Fixed-bed Adsorption Research Articles

Hybrid nano-biocomposite based on polysaccharide and graphene oxide for the practical separation of proteins in a fixed bed adsorption column

Proteins and amino acids are essential to humans and all living beings. Moreover, these compounds are present in the pharmaceutical, food, and cosmetic industries. Proteins need to be purified for use in industry. This work aims to synthesize and apply a nano-biocomposite based on graphene oxide (GO) and agar (polysaccharide) for protein separation and purification. The hydrogel composite was tested for myoglobin (Mb) adsorption, the effect of changing the initial pH in Mb adsorption, and the ionic strength was evaluated. The adsorptive capacity values were higher at pH=5 and 6 and decreased at higher pH values. The increase in NaCl concentration did not affect the adsorptive capacity significantly. The composite exhibited a notorious value of maximum experimental adsorption capacity in the equilibrium of over 790 mg g−1 at pH=5 and 25 °C. As GO interacts with the polymeric agar matrix, resulting in a 3D material, the material developed could adsorb Mb in a fixed bed column and single and binary (BSA+Mb) systems. There are indications that the GO-based composite possibly forms a complex with the peptide ligands of myoglobin, forming a protein corona, making Mb desorption difficult.

Fixed-bed natural gas CO2 adsorption performance of ZSM-5 zeolites impregnated with amines

This research studies the fixed-bed natural gas carbon dioxide (CO2) adsorption performance of ZSM-5 zeolites impregnation with different amines: monoethanolamine (MEA), ethylenediamine (ED), ethylenediaminetetraacetic acid (EDTA), and 4-aminophenol. The structural, morphological, and performance characteristics of the modified zeolites were examined through the use of several analytical techniques. These techniques featured Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The thermogravimetric analysis revealed weight losses in two stages linked to the removal of bound water molecules and the breakdown of the hydroxyl structure. Through fixed bed adsorption experiments, it was discovered that ZSM-5 zeolites functionalized with MEA/ED showed the CO2 adsorption capacity. This study investigated how well four different mathematical models—Clark, Yoon-Nelson, Thomas, and Adams-Bohart—could predict CO2 adsorption breakthrough curves from natural gas using non-linear regression methods. The results showed that all models had very high adjusted determination coefficients (Adj. R²) of over 0.99, indicating they matched the experimental data really well for various adsorbents. The analysis highlighted the models' effectiveness in reflecting adsorption kinetics and capacities, particularly noting the superior performance of the Thomas, Adams-Bohart, and Yoon-Nelson models in capturing uniform breakthrough behaviors. These findings underscore the models' utility in enhancing CO2 removal processes in natural gas purification, which is pivotal for optimizing industrial gas processing systems. These results highlight the efficiency of amine-functionalized ZSM 5 zeolites in capturing CO2 from natural gas streams.

Scale-bridging And Modelling Study of Graphene Shell Composite Adsorption for Dye Removal in Water Treatment

Continuous fixed-bed adsorption is a cost-effective water-treatment method for dye removal. This research examined parameters such as bed heights (5, 7, and 9cm), initial methylene blue (MB) concentrations (10, 15, and 20mg/L), and feed flow rates (8, 10, 12 and mL/min) on fixed-bed adsorption performance. Our findings showed that the performance was improved under longer exhaustion times not only with increasing column bed heights, but also with decreasing initial MB concentrations and feed flow rates. Of note, the Thomas and Yoon-Nelson models accurately described MB adsorption in a fixed-bed column, with R2 values from 0.7525 to 0.9833. Response surface methodology via central composite design optimized column bed heights and feed flow rates on the duration required to achieve 50% of column breakthrough. The coefficient of determination (R2) and analysis of variance demonstrated the significance of the Two Factor Interaction (2FI) model in fitting the actual values. The optimum conditions were determined to be as follows: a bed height of 5cm; a feed flow rate of 8mL/min; and a duration of 54.74min to achieve 50% of column breakthrough. Lastly, a confirmatory test further verified the precision of the proposed optimum conditions with an error of only 0.02%.

Fabrication of CNC-AC bionanosorbents from the residual mass of Magnolia champaca l. Bark after methanol extraction for wastewater treatment: Continuous column adsorption study

In this current study, a new class of multifunctional biobased ecofriendly nanosorbents namely crystalline nanocellulose-activated char (CNC-AC) nanosorbents were fabricated by employing a much more innovative and beneficial solvent evaporation induced phase separation (EIPS) technique. While the crystalline nanocellulose (CNC) were extracted from a very much new, innovative, and beneficial agrowaste source namely banana tree (M. oranta) rachis fibers by conducting a series of chemical treatments like scouring, alkali treatment, bleaching, and acid hydrolysis reactions. Additionally, the biochar were synthesized from the residual mass of Magnolia champaca L. barks after methanol extraction and functionalized by 30 % H3PO4 to improve their overall properties. Besides these the fixed-bed continuous column adsorption study were carried out by optimizing the various influential factors such as preliminary concentration and flow rates of the inlet wastewater solution, along with the nanosorbent bed heights into the applied column. For better understanding the overall physicochemical, thermomechanical, and morphostructural behavior of the newly fabricated polyfunctional CNC-AC bionanosorbents the samples were characterized by conducting FTIR-ATR, FESEM, BET, XRD, TGA analysis. Meanwhile the treated and nontreated water specimens were examined by conducting AAS and UV–vis-NIR techniques. The obtained results recommended that the newly produced CNC-AC nanosorbents have contained a quite number of active edges/binding sites along with substantial sp. surface area (around 316.95 m2/g). Additionally, they possessed a crystallinity index about 59.98 ± 0.027 %, greater thermal steadiness up to 600 °C, and outstanding 2D honeycomb-like mesoporous peripheral surface microstructure with a promising spherical shapes and smaller size nearly 5–10 nm. The highest removal capacity were found at 538.91 mg/g and 455.70 mg/g for Pb2+ and CR respectively. Additionally, for better understanding the experimental breakthrough curves (BTC) were evaluated by several well established column models while the maximum R2 value was found around 0.999 for the Thomas model and reduced chi squire (χ2) value was around 0.0001.

Enhanced continuous lithium extraction using self-designed porous nanosorbent fibers in a fixed-bed system: Optimization and mechanistic insights

This study introduced a novel lithium/aluminum layered double hydroxide (Li/Al-LDH) nanosorbent fiber (Li-PNF) engineered for continuous lithium extraction from brine using a fixed-bed system. These fibers featured a three-dimensional interconnected mesh structure and were distinctively encapsulated with needle-like Li/Al-LDH, exhibiting a layer-by-layer configuration. Compared to conventional Li/Al-LDH, Li-PNFs demonstrated abundant mesoporous structure and larger average pore size, facilitating the mass transfer and molecular diffusion of Li+ ions. Li-PNFs possessed a static lithium adsorption capacity of approximately 13.0 mg/g, with notable selectivity against Na+ and K+. Additionally, the Li+ binding energy across three distinct sites within the atomic structure of Li-PNFs proved advantageous, particularly at the Triangle-site-Al-overlapping-O3, which reached −5.72 eV. Fixed-bed adsorption experiments confirmed that lower feed flow rates, higher initial lithium concentrations, and increased bed heights significantly enhanced the Li+ capture efficiency, achieving up to 23.83 % in a single fixed-bed experiment. Based on the prediction of adsorption penetration curves using four empirical models, it was found that the Clark and Thomas models could accurately predict the behavior of Li+ penetration through the bed. Fixed-bed desorption results indicated that optimal lithium recovery was achieved at lower feed rates, reduced lithium concentrations in the desorption solution, and elevated temperatures. Finally, the excellent cyclic adsorption/desorption performance and low preparation cost of Li-PNF further highlighted its potential for real industrial applications, offering a significant advancement in the field of lithium extraction technology.

Capacities of sorbents prepared by impregnation of inorganic carriers with PEI using different methods

The study presented here focused on the research of adsorbents for the separation of carbon dioxide from flue gas or other waste gases. Specifically, it focused on the possibility of eliminating the permanent problem with the insufficient resistance of inorganic adsorbents to unwanted – parasitic – adsorption of moisture from the processed gas. Based on the promising data published in recent papers regarding the wet impregnation of adsorbents with branched polyethyleneimine (PEI), four methods for the preparation of PEI-impregnated zeolite were tested. Penetration of the agent into the porous structure of the zeolite was achieved by: applying ultrasound, applying vacuum, combining vacuum and overpressure and boiling off the solvent without further operation. The raw zeolite was characterized by X-ray fluorescence spectrometry and X-ray diffractometry and also subjected to textural analysis. The characterization of the impregnated products mainly included thermogravimetric analysis, textural analysis and organic elemental analysis. In addition to gravimetric screening, the adsorption capacities of raw zeolite and impregnated products were primarily determined using a pressure flow-through apparatus with a fixed bed adsorber. The experimental conditions were determined to be close to real industrial installations: temperature during adsorption 20 and 40 °C, pressure during adsorption 600 kPa and 15% volume fraction of CO2 in the gas. Desorption was carried out by a combination of thermal desorption at 80 °C and vacuum. By reproducing the impregnation procedures from the literature, a PEI loading in the range of 4.1–23.7% was achieved, which is significantly lower than the literature sources state for the same preparation procedures. The measurement of textural properties verified that, depending on the value of PEI loading, there is a gradual reduction of the specific surface area, the total pore volume and the virtual disappearance of micropores and small mesopores. Specifically, at a PEI loading of 4%, the BET surface area decreased compared to the pristine zeolite from 29.4 to 2.9 m2 g–1 and at the same time the total pore volume decreased from 0.13 to 0.02 cm3 g–1, etc. The measurement of capacities did not confirm almost any of the results published in the literature. Without exception, the adsorption capacity decreased with the amount of PEI introduced into the zeolite particles. E.g. if a gas with 80% relative humidity and a content of 15% CO2 was used at a pressure of 600 kPa and a temperature of 40 °C, the capacity (by mass) decreased due to impregnation from 2.4% (for raw zeolite) to 0.8% for the sample with PEI mass fraction of 19%. Tests using dry gas resulted in even more marked deterioration. Thus, one can only partially agree with the literature data in the sense that humidity slightly compensates the negative effect of PEI on capacity. The effect, where the capacity increases with increasing temperature due to the replacement of physical CO2 adsorption by its chemisorption in the PEI layer, was also not confirmed. For example, for the above sample, humidity and pressure, the capacity was 0.9% at 20 °C. The impregnation procedure based on boiling off the solvent turned out to be completely unusable and, despite repeated rigorous attempts to reproduce it, did not lead to a product with a measurable capacity. The results of the study can be summarized in the following sentence. The problem is not that the experiments did not lead to a positive result, but above all the fundamental discrepancy between the published data and the attempts to reproduce them.

Comparison of upward and downward flow in high-pressure bulk CO2 gas adsorption on NaY zeolite fixed bed

Adsorption is an appealing technology for the removing of CO2 from natural gas because it can handle high CO2 concentrations at high pressures. The determination of mono-component breakthrough curves provides heat and mass transfer parameters to assess separation effectiveness that can be used for simulation of swing adsorption separation processes (PSA, TSA etc.). However, in lab-scale fixed-bed adsorption, it may be challenging to perform this assessment due to low flow conditions that are usually employed, affecting the flow regimedepending on the operation conditions. In this sense, this work aimed to evaluate the effect of flow regime configurations and difference in gases densities by means of residence time distribution (RTD) analysis in the PSA of CO2 in a NaY zeolite fixed bed , in order to to collect information that satisfy pipeline specifications in industrial applications. A high-pressure lab-scale apparatus was used with NaY particles of 0.7250 mm mean diameter, a 10.5 cm bed height , and a tubular column of 2.0 cm internal diameter. The upward and downward flows were conducted under 528.82 ± 4.59 NmL min−1 inlet mass flow rate, 51 bar, and 30 °C. The RTD analysis was performed to verify the flow regime, and mass transfer zone (MTZ) length was estimated. It was observed that downward flow conditions promoted higher concentration spread than upward flow. RTD analysis showed that downward flow is dominated by laminar convection while the upward flow is dominated by dispersion. MTZ length increased from 0.64 cm in upward flow to 5.81 cm in downward flow. Therefore, assessing CO2 flow conditions and, additionally, the difference in gases densities, are important steps that should be taken when dealing with fluid adsorption under high pressure because different densities between fluid components severely changed and affected flow regime and, consequently, separation effectiveness.

Constructing yeast-modified polypropylene amidoxime membrane toward highly-selective adsorption of U(VI) from seawater

To extract uranium from seawater, the adsorbent needs to have high selectivity for uranium and good hydrophilicity, and could resist biological pollution and prevent Marine microorganisms from blocking chelate sites. For effective uranium extraction, a straightforward crosslinking technique is used to create a highly selective and biofouling-resistant poly(amidoxime) (PAO-Y) membrane. PAO-Y is characterized by FT-IR, SEM, EDS, XPS, BET, WCA and NMR techniques. The effects of solution acidity, concentration, and adsorption time on its adsorption of uranyl ions and vanadyl ions are investigated. The composite material (PAO-Y) exhibits higher selective adsorption and affinity towards U(VI) compared to V(V). In simulated marine environment experiments, the material exhibited an adsorption capacity of 10.39 mg·g−1 for U(Ⅵ), which is five times higher than that for V(V). Furthermore, the adsorption partition constant for U(Ⅵ) is 1.44 × 105 mL·g−1, two orders of magnitude greater than that for V(V). The DFT calculations revealed specific coordination modes between PAO-Y and uranyl/vanadyl ions, elucidating the selective adsorption mechanism of uranium. The pentadentate coordination mode is shown by DFT calculations to be the most stable one. DFT calculations also show that the increase in the number of amino acid groups increases the interaction between the coordinating ligands and uranyl, but decreases the interaction between the coordinating ligands and vanadyl. These findings suggest that PAO-Y effectively enhance the selectivity and affinity towards uranyl ions during uranium extraction from marine environments and may find practical applications. After 15 days of continuous flow of 30 L natural seawater, PAO-Y obtained a total uranium capture capacity of 1.969 mg·g−1 in the fixed-bed adsorption system, making it a suitable candidate for uranium extraction from natural seawater.

Dynamic behavior of a fixed-bed adsorption column for acid red removal using natural Algerian cactos

In this work, the ability of Natural Algerian Cactus (NAC) to adsorb Acid Red (AR) from aqueous solution was investigated in a fixed-bed column. Scanning Electron Microscopy (SEM) was employed to examine the surface of the biosorbent, Fourier Transform Infrared Spectroscopy (FTIR) was utilized to analyze the chemical composition of NAC, and Brunauer-Emmett-Teller (BET) analysis was conducted to determine the surface area of NAC. We examined the effects of flow rate and influent concentration of AR on the efficiency of the fixed bed. Additionally, we analyzed the sorption of AR using the Thomas and Yoon-Nelson models at various dye concentrations and flow rates to predict breakthrough curves and determine the characteristic parameters of the fixed bed sorption column. The applied models were found to describe the NAC column biosorption process. The obtained results show that the natural Algerian cactus is an efficient Acid Red biosorbent from its aqueous solutions. A sorption capacity of 39.51 mg/g was recorded for the highest concentration (100 mg/l) at a flow rate of 0.8 mL/min while for the highest flow rate (2 mL/min), the sorption capacity attained 30.27 mg/g for a concentration of 50 mg/l. However, the longest breakthrough time was noted for the lowest concentration and flow rate respectively (tb=21h and te=38h for 50mg/l and 0.8 mL/min).

Oily Wastewater Treatment by Using Fe3O4/Bentonite in Fixed-Bed Adsorption Column

Oily wastewater is a major environmental issue resulting from different industrial and manufacturing activities. Contaminated water with oil represents a significant environmental hazard that can harm numerous life forms. Several methodologies have been tested for the removal of oily wastewater from aqueous solutions, and adsorption in a flow-through reactor is an effective mechanism to reduce these effluents. This study focuses on evaluating the ability of Fe3O4/Bent material to adsorb gasoline emulsion from a solution using a fixed-bed column, and it involves analyzing the resulting breakthrough curves. The FT-IR, SEM, EDX, and XRD techniques were used to characterize Fe3O4/Bent. Various ranges of variables were examined, including bed height (2–4 cm), flow rate (3–3.8 mL/min), and initial concentration (200–1000 mg/L), to determine their impacts on the mass transfer zone (MTZ) length and the adsorption capacity (qe). It was shown that a higher bed height and a lower flow rate contributed to a longer time of breakthrough and exhaustion. At the same time, it was noted that under high initial gasoline concentrations, the fixed-bed system rapidly reached breakthrough and exhaustion. Models like the Yoon–Nelson and Thomas kinetic column models were employed to predict the breakthrough curves. Thomas and Yoon–Nelson’s breakthrough models provided a good fit for the breakthrough curves with a correlation coefficient of R2 > 0.95. Furthermore, with a fixed-bed system, the Thomas and Yoon–Nelson models best describe the breakthrough curves for gasoline removal.

Fixed-bed adsorption for industrial wastewater purification: An in-depth review

Fixed-bed adsorption for industrial wastewater purification: An in-depth review

Non-Idealities in adsorption thermodynamics for CO2 capture from humid natural gas using CALF-20

The focus of this article is on CO2 capture from natural gas under humid conditions using CALF-20. Configurational-Bias Monte Carlo (CBMC) simulations are used to investigate adsorption of CO2/CH4/H2O mixtures in CALF-20 with varying relative humidities in the bulk gas phase. The CBMC simulations reveal that the mixture adsorption equilibrium shows strong deviations from the estimations of the Ideal Adsorbed Solution Theory (IAST). CBMC simulations for mixture adsorption of the constituent binary pairs, CH4/H2O, and CO2/H2O, reveal that the origin of thermodynamic non-idealities stem from segregated nature of the adsorbed phase and inhomogeneous distribution of guest adsorbates within the pore landscape of CALF-20. The extent and nature of the segregation depends strongly on the % relative humidity of the bulk gas mixture.The important message that emerges from this investigation is the need to incorporate the Real Adsorbed Solution Theory (RAST) for quantitative modelling of fixed-bed adsorbers in natural gas purification with CALF-20.

Eco-friendly and cost-effective synthesis of hierarchical porous HKUST-1 from thin waste electric cables for enhanced cationic dye removal

HKUST-1, as a type of metal-organic framework (MOF), has attracted significant interest for various applications. However, its use for adsorption applications is hindered by its microporous structure, which negatively impacts the diffusion and mass transfer of large particles (> 2 nm). Concurrently, waste electric cables from discarded vehicles and electronic equipment pose significant environmental challenges. To address these issues, we developed a novel recycling method using copper hydroxide recovered from waste-thin electric cables as the metal source for synthesizing hierarchical porous HKUST-1 (W) using a green approach at a low temperature. The resulting HKUST-1 (W) exhibited interesting properties compared to the typical HKUST-1 (C) synthesized from commercial precursors, showing a microporous-mesoporous structure with enhanced molecular mass transport, while HKUST-1 (C) exhibited only micropores. Moreover, the waste-derived HKUST-1 (W) formed interconnected small particles with enhanced methylene blue (MB) removal properties compared to HKUST-1 (C), mainly due to its hierarchical porous structure facilitating easy mass transfer of MB. To evaluate the industrial potential of our adsorbent, we conducted a fixed-bed adsorption column (FBAC) experiment, which showed that HKUST-1 (W) achieved a high removal efficiency of 99 %, confirming its effectiveness as a dye adsorbent in both batch experiments and a FBAC. This approach opens new perspectives in applying upcycled waste-based materials in synthesizing hierarchical porous MOFs.

Ordered Mesoporous Carbon as Adsorbent for the Removal of a Triphenylmethane Dye from Its Aqueous Solutions.

A nanostructured material, ordered mesoporous carbon (OMC), was synthesised in metal- and halide-free form and its use for the sequestration of crystal violet, a hazardous triphenylmethane dye, is reported for the first time. The OMC material is characterised using scanning transmission electron microscopy with energy-dispersive spectroscopy for chemical analysis, by Fourier-transform infrared spectroscopy, and by nitrogen gas physisorption. The ideal conditions for the uptake of crystal violet dye were determined in batch experiments covering the standard parameters: pH, concentration, contact time, and adsorbent dosage. Experimental data are validated by applying Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin isotherms. The thermodynamic parameters, ΔH°, ΔG°, and ΔS°, are calculated and it has been found that the adsorption process is spontaneous and endothermic with increasing disorder. An in-depth analysis of the kinetics of the adsorption process, order of the reaction and corresponding values of the rate constants was performed. The adsorption of crystal violet over OMC has been found to follow pseudo-second-order kinetics through a film diffusion process at all temperatures studied. Continuous flow column operations were performed using fixed bed adsorption. Parameters including percentage saturation of the OMC bed are evaluated. The exhausted column was regenerated through a desorption process and column efficiency was determined.

Effect of multi-component gas on removal of trace hydrogen sulfide activity from blast furnace gas using activated carbon adsorbent

Abstract In the steel industry, blast furnace gas (BFG) is huge with complex components. The existence of hydrogen sulfide (H2S) in the BFG can produce sulfur dioxide (SO2) after combustion, which will increase the source of SO2 pollution and make the desulphurization more difficult, to be threat to people health. At present, the removal of H2S by dry adsorption with modified activated carbon adsorbent is a high-precision and low-cost desulphurization method. However, the effect of complex gas components in BFG on the adsorption of H2S by activated carbon adsorbent is not sufficient. Based on the fixed bed adsorbent evaluation system, a new type of highly efficient copper-cerium oxide (Cu–Ce–O) modified activated carbon H2S adsorbent was developed. And the effects of carbon monoxide (CO), carbon dioxide (CO2), hydrogen (H2), oxygen (O2), sulfur dioxide and hydrogen chloride (HCl) in BFG on the desulfurization activity of adsorbents were investigated. The results showed that the performance of H2S removal decreased in the presence of CO, CO2, HCl and SO2, and improved in the presence of H2 and O2. Other parameters were also studied which might influence the process. The application of modified activated carbon adsorbent in simulated BFG is basically stable. According to the fitting results of adsorption kinetics for the five adsorption models, as the atmosphere becomes BFG from N2, pore diffusion becomes the main adsorption form. However, the effects of internal diffusion, chemical adsorption and external mass transfer decreased. The Bangham model is the most suitable model to describe H2S adsorption process.

Pure Component and Binary Mixture Adsorption of Light Alkanes and Alkenes on Zeolite NaX at Low Temperatures: Influence of Chain Length.

In this study, the separation of short-chain alkane/alkene pairs by fixed-bed adsorption on zeolite NaX at low temperatures is investigated. Experiments are carried out with pure components and mixtures of ethane/ethene, propane/propene, and n-butane/1-butene in the temperature range between -75 and +40 °C and partial pressures up to 450 Pa. For a short chain length, much stronger adsorption of the alkene is observed. In contrast, with an increase in chain length, the isotherms of alkanes and alkenes of the same chain length become more similar. In addition, a greater influence of temperature on capacity is seen, the shorter the chain length is. In binary mixtures, a strong competition occurs at high total loadings with the alkene displacing the alkane. A characteristic curve is formed for the selectivity in the mixture, which shifts to higher temperatures with an increase in the chain length.

PH-Responsive removal of dyes from wastewater using MXene composited L-Cysteine-grafted HEMA hydrogel: Dynamics, selectivity, regeneration and mechanism

In this work, a MXene composited cysteine-grafted hydroxyethyl methacrylate hydrogel (PHGC/MXene) was successfully synthesized, exhibiting excellent cycle stability and high selectivity toward ionic dyes at different pH. In mixed dyes system, PHGC/MXene exhibited remarkable adsorption selectivity and excellent property of pH-responsivenes for methyl blue (AB93) at pH=2.0 and for methylene blue (MB) at pH=11.0, with maximum adsorption capacity of 207.47 mg/g and 555.56 mg/g, respectively. Even after 12 desorption-regeneration cycles, the removal rates for AB93 and MB remained above 90 %. The study further analyzed the dynamic fixed-bed adsorption behavior of PHGC/MXene for MB, revealing optimal conditions at an inlet concentration of 75 mg/L MB dye and a bed depth of 9 cm. The adsorption mechanism was proposed combined with molecular dynamics simulations. PHGC/MXene emerges as an easily synthesized, highly selective adsorbent with significant potential for the purification of dyes from wastewater in both strongly acidic and strongly alkaline environments.

Porous sodium alginate/cellulose nanofiber composite hydrogel microspheres for heavy metal removal in wastewater

High adsorption capacity, high adsorption rate and reusable adsorbents are urgent needed for removing heavy metals from wastewater. In this study, porous sodium alginate/cellulose nanofiber (SA/CNF) composite hydrogel microspheres were prepared by combining sodium alginate with cellulose nanofibers by microfluidics technology and adding polyethylene glycol (PEG) as pore making agent. The SA/CNF composite hydrogel microspheres could efficiently adsorb heavy metals (Pb2+, Cu2+ and Cd2+) in wastewater. The influencing factors of adsorption process, including pH, temperature, initial concentration, coexisting ions and aquatic environments, were systematically discussed. The adsorption process was more consistent with Langmuir isotherm model and pseudo-second-order model in batch system, indicating the adsorption process was mainly chemical adsorption. The adsorption capacity to Pb2+ obtained by Langmuir model was as high as 544.66 mg/g at 20 °C. Fixed-bed column adsorption experiments demonstrated the excellent performance of the as-prepared SA/CNF microspheres for treatment of the flowing wastewater in a column system. Overall, a highly practical adsorption process based on hydrogel adsorbents was developed for the removal of heavy metals from actual wastewater.

DFT calculation and experiments for Li+/H+ ion-exchange on titanium-based lithium ion-sieves

Titanium-based lithium ion-sieves (H2TiO3) with the layered structure is an excellent adsorbent for lithium recovery from brines, since it has a high theoretical Li+ ions adsorption amount (∼142 mg/g) and a stable structure under acid regeneration. However, the formation of the strong H–O bonds in H2TiO3 leads to a greater energy barrier for re-adsorption of lithium ions, so it would be difficult to reach the theoretical lithium adsorption capacity in practical application. Moreover, the influence of H+ content in brine (pH value) on the Li+ ion adsorption amount is obvious, that limits the lithium recovery efficiency from brines. In this work, Li+/H+ ion-exchange mechanism of layered H2TiO3 (HTO) ion-sieve is investigated through DFT calculation, where the Li+ ion adsorption energies for three kinds of Li+/H+ ion-exchange pathways are calculated, and the order of priority for Li+/H+ ion-exchange is deduced and validated based on the experimental data of Li+ ions adsorption on the prepared nanometer HTO ion-sieve. Then, a quantitative relationship between Li+ ion adsorption amounts on HTO ion-sieve and pH values in Li+-containing solution is developed on the basis of the experimental data. When the nanometer HTO ion-sieve powders are formed into the millimeter PVB-HTO ion-sieve granules for industrial application, it is found that the formation of an acidic micro-environment inside of this PVB-HTO granule obviously reduces the Li+ ions adsorption rate, especially in the initial stage of Li+/H+ ion-exchange process. Finally, an improved strategy of Li+/H+ ion-exchange rate on PVB-HTO granules from a carbonate-type brine is experimentally demonstrated utilizing a batch and a fixed-bed adsorber, respectively.

Removal of volatile organic compounds using fixed bed adsorption: optimization using Taguchi methodology and grey relational analysis

Removal of volatile organic compounds using fixed bed adsorption: optimization using Taguchi methodology and grey relational analysis