Search Results (1,335)

A comprehensive study was conducted to determine the suitability of biochar produced from agricultural waste in the form of alfalfa (BL₅₀₀) and corn (BC₅₀₀) for methylene blue (MB) adsorption. As part of the research, biochar was produced at 500 °C by pyrolysis using a CO₂ atmosphere. BL₅₀₀ and BC₅₀₀ biochar were characterised in terms of their physicochemical and structural properties using FTIR spectroscopy, Raman spectroscopy, and N₂ adsorption–desorption. The produced biochars are characterised by a significant ash content and high carbon content. They have a specific surface area of 4.12 m²/g (BL₅₀₀) and 19.84 m²/g (BC₅₀₀), a micro-mesoporous structure and are rich in functional groups (including OH, COOH, CO). BL₅₀₀ biochar showed greater effectiveness in removing methylene blue (MB) than BC500, with maximum sorption capacities of 39.94 mg/g and 19.47 mg/g, respectively. Furthermore, kinetic model fitting indicated that the adsorption process follows a pseudo-second-order model and a Langmuir monolayer model. However, the intramolecular diffusion model (IPD) and Bangham models confirmed that the adsorption process does not occur in a single stage. The produced biochar can be used as a sustainable adsorbent for MB from aqueous solutions. Full article

In this study, biocarbon adsorbents were obtained from fennel and caraway seeds through microwave-assisted chemical activation with sodium carbonate. The activation process involved carbonizing the raw material at 300 °C for 30 min., followed by impregnation with sodium carbonate at a precursor-to-activator mass ratio of 1:2. Activation was performed at two distinct temperatures—500 °C and 600 °C—with an activation time of 15 min. The structural, textural, and surface chemical characteristics of the obtained biocarbons were investigated using complementary analytical techniques, including low-temperature nitrogen adsorption–desorption isotherms, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), X-ray diffraction (XRD), Boehm titration, and pH analysis of aqueous extracts. The resulting adsorbents demonstrated low development of specific surface area (109–154 m²/g) and limited sorption capacity for methylene blue (20–32 mg/g). Adsorption experiments indicated that the Freundlich isotherm model most accurately described the data, suggesting multilayer adsorption on heterogeneous surfaces. Thermodynamic evaluations showed the adsorption to be both spontaneous and endothermic. The adsorption mechanism is primarily governed by electrostatic interactions between the cationic dye and surface functional groups, π–π interactions with the carbon structure, and diffusion within mesopores. This study provides a comparative evaluation of microwave-assisted Na₂CO₃ activation of fennel and caraway seed waste and assesses the potential of these biochars for dye removal from aqueous solutions. Full article

The presence of antibiotics in aquatic systems presents significant ecological and health risks. Herein, Fe₃O₄/MgAl₂O₄ (MgFeAl-1), 2.5%NiO@Fe₃O₄/MgAl₂O₄ (MgFeAl-2), 5%NiO@Fe₃O₄/MgAl₂O₄ (MgFeAl-3), and 10%NiO@Fe₃O₄/MgAl₂O₄ (MgFeAl-4) were synthesized, selecting glucose as a capping agent, and 600 °C as calcination temperature. The TEM, EDX, BET, XRD, and FTIR techniques were employed to characterize the preidentified sorbents. The average size of MgFeAl-1, MgFeAl-2, MgFeAl-3, and MgFeAl-4 was about 6.53, 5.0, 7.61, and 10.52 nm, respectively, and they exhibited surface areas of 114.15, 154.02, 153.36, and 128.54 m² g⁻¹, respectively. The sorbents were tested for the removal of ciprofloxacin (CFCN) from aqueous solutions using the batch protocol. The MgFeAl-2 exhibited the highest performance, achieving an adsorption capacity of 99.45 mg g⁻¹, and the sorption equilibrium was reached within 60 min. The pseudo-second-order model best described CFCN sorption onto MgFeAl-2, and liquid-film diffusion influenced CFCN sorption. The CFCN adsorption onto MgFeAl-2 was well represented by the Langmuir isotherm model (R² = 0.93), indicating a monolayer adsorption. The thermodynamic results indicated a spontaneous, endothermic sorption process. A four-cycle MgFeAl-2 reusability study showed an average efficiency of 90%. Notably, MgFeAl-2 was effective in treating natural-water matrices, with a slight reduction in seawater due to ionic interference. The findings highlight the potential of MgFeAl-2 as an affordable and reusable adsorbent for removing antibiotics from contaminated water. Full article

Ordered mesoporous silica (OMS) is widely investigated as a mineral carrier for bioactive compounds; however, the adsorption of poorly soluble flavonoids such as quercetin on unmodified silica remains limited, and the effect of cationic surfactant modification on adsorption performance is still insufficiently understood. This study evaluates the adsorption of quercetin on OMS modified with tetrabutylammonium bromide (TBA-Br) and hexadecyltrimethylammonium bromide (HDTMA-Br). Batch adsorption experiments were analyzed using various adsorption isotherm models, and the quality of fit was evaluated based on the coefficient of determination (R²) and the reduced chi-square statistic (χ²/DoF). The results indicated that quercetin adsorption followed a physisorption mechanism, predominantly governed by hydrophobic interactions and surface heterogeneity. Silica modified with HDTMA-Br exhibited a significantly higher maximum sorption capacity compared to OMS-TBA-Br, reaching g_max values of up to 5.2 mg·g⁻¹, whereas the maximum adsorption for OMS-TBA-Br did not exceed 4.2 mg·g⁻¹. The best fit of the experimental data was obtained for models accounting for the heterogeneous nature of the adsorbent surface, particularly the Tóth model. The obtained results clearly demonstrate that modification of OMS with a cationic surfactant possessing a long alkyl chain significantly enhances the adsorption capacity of silica toward quercetin, which is of considerable importance for the design of mineral carriers for bioactive compounds. Full article

Per- and Polyfluoroalkyl substances (PFASs) are commonly detected in airport stormwater runoff due to historical and ongoing use of aqueous film-forming foams (AFFFs). Conventional stormwater control measures (SCMs) are generally effective at removing PFASs associated with the particulate fraction, but may provide limited removal of dissolved-phase PFASs. Sorbent polishing beds represent a potential downstream treatment option; however, their applicability and performance for PFASs in stormwater have not been well studied. In this study, measured PFAS concentrations and runoff volumes from an AFFF-affected airport apron were combined with literature-derived sorption parameters to develop a screening-level framework for evaluating adsorber beds as polishing units for SCM effluent. Bed sizing was calculated using a representative empty bed contact time (EBCT) of 10 min and a design volume based on the 85th percentile storm event. Sorbent performance was evaluated using literature equilibrium partition coefficients (K_d) for activated carbons, ion exchange resins, and specialty materials to estimate operational lifetimes prior to regeneration or replacement. Model-based results indicated lifetimes ranging from approximately 7 years for activated carbon to more than 50 years for specialty materials, depending on PFAS chain length and affinity. Sensitivity analysis using quartile K_d ranges showed predicted lifetimes spanning orders of magnitude, emphasizing the screening-level nature of the estimates. This work links field monitoring data with conceptual adsorber design to support early-stage evaluation of sorbent polishing strategies for airport runoff management, supporting compliance under tightening discharge regulations. Full article

While advanced imaging techniques and ordered porous materials like MOFs have gained prominence, gas sorption remains the indispensable tool for characterizing the multiscale heterogeneity of industrially important disordered solids, such as catalysts and shales. This review examines recent developments in gas sorption methodologies specifically tailored for rigid, disordered porous media. We discuss experimental advances, including the choice of adsorbate and the utility of the overcondensation method for probing macroporosity and ensuring saturation. Furthermore, we critically evaluate theoretical approaches for determining pore size distributions (PSDs), contrasting classical methods with Density Functional Theory (DFT) and Grand Canonical Monte Carlo (GCMC) simulations. Special emphasis is placed on the impact of pore-to-pore cooperative effects, such as advanced condensation, cavitation, and pore-blocking, on the interpretation of sorption isotherms. We highlight how complementary techniques, including integrated mercury porosimetry, NMR, and computerized X-ray tomography (CXT), are essential for deconvolving these complex network effects and validating void space descriptors. We conclude that, while “brute force” molecular simulations on image-based reconstructions are progressing, “minimalist” pore network models, which incorporate cooperative mechanisms, currently offer the most empirically adequate approach. Ultimately, gas sorption remains unique in its ability to statistically characterize void spaces from Angstroms to millimeters in a single experiment. Full article

Yellow pitaya (Selenicereus megalanthus) pulp is rich in phenolic compounds with antioxidant capacity and exhibits desirable sensory properties. Dehydration and grinding into powder may enhance stability and broaden the potential for export and industrial applications. In this study, freeze-drying was used to obtain yellow pitaya pulp powder, which was stored at 20 °C under different water activity levels (a_w 0.113–0.750). Changes in physical properties (water sorption, glass transition, texture, and color) and bioactive compounds (antioxidant capacity and phenolic content) were assessed after 3 months of storage. Combining the Gordon & Taylor model with the GAB sorption isotherm, the critical water content (CWC) and water activity (CWA) related to glass transition were determined as 0.023 g water/g product and 0.110, respectively. Below these critical values, the glassy state of pitaya pulp powder was maintained, enhancing its quality and stability during storage. The greatest changes in color and bioactive compound content were observed at high a_w levels (0.680 and 0.750, respectively). Due to its high nutritional value and antioxidant properties, this powder can be incorporated into formulations or dietary supplements, offering additional functional benefits and expanding its application in the food industry. Full article

Polycyclic aromatic hydrocarbons (PAHs) can enter water bodies and bioaccumulate in fish, leading to biomagnification; therefore, their monitoring is necessary. Passive sampling is easy to handle and shows potential for this purpose. However, studies in vivo are scarce, and kinetic parameters governing analyte partitioning between tissue and samplers remain poorly characterized. In this study, the silicone rubber membranes (SRMs) were exposed to fish fillet from common carp (Cyprinus carpio) to determine bioaccumulation parameters based on dissipation modelling using performance reference compounds (PRCs). The SRM was implanted in vivo in fish, and the dissipated PRCs were measured and applied to a mono-compartmental model. The results in fish fillet showed a pseudo-first kinetic order, and the plateau was attained at a time > 30 h. However, the equilibrium may not be ensured because of the low lipid fraction (fl) in fish (4.5%), which could lead to a local saturation of the tissue in contact with the SRM. The ratio between elimination and uptake constants (K_e/K_u) showed faster PAHs–SRM sorption than PAHs-fish tissue sorption (200 times); thus, fish with low fl will lead to faster SRM sorption. By contrast, in fish with higher fl, the long-term exposures will be necessary. The percentage of released deuterated PAHs from SRM during in vivo fish exposure was 1.6 times higher than that observed in the fish fillet, indicating an active clearance process. Therefore, during implantation, the rate of clearance and the fl should be considered to ensure detectable levels for applying the integrative equation based on dissipation modelling. Full article

The selective removal of radioactive cesium-137 and strontium-90 from high-salinity radioactive wastewater remains a critical challenge, as competing ions reduce adsorption efficiency and selectivity. In this study, high-performance granulated adsorbents were developed based on alkali-activated geopolymer matrices to enhance sorption performance. The adsorbents were synthesized by inorganic polymerization, and mechanically robust granules with controlled porosity and surface chemistry were obtained. Batch sorption experiments conducted in simulated seawater demonstrated greater than 99% removal efficiencies for cesium and strontium. Isotherm modeling confirmed high maximum sorption capacities (up to 0.41 meq/g for Cs⁺ and 5.07 meq/g for Sr²⁺). Continuous fixed-bed column tests demonstrated sustained removal efficiencies for the optimized adsorbents. Structural analyses, including scanning electron microscopy, energy-dispersive X-ray spectroscopy mapping, and X-ray diffraction, confirmed uniform elemental distribution and crystalline phases consistent with selective sorption mechanisms. Assessment of mechanical strength revealed sufficient compressive strengths to ensure operational durability under hydraulic stress. These findings demonstrate that the synthesized geopolymer-based granules are a potentially effective and versatile solution for the comprehensive treatment of radioactive wastewater. Full article

The convergence of global plastic pollution and antimicrobial resistance crises has intensified concerns about the role of microplastics (MPs) in disseminating antibiotic resistance genes (ARGs) in marine environments. This review synthesizes the mechanistic pathways through which MPs act as vectors for ARG propagation, supported by a bibliometric analysis of 144 studies retrieved from Scopus. MPs possess distinct physicochemical properties such as nanoplastic formation, polymer-specific sorption, weathering-induced oxidation, and additive leachate release that facilitate microbial colonization and biofilm formation. These plastisphere biofilms, enriched with mobile genetic elements including integrons, transposons, and plasmids, promote ARG transfer via conjugation, transformation, and transduction. Environmental modulators like salinity, oxygen, nutrients, pH, UV exposure, and reactive oxygen species further accelerate horizontal gene transfer, while co-selection pressures from heavy metals and antibiotics amplify resistance dissemination. Bibliometric mapping reveals a sharp rise in publications since 2018, with China leading contributions and major research themes centered on horizontal gene transfer, metagenomics, nanoplastics, and biofilm-mediated resistome evolution. Overall, marine MPs substantially intensify ARG spread through complex microbe–plastic–pollutant interactions, posing significant ecological and public health risks. Addressing current gaps, such as limited field validation, underexplored nanoplastic mechanisms, geographic bias, and lack of standardized monitoring, requires harmonized surveillance, omics integration, pollutant mixture modeling, and One Health-based risk assessment to inform global policy interventions. Full article

This study evaluates the impact of a comprehensive design integrating precursor type, reduction and freeze-casting on the development of aerogels with high sorption capacity for engine oil. In this respect, the graphene oxide was varied from commercial to expanded; the reduction approach relied either on purely hydrothermal or combined hydrothermal–chemical reduction approaches. Following the synthesis, freeze-casting was applied at −5 °C and −196 °C. To further improve the reduction degree, annealing in an inert atmosphere was employed upon drying. The effects of precursors, reduction approach, freeze-casting and annealing were systematically investigated. Characterization techniques, including FT-IR, Raman spectroscopy, SEM, and EDS, were used to correlate the degree of reduction and morphological features of the porous structure with the absorption properties. The use of expanded GO as a precursor yielded aerogels with more homogeneous three-dimensional networks, a reduced bulk density of 3 mg cm⁻³, and lower oxygen-containing functional group content, thereby achieving consistently superior oil absorption of 270 g g⁻¹, with an oil occupancy of 94%. The process was found to fit well with the pseudo-first-order kinetic model. The results demonstrate that a comprehensive approach—considering combined reduction, freeze-casting, and thermal annealing—enables the tailored optimization of both the structure and absorption performance of GO aerogels for the remediation of oil spills. Full article

The Santiago River near the Guadalajara Metropolitan Area is one of the most contaminated water bodies in Mexico, where heavy metals pose a major threat to aquatic ecosystems. Chronic metal pollution has promoted the adaptation of native microbial communities, including the production of metal-chelating metabolites such as siderophores, which represent a valuable resource for remediation-oriented biomaterials. In this study, bacterial strains were isolated from water and sediment samples, then screened for siderophore production using the Chrome Azurol S assay (CAS), complemented by a MATLAB-based image processing approach for semi-quantitative ranking prior to taxonomic identification by MALDI-TOF MS. Based on biosafety considerations and cultivation robustness, Bacillus thuringiensis was selected as a benchmark case, being immobilized onto activated carbon to produce a carbon–bacteria biocomposite (CBM). To evaluate the performance of CBM, Cu(II) was used as a model contaminant due to its industrial relevance, persistence, toxicity, and strong complexation behavior. Batch adsorption experiments showed that the CBM exhibited a 23.9% higher maximum Cu(II) sorption capacity than pristine activated carbon. Acute toxicity assays using Vibrio fischeri further indicated reduced toxicity in CBM-treated effluents, supporting the feasibility of this contained biocomposite for heavy metal remediation. Full article

The growing interest in sustainable and structurally diverse sorbent materials has intensified the search for effective biosorbents that can complement or replace conventional adsorbents. This work presents the potential use of Chlorella vulgaris dried biomass and its modifications (ultrasound-treated, lipid-extracted, and combined forms) for diclofenac (DCF) sorption from aqueous solutions. It was demonstrated that sorption efficiency significantly depends on the solution’s pH. Lowering the pH from 6 to 2 increases the sorption from 5% to 68%, while 99% desorption occurred at pH 9. The adsorption isotherms for intact biomass and after lipid extraction (CV-E2) are best described by the Langmuir and Freundlich models; for ultrasonically treated biomass (CV-E1) by the Temkin model; and for ultrasound-assisted solvent extraction (CV-E3) by the Dubinin–Radushkevich model. These findings demonstrate that cellular lipids and particle characteristics critically govern sorption mechanisms, highlighting dried Chlorella biomass as a structurally and chemically tunable biosorbent. Importantly, the key sorption experiments were performed under strongly acidic conditions (pH 2), which differ from typical wastewater or surface water matrices. Therefore, the presented results should be regarded as a proof of concept illustrating the mechanistic potential of dried Chlorella biomass as a tunable sorptive material, with prospective relevance for separation science and laboratory-scale analytical applications rather than direct environmental remediation. Full article

A simple method employing dextrose as a capping agent was adopted for making MgAl₂O₄@MgO (AM), 5%NiO-MgAl₂O₄@MgO (AMNi), 5%CoO-MgAl₂O₄@MgO (AMCo), and 5%CuO-MgAl₂O₄@MgO (AMCu) nanocomposites. The average particle sizes, determined via SEM, were in the range of 21.6–51.4 nm, 9.8–13.8 nm, 19.1–32.2 nm, and 9.2–31.2 nm for AM, AMCu, AMNi, and AMCo, respectively. The nanosorbents exhibited type IV isotherm curves and type H3 hysteresis loops, signifying mesoporous properties. The AM, AMCu, AMNi, and AMCo exhibited surface areas of 69.47, 95.87, 86.23, and 75.87 m²/g, respectively. The pseudo second order described the indigo carmine (IDC) sorptions onto AM, AMCu, AMNi, and AMCo. The liquid film diffusion regulated IDC sorption on AMNi and AMCo, whereas the intraparticle diffusion was the dominant model on AM and AMCu. The AMCu’s showed a q_t value of 127 mg g⁻¹ from a 50 mg L⁻¹ IDC solution at 20 °C, and 286.2 mg g⁻¹ from a 200 mg L⁻¹ IDC solution at 50 °C, establishing its capability for treating contaminated water. The IDC sorption onto AMCu aligns with the Freundlich model, which may elucidate the elevated q_t value of AMCu. Elevating the temperature induced the IDC sorption on AMCu, indicating its endothermic nature, and the negative ΔG° implied that the IDC sorption by AMCu was spontaneous. A 5.0 and 10.0 mg L⁻¹ IDC concentration in natural water samples was treated by the AMCu, which showed 100.0% efficacy for both groundwater samples; however, its efficacy toward the 5 and 10 mg L⁻¹ IDC in seawater was 99.23% and 89.78%, respectively. The MACu’s efficiency throughout four reuse cycles decreased by only 7.21%, demonstrating excellent stability and reusability performance. Full article

Hydrogen-based energy systems require large amounts of high-purity water, motivating thermally driven desalination that can recover low-grade heat. This study evaluates a silica gel–water adsorption chiller–desalination unit as a coupled source of cooling and pre-treated water for electrolysers. A laboratory two-bed system was tested on saline feed using 300 s valve-switching periods at an 80 °C driving temperature and 20–30 °C cooling water. Dynamic vapour sorption measurements provided Dubinin–Astakhov equilibrium and linear driving force kinetic parameters, implemented in a CFD porous bed model via user-defined source terms. Experiments yielded COP values of 0.29–0.41, an SCP of 165 W·kg⁻¹ of adsorbent, and an average distillate production of 1.68–1.82 kg·h⁻¹, while distillate conductivity remained ≈2.3 μS·cm⁻¹. The model reproduced the mean condensate production with a ≈6% underprediction. It was then used to compare six alternative fin geometries with a constant heat-transfer area. Fin-shape modifications changed inter-fin heating by <2 K and cumulative desorbed mass by <0.05%, indicating limited sensitivity to subtle local refinements. Performance gains are more likely to arise from operating conditions and exchanger-scale architecture than from minor fin-shape changes. Full article