Search Results (79)

Numerous studies have been conducted employing various techniques to remove pollutants from water bodies. Among these techniques, adsorption a surface phenomenon that utilises adsorbents derived from agricultural residues has shown considerable potential for the removal of contaminants such as heavy metals. However, most of these investigations have been carried out at the laboratory scale, with limited efforts directed towards predicting the performance of these systems at an industrial level. Accordingly, the present study aims to model a packed bed column at industrial scale for the removal of Pb(II) and Ni(II) ions from aqueous solutions, employing biomass derived from oil palm residues as the adsorbent material. To achieve this, Aspen Adsorption was used as a modelling and simulation tool to evaluate the impact of bed height, inlet flow rate, and initial concentration through a parametric assessment. This evaluation incorporated the Freundlich, Langmuir, and Langmuir–Freundlich isotherm models in conjunction with the Linear Driving Force (LDF) kinetic model. The results indicated that the optimal operating parameters included a column height of 5 m, a flow rate of 250 m³/day, and an initial metal concentration of 5000 mg/L. Moreover, all models demonstrated removal efficiencies of up to 94.6% for both Pb(II) and Ni(II). An increase in bed height resulted in longer breakthrough and saturation times but led to a reduction in adsorption efficiency. Conversely, higher flow rates shortened these times yet enhanced efficiency. These findings underscore the potential of computational modelling tools as predictive instruments for evaluating the performance of adsorption systems at an industrial scale. Full article

The objective of this study was to model an adsorption column bed with biomass residues using computational software to remove Pb (II) at the industrial level and analyse the effects of parametric variation. For this purpose, several simulations of the adsorption column were performed using Aspen Adsorption software, evaluating the effects of varied height, inlet flow rate, and initial concentration on the adsorption process performance. The Langmuir II and Freundlich models are established as isotherm models, and the linear driving force (LDF) model is established as the kinetic model. The findings showed that Freundlich–LDF obtained efficiencies of up to 99.9% and Langmuir II–LDF efficiencies of up to 99.7%. The optimal simulation conditions were a column height of 4 m, an initial Pb (II) concentration of 3000 mg/L, and an inlet flow rate of 250 m³/d. This study presents a novel engineering approach to predict the potential performance of columns packed with organic waste-derived biomasses in multi-scale Pb (II) removal using computer-aided engineering tools. Full article

In this study, a novel adsorbent was developed by synthesizing Zn-Al layered double hydroxide (LDH) incorporated with silver nanoparticles (Ag-NPs), and its effectiveness in bromide removal from aqueous solutions was systematically evaluated. The X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) analyses confirmed the integration of Ag-NPs within the LDH, ensuring uniform chemical composition and structural integrity. A series of controlled batch trials, each varying a single parameter (adsorbent dose, contact time, or temperature) confirmed that over 95% of bromide (initially 5320 μg/L) was removed under optimized conditions. LDH/Ag-NPs exhibited superior performance, with kinetics well described by a second-order reaction model. Thermodynamic analysis confirmed the spontaneous and exothermic nature of bromide adsorption, with ΔG° values ranging from −2.03 to −0.73 kJ/mol as the temperature increased from 22 °C to 52 °C. In continuous-flow experiments, packed-bed column tests illustrated that LDH/Ag-NPs maintained more effective bromide removal than LDH alone over extended periods. Conductivity measurements further supported this enhancement, with LDH/Ag-NPs reducing final conductivity to 139 µS/cm, compared to 212 µS/cm for LDH. Furthermore, this study revealed the notable antimicrobial activity of LDH/Ag-NPs, as evidenced by a significant reduction in bacterial growth compared to LDH alone, highlighting its dual functionality for both bromide adsorption and water disinfection. Overall, the incorporation of Ag-NPs into LDH offers a promising strategy for developing multifunctional and sustainable water treatment systems. Full article

Cuboid packed-bed devices developed for chromatographic separation typically have shorter bed heights and larger cross-sectional areas than their equivalent cylindrical columns. These devices can be operated at low back pressures and give comparable or even better resolution than their equivalent columns. However, the bed height of a cuboid packed-bed device could potentially affect its separation performance. To examine this, three devices having 5, 10 and 19.5 mm bed heights were fabricated and packed with the same resin media. A mathematical model was first developed to predict the effect of bed height on the performance of these cuboid devices. This prediction was performed based on the residence time heterogeneity (RTH) in these devices, which increased slightly as the bed height was decreased. However, this was not likely to affect the separation efficiency very significantly. The relative performances of these three cuboid devices were then compared based on the resolution obtained during ion-exchange chromatography of multi-protein mixtures. As predicted by the mathematical model, the loss in resolution due to the decrease in bed height was relatively small (0.83 to 0.73 in binary protein separation). Also, this loss could easily be compensated for by slightly lowering the flow rate or by extending the elution gradient. The results discussed in this paper demonstrate that with cuboid packed-bed devices, the dimensions could be altered in a reasonably flexible manner without adversely affecting separation performance. Such flexibility is advantageous from the point of view of process design and optimization, which is critically important for developing large-scale processes for the purification of biologics. Full article

This work studies heat transport in the fluid–solid interface of a packed bed to demonstrate the feasibility of preheating lumpy manganese ores to 600 °C with air at 750 °C. Preheated manganese ores aim to reduce furnace energy consumption during smelting in submerged arc furnaces to produce manganese ferroalloys. The preheating process was experimentally studied in a pilot-scale shaft-type column. The air was heated to 750 °C and used as a heat transfer fluid to heat a packed bed of manganese ore from room temperature to 600 °C. A one-dimensional three-phase (manganese ore, air, and the column wall) numerical model was developed to simulate the preheating process. The energy balance of the three phases was carried across a finite volume using the volume averaging technique. Numerical schemes were applied, and non-dimensional parameters were introduced before applying numerical techniques to solve the systems of linear equations. Python NumPy and SciPy modules were used for the computation of the packed bed temperature fields. Temperature data from the preheating tests were used for model validation. The model prediction of the transfer process agreed with experimental results to least square errors of less than 25 °C. Data from experimental measurements confirmed the feasibility of using air as the transfer fluid in the preheating of manganese ore. Detailed temperature field data generated from the model can be used for the sizing of manganese ore preheating units and the implementation of control protocols for the preheating process. Full article

This study was carried out to appraise the groundwater fluoride removal effectiveness of Al-Fe oxide-infused diatomaceous earth (DE) in a continuous-flow fixed-bed column. The adsorbent was optimally synthesized and then characterized. A glass column designed for the experiment was packed with the test adsorbent at specific doses. The effects of flow rate, influent fluoride concentration and bed height (adsorbent dose) on fluoride removal were evaluated by fixing the value of a parameter while varying the others. The breakthrough volume was the volume of treated water obtained until the concentration of fluoride in the treated water reached 1.5 mg/L, which is the World Health Organization’s maximum limit of fluoride in drinking water. The maximum breakthrough volume obtained in this study was 118.2 mL under the optimum conditions of influent F⁻ concentration = 5 mg/L, 1 g of adsorbent with an initial bed height = 7.5 cm and a flow rate = 1.97 mL/min. Channeling and the presence of $\mathrm{P}{\mathrm{O}}_4^{3-}$ as a co-existing anion were limiting factors for the attainment of the breakthrough volume for groundwater defluoridation. Further work is encouraged to investigate a suitable binder that can hold the adsorbent particles firmly together, is not water-soluble, but remains water-permeable when dry. The resulting solid mass could then be pulverized into granules whose weight and rigidity would make them less susceptible to the channeling effect in the column. Full article

Biodiesel produced via oil transesterification often contains metallic impurities, such as copper, which affects its quality and engine performance. This study explores the use of activated carbon prepared from spent coffee grounds to remove copper from biodiesel. Activated carbon samples were prepared via biomass pyrolysis and chemical activation with KOH and HNO₃. The optimal conditions for copper adsorption were determined using a Taguchi L9 design. Maximum adsorption capacities were 13.4 and 17.3 mg/g at 30 and 40 °C, respectively, in batch adsorbers. In packed-bed columns, the axial dispersion reduced the adsorption efficiency obtaining bed adsorption capacities from 1.9 to 5.1 mg/g under tested experimental conditions. Adsorbent characterization and adsorption modeling indicated that copper removal was driven by multi-cationic interactions, where carboxylic groups from carbon surface acted as key active sites. The new adsorbent outperformed commercial bone char, making it a cost-effective alternative to improve biodiesel production contributing to the energy matrix diversification. Full article

An important contributor to environmental degradation is the industrial revolution, which has occurred in developed and developing nations. The present investigation aimed to tackle the escalating apprehensions regarding the discharge of various types of dyes from the paint, textile, and dyeing sectors. This research focuses on the adsorption performance of a newly developed system that uses cotton pod shell powder (CPSP) as a novel adsorbent to remove dye industry wastewater. The system has been designed, manufactured, and tested to be operationally efficient and cost-effective. The CPSP is a new adsorbent with desirable properties such as favorable functional groups and porosity, and analysis of its functional groups and porous nature was carried out using FTIR and SEM. The experimental data from the developed system showed that inlet dye concentration (50, 100, and 150 ppm), bed height (10, 20, and 30 cm), and flow rate (10, 15, and 20 mL/min) significantly affect the adsorption of dye industry wastewater by CPSP. Breakthrough curves were shown to be flow rate and bed depth dependent, according to the data. Significant experimentation was conducted on the developed system, and under optimized conditions. It was shown that the breakthrough point was affected by both bed height and flow rate. Evidence suggested that decreasing flow rate and concentration and raising bed height led to improved breakthrough and exhaustion times. At a concentration of 100 ppm and a flow rate of 15 mL/min, a bed depth of 20 cm was found to have the highest absorption capacity. Adam-Bohart, bed depth service time, and Yoon-Nelson models were utilized to examine the adsorption data. The results revealed that the developed system is effective, and the data obtained in this work can provide optimum operating conditions, suggesting its scalability to an industrial level for dye removal from wastewater by adsorption using CPSP as a novel adsorbent. Full article

The present work analyzes the behavior of an activated carbon fabricated from almond shells for the removal of cationic dyes (methylene blue, MB, and malachite green, MG) by adsorption from aqueous solutions. The carbonized precursor was activated with KOH at a 1:2 (w/w) ratio with the objective of increasing both the surface area and the pore volume. Both non-activated and activated carbon were characterized in different aspects of interest in dye adsorption studies (surface structure, point of zero charge, specific surface area, and pore size distribution). The effect of the dye’s initial concentration and adsorbent dosage on dye removal efficiency and carbon adsorption capacity was studied. Adsorption kinetics were analyzed under different experimental conditions, and different models were assayed to determine the adsorption mechanism. Dye adsorption in the adsorbent surface could be considered the rate-limiting step. Different adsorption equilibrium models were evaluated to fit the experimental data. This adsorbent allowed us to reach high Langmuir adsorption capacity for both dyes (MB: 341 mg·g⁻¹, MG: 364 mg·g⁻¹ at 25 °C and 0.5 g·L⁻¹). Moreover, kinetic and equilibrium adsorption data have been used to simulate breakthrough curves in a packed-bed column using different conditions (bed length, liquid flowrate, and dye initial concentration). The simulation results showed that almond shell activated carbon is a suitable adsorbent for methylene blue and malachite green removal from wastewater. Full article

Continuous flow technologies have become increasingly important for biocatalytic processes. In this study, we present the application and modelling of covalently immobilised N-acetylglucosamine 2-epimerase and N-acetylneuraminic acid lyase in packed bed reactors for the synthesis of N-acetylneuraminic acid. The immobilised enzymes were stable under continuous flow process conditions with half-life times of >28 d (epimerase immobilised on hexamethylamino methacrylate HA403/M) or 58 d (lyase immobilised on dimenthylamino methacrylate ECR8309M), suitable for continuous flow applications. Kinetic studies revealed Michaelis–Menten kinetic behaviour for both enzymes. The kinetic parameters and the inhibitions were analysed under continuous flow conditions and were integrated into a process model using Python. The model was validated by varying flow rates, the mass of immobilised enzymes and the reactor dimensions and shows a low error compared to the measured data. An error accuracy of 6% (epimerase) or 9% (lyase) was achieved. The product concentrations of the enzyme cascade at the end of the packed bed reactor can be predicted with an accuracy of 9% for the calculation of a large column (84.5 mL) or of 24% if several small columns (2.5 mL, 0.8 mL) are connected in series. The developed model has proved to be valid and will be used to optimise the process with respect to substrate concentrations, reactor dimensions and flow rate. Full article

The application of continuous fermentation with immobilized cells in brewing is a challenge because of problems with carrier selection and reactor design, which have economic impacts on the beer produced. Moreover, immobilization alters yeast physiology, which significantly affects beer flavor and aroma. Therefore, the aim of this study was to investigate the feasibility of a continuous fermentation system, consisting of a packed bed column bioreactor, containing lager brewing yeast, immobilized in alginate–chitosan microcapsules with a liquid core, in the primary beer fermentation. The results showed that the system entered in a stationary mode on the 3rd day and worked stably in this mode for 6 days. The “green” beer was taken at every 24 h at the output of the reactor and used for secondary fermentation with the yeast cells leaked from the capsules during the primary fermentation. The extract consumption, ethanol production, and pH change during primary and secondary fermentation were investigated. Some of the secondary yeast metabolites such as vicinal diketones, higher alcohols, esters, and aldehydes in “green” and final beers were determined and it was found that the flavor profile of the final beer was comparable to two industrially produced Bulgarian beers. Full article

This study explored the adsorption of acetaminophen and caffeine using CO₂-activated biochar (BT-CO₂) and hydrochar (HT-CO₂) derived from Tingui shell biomass. The experimental data from kinetic and equilibrium adsorption tests were employed in batch and fixed-bed systems. In the batch system, a specific amount of the adsorbent was added to a known volume of the solution, and the mixture was agitated for a set period to allow adsorption to occur. In the fixed-bed system, the solution was passed through a column packed with the adsorbent, allowing for continuous adsorption. These systems pave the way for future research. The findings revealed that HT-CO₂ exhibited a greater surface area and a higher presence of oxygen-containing functional groups than BT-CO₂. These functional oxygen groups had a notable impact on the adsorption capacity of the adsorbents for pharmaceutical substances. In the batch systems, BT-CO₂ demonstrated a maximum adsorption capacity of 221.4 mg g⁻¹ for acetaminophen and 162.7 mg g⁻¹ for caffeine, while HT-CO₂ exhibited higher capacities of 383.2 mg g⁻¹ for acetaminophen and 189.7 mg g⁻¹ for caffeine. In the fixed bed configuration, HT-CO₂ displayed a maximum adsorption capacity of 82.2 mg g⁻¹ for acetaminophen and 45.60 mg g⁻¹ for caffeine. The predominant mechanisms involved in the removal of acetaminophen and caffeine were identified as H-bonding and π-π bonds. These results underscore the promising potential of these carbons as effective adsorbents for treating water contaminated with pharmaceutical residues, inspiring further exploration in this field and offering hope for the future of water treatment by providing a solid foundation for future research and development. Full article

The Elastic Catalytic Foam-bed Reactor (EcFR) technology was used to enhance a model catalytic hydrogenation reaction by improving gas–liquid mass transfer. This advanced technology is based on a column packed with a commercial elastomeric polyurethane open-cell foam, which also acts as a catalyst support. A simple and efficient crankshaft-inspired system applied in situ compression/relaxation movements to the foam bed. For the first time, the catalytic support parameters (i.e., porosity, tortuosity, characteristic length, etc.) underwent cyclic and controlled changes over time. These dynamic cycles have made it possible to intensify the transfer of gas to liquid at a constant energy level. The application chosen was the selective hydrogenation of phenylacetylene to styrene in an alcoholic solution using a palladium-based catalyst under hydrogen bubble conditions. The conversion observed with this EcFR at 1 Hz as cycle frequency was compared with that observed with a conventional Fixed Catalytic Foam-bed Reactor (FcFR). Full article

Fugitive methane emissions from the mining industry, particularly so-called ventilation air methane (VAM) emissions, are considered among the largest sources of greenhouse gas (GHG) emissions. VAM emissions not only contribute to the global warming but also pose a significant hazard to mining safety due to the risk of accidental fires and explosions. This research presents a novel approach that investigates the capture of CH₄ in a controlled environment using 1-butyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide [BMIM][TF₂N] ionic liquid (IL), which is an environmentally friendly solvent. The experimental and modelling results confirm that CH₄ absorption in [BMIM][TF2N], in a packed column, can be a promising technique for capturing CH₄ from point sources, particularly the outlet streams of ventilation shafts in underground coal mines, which typically accounts for <1% v/v of the flow. This study assessed the effectiveness of CH₄ removal in a packed bed column by testing various factors such as absorption temperature, liquid and gas flow rates, flow pattern, packing size, desorption temperature, and desorption pressure. According to the optimisation results, the following parameters can be used to achieve a CH₄ removal efficiency of 23.8%: a gas flow rate of 0.1 L/min, a liquid flow rate of 0.5 L/min, a packing diameter of 6 mm, and absorption and desorption temperatures of 303 K and 403.15 K, respectively. Additionally, the experimental results indicated that ILs could concentrate CH₄ in the simulated VAM stream by approximately 4 fold. It is important to note that the efficiency of CH₄ removal was determined to be 3.5-fold higher compared to that of N₂. Consequently, even though the VAM stream primarily contains N₂, the IL used in the same stream shows a notably superior capacity for removing CH₄ compared to N₂. Furthermore, CH₄ absorption with [BMIM][TF₂N] is based on physical interactions, leading to reduced energy requirements for regeneration. These findings validate the method’s effectiveness in mitigating CH₄ emissions within the mining sector and enabling the concentration of VAM through a secure and energy-efficient procedure. Full article

Abundant, easily accessible, and low-cost agro-industrial residues represent attractive alternatives for removing emerging contaminants from water. In this work, the aqueous adsorption of caffeine/triclosan onto rice husk (RH) was studied in batch and continuous processes. For this purpose, adsorbents with three particle size ranges (120–150, 300–600, 800–2000 µm) were prepared and evaluated. The composition, structure, surface morphology, functionality, and specific surface area of the RH biosorbents were determined. This characterization revealed that RH primarily consists of lignin, cellulose, and hemicellulose, making up to 80.1% of its composition. RH also exhibited an irregular surface, with several functional groups (OH, C=O, CH, C=C, C-OH), and a relatively small specific surface area (1.18 m²/g). Batch tests were carried out using different RH sizes, doses (1–50 g/L), and contact times (5–300 min), using 20 mL of caffeine/triclosan solutions (30 mg/L). Tests were conducted to fit the most adequate kinetics and isotherm models. The optimal doses (g/L) for caffeine and triclosan removal were 4.5 and 1.5 with small RH, 8.5 and 2.5 with medium RH, and 50.0 and 10.0 with large RH, respectively. The optimal contact times for all three particle sizes were 180 and 60 min. Triclosan removal was greater than that of caffeine (2.5–25.5%) with all three particle sizes, requiring less adsorbent (2.5–5.0 times) and shorter times (3 times). The experimental data fit better the Sips isotherm and Elovich kinetics models. The small (120–150 µm) particles achieved the highest caffeine/triclosan batch adsorption capacities (6.3/28.6 mg/g). Continuous tests were performed on fixed-bed columns of 1 cm in diameter, packed with 4, 5, and 8 cm of RH, operated with hydraulic loading rates between 2 and 4 m³/m²day. Small particles also reached the highest adsorption capacity in the removal of caffeine (352.7 mg/L) and triclosan (3797.2 mg/L), and the experimental data were well-fitted to the Bohart–Adams model. The research results not only demonstrate the effective removal of contaminants but also illustrate the versatility and applicability of rice husk in various conditions and systems. Full article