Search Results (116)

This study investigates the capacity of green and brown algae to sustainably remove oxyanions from contaminated waters, highlighting their cost-effectiveness. Often considered biomass waste and contributors to organic contamination, these algae can be used as effective biosorbents, aligning with circular economy principles and sustainable waste management. Various pre-treatments were tested to enhance adsorption capacity, with mixed results regarding their effectiveness. The focus then shifted to the use of Cladophora sericea algae for the uptake and removal of selenium species, specifically selenite (Se(IV)) and selenate (Se(VI)). The effects of different operational parameters on oxyanion uptake by algae were studied in batch mode. The assessments were conducted on a single-component and a multi-component synthetic matrix. The results indicate that pH significantly impacts biosorption, with equilibrium achieved in 90 min. Both pseudo-first-order and pseudo-second-order models provided a good fit to the experimental data. The algae’s retention capacity for selenium remained largely unaffected by the presence of other anions, a key advantage for application in complex real effluent matrices. Kinetic studies performed under different values of initial pollutant concentration and biosorbent mass indicate a biosorbed amount at an equilibrium of 570 µg g⁻¹. Full article

A versatile, clear, and accurate method for determining the steady states of multi-component diffusion through composite membranes is presented in this study. This method can be used for simulating and designing membranes with any support orientation with respect to the zeolite film. In the mathematical model of the membrane, it was assumed that mass transport in the zeolite layer occurs by surface diffusion in accordance with the generalized Maxwell–Stefan model. Diffusion in the macroporous support was described by the dusty gas model (DGM). An alternative model of diffusion in the zeolite was proposed to the universally accepted model, which uses a matrix of thermodynamic factors Γ. Thus, the difficulty of analytically determining this matrix for more complex adsorption equilibria was eliminated. This article is dedicated to methodological and cognitive aspects. The practical features of the method are illustrated using two gas mixtures as examples, namely {H₂, CO₂} and {H₂, n-C₄H₁₀}. The roles of zeolite and support in the separation of these mixtures are discussed. It was demonstrated under what circumstances the presence of the support can be neglected in the steady-state analysis of the membrane. The effect of the alternative application of the dusty gas model or viscous flow only in the microporous support was discussed. Full article

The efficient degradation of antibiotics in pharmaceutical wastewater remains a critical challenge against environmental contaminants. Conventional photocatalysts face potential limitations such as narrow visible-light absorption, rapid carrier recombination, and reliance on precious metal cocatalysts. This review investigates the coordination structure of MXene as a cocatalyst to synergistically enhance photocatalytic antibiotic degradation efficiency and the coordination structure modification mechanisms. MXene’s tunable bandgap (0.92–1.75 eV), exceptional conductivity (100–20,000 S/cm), and abundant surface terminations (-O, -OH, -F) enable the construction of Schottky or Z-scheme heterojunctions with semiconductors (Cu₂O, TiO₂, g-C₃N₄), achieving 50–70% efficiency improvement compared to pristine semiconductors. The “electron sponge” effect of MXene suppresses electron-hole recombination by 3–5 times, while its surface functional groups dynamically optimize pollutant adsorption. Notably, MXene’s localized surface plasmon resonance extends light harvesting from visible (400–800 nm) to near-infrared regions (800–2000 nm), tripling photon utilization efficiency. Theoretical simulations demonstrate that d-orbital electronic configurations and terminal groups cooperatively regulate catalytic active sites at atomic scales. The MXene composites demonstrate remarkable environmental stability, maintaining over 90% degradation efficiency of antibiotic under high salinity (2 M NaCl) and broad pH range (4–10). Future research should prioritize green synthesis protocols and mechanistic investigations of interfacial dynamics in multicomponent wastewater systems to facilitate engineering applications. This work provides fundamental insights into designing MXene-based photocatalysts for sustainable water purification. Full article

Shale oil is a vital strategic resource in China. Developing shale oil using CO₂ not only enhances oil recovery but also contributes to achieving Chinese “dual carbon” goals. Given the challenges of insufficient number of fractures, inadequate vertical stimulation volume, and poor reservoir mobility associated with horizontal well fracturing, this study proposes a method for CO₂ flooding based on radial borehole fracturing in a single well to achieve long-term carbon sequestration. To this end, a multi-component numerical model is built to analyze the production capacity of radial borehole fracturing. This study analyzed the impacts of non-Darcy flow, diffusion, and adsorption mechanisms on CO₂ migration and sequestration. It also compared the applicability of continuous CO₂ flooding and CO₂ huff-and-puff under different matrix permeabilities. The results indicate that (1) CO₂ flooding using radial borehole fracturing can achieve long-term oil production and carbon sequestration. (2) Under low permeability conditions, the liquid non-Darcy effect retards the flow of oil and CO₂, while diffusion and adsorption facilitate CO₂ sequestration in the reservoir. The impact on carbon sequestration is ranked as follows: non-Darcy effect > adsorption > diffusion. (3) High-permeability reservoirs are more suitable for carbon sequestration and should utilize continuous CO₂ flooding. For low-permeability reservoirs (<0.001 mD), huff-and-puff should be employed to mobilize the reservoir around fractures and achieve carbon sequestration. The findings of this study are expected to provide new methods and a theoretical basis for efficient and economical carbon sequestration in shale oil reservoirs. Full article

Mycotoxins are common feed contaminants that can affect the health, immune function, and productivity of ruminants by causing oxidative stress and organ dysfunction. In this field study, the effects of a phytogenic multicomponent mycotoxin detoxifier on oxidative status, liver function, udder health, and productive parameters were investigated in dairy ewes. One hundred clinically healthy ewes were randomly assigned to either a control group or a treatment group, with the latter receiving 1.5 kg/ton of the detoxifier over a 90-day period during lactation. The detoxifying agent contained adsorptive clays as well as phytogenic ingredients such as silymarin and curcumin, which are known for their hepatoprotective and antioxidant properties. Blood, milk, and colostrum samples were collected and analyzed for oxidative stress markers (TBARS and protein carbonyl (CARBS)), total antioxidant capacity (TAC), liver enzymes (ALT, AST, and ALP), and milk quality parameters (fat, protein, and solid content). Clinical assessments included mastitis scoring, udder inflammation, and fecal consistency. The treated ewes showed a statistically significant reduction in blood plasma and milk oxidative stress markers and liver enzyme levels while at the same time improving the fat and solid content of the milk. The incidence and severity of mastitis, udder reddening, and lactation abnormalities were lower in the treatment group. Brix refractometry indicated improved colostrum quality in the treated ewes. These results suggest that the detoxifier improved the oxidative balance, liver function, and overall health and productivity of dairy ewes under field conditions, supporting its use as a practical nutritional measure. Full article

Adsorption of multicomponent mixtures on solid substrates is essential to numerous technological processes and provides key insights into surface phenomena. Despite advancements in theoretical modeling, many approaches still assume that each adsorbate occupies a single site, thereby neglecting important effects arising from molecules that span multiple adsorption sites. In this work, we broaden the theoretical description of such systems by considering the adsorption of j distinct polyatomic species on triangular lattices. Our approach is based on (i) exact thermodynamic results for polyatomic gases on one-dimensional lattices, extended here to account for substrates with higher coordination numbers, and (ii) the “0D cavity” functional theory originally developed by Lafuente and Cuesta, which reduces to the well-known Guggenheim–DiMarzio model in the limit of rigid rods. As a case study, we explore the behavior of a three-component system consisting of dimers, linear trimers, and triangular trimers adsorbing onto a triangular lattice. This model captures the interplay between structural simplicity, multisite occupancy, configurational diversity, and competition for space, key factors in many practical scenarios involving size-asymmetric molecules. We characterize the system using total and partial isotherms, energy of adsorption, and configurational entropy of the adsorbed phase. To ensure the reliability of our theoretical predictions, we perform Monte Carlo simulations, which show excellent agreement with the analytical approaches. Our findings demonstrate that even complex adsorption systems can be efficiently described using this generalized framework, offering new insights into multicomponent surface adsorption. Full article

A hetero-disubstituted sugarcane bagasse (HDSB) was prepared by simultaneous one-pot chemical modification of sugarcane bagasse with succinic and phthalic anhydrides. HDSB was used in batch mode for the removal of the cationic dyes auramine-O (AO) and safranin-T (ST) from spiked aqueous solutions. Adsorption of the dyes in mono- and bicomponent systems was investigated as a function of HDSB dosage, pH, contact time, and initial dye concentration. Maximum adsorption capacities for AO and ST on HDSB, at pH 7.0, were 1.37 mmol g⁻¹ (367.7 mg g⁻¹) and 0.93 mmol g⁻¹ (293.3 mg g⁻¹), respectively. In the bicomponent system, ST was preferentially adsorbed on HDSB, revealing an antagonistic effect of ST on AO adsorption. Changes in the enthalpy of the adsorption as a function of HDSB surface coverage were determined by isothermal titration calorimetry, with Δ_adsH° values for AO and ST equal to −22.1 ± 0.3 kJ mol⁻¹ and −23.44 ± 0.01 kJ mol⁻¹, respectively. Under standard conditions, the adsorption of the dyes on HDSB was exergonic and enthalpically driven. Desorption removed ~50% of the adsorbed dyes, and subsequent re-adsorption showed that HDSB could be reused, with non-desorbed dye molecules acting as new binding sites. The interaction between AO and ST with HDSB was elucidated by molecular dynamics simulations with atomistic modeling. Full article

To facilitate the local recycling of coal mine waste gas and investigate multi-component gas adsorption under high pressure conditions, this study develops a coal nanopore model using molecular dynamics (MD) and grand canonical Monte Carlo (GCMC) methods and simulates the adsorption behavior of coal mine waste gas components (CO₂, H₂O, N₂) under varying pressure levels and gas molar ratios at 353.15 K. We evaluated the adsorption capacity and selectivity for both single-component and multi-component gases, quantifying adsorption interactions through adsorption heat, interaction energy, and energy distribution. The simulation results revealed that the contribution of the three gases to the total adsorption amount followed the order: H₂O > CO₂ > N₂. The selective adsorption coefficient of a gas exhibits an inverse correlation with its molar volume ratio. Isothermal heat adsorption of gases in coal was positive, decreasing sharply with increasing pressure before leveling off. Electrostatic interactions dominated CO₂ and H₂O adsorption, while van der Waals forces governed N₂ adsorption. As the gas mixture complexity increased, the overlap of energy distribution curves pronounced, highlighting competitive adsorption behavior. These findings offer a theoretical foundation for optimizing coal mine waste gas treatment and CO₂ sequestration technologies. Full article

This study addresses the growing concern of water contamination by pharmaceutical residues, focusing on the simultaneous removal of paracetamol (PAR) and metronidazole (MTZ). Batch and fixed-bed column adsorption processes were evaluated using activated carbon. In the batch experiments, the effects of pH (3, 7, and 11), adsorbent mass (0.5, 1.25, and 2 g), and contact time (10, 30, and 60 min) were evaluated, while the fixed-bed column was optimized considering initial pollutants concentration (30, 40, and 50 mg/L), adsorbent mass (0.5, 0.75, and 1 g), and flow rate (5, 10, and 15 mL/min) to improve the maximum adsorption capacity of the bed for both pollutants (q_maxPAR and q_maxMTZ). Parameter estimation and model selection were performed using a Bayesian Monte Carlo approach. Optimal conditions in the batch system (pH = 7, W = 2 g, and time = 60 min) led to high removal efficiencies for both compounds (≥98%), while in the column system, the initial pollutant concentration was the most significant parameter to improve the maximum adsorption capacity of the bed, resulting in values equal to 49.5 and 43.6 mg/g for PAR and MTZ, respectively. The multicomponent Gompertz model showed the best performance for representing the breakthrough curves and is suitable for scale-up (R² ≥ 0.75). These findings highlight the complexity of multicomponent adsorption and provide insights, contributing to the development of more efficient and sustainable water treatment technologies for pharmaceutical residues. Full article

Volatile Organic Compounds (VOCs) are essential for primary pharmaceutical manufacturing. Their permissible emission levels are strictly regulated due to their toxic effects both on human health and the environment. Activated carbon adsorption columns are used in industry to treat VOC gaseous waste streams from industrial plants, but their process efficiency suffers from quick and unpredictable saturation of the adsorbent material. This study presents the application of a validated, non-isothermal, multicomponent adsorption model using the Langmuir Isotherm and the Linear Driving Force model to examine multicomponent VOC mixture breakthrough. Specifically, three binary mixtures (hexane–acetone, hexane–dichloromethane, hexane–toluene) are simulated for four different bed lengths (0.25, 0.50, 0.75, 1 m) and six different superficial velocities (0.1, 0.2, 0.3, 0.5, 0.7, 0.9 m s⁻¹). Key breakthrough metrics reveal preferential adsorption of acetone and toluene over hexane, and hexane over dichloromethane, as well as breakthrough onset patterns. Temperature peaks are moderate while pressure drops increase for longer column lengths and higher flow rates. A new breakthrough onset metric is introduced, paving the way to improved operating regimes for more efficient industrial VOC capture bed utilisation via altering multicomponent mixture composition, feed flowrate, and column length. Full article

This study investigates the potential of biochars derived from agricultural waste biomass for the removal of heavy metal ions from aqueous solutions. Biochars were produced via slow pyrolysis at 793 K using almond shells (AS), walnut shells (WS), pistachio shells (PS), and rice husks (RH) as feedstocks. The physicochemical properties and adsorption performance of the resulting materials were evaluated with respect to Cd(II), Mn(II), Co(II), Ni(II), Zn(II), total Iron (Fe_tot), total Arsenic (As_tot), and total Chromium (Cr_tot) in model solutions. Surface morphology, porosity, and surface chemistry of the biochars were characterized by scanning electron microscopy (SEM), nitrogen adsorption at 77 K (for specific surface area and pore structure), Fourier-transform infrared spectroscopy (FTIR), and determination of the point of zero charge (pH_pzc). Based on their textural properties, biochars derived from WS, PS, and AS were classified as predominantly microporous, while RH-derived biochar exhibited mesoporous characteristics. The highest Brunauer–Emmett–Teller (S_BET) surface area was recorded for PS biochar, while RH biochar showed the lowest. The pistachio shell biochar exhibited the highest specific surface area (440 m²/g), while the rice husk biochar was predominantly mesoporous. Batch adsorption experiments were conducted at 25 °C, with an adsorbent dose of 3 g/L and a contact time of 24 h. The experiments in multicomponent systems revealed removal efficiencies exceeding 87% for all tested metals, with maximum values reaching 99.9% for Cd(II) and 97.5% for Fe_tot. The study highlights strong correlations between physicochemical properties and sorption performance, demonstrating the suitability of these biochars as low-cost sorbents for complex water treatment applications. Full article

The large-scale production of high-purity hydrogen via pressure swing adsorption (PSA) remains a prominent research focus. This study develops a multi-component heat and mass transfer model for a lean hydrogen mixture (N₂/CO₂/H₂/CO = 44.6/35.4/19.9/0.1 mol%) on a coal-derived activated carbon (AC)/zeolite 13X layered bed to investigate its breakthrough curve and PSA purification performance. The model is implemented on the Aspen Adsorption platform and validated with published data. Parametric analysis of the breakthrough curve reveals that a high pressure and a low feed flow rate can delay the breakthrough of impurity gases. The simulated variations in pressure, purity, and recovery during the PSA cycle align with the published results. Studies on PSA cycle parameters show that, in general, a high pressure, a low feed flow rate, a short adsorption time, and a high P/F ratio improve purity but reduce recovery. The purity and recovery of the layered bed outperform those of the single-layer bed. Specifically, gradually modifying the AC/zeolite 13X length ratio from 10:0 to 5:5 enhances hydrogen purity, while adjusting it from 10:0 to 3:7 enhances hydrogen recovery. At AC/zeolite 13X = 5:5, the highest purity was 97.38%, while at AC/zeolite 13X = 3:7, the highest recovery was 49.13%. Full article

N-nitroso dimethylamine (NDMA), a common nitrogen disinfection by-product and carcinogen, can be removed using rapid sand filtration (RSF) after coagulation; however, its removal mechanism has not been extensively studied. This study analyzed NDMA and the water pollutant parameter removal rate change tendency in the filtrates of simulated supernatants directly and after enhanced coagulation (EC) using composite PAC/PDMDAAC that mimics treated Yangtze River water separated into blank, single-component, and mixed multi-component (MMC) water systems containing NDMA and pollutants like diatomite (DTA), humic acid salt (HAs), dimethyl amine (DMA), and ammonium nitrate (NH₄NO₃). Meanwhile, a correlation analysis of removal rate changes and adsorption analysis using SEM (surface morphology), polar functional groups, and zeta potentials (surface charge) were performed to obtain mechanistic insights into NDMA removal via adsorption. The results revealed that removal rates gradually increased with an increasing volume of filtrates, and there were correlations for NDMA-HAs, NDMA-DMA, NDMA-DTA, and NDMA-NH₄NO₃. The highest NDMA removal rates in the blank system were 10.29% using RSF directly and 12.84% after enhanced coagulation, indicating improved efficiency with coagulation. However, single and mixed systems showed that NDMA removal rate changes were enhanced by water pollutants and coagulation functions. The NDMA removal mechanism was verified, and it was revealed that the level of NDMA adsorption on water pollutants varies based on microstructure, available polar functional groups, and surface charge interactions that are strengthened by coagulation functions for improving the affinity of NDMA and pollutants on the sand surface. These findings provide new insights into NDMA removal mechanisms via adsorption and highlight the role of water pollutants and enhanced coagulation in strengthening rapid sand filtration for NDMA removal. Full article

Using raw and modified lignocellulosic residues as bioadsorbents in continuous adsorption is challenging but it marks significant progress in water treatment and the transition to a bio-based circular economy. This study reviews the application of bioadsorbents in fixed-bed columns for treating water contaminated with inorganic species, offering guidance for future research. It evaluates chemical modifications to enhance adsorptive properties, explores adsorption mechanisms, and analyzes bioadsorbent performance under competitive adsorption conditions. Analysis of adsorption data included evaluation of adsorption capacity in mono- and multicomponent solutions, regeneration, reuse, bed efficiency, and disposal of spent bioadsorbents. This enabled assessing their scalability to sufficiently high levels of maturity for commercialization. In multicomponent solutions, selectivity was influenced by the characteristics of the bioadsorbents and by competitive adsorption among inorganic species. This affected adsorption performance, increasing the complexity of breakthrough curve modeling and controlling the biomaterial selectivity. Models for mono- and multicomponent systems are presented, including mass transfer equations and alternatives including “bell-type” equations for overshooting phenomena and innovative approaches using artificial neural networks and machine learning. The criteria discussed will assist in improving studies conducted from cradle (synthesis of new biomaterials) to grave (end use or disposal), contributing to accurate decision making for transferring the developed technology to an industrial scale and evaluating the technical and economic feasibility of bioadsorbents. Full article

This study introduced a novel type of biochar–titanate nanosheet (BC@TNS) composite for the selective adsorption of Pb(II) from wastewater containing various heavy metal ions. The biochar derived from lignin–carbon pyrolysis forms the scaffold, while titanate nanosheets coat it via an alkaline hydrothermal reaction. The synthesis was confirmed through analytic characterizations, revealing a distinctive morphology of TNS nanoflowers consisting of numerous nanosheets incorporated into the BC support. BC@TNS achieved maximum adsorption capacities of 37.89 mg/g for Pb(II), 13.38 mg/g for Cd(II), and 8.47 mg/g for Zn(II), demonstrating its remarkable selectivity for Pb(II). Kinetic studies using Weber–Morris, PFO, and PSO models indicated that Pb(II) adsorption was primarily driven by chemisorption, whereas Cd(II) and Zn(II) adsorption were predominantly governed by physisorption. Isotherm analysis using Langmuir, Freundlich, Dubinin–Radushkevich, and Temkin models revealed that Pb(II) adsorption involved both monolayer and multilayer processes, while Cd(II) and Zn(II) adsorption were primarily monolayer. Detailed insights from scanning electron microscopy (SEM-EDS) and X-ray photoelectron spectroscopy (XPS) analyses further elucidated these mechanisms. The superior selectivity of BC@TNS for Pb(II) was further validated in multicomponent simulated HMs containing 10 co-existing metal ions, maintaining a high Pb(II) adsorption efficiency of 75.68%, highlighting its potential for selective Pb recovery. Moreover, the adsorbent demonstrated excellent regeneration capacity and recyclability. The BC@TNS adsorbent shows great potential for the selective and efficient removal of Pb(II) ions from wastewater, offering a sustainable solution for environmental protection. Full article