ABSTRACT Sodium‐ion batteries (SIBs) are attracting increasing attention as a sustainable and low‐cost alternative to lithium‐ion batteries (LIBs). However, SIBs recycling presents distinct technical, environmental, and economic challenges because of the lower economic value of sodium compounds and the variety of electrode chemistries compared to LIBs. This perspective paper discusses key material systems and degradation mechanisms relevant to SIBs performance, identifies the major technical, environmental, and economic constraints on recycling, and proposes a chemistry‐specific framework for evaluating pretreatment, pyrometallurgy, hydrometallurgy, and direct regeneration routes. Finally, this perspective highlights future directions where degradation‐guided recycling and recycling‐informed battery design can work together to support a closed‐loop SIB ecosystem.
ABSTRACT Ultrafine particles (UFPs), particularly black carbon (BC), are major contributors to air pollution, climate change, and health risks. Conventional quantification techniques such as Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Raman Spectroscopy, while effective, suffer from limitations in real‐time analysis, sample representativeness, and scalability. Lock‐in thermography (LIT) has emerged as a promising alternative, offering enhanced sensitivity and real‐time monitoring for nanoparticle detection. In this study, we employ LIT to quantify black carbon. Two measurement configurations—transmission and reflection mode—are utilized to assess spatial distribution and concentration dependence of BC particles collected on filter substrates. Our results demonstrate a strong correlation between measured thermal signals and reference concentrations, confirming LIT's precision in quantifying BC with high reproducibility. The imaging capability further reveals non‐homogeneous particle deposition patterns, which would be challenging to capture using conventional point‐based techniques. These findings establish LIT as a viable tool for real‐time BC quantification in environmental monitoring and industrial applications, overcoming the constraints of traditional measurement approaches.
ABSTRACT The elevated expenses and utilization of hazardous chemicals in traditional chemical synthesis of anode materials of Li‐ion batteries (LIBs) demand more environmentally friendly and economical approaches for a sustainable energy transition. Herein, a very cheap and facile fabrication approach has been conducted to fabricate anode materials from basic steel slag. Characterization techniques confirmed that the slags were composed of numerous major and minor transition metal oxides' (TMOs) nanosheets with an average thickness of 30.76 nm. The fabricated steel slag electrodes displayed the first cycle charge‐discharge capacities of 161.42 mAh g −1 and 127.34 mAh g −1 at a current density of 20 mA g −1 with Columbic efficiency (CE) of 78.89%. The electrode portrayed improved discharge capacity after 150 cycles and maintained a consistent capacity even after 500 cycles. It exhibited average rate capacities of 115.18, 64.17, 35.86, and 35.42 mAh g −1 at current densities of 20, 40, 80, and 200 mAg −1 , respectively. Detailed electrochemical investigations indicate cell degradation upon cycling.
ABSTRACT Globally accelerating the requirement for ecologically sound and economically efficient energy storage prompted interest in battery technologies. Since the origin, lithium‐ion batteries (LIB) dominated with high energy density and mature infrastructure; however, given the scarcity of lithium resources and rising cost, there has been a driving force to explore alternatives like sodium‐ion battery and potassium‐ion battery technologies. Among these, KIBs offer high power density, favorable K + ion diffusion kinetics, wider range of voltage at higher potential, eliminates the formation of intermetallic compounds, is abundant and also cost‐effective, unlike LIBs. KIBs can use industrial standard graphite as anode unlike NIBs but both behave similarly during ion‐solvent co‐intercalation. Eventually reached with versatile electrode, graphite, as anode exhibits reversible potassium intercalation and charge storage mechanism with structural constraints of larger potassium‐ions and lacks stability. Herein, we introduced graphite anodes recycled from spent LIBs, regenerated as anodes for KIBs‐propounding a circular economy. The optimized sample tested with an ether‐based electrolyte exhibited 107 mAh/g capacity at 5 A/g and was stable for 1000 cycles at room temperature. This sustainable material suitably tailored, exhibits good electrochemical performance at both room and low temperatures. Also, the kinetics of co‐intercalation mechanism was investigated using electrochemical impedance spectroscopy, ex situ x‐ray diffraction and transmission electron microscopy. To a greater extent, the work highlights the positive outcomes of usage of spent graphite in advanced resource‐efficient energy storage solutions. This idea keeps away resource exploitation, environmental contaminations and economic imbalances, reinforcing a sustainable circular economy.
ABSTRACT Metal‐organic frameworks (MOFs) are promising oxygen evolution reaction (OER) electrocatalysts, yet their commercial viability is impeded by poor conductivity and stability under alkaline conditions. Herein, a stable CoFe‐MOF composite was synthesized via a post‐synthetic bimetallic assembly strategy, creating uniform Co–Fe coordination sites within a Co‐MOF‐derived framework. The resulting CoFe‐MOF composite possesses hierarchically porous two‐dimensional (2D) nanosheet structure. The composite delivers remarkably enhanced OER performance, achieving a low overpotential of 290 mV at 10 mA cm −2 and a minimal Tafel slope of 31.88 mV dec −1 , significantly outperforming pristine Co‐MOFs and Fe‐MOFs. Systematic density functional theory (DFT) calculations provide profound theoretical support, revealing that the Fe active site (CoFe‐Fe) exhibits an optimal theoretical reaction barrier (Δ G max ) of only 1.67 eV for the rate‐determining step, which is 0.43 eV lower than that of Co‐MOFs (2.1 eV). This superior intrinsic activity can be attributed to the Co–Fe synergistic electronic effect (Fe→O→Co charge transfer), which effectively optimizes intermediate adsorption and enhances metallic character. Moreover, the nanosheet‐stacked structure ensures excellent long‐term operational stability (over 35 h), effectively mitigating structural collapse in strong alkaline electrolytes. This work demonstrates an effective structural regulation and performance enhancement strategy for designing highly stable MOF‐based water‐splitting electrocatalysts.
ABSTRACT Converting waste biomass into functional biochar offers a promising approach to carbon sequestration, but a sustainable manufacturing method is yet to be developed. The current work demonstrates the proof of concept of biochar production using concentrated seawater, a by‐product from seawater desalination, as the templating agent. The resulting biochar shows mixed meso‐ and micropores, high specific surface area and low oxygen content. Owing to these features, the biochar demonstrates applications as a modest methylene blue adsorbent (adsorption capacity up to 8.2 mg/g), satisfactory supercapacitor electrode (specific capacitance up to 135 F g −1 ), and superior CO 2 adsorbent (maximum capacity 4.05 mmol g −1 ). Moreover, we propose that the biochar production can be combined with other established processes for implementing circular economy to achieve concentrated seawater valorization, carbon sequestration and waste minimization.
ABSTRACT Anaerobic digestion (AD) is a well‐established technique that provides numerous advantages, including efficient waste treatment and the concurrent generation of renewable energy. Multiple factors can considerably influence the efficiency of biogas production in AD systems. Nevertheless, understanding the fundamental principles of AD and identifying the key factors that affect biogas generation efficiency is critical. Here, we provide a comprehensive overview of the key factors influencing the AD process and a narrative review of current literature to understand progress in this field. The current review focuses on biogas production processes, particularly those involving organic waste. Subsequently, the factors affecting the AD process, such as feedstock composition, pretreatment methods, operational parameters, reactor design, and microbial community dynamics, were detailed. This review highlights that AD remains a viable solution for waste management and renewable energy production, with significant potential for efficiency improvement through optimized operating conditions, advanced reactor designs, and innovative pretreatment and microbial strategies. Moreover, the review shows that while combined pretreatment strategies may have synergistic effects on AD, their industrial adoption still requires standardized frameworks and adaptive, multi‐parameter control systems for variable organic waste. This review contributes to a better understanding of AD as a viable solution to the waste crisis, while also considering its implications for sustainability.
ABSTRACT The present study employs a novel method for the synthesis of graphene oxide (GO) based ternary composite utilized for the adsorption of Congo red (CR), an anionic dye molecule. The GO was synthesized using the well‐known Hummer's method and subsequently incorporated with binary metal oxide (NiO‐ZrO 2 ) and zeolite by a hydrothermal approach. The GO/NiO‐ZrO 2 /zeolite composite was characterized via different analytical methods, including FTIR, PXRD, FESEM‐EDX, Raman spectroscopy, BET‐surface area and XPS which exhibited encouraging characteristics for CR dye removal. The prepared composite exhibited a specific surface area of 144.48 m 2 /g. To evaluate the removal efficiency of the synthesized composite, optimizations were performed regarding starting dye amount, amount of adsorbent, adsorption time, and solution pH. The optimized parameters were observed at an adsorbent amount of 1.0 g/L, starting dye amount of 60 mg/L, adsorption time of 180 min, and pH of 5 at room temperature. At these conditions, the composite achieved the highest removal efficacy of 97.02 ± 0.32%. The composite was reusable upto third adsorption desorption cycle. Furthermore, the isotherm and kinetics models were applied to investigate the adsorption characteristics of GO/NiO‐ZrO 2 /zeolite with respect to CR dye. The GO/NiO‐ZrO 2 /zeolite composite exhibited the highest adsorption capability of 142.85 mg/g.
ABSTRACT Significant quantities of fiber waste are generated across the textile production chain, a substantial portion of which—particularly the short fibers arising from fabric finishing processes such as sueding—is typically incinerated due to its inadequate length and incompatibility with conventional blow‐room processing. This study demonstrates the upcycling potential of recycled dyed fiber waste (RDFW) from the sueding process by converting it into high‐value rotor‐spun yarn. The RDFW in tuft form were directly introduced into the carding machine, circumventing the blow‐room stage that conventionally rejects short fibers. Specifically, 14Ne and 16Ne open‐end rotor yarns were produced by incorporating 5% and 10% RDFW, and their uniformity and tensile properties were systematically evaluated and compared with yarns manufactured from carding machine waste (CMW) and post‐consumer waste fibers (PCMW). The results reveal that the developed yarns exhibited superior evenness, with notably lower CVm% and imperfection index (IPI) compared to those produced from CMW and PCMW. Furthermore, the findings demonstrate that 14Ne rotor‐spun yarn incorporating up to 10% RDFW can effectively serve as a high‐quality substitute for rotor yarns made from CMW and PCMW. A single jersey knitted fabric was produced from the developed yarn to assess its esthetic appeal and potential end‐use applications. The pre‐dyed nature of the RDFW eliminates the need for additional dyeing, thereby enabling the production of inherently colored or mélange yarns while significantly reducing water, energy, and chemical consumption. Furthermore, repurposing RDFW can substantially mitigate the environmental burden associated with virgin fiber production, offering potential savings of 6000–22,000 L of water and approximately 1.2 kg of CO 2 per kilogram of fiber. Overall, the upcycling of RDFW emerges as a practical and viable strategy to valorize textile finishing waste and advance circular economy principles in sustainable textile manufacturing.
ABSTRACT Hydrothermal liquefaction (HTL) represents a promising thermochemical pathway for recycling recalcitrant plastic waste, such as polyethylene (PE), offering high conversion efficiency under relatively mild operating conditions. However, oils produced by non‐catalytic HTL typically consist of heterogeneous hydrocarbons, including paraffins, olefins, cyclic hydrocarbons, and aromatics, which complicates downstream refining. This study investigates the catalytic HTL of low‐molecular‐weight polyethylene (LWPE) over a Pt/C catalyst. Experiments were conducted in supercritical water at 425°C, with reaction times varied between 0.5 and 2.5 h to evaluate effects on product distribution and the composition of the GC‐MS‐detectable oil fraction. Within the experimental uncertainty, Pt/C did not significantly change the bulk product‐yield distribution relative to non‐catalytic HTL under the conditions examined. However, the GC‐MS‐detectable oil fraction from Pt/C‐catalyzed HTL showed pronounced enrichment of paraffinic hydrocarbons at shorter reaction times, indicating that Pt/C can influence product composition even when bulk yields remain comparable. By integrating oil, gas, and aqueous‐phase compositional analyses with product yield distributions, plausible reaction pathways for catalytic HTL of PE over Pt/C are proposed. These results provide insight into tuning product composition during HTL of PE and support the rational design of catalytic chemical recycling strategies for recalcitrant polyolefin waste.
ABSTRACT Growing environmental concerns associated with synthetic materials have intensified the demand for sustainable alternatives derived from renewable sources. In addition, the increasing global population has led to a surge in the demand for food products including juice, resulting in the generation of substantial quantities of byproducts, which are organic waste with the potential for valorization. This study investigated the bioconversion of carrot pomace (CP), waste generated in the juice industry, into fungal biomass to produce mycelium‐based foams. Filamentous fungus (Aspergillus oryzae) was cultivated on carrot pomace through a submerged process in a bubble column bioreactor. The analysis of the scanning electron microscopy (SEM) confirmed the presence of the fungal mycelium and CP residues in the material recovered from the bioreactor. This material was mixed with water, and the suspension was subjected to different grinding cycles in an ultrafine grinder, and mycelium‐based foams were then formed via freeze‐molding and freeze‐drying. The resulting foams exhibited an average density of 21.1 kg/m3, with compressive resistance values of 5.8 kPa at 10% deformation and 20.5 kPa at 30% deformation. These mechanical properties are comparable to those of commercial lightweight foams, as indicated by the Ashby material plot. These findings demonstrate the potential of mycelium‐based foams as an alternative to synthetic materials, contributing to waste valorization and development of environmentally friendly materials.
ABSTRACT Developing targeted functionalized photoelectrodes based on charge transfer kinetics is a pivotal strategy to achieve efficient photoelectrocatalytic (PEC) process. Herein, Bi2WO6@Black‐TiO2 hierarchical heterogeneous network architectures are prepared by coupling Bi2WO6 nanosheets with a three‐dimensional B(black)‐TiO2 network structure via a sequence simple hydrothermal/solvothermal strategy for application in water pollution remediation. The optimized Bi2WO6@B‐TiO2‐2.0 photoelectrode exhibits excellent PEC degradation efficiency for sulfamethoxazole and various organic pollutants, including reactive brilliant blue KN‐R, rhodamine B, and bisphenol A. And the Bi2WO6@B‐TiO2‐2.0 photoelectrode also demonstrated well catalytic stability by long‐term stability and recycling experiments, which can be attributed to its unique nanonetwork structure bringing an abundance of active sites. Furthermore, a S‐Scheme carriers transfer mechanism with solid ability to induce long lifetime electron/hole with strong redox, was identified via in situ x‐ray photoelectron spectroscopy and time‐resolved photoluminescence, resulting in the efficient production of active species (·OH and·O2−) to achieve superior PEC degradation efficiency. The work reveals Bi2WO6@B‐TiO2‐2.0 as promising catalysts for water remediation but also unlocks that S‐Scheme heterojunctions facilitate carrier transport and utilization, guiding the designing of heterojunctions for other optoelectronic applications.
ABSTRACT The treatment of oily wastewater is a critical challenge due to the limitations of conventional separation technologies in handling stable oil‐in‐water (O/W) emulsions. This study presents a hyperbranched polylysine (HBPL)‐based molecular brush membrane modified with tricarballylic acid (TCA) for efficient and antifouling O/W emulsion separation. The tailored carboxyl‐terminated hyperbranched architecture endowed the membrane with superhydrophilicity, underwater superoleophobicity, and a pronounced negative charge. Characterizations demonstrated that the modified membrane exhibits significantly enhanced separation efficiency and superior fouling resistance against both oil and protein contaminants. The exceptional performance is attributed to the synergistic effects of a robust hydration layer and the strong electrostatic repulsion provided by the hyperbranched molecular brush, which effectively minimize foulant adhesion. Furthermore, the membrane showed good chemical stability across a wide pH range. This work presents a feasible surface‐engineering strategy using hyperbranched molecular brushes to achieve high‐performance, durable membranes for challenging oily wastewater treatment.
ABSTRACT To minimize liquid waste generation and enhance resource utilization in nuclear waste treatment, this study integrates molten salt electrolysis‐a dry processing technique—with 5 Å molecular sieve adsorption. This study first examines the electrochemical behavior of MgCl2 at an inert tungsten electrode, followed by investigation of CeCl3 redox processes at a Mg‐coated electrode, enabling successful cerium electrodeposition on the Mg substrate. ICP‐OES measurements of rare earth concentrations in molten salt pre‐ and post‐electrolysis determine a 92.79% average cerium extraction rate. Subsequent kinetic and intraparticle diffusion modeling reveals Ce adsorption conforms to the pseudo‐second‐order kinetic model, indicating chemisorption‐dominated mechanisms. Ultimately, molecular sieve adsorption achieves 99.89% elimination efficiency for residual Ce(III) in post‐electrolysis molten salt. Based on molten salt electrolysis, this study applies 5 Å molecular sieve technology to achieve enhanced adsorption of rare earth elements, thus enabling efficient recovery. This methodology significantly improves the separation efficiency of fission products in reprocessing operations, while simultaneously enabling the effective recycling of radioactive molten salts and substantially reducing waste production. The developed approach offers innovative solutions and technical foundations for nuclear waste management and resource reclamation.
ABSTRACT Polyethylene terephthalate (PET) is one of the major polymeric plastic products, with an annual production of over 24 million tons. Revalorization of plastic waste holds the promise of transforming end‐of‐life plastic materials towards cleaner and more sustainable product use. Cement is essential to shape the built environment by developing long‐lasting, stable structures. While plastic materials have shown low adhesion with cement, the functionalization of PET (FPET) surfaces can enhance the interaction with a cementitious matrix. Herein, we present a new functionalization strategy that enables polymer‐cementitious composites while enhancing the energy absorption capacity and ductility of cementitious beams. This cleaner manufacturing technique can provide an alternative application of waste polymeric products while enabling alternative market opportunities in construction. Complete standard rheological and mechanical characterization of composite cement, including fracture tests, are presented. A significant improvement in modulus of rupture, energy absorption, and ductility was observed when 12% FPET and 16% FPET were included. This suggests that the FPET is strongly bonded to cement, enabling stress transfer across the cracked surfaces, increasing ductility and energy absorption.
ABSTRACT At present, the increasing discharge of hazardous and toxic pollutants into freshwater bodies has become a major global concern due to its detrimental effects on human health and aquatic ecosystems. The growing challenges and a complex suite of problems related to water pollution and scarcity demand technological innovations, reuse strategies, and sustainable solutions. Therefore, developing efficient, affordable, and eco‐friendly wastewater treatment technologies is crucial. An oleaginous photosynthetic organism “microalga” has emerged as a valuable feedstock for wastewater treatment, carbon neutrality, and nutrient recovery. On the other hand, setting up microalgal biorefineries support resource recovery and biomass utilization, offering diverse bio‐based products across industries. For instance, the global microalgal biofuel market is projected to reach USD 8.7 billion by 2030, while microalgal nutraceuticals including omega‐3 fatty acids already command a market value of over USD 2.5 billion annually, with pigments like astaxanthin valued at USD 1500–7000 per kg. Similarly, microalgal biomass for biofertilizers and animal feed additives contributes to a market share exceeding USD 1.2 billion globally. This multifaceted approach facilitates the reduction of waste generation by enhancing production of microalgae bioproducts. Unlike terrestrial crops like soybean that require 2000–3000 L of freshwater per kg biomass, microalgae cultivation in wastewater systems can reduce the water footprint to less than 100 L per kg biomass, achieving > 95% reduction in freshwater demand. Keeping this in mind, present review instigates the integrated phycoremediation approach that aligns with circular economy goals, promoting resource recovery and reducing the carbon footprints and water footprints in the framework of regenerative and zero waste valorization.
Basic sanitation and access to drinking water are critical challenges for developing countries. By 2025, water scarcity could affect 50% of the global population. Given this scenario, the search for sustainable and cost-effective water purification methods has driven research into the application of biologically synthesized silver nanoparticles (AgNPs). In this study, AgNPs were produced using the filamentous fungus Aspergillus niger IBCLP20 and encapsulated in calcium alginate (AgNP IBCLP20/CA ) for use in a packed-bed reactor (PBR) to treat water contaminated with Escherichia coli IPT245 and Pseudomonas aeruginosa IPT365. To evaluate the process parameters for water disinfection, the following variables were assessed: influent bacterial concentration (10 3 , 10 4 , and 10 5 CFU·mL −1 ), temperature (25°C, 30°C, 37°C, and 40°C), reactor occupancy (50%, 75%, and 100%), and volumetric feed flow rate (1.0, 4.0, 7.0, and 10.0 mL·min −1 ). In the experiments, P. aeruginosa IPT365 exhibited greater resistance compared to E. coli IPT245. For both bacteria, the best antimicrobial results were obtained at an influent concentration of 10 3 CFU·mL −1 . Temperature had no significant impact on the system for either of the bacterial strain. The antimicrobial activity against E. coli IPT245 was observed for all reactor occupancy levels tested, whereas the bactericidal effect against P. aeruginosa IPT365 was only achieved when the PBR was filled to 100% of the catalyst mass. The optimum volumetric flow rate was determined to be 4.0 mL·min −1 . These findings confirm that the PBR with encapsulated AgNP IBCLP20/CA is a promising approach for water disinfection. The maintenance of antimicrobial activity after nanoparticle encapsulation, along with a detailed analysis of operational parameters, supports the feasibility of this method for environmental applications.
The mounting global waste crisis demands forward-looking solutions rooted in circular economy principles and sustainable material flows, as well as resource efficiency. This review examines emerging technological approaches in recycling, upcycling, and downcycling, emphasizing their roles in enhancing environmental sustainability, economic viability, and social equity. Recycling is transforming through the integration of artificial intelligence–driven sorting, advanced material separation, and chemical recycling technologies, which enable the recovery of high-purity materials from complex waste streams. Upcycling leverages design thinking, biotechnology, and creative engineering to generate higher-value products from waste, reducing dependency on virgin materials and contributing to sustainable production systems. Downcycling, although resulting in lower value outputs, remains essential for diverting residual waste from landfills and supplying secondary materials for industries such as construction, textiles, and agriculture. This review critically evaluates how policy instruments, market-based incentives, and community participation shape the success of waste valorization efforts across diverse socio-economic contexts. Comparative insights from both industrialized nations and the Global South reveal that integrated, context-specific waste management approaches can significantly improve material recovery rates while minimizing environmental footprints. Key findings highlight the importance of harmonizing technological innovation with participatory governance and life cycle thinking. The review concludes with recommendations for advancing systems-based modeling, expanding life cycle assessment tools, and fostering interdisciplinary collaborations to optimize the performance, profitability, and sustainability of circular waste management systems in the face of climate change and growing urbanization.
Hydrochar–metal composites exhibit significant potential in catalysis and energy storage due to their tunable pore structures, high surface areas, and adjustable physicochemical properties. This review systematically examines preparation methods, phase equilibrium behavior, and thermophysical properties of these composites. Microstructural control is achieved by varying biomass types, hydrothermal conditions (temperature, time, pH), and metal incorporation approaches (direct addition or pretreatment). Metal type and content critically influence phase equilibrium, governing thermal conductivity (TC), specific heat capacity (SHC), and thermal expansion coefficient (CTE). Uniform metal dispersion and stable integration with the carbon matrix enhance catalytic activity and energy storage performance. High TC improves thermal management in catalysis, while high SHC and low CTE enhance energy storage stability by mitigating thermal fluctuations and mechanical stress. Challenges include phase equilibrium modeling, thermophysical characterization under extreme conditions, and scalable synthesis optimization. Future research should leverage machine learning, multifield coupling experiments, and advanced characterization to guide high-performance composite design.
The rapid emergence of lithium-ion batteries (LIBs) to satisfy our ever increasing energy demands will result in a significant future waste problem at their end of life. Lithium iron phosphate (LFP) as a cathode material is now widely used in LIBs with increasing market share. It is expected that there will be significant volumes of battery waste containing this material in the near future, and therefore it is important to develop methods for effectively repurposing this LFP waste to mitigate its impact on the environment. In this work we demonstrate the repurposing of LFP from spent LIBs as electrocatalysts for the oxygen evolution reaction (OER) which is critical to electrochemical water splitting and the production of green hydrogen. Our study has shown that the recovered LFP once immobilized onto a Ni substrate reconstructs into a mixed Fe/Ni oxide surface layer which is highly active for the OER. Promisingly, the LFP recovered from batteries that were cycled multiple times (up to 100 cycles) showed excellent electrocatalytic performance with a low Tafel slope of 58 mV dec −1 , overpotential values of 250 and 310 mV to reach 10 and 100 mA cm −2 , respectively and 24 h stability at over 200 mA cm −2 . This research provides potential motivation for recycling companies to isolate LFP from spent Li ion batteries for later use in water electrolysis technologies.
