Adsorption-desorption Cycles Research Articles

Promising CO2 Capture and Effective Iodine Adsorption of Hyper-Cross-Linked Conjugated Porous Organic Polymers Prepared from a Cyclopentannulation Reaction.

Three novel conjugated porous organic polymers, denoted as C-POP1-3 and which consist of alternating pyrene cores with various contorted fluorene surrogates, were successfully synthesized from a versatile one-pot palladium-catalyzed [3+2] cyclocondensation reaction. The resulting polymers were obtained in excellent yields and displayed weight-average molecular weights (Mw) ranging from 12.2 to 20.2 kg/mol with polydispersity indices (Mw/Mn) ranging between 1.8 and 2.4, suggesting that the molecular masses are narrowly distributed and thus implying homogeneous polymer chains. Thermal stability exploration of C-POP1-3 by thermogravimetric analysis (TGA) revealed an impressive robustness with a 10% weight reduction temperature attaining 485 °C. Investigation of the inherent microporosity properties of C-POP1-3 via nitrogen adsorption experiments using Brunauer-Emmett-Teller (BET) theory discloses their surface areas which reach up to 560 m2 g-1 and pore volumes averaging 0.47 cm3 g-1. The target conjugated polymers were explored as adsorbents disclosing a maximum carbon dioxide adsorption of 83.0 mg g-1 at 273 K and low pressure for C-POP1, whereas iodine sorption tests portrayed prominent outcomes, notably for C-POP3 which proved to owe a strong affinity toward the hitherto mentioned halogen by achieving a maximum adsorption of 2220 mg g-1. Additionally, recyclability experiments confirmed the possibility to regenerate the polymers' adsorption capabilities even after seven consecutive cycles of adsorption-desorption cycles, which qualify them as auspicious iodine adsorbents.

Synthesis of sodium polystyrene sulfonate resins for the removal of methylene blue from wastewater

BackgroundThe treatment of dye residue water pollution is a hot research topic, so it is necessary to prepare a resin which can adsorb dye efficiently. MethodsThe sodium polystyrene sulfonate (PSSNa) were prepared by the sulfonation reaction of styrene resins with concentrated sulfuric acid and applied for Methylene Blue adsorption in wastewater. The structure of PSSNa was characterized by FT-IR, SEM, XPS and XRD. Significant findingsThe results show that the maximum adsorption capacity is 16.89 mg∙g−1. The adsorption processes of Methylene Blue with PSSNa conforms to the pseudo-second-order kinetic model and the Langmuir isotherm adsorption model, which means that the adsorption process follows single-molecular layer adsorption mechanism. The characteristic group (–SO3−) of the exchange resin interacts electrostatic with MB. Good desorption was achieved with 1 mol·L−1 HCl solution, and the resin retained good adsorption capacity after 5 adsorption-desorption cycles. In practical applications, PSSNa exhibits a good removal efficiency for dyes containing MB in lake water. These results provide a reference for the treatment of printing and dyeing wastewater by resin adsorption materials.

Separation of Mono-/Divalent Ions via Controlled Dynamic Adsorption/Desorption at Polythiophene Coated Carbon Surface with Flow-Electrode Capacitive Deionization.

Capacitive deionization for selective separation of ions is rarely reported since it relies on the electrostatic attraction of oppositely charged ions with no capability to distinguish ions of different valent states. Using molecular dynamic simulation, a screening process identified a hybrid material known as AC/PTh, which consists of activated carbon with a thin layer of polythiophene (PTh) coating. By utilizing AC/PTh as electrode material implementing the short-circuit cycle (SCC) mode in flow-electrode capacitive deionization (FCDI), selective separation of mono-/divalent ions can be realized via precise control of dynamic adsorption and desorption of mono-/divalent ions at a particular surface. Specifically, AC/PTh shows strong interaction with divalent ions but weak interaction with monovalent ions, the distribution of divalent ions can be enriched in the electric double layer after a couple of adsorption-desorption cycles. At Cu2+/Na+ molar ratio of 1:40, selectivity toward divalent ions can reach up to 110.3 in FCDI SCC mode at 1.0V. This work presents a promising strategy for separating ions of different valence states in a continuously operated FCDI device.

Efficient removal of tizanidine and tetracycline from water: A single and competitive sorption approach using carboxymethyl cellulose granulated iron-pillared clay

This study deals with the development of a granulated Fe-pillared clay (Fe-PC) using carboxymethylcellulose (CMC) as a binder to present it as an innovative adsorbent for the individual and competitive adsorption of tetracycline (Tc) and tizanidine (Tz) from water. An optimum pH value of 7 was determined for both individual and multi-component adsorption. The optimal dosage of granulated Fe-PC was determined to be 1.5 g/L for Tz and 3 g/L for Tc, resulting in constant removal rates of 80 % for Tc and 90 % for Tz. Tizanidine showed a higher affinity for powdered or granulated Fe-PC compared to tetracycline, due to its smaller molecular size and increased amine functional groups. Consequently, Tz showed improved kinetic rates (initial pseudo-second order sorption rates of 170.79 and 25.62 mg/g.h for Tz and Tc, respectively) and equilibrium capacities (maximum monolayer adsorption capacity of granulated Fe-PC at room temperature over Tc and Tz, 54.89 mg/g and 66.40 mg/g). Granulation affected the kinetic rate for both adsorbates, albeit with a more pronounced effect for Tc. The adsorption of Tz was less sensitive to temperature changes, indicating a lower enthalpy change of adsorption (14.24 and 77.91 kJ/mol for Tz and Tc, respectively). HCl for Tc and NaCl for Tz were identified as optimal desorption eluents, confirming the involvement of cation exchange in Tz adsorption. Surface functional group analysis confirmed the proposed complexation mechanisms. Tz consistently showed a higher affinity for granular Fe-PC than Tc, especially at lower adsorbent dosages. This article provides a comprehensive insight into the characterization of the prepared adsorbents and their cyclic adsorption-desorption performance for Tc and Tz.

Comparative Analysis of Hydrogel Adsorption/Desorption with and without Surfactants

In this particular study, a hydrogel known as SAP-1 was synthesized through the grafting of acrylic acid-co-acrylamide onto pullulan, resulting in the creation of Pul-g-Poly (acrylic acid-co-acrylamide). Additionally, a sponge hydrogel named SAP-2 was prepared by incorporating the surfactant sodium dodecyl benzene sulfonate (SDBS) into the hydrogel through free radical solution polymerization. To gain further insight into the composition and properties of the hydrogels, various techniques, such as Fourier transform infrared spectroscopy, hydrogen nuclear magnetic resonance (1H NMR), atomic absorption spectroscopy, and field emission scanning electron microscopy (FE-SEM), were employed. Conversely, the absorption kinetics and the equilibrium capacities of the prepared hydrogels were investigated and analyzed. The outcomes of the investigation indicated that each of the synthesized hydrogels exhibited considerable efficacy as adsorbents for cadmium (II), copper (II), and nickel (II) ions. In particular, SAP-2 gel displayed a remarkable cadmium (II) ion absorption ability, with a rate of 190.72 mg/g. Following closely, SAP-1 gel demonstrated the ability to absorb cadmium (II) ions at a rate of 146.9 mg/g and copper (II) ions at a rate of 154 mg/g. Notably, SAP-2 hydrogel demonstrated the ability to repeat the adsorption–desorption cycles three times for cadmium (II) ions, resulting in absorption capacities of 190.72 mg/g, 100.43 mg/g, and 19.64 mg/g for the first, second, and third cycles, respectively. Thus, based on the abovementioned results, it can be concluded that all the synthesized hydrogels possess promising potential as suitable candidates for the adsorption and desorption of cadmium (II), copper (II), and nickel (II) ions.

Insight into adsorption properties and mechanism of geopolymer adsorbents with inherent alkali release for tetracycline

The crux to practical application of geopolymer adsorbents for antibiotics that are easily protonated and deprotonated is to clarify the dynamic adsorption mechanism of geopolymer with intrinsic alkaline release. The adsorption properties, adsorption mechanism, adsorption-desorption cycle and waste adsorbent regeneration based on the geopolymer adsorbent for adsorbing tetracycline under the spontaneous dynamic pH conditions were systematically investigated by experiment, characterization and density functional theory. The results confirmed that the structures of tetracycline depended on dynamic pHs of adsorption systems changed by geopolymer adsorbent. The electrostatic interaction assisted by hydrogen-bonding and n-π interaction dominated the adsorption process when the dynamic pHs were less than 7. And the hydrogen-bonding and n-π interaction provided the possibility of weak adsorption effect in highly alkaline environments. The geopolymer powder exhibited outstanding adsorption efficiency (∼95.62%, 30 min) due to the strong electrostatic adsorption between electronegative skeleton of geopolymer and zwitterions species tetracycline under dynamic pH range of 4–6.3 and fitted the pseudo-second-order model. The outstanding competitive adsorption properties in NaCl solution, adsorption (4 times)-desorption (3 times) cycle properties and regenerative property of waste adsorbent were exhibited. The mechanism study based on the dynamic pHs which is closer to actual conditions can provide important reference for practical application of easy preparation and low cost geopolymer adsorbents.

One-Step Butadiene Purification in a Sulfonate-Functionalized Metal-Organic Framework through Synergistic Separation Mechanism.

Porous materials that could recognize specific molecules from complex mixtures are of great potential in improving the current energy-intensive multistep separation processes. However, due to the highly similar structures and properties of the mixtures, the design of desired porous materials remains challenging. Herein, a sulfonate-functionalized metal-organic framework ZU-609 with suitable pore size and pore chemistry is designed for 1,3-butadiene (C4H6) purification from complex C4 mixtures. The sulfonate anions decorated in the channel achieve selective recognition of C4H6 from other C4 olefins with subtle polarity differences through C-H···O-S interactions, affording recorded C4H6/trans-2-C4H8 selectivity (4.4). Meanwhile, the shrunken mouth of the channel with a suitable pore size (4.6 Å) exhibits exclusion effect to the larger molecules cis-2-C4H8, iso-C4H8, n-C4H10 and iso-C4H10. Benefiting from the moderate C4 olefins binding affinity exhibited by sulfonate anions, the adsorbed C4H6 could be easily regenerated near ambient conditions. Polymer-grade 1,3-butadiene (99.5%) is firstly obtained from 7-component C4 mixtures via one adsorption-desorption cycle. The work demonstrates the great potential of synergistic recognition of size-sieving and thermodynamically equilibrium in dealing with complex mixtures.

Adsorptive removal of recalcitrant organic compounds of compost leachate by epichlorohydrin cross‐linked cyclodextrin copolymer

AbstractHazardous materials in compost leachate pose a threat to the environment, and its treatment has become a concern in recent years. The adsorption process is a highly effective method that is used for treating these contaminants. This research pioneered the application of cyclodextrin‐epichlorohydrin (ECP) copolymer for chemical oxygen demand (COD) removal in compost leachate treatment. It offers a practical and effective approach to addressing environmental concerns associated with COD, with an extremely high adsorption capacity of 11,246 mg/g. Fourier transform infrared (FTIR), x‐ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive x‐ray (EDX) analyses were performed to identify the synthesized ECP. The effects of different parameters on the adsorption process were systematically investigated. Organic compounds removal was also evaluated using response surface methodology (RSM) in relation to process parameters. The maximum removal of COD was achieved in acidic solutions with an agitation speed of 160 rpm and adsorbent dosage of 3 g/L at 60 min. The corresponding maximum removal percentage achieved under the optimum conditions was about 70%. The adsorption process followed pseudo−second order kinetics and Freundlich isotherms models. The adsorption behaviour of ECP was investigated in ionic environment and it was efficiently regenerated for three adsorption–desorption cycles. The ECP showed high adsorption capacity and was found to be cost‐effective for COD removal. It was found to be a sustainable waste management strategy.

Synergy of Post-Crosslinked imprinting strategy and silanol chemistry for the anisotropic construction of molecularly imprinted polymers onto Halloysite nanotubes

Searching for alternative porous substrates which can realize anisotropic preparation of “tailor-made” complementary binding sites is an important way to improve the identification efficiency and interfacial stability of the surface molecularly imprinted polymers (SMIPs). In this work, a functional polymer (FP) with multi-functional properties was firstly synthesized using 3-(isobutenyloxy) propyltrimethoxysilane, 1-(vinylbenzyl) thymidine and cinnamoyloxyethyl methacrylate (CEMA) as monomers, and then FP with post-crosslinking property was covalently deposited onto theoutersurfaceof halloysite nanotubes (HNTs) using silanol chemistry to prepare 2′-deoxyadenosine (dA) imprinted sorbents (HNTs-SMIPs). More than 65 % of dA molecules was captured within the first 2.0 h. The number of high affinity site from the total binding sites of HNTs-SMIPs is estimated to be as high as 73.25 %, and the maximum adsorption amount of HNTs-SMIPs is 48.78 μmol g -1 at 25 °C. The imprinting factor (IF) of HNTs-SMIPs towards dA is 1.89, and 79.49 % the adsorption capacity is remained after five adsorption–desorption cycles. In addition, 70.2 % of the dA from spiked human urine samples can be selectively extracted by HNTs-SMIPs. HNTs-SMIPs have excellent interfacial stability and strong affinity for the template molecule dA, and this work provides a new strategy for the specific separation and enrichment of dA.

Construction of 3D-Printed Sodium Alginate/Chitosan/Halloysite Nanotube Composites as Adsorbents of Methylene Blue.

In this study, sodium alginate/chitosan/halloysite nanotube composites were prepared by three-dimensional printing and characterized in terms of morphology, viscosity, thermal properties, and methylene blue (MB) adsorption performance. The high specific surface area and extensively microporous structure of these composites allowed for effective MB removal from wastewater; specifically, a removal efficiency of 80% was obtained after a 60 min treatment at an adsorbent loading of 1 g L-1 and an MB concentration of 80 mg L-1, while the maximum MB adsorption capacity equaled 376.3 mg g-1. Adsorption kinetics and isotherms were well described by quasi-second-order and Langmuir models, respectively. The composites largely retained their adsorption performance after five adsorption-desorption cycles and were concluded to hold great promise for MB removal from wastewater.

Microwave pyrolysis of waste biomass and synthesis of micro-mesoporous activated carbons: The role of textural properties for CO2 and textile dye adsorption

Hierarchical porous activated carbons (ACs) were efficiently synthesized in less than 2 min using microwaves and phosphoric acid (H3PO4), exhibiting excellent potential as adsorbent for carbon dioxide (CO2) and Methylene Blue (MB). The method emphasizes the development of selective physicochemical and textural properties crucial for CO2 post-combustion capture and textile dye removal from water, using agricultural waste as carbon precursor to address the environmental and economic challenges associated with the preparation of ACs. Dielectric properties confirmed H3PO4 increased the microwave absorption properties of the biomass. Employing a single-step method, the resulting ACs exhibited large specific surface areas exceeding 1000 m2g−1, achieved in less than 2 min and relatively low energies (2.4 GJ ton-1). Sample 0.4H4 displayed a surface area of 1145 m2g−1 and a significant ultra-micropore (<0.7 nm) content, demonstrating a CO2 uptake of 4.1 and 2.8 mmolg−1 at 0 and 25 °C, with high CO2/N2 selectivity (>38). The sample exhibited rapid CO2 uptake in 5 min and efficient regeneration after 20 adsorption–desorption cycles. Sample 0.3H3 developed large mesoporosity and a high surface area of 1217 m2g−1 with less than 3 min of treatment. The maximum dye removal was 281 mgg−1 and adsorption mechanisms involved diffusion into the mesoporous matrix, electrostatic interactions, H-bonding between AC and MB acid groups, and π–π interactions. The experimental data best fitted the Freundlich model. The results confirmed that microwaves have the potential to convert waste to micro-mesoporous ACs that can be used for a wide range of applications with significant processing time reductions and superior product qualities compared to conventional technologies.

Efficient phosphate removal by Mg-La binary layered double hydroxides: synthesis optimization, adsorption performance, and inner mechanism.

Layered double hydroxides (LDH) hold great promise as phosphate adsorbents; however, the conventional binary LDH exhibits low adsorption rate and adsorption capacity. In this study, Mg and La were chosen as binary metals in the synthesis of Mg-La LDH to enhance phosphate efficient adsorption. Different molar ratios of Mg to La (2:1, 3:1, and 4:1) were investigated to further enhance P adsorption. The best performing Mg-La LDH, with Mg to La ratio is 4:1 (LDH-4), presented a larger adsorption capacity and faster adsorption rate than other Mg-La LDH. The maximum adsorption capacity (87.23 mg/g) and the rapid adsorption rate in the initial 25 min of LDH-4 (70 mg/(g·h)) were at least 1.6 times and 1.8 times higher than the others. The kinetics, isotherms, the effect of initial pH and co-existing anions, and the adsorption-desorption cycle experiment were studied. The batch experiment results proved that the chemisorption progress occurred on the single-layered LDH surface and the optimized LDH exhibited strong anti-interference capability. Furthermore, the structural characteristics and adsorption mechanism were further investigated by SEM, BET, FTIR, XRD, and XPS. The characterization results showed that the different metal ratios could lead to changes in the metal hydroxide layer and the main ions inside. At lower Mg/La ratios, distortion occurred in the hydroxide layer, resulting in lower crystallinity and lower performance. The characterization results also proved that the main mechanisms of phosphate adsorption are electrostatic adsorption, ion exchange, and inner-sphere complexation. The results emphasized that the Mg-La LDH was efficient in phosphate removal and could be successfully used for this purpose.

Magnetically recyclable hydrothermal biochar functionalized with β-CD for simultaneous capturing of cationic methylene blue and auramine O in wastewater

The highly efficient and recoverable magnetic hydrothermal biochar (β-CD@MHBC) was prepared by combining red sandalwood and β-cyclodextrin, and was used for removing methylene blue (MB) and auramine O (AO) dyes in the single and binary systems. The physical and chemical properties of the β-CD@MHBC were characterized using SEM-EDS, BET, XRD, VSM, FT-IR, and XPS techniques. Batch adsorption studies revealed that the obtained maximum adsorption capacities of β-CD@MHBC for MB and AO in the single system were 303.1 and 400.0mgg-1, while in the binary system were 151.1 and 169.1mgg-1 under the optimal conditions of pH 6, 1.0gL-1 dosage, 150mgL-1 dye concentration and adsorption time of 180min, indicating the presence of competitive adsorption with AO possessing stronger affinity in the binary system. The adsorption behaviors of MB and AO could be well described by the Langmuir isotherm model and pseudo-second-order kinetic model in both single and binary systems. The possible adsorption mechanism involved pore filling, electrostatic attraction and hydrogen bonds between β-CD@MHBC and dye molecules. Furthermore, the spent β-CD@MHBC displayed excellent reusability and stability with removal efficiencies of 94% for MB and 83% for AO after five cycles of adsorption-desorption. In summary, the prepared β-CD@MHBC with excellent adsorption property and regeneration performance could have great potential for continuous removal of target pollutants in actual wastewater treatment.

Synthesis of recyclable and light-weight graphene oxide/chitosan/genipin sponges for the adsorption of diclofenac, triclosan, and microplastics

Emerging micropollutants, such as pharmaceuticals and microplastics (MPs), have become a pressing water environmental concern. The aim of this study is to synthesize chitosan sponges using graphene oxide (GO) and genipin (GP) for the removal of pharmaceuticals (diclofenac (DCF) and triclosan (TCS)) and MPs, verify their adsorption mechanisms, evaluate the effects of temperature, pH, and salinity on their adsorption capacities, and determine their reusability. The GO5/CS/GP sponge exhibited a macroporous nature (porosity = 95%, density = 32.6 mg/cm3). GO and cross-linker GP enhanced the adsorption of DCF, TCS, and polystyrene (PS) MPs onto the CS sponges. The adsorption of DCF, TCS, and PS MPs involved multiple steps: surface diffusion and pore diffusion of the sponge. The adsorption isotherms demonstrated that Langmuir model was the most fitted well model to explain adsorption of TCS (qm = 7.08 mg/g) and PS MPs (qm = 7.42 mg/g) on GO5/CS/GP sponge, while Freundlich model suited for DCF adsorption (qm = 48.58 mg/g). DCF adsorption was thermodynamically spontaneous and endothermic; however, the adsorption of TCS and PS MPs was exothermic (283–313 K). The optimal pH was 5.5–7 due to the surface charge of the GO5/CS/GP sponge (pHzpc = 5.76) and ionization of DCF, TCS, and PS MPs. As the salinity increased, DCF removal efficiency drastically decreased due to the weakening of electrostatic interactions; however, TCS removal efficiency remained stable because TCS adsorption was mainly caused by hydrophobic and π–π interactions rather than electrostatic interaction. The removal of PS MPs was enhanced by the electrostatic screening effects of high Na+ ions. PS nanoplastics (average size = 26 nm) were removed by the GO5/CS/GP sponge at a rate of 73.0%, which was better than that of PS MPs (41.5%). In addition, the GO5/CS/GP sponge could be recycled over five adsorption–desorption cycles.

Artemisinin gum reinforced porous amidoxime aerogel with high efficiency adsorption for uranium extraction from seawater

The extraction of uranium resources from the ocean is of great importance in energy exploration. This work reported a polysaccharide composite aerogel to adsorb uranium from the ocean, a facile freeze-drying strategy was explored to create a physically crosslinked artemisia sphaerocephala krasch gum (ASKG)-poly(amidoxime) (PAO) aerogel (ASKG@PAO). Due to the excellent hydrophilicity and swelling properties of artemisia spherecephala krasch gum, the ASKG@PAO can quickly and stably adsorb uranyl ions in the ocean. The batch adsorption test results showed ASKG@PAO (mASKG: mPAO = 1:1) has an excellent uranium removal rate (93.92 %) and a high uranium adsorption capacity (341.11 mg/g). Desorption kinetic experiments showed that the ASKG@PAO can desorb 90 % of the uranyl ions within 10 min and retain a removal rate of 87.3 % after five adsorption–desorption cycles. In addition, ASKG@PAO has excellent selectivity for uranyl ions. Consequently, ASKG@PAO aerogel has significant potential for extracting marine uranium resources.

Separation and purification of polyprenols from Ginkgo biloba leaves by silver ion anchored on imidazole-based ionic liquid functionalized mesoporous MCM-41 sorbent.

Polyprenols (PPs) are compounds with excellent biological activities and are applied in food, pharmaceutical, and cosmetic industries. However, its strong non-polar nature makes it difficult to separate with many saturated impurities (such as saturated fatty acids) extracted together. Complexation extraction is an effective method for separating saturated and polyunsaturated compounds. In this study, mesoporous silica MCM-41 was modified by imidazole-based ionic liquids (IL) followed by coating these MCM-41-supported IL compounds with silver salt to construct π-complexing adsorbent (AgBF4/IL•MCM-41) to enrich PPs from Ginkgo biloba leaves (GBL) extract. The mesoporous π-complexing sorbent was characterized by small-angle X-ray scattering (SAXS), FTIR, and nitrogen adsorption-desorption. The effect of the ratio of silver salt to IL•MCM-41 on the adsorption capacity of polyprenols from GBL was compared, and the dosage of AgBF4 was determined to be 1.5 mmol/g IL•MCM-41. Adsorption isotherms and kinetics indicate that the π-complexing adsorbent has excellent PPs adsorption performance (153 mg/g at 30 °C) and a fast adsorption rate (the time to reach adsorption equilibrium is 210 s). The PPs were separated using the fixed bed after treatment for only one cycle with AgBF4/IL•MCM-41, and the content of PPs in the product was increased from 38.54% to 70.2%, with a recovery rate of 86.6%. The π-complexing adsorbent showed excellent reusability for ≥3 adsorption-desorption cycles.

Decoration of dandelion-like manganese-doped iron oxide microflowers on plasma-treated biochar for alleviation of heavy metal pollution in water

Carbon-based biowaste incorporated with inorganic oxides as a composite is an enticing option to mitigate heavy metal pollution in water resources due to its more economical and efficient performance. With this in mind, we constructed manganese-doped iron oxide microflowers resembling the dandelion-like structure on the surface of cold plasma-treated carbonized rice husk (MnFe2O3/PCRH). The prepared composite exhibited 45% and 19% higher removal rates for Cu2+ and Cd2+, respectively, than the pristine CRH. The MnFe2O3/PCRH composite was characterized using XRD, FTIR, FESEM, EDX, HR-TEM, XPS, BET, TGA, and zeta potential, while the adsorption capacities were investigated as a function of pH, time, and initial concentration in batch trials. As for the kinetics, the pseudo-second-order was the rate-limiting over the pseudo-first-order and Elovich model, demonstrating that the chemisorption process governed the adsorption of Cu2+ and Cd2+. Additionally, the maximum adsorption capacities of the MnFe2O3/PCRH were found to be 122.8 and 102.5 mg/g for Cu2+ and Cd2+, respectively. Based on thorough examinations by FESEM-EDS, FTIR, and XPS, the possible mechanisms for the adsorption can be ascribed to surface complexation by oxygen-containing groups, a dissolution-precipitation of the ions with –OH groups, electrostatic attraction between metal ions and the adsorbent's partially charged surface, coordination of Cu2+ and Cd2+ with π electrons by aromatic/graphitic carbon in the MnFe2O3/PCRH, and pore filling and diffusion. Lastly, the adsorption efficiencies were maintained at about 70% of its initial adsorption even after five adsorption-desorption cycles, displaying its remarkable stability and reusability.

Adsorption of 2,4,6-trinitrotoluene by indole-based porous organic polymer with suitable three-dimensional space size via physisorption and chemisorption

An indole-based porous organic polymer (PTIM) with antibacterial activity was prepared by Friedel-Crafts alkylation and supercritical drying from the self-made tri(1H-indol-3-yl)methane (TIM). The adsorption of 2,4,6-trinitrotoluene (TNT) by PTIM involved physisorption followed by chemisorption, and the mechanism was verified by theoretical simulation and experiment. The physisorption and chemisorption between PTIM and TNT as well as the suitable three-dimensional space size of cross-linked network in PTIM enabled PTIM to have an unprecedented adsorption capacity for TNT (399.2 mg/g). Meanwhile, the removal efficiency of PTIM for TNT was also very high, and it could reach more than 85% of the maximum adsorption capacity after only 1 h of adsorption. Furthermore, the adsorption capacity of PTIM to TNT in actual water samples was slightly less than that in the laboratory, while the adsorption equilibrium time (4 h) was much shorter than the laboratory data (13.75 h). As a result, PTIM could not only achieve primary purification of TNT wastewater from high concentration to low concentration, but also advanced purification from low concentration to standard discharge concentration. In addition, PTIM possessed excellent recycling performance, and the maximum adsorption capacity was still 97% of the initial capacity after five adsorption-desorption cycles Unexpectedly, PTIM also had good antibacterial activity, preventing bacteria from adhering to or covering the pores, and ensuring excellent adsorption capacity and recycling performance. These results showed that PTIM was a promising TNT adsorbent.

A new initiators-free technique for synthesizing stable amine-impregnated polymeric aerogel using electron beam radiation for CO2 capture

New research in reducing CO2 emissions is ongoing to mitigate global warming. New ways are continuously sought to efficiently capture flue gases emitted by industries, one of which is using porous adsorbents like aerogels. The use of chemical initiators is the traditional way of synthesizing aerogels for CO2 capture; however, it pollutes the environment to some extent. This study finds an initiator-free method of synthesizing the aerogel which is faster and more stable yet green. The method involves exposing oil-in-water emulsions containing monomer mixtures along with other chemicals to a radiation dose of 10–50 kGy range using an electron accelerator. The polymeric aerogel was formed within 5 min after exposure to optimum dosage, which was then characterized to evaluate the physio-chemical changes. The test revealed that the aerogel synthesized at 40 kGy EB radiation dose exhibits the maximum PEI loading capacity of 4.1 g/g of aerogel. Furthermore, the CO2 adsorption performance of an optimized amine-impregnated polymeric aerogel was 4.45 mmol/g at 30 °C. Interestingly, this aerogel was able to preserve the initial capacity without significant decrease even after five adsorption-desorption cycles. The proposed method is likely to be of great significance in the field of CO2 capture.

Preparation of formic acid-modified zirconium based metal organic frameworks for toluene absorption

UiO-66 is a widely used metal-organic frameworks in air pollution control. Volatile organic compounds (VOCs) are the important atmosphere pollutants that damage atmospheric environment and people health. UiO-66 was prepared by solvothermal method and modified with formic acid. All the materials were successfully prepared and characterized by XRD, BET, SEM, TG and FTIR, and the adsorption ability of UiO-66 was tested by toluene. The results showed that the BET specific surface area of UiO-66 synthesized by formic acid doping was enhanced, and the adsorption capacity of the doped adsorbent was significantly higher than that of UiO-66, which could reach up to 424.9 mg/g when the doping amount of formic acid was 20 mmol. The addition of acid during the reaction process could inhibit the recrystallization of H2BDC, which was beneficial for the pore structure construction of the material. Meanwhile, the material was subjected to static and dynamic adsorption, as well as adsorption-desorption continuous cycle experiments, which showed that the material has high thermal stability, and the desorption efficiency was 90.8% after five cycle experiments. The addition of formic acid can improve the adsorption performance of the specific surface area of UiO-66.