Fixed Bed Height Research Articles

Pathways and enhancement strategies for magnesium hardness removal in modified induced crystallization softening

Elevated levels of total hardness in drinking water can readily result in scaling, which poses a threat to both the safety of water quality and the convenience of its use. While there is a wealth of research on the removal of calcium hardness, there is a dearth of studies focusing on the removal of magnesium hardness. In light of this, the present study employs modified induced crystallization softening (MICS) to delineate the removal pathways and mechanisms of magnesium hardness, and to investigate viable methods for its enhancement and application. Our research has determined that magnesium hardness can be effectively removed from water through the MICS, with the dosage of softening agents (NaOH) being a significant factor that influences this removal, whereas the fixed bed height within the fluidized bed exerts minimal impact on the process. In the low-dose stage (less than 250 mg/L), when the pH is below 10.0, up to 20% of magnesium hardness can be removed, predominantly through the crystallization of (Ca0.936Mg0.064)CO3. As the dosage increases to the moderate stage (250–400 mg/L), the conversion of excess bicarbonate (HCO3−) to carbonate (CO32−) in the water hinders further removal of magnesium hardness. In the high-dose stage (exceeding 400 mg/L), when the pH rises above 10.5, the removal rate of magnesium hardness can be enhanced to over 75%, with the crystallization of Mg(OH)2 being the primary removal mechanism. Density functional theory calculations, along with molecular dynamics simulations of cohesive energy and bond energy, substantiate the feasibility of the identified magnesium removal pathways. The addition of coagulants (FeCl3) and an decrease in the up-flow velocity can further augment the removal efficiency of magnesium hardness by promoting the crystallinity of Mg(OH)2 during the high-dose stage (exceeding 400 mg/L). In practical engineering applications, the strategic control of softening agent dosages enables the achievement of varying levels of magnesium hardness removal, tailored to specific water quality requirements.

Adsorption of Heavy Metals on Alkali-Activated Zeolite Foams.

Elevated concentrations of heavy metals in natural waters can cause significant ecological problems. It is therefore essential to ensure their removal from any water discharged into the environment immediately, especially in case of an accident, where there is a risk of releasing large quantities or high concentrations. The aim of this paper is to test a newly developed adsorbent for the removal of heavy metals from aqueous solutions-in particular, it is very fast adsorption, and thus efficiency, during clean-ups. The alkali-activated foamed zeolite adsorbent was laboratory-prepared and -tested in both batch and flow-through arrangements on single and multi-component solutions and compared with natural zeolite. The experimental setup for batch adsorption consisted of a set of samples and solutions containing iron, cobalt, manganese, zinc and nickel. The samples were put on a horizontal shaker with a 500 mg adsorbent loading in a 50 mL solution. The column adsorption experimental setup consisted of a glass column with an inside diameter of 15 mm and a bed length of 165 mm. A measured amount of each adsorbent was added to the column to achieve a filter fixed-bed height of 160 mm. The high efficiency of the tested adsorbent on various heavy metals was confirmed. The adsorbent has a high potential for use in decontamination processes, water protection and landscape revitalization. Due to its rapid precipitation and subsequent fixation of metal cations in the form of insoluble oxide or hydroxide, it can be used as an emergency adsorbent, the great advantage of which is its low production cost and natural origin.

Effect of Horizontal Tube Position on Wall-to-Bed Heat Transfer in Air-Solid Fluidized Bed of Large Particles

Fluidized beds are extensively used in a variety of industrial applications, such as heat recovery systems, coal combustion, and solid particle drying. The effect of the position of the heat transfer tube on heat transfer from a horizontal bare tube in a 150 mm square cross-section fluidized bed containing large particles, ragi, and mustard is investigated. The influence of varying fluidizing velocities on heat transport is also examined for a fixed bed height of the large particles. When the position of the tube from the distributor plate was increased in 0.028m increments from 0.52 m to 0.080 m and then to 0.108 m, the heat transfer coefficient was reduced. Due to enhanced fluidization, all bed heights yielded almost comparable heat transfer coefficient values at velocities exceeding 1 m/s, 170 and 160 W/m2K for ragi and mustard, respectively. The dependency of the heat transfer coefficient on fluidizing velocity is qualitatively like that of small particles. An error deviation of around 8.8% was found when comparing experimental heat transfer coefficient values to those predicted from empirical correlations in the published literature.

Continuous Removal of Dyes from Wastewater Using Banana-Peel Bioadsorbent: A Low-Cost Alternative for Wastewater Treatment

Methylene blue is a widely used dye that can have severe negative impacts on the environment and human health. Adsorption is an effective method for removing it from wastewater, but the high cost of traditional adsorbents has motivated the research into low-cost alternatives derived from waste biomass. Designing a dye-removal process requires the knowledge of breakthrough curves. This paper assesses the use of banana peel as an adsorbent in a continuous process for the removal of methylene blue. The adsorption efficiency of lab-scale continuous systems using a stock solution of 0.5 g L−1 methylene blue was analyzed. The best performance was found at pH 6, with a particle size of 0.08–0.3 mm and a fixed bed height of 7.5 cm. The total adsorption capacity was 22.11 mg/g based on experimental data and 25.40 mg/g based on mathematical modeling (Thomas model). The saturation time was 53 h. According to the results, the process conditions and adsorbent characteristics have a critical role in the design of continuous adsorption systems. However, further research is needed to generalize conclusions about the process and include additional experimental data under different operating conditions.

Assessment of experimental methods for measurements of the horizontal flow of fluidized solids under bubbling conditions

Dual fluidized bed systems are indispensable for future energy systems that require solids cycling between different atmospheres. However, controlling the residence time of solids in the reactor, which is crucial for controlling the heat and mass transfer of the fuel, is a significant challenge. This study investigates four experimental techniques to quantify the horizontal flow of solids fluidized under bubbling conditions: integral mass accumulation; differential mass accumulation; thermal tracing; and magnetic solids tracing. Integral mass accumulation entails collecting bed material using a defluidized box within a given time period. Differential mass accumulation measures the material accumulation rate in a section of the bed that is monitored using pressure measurements. Thermal tracing calculates the solids flow rate by solving the heat balance to match the temperature field captured by a thermographic camera. Magnetic solids tracing involves injecting a batch of magnetic tracer solids into the reactor and then measuring the residence time distribution using impedance coils.The experiments were conducted under down-scaled conditions that resemble large-scale operations with a length scaling factor of 0.12. For this study, three operational parameters were varied: the fixed bed height; the volumetric flow rate of the conveying air; and the fluidization velocity in the bed. The horizontal solids circulation rates achieved ranged from 1.7×10−4 to 10 kg/m·s, corresponding to 1.2×10−3 to 70 kg/m·s on a hot up-scaled basis, which is a relevant range to indirect biomass gasification in an industrial setting.The three selected operational parameters led to increases in the horizontal solids flow. While all four methods replicated the trends, quantitative variations in the measured circulation rates occurred due to the inherent characteristics of the methods. High circulation rates resulted in a continuous decrease in the solids inventory, leading to an underestimation of the circulation rate when using the integral mass accumulation method. The accuracy of the differential mass accumulation method relied on transient pressure measurements, which were less-effective at low solids flow rates. Conversely, the accumulation time required for pressure measurements was reduced at high circulation rates, resulting in uncertainties in the analysis. The accuracy of the thermal tracing method decreased drastically with higher solids circulation, resulting in an overestimation of the circulation rate. Moreover, low circulation rates adversely affected the accuracy of the magnetic solids tracing by producing barely discernible tracer concentration gradients.

Experimental investigation of the lateral mixing of large and light particles immersed in a fluidized bed

Fluidized bed reactors for solid fuel conversion are characterized by the presence of a small fraction of fuel particles that are significantly larger (usually 1–2 orders of magnitude larger) and lighter (2–20-fold less dense) compared to the bulk solids. This difference in physical properties strongly influences the mixing of the fuel particles and therefore affects the mass, momentum and heat transfers between the fuel particles and the surrounding bed. This work uses Magnetic Particle Tracking (MPT) to acquire highly resolved trajectories for single tracer particles immersed in a bubbling fluidized bed operated under ambient conditions and with a cross-sectional area of 0.45 m2. This bed size is sufficiently large to abrogate the influence of the reactor walls, allowing data post-processing to study the free movement of the tracer particle, which has not been available to date. This required the enhancement of the MPT system from that in previous works: 12 sensors and a communication protocol in series are here applied, which showed good performance in both spatial accuracy (1 mm) and time resolution (100 Hz). The bed material used in the experiments was glass beads (mean particle size of 106 µm, particle density of 2,486 kg/m3). Two different tracer particles, with diameters of 18 mm but with different densities (572 kg/m3 and 1,015 kg/m3) were used to mimic the sizes and densities of the solid fuel particles. Fluidization velocity was varied within 0.2–0.7 m/s and two fixed bed heights (50 mm and 130 mm) were tested. Based on the trajectories, dispersion coefficients were calculated for quantitative evaluation of the solids mixing. The results reveal that increased bed height yields higher dispersion coefficients with a higher sensitivity for fluidization velocity. The properties of the tracer particles appear, within the tested range, to exert little impact on its lateral dispersion. From the velocity maps generated, a swirling pattern was observed in the vicinity of the walls, while zones of preferential ascendent or descendant movement were observed in the cross-section centre, although clearly defined mixing cells were not exhibited.

Partitioning of a wide bubbling fluidized bed with vertical internals to improve local mixing and bed material circulation

Industrial scale fluidized bed reactors are characterized by limited mixing rates, either local or global, especially when using low-pressure drop gas distributors to reduce operational costs. In this work, partitioning of wide beds using vertical internals is proposed as an effective technique to improve local mixing in large reactors, i.e., mixing in specific zones of the bed. The effect of the vertical internals height on local solids mixing within partitions was experimentally evaluated in a pseudo-2D bed by analyzing the velocity and flow structure of the solids and the circulation time within individual partitions. In the presence of internals, global mixing, i.e., mixing between neighboring partitions and across the entire reactor, may be reduced as vertical internals compartmentalize the bed. Thus, the effect of the internals height on global mixing was also quantified while using bed materials with the same properties, but differing in color, in the different partitions, and analyzing the time evolution of the concentration of solids. Furthermore, the effect of internals on bubbles was also evaluated for different internal heights. It was found that internals with a height between the gulf-stream height and the fixed bed height promote the appearance of vortex pair structures in each partition of the wide bed. These structures substantially improve local mixing within each partition, while global mixing between partitions is practically unaffected by the presence of these short internals. • Pseudo-2D bed was used to characterize the effect of vertical partitions on mixing. • Solids with different colors were used to evaluate local and global mixing. • A model is developed to determine the exchange efficiency between partitions. • Vortex pair structures appear with internals above the gulf-stream height. • Vortex structures improve local mixing, global mixing remaining nearly unaffected.

Compendium data and preliminary results based on alum sludge and gravel continuous fixed-packed-bed column substrate as sustainable practice for constructed wetland development in northern Egypt

The present investigation represents the valuable reclaims of the aluminum-based waterworks sludge that is so called “alum sludge” to close the loop concerning the sludge waste production and the sustainable ecosystem. In this study the adsorption behaviors of aluminium based sludge, namely alum sludge (AS) and gravel as cost-efficient adsorbents regarding dye elimination from aqueous synthetic stream were analyzed in fixed bed column. The influence of variable boundaries such as column pack depth and influent concentration on the effluent concentrations via breakthrough curves were examined. It is estimated that the removal uptake and sorption capabilities elevated as the initial influent loading of the dye dismissed for the fixed bed height of the both adsorbents, namely, gravel and AS. Thereafter, a preliminarily results were checked to investigate the feasibility of the adsorption column in Reactive Blue 4 (RB4) adsorption. The maximum adsorption capacities were observed around 4 mg L-1 for sample with pH 7.5 that is signified as the natural pH of the synthetic stream. However, increasing the initial dye loading increasing the adsorption capacity which reached to 5.5 mg L-1 for the dye loading 27.8 mg L-$$$1 of Reactive Blue 4 (RB4). Thus, the first results will be a valued scheme in the development of adsorption systems to build up a constructed wetland facility.

An integrated ionic liquid hybrid polymeric fixed-bed reactor with a porous sponge-like structure for biomass hydrolysis

Biomass hydrolysis into fermentable reducing sugars is essential for the bioethanol production. Novel integrated ionic liquid (IL) hybrid polymeric fixed-bed reactor with porous sponge-like structure was constructed for inulin hydrolysis. The acidic IL, [(CH2)3SO3HVIm]HSO4 was covalently grafted on polysulfone (PSF). The PSF-ILs integrated porous fixed beds were elaborately prepared by famous non-solvent induced phase separation approach. Effects of coagulation bath composition and temperature, fixed bed height, permeation flux, feed temperature and concentration on inulin hydrolysis were explored intensively. The porous sponge-like structure and chemical binding of ILs endowed the fixed beds with excellent catalytic performance, stability, and reusability. Under optimized conditions, once the inulin aqueous solution permeated through the fixed beds, the yield of total reducing sugar (TRS) reached up to 98.82%. Compared with the catalytic membrane, the hydrolysis reaction time was drastically shortened by 92.5%. These findings provided a new strategy on developing high-performance fixed-bed reactors for biomass conversion.

Removal of chromium and Iron using mixed adsorbent for synthetic and industrial samples in a continuous column reactor

he results of the experiments showed that bed weight, flow rate, and initial metal ion concentration all play a role in the removal of Cr (III) and Fe (II). The optimized break through curve was obtained at 36cm bed height and 10ml/min for chromium where 97.5 to 100% removal was observed at a saturation time of 500-600 min. With the increase in bed height from 12cm to 36cm, both the breakthrough and saturation times for Cr (III) increased. The break through time at 12cm, 24cm, 36cm and 10ml/min for Cr (III) were 70 min, 105 min, and 35 min respectively. The saturation time for Cr (III) at 12cm, 24cm, 36cm and 10ml/min were 460 min, 490 min, and 500 min respectively. Similarly, the break through time for Fe (II) at 12cm, 24cm, 36cm and 10ml/min were 70 min, 80 min, and 100 min respectively. At 12cm, 24cm, 36cm, and 10ml/min, the saturation time for Fe (III) was 340 minutes, 360 minutes, and 430 minutes, respectively. Overall in the column performance comparison between synthetic solution and industrial effluents for chromium, synthetic solution performance was more superior at fixed volumetric flow rates of 10 ml/min and bed heights ranging from 12 cm to 36 cm But the reverse trend was observed in case of fixed bed heights of 36 cm (150 g) and variation of volumetric flow rates from 10ml/min to 30ml/min which indicates that industrial effluent performance was superior when compared to synthetic solution for heavy metal removal.

The control on adsorption kinetics and selectivity of formaldehyde in relation to different surface-modification approaches for microporous carbon bed systems

It is perceived that surface modification of microporous carbon is an efficient option to remove light-weight volatile organic compounds (VOCs) like formaldehyde (FA). To adjust textural characteristics with surface functionalities of amine/sulfur and amino-silane, the commercial activated carbon (AC) was treated with dicyandiamide/thiourea (AC-M) and N-[3-(trimethoxysilyl)propyl]ethylenedia (AC-S), respectively, by thermal/microwave-assisted solvothermal methods. The adsorption performance of honeycomb air filters packed with different bed heights of AC-M/-S adsorbents (e.g., 1.38 ± 0.05, 6.36 ± 0.06, 7.99 ± 0.04, and 10.93 ± 0.04 mm) was evaluated (relative to commercial AC-based filters) towards the adsorption removal of FA (10 Pa) in both single and binary mixtures with benzene (at 10 Pa). . Based on the partition coefficient and kinetic metrics, the AC-M/-S based filters showed higher efficacy for FA capture than commercial AC filter with increasing bed height (e.g., ≥ 7.99 ± 0.04 mm) to reflect the increased number of Lewis acid/base active sites on the bed surface. At the highest bed height (10.93±0.04 mm), AC-S was far superior with significantly enhanced selectivity of FA (by 20 times) over benzene with the accelerated mass transfer and acid-base surface interactions at the gas-solid interface. In contrast, AC-M outperformed commercial ACs for benzene adsorption from the binary gas mixture (breakthrough time (τ-value) of 683 min) with the aid of the improved surface porosity (71.8%) through the modification process. The kinematic data also confirmed that the adsorption affinity of modified AC-M/-S adsorbents was unaffected by the feed gas composition (single or binary phase) at the initial BT region. It thus supports the key role of surface modification technique on the enhanced adsorptivity of aldehyde and/or aromatic VOCs. This study is expected to help expand our basic knowledge on the interplay between surface/textural characteristics of modified AC and fixed-bed height to control the adsorptivity of air filter for efficient trapping of FA in either single or mixed phases with non-polar VOCs (like benzene).

Numerical Studies on Particle Dynamics in a Spouted Bed

A coupled computational fluid dynamics (CFD)-discrete element method (DEM) technique has been adopted to examine the dynamic behavior of particles in a rectangular spouted bed. Eulerian method has been used to solve the Navier–Stokes equation for the gas phase (for the CFD) and Lagrangian method (for the DEM) for the particle phase, where the k–ϵ two-equation turbulence model has been used to capture the effect of gas-phase turbulence. In the present work, we sought to predict the minimum spouting velocity (Ums) numerically for a fixed bed height and particular particle properties. The effects of the inelastic collision and the friction on translational and rotational dynamics of the particles in spout, annulus, and fountain zones have been brought out with the intensive parametric study. The results reported here would be a way forward for a better understanding of the spouted bed processing where translational and rotational dynamics of particles play a key role.

Wastewater treatment by adsorption process on mineral actived carbon: modeling and prediction using an intelligent artificial approach

Currently there are several wastewater treatments processes, and several adsorbent materials consist of separating and purifying the various industrial effluents. In this work an artificial neural network (ANN) was developed to describe the dynamic adsorption of sodium decanesulfonate using actived carbon obtained by the calcination of mineral biomass under different conditions. Three inputs (time, mass of adsorbent and fixed bed height) were used in the input layer, three neurons in the hidden layer and one in the output layer for the reduced concentration. The Levenberg Marquardt back-propagation algorithm was applied. The tangent sigmoid and linear transfer functions are used for the hidden layer and the output layer respectively. The results showed a correlation coefficient R2 = 0.9965 with root mean squared error RMSE = 0.0276. An interpolation and an extrapolation stage are made to test the accuracy of the network. The results showed a high correlation coefficient R2 = 0.9969 and 0.984 respectively for the interpolation and the extrapolation. These results show the robustness and the high capacity of ANN to describe the dynamic adsorption of sodium decanesulfonate onto actived carbon.

3D numerical simulation of a directly irradiated bubbling fluidized bed with SiC particles

Abstract This paper presents the numerical results obtained in a directly irradiated fluidized bed. The numerical model was implemented using CPFD-Barracuda software coupled with a P-1 radiation model. The bed consists of a cylindrical geometry containing SiC particles, with a diameter of 7.62 cm and a fixed bed height of 8 cm. The irradiation on the top of the bed was implemented by including a high temperature surface that directly irradiated on the top of the bed, with a uniform radiation flux of 3 × 1 0 4 kW ∕ m 2 . The work studies the influence of the airflow rate and the thermal behavior of the irradiated bed. The results show that increases in the airflow rate (up to 2.5 times the minimum fluidization conditions) notably enhance the mixing rate and the agitation levels on the top of the bed, reducing the appearance of hot spots on the top surface, with the bed exhibiting a more uniform temperature in its upper half. At higher airflow rates, the maximum temperature of the directly irradiated particles is reduced from 454 K to 384 K when the airflow rate is increased from 1.5 to 2.5 times the minimum fluidization airflow rate. In contrast, the mean temperature of the whole bed of particles rises (from 315.9 K to 327.5 K), increasing the storage efficiency.

Monitoring of the fluidized bed particle drying process by temperature and pressure drop measurements

This work aimed to monitor the temperature and the pressure drop behaviors in bed during the drying of Persian clover and arrowleaf clover seeds in a fluidized bed. The inlet air temperatures were of 40 °C and 50 °C, with a fixed bed height (Hl:Dl ratio of 1:1) and fluidization velocity of 2.7 times the minimum. For the temperature and the pressure drop profiles in bed and the standard deviation of pressure drop, all changed significantly during the process in function to solids moisture content, mainly on the transition of the constant rate period to the falling rate period, due to change of the mass transfer mechanisms. In addition, an analysis of pressure measurements in the frequency domain was performed, using the Fast Fourier Transform, and power spectra of distinct characteristics for the two drying periods was obtained, showing that this technique can be a potential alternative for operation drying monitoring. Highlights Temperature and pressure drop measurements showed great potential for monitoring the particles; Pressure and temperature measurements between of constant and falling rates periods had changed significantly; Standard deviation measures behaved in a similar way to pressure drop; Power spectra became wider and showed a decrease in amplitude during the operation.

CO2 Removal Using Adsorption Onboard A Floating Production Storage and Offloading (FPSO) Vessel

Offshore operations gas purification has always been limited to the marketable associated value of the gas where purification would either be onsite or sent to surface facilities for treatment. CO2 and H2S removal and gas sweetening in remote offshore locations is for the most part non-existent and CO2 is either being released into the atmosphere, within the acceptable operation limit of the platform, or being captured using conventional techniques with physical solvents such as in the selexol, rectisol, or sulfinol processes. Approximately 429.61 kg of CO2 exists in a 42-gallon barrel of distillate fuel oil and a CO2 coefficient of 0.0549 kg exists in 1 cubic foot of gas thereby emphasizing the need for an engineering solution on floating production storage and offloading (FPSO) units [1]. With strict regulation on greenhouse gases, it is increasingly paramount to utilize engineering measures to provide a contingency plan in mitigating carbon footprint with emerging novel technologies. The purpose of this study is to retrofit an existing FPSO with a CO2 capture plant; the efficiency of the capture plant, its capture capacity, and energy requirement based on experimental data will be thoroughly investigated during the scale up procedure. The research proceedings will require the use of a plethora of simulation suites which include Autodesk Fusion 360 for plant design. Further simulation will be carried out with numerical suites using Mathcad Prime 3.0 to study the scale up procedure from experimental to industrial sized adsorption unit complete with dimensions, energy requirement, capture capacity, and thermal values. The FPSO in figure 1 above presented by (Araujo et al., 2016) indicates the availability of a capture plant as part of the process train on an FPSO. Efficiency loss contribution to the system may be deduced but also it is relevant to note the custom nature of the FPSO design being independent in its operation mode compared to other profiles. The availability of the stage compressors, dehydration units, and steam generation plant as part of the FPSO operation aid in minimising the need for additional equipment for the adsorption plant, however investigation has to be made on the redirecting of processes to serve the additional components highlighted above. Primary results have shown a low tendency for dual adsorption from the initial kinetic stoichiometric balance which could also be due to the force field parameters and charges affecting the active sites. For the current concept the fixed bed experimental model from the Research and Innovation Centre on CO2 and H2 is scaled up numerically to a fixed bed height of 6.56 feet, and filled with precipitated silica impregnated with PEI solution pressurized with CO2 inflow rated at 13 lb/hr at a fixed 1.2 Bar 60°C. The operational nature of the FPSO will be modified to account for the changes requested in gas sweetening and capture programs or enhanced oil recovery. Results from the simulation will also assist in providing a tangible and relatable understanding to the complexity of solid sorption technology integration within existing processing plants. The findings of this study will help comprehend the viability of an integrated adsorption plant within an existing process train. The efficiency of the plant operation for an oil production offshore facility with associated gas or for a standalone gas field will be addressed using a feasibility study conducted for the purpose of sustainable offshore operations.

Performance Evaluation of Fixed Bed Column Packed with Ionic Liquid Impregnated Silica for Separation of Gadolinium and Neodymium from Aqueous Solutions

Application of fixed bed column for separation of gadolinium and neodymium ions from their aqueous solutions using cyphos IL-104 impregnated silica was investigated. The performance of separation of the two lanthanide elements was evaluated by determining the column capacity, the total quantity sorbed of metal ions, and the removal percentage. These indicative column performance parameters were evaluated in altered conditions including fixed bed height of 2.0 and 3.0 cm, flow rate of 1.0 and 2.0 mL/min, and solution feed concentration of 50 and 100 ppm. Breakthrough modeling of the sorption process across the column was performed by employing Thomas and Adams–Bohart models. It was found that it took less time to reach the breakthrough when the flow rate and initial concentration increased, while the height of the bed decreased. Also, the column capacity increased by increasing the bed depth, decreasing the flow rate, and increasing the initial metal ion concentrations. 0.1 M nitric acid was found to be the best media for the separation of Nd3+ and Gd3+ ions.

Hydrodynamic Properties of High Activated y-Al2O3 in a Fixed Bed Reactor

The high activated γ-Al2O3 hydrodynamic properties in the fixed bed are studied in this paper. The factors of gas velocity and the heights of the bed on the axial bed pressure, bed pressure drop and bed voidage are studied. The results indicated that under the same height of fixed bed, the axial pressure decreased along the bed at the same gas velocity. While the pressure drop increased with the gas velocity and the bed height increased. The pressure drop has a good agreement to the Ergun equation. According to the Ergun equation, the bed voidage is regressed at different height of fixed bed. The results revealed that the bed voidage of high-activated γ-Al2O3 is almost the same in the fixed bed heights of 400 mm, 300mm and 200mm, which is 0.31, 0.32, and 0.32 respectively.

MOF-based polymeric nanocomposite beads as an efficient adsorbent for wastewater treatment in batch and continuous systems: Modelling and experiment

Herein, a novel polymeric nanocomposite based on zeolitic imidazolate frameworks (ZIFs) was synthesized through a facile one step phase inversion (PI) technique. The prepared PES/ZIF-8/ZIF-67 was employed to remove Malachite green (MG) dye from colored wastewater in both batch and continuous flow systems. The influence of different parameters such as adsorbent dosage, initial MG concentration and solution pH were investigated and the results indicated that the pure PES beads had negligible adsorption, while compositing of this polymer with ZIFs particles removed 99.2% of MG molecules with a significant adsorption capacity (613.2 mg/g). Aromatic–aromatic interactions (π-π stacking) between the rings of imidazole ligand and MG dye was dominant adsorption mechanism. Kinetics and equilibrium isotherms studies revealed that batch adsorption experiment followed pseudo-second order and Langmuir models, respectively. In addition, the continuous separation process was evaluated and the breakthrough curves (BTCs) proposed that the longest breakthrough time could be attained within 12 mg/L of inlet MG concentration, 6 cm of fixed bed height and 1 mL/min of flow rate. Several well-known models including Thomas, Bed Depth Service Time (BDST), Adams-Bohart and Yoon-Nelson models were employed to correlate the experimental data obtained from the fixed bed adsorption setup. Moreover, continuous flow adsorption was simulated using Aspen Adsorption™ software which can solve the governing differential equations and provide useful information for designing and scaling up the adsorption process to the industrial levels. Consequently, the PES/ZIF-8/ZIF-67 beads with a high adsorption performance have a good application potential for eliminating organic contaminates from wastewater.

Modified Biopolymer Adsorbents for Column Treatment of Sulfate Species in Saline Aquifers

In the present study, variable forms of pelletized chitosan adsorbents were prepared and their sulfate uptake properties in aqueous solution was studied in a fixed-bed column system. Unmodified chitosan pellets (CP), cross-linked chitosan pellets with glutaraldehyde (CL–CP), and calcium-doped forms of these pellets (Ca–CP, Ca–CL–CP) were prepared, where the removal efficiencies and breakthrough curves were studied. Dynamic adsorption experiments were conducted at pH 4.5 and 6.5 with a specific flow rate of 3 mL/min, fixed-bed height of 200 mm, and an initial sulfate concentration of 1000 mg/L. Breakthrough parameters demonstrated that Ca–CP had the best sulfate removal among the adsorbents, where the following adsorption parameters were obtained: breakthrough time (75 min), exhaust time (300 min), maximum sulfate adsorption capacity (qmax; 46.6 mg/g), and sulfate removal (57%) at pH 4.5. Two well-known kinetic adsorption models, Thomas and Yoon-Nelson, were fitted to the experimental kinetic data to characterize the breakthrough curves. The fixed-bed column experimental results were well-fitted by both models and the maximum adsorption capacity (46.9 mg/g) obtained was for the Ca–CP adsorbent. A regeneration study over four adsorption-desorption cycles suggested that Ca–CP is a promising adsorbent for sulfate removal in a fixed-bed column system.