Search Results (3,671)

The increasing discharge of pharmaceutical contaminants, particularly antibiotics like metronidazole (MNZ), into water systems poses significant ecological and public health risks due to their high solubility and low biodegradability. This study developed and characterized a highly porous activated carbon derived from maize cob (MC-AC). The synthesized material was characterized using FTIR, FESEM, PXRD, HRTEM, and BET analysis. Batch adsorption experiments were conducted, and the removal efficiency of MC-AC for MNZ was 98.6%. Optimization and modeling of the process variables of pH (3–11), contact time (0–75 min), concentration (0–70 mg/L), temperature (25–35 °C), and adsorbent dosage (0.5–1.5 g/L) were investigated using the Box–Behnken design (BBD) of response surface methodology, and 29 runs were obtained. The BBD model determined an optimal removal efficiency of 94.6 for metronidazole. Furthermore, non-linearized kinetic and isotherm models were used to determine the adsorption mechanism and mode of metronidazole from water. From the investigation, it was observed that both the Freundlich and pseudo-second-order models exhibited high correlation coefficients. The models with the best performance and low error metrics were determined by R², MSE, RMSE, SAE, and SSE. Therefore, the adsorption mode was multilayer heterogeneous, and the mechanism was chemisorption. Therefore, this study provides a unique alternative for using the Box–Behnken design, kinetic, and isotherm models to understand the removal of metronidazole from water using maize cob-activated carbon. Full article

The Jinjia oilfield in Shengli oilfield is a typical ultra-sensitive reservoir characterized by high crude oil viscosity, poor fluidity, high clay content, and weak cementation. During development, oil-sand mixtures readily plug pore throats. Various development methods including water flooding and thermal recovery have been implemented, yet severe problems persist: inability to inject, failure to displace, and lack of capacity to produce. To address these challenges, a functional microbial mineral-modified desensitization-chemical viscosity-reduction dual-effect agent, a self-growing gel dispersion profile control agent, and a low-damage deep acidizing system were developed. Laboratory experiments clarified the enhanced oil recovery mechanism of the bio-chemical desensitization and viscosity-reduction system. Results indicate that the desensitization and viscosity-reduction system can inhibit clay swelling, with the anti-swelling improvement rate of core permeability reaching 56%. Chemical viscosity reduction enabled heavy oil to “flow effectively,” achieving a viscosity reduction rate of 98.9% after adsorption. The profile control agent dispersed and migrated, then stably adsorbed onto particle surfaces to plug high-permeability channels, demonstrating strong anti-scouring capability and effectively suppressing channeling flow. In the composite system, bio-chemical desensitization and viscosity reduction synergistically enhanced mobility control, achieving an oil recovery factor of 56.5%, representing a 26.3% increase over post-water-flooding viscosity-reduction flooding. After two pilot well groups in the Jinjia oilfield were converted from water flooding to bio-chemical desensitization and viscosity-reduction composite flooding, single-well oil production capacity increased by 2.8-fold, water cut decreased by 12%, and both development performance and economic benefits were significantly improved—transforming the situation from “increasing water without increasing oil” to “increasing both liquid and oil production.” The research findings provide important reference value for the effective development of ultra-sensitive reservoirs. Full article

Agricultural waste-derived biochars have recently attracted increasing attention as sustainable adsorbents for wastewater treatment. In this study, biochars (BHBs) produced from buckwheat husks at 500, 600, and 700 °C were investigated as novel adsorbents for the removal of the cationic dyes Crystal Violet (CV) and Rhodamine B (RhB) from aqueous solutions. The obtained materials were characterized using thermogravimetric analysis and surface functional group analysis to evaluate the influence of pyrolysis temperature on their physicochemical properties. The effects of initial adsorbent dose, solution pH, and ionic strength were assessed, while adsorption kinetics and equilibrium isotherms were analyzed to elucidate the adsorption mechanisms. It was found that the adsorption of both dyes depended on pH. CV adsorption was lowest in an acidic environment and increased with increasing pH from 3 to 9. RhB was most effectively adsorbed in an acidic environment. Its adsorption decreased as the pH increased from 3 to around 5, after which it stabilized. The adsorption of CV decreased with increasing ionic strength of the solution, whereas the adsorption efficiency of RhB remained unaffected. The adsorption kinetics of CV and RhB on BHBs were found to follow a pseudo-second-order mechanism controlled by film diffusion. The Langmuir, Freundlich, and Temkin models all provided good fits to the equilibrium experiments. The adsorption capacities of BHBs for CV and RhB decreased with increasing pyrolysis temperature and surface alkalinity of the biochars (BHB700 < BHB600 < BHB500). The adsorption capacities of biochars ranged from 41.00 mg/g (BHB700) to 56.10 mg/g (BHB500) for CV and from 9.74 mg/g (BHB700) to 13.24 mg/g (BHB500) for RhB. The study highlights the potential of buckwheat husk-derived biochars as sustainable adsorbents for the treatment of dye-contaminated wastewater and provides insight into the relationship between pyrolysis conditions and adsorption performance. Full article

Per- and polyfluoroalkyl substances (PFAS), and the short-chain representative perfluorohexanoic acid (PFHxA), are persistent environmental pollutants that pose serious health risks due to their resistance to degradation, mobility, and widespread presence in aquatic systems. This study investigates the adsorption of PFHxA onto graphene-based materials synthesised from graphite using a scalable, resource-efficient route and compares their performance with three commercial reduced graphene oxides. The graphene samples were characterised by BET surface area analysis, SEM, XPS, and Raman spectroscopy, revealing significant differences in surface area, pore volume, and surface chemistry that govern adsorption behaviour. Batch adsorption experiments in different water matrices (tap water, river water, and treated wastewater) under controlled pH conditions showed that graphene materials with higher surface area and optimised oxygen-containing functional groups achieved enhanced PFHxA removal, even in complex, real-world waters. Based on the physicochemical properties of both the adsorbent and adsorbate, hydrophobic interactions may contribute to adsorption alongside pore-filling effects, hydrogen bonding, and other intermolecular forces. Among the tested sorbents, the SG-X material, with its high BET surface area and hydrophobic character, and the CG-A material, which retained high performance across a broad pH range, exhibited the most promising adsorption capacities and operational robustness. These findings demonstrate the potential of engineered graphene-based adsorbents as a sustainable remediation option for short-chain PFASs, supporting circular and low-chemical-intensity approaches to protecting water quality under diverse environmental conditions. Full article

Landfill wastewater is a serious environmental problem and represents a high-concentration source of valuable organic compounds such as humic acids (HAs). The nanofiltration (NF) concentrate generated during treatment poses an even more significant environmental challenge, and the recovery of these substances is compatible with circular economy principles but requires innovative, pollution-resistant separation technologies. This study presents a novel hybrid approach for HA recovery by integrating naturally occurring clay minerals, such as halloysite nanotubes (HNTs), as a dynamic coating layer onto tube-shaped ceramic ultrafiltration membranes. The research was conducted in two stages: batch adsorption–desorption experiments followed by membrane integration. In the first stage, the batch adsorption studies showed that HA adsorption by HNTs followed the Freundlich isotherm model. The maximum HA adsorption capacity for HNTs increased with increasing initial concentration. In desorption studies, recovery rates of 74.6% were achieved with 1.5 N sodium hydroxide (NaOH) and 67.5% with 1.5 N potassium hydroxide (KOH). In membrane studies, the optimum HNT coating concentration was determined as 0.05 g/L. While an average removal efficiency of 85.3% was obtained in synthetic HA filtration, the desorption efficiency after regeneration was around 35–37%. In experiments with real NF concentrate, HA removal efficiencies ranged from 19 to 64% for concentrations of 5, 10, and 20 mg/L, with the highest desorption efficiency (59.3%) obtained in the 10 mg/L NF concentrate. The results reveal that the complex structure and competing components in the real wastewater matrix limit the removal and recovery performance compared to synthetic solutions. Full article

Almond processing byproducts are rich in bioactive polyphenols but severely underutilized due to inefficient conventional extraction methods. This study presents the first systematic optimization of an integrated ultrasound-assisted enzymatic extraction and AB-8 macroporous resin purification process for almond hull polyphenols, addressing the limitations of low yield, high impurity content, and bioactivity loss in traditional approaches. Extraction parameters were optimized via single-factor experiments combined with Box–Behnken response surface methodology, while purification conditions were refined through static and dynamic adsorption–desorption tests. Structural characterization and antioxidant evaluation were performed using Ultraviolet-Visible Spectroscopy (UV-Vis), Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and Ferric Reducing Antioxidant Power (FRAP) assays. Under optimal conditions, the polyphenol yield reached 23.67 mg/g. After purification, polyphenol purity increased 5.88-fold, flavonoid purity improved 4.62-fold, and DPPH/FRAP antioxidant activities were enhanced 5.0-fold and 6.5-fold, respectively. Purified polyphenols retained intact phenolic structures and exhibited a loose porous microstructure. This green process provides a technical basis for high-value utilization of almond hulls. Limitations include lack of polyphenol monomer identification, in vivo efficacy validation and industrial economic feasibility assessment. Full article

Toxic metal contamination in aquatic systems commonly occurs as multicomponent mixtures, making competitive adsorption assessment essential for realistic adsorbent evaluation. This study investigated corn stalk-derived hydrochar functionalized with Mg-Fe layered double hydroxide (Mg–Fe-LDH@HC) for simultaneous Cd(II) and Zn(II) adsorption in aqueous bicomponent systems. The material was evaluated through pH and dosage optimization, kinetic assays, bicomponent equilibrium modeling, thermodynamic assessment, mixture-design experiments, regeneration tests, and applicability assays with interfering ions and real water matrices. Under the selected conditions, pH 6.75, 4 g L⁻¹ Mg–Fe-LDH@HC, 1 mM equimolar Cd(II)/Zn(II), 298.15 K, and 180 min, near-complete removal of both metals was achieved. Kinetic analysis showed rapid initial uptake followed by a slower approach to equilibrium. Bangham, Elovich, and Weber-Morris analyses supported a multistage adsorption process involving external surface uptake, diffusion-related resistance, and heterogeneous surface interactions, although intraparticle diffusion was not the sole rate-controlling step. Bicomponent equilibrium was better described by heterogeneous models, particularly the double-layer model and Extended Sips, indicating non-equivalent adsorption domains. Thermodynamic parameters showed favorable and mildly endothermic adsorption with limited temperature dependence. Mixture-design experiments demonstrated that metal proportion influenced adsorption more strongly than temperature, with increasing Cd(II) fractions reducing Zn(II) retention. Overall, Mg–Fe-LDH@HC showed promising performance for Cd(II)/Zn(II) removal under competitive conditions, although the adsorption pathway should be interpreted as an evidence-supported combined process rather than individually confirmed mechanisms. Full article

Heavy metals (HMs) such as copper (Cu), lead (Pb), cadmium (Cd), chromium (Cr) and zinc (Zn) from industrial activities are discharged into nearby water resources after treatment. In the present study, the potential of utilizing chemically activated carbon derived from water hyacinths as a sustainable and low-cost adsorbent for heavy metal removal from industrial wastewater from the Nakawa industrial area, Uganda was investigated. The measured physicochemical parameters of wastewater (temperature, pH, electrical conductivity, total dissolved solids, turbidity, dissolved oxygen, chlorides and total hardness) varied significantly among the three sampled sites (p < 0.05), except for pH. Similarly, the concentration of the HMs in the samples (0.54 ± 0.04 mg L⁻¹ for Cr to 93.54 ± 0.07 mg L⁻¹ for Pb) varied significantly between sites (p < 0.05), exceeding the maximum permissible limits of Cd, Pb, Cr, Cu and Zn specified in the National Environment Standards for Discharge of Effluent into Water or Land. The water hyacinth biomass was activated using eggshell powder and phosphoric acid, followed by thermal treatment. Characterization using Fourier-transform infrared spectroscopy and scanning electron microscopy confirmed that there was improvement in its surface functionality and porosity post activation. Batch adsorption experiments indicated that optimal removal of the HMs was achieved at pH 4–5, contact time of 90 min, and 1.0 g of adsorbent. Maximum adsorption capacities of Pb, Cd, Cu, Cr and Zn were in the range of 1.04–8.36 mg g⁻¹. Under the optimized conditions, the eggshell-activated carbon derived from water hyacinths had removal efficiencies of 91.2 ± 9.1% (range: 71.3–100%). Adsorption occurred through both monolayer and multilayer coverage, as indicated by the experimental data which fitted well to the Freundlich isotherm (Cd²⁺, Pb²⁺, Zn²⁺ and Cu²⁺ ions) and Langmuir isotherm model (Cr³⁺ ions). These results support the potential of water hyacinth-derived activated carbon as an ecofriendly alternative for treating low concentrations of these HMs in industrial wastewater. Full article

Coal gasification slag (CGS), a massive industrial solid waste, possesses inherent adsorptive potential that remains underutilized due to pore blockage by amorphous siliceous phases. Conventional modification strategies typically rely on energy-intensive high-temperature processes. Herein, we report a facile, low-temperature alkaline activation approach to transform CGS into a high-efficiency adsorbent (denoted NCGS) for Cd²⁺ removal. Sodium hydroxide (NaOH) solution was employed under mild conditions (90 °C) to selectively etch siliceous species, thereby generating a porous architecture and enriching surface oxygen-containing functionalities. Orthogonal experimental design identified optimal synthesis parameters (1 mol/L NaOH, solid–liquid ratio of 1:30 g/mL, 12 h), yielding NCGS with significantly enhanced textural properties. The adsorption isotherm was well described by the Langmuir model, with a maximum capacity of 87.06 mg/g at pH 6.0, while kinetic studies indicated the adsorption process could be described by pseudo-second-order kinetic model. Comprehensive characterization via SEM-EDS, FTIR, and XPS elucidated a multi-mechanistic adsorption pathway mainly involving ion exchange (Na⁺/Cd²⁺) and coordination complexation. Life cycle assessment analysis revealed that NCGS production generates 11.23 kg CO₂ eq emissions, with transportation accounting for 88%. This study presents an energy-saving and environmentally friendly strategy to unlock the adsorptive potential of CGS, providing a highly promising waste-based adsorption material for the remediation of Cd²⁺-contaminated water. Full article

Biomass thermochemical conversion-derived hydrochar has been increasingly recognized as a functional resource for environmental remediation, but knowledge about the effect of the carbonization conditions on the surface chemistry and binding behaviour of hydrochar is still limited. In this study, hydrochar from two different processing pathways, pressure reactor carbonization (P-RC) and microwave-assisted carbonization (M-RC), is compared to understand the mechanisms of contaminant interaction and the changes in structure that occur during the carbonization processing. P-RC was synthesized at the hydrothermal temperatures (180, 220, and 250 °C) for 2 and 5 h, while M-RC was synthesized at microwave irradiation for 30 min and 1 h. TGA, SEM–EDS, FTIR, and XRD were used for comprehensive characterization, which revealed systematic differences in functional group distribution, mineral phases, and microstructural development between the two carbonization methods and at different carbonization temperatures. The increase in P-RC temperature led to greater aromatic condensation, thermal stability, and mineral reorganization, while M-RC maintained a higher percentage of oxygenated functionality and a more heterogeneous surface morphology. Batch adsorption experiments indicated that the M-RC hydrochar had a faster adsorption rate, attributed to its greater number of reactive oxygenated functionalities, whereas the P-RC hydrochar produced at higher temperatures exhibited a more even distribution of adsorption sites and stronger mineral-assisted interactions. The kinetics and isotherm modeling also showed different interaction pathways: for M-RC, surface complexation on heterogeneous sites was favored, whereas for P-RC, a more monolayer-like adsorption was observed. These results collectively show how the method and temperature of carbonization affect reactivity and support the establishment of mechanistic relationships crucial to maximizing the utility of hydrochar as a functional material for environmental remediation. Full article

To address the ecological risks associated with highly mobile hexavalent chromium [Cr(VI)], woody biochar was functionalized with hydrogen peroxide (H₂O₂) to develop a dual-phase remediation material (H-BC) for aqueous and soil environments. Batch post-contact isotherm fitting yielded a Langmuir-fitted/extrapolated apparent retention capacity q_m of 77.44 mg/g at 328 K. This value reflects enhanced overall Cr(VI)-derived retention within the tested concentration range, rather than increased electrostatic affinity for chromate oxyanions. Empirical kinetic diagnostics and FTIR/XPS results were consistent with adsorption-coupled interfacial reduction, while DFT analysis provided qualitative support for the enhanced electronic responsiveness of H-BC. The OFG-enriched interface may facilitate short-range, non-electrostatic interfacial interactions and stabilize surface-associated Cr(III). Temperature-dependent apparent isotherm fitting suggested that elevated temperature favored the overall Cr(VI)-derived retention process under the tested conditions, and should not be interpreted as rigorous standard-state adsorption thermodynamics. Continuous-flow column leaching and accelerated wet–dry (W–D) aging experiments demonstrated that H-BC substantially suppressed the mobility of operationally filtered Cr(VI), achieving a maximum filtered-Cr(VI)-based retention efficiency of 99.98% under cyclic drying–rewetting conditions. Spatial configuration analysis indicated that homogeneous incorporation of H-BC improved soil–biochar contact and was more effective than stratified placement in limiting vertical filtered-Cr(VI) migration. Overall, oxidatively functionalized H-BC shows promise as a biomass-derived amendment for reducing Cr(VI) mobility in complex environmental matrices, although complete chromium mass redistribution will require future total-Cr and Cr(III)-resolved analyses. Full article

The disposal of high-water-content bentonite slurry generated from underground construction presents prominent environmental and technical challenges, calling for low-carbon and efficient consolidation technologies. This study proposes an integrated flocculation–preloading–electro-osmosis (FPE) method using anionic polyacrylamide (APAM) combined with ground granulated blast furnace slag to strengthen dewatering and stabilization of bentonite slurry. Settlement column experiments were conducted to determine the optimal APAM dosages. A series of FPE consolidation experiments were performed to monitor drainage, settlement, electrical current, temperature and post-treatment soil properties, combined with microstructural analysis to reveal the synergistic mechanism. The results show that APAM creates abundant seepage channels via adsorption bridging and flocculation, significantly accelerating early-stage drainage and settlement rates without obviously increasing total drainage and final settlement. The polymer hydrogel homogenizes soil structure, leading to a gradual increase in moisture content and decrease in shear strength from anode to cathode, and effectively eliminates cracking during electro-osmosis. The temporary seepage channels induce a faster initial current rise, while the polymer coating increases apparent resistivity after free water discharge, thereby reducing current and temperature during the electro-osmotic consolidation stage. Appropriate APAM dosage thickens the electric double layer to raise the free swell ratio, whereas excessive dosage restricts swelling by particle coating. Microscopic observations confirm that chain-structured APAM and flocculent C-(A)-S-H hydration products cement soil particles and fill pores, improving soil integrity and shear strength. Overall, APAM improves early-stage efficiency and soil uniformity/integrity. In addtion, its combined effect with slag on bentonite shear strength increase is relatively higher than that of 0% slag condition. The integrated FPE technique realizes synchronous high-efficiency dewatering and low-carbon stabilization of high-water-content bentonite slurry, providing a novel and practical solution for engineering slurry disposal. Full article

China is rich in high-sulfur natural gas resources. During reservoir development, reservoir temperature and pressure reduction induces the precipitation of elemental sulfur. Subsurface sulfur deposition seriously affects the recovery and the stable production of high-sulfur gas reservoirs. This study utilized multiple experimental techniques, including CT scanning, scanning electron microscopy, energy spectrum analysis, and nuclear magnetic resonance. The experiments were conducted under different water saturation levels and pressure differences. The results showed that the permeability of the rock samples decreased after sulfur deposition. The permeability reduction varied from 0.004 mD to 8.852 mD, with a relative change of 10.2% to 29.8%. Meanwhile, sample porosity also declined, and the porosity damage ranged from 1.5% to 11.9%. Scanning electron microscopy showed that sulfur presented a membrane adsorption morphology on the surface of skeleton particles, with spherical particles protruding from the membrane. Rock samples with poorer physical properties showed lamellar superposition sulfur deposition. Sulfur deposition damage became more severe with increasing pressure difference and weakened as water saturation increased. Beyond a water saturation of 40.6%, further increases no longer reduce sulfur deposition damage. Full article

Dye removal from aqueous solutions remains a major global environmental challenge. Among the various remediation techniques, adsorption using natural materials has gained significant attention. In this study, the adsorption of methylene blue (MB) by a natural volcanic rock (VR) adsorbent—collected from the Cerro Blanco volcano in Divisaderos, Sonora, Mexico—was investigated, and the process efficiency was evaluated at different temperatures. The comprehensive characterization revealed a rough and irregular porous surface via SEM, while the EDS elemental data and the CIPW normative calculations identified the material as a silica-saturated tholeiitic basalt, primarily composed of bytownite (${An}_{71})$ and pyroxenes. This petrological classification was cross-validated by XRD and FTIR spectra, which exhibited vibrational modes characteristic of mafic silicate. The surface analysis via the BET method indicated a specific surface area of 12 m²·g⁻¹, while a BJH analysis indicated a mesoporous structure (average pore diameter of 3.75 nm), and a Type IV isotherm with H3-type hysteresis, suggesting narrow, slit-shaped pores. Batch adsorption experiments demonstrated an exceptional removal efficiency of 99.99% for 50 mg·L⁻¹ MB within only 30 min. The equilibrium data and the adsorption kinetics followed the Langmuir isotherm and a pseudo-second-order model, respectively. Cytotoxicity assays confirmed the VR is biosafe. The combination of high removal efficiency, low cost, and environmental safety positions this material as high-potential adsorbent for sustainable water remediation processes. Full article

CO₂/N₂-enhanced coalbed methane recovery (ECBM) offers a potential route to improve coalbed methane production, reduce CH₄ emissions, and couple gas drainage with low-carbon coal development. However, the relative roles of adsorption-controlled replacement and pressure-driven displacement under deep stress conditions remain insufficiently resolved. Here, CO₂ and N₂ injection experiments were conducted under different vertical stresses to quantify the evolution of gas flow, breakthrough time, increase in coal gas content, replacement–displacement ratios, and injection efficiency. Increasing stress compressed the pore–fracture network, reduced gas transport capacity, and delayed breakthrough of the injected gas. CO₂, because of its strong adsorption affinity, remained dominated by replacement throughout the injection process. Higher stress enhanced CO₂ retention in coal and therefore its potential storage capacity, but it also weakened sustained CH₄ recovery by restricting transport. In contrast, N₂, which adsorbs weakly, rapidly shifted to displacement-dominated recovery after breakthrough. Although high stress delayed the formation of connected displacement pathways, N₂ maintained high injection efficiency. These results show that stress controls the dominant ECBM mechanism by regulating adsorption retention, seepage transport, and displacement outflow. The findings provide a mechanistic basis for selecting injection gases and designing low-carbon ECBM strategies in deep coal seams. Full article