Search Results (306)

Sorption and advanced oxidative processes (AOPs) are potential strategies for the removal of organic compounds, such as caffeine, from aqueous media. Such strategies tend to be more promising when combined with biopolymeric membranes as sorbents and photocatalyst supports. Therefore, the aim of the present study was to investigate sorption and AOP parameters in the performance of chitosan membranes and chitosan/TiO₂ composite membranes in individual and hybrid systems involving the photolysis, photocatalysis, and sorption of caffeine. Caffeine degradation by photolysis was 19.51 ± 1.14, 28.61 ± 0.05, and 30.64 ± 6.32%, whereas caffeine degradation by photocatalysis with catalytic membrane was 18.33 ± 2.20, 20.83 ± 1.49, and 31.41 ± 3.08% at pH 6, 7, and 8, respectively. In contrast, photocatalysis with the dispersed catalyst achieved degradation of 93.56 ± 2.12, 36.42 ± 2.59, and 31.41 ± 1.07% at pH 6, 7, and 8, respectively. These results indicate that ions present in the buffer solutions affect the net electrical charge on the surface of the composite biomaterial with the change in pH variation, occupying active sorption sites in the structure of the biomaterial, which was characterized by Fourier transform infrared spectrometry, thermogravimetric analysis, differential scanning thermogravimetry, and X-ray diffraction. Thus, it is verified that in a combined process of caffeine removal under UV irradiation and use of chitosan/TiO₂ composite membranes in phosphate-buffered medium, the photolysis mechanism is predominant, with little or no contribution from sorption, and that the TiO₂ catalyst promotes a significant reduction in the percentage of pollutant in the medium only when used dispersed and at low pH. Full article

This article presents the potential use of a humic agent called ‘Superhumate’, obtained from weathered coal from the Shubarkol deposit in Kazakhstan. The experiment was conducted using model solutions and surface mine water samples from the “Degelen” site at the Semipalatinsk Test Site. The adsorption of heavy metals and toxic elements using the “Superhumate” agent was carried out under dynamic conditions using a chromatographic column. Tests were conducted at a natural pH range of 5–8 (mine waters) and with a model solution at pH 1.7. Assessing the sorption efficiency of this preparation revealed that at pH 1.7, the agent does not adsorb elements such as Cd, Cu, Pb, and Zn. Under dynamic experimental conditions, using the preparation for mine waters at natural pH levels (pH 5–8), elements such as Be, Sr, Mo, Cd, Cs, Zn, and U were efficiently adsorbed at levels of 60–95%. The sorption efficiency of Pb ions was found to be almost independent of pH. The experimental results obtained with mine water samples indicate that alkaline solutions have the highest sorption efficiency, with pH ≥ 7, which is attributed to the solubility of the agent. Full article

Ethanol upgrading via catalytic C–C coupling, commonly known as the Guerbet reaction, offers a sustainable route to produce 1-butanol, a high-performance biofuel. To address gaps in the mechanistic understanding of the catalytic reaction, we investigated the process involving a fixed-bed reactor, operated at 275–325 °C, 21 bar, and weight hourly space velocities of 0.25–2.5 g_EtOH/(g_cat·h), using helium as a carrier gas, with a 5:1 He/EtOH molar ratio. The catalyst was a MgO–Al₂O₃ mixed oxide (Mg/Al = 2:1), derived from a hydrotalcite precursor. A detailed kinetic model was developed, encompassing 15 species and 27 reversible steps (10 sorption and 17 reaction steps), within a 1+1D sorption–reaction–transport framework. Four C₄-forming pathways were included: aldol condensation to form crotonaldehyde, semi-direct coupling to form butyraldehyde and crotyl alcohol, and direct coupling to form 1-butanol. To avoid overfitting, Arrhenius parameters were grouped by reaction type, resulting in sixty rate parameters and one active site-specific density parameter. The optimized model achieved high accuracy, with an average prediction error of 1.44 times the experimental standard deviation. The mechanistic analysis revealed aldol condensation as the dominant pathway below 335 °C, with semi-direct coupling to crotyl alcohol prevailing above 340 °C. The resulting model provides a robust framework for understanding and predicting complex reaction networks in ethanol upgrading systems. Full article

A VOC-contaminated shallow aquifer in an industrial site was investigated to evaluate its potential for natural attenuation. The shallow groundwater aquifer beneath the industrial site has been contaminated by dissolved volatile organic compounds (VOCs) such as trichloroethylene (TCE), cis-1,2-dichloroethylene (cis-DCE), and vinyl chloride (VC) for more than three decades. Monitoring and investigation were implemented during 2011–2024, aiming to propose future groundwater aquifer management strategies. This study included groundwater borehole investigation, well installation monitoring, hydraulic head measurements, slug tests, groundwater samplings, and microbial analyses. Microbial investigations identified the predominant group of microorganisms of Proteobacteria, indicating biodegradation potential, as demonstrated by the presence of cis-DCE and VC. BIOSCREEN was used to evaluate the process of natural attenuation, incorporating site-specific parameters. A two-layer groundwater flow model was developed using MODFLOW with hydraulic conductivities obtained from slug tests. The site has an average hydraulic head of 259.6 m amsl with a hydraulic gradient of 0.026, resulting in an average groundwater flow velocity of 11 m/y. Hydraulic conductivities were estimated during model calibration using the PEST pilot point technique. A reactive transport model, RT3D, was used to simulate dissolved TCE transport over 30 years, which can undergo sorption as well as biodegradation. Model calibration demonstrated a satisfactory fit between observed and simulated groundwater heads with a root mean square error of 0.08 m and a correlation coefficient (r) between measured and simulated heads of 0.81, confirming the validity of the hydraulic conductivity distribution. The TCE plume continuously degraded and gradually migrated southward, generating a cis-DCE plume. The concentrations in both plumes decreased toward the end of the simulation period at Source 1 (located upstream), while BIOSCREEN results confirmed ongoing natural attenuation primarily by biodegradation. The integrated MODFLOW-RT3D-BIOSCREEN approach effectively evaluated VOC attenuation and plume migration. However, future remediation strategies should consider enhanced bioremediation to accelerate contaminant degradation at Source 2 and ensure long-term groundwater quality. Full article

The occurrence of toxic metal(loid)s in surface freshwater is a global concern due to its impacts on human and ecosystem health. Conceptual and quantitative metal(loid) models are needed to assess the impact of metal(loid)s in watersheds affected by acid rock drainage. Few case studies have focused on arid and semiarid headwaters, with scarce hydrological and hydrochemical information. This work reports the use of WASP8 (US EPA) to model Al, Fe, As, Cu, and SO₄²⁻ concentrations in the Upper Elqui River watershed in north–central Chile. Calibrated model performance for total concentrations was “good” (25.9, RRMSE; 0.7, R²-d) to “very good” (0.8–0.9, R²-d). The dissolved concentrations ranged between “acceptable” (56.3, RRMSE), “good” (28.6, RRMSE; 0.7 d), and “very good” (0.9, R²-d). While the model validation achieved mainly “very good” (0.8–0.9, R²-d) predictions for total concentrations, the predicted dissolved concentrations were less accurate for all indicators. Sensitivity analysis showed that the partition coefficient is a sensitive constant for estimating dissolved concentrations, and that integrating sorption and sediment interaction reduces the model error. This work highlights the need for detailed and site-specific information on the reactive and hydrodynamic properties of suspended solids, which directly impact the partition coefficient, sedimentation, and resuspension velocity calibration. Full article

This study employs Density Functional Theory (DFT) and Molecular Dynamics (MD) simulations to investigate interactions between water molecules and Poly(N-isopropylacrylamide) (PNIPAM). DFT reveals preferential water binding sites, with enhanced binding energy observed in the linker zone. Quantum Theory of Atoms in Molecules (QTAIM) and electron localization function (ELF) analyses highlight the roles of hydrogen bonding and steric hindrance. MD simulations unveil temperature-dependent hydration dynamics, with structural transitions marked by changes in the radius of gyration (Rg) and the radial distribution function (RDF), aligning with DFT findings. Our work goes beyond prior studies by combining a DFT, QTAIM and MD simulations approach across different PNIPAM monomer-to-30mer structures. It introduces a systematic quantification of pseudo-saturation thresholds and explores water clustering dynamics with structural specificity, which have not been previously reported in the literature. These novel insights establish a more complete molecular-level picture of PNIPAM hydration behavior and temperature responsiveness, emphasizing the importance of amide hydrogen and carbonyl oxygen sites in hydrogen bonding, which weakens above the lower critical solution temperature (LCST), resulting in increased hydrophobicity and paving the way for understanding water sorption mechanisms, offering guidance for future applications such as dehumidification and atmospheric water harvesting. Full article

Creation of alkaline bulk layers from mining waste is economically viable way to prevent the migration of toxic metals down the soil profile and revegetate heavy polluted soils over large areas. We have conducted perennial experiments on the revegetation of industrial barren located near the operating nonferrous smelter in humid subarctic climate. A vermiculite–lizardite material from closed phlogopite mining, containing 10% layered silicates, was used to create the alkaline sorption barrier on the sites with high level of Cu/Ni pollution and wide range of topographic wetness index (TWI). We have revealed the strong effect of TWI on metal accumulation by mineral material with the highest effectiveness for the most wet sites. At the same time, the stable Ca and Mg content over seasons revealed the prolonged material effect for the maintenance of alkalinity and macronutrient supply. Further, we demonstrate the potential of Festuca rubra, Festuca ovina, Achillea millefolium, Deschampsia cespitosa, Dactylis glomerata, Rumex acetosella, Silene suecica, and for the revegetation of mineral material in dry locations. We demonstrated the effectiveness of alkaline geochemical barrier for the accumulation of toxic metals and successful plant growth in a wide range of topographic units. Full article

The Po Nagar Towers (Thap Ba) complex, an iconic heritage site of Cham culture and a nationally recognized special relic, has stood in Nhatrang, Vietnam, for over a thousand years. We report here a preliminary analysis of original ancient Cham bricks from the Po Nagar Towers using a combination of appropriate characterization techniques, including X-ray fluorescence (XRF), X-ray diffraction (XRD), Raman micro-spectroscopy, thermal dilatometry, compressive strength testing, and water sorption. Mechanical properties and firing temperatures of the ancient bricks have been determined to support the discussion on the likely technology used to make them. Specifically, they were made from clay, sand, plagioclases/feldspar, and grog mixed with intentionally added carbon precursor (charcoal powder), then fired at temperatures between 800 °C and 1000 °C to form lightweight bricks with a mass density of 1.3–1.6 kg/dm³ and an open porosity of 18–25%. The ancient Cham bricks have their texture and porosity to meet the requirements of the thin rubbing joint technique in tower construction and to contribute to the carvability and durability of Cham towers. A comparison is made with the bricks for tower restoration during the 2000s. Full article

Anaerobically digested liquid pig manure (LPM) is enriched with nutrients and thus can be used as an alternative nutrient source and substitute for chemical fertilizer (CF) in rice (Oryza sativa L.) farming. However, there are concerns regarding the contamination of the surrounding water due to the discharge of ponding water containing dissolved organic carbon (DOC), nitrogen (N), and phosphorus (P) from rice paddies fertilized using LPM. This study investigated the effects of the co-application of fly ash (FA) and zeolite (Z) amendments (FAZ amendments) on the concentration of DOC, N, and P in the ponding water of rice paddies fertilized with LPM at two different rates (standard (LPM_S) and double (LPM_D) at 11 and 22 g N m⁻², respectively). Rice was cultivated using four nutrient treatments, including no input, CF (11 g N m⁻²), LPM_S, and LPM_D, with or without FAZ amendments. When FAZ was not amended, LPM_S and LPM_D application increased the DOC concentration by 32% and 41%, respectively, compared to CF treatments (11 g N m⁻²), reflecting a high DOC concentration in LPM. The total N and P concentrations in the ponding water were lower in LPM_S treatment (by 5 and 8%, respectively) but higher (by 94% and 47%, respectively) in LPM_D treatment compared to CF treatments in the absence of FAZ, indicating a high potential for water pollution with a double LPM application rate. With a given nutrient treatment, FAZ amendments decreased DOC by 15–39%, supporting the immobilization of DOC by Z. FAZ consistently decreased the NH₄⁺ concentration by 6–51% across the nutrient treatments, likely via the sorption of NH₄⁺ onto the negatively charged sites of Z, but its effect on total N concentration was not consistent. Unexpectedly, total P concentration increased (by 77–167%) following the FAZ amendment. FAZ amendments tended to increase rice biomass and grain yield for LPM treatments, but these rice growth parameters were poor compared to CF regardless of FAZ amendment. Our results show that the application of LPM as a complete replacement for CF may hamper rice yield while increasing the likelihood of water pollution with DOC and P, although the co-application of FAZ may help to reduce rice yield loss and decrease DOC and NH₄⁺ concentrations. Full article

The interaction of microplastics (MPs) with organic micropollutants, such as antibiotics, facilitates their transport in aquatic environments, increasing mobility and toxicological risk. The diverse polymer types, sizes, and shapes in wastewater present a challenge in understanding the fate of persistent organic micropollutants. This study examines ceftazidime adsorption on five polymer types—polyethylene terephthalate (PET), polyethylene (PE), hard and soft polystyrene (PS), hard and soft polyurethane (PU), and tyre wear particles (TWPs, including three passenger tyres and one truck tyre) in various forms (fibres, beads, foam, and fragments) and sizes (10–1000 µm). MPs underwent weathering (alkaline hydrolysis, UVC-activated H₂O₂, and Xenon lamp irradiation) to simulate environmental conditions. Their physical and chemical changes were analysed through mass loss, carbonyl index, scanning electron microscopy, and atomic force microscopy. The adsorption values (mg g⁻¹) for pristine and weathered MPs, respectively, were as follows: PET (0.664 and 1.432), PE (0.210 and 0.234), hard PS (0.17 and 0.24), soft PS (0.53 and 0.48), hard PU (0.19), soft PU (0.17), and passenger TWPs—Bridgestone (0.212), Michelin (0.273), Goodyear (0.288), and Kumho truck TWPs (0.495). The highest and lowest adsorption were observed in weathered PET (1.432 mg g⁻¹) and pristine hard PS/soft PU (0.17 mg g⁻¹), respectively. Sorption kinetics and isothermal models showed that aged MPs exhibited higher sorption due to surface cracks, fragmentation, and increased adsorption sites. These findings enhance scientific knowledge of MP–antibiotic interactions in wastewater and can underpin studies to mitigate MP pollution and their adverse effects on the environment and humans. Full article

Irbesartan (IRB) is a commonly used BCS Class II antihypertensive drug requiring dissolving capacity enhancement to address oral bioavailability limitations. In this work, seven new IRB salts were successfully synthesized, including one carboxylate (IRB-MAL) and six sulfonate salts (IRB-TOSA, IRB-BSA, IRB-4-CBSA, IRB-2, 5-CBSA, IRB-MSA, and IRB-CPSA). Their vitro dissolution, intrinsic dissolution rates (IDRs), thermal/hygroscopic stability (via thermal analysis, dynamic vapor sorption, and accelerated stability tests), and phase transition process (monitored by in situ Raman spectroscopy) were evaluated. The results revealed that IRB-TOSA, IRB-MAL, IRB-BSA, IRB-4-CBSA, and IRB-MSA salts exhibited IDRs of 0.3194–0.7383 mg/(cm²·min), all significantly higher than IRB, with dissolution concentrations increased by 14.9–113.6%. IRB-TOSA and IRB-4-CBSA salts demonstrated excellent hydrothermal stability. Single crystal structure analysis confirmed proton transfer from coformers’ sulfonic/carboxylic acids (deprotonation site, H-out) to IRB’s diazaheterocycles (protonation site, H-in) in IRB salts. Six sulfonate salts exhibited N_H-in–H···O_H-out and N_non-H-in–H···O_H-out hydrogen bonds, with the former absent in IRB-MAL. Furthermore, supramolecular synthon studies revealed distinct hydrogen-bonding patterns (e.g., bifurcated bonds in 2,5-CBSA and CPSA salts) that correlate with moisture resistance. Quantitative analysis of IRB salts suggested hydrogen bond strengths may influence their melting points (decomposition temperatures). This study demonstrates that IRB salts hold promise for advanced pharmaceutical applications. Full article

Pollution of soil by heavy metals has become a critical environmental issue. This study investigated an innovative approach to heavy metals removal, focusing on the desorption of nickel and zinc from vermiculite using a combination of leaching and ultrasonic (US) irradiation at 20 or 362 kHz. When 0.1 M HCl was used as a washing solution, Zn²⁺ desorption yields around 85% were obtained in all conditions. Under 20 kHz US, fragmentation of the particles occurred, leading to the formation of new sites where released Zn²⁺ could sorb, allowing improved decontamination by cation exchange. Even higher yields were obtained with the biobased citric acid. Ni²⁺ desorption yields were lower due to its distribution in less accessible Tessier fractions. They significantly increased under US, especially at 362 kHz. It is shown that US leads to transfer of the contaminant from less accessible fractions (in particular the residual one) to more accessible ones, and that at low frequency, new sorption sites are created by fragmentation, leading to readsorption in the exchangeable fraction. This study brought to light for the first time the potential of high-frequency US in enhancing soil washing, to a higher extent compared to low-frequency (20–50 kHz) US. Full article

The evolution of coal’s pore structure is crucial to the efficient capture of carbon dioxide (CO₂) within coalbeds, as it provides both adsorption sites and seepage space for the adsorbed- and free-phase CO₂, respectively. However, the conventional single fractal method for characterizing pore structure fails to depict the intricacies and variations in coal pores. This study innovatively applies the low-temperature N₂/CO₂ sorption measurement and multifractal theory to investigate the evolution of the microporous structure of coals (e.g., from the Huainan coalfield) during the supercritical CO₂(ScCO₂)–water–rock interaction process. Firstly, we observed that the ScCO2–water–rock interaction does not significantly alter the coal’s pore morphology. Notably, taking the ZJ-8# sample as an example, low-temperature N₂ sorption testing displayed a stable pore volume following the reaction, accompanied by an increase in specific surface area. Within the CO₂ sorption testing range, the ZJ-8# sample’s pore volume remained unchanged, while the specific surface and pore width performed displayed a slight decrease. Secondly, by introducing key parameters from multifractal theory (such as D_q, α(q), τ(q), and f(α)), we assessed the heterogeneity characteristics of the coal’s pore structure before and after the ScCO2–water–rock reaction. The N₂ sorption analysis reveals an increase in pore heterogeneity for the ZJ-8# sample and a decrease for the GQ-13# sample within the sorption testing range. In the context of low-temperature CO₂ sorption analysis, the pore distribution complexity and heterogeneity of the GQ-11# and GQ-13# samples’ pores were escalated after ScCO2–water–rock interaction. The experimental and analysis results elucidated the dual roles of precipitation and dissolution exerted by the ScCO2–water–rock interaction on the micropores of coal reservoirs, underscoring the heterogeneous nature of the reaction’s influence on pore structures. The application of fractal theory offers a novel perspective compared to traditional pore characterization methods, significantly improving the precision and comprehensiveness of pore structure change descriptions. Full article

Crop residue returning to field inputs considerable nitrogen (N) into soils, which greatly influences the function and sustainability of the agricultural system. However, little is known about the transformation and physical stabilization of maize residue-derived N in soil matrix in response to changing N availability. To explore the distinct regulation of organo-mineral complexes on maize residue N translocation, a 38-week microcosm incubation was carried out amended with ¹⁵N-labeled maize residue in a Mollisols sampled from Gonghzuling, Northeast of China. Unlabeled inorganic N was added at different levels (0, 60.3 mg N kg⁻¹ soil (low level), 167 mg N kg⁻¹ soil (medium level), and 702 mg N kg⁻¹ soil (high level)). ¹⁵N enrichment in bulk soil and the separated particle size fractions were determined periodically in the bulk soils and the subsamples were analyzed. At the early stage of the incubation, the maize residue N concentration declined significantly in the sand fraction and increased in the silt and clay fractions. Temporally, the ¹⁵N enrichment in the silt fraction changed slightly after 4 weeks but that in the clay fraction increased continuously until the 18th week. These results indicated that the decomposing process controlled maize residue N translocation hierarchically from coarser into finer fractions. From the aspect of functional differentiation, the pass-in of the maize residue N into the silt fraction was apt to be balanced by the pass-out, while the absorption of clay particles was essential for the stabilization of the decomposed maize residue N. The inorganic N level critically controlled both the decomposition and translocation of maize residue in soil. High and medium inorganic N addition facilitated maize residue N decomposition compared to the low-level N addition. Furthermore, medium N availability is more favorable for maize residue N transportation and stabilization in the clay fraction. Comparatively, high-level inorganic N supply could possibly impede the interaction of maize residue N and clay minerals due to the competition of ammonium sorption/fixation on the active site of clay. This research highlighted the functional coupling of organic–inorganic N during soil N accumulation and stabilization, and such findings could present a theoretical perspective on optimal management of crop residue resources and chemical fertilizers in field practices. Full article

Microplastic (MP) contamination in soil is an emerging environmental concern, influencing the mobility and bioavailability of heavy metals (HMs). This study investigates how different MP types (PP, PS, PVC, HDPE, LDPE, PES, and PET-Glitter) affect HM behavior in soil, focusing on sorption/desorption, and the extraction efficiency of Pb, Cu, Co, Ni, Cr, and Cd. Soil samples incubated with MPs showed significant pH increases, particularly with PES and HDPE at 0.8 and 0.6 pH units, respectively. The extraction experiments using 0.05 M EDTA and 0.01 M CaCl₂ revealed that MPs altered metal bioavailability—with HDPE reducing Pb mobility by 15%—and increased Cd and Co mobility by 10–20%. The batch sorption tests confirmed higher Pb adsorption onto HDPE but decreased Cd and Co sorption compared to control soils without MP. These findings demonstrate that MPs act as additional sorption sites, modifying metal speciation and availability, which has critical implications for soil health, agricultural sustainability, and remediation strategies. However, results may vary based on soil type, MP aging, and environmental conditions, indicating the need for further long-term field studies. This research provides valuable insights into the complex interactions between MPs, heavy metals, and soil systems, contributing to a better understanding of pollution dynamics and risk assessment in contaminated environments. Full article