strains but generally included amino acids, organic acids, and nucleic acid constituents. Arthrobacter-derived necromass appeared more recalcitrant. Necromass metabolites enriched diverse microbial genera, particularly Massilia sp. responded quickly regardless of the necromass source. Despite differences in necromass utilization, microbial community composition converged rapidly over time across the three different necromass amendments. Uracil, xanthine, valine, and phosphate-containing isomers were generally depleted over time, indicating microbial assimilation for maintenance and growth. However, numerous easily assimilable metabolites were not significantly depleted, suggesting efficient necromass recycling and the potential for necromass stabilization in systems. This study highlights the dynamic interactions between microbial necromass metabolites and subsurface microbial communities, revealing both selective utilization and rapid community and necromass convergence regardless of the necromass source.

Circular Economy for Construction and Demolition Waste in the Santiago Metropolitan Region of Chile: A Delphi Analysis

This study investigates the design and implementation of circular economy (CE) strategies for managing construction and demolition waste (CDW) in the Santiago Metropolitan Region of Chile (SMRC). The research aimed to identify key factors influencing the current and future adoption of CE practices for CDW management related to socio-environmental, technical, financial, and strategic-regulatory aspects, employing the Delphi method to gather expert insights. Findings reveal that the lack of knowledge about sustainable practices and the absence of regulatory frameworks for CDW disposal are the most critical barriers to effective CE implementation. The study recommends enhancing public awareness and environmental education through government and school programs, as well as enacting stricter legislation to combat illegal disposal and encourage sustainable practices and valorization of secondary raw materials within companies. Additionally, it emphasizes the importance of designing projects that prioritize waste avoidance and the development of infrastructure, technology, and processes for efficient material separation and recycling. The research also highlights potential challenges such as stagnation in the adoption of sustainable practices, skilled labor shortages, and limited research and innovation. It underscores the need for a comprehensive approach to CDW management that integrates socio-environmental, technical, financial, and regulatory dimensions to promote sustainability at both regional and global levels.

Solventless Dual-Cure Liquid Resins Via Circular Use of Phthalic Anhydride for Recyclable Composite Applications.

Fiber-reinforced composites (FRCs) possess a remarkable strength-to-weight ratio, making them ideal light-weighing alternative materials of metals used in automotive, aerospace, and outdoor equipment applications, but their recycling is challenging. Chemically recyclable thermoset polymers can enable fiber recovery and reuse; however, challenges remain in the separation and purification of depolymerized small molecules for efficient polymer recycling. To this end, a series of liquid resins for chemically recyclable polymer networks is designed based on phthalic anhydride, a widely produced and inexpensive chemical. The straightforward sublimation of phthalic anhydride is leveraged to enable a simple and efficient separation process for polymer recycling. To liquefy phthalic anhydride, five mono-acryloyl-phthalates are synthesized to obtain stable liquid resins together with phthalic diglycidyl ester. These liquid resins undergo dual-cure reactions that comprise photopolymerization of acrylate and, subsequently, heat-mediated epoxy-acid polymerization reactions. These liquid resins exhibit moderate viscosities (2600-6400 cP @ 22 °C), fast curing, and robust thermomechanical properties (Tgs from 71 to 116 °C). It is demonstrated that hydrolysis of the dual-cured polymers completes within 2 h at 80 °C, and direct sublimation produces phthalic anhydride with 82% yield. This resin system is expected to provide a cost-competitive, highly efficient platform for recyclable FRCs.

Collaborative performance of enzymatic saccharification and organic pollutant degradation from PHP (phosphoric acid coupled with hydrogen peroxide) pretreatment of lignocellulose.

As a newly developed technology, lignocellulose pretreatment of PHP (phosphoric acid coupled with hydrogen peroxide) can facilitate the enzymatic hydrolysis of pretreated lignocellulose for glucose production. It also has been found that the derived oxidative tail gas from pretreatment can facilely degrade organic pollutant. To balance the pollutant degradation and the glucose yield, the collaborative optimization on pretreatment was investigated. Results indicated that temperature, H3PO4 and H2O2 concentration were positively correlated with the model pollutant degradation (methylene blue) and enzymatic hydrolysis. Under the optimized conditions of temperature (55°C), H3PO4 concentration (65%), and H2O2 concentration (7%), three typical agricultural residues, including wheat straw, Jerusalem artichoke stalks and corn stover, achieved 95.2%, 94.0% and 98.3% methylene blue degradation, and the corresponding cellulose-glucose conversion was 100%, 97.6% and 100.0%, respectively. While two typical woody residues of oak and birch sawdust achieved methylene blue degradation of 70.2% and 68.0%, and the corresponding cellulose-glucose conversion reached 88.3% and 84.0%, respectively. 90.2-93.6% H3PO4 could be recovered with a stable performance of methylene blue degradation of 98.8-99.7% and cellulose-glucose conversion of 96.1-99.8% in the 5 recycling batches. Overall, this work achieved the "win-win" function on pollutant removal and glucose production, and efficient solvent recycling, which further improved the applicability of PHP pretreatment.

Unraveling Redox Mediator-Assisted Chemical Relithiation Mechanism for Direct Recycling of Spent Ni-Rich Layered Cathode Materials.

The increasing demand for Li-ion batteries across various energy storage applications underscores the urgent need for environmentally friendly and efficient direct recycling strategies to address the issue of substantial cathode waste. Diverse reducing agents for Li supplements, such as quinone molecules, have been considered to homogenize the Li distribution in the cathode materials obtained after cycling; however, the detailed reaction mechanism is still unknown. Herein, the ideal electrochemical potential factor and reaction mechanism of the redox mediator 3,5-di-tert-butyl-o-benzoquinone (DTBQ) for the chemical relithiation of high-Ni-layered cathodes are elucidated. Here, 100% efficiency of DTBQ-assisted chemical relithiation is achieved by adjusting the direct immersion time of Li-deficient cathode electrodes. The reversible reaction features of the physical and chemical structures of both the regenerated cathodes and the DTBQ molecules are investigated using advanced characterization and density functional theory calculations. These findings emphasize the potential of redox-mediator-assisted chemical relithiation for realizing direct recycling processes and offer a facile and sustainable solution for battery recycling.

Environmentally Friendly and Simple Recycling of Titanium Alloy Scrap via Deoxygenation with Hybrid Hydrogen Plasma Arc.

The potential of hydrogen plasma arc technology for the efficient deoxygenation and recycling of titanium alloy scrap is explored. The results of thermodynamic analysis reveal that hydrogen plasma is suitable for oxygen removal. The intermediate stages of the deoxygenation process are sequentially analyzed, showing that the hydrogen plasma arc primarily facilitated the reduction and dissolution of oxides as well as eliminated interstitial oxygen. The experimental results demonstrate that the deoxygenation dynamics are governed by the interaction between the hydrogen partial pressure and the surface area of the hydrogen plasma arc irradiation range. Furthermore, the results of the detailed characterization of the recycled titanium alloys indicate that hydrogen plasma arc technology not only reduces the oxygen content to levels compliant with industrial standards for Ti-6Al-4V but also substantially enhances the tensile strength and ductility of Ti-6Al-4V compared with those of conventional cast titanium alloys. The results of microstructural analysis show that hydrogen tends to concentrate in the β phase, whereas oxygen is predominantly found in the α phase. These findings highlight the effectiveness of hydrogen plasma arc technology, which offers environmental benefits and improves the performance of the resulting material, indicating its promise as a solution for titanium recycling.

New opportunities for biologically and chemically mediated adsorption and precipitation of phosphorus from wastewater.

Biologically mediated adsorption and precipitation of phosphorus (P) from waste streams can restrict environmental P discharges. Here, we appraise progress in this field over the past decade. The research discipline has grown considerably in recent years. Industry 'wastes', including steel slags, continue to show promise as adsorbents with exceptionally high P retention capacities (>500mgPg-1). Hydrotalcite, a nanomineral, offers prospects as a P removal technology with imbedded climate change mitigation capacity. Biomineral struvite formation, driven by microbial processes, offers an exciting P removal and recovery approach that can be applied to diverse wastewater types due to its feedstock-independent mechanisms, emerging immobilisation techniques and adaptability to mixed cultures. All of these factors facilitate efficient nutrient recycling and scalable application to the wastewater industry. Adsorbed and precipitated P can be applied to cropland to offset dependence on conventional fertiliser inputs. Therefore, in addition to water treatment, these biologically mediated processes also offer opportunities to support food production. Moreover, as many of the input materials covered in this review are industry byproducts and common organic materials, the removal of P from waste streams by adsorption and precipitation offers strong circularity potential that aligns with the UN's Sustainable Development Goals. We call for future work to focus on long-term full-scale trials involving community, government and industry partners.

Lithium recovery from mixed spent LFP-NMC batteries through atmospheric water leaching

Selective lithium recovery from a mixture of LFP-NMC spent lithium batteries presents significant challenges due to differing structures and elemental compositions of the batteries. These differences necessitate a distinct recycling pathway for each, complicating the process for the mixture. This study explored a carbothermal reduction approach combined with water leaching under atmospheric conditions to achieve a selective lithium recovery. For individual NMC black mass, at the optimal carbothermal conditions (950 °C, 15 °C/min, 2 h), lithium recovery of 95.7 ± 0.31% with 100% selectivity could be achieved. However, when the black mass was mixed with that of LFP in a 50:50 ratio, the recovery dropped to 9.78 ± 0.44%. Solid-state reactions during carbothermal process resulted in the formation of highly insoluble Li3PO4, and Fe-Ni-Co/Ni-Co alloys, which hinder lithium dissolution. To address these challenges, Na2CO3 was introduced as an additive to suppress Li3PO4. The addition of Na2CO3 to the 50:50 ratio of LFP-NMC black mass, increased lithium recovery to 59.47% with 100% selectivity. This enhancement was due to the stabilization of lithium as Li2CO3, a water-soluble compound. The results demonstrated that addition of Na2CO3 is a promising strategy for improving lithium recovery from mixed LFP-NMC batteries, providing a potential pathway for a more efficient recycling process.

Fabrication of High-Strength Waste-Wind-Turbine-Blade-Powder-Reinforced Polypropylene Composite via Solid-State Stretching

In recent years, wind energy has emerged as one of the fastest-growing green technologies globally, with projections indicating that decommissioned wind turbine blades (WTBs) will accumulate to millions of tons by the 2030s. Due to their thermosetting nature and high glass/carbon fiber content, the efficient recycling of WTBs remains a challenge. In this study, we utilized solid-state shear milling (S3M) to produce a fine WTB powder, which then underwent surface modification with a silane coupling agent (KH550), and we subsequently fabricated WTB-reinforced polypropylene (PP) composites with enhanced mechanical performance through solid-state stretching. The stretching-process-induced orientation of the PP molecular chains and glass fibers led to orientation-induced crystallization of PP and significant improvements in the mechanical properties of the PP/WTB@550 composites. With 30 wt. % WTB content, the PP/WTB@550 composite achieved a tensile strength of 142.61 MPa and a Young’s modulus of 3991.19 MPa at a solid-state stretching temperature of 110 °C and a stretching ratio of 3, representing increases of 268% and 471%, respectively, compared to the unstretched sample. This work offers both theoretical insights and experimental evidence supporting the high-value recycling and reuse of WTBs through a cost-effective, environmentally friendly, and scalable approach. Due to the enhanced mechanical properties of the PP/WTB composite and the intrinsic waterproofing and corrosion resistance of PP, it is hoped that such a composite would be used in road engineering and building materials, such as geogrids, wall panels, floor boards, and floor tiles.

Enhanced FeIV═O Generation via Peroxymonosulfate Activation by an Edge-Site Engineered Single-Atom Iron Catalyst.

As an oxidant, the ferryl-oxo complex (FeIV═O) offers excellent reactivity and selectivity for degrading recalcitrant organic contaminants. However, enhancing FeIV═O generation on heterogeneous surfaces remains challenging because the underlying formation mechanism is poorly understood. This study introduces edge defects onto a single-atom Fe catalyst (FeNC-edge) to promote FeIV═O generation via peroxymonosulfate (PMS) activation. In the presence of PMS, the FeNC-edge catalyst at a low dose (20 mg L-1, equivalent to 0.14 mg L-1 Fe) exhibits unprecedented activity for organic contaminant degradation. Electrochemical analysis, in situ Raman spectroscopy, and FeIV═O probe experiments confirm that FeIV═O generation is enhanced on the surface of FeNC-edge. Density functional theory calculations reveal that the introduced edge sites concentrate electron density on active Fe atoms, facilitating charge transfer from Fe to PMS. Notably, FeNC-edge immobilized on a polymeric membrane functioned as a continuous-flow oxidation system with efficient catalyst recycling and minimal Fe leaching.

Study on the preparation of calcium modified coal gangue and its adsorption performance of phosphate

The adsorption of phosphate in the collected water is crucial to alleviate the crisis of phosphorus resources, which is in line with the concept of green and sustainable development of resources. In this study, based on the calcium modification technology of pyrolysis combined with chemical modification, a new type of calcium modified coal gangue (CaMCG) was prepared by using coal gangue as raw material and calcium chloride as modifier for the removal of phosphate.The optimum preparation conditions of CaMCG were obtained by response surface test: mcalcium chloride:mcoal gangue=1, calcination temperature 735℃, calcination time 135 min. Batch adsorption experiments showed that when the phosphate concentration was 100 mg/L, the optimal CaMCG dosage was 0.5 g and the optimal reaction time was 48 h. At pH 3–7, the adsorption capacity of CaMCG for phosphate was always good. The order of the strength of coexisting anions affecting the adsorption of phosphate by CaMCG was: CO32− > SO42− > HCO3− > NO3− ≈ Cl−. Kinetic isotherm analysis showed that the adsorption of phosphate by CaMCG had both physical adsorption and chemical adsorption. The theoretical maximum adsorption capacity of CaMCG for phosphate was 17.85 mg/g. The adsorption process of CaMCG on phosphate conformed to the Langmuir model. The main mechanisms of CaMCG adsorbing phosphate are electrostatic interaction, surface precipitation, adsorption exchange and complexation. This study shows that CaMCG has great potential in adsorbing phosphate, which can provide technical reference for the efficient utilization of coal gangue and the treatment of phosphate wastewater.The phosphate adsorbed by CaMCG can be recycled and reused to achieve efficient and sustainable recycling of phosphorus resources.