Search Results (851)

The efficient separation and removal of key nuclides is important for the nuclear fuel cycle from the aspects of radioactivity reduction and potential resource recycling. The urgent objective is to design and develop functional materials for the separation and removal of important nuclides. Porous silicon-based adsorbents are considered highly advantageous materials for separating and removing radioactive nuclides in complex environments due to their excellent mechanical properties, high porosity, and functionalization ability. In this review, we compiled the applications of porous silica-based materials in recent years in the separation and removal of key nuclides, such as actinides, lanthanides, strontium, cesium, iodine, and platinum group metals; discussed their separation and removal performances; analyzed the constitutive relationship between key radionuclides and porous silica-based adsorbents; and systematically described the properties and mechanisms of different types of porous silica-based adsorbents. This article aims to provide some ideas for the design of an advanced separation process in the nuclear fuel cycle. Full article

Heavy metal contamination of water is a critical environmental problem due to its toxicity and persistence in ecosystems. In this study, magnetic hydrogel spheres composed of carboxymethylated starch modified with poly(1-vinylimidazole) (CMS-g-PVI) and polyvinyl alcohol (PVA), combined with Fe₃O₄ nanoparticles, were synthesized and characterized to evaluate their efficiency in adsorbing metal ions such as Cu²⁺, Pb²⁺, and Cd²⁺. Structural characterization by FT-IR spectroscopy confirmed the successful integration of all functional components into the hydrogel matrix. Additionally, scanning electron microscopy (SEM) revealed a rough and porous surface morphology favorable for adsorption and an average bead diameter of 3.2 mm, influenced by the stirring rate during synthesis. Adsorption studies demonstrated maximum capacities of 82.4 mg·g⁻¹ for Cu²⁺, 66.5 mg·g⁻¹ for Pb²⁺, and 51.8 mg·g⁻¹ for Cd²⁺, with optimal removal efficiencies at pH 6.2 and 5.7. From a theoretical perspective, density functional theory (DFT) calculations using the B3LYP/6-311+G(d,p) method allowed the optimization of molecular structures and analysis of electronic properties. The total dipole moment (TDM) of the CMS-g-PVI/PVA system reached 20.81 Debye. A significant reduction in the HOMO-LUMO energy gap was observed upon metal adsorption, with values of 0.0308 eV for Cu²⁺, 0.0175 eV for Pb²⁺, and 0.0235 eV for Cd²⁺, confirming strong interactions between the hydrogel matrix and the metal ions. The combined experimental and computational approach provides a comprehensive understanding of the adsorption mechanisms and supports the development of efficient materials for water decontamination. Full article

Hexavalent chromium (Cr(VI)), a highly toxic and carcinogenic contaminant, presents a significant hazard to aquatic ecosystems and human health. Developing environmentally friendly, cost-effective, biodegradable, and easily recyclable adsorbents is critical for efficient Cr(VI) removal. Here, we present an innovative solution using a Mg/Al layered double hydroxide (LDH)-modified sphagnum cellulose gel (MgAl/LDH@SMCG), prepared by pre-treating sphagnum cellulose, crosslinking with polyvinyl alcohol, and doping with LDH. The resulting porous composite gel features abundant -COOH and -OH chelating groups, significantly enhancing its adsorption capacity and structural stability. The material’s structure and surface modifications were systematically characterized using SEM, TGA, FT-IR, and XPS. Batch adsorption experiments were conducted to assess the influence of adsorbent dosage, initial Cr(VI) concentration, pH, contact time, and temperature on performance. Adsorption kinetics, isotherms, and thermodynamics analyses revealed a primary mechanism of monolayer chemical adsorption, with experimental data closely fitting the Freundlich isotherm and pseudo-second-order kinetic models. The modified gel exhibits increased surface roughness and adsorption sites, resulting in markedly improved Cr(VI) removal efficiency. This study not only provides theoretical insights into Cr(VI) adsorption but also highlights the potential of LDH-functionalized cellulose gels for heavy metal wastewater treatment, offering a sustainable pathway for addressing global water contamination challenges. Full article

Chromium-containing wastewater poses severe threats to ecosystems and human health due to the high toxicity of hexavalent chromium (Cr(VI)). Although iron oxide nanoparticles (IONPs) show promise for Cr(VI) removal, their practical application is hindered by challenges in recovery and reuse. Herein, a novel three-dimensional porous nanocomposite, Artemia cyst shell biochar-supported iron oxide nanoparticles (ACSC@ IONP), was synthesized via synchronous pyrolysis of Fe³⁺-impregnated Artemia cyst shells (ACSs) and in situ reduction of iron. The optimized composite C@Fe-3, prepared with 1 mol/L Fe³⁺ and pyrolyzed at 450 °C for 5 h, exhibited rapid removal equilibrium within 5–10 min for both Cr(VI) and total chromium (Cr(total)), attributed to synergistic reduction of Cr(VI) to Cr(III) and adsorption of Cr(VI) and Cr(III). The maximum Cr(total) adsorption capacity was 110.1 mg/g at pH 2, as determined by the Sips isothermal model for heterogeneous adsorption. Competitive experiments demonstrated robust selectivity for Cr(VI) removal even under a 64-fold excess of competing anions, with an interference order of SO₄²⁻ > NO₃⁻ > Cl⁻. Remarkably, C@Fe-3 retained 65% Cr(VI) removal efficiency after four adsorption–desorption cycles. This study provides a scalable and eco-friendly strategy for fabricating reusable adsorbents with dual functionality for chromium remediation. Full article

As urbanization progresses rapidly, the pollution of heavy metal wastewater and the disposal of municipal solid waste incineration bottom ash (MSWI-BA) have emerged as significant challenges. MSWI-BA is a porous material recognized as an environmentally friendly adsorbent. To prevent escalating costs in future practical engineering applications, this study employed unmodified, natural MSWI-BA. This research assessed the adsorption capabilities of MSWI-BA for Pb(II) and Zn(II) through static adsorption experiments, which included adsorption kinetics and isotherm studies. The influence of various factors on the adsorption performance of MSWI-BA was investigated through adjusting the solution pH and the amount of ash, competitive adsorption conditions, and regeneration experiments. Advanced techniques, including ESEM-EDS, XRD, and FTIR, were utilized to analyze the adsorption mechanisms. The results indicated that under the conditions of pH values of 4 and 5, a temperature of 318 K, and an ash dosage of 0.1 g/20 mL, the maximum adsorption capacities of MSWI-BA for Pb(II) and Zn(II) were 89.09 mg/g and 33.77 mg/g, respectively. MSWI-BA demonstrates robust regeneration potential over multiple cycles, validating its practical feasibility. The principal mechanisms for removal include chemical precipitation, ion exchange, and surface complexation. By repurposing it as an efficient and low-cost adsorbent, this represents a sustainable strategy. Full article

Polyethyleneimine-based porous composites have been prepared by ring-opening polymerization of 2,2-bishydroxymethylbutanol-tris[3-(1-aziridinyl)propionate] (3AZ), a tri-aziridine compound, in water, in the presence of cyclodextrins (CDs), i.e., α-CD, γ-CD, methyl-β-cyclodextrin (Me-β-CD), monoacetyl-β-cyclodextrin (Ac-β-CD), and hydroxypropyl-β-cyclodextrin (HP-β-CD). The corresponding 3AZ-CD porous polymer composites were successfully obtained in most cases under a wide range of CD concentrations, 5–20 wt%, and reaction temperatures, 20–60 °C. The reaction system in the presence of Ac-β-CD preferentially yielded gels. The polymer composites were composed of connected particles with sizes of the order of 10⁻⁹ m. The particle sizes decreased with an increase in the CD concentration. Young’s moduli of the 3AZ-CD porous polymer composites tended to increase with an increase in bulk density. The 3AZ-CD porous polymer composites with Me-β-CD and HP-β-CD effectively adsorbed phenolphthalein in the solution. The adsorption value increased with increasing the CD content and rose to more than 600 mg/g of porous polymer composite. Full article

Heterocyclic aromatic amines (HAAs), known for their mutagenic and carcinogenic potential, are formed during the heating of protein-rich food items. Detecting HAAs swiftly and accurately poses challenges due to complex food matrices and low HAA concentrations. In this study, a simple and efficient magnetic solid-phase extraction (MSPE) strategy was developed for the simultaneous isolation and enrichment of three HAAs such as 2-amino-3,4,8-trimethylimidazo [4,5-f]quinoxaline (4,8-DiMeIQx), 2-amino-3,8-dimethylimidazo [4,5-f]quinoxaline (MeIQx), and 2-amino-3-methylimidazo [4,5-f]quinoline (IQ) in processed meats, employing the magnetic covalent organic framework Fe₃O₄@MOF-545-AMSA as an adsorbent. It was synthesized via a solvothermal method, with Fe₃O₄ as the magnetic core. Its building blocks are as follows: zirconium (Zr) as the coordination metal ion, tetrakis(4-carboxyphenyl)porphyrin and benzoic acid as organic ligands, and aminomethanesulfonic acid (AMSA). This composite captures targeted HAAs efficiently by exploiting the unique porous MOF-545-AMSA structure, specific metal–ligand coordination, and AMSA’s amino and sulfonic acid groups. The quantification of HAAs was achieved through the combination of Ultra-Performance Liquid Chromatography–Tandem Mass Spectrometry (UPLC-MS/MS) and MSPE, demonstrating satisfactory linearity (R² ≥ 0.9917), high recovery rates (83.7–111.0%), and low detection limits (0.1–1.0 μg/kg). Moreover, an automated high-throughput detection system was developed using MSPE to assess the presence of HAAs in meat products. Full article

The highly efficient removal of mercury metal ions at a higher pH (basic media) is barely reported in the literature. In this study, we developed a novel adsorbent by blending chitosan with guar gum, designed to effectively remove mercury ions from basic media by stabilizing them with a gold (Au³⁺) solution. The FTIR confirmed the compatibility of chitosan and guar gum through hydrogen bonding. The morphology of the blend exhibited an amorphous and porous structure. A mesoporous structure with a surface area, volume, and diameter of 11.843 (m²/g), 0.184 (cm²/g), and 17.072 nm, respectively, was confirmed by BET. The adsorption behavior was analyzed using isotherms and kinetics models, which best fitted with the pseudo-second-order kinetic model and Freundlich adsorption isotherm model, respectively. The adsorbent was shown to be an excellent candidate for the removal of mercury ions in water, with an adsorption efficiency of 92% at pH 12 in 60 min and a maximum adsorption capacity of 370.37 (mg/g). Full article

Microplastics (MPs) are ubiquitous in aquatic environments, soils, and beach sediments, demonstrating a remarkable ability to adsorb dissolved organic matter (DOM). Although there are methods for extracting DOM from water, the approaches for directly extracting DOM from microplastics have not been thoroughly investigated, and the characterization of DOM adsorbed on microplastics is also insufficient. In this study, five different types of microplastic samples were collected from each of five environmental media (water and sediment), and finally 25 samples were obtained. This paper comparatively assessed the extraction efficiency of DOM from MPs with various solvents by using total organic carbon (TOC), culminating in the development of a sodium pyrophosphate-NaOH solution extraction method optimized for DOM. The morphology, material and environmental medium of microplastics were the three primary factors affecting the adsorption of DOM on microplastics, with the highest enrichment ratio of 1.4–1.8 times for extruded polyethylene microplastics (EPE-MPs) characterized by their porous structure in the flowing water environment. The molecular weight of DOM adsorbed on microplastics showed a multi-modal distribution pattern with great dissimilarities among the different environmental media. Gel permeation chromatography (GPC) indicated that the weight-average molecular weight (M_w) of DOM was 2750–4552 Da for river MPs, 2760–5402 Da for Qiantang River MPs, 1233–5228 Da for East China Sea MPs, 440–7302 Da for soil sediment MPs and 438–6178 Da for beach sediment MPs, respectively. Excitation-emission matrix-parallel factor analysis (EEM-PARAFAC) identified that tyrosine-like substances with high excitation in region IV and low excitation in region I were predominantly adsorbed on MPs, followed by tryptophan-like substances with low excitation in region II and protein-like substances in region IV, while humic- and fulvic-like substances in regions V and III, respectively, exhibited the least adsorption affinity. The findings underscored the critical need to comprehensively consider the interactions between MPs and DOM and their environmental impacts in pollution control strategies. Full article

Superior selective adsorption of organic dye is still a big challenge in the process of dye wastewater treatment. Meanwhile, low-price and environmentally friendly biomass-based adsorbents show huge potential in the fields of separation and purification. In this study, we adopted the “hydrolysis–calcination method” to develop a novel in situ anchoring strategy for ultrasmall TiO_2−x on carbonized bacterial cellulose (CBC), which was derived from natural bacterial cellulose. Notably, 3D networks of porous CBC played a dual role for both providing hydrolytic sites and controlling the oxygen vacancies (V_o) of TiO_2−x. As for the single-dye adsorption, the TiO_2−x/CBC had a strong adsorption ability (101.4 mg/g) for removing methylene blue (MB), which was much higher than that of methyl orange (MO), malachite green (MG), rhodamine B (RhB), and tetracyclines (TC). Moreover, under the optimized carbonization temperature (T_c) of 300 °C, the TiO_2−x/CBC-300 exhibited an outstanding separation efficiency of 97.07% for the MB/MO solution. Detailed analysis confirmed that T_c was a key regulator for adjusting the V_o concentration, which directly influenced the surface charge density and, further, the separation efficiency of TiO_2−x/CBC. Additionally, the used adsorbent could be easily regenerated from washing by ethanol. After 4 regenerations, the adsorption efficiency declined only by 6.9% after 20 min and 13.6% after 120 min adsorption, respectively. Ultimately, this oxygen vacancy-rich TiO_2−x/BC system illuminated good prospects for mixed dye wastewater adsorption and separation. Full article

Activated carbon used to adsorb organic pollutants and heavy metals in wastewater is often used to prepare precursor materials to avoid re-polluting the environment. Non-precious metal and heteroatom co-doped electrocatalysts have emerged as promising alternatives to Pt-based catalysts due to their high catalytic activity and remarkable stability. This has greatly developed the ORR process in the field of energy storage, which is restricted due to the high price of Pt-based catalysts. In this study, bamboo shavings were pre-activated to synthesize carbon materials, which were subsequently mixed with an oil phase to simulate “waste-activated carbon”. The results demonstrate that the modified waste-activated carbon exhibits a high specific surface area, a well-developed porous structure, and characteristic element doping, which collectively contribute to the effective construction of active sites. Furthermore, the material displays ORR electrocatalytic performance that surpasses that of commercial Pt/C catalysts. In this study, a high-performance ORR electrocatalyst was successfully synthesized through the retreatment of “waste-activated carbon”. Building on this achievement, this study offers a novel perspective and contributes to advancing research on the resource utilization and sustainable treatment of waste-activated carbon. Full article

Polyphenols are organic molecules extracted from various fruits, such as coffee and citrus, that possess biological activity and antioxidant properties. However, the presence of polyphenols in the environment is hazardous to water quality and living health. Among a variety of water remediation methods, adsorption remains a staple in the field. Therefore, this work aims to develop porous polycaprolactone: poly(methyl methacrylate) (PCL:PMMA) membranes as a support for hydrotalcite immobilization for the removal of chlorogenic acid polyphenol (CGA) from aqueous solutions. Due to the hydrophilic nature of hydrotalcite, the adsorbent was functionalized with hexadecyltrimethylammonium bromide (CTAB) to increase its affinity for CGA, resulting in a removal efficiency of approximately 96%. Composite fiber membranes were prepared by solution-blowing spinning with specific amounts of hydrotalcite added (i.e., 1 to 60 wt%). A 3:1 PCL:PMMA blend resulted in superior mechanical traction (0.8 MPa) and stress deformation (70%) compared to pure PCL (0.7 MPa and 37%) and PMMA (0.1 MPa and 5%) fibers. PCL:PMMA membranes with 60% LDH-CTAB exhibited CGA removal rates equal to 55% in the first cycle while maintaining the capacity to remove 30% of the polyphenol after five consecutive reuses. Removal rates up to 90% could also be achieved with an appropriate adsorbent dose (2 g L⁻¹). Adsorption was found to follow pseudo-second-order kinetics and was adequately described by the Langmuir model, saturating LDH-CTAB active sites in four hours. PCL:PMMA:LDH-CTAB composites can be considered a potential alternative to support adsorbents for water remediation. Full article

Chitosan (CS) and polyvinyl alcohol (PVA) nanofiber membranes were synthesized via electrospinning and used as supporting materials for powdered porous organic polymer (POP). These membranes were then crosslinked with glutaraldehyde, resulting in nanofiber membranes (CS/PVA/POP) as an efficient adsorbent for Hg(II) ions. Characterization using Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy showed that the membranes effectively removed up to 92.9% of mercury ions at optimal conditions, with an adsorption capacity of 116.1 mg/g. The adsorption data fit well with the Langmuir isotherm and pseudo-second-order kinetic models. The efficient uptake of mercury ions was attributed to chemisorption involving active groups (C=S, -NH₂, -OH), facilitated by mechanisms such as chelation, complexation, or electron exchange. The CS/PVA/POP nanofiber membranes demonstrated significant advantages in adsorption capacity, economic viability, and recyclability, providing an effective solution to mercury pollution in water. Full article

In the context of global warming, technologies and studies aimed at mitigating carbon dioxide (CO₂) have become increasingly relevant. One such technology is CO₂ capture by activated and functionalized N-doped carbon from biomasses. This paper explores the ways to find the optimal CO₂ adsorption conditions, based on the carbonization temperature, impregnation rate, and preparation method, considering four different preparation routes in activated and functionalized carbon-N (PCs) of banana peel biomass residues. PCs were produced and chemically activated by K₂C₂O₄ and H₂O and functionalized by ethylenediamine (EDA). Carbon dioxide capture was investigated using functional density theory (DFT). Nitrogen (N) doping was confirmed by X-ray photoelectron spectroscopy (XPS), while the thermal characteristics were examined by thermogravimetric analysis (TGA). Surface morphology was examined by scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) detection, and surface functional groups were characterized using Fourier-transform infrared (FTIR) spectroscopy. In addition, the inorganic components were characterized by X-ray diffraction (XRD). The best performance of CO₂ adsorption of 1.69 mmol/g was achieved at 0 °C and 1 bar over the adsorbent synthesized at 600 °C with 60 min residence time, a 1:1 degree of impregnation, and a dry preparation method (single-stage preparation). This work presents as a great innovation the use of biomass as a raw material in the adsorption of the main greenhouse gases, using easy and accessible products. Full article

As a cost-effective sorbent, modified biochar has received increasing attention for the removal of heavy metal contaminants. Among several chemical modification methods, introducing thiol functional groups onto the surface of biochar has been identified as an effective enhancement approach for the heavy metal sorption and removal capacity of this porous adsorbent material. In general, chemical impregnation is a widely used method to graft thiol groups onto the surface of carbon-based materials. However, limited comparative data are available on the efficacy of the present biochar thiolation methods. In this study, the biochar of nine different organic sources was modified by two frequently used agents with distinct thiolation mechanisms: 3-Mercaptopropyltrimethoxysilane (3-MPTS) and β-mercaptoethanol. In addition to chemical impregnation, the ball milling method, a simple and environmentally friendly alternative thiolation method, was also evaluated. A comprehensive structural characterization of the biochar samples was completed before and after thiolation. A higher concentration of sulfur on the surface of the biochar was achieved through thiolation with β-mercaptoethanol, in which the thiolation mechanism is performed through an esterification reaction with the carboxylic acid functional groups of the activated biochar. Chemical impregnation was found to be a more effective thiolating method than ball milling using the same thiolating agent. Full article