Continuous Fixed-bed Adsorption Research Articles

Performance of metakaolin-based geopolymer molecular sieve microspheres on dynamic recovery of Cu (II)

This study reports the in-situ transformation of geopolymers into molecular sieve using a method with mild conditions. The application of geopolymer zeolites for dynamic adsorption in continuous fixed beds has been less studied, and the application of adsorbents after adsorption has been less studied. Different metakaolin-based geopolymer molecular sieve microspheres (NaA-MSM, SOD-MSM) were prepared by in-situ conversion of metakaolin as raw material and NaOH as an alkali activator. The continuous fixed-bed adsorption performance was evaluated by varying the influent flow rate, initial metal concentration, and adsorbent dosage. The maximum adsorption capacities of NaA-MSM and SOD-MSM for Cu (II) were 698.14 and 523.84 mg·g−1, respectively. In the simulated solution of real lake water, the adsorption capacities of NaA-MSM and SOD-MSM for Cu (II) were 202.94 and 154.97 mg·g−1, respectively. The results show that the synthesized molecular sieve is an excellent adsorbent for Cu (II)-containing wastewater, and the application design of recycling heavy metals in wastewater by adsorption technology and degrading dyes has been successfully constructed.

Ionic liquid-entrapped MIL-101(Cr)-NH2 frameworks with improved phosphate control efficiency in aqueous media

In this work, different contents of 1-butyl-3-methylimidazoliumbromide ionic liquid (IL) were entrapped into amino-functionalized MIL-101(Cr) frameworks using the ship-in-a-bottle strategy to harvest novel adsorbent, namely C4mim@MIL-101(Cr)-NH2 [C4mim@MCr-NH2]. The prepared materials were characterized and exploited for phosphate removal using batch and continuous fixed-bed adsorption modes. In batch adsorption, the optimized C4mim@MCr-NH2 containing 9 wt% IL had the highest phosphate absorbing capacity of ∼ 240 mg/L at pH media ∼ 4.5, exceeding the pristine MIL-101-NH2 (∼ 91 mg/g) thanks to the synergetic effects resulting from adding adsorption sites of ILs and protonating -NH2 groups. The phosphate capture onto the C4mim@MCr-NH2 adsorbents obeyed the pseudo-second-order model, and the procedure was predominantly monitored by hydrogen bonds, electrostatic interactions, and π-cation interactions. The phosphate treatment under continuous fixed-bed conditions using PVA(4%)-mixed C4mim@MCr-NH2 pellets (∼ 3×5 mm) was described by Thomas' and Yan's column models, which showed that 1 g of the adsorbent could treat ∼26.4 L of water containing phosphate contaminant with 1 mg/L concentration. Overall, the harvested [C4mim]+[Br]--entrapped MIL-101(Cr)-NH2 showed a good ADP performance, making it a promising adsorbent for controlling phosphate in water.

Dextrin-Based Adsorbents Synthesized via a Sustainable Approach for the Removal of Salicylic Acid from Water.

Pharmaceuticals such as salicylic acid are commonly detected in wastewater and surface waters, increasing concern for possible harmful effects on humans and the environment. Their difficult removal via conventional treatments raised the need for improved strategies, among which the development of bioderived adsorbents gained interest because of their sustainability and circularity. In this work, biobased cross-linked adsorbents, synthesized via a sustainable approach from starch derivatives, namely beta-cyclodextrins and maltodextrins, were at first characterized via FTIR-ATR, TGA, SEM, and elemental analysis, showing hydrophilic granular morphologies endowed with specific interaction sites and thermal stabilities higher than 300 °C. Subsequently, adsorption tests were carried out, aiming to assess the capabilities of such polymers on the removal of salicylic acid, as a case study, from water. Batch tests showed rapid kinetics of adsorption with a removal of salicylic acid higher than 90% and a maximum adsorption capacity of 17 mg/g. Accordingly, continuous fixed bed adsorption tests confirmed the good interaction between the polymers and salicylic acid, while the recycling of the adsorbents was successfully performed up to four cycles of use.

Bacterial cellulose-based submicrobundle framework-induced hyperporous cellulose microspheres functionalized by ionic liquids for anion exchange chromatography

Ovalbumin (OVA) is widely used in food and pharmaceutical industries and can be separated using ion exchange chromatography. However, both rapid adsorption kinetics and great adsorption capacity are impeded by the nanoscale porous structures of chromatography media. Here, hyperporous cellulose microspheres (BCMs) with well-controllable micron-sized macropores are fabricated by a facile one-step pre-crosslinking strategy. Bacterial cellulose nanofibers and dissolved cellulose chains are pre-crosslinked by epichlorohydrin to form submicrobundles and generate an interconnected gel network. The preliminary gelation blocks induce a hyperporous framework during the recrystallization and assembly of regenerated cellulose. BCMs have demonstrated decreased mass transfer resistance and increased accessible active sites due to the micron-sized convective macropores (2.04 μm) and high specific surface area (194.25 m2 g−1). Cationic imidazolium ILs (AMIBr) functionalized BCMs (IL-BCMs) are prepared as anion exchangers. IL-BCMs exhibit rapid adsorption kinetics for OVA, reaching 85% of the equilibrium adsorption amount within 30 min. Additionally, IL-BCMs demonstrate endothermic chemosorption, high adsorption capacity (150.30 mg g−1, 25 °C), reusability (>85% removal efficiency after seven cycles), and selectivity towards OVA at pH 6.0. Continuous fixed-bed adsorption further suggests the practicality of IL-BCMs in ion exchange chromatography, indicating that IL-BCMs are appealing media for protein separation and purification.

Fixed bed mycofilter column optimization and performance evaluation through the removal of a food coloring agent from an aqueous solution

Mycofiltration via continuous fixed bed adsorption, helped to assess the effect of flow rate, pH, column bed height and myceliation on the sorption capacity of a mycofilter. The mycofilter (thatching straw and Pleurotus ostreatus) was cultured and loaded into polypropylene columns (2.5 × 12 cm) to bed heights of 2 and 4 cm. A food color solution was passed through at different pH (2 and 7.5) and flow rates (0.25 ml/min and 2 ml/min). The filtrate was collected and measured at time intervals. Under constant flow rate and solution pH, the 4 cm bed adsorbed 8 times the inlet amount of food color compared to 1.6 times only for the 2 cm bed. More food color was adsorbed with the higher flow rate (10 times the inlet concentration). Adsorption was only observed in the solution with pH = 2. The control filter (without mycelia) adsorbed 3-fold less than the mycofilter. The experimental data best fitted into the Thomas model (compared to the Yoon-Nelson model) which showed that an increase in bed height caused an increase in adsorption capacity (qTH), and that an increase in flow rate resulted in an increase in Thomas rate constant (KTH). FTIR analyses of the mycofilter revealed amide, hydroxyl, and chitin groups possibly involved in adsorption processes. Our fixed bed mycofilter optimally removed food color from aqueous solutions, in high bed height and flow rate, and low pH conditions.

Continuous fixed-bed adsorption of reactive azo dye on activated red mud for wastewater treatment-Evaluation of column dynamics and design parameters

Continuous adsorption of Remazol Brilliant Blue (RBB) dye in water onto sulfuric acid activated red mud (CATRM) in a fixed bed column was investigated. Breakthrough curves were obtained experimentally by varying the bed height (Z), influent flow rate (Q), and dye concentration(C0). The adsorption efficiency in the removal of RBB was favored at lower C0, higher Z, and lower Q. The maximum adsorption capacity of the activated red mud bed in the column was obtained at C0 = 70mg/L, Z = 8cm, and Q = 5mL/min and found to be 106mg/g. Important parameters of column dynamics and design such as mass transfer zone (MTZ) and length of unused bed (LUB) were evaluated from the breakthrough curves. The MTZ and LUB have varied with varying Z, which indicated the existence of nonideal conditions. Thomas model was found to be valid to predict the column dynamics and the model parameters were evaluated. Bed depth service time (BDST) model parameters were evaluated to facilitate the determination of packed bed height for the design of packed bed adsorption column. The bed could be regenerated with NaOH solution with desorption efficiency decreasing from 83.8 to 55.72% from the first to third cycle. A fixed bed of CATRM can be effectively used for continuous dye removal from industrial wastewater.

Batch and continuous fixed-bed adsorption of antibiotics from aqueous solution using stearic acid-activated carbon composite

Batch and continuous fixed-bed adsorption of antibiotics from aqueous solution using stearic acid-activated carbon composite

Simultaneous removal of heavy metals and dye from wastewater: modelling and experimental study.

In this work, heavy metals were removed simultaneously using wheat bran as an adsorbent. For batch experiments, the Box-Behnken design of response surface methodology was used and the effect of dye on metal removal was analysed. It has been observed that the presence of dye has reduced the removal of each metal in the range of 100-20% with no appreciable reduction in dye adsorption. The optimum pH, temperature, and adsorbent dose were found to be 7.59, 33.23 °C, and 2.90 g/L, respectively, for 79.70% chromium, 99.9% cadmium and 87.27% copper removal. It was found that Langmuir isotherm fits well with the experimental data (RMSE value up to 0.033). The maximum adsorption capacity obtained for copper, chromium, cadmium and dye were 2.17 mg/g, 1.76 mg/g, 1.52 mg/g and 3.215 mg/g, respectively. The continuous study was performed for parameters, i.e. bed height (0.15-0.45 m), flow rate (5-15 mL/min) and initial metal concentration (100-500 mg/L). In continuous study, dye acted as an interfering species and as a result breakthrough and exhaustion time decreased. The modelling and simulation of continuous adsorption process were performed. A dynamic mathematical model was developed for continuous fixed bed adsorption column to compare the breakthrough curve with experimental results.

A Continuous Fixed Bed Adsorption Process for Fez City Urban Wastewater Using Almond Shell Powder: Experimental and Optimization Study

This study deals with the valorization of a biomaterial, almond shell, for the treatment of urban effluents of the city of Fez by a fixed bed column adsorption process. A parametric analysis of the process is carried out with conditions such as particle size, pH and height of the adsorbent bed to evaluate the optimal removal percent and obtain an optimal removal capacity of the adsorbent load. Characterization of the adsorbent prior to continuous adsorption was carried out by X-ray diffraction, Fourier-transform infrared spectrometry and scanning electron microscopy. The adsorption treatment seems to be influenced by certain parameters, such as the particle size of the biomaterial used, the height of the adsorption bed and the pH. The results suggest that this biomaterial can be used as a less expensive, available, biodegradable and very effective adsorbent to eliminate the load of urban waters on a small scale and why not on a large scale to replace chemicals in the treatment and to recover waste such as almond shell. The parameters measured reached maximum values varying between 82% for COD, 79% for EC and 71% for nitrite under well-defined operating conditions, with a particle size of 0.063 mm, a height column height of 7 cm and a pH of 6.5.

Silver ions and silver nanoparticles removal by coffee derived biochar using a continuous fixed-bed adsorption column

Even low concentration monovalent silver (Ag+) and silver nanoparticles (Ag NPs) are emerging environmental threats, seeking an eco-friendly and cost-effective continuous treatment process to mitigate their pollution. In this study, an attempt has been made to investigate the potential of spent coffee grounds (SCGs) biochar in a fixed-bed column, to remove silver ions and silver nanoparticles from wastewater. A series (adsorption and desorption) of fixed-bed column experiments were performed under different operating conditions to determine the breakthrough curves (BTCs) and understand the effect of initial concentration (50–100 mg/L), the quantity of biochar (0.5–1 g), and the form of silver Ag+ and Ag NPs on biochar removal capacity. Thomas and Yoon-Nelson models were applied to simulate different column parameters, such as breakthrough time, saturation time, the volume of treated effluent, and percentage of removal. These simulated results could assist in the scale-up of the process for an actual industrial operation. Experimental data showed good agreement with both Thomas and Yoon-Nelson models, where the simulated values were closely matched with the experimental values. Biochar was collected after the adsorption and characterised to confirm the morphology, crystal structure, and ionic state of silver. The saturated column was regenerated by 0.05 M HNO3 as eluent and used at least 3 times with 15% capacity loss compared to initial performance, which demonstrated the viability and effectiveness of the biochar adsorption process.

Evaluation of the performance of an agricultural residue Cyamopsis tetragonolobus (guar gum) in toxic paint industry, effluent treatment using continuous fixed-bed adsorption column

Evaluation of the performance of an agricultural residue Cyamopsis tetragonolobus (guar gum) in toxic paint industry, effluent treatment using continuous fixed-bed adsorption column

Silver Ions and Silver Nanoparticles Removal by Coffee Derived Biochar Using a Continuous Fixed-Bed Adsorption Column

Silver Ions and Silver Nanoparticles Removal by Coffee Derived Biochar Using a Continuous Fixed-Bed Adsorption Column

Batch and continuous fixed bed adsorption of heavy metals removal using activated charcoal from neem (Azadirachta indica) leaf powder

The present investigate was intended for adsorption of heavy metals i.e. Pb, Cu, Cr, Zn, Ni and Cd onto activated charcoal prepared from neem leaf powder (AC-NLP) using batch and column studies. Batch adsorption was performed using different variables like adsorbent dose, temperature and contact duration. Thermodynamic analysis of batch treatment concluded that adsorption is thermodynamically feasible and endothermic. This adsorption followed the Pseudo second-order kinetic model derived from correlation coefficient values of chemical kinetic studies. For column study, interpretation of breakthrough curves and parameters were conducted by varying flow rate, initial concentration and bed height; and reveal that optimum conditions were lower flow rate (5 mL/min) and lower initial concentration (5 mg/L) and higher bed height (20 cm). Comparisons of batch and column study through isotherm models were evaluated and column study is more preferred than batch treatment. Maximum Thomas adsorption capacity was achieved upto 205.6, 185.8, 154.5, 133.3, 120.6, 110.9 mg/g for Pb, Cu, Cd, Zn, Ni and Cr respectively. This removal pattern is elucidated by metal ionic properties. Various adsorbing agents such as acids and bases were utilized for adsorption–desorption of AC-NLP.

Continuous fixed-bed adsorption of Mo(VI) from aqueous solutions by Mo(VI)-IIP: Breakthrough curves analysis and mathematical modeling

In the search for cost-effective and highly selective adsorbents for the removal of Mo(VI) from aqueous systems, the Mo(VI)-imprinted polymer (Mo(VI)-IIP) has been identified as a potential candidate. In this study, we investigated the performance of Mo(VI)-IIP in the packed fixed-bed column, to assess its potential for industrial extension. In a laboratory-scale fixed-bed column, the effluent Mo(VI) concentration versus time span (i.e., breakthrough curves) were determined for various operational parameters, such as flow rate (5, 7 and 9 mL min−1), influent Mo(VI) concentrations (50, 70 and 90 mg L−1), bed depths (0.5, 1 and 1.5 cm) at pH 3. The breakthrough curve of various bed height demonstrated that the life span of the continuous fixed-bed column will be extended with a longer bed column. The maximum capacity and total metal removal reached 94.3 mg g−1 and 80.2% respectively, using 1.5 cm bed depth, 7 mL min−1 flow rate and 50 mg L−1 influent Mo(VI) concentration. The growth of influent Mo(VI) concentration and flow rate caused the earlier exhaustion time in the column. The experimental data were fitted with well-established mathematical models such as Yoon-Nelson, Thomas, and Adams-Bohart. The results were best-fitted with Thomas and Yoon-Nelson models (with correlation coefficient R2 ≥ 0.99) rather than the Adams-Bohart model for all conditions.

Authors’ response to comments on Ang et al. “Breakthrough analysis of continuous fixed-bed adsorption of sevoflurane using activated carbons”

Authors’ response to comments on Ang et al. “Breakthrough analysis of continuous fixed-bed adsorption of sevoflurane using activated carbons”

Comments on “Breakthrough analysis of continuous fixed-bed adsorption of sevoflurane using activated carbons”

This communication discusses the fixed bed modeling results of the recent paper published by Ang et al. (2020) in this journal.

Continuous Fixed-Bed Adsorption of Heavy Metals Using Biodegradable Adsorbent: Modeling and Experimental Study

AbstractIn this study, a continuous fixed-bed column was investigated for heavy metal removal using modified wheat bran as adsorbent. Clay and chitosan were used as binders with the adsorbent to pr...

Breakthrough analysis of continuous fixed-bed adsorption of sevoflurane using activated carbons

The inhalational anaesthetic agent – sevoflurane is widely employed for the induction and maintenance of surgical anaesthesia. Sevoflurane possesses a high global warming potential that imposes negative impact to the environment. The only way to resolve the issue is to remove sevoflurane from the medical waste gas before it reaches the atmosphere. A continuous adsorption study with a fixed-bed column was conducted using two commercial granular activated carbons (E-GAC and H-GAC), to selectively remove sevoflurane. The effect of bed depth (Z, 5–15 cm), gas flow rate (Q, 0.5–6.0 L/min) and inlet sevoflurane concentration (C0, ∼55–700 mg/L) was investigated. E-GAC demonstrated ∼60% higher adsorption capacity than H-GAC under the same operating conditions. Varying the levels of Z, Q and C0 showed significant differences in the adsorption capacities of E-GAC, whereas only changing the C0 level had significant differences for H-GAC. Three breakthrough models (Adams-Bohart, Thomas, and Yoon-Nelson) and Bed-depth/service time (BDST) analysis were applied to predict the breakthrough characteristics of the adsorption tests and determine the characteristic parameters of the column. The Yoon-Nelson and Thomas model-predicted breakthrough curves were in good agreement with the experimental values. In the case of the Adams-Bohart model, a low correlation was observed. The predicted breakthrough time (tb) based on kinetic constant (kBDST) in BDST analysis showed satisfactory agreement with the measured values. The results suggest the possibility of designing, scaling up and optimising an adsorption system for removing sevoflurane with the aid of the models and BDST analysis.

Removal efficiency of metallic trace elements by slow sand filtration: study of the effect of sand porosity and diameter column

The removal potential of slow sand filtration was investigated in a continuous fixed-bed adsorption system as a replacement of current expensive methods for decontaminating water. This study was achieved on Tensift River water contaminated by metallic trace elements (Cd, Cu, Pb and Zn) that received directly wastewater of industrial unit of Zn and Pb extraction of Draa Lasfar mine near Marrakech city in Morocco. Results showed that removal efficiency of sand used in this process depends greatly on both sand porosity and diameter of column. Thus, higher decontamination efficiency was noted at higher column’s diameter and higher sand porosity. These results can be justified by the fact that higher diameter of column and sand porosity engenders a higher mass transfer zone due to an increase coefficient diffusion and longer contact time as well as shallow adsorption zone with exposition of new active binding sites to metallic pollutants on the sand surface. This result provides a larger service area leading to an increase in the volume of the treated solution water. In order to describe the column adsorption process used in slow sand filtration, it is crucial to predict the breakthrough curve (concentration-like profile) and adsorption capacity of sand under the given set of operating conditions (sand porosoty and diameter of column), based on the assumption that this process follows Langmuir kinetics of adsorption–desorption with no axial dispersion which describes that the rate driving force obeys the 2nd order irreversible reaction kinetics.

Altered neural sensitivity to faces and dynamic gaze in 8-month-old infants with later autism spectrum disorder

In this study, oxidative-adsorptive desulfurization technology was applied to raw diesel containing 1480.4 ppm sulfur. For oxidative desulfurization, the oxidant and catalyst were hydrogen peroxide and phosphotungstic acid, respectively. Two types of continuously mixed reactors: (1) continuous stirred tank reactor (CSTR) and (2) in-line mixer were evaluated under varying reaction temperature, mixing speed and diesel flow rate. For the in-line mixer system, the mixer speed and the flow rates for diesel and oxidant were modeled and optimized using Box-Behnken design of the response surface methodology. Optimization of process parameters resulted in sulfur removal of 85.90% at 18,000 rpm mixer speed, 500 mL min−1 diesel flow rate and 300 mL min−1 H2O2 flow rate. In the subsequent adsorptive desulfurization experiments, continuous fixed-bed adsorption using alumina removed 92.81% sulfur from treated diesel fuel thereby producing low-sulfur diesel that is within the allowable limit of Euro IV standard.