Search Results (277)

Arabinoxylan is a polysaccharide with film-forming properties, present in corn fiber, and a low-value by-product. The extract has a deep brown color, producing films of the same shade, which may not be appealing. This study addresses, for the first time, the adsorption of colored compounds present in an arabinoxylan extract using resin MN102. The resin successfully adsorbed the colored compounds from the arabinoxylan extract. After four consecutive adsorption/desorption cycles, the efficiency of the resin was similar, only decreasing from 63.3% to 52.9%. Langmuir and Freundlich models were fitted to the results of adsorption isotherm experiments, with the Freundlich model demonstrating the best fit to the experimental results. A fixed-bed column loaded with the resin was used for the removal of the colored compounds from the arabinoxylan extract, and the effect of the volumetric flow rate was investigated. The Yan and log-Gompertz models showed the best fit to the experimental breakthrough curves. This study systematically evaluated the adsorption conditions, providing a comprehensive analysis of the performance of the resin in the removal of the colored compounds. Additionally, the ability of the extract to maintain its film-forming properties after decolorization was evaluated, and some of the film’s key characteristics were evaluated, namely its color, solubility in water and mechanical properties. Full article

Arsenic contamination in groundwater is a significant public health concern, with As(III) posing a greater and more challenging risk than As(V) due to its higher toxicity, mobility, and weaker adsorption affinity. Fe-Mn-based adsorbents offer a promising solution, simultaneously oxidizing As(III) to As(V), enhancing its adsorption. This study evaluates an Fe-Mn nanocomposite across typical batch (20 mg of adsorbent), fixed-bed column (28 g), and pilot-scale (2.5 kg) studies, bridging the gap between laboratory and real-world applications. Batch experiments yielded maximum adsorption capacities of 6.25 mg/g and 4.71 mg/g in a synthetic matrix and real groundwater, respectively, demonstrating the impact of the water matrix on adsorption. Operational constraints and competing anions led to a lower capacity in the pilot (0.551 mg/g). Good agreement was observed between the breakthrough curves in the pilot (breakthrough at 475 bed volumes) and the fixed-bed column studies (365–587 bed volumes) under similar empty bed contact times (EBCTs). The Thomas, Adams–Bohart, and Yoon–Nelson models demonstrated that lower flow rates and extended EBCTs significantly enhance arsenic removal efficiency, prolonging the operational lifespan. Our findings demonstrate the necessity of continuous-flow experiments using real contaminated water sources and the importance of optimizing flow conditions, EBCTs, and pre-treatment in order to successfully scale up Fe-Mn-based adsorbents for sustainable arsenic removal. 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

A catalyst with the active component Cu loaded onto the carrier activated carbon was prepared, and metal Ca was introduced into the catalyst to modify it. This catalyst was used in the hydrogenation reaction of dimethyl oxalate, and the reaction kinetics was studied. The kinetic experiments were carried out in a fixed bed reactor with a reaction temperature varying from 483 K to 513 K, reaction pressure varying from 1.5 Mpa to 2.5 Mpa, and the weight hourly space velocity of dimethyl oxalate varying from 0.435 h⁻¹ to 0.726 h⁻¹. Eight possible dynamic models were proposed, the optimal model was selected, and the parameters of the optimal model were calculated using MATLAB. The results showed that dimethyl oxalate adsorbed on the active site by dissociation adsorption, and the dissociation adsorption of ester was the rate-controlling step. The parameters of the model were consistent with thermodynamics and statistical analysis, further proving that the model has good forecasting performance. Full article

In this study, the adsorption of a textile dye from water onto activated carbon is considered and the results of our own experimental studies on adsorption equilibrium and kinetics are presented. The adsorption isotherm and kinetic curves were found to reflect the possibility of removing the dye from water by adsorption onto activated carbon. Kinetic studies were conducted using a fixed bed of adsorbent grains. The water and dye solution flowed through the column with the adsorbent. The main aim of this study was to determine diffusion coefficients and mass transfer coefficients. The values of the external mass transfer coefficient and external diffusion coefficient of the dye in water were calculated for different flow rates of the solution, i.e., for different external resistance values. The external diffusion coefficient was D_AB = 2.21·10⁻¹⁰ m²/s and the external mass transfer coefficient was between k_c = 4.813·10⁻⁸ m/s for the lowest solution velocity in the adsorber equal to 0.0693 m/s and k_c = 5.623·10⁻⁸ m/s for the highest velocity equal to 0.185 m/s. The internal diffusion coefficient and internal mass transfer coefficient, i.e., the coefficients of the transfer from the external surface of a grain to its interior, were determined with the use of the analytical solution of the diffusion and adsorption equation For the apparent solution velocity of 0.0693 m/s the internal diffusion coefficient was D_s = 0.57·10⁻¹⁰ m²/s and the internal mass transfer coefficient was k_s = 1.89·10⁻¹⁰ m/s. For the velocity of 0.163 m/s, the internal diffusion coefficient was D_s = 0.84·10⁻¹⁰ m²/s and the internal mass transfer coefficient was k_s = 9.00·10⁻¹⁰ m/s. The results of the calculations presented are a measure of the efficiency of a given adsorbent in a given system. The values obtained for the mass transfer coefficients can be used as data for further calculations of this process. Full article

Research on using biochar as an adsorbent of contaminants in aqueous matrices has gained significant relevance in recent years due to the surface chemistry and porous structure of biochar, which facilitate the retention of a wide range of pollutants. This study explores the adsorption performance of a novel biochar produced from agave bagasse—a readily available agro-industrial waste in Mexico—through low-temperature pyrolysis. The biochar was evaluated for its capacity to remove conventional water quality parameters (chemical oxygen demand (COD), nitrates (NO₃⁻), total nitrogen (TN), total phosphorus (TP), ammonium (NH₄⁺), turbidity, apparent color, and true color) from water samples collected from the polluted Bustillos Lagoon in Chihuahua, Mexico. Additionally, the removal of emerging pharmaceutical contaminants, specifically acetaminophen (Act) and diclofenac (Dfc), was assessed in synthetic aqueous solutions. Potentiometric titration analyses revealed a significant contribution of surface acidity in the adsorption of pharmaceutical derivatives, highlighting the relevance of functional groups retained during low-temperature pyrolysis. The biochar derived from agave bagasse (BBAF1) was tested in a fixed-bed column system and compared with two commercial activated carbons (CACCF2 and CVCF3). The BBAF1 biochar achieved average removal efficiencies ranging from 50% to 90% for all conventional parameters. In contrast, those of ACT and DFC were between 0.43 and 0.67 mg g⁻¹ (59–85%) and 0.34 and 0.62 mg g⁻¹ (37–79%), respectively, demonstrating their potential as an adsorbent material for improving water quality. This work supports the development of circular economic strategies by valorizing agricultural residues while offering an effective solution to environmental pollution challenges. Full article

The simultaneous adsorption and removal of low concentrations of SO₂ and H₂S using experimental and simulation methods were investigated in this paper. The adsorption breakthrough performance of the single-component SO₂ or H₂S was determined in the activated carbon fixed-bed test. Langmuir and extended Langmuir equations in the Aspen adsorption module were used to describe the adsorption equilibrium of the single and bi-component SO₂ and H₂S system, respectively. The effects of gas hourly space velocity (GHSV) and temperature on the dynamic adsorption process of the bi-component SO₂/H₂S system were investigated. The concentration distribution and adsorption capacity of SO₂/H₂S in the bed were simulated. The results showed that the simulation for the single-component breakthrough curves of SO₂ or H₂S agreed well with the experimental data. It indicated that the model and simulation yielded engineering acceptable accuracy. For the bi-component adsorption, the competitive adsorption effect was observed, with H₂S as the weakly adsorbed component and SO₂ as the strongly adsorbed component. The dynamic adsorption process showed the sequence of initial adsorption, breakthrough, replacement, and equilibrium. The breakthrough curves were characterized by the distinct hump (roll-up) for H₂S, resulting from the replacement effect. The influence of GHSV and the temperature on the dynamic adsorption process were investigated, revealing that the lower velocity and temperature enhanced the adsorption. This work might be used for the design and optimization of adsorption bed for the simultaneous removal of SO₂ and H₂S in Claus tail gas. Full article

Addressing the removal of hazardous phenolic pollutants from water, this study introduces an eco-friendly adsorbent composed of waste-derived hydrochar immobilized in alginate beads (Alg/HC). The physicochemical properties of the Alg/HC beads were characterized using SEM, XRD, and FTIR, confirming hydrochar encapsulation and partial structural preservation. Batch studies revealed a maximum 2-nitrophenol (2-NP) adsorption capacity of 15.80 ± 0.62 mg/g at 30 mg/L of 2-NP, with kinetics best described by the Elovich and pseudo-second-order models. Freundlich isotherm fitting indicated multilayer adsorption on heterogeneous surfaces, likely governed by hydrogen bonding and π–π interactions. In a fixed-bed column system, Alg/HC beads demonstrated a continuous adsorption capacity of 6.84 ± 0.45 mg/g at 10 mg/L of 2-NP, with breakthrough behavior modeled by the Yoon–Nelson and Thomas equations. The beads maintained stable performance across four regeneration cycles using a mild water/ethanol desorption method. This work represents the first study to explore Alg/HC composites for 2-NP removal in both batch and continuous modes, demonstrating their potential as low-cost, regenerable adsorbents for tertiary treatment of phenolic industrial wastewater. Full article

The water adsorption property was shown to be the critical process limiting the thermal output in the adsorption heat storage driven by the air humidity process, which was different for the physical adsorbent and the physical/chemical adsorbent. In this study, coconut shell-based activated carbon (CAC), a hierarchically porous material that is both low-cost and mass-producible, was utilized as a physical adsorbent and as a matrix for loading calcium chloride (CAC/Ca). The incorporation of calcium chloride in CAC, with a 24% content, resulted in a 4~102% increase in water uptake capacity. The water uptake dynamics of high-thickness adsorbents are inhibited, especially for CAC/Ca. In the context of the adsorption test conducted within a fixed-bed reactor, an increase in air velocity was observed to facilitate water vapor supply, thereby culminating in higher output temperatures for both CAC and CAC/Ca, indicating a higher hydration conversion. The maximum discharge powers of CAC/Ca increased from 2 kW/m³ to 20 kW/m³, with the air velocity increasing from 0.5 m/s to 2.5 m/s. The heat-release densities of CAC and CAC/Ca at the air velocity of 2.5 m/s were 156 kJ/kg and 547 kJ/kg, respectively. Full article

Excessive phosphorus discharge from fertilizers and detergents has caused severe eutrophication in water bodies, necessitating the upgrading of efficient and cost-effective adsorbents for phosphorus removal. In this study, a novel lanthanum and extracellular polymeric substance (EPS) coprecipitation-modified ceramic (La-EPS-C-450) was developed to address the limitations of existing adsorbents. The ceramic filler served as a robust and scalable matrix for lanthanum loading, while EPS introduced functional groups and carbonate components that enhanced adsorption efficiency. The prepared adsorbent manifested a maximum phosphorus adsorption capacity of 83.5 mg P/g-La at 25 °C, with its performance well expressed by the Freundlich isotherm model, indicating that it was a multilayer adsorption process. The adsorption mechanism was driven by electrostatic attraction and ligand exchange between lanthanum and phosphate ions, forming inner-sphere complexes. The material demonstrated unfluctuating‌ performance across a pH range of 3–7 and retained high selectivity in the presence of competing anions. In practical applications, La-EPS-C-450 effectively removed phosphorus from actual river water, achieving a treatment capacity of 1800 bed volumes in a continuous-flow fixed column system. This work provides valuable insights into the progress of advanced ceramic-based adsorbents and demonstrates the potential of La-EPS-C-450 as a cost-efficient and effective material for phosphorus removal in water treatment applications. 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

The indiscriminate discharge of common dyes, such as malachite green (MG), poses significant risks to water quality and human health. To address this issue, a biochar (MBC) was synthesized from waste Myriophyllum aquaticum biomass (MAB) and further activated with KOH to produce micro-mesoporous biochar (KMBC) with enhanced adsorption efficiency. Characterization results demonstrated that KMBC exhibits a higher specific surface area (1632.7 m²/g) and a larger pore volume (0.759 cm³/g) compared to MBC. Batch adsorption experiments revealed that the adsorption process follows pseudo-second-order kinetics and the Langmuir isotherm model, with the theoretical maximum adsorption capacities of MBC and KMBC reaching 1772.3 mg/g and 2570.7 mg/g, respectively and the adsorption is a spontaneous, endothermic, and entropy-driven process. Key mechanisms involved in the adsorption process include hydrogen bonding, hydrophobic interactions, and surface complexation. Due to electrostatic attraction, selective adsorption experiments confirmed that MBC can effectively separate cationic dyes such as MG from mixed anionic-cationic systems. Dynamic experiments showed that the breakthrough curve data fit well with the Thomas model. In summary, MAB-derived biochar demonstrates significant potential for practical applications in the treatment of MG-contaminated wastewater. Full article

The reliance on greenhouse gas-emitting unrenewable energy sources such as coal, natural gas, and oil, increases climate change. Transitioning to renewable energy, such as biogas, is crucial to reducing environmental degradation and global warming. The existence of impurities such as hydrogen sulfide hampers the application of biogas. Utilizing natural resources for biogas purification is essential to improve access to clean energy for low-income communities. This study used soda ash derived from Lake Natron in Tanzania as a sorbent for H₂S removal. Effects of sorbent mass, flow rate, and particle size were investigated. Experimental data were analyzed using kinetic models, adsorption isotherms, and breakthrough curves. Soda ash of 280 μm particle size, a flow rate of 0.03 m³/h, and a mass of 75 g demonstrated the best performance, achieving an efficiency of 94% in removal and a sorption capacity of 0.02 g per 100 g in five repeated cycles. Freundlich and Jovanovich’s isotherms match the data with n = 0.4 and K_j = 0.003, respectively. Adsorption kinetics were best described by the intra-particle model (k_id = 0.14, c = 0.59 mg/g, and R² = 0.972). A breakthrough analysis indicated that the Yoon–Nelson model provided the best fit with an R² of 0.95. Soda ash from Lake Natron demonstrated great potential in biogas desulphurization, thus contributing to the production and access to clean energy. Full article

The fuel-cell (FC) power system, utilizing biohydrogen from biomass resources, is a promising alternative to fossil fuels. However, hydrogen sulfide (H₂S) in bio-syngas can severely degrade FC performance and increase environmental impact, necessitating impurity removal. This study investigates a multi-stage desulfurization process using neutralized sediment (NS) and a metal hydride (LaNi₅) as H₂S adsorbents. NS, a mining waste material, can potentially reduce environmental impact when repurposed as an adsorbent, with its performance influenced by pore configuration and Fe content. However, the purified gas does not fully meet FC fuel specifications. To address this, LaNi₅, which selectively absorbs and releases hydrogen, was incorporated to achieve higher purification levels. In our study, H₂S adsorption tests were conducted using two fixed-bed flow reactors heated to 250 °C, where a gas mixture containing 196 ppm of H₂S flowed through the system. The proposed multi-stage system achieved a breakthrough time of 182.5 h with purified gas remaining under 0.1 ppm and an adsorption capacity of 16.4 g/g-sorbent. These results demonstrate the high desulfurization performance achieved using NS and LaNi₅. Full article

The contamination of aquatic environments with hexavalent chromium (Cr(VI)) poses significant environmental and public health risks, necessitating the development of high-performance adsorbents for its efficient removal. This study evaluates the potential of green-synthesized nanoscale zero-valent iron-modified sludge biochar (TP-nZVI/BC) as an effective adsorbent for Cr(VI) removal through isothermal adsorption experiments, fixed-bed column studies, and artificial neural network (ANN) modeling. Fixed-bed experiments demonstrated that breakthrough time, exhaustion time, and unit adsorption capacity increased with bed height. Conversely, these parameters decreased with higher influent concentrations and flow rates. Breakthrough curve analysis revealed that the Thomas model provided the best fit for the experimental data (R² = 0.992–0.998). An ANN model, developed using the Levenberg–Marquardt algorithm, employed a single hidden layer with six neurons and exhibited excellent predictive performance (R² = 0.996, MSE = 0.520). The ANN model was validated for its ability to predict adsorption behavior under untested conditions, demonstrating its applicability for process optimization. This study highlights the superior performance of TP-nZVI/BC as an adsorbent for Cr(VI) and establishes a theoretical basis for optimizing and scaling up fixed-bed adsorption systems using ANN modeling. The findings provide valuable insights into the practical application of sustainable materials in environmental remediation. Full article