Multiple Regeneration Cycles Research Articles

Rapid and selective separation of heavy metal ions from aquatic medium using a bidentate functionalized hybrid material

Low-cost mesoporous silica material, functionalized with a bidentate pyrazolyl pyridine metal acceptor and presenting a high specific surface area of 417 m²/g, was synthesized (mSi-L3) using a two-step procedure and characterized in detail to confirm the successful covalent binding onto silica surface. Notably, mSi-L3 exhibited strong selectivity for PbII among CdII and CuII ions, and displayed rapid metal ion removal, typically less than 10 min, from water samples.The influence of various environmental parameters on the adsorption process, such as pH, contact time and temperature, was systematically investigated. Optimal adsorption of metal ions was achieved at pH 6, as lower pH values reduced the availability of active sites due to competitive hydronium ion presence. Kinetic studies indicated that the adsorption process adhered to the pseudo-second-order model, suggesting a chemisorption mechanism. Temperature significantly influenced the adsorption capacity, with increased temperatures enhancing metal ion removal and confirming the endothermic nature of the process. The isotherm study suggests that the Langmuir model accurately describes the adsorption process, confirming that CuII, CdII and PbII ions are adsorbed as a monolayer on the homogeneous surface of m-SiL3 material, implying that the material has uniform adsorption sites where each metal ion occupies a distinct site without interaction with neighbouring ions. These findings underscore the importance of optimizing environmental conditions to maximize the efficiency of mSi-L3 for heavy metal removal. Also, mSi-L3 demonstrated excellent stability, with only a slight (∼1−3 %) decrease in functional groups on its surface after multiple regeneration cycles. Extensive analytical studies conducted with real water samples provided further evidence of the stability and effectiveness of mSi-L3 for the separation of metal trace elements of lead, copper and cadmium.

Simplified synthesis and identification of novel nanostructures consisting of cobalt borate and cobalt oxide for crystal violet dye removal from aquatic environments

Crystal violet dye poses significant health risks to humans, including carcinogenic and mutagenic effects, as well as environmental hazards due to its persistence and toxicity in aquatic ecosystems. This study focuses on the efficient removal of crystal violet dye from aqueous media using novel Co3O4/Co3(BO3)2 nanostructures synthesized via the Pechini sol–gel approach. The nanostructures, which were abbreviated to EN600 and EN800, were fabricated at calcination temperatures of 600 and 800 °C, respectively. X-ray diffraction (XRD) analysis revealed that the synthesized samples have a cubic Co3O4 phase and an orthorhombic Co3(BO3)2 phase, with mean crystal sizes of 43.82 nm and 52.93 nm for EN600 and EN800 samples, respectively. The Brunauer–Emmett–Teller (BET) surface areas of EN600 and EN800 samples were 65.80 and 43.76 m2/g, respectively, indicating a significant surface area available for adsorption. Optimal removal of crystal violet dye was achieved at a temperature of 298 K, a contact time of 70 min, and a pH of 10. The maximum adsorption capacities were found to be 284.09 mg/g for EN600 and 256.41 mg/g for EN800, which are notably higher compared to many conventional adsorbents. The adsorption process followed the pseudo-second-order kinetic model and fitted well with the Langmuir isotherm. The adsorption was exothermic, spontaneous, and physical in nature. Moreover, the adsorbents exhibited excellent reusability, retaining high efficiency after multiple regeneration cycles using 6 mol/L hydrochloric acid. These findings highlight the potential of these Co3O4/Co3(BO3)2 nanostructures as effective and sustainable materials for water purification applications.

Preparation of novel ACMO-AA/PVDF composite membrane by one-step process and its application in removal of heavy metal ions from aqueous solutions

In this study, a simple one-step process was used to fabricate a high-efficiency 4-acryloylmorpholine-acrylic acid/polyvinylidene fluoride (ACMO-AA/PVDF) composite membrane for the adsorption of heavy metal ions. The initiation phase involved the use of the strong organic base tetramethylammonium hydroxide (TMAH) to facilitate the partial dehydrofluorination of PVDF, thereby yielding a reactive CC bond. Following this, undesirable residuals and by-products of TMAH were removed through a thermal treatment process. Subsequently, an ACMO and AA, both possessing distinctive functional groups, onto the active CC bond took place in-situ. The use of a suitable initiator (AIBN) and crosslinking agent (MBA) facilitated the copolymerization process, culminating in the production of the ACMO-AA/PVDF composite membrane with excellent capability for the adsorption of heavy metal ions. Performance evaluations confirmed the membrane high efficiency in Pb2+ removal with complete removal realized at initial Pb2+ concentrations of ≤50 mg·L–1 and presenting a maximum adsorption capacity of 1214.75 mg·g–1, as described by the Langmuir model. In complex environments with co-existing metal ions such as Cu2+, Hg2+, and Cd2+, at an each initial concentration of up to 50 mg·L–1, the membrane exhibited a Pb2+ removal rate of 93.81 %, and Hg2+ and Cu2+ removal rates of 93.75 % and 92.93 %, respectively. The results of surface morphological and microstructural analyses showed that the principal adsorption mechanism is chemical chelation. Furthermore, the membrane exhibited sustainable usability, retaining its structural integrity and adsorption efficacy over multiple regeneration cycles. This indicates that the ACMO-AA/PVDF composite membrane is a viable candidate for deep decontamination processes involving Pb2+, Hg2+, and Cu2+ in environmental remediation applications.

Coke formation and mineral accumulation on HZSM-5/Al2O3 catalysts during in-situ catalytic fast pyrolysis of microalgae over multiple regeneration cycles

Catalyst deactivation caused by coke formation and mineral accumulation occurs simultaneously and intensively during the catalytic pyrolysis of biomass. A comprehensive understanding of their distinction and interactions during the deactivation and regeneration process of shaped catalysts are essential for catalyst advancement and longevity in industrial application. In this study, we report the reversible and non-reversible catalyst deactivation caused by coke formation, mineral accumulation and the interactions thereof by a multi-technique characterization of a HZSM-5/Al2O3 catalyst (crushed extrudates; particle size 1–3 mm) in fast pyrolysis. A total of 5 cycles of catalyst reaction/regeneration were performed in a bench scale reactor (60 g/h feedstock feeding rate; pyrolysis temperature of 500°C) using both raw microalgae (Scenedesmus almeriensis, or SA) and citric acid treated microalgae (CA-SA). The measured properties of the fresh and used catalysts (SA-R5, 5th recycled and reacted catalyst mixed with SA) disclosed the anticorrelation of the metal contents (increased by a factor of 2.5 times) with surface area (-4.4 %) and Brønsted acid (-70.4 %). The presence of minerals in the feedstock might catalytically alter the pyrolysis chemistry, interfere with the shape selectivity and acidity of the catalysts, thus reduced the formation of coke. Additionally, metal species from the microalgae ash that ended up on the catalyst could promote coke combustion during the regeneration process. This work revealed the demineralization of the microalgae prior to fast pyrolysis minimized the rate of irreversible catalyst deactivation. Whereas, the trade-off between promoted coke formation after the ash removal of microalgae and accelerated minerals accumulation without microalgae demineralization should be evaluated.

Regulating the Interface Polarity Distribution of Zr-Based MOFs by Amino Acid-Like Ligand Functionalization Enables Efficient Recovery of Gold.

The recovery of gold from industrial effluents is crucial for environmental conservation, sustainable resource management, and promoting the green development of gold resources. We designed a Zr-based MOF (UKM-78) by incorporating functional organic ligands that resemble amino groups, using MOFs' inherent sieving effect for ion separation. This novel material exhibited enhanced gold recovery under acidic conditions, with an adsorption capacity three times and an adsorption rate four times higher than those of nonfunctionalized UKM-77. Notably, UKM-78 efficiently captured gold solutions at concentrations as low as 1 ppm and achieved an adsorption rate exceeding 90%, owing to the electrostatic interactions and coordination between its functionalized groups and the synergistic effect of its porous structure. Despite multiple regeneration cycles, UKM-78 retains 99.4% of its adsorption capacity. X-ray photoelectron spectroscopy (XPS), kinetic studies, and thermodynamics collectively demonstrated that Au(III) binding on UKM-78 involved cooperative electrostatic interactions and chemical adsorption through coordination. This study highlights the potential of MOFs for efficient and sustainable recovery of gold from complex waste streams.

Introducing Diels‐Alder reaction with carbon nanotubes for the enhanced repair performance of epoxy resin modified asphalt

AbstractEpoxy asphalt, a thermosetting polymer, is characterized by stable, irreversible internal chemical bonds that prevent recovery and spontaneous micro‐crack healing, unlike conventional asphalt. This study introduces a renewable nano‐modifier synthesized via esterification of carboxyl‐functionalized carbon nanotubes (CNTs‐COOH) and furfuryl alcohol (FA), termed CNTs‐FA. The successful synthesis of CNTs‐FA was confirmed through various microscopic techniques. Integrating CNTs‐FA into epoxy asphalt materials, the optimal dosage was identified as 0.05% of the total epoxy asphalt mass using tensile tests and fluorescence microscopy. Thermal reversible effects and mechanisms were further analyzed through multiple regeneration cycles using tensile properties, fluorescence microscopy, and infrared spectroscopy. The study elucidates that the thermal reversibility in epoxy asphalt is facilitated by the Diels‐Alder (DA) reaction between the conjugated diene structure in FA and the curing agent oleylamine. This research provides an effective solution to the non‐recoverability and unrepairable micro‐cracks of traditional epoxy asphalt mixtures.Highlights CNTs‐FA was successfully prepared by esterification reaction. Using nano modification methods, introduce DA reaction into curing system. Renewable function of epoxy asphalt by DA reversible reaction.

Construction of coal fly ash-based spherical grain adsorbents and their adsorption characteristics on phenolic compounds

Addressing the significant emissions and severe pollution hazards posed by coal fly ash waste in the coal chemical industry, as well as the challenges in recovering phenolic substances from coal chemical wastewater, this study utilized coal fly ash as a raw material to construct two types of spherical grain adsorbents: coal fly ash and coal gangue spherical grain (CFAGsg) and coal fly ash and pyrite spherical grain (CFAPsg). The adsorption performance of CFAGsg and CFAPsg towards phenolic substances in coal chemical wastewater was investigated. The research results demonstrated that CFAGsg and CFAPsg exhibited adsorption capacities of 20.31 mg/L and 30.42 mg/L for phenol, respectively, and maintained stable adsorption performance even after multiple regeneration cycles. Further analysis using kinetic, isotherm, and thermodynamic models, along with various characterization techniques, revealed that the adsorption of phenol onto CFAGsg and CFAPsg was primarily governed by physical and chemical adsorption, involving an endothermic reaction. Moreover, the study on the adsorption mechanism of phenol revealed that the adsorption behavior of CFAGsg and CFAPsg was mainly driven by pore filling, π-π stacking, and hydrogen bonding. Additionally, hydrophobic interactions were involved in the adsorption of phenol onto CFAGsg, while surface complexation forces played a role in the adsorption of phenol onto CFAPsg. Overall, the research findings provide vital theoretical support and practical application prospects for the high-value utilization of coal fly ash and the clean production of the coal chemical industry.

Gas-phase surface modification to control catalyst structure and yields in methane dehydroaromatization

Methane dehydroaromatization (MDA) is a promising approach for direct methane transformation to aromatics and hydrogen. The benchmark catalyst Mo/H-ZSM-5 struggles to find commercial adoption because of thermodynamically-limited yields and rapid coking on Brønsted acid and molybdenum carbide species, especially on zeolite external surfaces. Here, gas-phase atomic layer deposition (ALD) overcoats H-ZSM-5 external surfaces with SiO2 or Al2O3. NH3-TPD, HRTEM, and textural properties show that these overcoats exclusively passivate zeolite external surfaces. Under MDA conditions, SiO2 gives softer coke and increases cumulative benzene yields by 25 %, while Al2O3 strongly decreases yields. H2-TPR and UV–visible and Raman spectroscopy show how the overcoats redisperse the MoOx precatalysts, especially over multiple deactivation and isothermal oxidative regeneration cycles. Combined with 27Al-MAS NMR, MoOx redistribution and dealumination are seen as the causes of long-term deactivation over multiple regeneration cycles, and this process continues to occur regardless of the overcoat. Overall, the deposition of a small amount of silica on the outer surface of Mo/H-ZSM-5 reduces the formation of hard coke, which could be regenerated by milder methods such as hydrogen treatment.

Novel granular bentonite-carbon sorbents: textural characterization, adsorption-desorption isotherm, kinetics, and cost estimation.

This research focuses on the synthesis of novel low-cost granular sorbents based on bentonite clay of the Navbahor deposit, dust fraction of Angren brown coal, and agricultural wastes such as straw and sawdust to meet the internal needs of the Republic of Uzbekistan. The impact of the initial mixture ingredients on the structural and textural properties of bentonite-coal sorbents (BCSs) has been studied using X-ray diffraction, Raman spectroscopy, Fourier-transform infrared spectroscopy, optical microscopy, and nitrogen adsorption-desorption analysis. For determining the sorption capacity of BCSs, a standard model substance methylene blue (MB), was applied. It was revealed that the maximum adsorption amount of MB was 5.3 mg∙g-1 during 2 h of contact. Prolonging the contact time to 24 h allowed for more extensive diffusion of dye molecules into the sorbent's pores, increasing the adsorption capacity to 13 mg∙g-1. It was demonstrated that BCSs could be regenerated by strong oxidizing agents such as sulfuric acid and hydrogen peroxide, with sulfuric acid proving more effective. Regeneration fully restores sorption properties, particularly at low dye concentrations (up to 0.2 mg∙ml-1). Despite slight reductions in adsorption capacity over multiple regeneration cycles, the sorbents maintain their structural integrity and durability. It is shown that compared to imported expensive activated carbon, the gross profitability of the in-house production of such granular BCSs within the territory of Uzbekistan increases from 48 to 78%, while the net income increases almost three times.

TPU/PEI nanofibers for the efficient removal of PFOA and its analogs: Effect of pH, humic acid and co-existing ions, mechanism, and regenerative effects

Perfluorooctanoic acid (PFOA) and its analogs, such as perfluorocaproic acid (PFHxA), perfluorobutyric acid (PFBA), and perfluoro(2-methyl-3-oxahexanoic) acid (GenX), present environmental contamination concerns due to their toxicity. To addressing this, in this study, we have explored the utility of thermoplastic polyurethane/polyethyleneimine (TPU/PEI) nanofibers, synthesized via electrospinning, for the efficient removal of PFOA and its analogs from aqueous solutions. Combining the positively charged amino groups of PEI and hydrophobicity of TPU potentially enhances adsorption. Further, the TPU/PEI nanofibers exhibit a distinctive nano-phase separation morphology, creating abundant adsorption sites conducive to PFAS binding. Batch adsorption experiments indicated that TPU/PEI nanofibers possess notable adsorption capacities for PFOA and its analogs. The observed adsorption capacities were ranked as follows: PFOA (0.931 mmol/g) > PFHxA (0.872 mmol/g) > PFBA (0.827 mmol/g) > GenX (0.771 mmol/g), thus showing a correlation with their respective octanol–water partition coefficient (Kow) values. Both inorganic ions and organic matter exerted more pronounced adverse effects on the adsorption of PFBA and GenX than on those of PFOA and PFHxA. This observation can be linked to competitive adsorption with PFAS. Impressively, the TPU/PEI nanofibers maintained a high removal efficiency across multiple regeneration cycles, with more than 95 % adsorption capacity retained after five cycles. To the best of our knowledge, this study is the inaugural demonstration of utilizing a TPU and PEI blend for remediation of both long-chain and short-chain PFAS in highly polluted wastewater, positioning it as a promising, accessible material for such applications.

A porous media catalyst for waste polyethylene pyrolysis in a continuous feeding reactor

This study investigated the catalytic pyrolysis of waste polyethylene (PE) using a ZSM-5/Al2O3 porous media catalyst in a continuous feeding mode. The findings revealed that the porous media catalyst with 100 mm height and 40 PPI (pore per inch) pore size had the supreme catalytic performance, which could obtain the highest pyrolysis oil yield and the light fraction (<C12) and aromatics in the oil, and improve the catalytic stability of the porous media catalyst. The optimal operating conditions were the pyrolysis temperature of 460 °C, the carrier gas velocity of 65 mL/min, and the plastic feeding rate of 25 g/h, of which the light fraction and aromatics in the oil were up to 95.25 % and 97.33 %. Moreover, the catalytic cycling performance of the porous media catalyst was thoroughly investigated. The catalytic activity declined and the catalyst deactivation rate decreased after multiple regeneration cycles. This study presents a comprehensive investigation of waste PE catalytic cracking using the porous media catalyst in continuous feeding mode, which can provide insightful guidance on the industrialization of plastic waste valorization.

Assessment of chromite ore wastes for methylene blue adsorption: Isotherm, kinetic, thermodynamic studies, ANN, and statistical physics modeling

This research investigates the adsorption potential of chrysotile and lizardite, two minerals derived from chromite ore wastes, for the uptake of Methylene Blue (MB) dye from waste streams. The characterization of these minerals involves XRD, XRF, FTIR, and SEM. Results confirm the dominance of polymorphic magnesium silicate minerals, specifically chrysotile and lizardite, in the samples. The FTIR spectra reveal characteristic vibration bands confirming the presence of these minerals. The SEM analysis depicts irregular surfaces with broken and bent edges, suggesting favorable morphologies for adsorption. N2 adsorption-desorption isotherms indicate mesoporous structures with Type IV pores in both adsorbents. The Central Composite Design approach is employed to optimize MB adsorption conditions, revealing the significance of contact time, adsorbent mass, and initial MB concentration. The proposed models exhibit high significance, with F-values and low p-values indicating the importance of the studied factors. Experimental validation confirms the accuracy of the models, and the optimum conditions for MB adsorption are determined. The influence of solution acidity on MB uptake is investigated, showing a significant enhancement at higher pH values. Isothermal studies indicate Langmuir and Freundlich models as suitable descriptions for MB adsorption onto chrysotile and lizardite. The maximum adsorption capacities of MB for chrysotile and lizardite were found to be 352.97 and 254.85, respectively. Kinetic studies reveal that the pseudo-first-order model best describes the adsorption process. Thermodynamic analysis suggests an exothermic and spontaneous process. Statistical physics models further elucidate the monolayer nature of adsorption. Additionally, an artificial neural network is developed, exhibiting high predictive capability during training and testing stages. The reusability of chrysotile and lizardite is demonstrated through multiple regeneration cycles, maintaining substantial adsorption potential. Therefore, this research provides comprehensive insights into the adsorption characteristics of chrysotile and lizardite, emphasizing their potential as effiective and reusable sorbents for MB uptake from wastewater.

Deep eutectic solvent‐assisted selective extraction of valuable metals from waste lithium‐ion batteries

AbstractA novel synergistic extractant consisting of a deep eutectic solvent (DES) and tri‐n‐butyl phosphate (TBP) is proposed for selective extraction of valuable metals from waste lithium‐ion batteries (LIBs). The extraction efficiencies of Ni2+, Co2+, and Mn2+ were 99.8%, 99.1%, and 95.9%, respectively, and high‐purity Li+ was enriched in the raffinate after the single‐stage extraction. Valuable metal salts, lithium carbonate (92.3 wt%) and cobalt oxalate (94.9 wt%), were obtained. The DES + TBP extractant retained its high extraction performance even after multiple regeneration cycles. The extraction process followed the so‐called “cation exchange mechanism” with thermodynamic properties of ΔH &lt; 0, ΔG &lt; 0, and ΔS &lt; 0. The molecular‐level extraction mechanism demonstrated that the extraction process was dominated by both electrostatic and coordination interactions between the metal ions and DES/TBP, based on quantum chemical calculations. This study aims to provide a new strategy for recycling valuable metals from waste LIBs.

Breakthrough Study of CO2 Adsorption and Regeneration Performance of Mn‐ and Ce‐Doped Ni–Al Layered Double Hydroxides Derived Mixed Oxides in Packed‐Bed Column

AbstractCarbon dioxide (CO2) capture is an important strategy to mitigate greenhouse gas emissions and reduce global warming effects. This study synthesizes two nanomaterials, Ce‐doped Ni–Al mixed metal oxide (CNAO) and Mn‐doped Ni–Al mixed metal oxide (MNAO), from Mn‐ and Ce‐doped Ni–Al‐layered double hydroxides using a co‐precipitation method followed by a calcination process. The materials are characterized using various techniques, such as High‐resolution transmission electron microscopy‐energy dispersive x‐ray spectroscopy/selected area electron dispersion (HRTEM‐EDS/SAED), X‐ray diffraction (XRD), x‐ray photoelectron spectroscopy (XPS), Brunauer‐Emmett‐Teller (BET), and attenuated total reflection Fourier transform infrared (ATR FT‐IR). The CO2 adsorption performance of the materials is evaluated using packed‐bed column experiments at the testing conditions of 13 vol% ± 1 vol% CO2 in N2 simulated flue gas, flow rate of 20 mL min−1, inlet pressure of 14.15 ± 0.1 psi, and temperature of 31 °C ± 2 °C. The results show that both CNAO and MNAO are promising nanomaterials for CO2 capture applications due to their high CO2 adsorption capacity and efficiency. CNAO has a higher saturation capacity of 11.4 mmol g−1 and a longer breakthrough time than MNAO, which has a saturation capacity of 10.0 mmol g−1. The doping of Ce and Mn enhances the CO2 adsorption capacity of the materials compared to the un‐doped Ni–Al mixed oxide. The mechanisms of CO2 adsorption are mainly linearly adsorbed CO2, bidentate, and monodentate or bulk carbonate formation, as revealed by ATR FT‐IR analysis. The regeneration performance results suggest that CNAO is more stable than MNAO under multiple regeneration cycles and more promising material for large‐scale CO2 capture applications.

Rapid in situ regeneration of phenol-saturated activated carbon fiber by an electro-permonosulfate-ozone process: Performance, operators and mechanism

In this study, a new method that encompasses electricity, permonosulfate (PMS), and ozone (E-PMS-O3) was proposed and applied in the regeneration of phenol-saturated activated carbon fiber (ACF). Compared with traditional regeneration technology, the E-PMS-O3 process simultaneously regenerated exhausted ACF in situ and mineralized the desorbed pollutants effectively (78.67%) with relatively low energy consumption (4.338 kWh m−3). Furthermore, the E-PMS-O3 regeneration process only required 2 h, which was shorter than other well-documented electro-advanced oxidation processes (EAOPs), such as the E-O3 process lasting for 3 h, the E-persulfate process for 6 h, and the E-Fenton process for 6 h. Possible pathways in the regeneration process include direct electron transfer, ozone oxidation, PMS oxidation, non-radical reactions, and reactive oxygen species (ROS) oxidations. Two main ROS — hydroxyl radical (O•H) and sulfate radical (SO4•−) were probed and their contribution ratio was approximately 1:1. An external electric field visibly enhanced the recovery adsorption capacity of ACF and accelerated the decomposition of PMS. Interestingly, additional experiments revealed that adding two different oxidants (PMS/O3) provided a better protection effect on the properties of ACF against oxidation of oxidants and ROS. It's important to mention that the maximum concentration of byproducts remained below 5 mg g−1, which effectively minimized the potential for subsequent pollution. In the end, multiple regeneration cycles demonstrated that the regeneration efficiency was nearly 60% even after 6 cycles. Hence, the E-PMS-O3 process was promising for further exploration and discussion when applied in regeneration of exhausted AC materials.

Ce4+-Substituted Ni-Al mixed oxide: fluoride adsorption performance and reusability.

In this study, Ce4+-doped Ni-Al mixed oxides (NACO) were synthesized and comprehensively characterized for their potential application in fluoride adsorption. NACOs were examined using Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM), revealing a sheet-like morphology with a nodular appearance. X-ray diffraction (XRD) analysis confirmed the formation of mixed oxides of cubic crystal structure, with characteristic planes (111), (200), and (220) at 2θ values of 37.63°, 43.61°, and 63.64°, respectively. Further investigations using X-ray Photoelectron Spectroscopy (XPS) identified the presence of elements such as Ni, Al, Ce, and O with oxidation states +2, +3, +4, and -2, respectively. The Brunauer-Emmett-Teller (BET) analysis indicated that NACO followed a type IV physisorption isotherm, suggesting favorable surface adsorption characteristics. The adsorption kinetics was studied, and the experimental data exhibited a good suit to both pseudo-first order and pseudo-second order, as indicated by high R2 values. Moreover, the Freundlich isotherm model demonstrated a good fit to the experimental data. The result also revealed that NACO has a maximum capacity for adsorption (qmax) of 132 mg g-1. Thermodynamic studies showed that fluoride adsorption onto NACO was feasible and spontaneous. Additionally, NACO exhibited excellent regeneration capabilities, as evidenced by a remarkable 75.71% removal efficiency at the sixth regeneration stage, indicating sustained adsorption capacity even after multiple regeneration cycles. Overall, NACOs displayed promising characteristics for fluoride adsorption, making them potential candidates for efficient and sustainable water treatment technologies.

Scalable and sustainable radiative cooling enabled by renewable poplar catkin-derived films

Passive radiative cooling is a vital strategy for mitigating the greenhouse effect. However, the widespread use of synthetic plastics as the primary constituent raises environmental concerns of plastic waste. Addressing these challenges necessitates the development of radiative cooling materials based on natural and renewable resources. Herein, we utilize the abundant but underutilized poplar catkins, which are currently perceived as harmful, to fabricate a poplar catkin-derived (PC) film for radiative cooling. The PC film exhibits exceptional cooling performance, with a maximum cooling power of 75.3 W m−2 under an average sunlight intensity of 819 W m−2. Remarkably, the PC film achieves a sub-ambient temperature reduction of 6.2 °C during 9:00–13:00, within a similar solar radiation intensity. Additionally, the PC film possesses outstanding properties, including UV resistance, mold resistance, and renewability. Even after multiple regeneration cycles, the film experiences only marginal decreases of 0.9 % in sunlight reflectance and 1.4 % in infrared emissivity (8–13 μm). Furthermore, the resulting film demonstrates superior resistance to mildew compared to wood, highlighting its potential for long-term usability. This work not only addresses the environmental concerns associated with synthetic plastics but also harnesses the untapped potential of readily available natural resources to develop sustainable radiative cooling materials.

Design, synthesis, and characterization of thiol-decorated cross-linked graphene oxide framework for high-capacity Hg2+ ion adsorption

A 3D framework was effectively created by cross-linking graphene oxide nanosheets with 2,5-bis(((3-mercaptopropyl)dimethoxysilyl)oxy)terephthalohydrazide as a sulfur-containing linker, resulting in a successful synthesis of a novel chelating adsorbent. The resulting material showed remarkable efficiency in removing Hg2+ ions from polluted water, with a high adsorption capacity of 204.08 mg g−1 at pH 6 and 25 °C. The adsorption process followed a monolayer model described by the Langmuir isotherm, and the kinetics followed a pseudo-second-order model, indicating a chemical adsorption mechanism. The material demonstrated rapid adsorption and desorption, maintaining its performance even after multiple regeneration cycles. Overall, the synthesized 3D GOF stands out as an exceptional adsorbent due to its porous structure, efficient chelating functional groups, and robust efficacy in eliminating Hg2+ ions from contaminated water sources.

Microwave-induced fabrication of fiber-reinforced adsorbent from waste cardboard and chitosan for effective dye removal

An adsorption process is a familiar approach to the dye decontamination of polluted wastewater. Ecological and low-cost fabrication of a highly efficient adsorbent has been a typical predicament. Herein, we reported a microwave-assisted preparation of a waste-based three-dimensional fibrous material with reliable mechanical stability, efficient adsorbing characteristics, and excellent dye decontamination performance. The material was prepared by reinforcing the milled waste cardboard fibers using chitosan to establish dual-pore scaffolds composed of interconnected lamellar channels and random pores. The adsorbent demonstrated exceptional removal capacity for the dye solution which fitted well with the isotherm model of Langmuir and the thermodynamic analysis of the adsorption process verified the prominent physisorption process. The maximum removal efficiency of the obtained samples for 25 ppm dye solution was up to 99% at a maximum adsorption capacity of 53.87 mg g−1. It is also worth mentioning that m(CF/Ch-2)7 has consistent removal performance over multiple cycles of regeneration. These results featured to be a promising material for utilizing solid waste materials to address one major type of water pollution.

A novel magnetic manganese oxide halloysite composite by one-pot synthesis for the removal of methylene blue from aqueous solution

In this study, the magnetic manganese oxide halloysite composite was prepared by one-pot synthesis method. The methylene blue (MB) removal performance was synergistically enhanced by both adsorption capacity and Fenton-like degradation and the used particles can be separated by using an external magnetic field for the next regeneration. The prepared samples were characterized by XRD, FTIR, SEM, TEM, XPS, magnetic measurement and zeta potential. Characterization results illustrate that both Fe3O4 and MnO2 were successfully introduced and relatively well-distributed on the surface of halloysite nanotubes. A perfect magnetization property was obtained. In the removal process, the prepared sample exhibited the maximum adsorption capacity of methylene blue about 96.47 mg/g. The adsorption behavior results indicate that the pseudo-second-order model is more suitable to describe this process and MB adsorption was better described with the Langmuir model. After the removal reaction, the stable structure of the sample was proved by XPS and SEM. Moreover, the stable removal performance of the sample in the multiple cycles of regeneration indicates that the magnetic manganese oxide halloysite composite is an effective material for the methylene blue removal.