Dynamic Adsorption Performance Research Articles

Dynamic CO2 separation performance of nano-sized CHA zeolites under multi-component gas mixtures

To identify and evaluate promising adsorbents for CO2 separation, we synthesized CHA zeolites with different cations (Na+, K+, Cs+) and crystal sizes (45 nm – CHA45 and 500 nm – CHA500), and evaluated their explored CO2 adsorption performance from CO2/N2/He and CO2/CH4/He mixtures. Grand Canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations predicted CO2, N2, and CH4 adsorption isotherms and CO2 mobilities, respectively, which were compared to experimental data. Breakthrough curve analysis was used to assess the CO2 dynamic adsorption performance. The breakthrough curve analysis shows the smaller crystal sizes (45 nm) enhance the CO2 separation due to shorter interacrystalline diffusion pathways. Notably, Cs-CHA45 removed 2.2 times more CO2 from CO2/N2/He than Cs-CHA500. K-CHA45 showed the highest CO2/N2 selectivity (108) and achieved 841mmol g−1 for CO2 capture from N2 and 721mmol g−1 for CO2 from CH4. These findings underscore the potential of CHA nanocrystals for effective CO2 separation in various applications.

Fabrication of highly carboxylated nanofibrous aerogels under mild conditions and their protein adsorption performance

The development of high-performance media for protein adsorption in bio-purification is highly desired, particularly in biological pharmaceuticals. In this study, we demonstrate a simple, versatile and mild strategy to construct a nanofibrous aerogel (NFA)-based adsorption media for protein purification. Pyromellitic dianhydride (PMDA) was selected to in-situ graft onto poly(ethylene-co-vinyl alcohol) (PE-co-PVA) nanofibers in aerogels through liquid phase grafting. The obtained PE-co-PVA/PMDA NFAs (PPNAs) possessed superb underwater elasticity, compression fatigue resistance and shape-memory performance. With an open porous network, abundant adsorption ligands, and surface hydrophilicity, the PPNAs exhibited a significant adsorption capacity of 1019.71 mg/g and a short equilibrium time of 3.0 h, surpassing that of commercial and reported nanofiber-based adsorbents. Additionally, the PPNAs demonstrated good dynamic adsorption performance for protein driven solely by gravity. Furthermore, the PPNAs showed reusability, selectivity, acid and alkaline resistance, and practical potential of extracting lysozyme form egg white solution. The successful scale-up of such aerogel-based adsorbents can open up new way for the development and design of next-generation protein adsorption media for bio-purification applications.

High-Performance Polyamidoxime Porous Membrane Prepared by the In Situ Modification/Nonsolvent-Induced Phase Separation Strategy for Uranium Extraction from Seawater.

The abundance of uranium (U(VI)) reserves in seawater makes it crucial to develop economically efficient methods for uranium extraction from seawater. In this work, an enhanced polyamidoxime porous membrane (PAOM) was fabricated by pre-in situ amidoxime modification combined with nonsolvent-induced phase separation (NIPS). The strategy of in situ modification of the polyacrylonitrile (PAN) solution served to enhance the homogeneity of the reaction and avoid the destruction of the membrane matrix and pore structure. Compared with the control sample (AOPM), PAOM possessed better mechanical strength and hydrophilicity. The introduction of polyvinylpyrrolidone (PVP) formed a porous structure in PAOM, improving spatial accessibility and facilitating the diffusion transport and capture of UO22+ inside the membrane. The more uniform and abundant distribution of amidoxime groups in PAOM gave it ultrahigh adsorption capacity and selectivity. The equilibrium adsorption capacity and Kd value of PAOM were 1.72 and 5.51 times higher than those of AOPM. Meanwhile, PAOM also demonstrated good recyclability, with only a 6.15% decrease in adsorption capacity after seven cycles. Additionally, PAOM exhibited excellent dynamic adsorption performance, and after 14 days of continuous filtration and adsorption, PAOM could extract 2.03 mg·g-1 U(VI) from natural seawater.

Macroporous cellulose microspheres with high specific surface area via semi-dissolved chitosan templating for protein separation

The conflict between macroporous structure and high specific surface area strongly limited the dynamic adsorption performance of chromatographic media. Here, macroporous and high-specific-surface-area cellulose microspheres (PCMs) are prepared by using semi-dissolved chitosan as a dual-functional template and subsequently functionalized with diethylaminoethyl (DEAE) as anion exchangers for protein separation. The dual-functional template strategy leverages dissolved chitosan nanofibers as meso/micropore templates and the undissolved chitosan particles as macropore templates. The macropores of DEAE-PCMs (average size: 0.4–1.2 μm) efficiently decrease mass transfer resistance for fast uptake kinetics. The high specific surface area (272.34 m2/g) provides sufficient ligand sites for ensuring exceptional adsorption capacities. Therefore, the chitosan bifunctional templated PCMs, possessing a macro/meso/microporous structure, are promising candidates for high-performance chromatographic media.

Hierarchical porous carbon nanofibrous membranes with elaborated chemical surfaces for efficient adsorptive removal of volatile organic compounds from air

Volatile organic compounds (VOCs) in the air pose great health risks to humans and the environment. Adsorptive separation technology has proven effective in mitigating VOC pollution, with the adsorbent being the critical component. Therefore, the development of highly efficient adsorbent materials is crucial. Carbon nanofibers, known for their physical–chemical stability and rapid adsorption kinetics, are promising candidates for removing VOCs from the air. However, the relatively simple porous structures and inert surface chemical properties of traditional carbon nanofibers present challenges in further enhancing their application performance further. Herein, a hierarchical porous carbon nanofibrous membrane was prepared using electrospinning technology and a one-step carbonization & activation method. Phenolic resin and polyacrylonitrile were used as co-precursors, with silica nanoparticles serving as the dopant. The resulting membrane exhibited a specific surface area of up to 1560.83 m2/g and surfaces rich in functional O-/N- groups. With a synergistic effect of developed micro- and meso-pores and active chemical surfaces, the carbon nanofibrous membrane demonstrated excellent adsorption separation performance for various VOCs, with comparable adsorption capacities and fast kinetics. Moreover, the membrane displayed remarkable reusability and dynamic adsorption performance for different VOCs, indicating its potential for practical applications.

Enhanced Nitrate Nitrogen Removal from Wastewater Using Modified Reed Straw: Adsorption Performance and Resource Utilization

This paper presents a study on the efficient removal of nitrate nitrogen from wastewater using modified reed straw (MRS) and its subsequent resource utilization. The modification of the reed straw involved the introduction of branching quaternary amine groups to enhance its adsorption capacity for nitrate nitrogen. Experimental investigations were conducted to analyze the impact of packing height, flow rate, and initial solution concentration on the dynamic adsorption performance of the MRS. The results revealed that the maximum dynamic adsorption capacity of the MRS for nitrate nitrogen reached 14.76 mg/g. Furthermore, valuable nitrate nitrogen nutrient solution was successfully recovered through subsequent desorption experiments for resource recycling. Moreover, the application of the MRS led to notable enhancements in column height, fresh weight, chlorophyll content, and nitrogen content of the treated plants, indicating its efficacy in promoting plant growth. Overall, the findings demonstrate that MRS serves as a versatile adsorbent capable of efficient nitrate nitrogen removal and subsequent resource utilization.

The influence of activated carbon fiber paper structure on adsorption performance of cyclohexane

Activated carbon fibers paper (ACFP), made through wet-laid technology, had exhibited promising adsorption performance compared with granular and powdered activated carbon. This study prepared activated carbon fibers papers with different fibrous structures and investigated the dynamic adsorption performance of thin-layered ACFP against cyclohexane gas. The effects of inter-fiber pore size, dilution degree of activated carbon fibers, and porosity of the paper sheet on the adsorption performance were explored. The Bed Depth Service Time (BDST) model was employed for fitting and calculation, and the Flowdict module in Geodict software was used to analyze the flow field within the paper sheet. The results indicated that the inter-fiber pore size variation of ACFP had no significant effect on its adsorption breakthrough curve against cyclohexane gas. However, as the dilution degree of activated carbon fibers in the ACFP increased, the breakthrough time prolonged, and the adsorption utilization efficiency of activated carbon fibers continuously improved. Furthermore, decrease of ACFP porosity significantly impaired the adsorption performance. When the porosity decreased from 95.4 % to 91.4 %, the breakthrough adsorption capacity decreased from 134 mg/g to 95 mg/g, and the critical bed thickness increased from 0.029 cm to 0.044 cm.

Dynamic Intermediate-Temperature CO2 Adsorption Performance of K2CO3-Promoted Layered Double Hydroxide-Derived Adsorbents.

The dynamic adsorption characteristics of K2CO3-promoted layered double hydroxides (LDHs)-based adsorbent, with organic and inorganic anion intercalation, were studied. MgAl-LDH, K2CO3/MgAl-LDH, and K2CO3/MgAl-LDH(C16) with varying K2CO3 loads were prepared and used for intermediate-temperature CO2 sequestration. The adsorbent was thoroughly characterized using X-ray diffraction, Brunauer-Emmett-Teller, scanning electron microscopy, and Fourier Transform Infrared Spectroscopy techniques, which revealed enhanced adsorption properties of MgAl-LDH, due to K2CO3 promotion. Thermogravimetric CO2 adsorption tests on the constructed adsorbent materials showed that the 12.5 wt% K2CO3/MgAl-LDH(C16) adsorbent with organic anion intercalation exhibited optimal adsorption activity, achieving an adsorption capacity of 1.12 mmol/g at 100% CO2 and 350 °C. However, fixed-bed dynamic adsorption tests yielded different results; the 25 wt% K2CO3/MgAl-LDH prepared through inorganic anion intercalation exhibited the best adsorption performance in low-concentration CO2 penetration tests. The recorded penetration time was 93.1 s, accompanied by an adsorption capacity of 0.722 mmol/g. This can be attributed to the faster adsorption kinetics exhibited by the 25 wt% K2CO3/MgAl-LDH adsorbent during the early stages of adsorption, thereby facilitating efficient CO2 capture in low-concentration CO2 streams. This is a conclusion that differs from previous reports. Earlier reports indicated that LDHs with organic anion intercalation exhibited higher CO2 adsorption activity in thermogravimetric analyzer tests. However, this study found that for the fixed-bed dynamic adsorption process, K2CO3-modified inorganic anion-intercalated LDHs perform better, indicating their greater potential in practical applications.

Baking-inspired pore regulation strategy towards a hierarchically porous carbon for ultra-high efficiency cationic/anionic dyes adsorption

Converting waste resource into porous carbon toward contaminant capturing is a crucial strategy for realizing “treating waste with waste”. Inspired by bread baking process, the soybean meal activated carbon (SAC) with multimodal pore structures was developed via thermally remodeling the pores of waste soybean meal. The obtained SAC-3-800 has ultra-high specific surface area (3536.952 m2/g), as well as a hierarchically porous structure. SAC-3-800 exhibits extremely high adsorption capacity for methylene blue (MB) (3015.59 mg/g), methyl orange (MO) (6486.30 mg/g), and mixed dyes (8475.09 mg/g). The hierarchically porous structure enabled fast adsorption kinetics of SAC-3-800 for MB and MO (∼30 min). Additionally, SAC-3-800 shows excellent dynamic adsorption and regeneration performance, exhibiting great potential for industrial applications. This work showcases a feasible method for synthesizing hierarchically porous carbon with outstanding adsorption performance that can simultaneously achieve efficient treatment of dye-wastewater and value-added utilization of waste resources.

Highly permeable nanofibrous polyamide membranes for multi-component wastewater treatment: Exploration of multiple separation mechanism

Multi-component wastewater containing a variety of organic toxins, e.g., dyes and inorganic particulates induces serious environmental concerns, which must be addressed by innovative approaches instead of conventional chemical and physical processes, which are limited by purification efficiency, secondary pollution, and cost-effectiveness. Therefore, it is important to find new avenues of purification methods that are both sustainable and effective. Ultra-fine nanofibrous microfiltration membranes were fabricated by multi-nozzle electrospinning of polyamide-66 (PA-66) and were employed to remove 0.2-μm-nanoparticles and dyes simultaneously from wastewater through filtration and dynamic adsorption performance, in an attempt to discover a one-step filtration system for both dyes and nanoparticles. The fiber diameter and surface morphology of the nanofibrous membranes varied with the concentrations of polyamide solutions, where the ultra-fine nanofibrous membrane exhibited optimum mechanical properties at a specific concentration of PA-66 (11 wt%). The nanofibrous membranes had adsorption capabilities of 133.3 and 204.5 mg/g, respectively, against both anionic dyes (e.g., metanil yellow) and cationic dyes (e.g., chrysoidine), respectively. The membrane also selectively filtrated fine nanoparticles with a nearly 100% rejection ratio. A multiple separation mechanism, including adsorption based on electrostatic interaction, hydrogen bonding interaction, and hydrophobic interaction, as well as depth filtration, was proposed. As an applicable demonstration, the spiral wound cartridge fabricated by PA-66 nanofibrous membrane was used for a simulated multi-component wastewater treatment that contained dyes and nanoparticles of different concentrations. During the multicomponent test at flow rate 1 mL/min, a rejection rate of 97% and greater than 99% were achieved against dyes and nanoparticles, respectively.

One-step synthesis of iron and nitrogen co-doped porous biochar for efficient removal of tetracycline from water: Adsorption performance and fixed-bed column

Here, Fe/N co-doped porous biochars (FeNKBCs) were obtained by grinding corncob, CH3COOK, FeCl3·6H2O, and C3H6N6 via one-step synthesis and were applied to remove antibiotics from wastewater. Notably, CH3COOK had an excellent porous activation ability. The developed nanotubular structure of Fe1N2KBC had a high pore volume (Vtotal) (1.2131 cm3/g) and specific surface areas (SSA) (2083.54 m2/g), which showed outstanding sorption abilities for TC (764.35 mg/g), OTC (560.82 mg/g), SMX (291.45 mg/g), and SMT (354.65 mg/g). The adsorption process of TC was controlled by chemisorption. Moreover, Fe1N2KBC has an excellent dynamic adsorption performance (620.14 mg/g) in a fixed-bed column. The properties of SSA, Vtotal, and the content of graphite N and Fe–N were positively correlated with TC adsorption capacity. The high performance of TC removal was related to π-π stacking, pore-filling, hydrogen bond, and electrostatic interaction. Fe1N2KBC possessed stable sorption amounts in pH 2–12 and actual water, and well reuse performance. The results of this work present an effective preparation method of Fe/N porous biochar for TC-contaminated water remediation.

Effect of montmorillonite nanosheets on the adsorption performance of hydrogel beads and the study of column adsorption

In this work, hydrogel beads with 3D network structure were successfully prepared using montmorillonite nanosheets (MMTNS) combined with macromolecule polymers. Batch adsorption tests revealed that the increase in exfoliation degree of MMTNS was beneficial to improve the methylene blue (MB) adsorption on hydrogel beads (HB). In addition, the HB with 25 % MMTNS-3 dosage achieved high mechanical strength and reached the maximum adsorption capacity of 543.1 mg/g. Effects of MB concentration (40–120 mg/L), adsorbent dosage (1–1.5 g) and flow rate (5–15 mL/min) on fixed-bed column adsorption indicated that the HB column exhibited an excellent dynamic adsorption performance and recycling performance, much better than the D113 resin. The good fits of Pseudo-first-order model and Pseudo-second-order model and a better Langmuir model fitting result implied a monolayer chemical adsorption and physical adsorption nature of MB on HB. Moreover, scanning electron microscope combined with the energy dispersive spectrometer, fourier transform infrared spectroscope and X-ray photoelectron spectroscopy measurements indicated that the adsorption mechanism was mainly attributed to Ca ion-exchange and chemical bonding of –COOH and –OH groups with MB. Such hydrogel beads showed a good potential in the application of practical wastewater treatment.

Pore Space Partition Synthetic Strategy in Imine-linked Multivariate Covalent Organic Frameworks.

Partitioning the pores of covalent organic frameworks (COFs) is an attractive strategy for introducing microporosity and achieving new functionality, but it is technically challenging to achieve. Herein, we report a simple strategy for partitioning the micropores/mesopores of multivariate COFs. Our approach relies on the predesign and synthesis of multicomponent COFs through imine condensation reactions with aldehyde groups anchored in the COF pores, followed by inserting additional symmetric building blocks (with C2 or C3 symmetries) as pore partition agents. This approach allowed tetragonal or hexagonal pores to be partitioned into two or three smaller micropores, respectively. The synthesized library of pore-partitioned COFs was then applied for the capture of iodine pollutants (i.e., I2 and CH3I). This rich inventory allowed deep exploration of the relationships between the COF adsorbent composition, pore architecture, and adsorption capacity for I2 and CH3I capture under wide-ranging conditions. Notably, one of our developed pore-partitioned COFs (COF 3-2P) exhibited greatly enhanced dynamic I2 and CH3I adsorption performances compared to its parent COF (COF 3) in breakthrough tests, setting a new benchmark for COF-based adsorbents. Results present an effective design strategy toward functional COFs with tunable pore environments, functions, and properties.

Breakthrough curve modeling for lysozyme by ion-exchange nanofiber membrane: Linear and nonlinear analysis

BackgroundNanofibers prepared by electrospinning technology are widely used as an adsorber in protein purification processes. However, the evaluation of dynamic adsorption performance has not been reported yet. MethodsLysozyme was subjected to assess dynamic adsorption of weak ion exchange nanofiber membranes by applying a continuous flow system. Different operating conditions were selected to study the lysozyme adsorption breakthrough curve, which included four factors: pH, feedstock lysozyme concentration, feed flow rate, and stacked membrane layers. The breakthrough curve was applied to analyze the performance for dynamic binding with lysozyme as a model protein. In addition, the adsorption models (Bohart-Adams, Thomas, Yoon-Nelson, and BDST) were fitted to the breakthrough curves using linear and nonlinear regression analysis. Significant findingsIt was found that the four operating parameters had considerable influences on the dynamic adsorption performance. Among these models, the breakthrough curve was well-fitted by using linear regression analysis of the Yoon-Nelson model. The breakthrough curve characteristics could be used to describe the dynamic binding performance of interested membranes to lysozyme molecules.

Experimental research of alkali metals modified Mg/DOBDC metal organic framework as high capacity CO2 adsorbent

In this paper, novel M−Mg/DOBDC (M = Li, Na, K) composites (a MOF built of Mg(OAc)2·4H2O and MOAc (M = Li, Na, K) linked by 2,5-dioxido-1,4-benzenedicarboxylate (DOBDC) ligands) were prepared for the first time by doping alkali metals in Mg/DOBDC MOF. The CO2 dynamic adsorption performance of the novel synthesized composite was experimentally investigated, including different alkali metal doping amounts and alkali metal species. The structural morphology and CO2 adsorption of the composites were characterized by XRD, FT-IR, SEM, EDX, BET, CO2-TPD and TGA. Ten cycles of adsorption–desorption tests were performed on the M−Mg/DOBDC after doping with alkali metals. In addition, the CO2 adsorption process of the materials was simulated using various models. The results showed that the introduction of the alkali cation M+ would coordinate with the active site of the metal center and had high affinity and activation ability for CO2. The composite with the best dynamic CO2 uptake after the modification of Li, Na and K alkali metals was 0.5 K-Mg/DOBDC with an adsorption capacity of 14.93 mmol g−1 (0.1 MPa, 25 °C), which was 3.44 times higher than that of the parent material Mg/DOBDC. That was higher than the previously reported CO2 capture performance.

Biochar with nanoparticle incorporation and pore engineering enables enhanced heavy metals removal

Biochar is a desirable candidate for environment remediation of heavy metals in water due to wide availability and environmental-friendliness. In practical application, however, biochar suffers from inferior adsorption capacity owing to poor surface properties and limited pore structure. Herein, a combined strategy of nanoparticle incorporation and pore engineering was proposed to synthesize KOH activated porous biochar embedded MgO composite (K-MgO-RB) derived from waste ramie. Specifically, KOH as the chemical activator developed regular porous structures, which not only facilitated the increase in surface area and the MgO incorporation, but also effectively suppressed the aggregation of MgO nanoparticles due to the nanoconfinement effect. Thanks to the favorable nanostructures and incorporation of nano-MgO, K-MgO-RB presented superior adsorption capacities for Pb2+ (1276.46 mg/g) and Cd2+ (861.82 mg/g), which was approximately 100 and 19 times higher than those of the pure RB, respectively. The adsorption mechanism study indicated that electrostatic effect, precipitation, ion exchange, and cation-π electrons complexation were the dominant adsorption driving force of Pb2+ and Cd2+. Further, outstanding dynamic adsorption performance of 3480 mL (174 BV) for Pb2+ and 2520 mL (126 BV) for Cd2+ in fixed-bed column experiment, exceptional reusability as well as low economic cost demonstrated the excellent potential of K-MgO-RB for practical application.

Polyacrylonitrile (PAN)/Freeze-dried Chitosan (FCS)-NaY zeolite triple layer nanostructure fibrous adsorptive membrane (PAN/FCS-NaY TNAM) for Cu(II) and Pb(II) ions removal from aqueous solutions

In this study, an innovative PAN/FCS-NaY TNAM was fabricated using an electrospinning technique for Cu(II) and Pb(II) removal from contaminated water. Top and bottom fibrous layers (M1) were fabricated using a combination of FCS and PAN blends. Middle layer (M2) was electrospun from pure PAN solution and loaded with NaY zeolite particles. The physicochemical properties of the material and fibrous samples were investigated through SEM, FTIR-ATR, DSC, AFM, DMTA analysis, and contact angle measurement. The effective parameters, including initial ions concentration, time, reusability, and pH on the dynamic adsorption performance of the prepared membrane and its stability in the aqueous medium for Cu(II) and Pb(II) ions removal were investigated at a pressure of 0.006 bar. Dynamic metal ions adsorption was modeled using dynamic filtration prediction models such as Thomas and Yoon-Nelson. The fabricated nanostructure fibrous membranes with the removal percentage of Cu(II) and Pb(II) ions (94.6% and 98.7%, respectively) under the optimal operating conditions (initial concentration: 50 ppm, time: 10 min, and pH: 4.6), high compatibility in modeling dynamic filtration (R2 > 0.99), high pure water flux (298 LMH), suitable reusability (four-cycle without significant reduction in adsorption) as well as long-term stability, can be as potential filters in water treatment applications.

Construction of polydopamine-functionalized phosphate-intercalated Mg[sbnd]Fe layered double hydroxide for efficient removal of U(VI)

Polydopamine-coated phosphate-intercalated MgFe layered double hydroxides (PDA/phos-LDH) were fabricated to capture U(VI). Phosphate was intercalated in the layers of LDH because of its strong affinity for U(VI) species and the PDA was employed to provide massive binding sites for U(VI) by promoting the dispersion of LDH in the matrix. Experimental results revealed that the introduction of phosphate and PDA significantly increased the removal amount for U(VI) because of the increased functional groups (including PO43−, -OH, -NH2 and aromatic ring). The highest removal amount of PDA/phos-LDH (pH = 3.0, T = 298 K) reached 912.0 mg/g within 60 min, which was higher than many other LDH-based adsorption materials. After 5 repeated uses, the uptake percentage was still as high as 81.4 %. In addition, the excellent dynamic adsorption performance further confirmed the potential of PDA/phos-LDH in the actual processing of U(VI)-containing wastewater. Ion exchange, complexation, electrostatic attraction, cation-π interaction and precipitation were confirmed to play prominent roles in U(VI) removal. In a word, PDA/phos-LDH was an exceptional adsorbent for U(VI) immobilization.

Nanostructured carboxylated-wood aerogel membrane for high-efficiency removal of Cu (II) ions from wastewater

Heavy-metal pollution is a significant environmental issue that has raised global concern due to its harmful impact on humans and the natural ecosystem. Heavy metal pollution poses several challenges in terms of remediation, including low adsorption capacity and efficiency, scale-up issues and non-degradability. Here, we developed an eco-friendly tunable dual-wavelength absorption mesoporous wood aerogel (TDWA) for removal of Cu2+ ions from wastewater based on wood nanotechnology and carboxylated functionalization treatment. Nanostructured pores generated from the cell walls with carboxyl groups due to the removal of most lignin/hemicellulose and 2,2,6,6-tetramethylpiperidine oxidation. Mechanical compression was parallelly applied to the transverse direction of TDWA resulted in removing micron-scale cell cavity and intercellular, which significantly improved the dynamic adsorption performance with an excellent Cu2+ adsorption capacity of 115 mg g−1. This value is superior to most wood-based adsorption membrane as wastewater mainly flowed through the continuous microfibril network in the cell wall. The double-layer mesoporous TDWA membrane (5 mm) possessed a favorable removal efficiency (99.83 %) even after 5-cyclic adsorption (92.34 %). The invented nanostructured TDWA membrane in the current study has promising potential to substitute the present plastic-based membrane in the realistic Cu2+ adsorption because of the facile technology, renewability and high removal efficient, as well as the complete biodegradability.

Mussel inspired synthesis of polydopamine/polyethyleneimine-grafted fly ash composite adsorbent for the effective separation of U(VI)

Polydopamine/polyethyleneimine-grafted fly ash composite (PDA/PEI/FA), an efficient multifunctional adsorbent for U(VI) with excellent separation efficiency (94.5 %) and capacity (422.5 mg/g), was synthesized by grafting PDA and PEI on FA via Mussel inspiration and Michael addition reaction. The introduction of PDA and PEI had brought numerous functional groups with fine affinities to uranium, like catechol, amino and imino, causing good U(VI) separation performances. Langmuir and Pseudo-second-order models were well matched with experimental data, illustrating the U(VI) separation on PDA/PEI/FA was a homogeneous chemical adsorption process. After five cycles, the U(VI) adsorption efficiency for PDA/PEI/FA was still up to 90.2 %, implying that PDA/PEI/FA possessed good stability and reusability. Besides, the good dynamic adsorption performances of PDA/PEI/FA further demonstrated that PDA/PEI/FA was an ideal adsorbent for the practical wastewater treatment. According to the characterization results, U(VI) was absorbed by PAD/PEI/FA through complexation, redox reaction, electrostatic attraction and hydrogen bonding. Given the above, PDA/PEI/FA showed good practical application prospect in U(VI) separation.