Fixed-bed Adsorption Research Articles

Fixed-bed CO2 adsorption onto activated char from the pyrolysis of a non-recyclable plastic mixture from real urban residues

The potential use of activated char obtained from the pyrolysis of a mixture of non-recyclable plastics for the adsorption of CO2 in fixed-bed columns has been explored. The rejected fraction of plastics collected in a municipal solid treatment plant was pyrolyzed and the resulting char residue was activated to develop a porous carbonaceous material. The dynamic behavior of CO2 adsorption was assessed by the breakthrough curves obtained in continuous column tests. Among all the available models, the curves were successfully fitted to the dose-response model. The effect of adsorption temperature (15–45 ºC), the inlet CO2 concentration (10–40 %, vol.), and the adsorbent length of the bed (loadings, 1–2 g) on the efficiency of the process was evaluated by the surface response methodology applying an adaptative neural fuzzy inference system (ANFIS). A temperature rise exerted a negative effect on the adsorption capacity due to the physisorption properties of the process, the fed CO2 concentration displayed a positive effect and the fixed-bed length did not play a remarkable influence.

Performance of slurry contact adsorber operating under high gravity for removal of fluoride

Fine adsorbent particles though associated with large surface area and high adsorption rate are not employed in fixed bed adsorber for wastewater treatment due to high-pressure drop. In this investigation, slurry contact adsorption wherein fine adsorbent particles can be utilized was studied for the removal of fluoride using commercial activated charcoal as adsorbent (size<100 µm). The mass transfer operation was performed in two rotating contactors (rotating packed bed and rotating spiral) operating under centrifugal acceleration up to fifty times the terrestrial gravity, and conventional contactors (continuous stirred tank and fixed bed). The results indicated that the removal efficiency with slurry contact adsorption is higher in rotating spiral contactors compared to rotating packed bed or traditional contactors. Maximum utilization (equilibrium loading) of adsorbent particles at contactor exit is approached at high rotational speed and adsorbent dosage, and low feed flow rate and feed concentration. The magnitude of the volumetric mass transfer coefficient in a rotating spiral contactor obtained from mathematical modeling varied between 1.5 × 10−2 1/s to 8.0 × 10−2 1/s.

Integrating chemical coagulation with fixed-bed column adsorption using rice husk-derived biochar for shipboard bilgewater treatment: Scale-up design and cost estimation

Discharging shipboard bilgewater (SBW) into seas and oceans without proper treatment could poison marine organisms and negatively impact transportation-related activities. This study focuses on the treatment of synthetic SBW using a simple and cost-efficient physico-chemical process. This treatment system included coagulation-flocculation (CF) using alum coagulant and fixed-bed column adsorption using rice husk-derived biochar (RHB). The optimization and effect of CF process parameters, viz., pH, fast stirring speed, and alum dosage, on surfactant and COD removal efficiencies were studied using a central composite design-response surface methodology (CCD-RSM). At optimum conditions (pH of 6.4, rapid mixing speed of 160 rpm, and coagulant dosage of 140 mg/L), the surfactants and COD removal efficiencies were 46.31±1.48% and 84.67±2.61%, respectively. The adsorption column optimum conditions were flow rate= 5 mL/min and bed depth= 16 cm, giving a surfactant removal efficiency of 96.6%. The primary adsorption mechanism was physisorption, including electrostatic attraction, hydrogen bonding, pore-filling, and hydrophobic interaction, as revealed by SEM, EDX, and FTIR characterizations. The adsorption data fitted well with Thomas model predictions, giving the best kinetic constant (KTh)= 0.305 mL/min/mg and equilibrium surfactant uptake (qo)= 11.05 mg/g (R2= 0.996). The Thomas model's coefficients were successfully used to predict the breakthrough curves and determine the column dimensions for pilot-scale (3 L/h) and large-scale (300 L/h) fixed-bed adsorption units. The estimated cost for the on-board treatment of SBW by the proposed system was 2.51 US$/m3. Future studies are required to implement the proposed combined coagulation/flocculation/adsorption system to treat real SBW from medium-sized ships.

Boron continuous recovery from brines by the multicolumn simulated moving bed process with boron chelating resin

The objective of this work is to develop an advanced adsorption process to continuously recover and remove boron from brines. Firstly, the adsorption and desorption performances of boron on the commercially available N-methylglucamine resin (D403 resin) are evaluated, then, the cyclic adsorption and desorption process is investigated experimentally in the fixed bed adsorber for boron recovery from brine. It is confirmed that the cyclic process involves five steps, such as boron recovery from brine, water washing 1 to remove the retained brine, boron desorption to obtain boron-rich solution, water washing 2 to recover the retained HCl solution, and resin regeneration for the reuse. Furthermore, the seven-column simulated moving bed (SMB) process with four zones is designed and investigated experimentally. Experimental results demonstrate that boron can be recovered continuously from brine in adsorption zone, and boron-rich solution is obtained continuously in desorption zone. When the inlet brine contains a low boron content (for example 296.5 mg/L), most boron in brine can be recovered by the seven-column SMB unit with 96.8 % boron adsorption efficiency, and the discharged brine contains 8.77 mg/L boron, approximately meeting the environmental protection requirement for the limitation of boron emission. Therefore, the simultaneous recovery and removal of boron from brine can be achieved by the proposed multicolumn SMB process.

Performance assessment of the MOF adsorbent MIL-101 for removal of gaseous benzene and toluene: kinetic column modeling and simulation studies of fixed-bed adsorption.

The adsorbent MIL-101, a metal-organic framework material, was synthesized, characterized, and tested for removal of relatively low concentrations of benzene and toluene adsorbates (200 ppm) from a gas phase in a continuous flow system. Breakthrough studies were modeled based on Thomas, Yoon-Nelson, Yan, Clark, Bohart-Adams, bed-depth service time, modified dose response, Wolborska, and Gompertz in the continuous fixed-bed operation. Through statistical analysis, it was determined which type of regression is most suitable for the studied models, linear or nonlinear. By comparing the values of error functions, it was possible to infer that the Thomas model is the best match for the experimental breakthrough curves for benzene (with maximum solid-phase concentration qT=126,750 mg/g) and the Gompertz model for toluene (parameter β=0.01 min-1). Overall, when compared to the model parameters of the linear regression, those obtained through nonlinear regression show a stronger correlation with the results found experimentally. Thus, this type of regression is more suitable for the adsorption model analysis. The liquid film and intraparticle diffusion analysis was described, and it was suggested that both types of diffusion contribute to the adsorption mechanism of benzene and toluene on MIL-101. As for the isotherms, the adsorption process was better fitted by the Freundlich isotherm. The reusability of MIL-101 after six cycles was 76.5% for benzene and 62.4% for toluene, indicating that MIL-101 was a better adsorbent for the removal of benzene in comparison with toluene.

Renewable Adsorbents for Selective Phosphorus Removal: Co(OH)2-Derived ZIF-67 on Anion Exchange Resin.

Metal organic framework (MOF)-based adsorbents are appealing for removing low-concentration phosphates with interfering ions in wastewater purification, a new strategy developed to maintain the good activity of metal sites. Here, ZIF-67 was immobilized onto the porous surface of anion exchange resin (D-201) with a high loading amount of 22.0 wt % by a modifiable Co(OH)2 template. We observed that the removal rate of low-concentration phosphate (2 mg P/L) by ZIF-67/D-201 nanocomposites was 98.6%, and more than 90% phosphate adsorption capacity was still maintained, with 5 times molar concentration of interfering ions in the solution. Moreover, after six times of regeneration by solvothermal reaction in the ligand solution, the structure of ZIF-67 was better preserved in D-201 with more than 90% phosphate removal rate. ZIF-67/D-201 could be employed effectively in fixed-bed adsorption runs. By the analysis of experiment and characterization, we found that during the adsorption-regeneration process of ZIF-67/D-201 for phosphate, reversible structural transformation of ZIF-67 and Co3(PO4)2 occurred in D-201. In general, the study reported a new method to develop MOF adsorbents for wastewater treatment.

Sodium-alginate-laden MXene and MOF systems and their composite hydrogel beads for batch and fixed-bed adsorption of naproxen with electrochemical regeneration

Sodium alginate (SA)-laden two-dimensional (2D) Ti3C2Tx MXene (MX) and MIL-101(Fe) (a type of metal–organic framework (MOF)) composites were prepared and used for the removal of naproxen (NPX), following the adsorption and electrochemical regeneration processes. The fixed-bed adsorption column studies were also conducted to study the process of removal of NPX by hydrogels. The number of interactions via which the MX-embedded SA (MX@SA) could adsorb NPX was higher than the number of pathways associated with NPX adsorption on the MIL-101(Fe)-embedded SA (MIL-101(Fe)@SA), and the MX and MIL-101(Fe) composite embedded SA (MX/MIL-101(Fe)@SA). The optimum parameters for the electrochemical regeneration process were determined: charge passed and current density values were 169.3 C g−1 and 10 mA cm−2, respectively, for MX@SA, and the charge passed and current density values were 16.7 C g−1 and 5 mA cm−2, respectively, for both MIL-101(Fe)@SA and MX/MIL-101(Fe)@SA. These parameters enabled excellent regeneration, consistent over multiple adsorption and electrochemical regeneration cycles. The mechanism for the regeneration of the materials was proposed that the regeneration of MX@SA and MIL-101(Fe)@SA involved the indirect electrooxidation process in the presence of OH radicals, and the regeneration of MX/MIL-101(Fe)@SA involved the indirect oxidation process in the presence of active chlorine species.

An engineered biochar for treatment of selenite contaminated water: Mass transfer characteristics in fixed bed adsorption

Biochar composites have been gaining attention in recent years as a promising and cost-effective material for wastewater treatment. In the present study, a novel procedure was developed to create a biochar (BC) composite impregnated with binary zinc (Zn) and iron (Fe) oxides (denoted as ZnFeBC). The procedure was optimized to enhance selenite, Se(IV), adsorption performance of the ZnFeBC composite. The modified biochar composite had excellent pore characteristics with a specific surface area of 854 m2/g. The maximum Se(IV) adsorption capacity of an unary Zn-loaded biochar composite was 520 µg/g, which significantly increased to 4,100 µg/g after the iron oxide impregnation. Isotherm experiments suggested that the adsorption process was likely through homogeneous monolayer adsorption. The ZnFeBC composite exhibited excellent performance over a broad range of pH values, with the highest Se(IV) adsorption capacities observed at lower pH values (maximums at pH 3). X-ray absorption near edge structure spectroscopy (XANES) indicated that the redox reaction of Se oxyanions did not occur during the adsorption process. ZnFeBC was successfully used to remove Se(IV) from a mining lake water matrix in a fixed-bed adsorption system. Additionally, a mass transfer model optimizing effective diffusion and external mass transfer coefficients was developed to comprehensively assess the adsorption system. Overall, ZnFeBC exhibited great potential as an adsorbent for treating Se(IV) contaminated waters and the developed mass transfer model is useful for scaling up fixed-bed adsorption systems.

Performance and mechanism of La-Fe metal-organic framework as a highly efficient adsorbent for fluoride removal from mine water

Water fluoride pollution has caused non-negligible harm to the environment and humans, and thus it is crucial to find a suitable treatment technology. In this study, La-Fe@PTA adsorbent was synthesized for the defluoridation of mine water. The results showed that the optimum conditions for defluoridation by La-Fe@PTA were pH close to 7.0, the initial F− concentration of 10 mg/L, the dosage of 0.5 g/L and the adsorption time of 240 min. Compared with SO42‒, Cl‒, NO3‒, Ca2+ and Mg2+, CO32‒ and HCO3‒ presented severer inhibition on fluoride uptake by La-Fe@PTA. The adsorption process fits well with the pseudo-second-order kinetic model and Freundlich model, and the maximum adsorption capacity of Langmuir model was 95 mg/g. Fixed-bed adsorption results indicated that fluoride in practical fluorinated mine water could be effectively removed from 3.6 mg/L to less than 1.5 mg/L within 130 bed volume (BV) by using 1.5 g La-Fe@PTA. Furthermore, the adsorbent still had good adsorption capacity after regeneration, which confirms the great application potential of La-Fe@PTA as a fluoride ion adsorbent. The mechanism analysis showed that La-Fe@PTA adsorption of fluorine ions is a physicochemical reaction driven by electrostatic attraction and ion exchange.

Robust mechanical-performance core-shell nanostructured HNTs/PAN-supported Cu(I)/UIO-66 composite nanofibers towards selective adsorption removal of benzothiophene

In this work, a novel core-shell nanostructured coaxial nanofiber membranes (CFMs) were successfully produced by the coaxial electrospinning. The structure and composition of CFMs were probed by a series of characterizations. The results demonstrated that the CFMs were comprised of the versatile core-shell structure nanofibers, therein Cu(I)/UIO-66 scattered in the shell layer and HNTs dispersed in the core layer. As applied in the selective adsorption desulfurization, the Cu(I)/UIO-66 embedded on the surface of the nanofiber undertook the adsorption active sites, while HNTs in core layer served as enhancing the mechanical performance of PAN nanofibers. The CFMs had the superior adsorption performance in the batch adsorption (maximum:40.14 mg·g−1) and fixed-bed adsorption (maximum: 47.43 mg·g−1) capacities for benzothiophene (BT) from fuel oil, respectively. Furthermore, due to having the robust mechanical performance, the CFMs exhibited the preferable recycling adsorption and mechanical stability. The adsorption mechanism of BT molecules on CFMs was explored by the kinetics, isotherms and thermodynamic models, indicating the existence of the synergistic effect of physical adsorption and chemical adsorption.

Preparation of P-doped biochar and its high-efficient removal of sulfamethoxazole from water: Adsorption mechanism, fixed-bed column and DFT study

Heteroatom doping technology is of great significance for adsorption. However, the effect of P with relatively lower electronegativity (2.19) doped in the π-electron system and phosphorus-containing functional groups on the adsorption has always been neglected. Herein, P-doped biochar (PBC) was successfully synthesized via the in-situ activation method and applied in a bath experiment and a long-term fixed-bed dynamic adsorption for sulfamethoxazole (SMX) removal. Compared to pristine BC, the pHpzc, ash content and graphitization degree of PBC would be reduced significantly after phosphoric acid (H3PO4) was treated, but it gained a large specific surface area (SSA = 233 m2 g−1), as well as abundant surface functional groups. In the adsorption process, the behavior of SMX adsorbed onto PBC conformed to pseudo-second-order kinetic and Langmuir models in batch experiments. Its excellent adsorption capacity (148.62 mg g−1) benefited from a large number of functional groups. DFT calculation indicates that the C3-P-O configuration mainly promoted the adsorption of SMX. It is speculated that the hydrogen-bond interaction between SMX and C3-P-O was the main adsorption mechanism, and electrostatic and π-π EDA interaction also contributed. Various parameters during the dynamic process were thoroughly explored. The saturated adsorption capacity of the column would be promoted when influent SMX concentration and bed depth increased, but negatively correlated with solution pH and influent rate. Moreover, PBC fixed-bed column for SMX removal was well fitting Thomas, Yoon-Nelson and BDST models, which provided a predictable strategy for practical application.

Removal of Hexamethyldisiloxane by NaOH–Activated Porous Carbons Produced from Coconut Shells

The utilisation of activated porous carbon (APC) for the removal of volatile methyl siloxane (VMS) has attracted significant research attention. However, the development of materials with high adsorption capacity remains a challenge. In this study, we successfully developed a high-specific-surface-area (2551 m2 g−1) APC material with a large porous texture (1.30 cm3 g−1) using coconut shell waste and NaOH as the activating agent. The performance of the APC material in the removal of hexamethyldisiloxane (L2) was evaluated using a fixed-bed dynamic adsorption setup. Notably, at 0 °C, the APC demonstrated a remarkable L2 removal ability, achieving a breakthrough adsorption capacity of 898.6 mg g−1. By increasing the inlet concentration of L2 and decreasing the temperature appropriately, the L2 adsorption capacity could be further improved. One advantage of APCs is their simple recycling process, which allows for sustained adsorption performance even after five consecutive cycles of adsorption and desorption. Therefore, the prepared APC material holds great promise as an efficient adsorbent for the removal of VMS.

Constructing porous ZnFC-PA/PSF composite spheres for highly efficient Cs+ removal

Radioisotope leaking from nuclear waste has become an intractable problem due to its gamma radiation and strong water solubility. In this work, a novel porous ZnFC-PA/PSF composite sphere was fabricated by immobilization of ferrocyanides modified zinc phytate into polysulfone (PSF) substrate for the treatment of Cs-contaminated water. The maximum adsorption capacity of ZnFC-PA/PSF was 305.38 mg/g, and the removal efficiency of Cs+ was reached 94.27% within 2 hr. The ZnFC-PA/PSF presented favorable stability with negligible dissolution loss of Zn2+ and Fe2+ (< 2%). The ZnFC-PA/PSF achieved high-selectivity towards Cs+ (Kd = 2.24×104 mL/g) even in actual geothermal water. The adsorption mechanism was inferred to be the ion-exchange between Cs+ and K+. What's more, ZnFC-PA/PSF worked well in the fixed-bed adsorption (E = 91.92%), indicating the application potential for the hazardous Cs+ removal from wastewater.

Mercury removal from aqueous media by aminated polyacrylonitrile beads impregnated with nano-urchin bismuth sulfide particles: Experimental and theoretical analysis under batch and continuous mode

The present study encompasses a thorough analysis of aqueous Hg (II) adsorption using aminated polyacrylonitrile beads incorporated with high-capacity surfactant assisted bismuth sulfide nanoparticles. The porous beads provided effective contact between aqueous Hg and the inorganic nano-adsorbent (PBS2) that was encapsulated in the matrix. The macro-sized beads served as suitable packing material for designing a fixed bed adsorption column for continuous mode analysis without significant pressure build up and offered an easy solid–liquid separation after treatment. A marginal negative zeta potential of the adsorbent beads improved the interaction with Hg2+ facilitating the sorption. The incorporation of amine groups into the polymeric bead surface via amination increased the adsorption capacity further from 83.30 mg/g to 130.00 mg/g (∼56.00%) at 303 K. The associated parameters of batch kinetics (effective pore diffusivity and mass transfer coefficient) were determined using a first principle-based model available in literature. Mercury was chemisorbed via synergistic lone pair interactions of S and N atoms with Hg, leading to formation of coordination bonds (Hg-S and Hg-N). An established mass transfer model was utilized to generate simulated breakthrough curves for the continuous analysis using synthetic feed. Additionally, the adsorption column showed comparable performance using both synthetic and real water samples (synthetically spiked) maintaining high selectivity. The optimized values of axial dispersion coefficient (Ez) and fixed bed mass transfer coefficient (kfb) were estimated and subsequently used for the scale up studies to predict column life. The adsorbent beads were regenerated using 0.05 M EDTA aqueous solution and showed good reusability (>95.00%) after 5 cycles of operation. Overall, this work highlights a reusable Hg adsorbent possessing good selectivity and capacity and simultaneously demonstrating real-field applicability.

A breakthrough adsorption study of modified activated carbon using different environmentally-friendly activating agents

Adsorption using solid adsorbents is a promising technique for capturing carbon dioxide (CO&lt;sub&gt;2&lt;/sub&gt;) to reduce greenhouse gas emission. In the present work, palm shell-based activated carbon was functionalized with eco-friendly activating agents including potassium carbonate, potassium acetate, binary deep eutectic solvent (DES) composed of choline chloride and ethylene glycol, and ternary DES composed of choline chloride, urea and ethylene glycol by impregnation method. Post-combustion CO&lt;sub&gt;2&lt;/sub&gt; adsorption performance of the functionalized adsorbents was evaluated in a fixed-bed adsorption column under varying adsorption temperature (25-55°C) and inlet CO&lt;sub&gt;2&lt;/sub&gt; concentration (15-20%), followed by a cyclic CO&lt;sub&gt;2&lt;/sub&gt; adsorption study to determine the regeneration ability of the adsorbents. The results revealed that activated carbon modified with potassium acetate (ACPA) exhibited remarkably high CO&lt;sub&gt;2&lt;/sub&gt; adsorption capacity of 116.5 mg/g and breakthrough time of 54 min at 25°C and 15% inlet CO&lt;sub&gt;2&lt;/sub&gt; concentration. Furthermore, ACPA demonstrated good regeneration ability even after seven adsorption-desorption cycles. Interestingly, it was found that activated carbon modified with ternary DES (AC-DES 4) exhibited significantly higher adsorption capacity than activated carbon modified with binary DES (AC-DES 2). It is worth mentioning that the present work is the first study that uses ternary DES as activating agent for such purpose.

Fixed bed adsorption of phosphate by lanthanum carbonate modified microfibrous composite

A kind of novel adsorbent, lanthanum carbonate modified microfibrous composite (LC-MC), is synthesized through a facile combined wet lay-up paper making and hydrothermal synthesis method. The fixed bed phosphate adsorption results show that LC-MC performs best when initial phosphate concentration is 5 mg/L, flow rate is 2.7 mL/min and bed height is 2 cm, with the maximum breakthrough time of 82.5 h and maximum adsorption capacity of 38.5 mg/g. High bed height and low flow rate are beneficial to the phosphate adsorption. Acid solution conditions benefit the adsorption process but will cause leakage of the lanthanum species (over 8 mg/L). 50 mg/L co-existing anions have no significant effect on the adsorption process, while concentrations more than 100 mg/L obviously inhibit the adsorption. The adsorbent also shows a good regenerability with less than 15 % decrease in adsorption capacity after 5 cycling runs. The adsorption kinetic process can be described better by the Yoon-Nelson model than Adams-Bohart model and Thomas model. Finally, the mechanism study indicates that the formation of phosphate lanthanum is the main reason for phosphate adsorption on LC-MC. Results show that LC-MC is a promising phosphate adsorbent to be used in fixed bed.

DESIGN OF A FIXED BED ADSORPTION COLUMN AND MODELLING OF OPERATING PARAMETERS FOR THE REMOVAL OF METHYLENE BLUE IN DYNAMIC MODE

This study investigates the potential of using the mixture of titaniferous sand and attapulgite as adsorbents in a fixed bed adsorption process to remove a synthetic dye such as methylene blue in aqueous media. The different adsorbents were characterised by X-ray fluorescence spectroscopy and infrared spectroscopy. The different physico-chemical parameters such as pH, zero charge potential, bulk and absolute density, porosity and specific surface area were determined. The sizing algorithm used resulted in a number of transfer units (NUT) equal to 20.109, a height of transfer unit (HUT) equal to 0.515, a material transfer coefficient (Kya) equal to 3.159 and a height of the column (Z) equal to 1.05m. The influence of different experimental parameters such as initial dye concentration, adsorbent bed height and feed rate on the breakthrough curve was investigated. Various simple mathematical models such as Adams-Bohart and Thomas were applied in order to study the dynamic behaviour of the column and to estimate some kinetic coefficients through the experimental data obtained from the dynamic studies performed on the fixed bed. The results showed that the Thomas and Adams-Bohart models perfectly describe the behaviour of the breakthrough curves with values of coefficients of determination R2 that are higher than 0.90 except for the concentration of the dye equal to 50mg/L which has a coefficient R2 equal to 0.88.

Application of a biochar produced from malt bagasse as a residue of brewery industry in fixed-bed column adsorption of paracetamol

We report the removal of paracetamol from aqueous systems using a fixed-bed packed with biochar obtained from pyrolysis of malt bagasse residue (MBR). MBR biochar was characterized by carbonization yield, pH, Fourier-transform infrared spectroscopy (FTIR), and specific surface area (BET method). High surface area biochar (308.6 m² g-1) was fixed in a bed sorption column and sorption capacity was studied by varying the mass of sorbent and sorbate flow rate. Sorption isotherms (breakthrough curves) in the traditional "S" shape were observed in the assays. The nonlinear models of Thomas, Bohart-Adams and Yan-Viraraghavan were applied to the experimental data, with the model of Yan-Viraraghavan best describing the behavior of the isotherms, with a good mean coefficient of determination (R²) of 0.9883. Breakthrough times were greater at lower flow rates and greater sorbent amounts, and the effect of sorbent mass alone upon adsorption capacity (qexp) was not significant for a given flow rate. Thus, beer processing residue can be a source of raw material for the production of value-added MBR biochar, since it showed good sorption results of paracetamol in the biochar fixed-bed column, reaching sorption capacities at equilibrium up to 27.65 mg g-1 depending on the experimental parameters adopted.

Assessment of dual-adsorbent beds for CO[formula omitted] capture by equilibrium-based process design

We have carried out a model-based assessment of dual-adsorbent beds for post-combustion CO2 capture, whereby we consider systems in which two distinct adsorbent materials are homogeneously mixed to form a fixed bed adsorber. We have employed an equilibrium-based process model (D-BAAM) to simulate and optimize the process performance of a four-step vacuum swing adsorption cycle for CO2 capture with a dual-adsorbent bed. We have used the developed framework to screen the performance of 2,850 binary combinations of adsorbents from a database of 76 promising materials for post-combustion capture, which includes zeolites, activated carbons, metal organic frameworks (MOFs) and zeolitic imidazolate frameworks (ZIFs). Through unconstrained purity/recovery process optimization, we determine that only one pure material in a material pair needs to itself satisfy regulatory constraints on CO2 purity/recovery for post-combustion capture to yield a dual-adsorbent process which satisfies the constraints. For these dual-adsorbent combinations, we have assessed the optimal process performance in the constrained working capacity/energy usage Pareto plane and have identified nine distinct categories of process behavior. Five of these categories have the potential to allow for a reduction in the energy penalty of the separation, as compared to the constituent single-adsorbent processes. We have observed reductions in the energy penalty of the separation of approximately 20%. We contend that such processes may be economically optimal depending on a process specific balance of capital, operating and material costs, and should be investigated in more detail using dynamic process modeling and an associated techno-economic assessment.

Spinning Submerged Filter Adsorber versus Packed Bed Adsorber for the Continuous Removal of Antibiotics from Wastewater with Activated Carbon

The removal of antibiotics from wastewater is receiving considerable attention to fulfill water quality parameters required for reuse. This study compares a spinning submerged filter adsorber with a fixed bed adsorber for continuous antibiotic removal. Adsorbers were evaluated with micro granular activated carbon (μGAC: 508 μm), coarse powder activated carbon (cPAC: 197 μm), powder activated carbon (PAC: 77 μm), and a domestic wastewater effluent spiked with a mixture of amoxicillin, sulfamethoxazole, and levofloxacin with concentrations ranging from 10 to 50 mg/L. The fixed bed adsorber packed with cPAC was the most efficient adsorber running with wastewater spiked with 50 mg/L of each antibiotic and an empty bed contact time (EBCT) of 4.5 min. The spinning submerged filter adsorber configuration also provided high removal effectiveness using a 15 g/L concentration of PAC but with a lower hydraulic retention time (HRT) of 40 min. This adsorption unit can be filled with small PAC particles, unlike packed beds, and PAC concentrations can be increased up to 150 g/L if necessary. It combines adsorption and filtration with a completely mixed mode of operation in which the PAC concentration can be adapted to effluent micropollutant concentrations, making it an interesting alternative for adsorption processes.