High Adsorption Rate Research Articles

Biomimetic mineralization synthesis of tricobalt tetraoxide/nitrogen doped carbon skeleton for enhanced capacitive deionization

Developing novel capacitive deionization (CDI) electrode materials with high salt adsorption capacity and adsorption rate is essential for desalination applications, however, encountering significant challenges. Herein, a facile and energy economical biomimetic mineralization method is proposed to construct the tricobalt tetraoxide/nitrogen doped carbon (Co3O4/NC) heterostructure. Benefiting from the mild biomimetic mineralization process, small Co3O4 nanoparticles grow uniformly on interconnected multi-branched NC skeleton. The as-obtained Co3O4/NC heterostructure exhibits a salt adsorption capacity of 44.5 mg g−1, adsorption rate of 7.9 mg g−1 min−1, and 91.3 % of capacity retention after 60 cycles at 1.2 V in 500 mg L−1 salt solution. These performances overwhelm the bare Co3O4 (24.6 mg g−1, 3.5 mg g−1 min−1, 65.7 %), indicating superior desalination performances of the Co3O4/NC heterostructure. This study gives an insight into the biomimetic mineralization method and provides one promising candidate of CDI electrode.

Prebiotic stachyose inhibits PRDX5 activity and castration-resistant prostate cancer development

Stachyose (STA) is a prebiotic with poor oral bioavailability. In this study, we developed stachyose caproate (C6-STA), as a novel STA derivative, to demonstrate its high adsorption rate via oral administration. Pharmacokinetic analysis reveals that after absorption, the STA derived from C6-STA reaches its highest peak in the blood, liver, and kidney at 20 min, 30 min, and 12–24 h, with approximate levels of 1200 μg/mL, 0.14 μg/mL, and 0.2–0.3 μg/mL, respectively. In addition, the accumulation of STA in prostate tissues of mice with castration-resistant prostate cancer (CRPC) (1.75 μg/mg) is 10-fold higher than that in normal prostate tissues (0.14 μg/mg). The analysis also reveals that C6-STA has t1/2 of 12.8 h and Tmax of 0.25 h, indicating that it has the potential to be used as a promising drug in clinical practice. The toxicological evaluation shows no obvious side effects of C6-STA in mice administered with a 0.2 g/kg intragastric dose. Pharmacodynamic analysis and mechanism investigation of C6-STA show its ability to inhibit peroxiredoxin 5 (PRDX5) enzyme activity, disrupt PRDX5-nuclear factor erythroid 2-related factor 2 (NRF2) interaction, and decrease NAD(P)H quinone dehydrogenase 1 (NQO1) levels. NQO1 decrease further causes the accumulation of quinone radicals, which ultimately leads to the apoptosis of LNCaP cell-derived drug-tolerant persister (DTP) cells and slows CRPC progression. Our study discovered the anti-tumor activity of stachyose and shows that prebiotics have biological functions in vivo besides in the gut. Further investigation of C6-STA, especially in CRPC patients, is warranted.

Electron-rich COFs with a bis-triphenylamine structure as the main chain: Ultrafast and ultrahigh iodine capture

The construction of ideal adsorbents for the capture of radioiodine usually requires high adsorption capacity and high adsorption rate. However, this is still a challenging problem. The advantages of COFs based on their good crystallinity, pore order, and structural diversity make COFs ideal adsorbents. Here, we developed three novel electron-rich COFs based on the triphenylamine, which have good chemical, thermal, and radiation-resistant stability and are suitable for the harsh environment of radioactive iodine therapy. Upon the introduction of heteroatom N/S, TAPD-PDB and TAPD-TDB exhibited amazing adsorption capacities (75 °C: 7.88 g g−1 and 6.98 g g−1, 25 °C: 4.46 g g−1 and 3.62 g g−1), while the adsorption rates, K80%, are significantly increased to 5.34 g g−1h−1 and 4.22 g g−1h−1, which is higher than most of the reported iodine adsorbents. It was surprising that COFs also have excellent adsorption properties for iodine in cyclohexane solution up to 1260 mg L−1. FT-IR, XPS, Raman and electrostatic potential calculations indicate that the ultrafast and ultrahigh iodine uptake of COFs can be attributed to the interplay of their rich electronic structure, efficient adsorption sites, helical conformation and charge transfer. This study shows the efficient and ultrafast removal of iodine from nuclear wastewater and nuclear exhaust gas by electron-rich COFs.

Surface functionalization of oil palm empty fruit bunch (OPEFB)-derived cellulose as a carboxyl platform for metal cations and dyes removal from aquatic media

The abundant oil palm empty fruit bunch (OPEFB) as by-product of palm oil milling processes exhibits a potential as an alternative cellulose feedstock for bio-adsorbent. This study aimed to produce a highly carboxylated bio-adsorbent for direct industrial application from OPEFB-based cellulose via mercerization and followed by esterification with succinic anhydride (SA) to enhance its adsorptive capability towards hazardous heavy metal and dyes ions. The modification using SA provides the carbon backbone platform for carboxyl group attachment for the contaminants. The results showed that the carboxylated cellulose had a high carboxyl content (4.39 mmol/g). Carboxylated cellulose had a higher binding capacity for adsorbates, with removal rates of 94.7%, 97.85%, 40.9%, and 90.15% for dye, Pb2+, Cu2+, and Cd2+ cations, respectively, at pH 6, 4 hours reaction time, and at room temperature. In comparison, unmodified cellulose removed only 47%, 23.1%, 2.9%, and 7.5% for dye, Pb2+, Cu2+, and Cd2+ cations, respectively. The adsorption kinetics study revealed that the adsorption process followed the pseudo-second-order model. The adsorption isotherm of these two metal cations follows the model of Langmuir very well, while Cu2+ follows the Freundlich model. Our method produces bio-adsorbents with high carboxyl content and adsorption rate in a short reaction time using OPEFB as a green precursor material that is easily scalable for industrial use.

Fabrication of magnetic ferroferric oxide-based composite for efficiently removing and recycling ciprofloxacin

The extensive use of antibiotics and recklessly discarding have caused serious water pollution. Its controlling and remedying become an urgent problem. With the goal of removing ciprofloxacin hydrochloride (HCIP), a magnetic adsorbent of Fe3O4@Mg(OH)2 was prepared via a facile approach in this work. The structure and morphology were systematically characterized by XRD, SEM, FT-IR and XPS. It is found hexagonal Mg(OH)2 flakes are evenly coating on the surface of Fe3O4. This structured morphology offers Fe3O4@Mg(OH)2 high specify surface area. The composite shows excellent removal performance. It achieves almost 99 % HCIP elimination within 1.5 h. The influence of the dosage of adsorbents, pH and interfering ions and reusability were fully studied. It is shown that the composite can be used in neutral condition and has long serve life. The cost effective synthesis, simple operation, high adsorption rate and long serve life make Fe3O4@Mg(OH)2 wide application for water treatment in a large scale.

Constructing 2D Polyphenols-Based Crosslinked Networks for Ultrafast and Selective Uranium Extraction from Seawater.

The role of tannins (TA), a well-known abundant and ecologically friendly chelating ligand, in metal capture has long been studied. Different kinds of TA-containing adsorbents are synthesized for uranium capture, while most adsorbents suffer from unfavorable adsorption kinetics. Herein, the design and preparation of a TA-containing 2D crosslinked network adsorbent (TANP) is reported. The ≈1.8-nanometer-thick TANP films curl up into micrometer-scale pores, which contribute to fast mass transfer and full exposure of active sites. The coordination environment of uranyl (UO2 2+) ions is explored by integrated analysis of U L3-edge XANES and EXAFS. Density functional theory calculations indicate the energetically favorable UO2 2+ binding. Consequently, TANP with excellent adsorption kinetics presents a high uranium capture capacity (14.62mg-Ug-Ads-1) and a high adsorption rate (0.97mgg-1day-1) together with excellent selectivity and biofouling resistance. Life cycle assessment and cost analysis demonstrate that TANP has tremendous potential for application in industrial-scale uranium extraction from seawater.

A Review of Life Cycle Assessment of Nanomaterials-Based Adsorbent for Environmental Remediation

<p>Nanomaterials, known for their exceptional physicochemical properties, are used in electronics, skincare, catalysts, agriculture, and water treatment. Their small size and large surface area enable high adsorption capacities and rapid adsorption rates, effectively removing organic and inorganic pollutants from water. Designed as composites, nanomaterials enhance adsorption capacity, improve mechanical strength, and provide support matrices for retaining nanoparticles. Nanoadsorbents are particularly effective in removing toxic metals from wastewater and drinking water, targeting low concentrations of metals like arsenic, cadmium, lead, and mercury, crucial given stringent discharge regulations. However, the widespread use of nanomaterials poses potential health and environmental risks, as their production involves significant energy and material inputs, generating pollutants. Most research focuses on functionalities without considering life cycle environmental impacts. Life cycle assessment (LCA) is a comprehensive tool for evaluating these impacts, assessing products from cradle to grave, including raw material extraction, processing, manufacturing, distribution, use, maintenance, and disposal or recycling. LCA, based on the ISO 14040 series, includes four phases: goal and scope definition, life cycle inventory, life cycle impact assessment, and life cycle interpretation. This study categorizes existing research based on the four LCA phases, aiming to highlight current practices, challenges, and progress. The findings provide insights and recommendations for future research to ensure the sustainable development of nanomaterials.</p>

The molecular binding sequence transformation of soil organic matter and biochar dissolved black carbon antagonizes the transport of 2,4,6-trichlorophenol

Dissolved organic matter (DOM) and dissolved black carbon (DBC) are significant environmental factors that influence the transport of organic pollutants. However, the mechanisms by which their molecular diversity affects pollutant transport remain unclear. This study elucidates the molecular binding sequence and adsorption sites through which DOM/DBC compounds antagonize the transport of 2,4,6-trichlorophenol (TCP) using column experiments and modelling. DBC exhibits a high TCP adsorption rate (kn = 5.32 × 10−22 mol1–n∙Ln–1∙min−1) and conditional stability constant (logK = 5.19–5.74), indicating a strong binding affinity and antagonistic effect on TCP. This is attributed to the high relative content of lipid/protein compounds in DBC (25.65 % and 30.28 %, respectively). Moreover, the small molecule lipid compounds showed stronger TCP adsorption energy (Ead = −0.0071 eV/−0.0093 eV) in DOM/DBC, combined with two-dimensional correlation spectroscopy model found that DOM/DBC antagonized TCP transport in the environment through binding sequences that transformed from lipid/protein small molecule compounds to lignin/tannin compounds. This study used a multifaceted approach to comprehensively assess the impact of DOM/DBC on TCP transport. It reveals that the molecular diversity of DOM/DBC is a critical factor affecting pollutant transport, providing important insights into the environmental trend and ecological effects of pollutants.

Engineering shrinkage resistance of nano-structured hydrogels in seawater for fast uranium capture

Synthetic hydrogels, which are 3D networks composed of crosslinked hydrophilic polymer chains, have been created using various crosslinked ways for uranium capture due to full exposure of chelate functional groups. However, the conventional honeycomb-like hydrogels exhibit non-connected micropore structure, which locks abundant water molecules and hence is unfavorable for mass transfer. Herein, we demonstrate a simple synthesis of the nano-structured hydrogel with activated nanogels as nano-crosslinkers (denoted as PGP hydrogel), and probe into the relationship between hydrogel structural parameters and uranium adsorption kinetics. It is found that the PGP hydrogel with a low crosslinking density of ∼0.02 mol/m3 possesses interconnected micropores, thereby facilitating diffusion of uranyl ions (UO22+) in 3D polymeric networks. Furthermore, a freeze-assisted soaking strategy is proposed to endow PGP hydrogel (denoted as target hydrogel) with strong shrinkage resistance in natural seawater, resulting in a ∼40 % increase in water permeance to reach 369 Lm−2h−1MPa−1. Correspondingly, the adsorption equilibrium time is shortened to ∼11 days. Although the uranium uptake capacity of PGP hydrogels with and without freeze-assisted soaking treatment remain basically unchanged (∼9.73 mg-U/g-Ads), a high uranium adsorption rate of 0.88 mg/g/d for the target hydrogel surpasses most currently available polymer adsorbents. The presented strategy is generalizable to a broader range of applications involving the adsorption of economically valuable ions in seawater or brine lake.

Fast and facile sonochemical fabrication of covalent organic frameworks in water for the adsorption of flavonoids: Adsorption behaviors and mechanisms

Solvothermal synthesis of covalent organic frameworks (COFs) typically requires high temperatures exceeding 120 °C, large amounts of toxic organic reagents, and reaction durations spanning 3–7 days. In contrast, a new COF (TFPPy-AD) was rapidly synthesized by the sonochemical method at room temperature within just 60 min, eliminating the need for toxic reagents. The characterization of the material showed that TFPPy-AD was successfully synthesized with notable features such as a large pore size, high crystallinity, and good thermal stability. Subsequent adsorption experiments highlighted the material's exceptional adsorption capacity and selectivity for flavonoids. The adsorption mechanism of flavonoids onto TFPPy-AD likely involves a combination of sieve interactions, hydrogen bonding interactions, hydrophobic interactions, and π-π interactions. This sonochemically synthesized COF exhibits promising attributes including high adsorption capacity, selectivity, and rapid adsorption rate for flavonoids, suggesting potential applications in the separation and purification of flavonoids in natural medicines.

Wood-structured carbon with reassembled pores showing high propylene adsorption rate for efficient separation of propylene/propane

Efficient separation of propylene/propane requires enhancing adsorption rates on adsorbents, while maintaining high adsorption capacity and selectivity, heavily relying on engineering pore structures within the adsorbents. Herein, we have prepared wood-structured carbon with reassembled pores by using wood frameworks incorporated with CuCl2 and a polymer coating. Upon carbonization, the wood framework transforms into microporous carbon, while the polymer coating converts into molecular sieving carbon. Notably, the evaporation of CuCl produced from the in-situ reduction of CuCl2 creates additional micropores in the molecular sieving carbon layer. This wood-structured carbon adsorbent exhibits a propylene diffusion constant of 0.011 min−1 at 0.5 bar, which is 4.1-fold higher than the sample without CuCl2. Additionally, this adsorbent shows a high propylene uptake of 2.38 mmol g−1 and a propylene/propane dynamic selectivity of up to 161 at 298 K and 1 bar. Aspen simulation suggests that a propylene purity of 99.9 % can be achieved with a 70 % recovery using a vacuum swing adsorption process. The enhanced performance is primarily attributed to the unique pore structures of the wood-structured carbon adsorbent.

Fabrication of single-ion conductive quasi-solid-state electrolyte membrane for high-performance lithium-ion batteries

The aim of this work is to develop new quasi-solid-state electrolyte materials for lithium-ion batteries (LIBs) to improve their safety and comprehensive electrochemical performance. Herein, helical mesoporous silica nanofibers were synthesized by a sol–gel method. After grafting lithium salt onto their surfaces, a single-ion conductor (SL) was obtained. Then, using poly(vinylidene fluoride-co-hexafluoropropylene) as the polymer matrix, SL as the filler, a porous composite film was prepared by solution casting method. After soaking organic electrolyte with low concentration Li salt till saturation, one quasi-solid-state electrolyte membrane (PSLE) was achieved. It showed high electrolyte adsorption rate of 660 % and good thermal stability. A high lithium-ion transfer number of 0.85 indicated typical single-ion conductivity. Moreover, a high electrochemical stability window of up to 5.5 V and an ionic conductivity of 2.5 × 10−3 S·cm−1 at 25 °C were gained. The assembled LFP|PSLE|Li battery exhibited excellent rate performance and cycle stability, indicating that the PSLE has great application prospect in solid-state LIBs.

Eco-friendly synthesis and application of NH2-COOH functionalized Fe3O4@graphite carbon microballs in heavy metal removal

Heavy metal pollution in wastewater is quite challenging for the environment. This study pioneers the synthesis of a novel adsorbent, amine-acid functionalized Fe3O4 decorated carbon micro-balls (NH2-COOH/Fe3O4@CMBs) via hydrothermal process and controlled thermal treatment under nitrogen atmosphere, utilizing eco-friendly resource glucose as a carbon precursor. The formation of cubic Fe3O4 nanoparticles and crystalline graphite within a carbon core-shell structure is confirmed. NH2-COOH/Fe3O4@CMBs show a porosity conducive to ion exchange in the range of 100–300 nm via FE-SEM, exhibiting a significant surface area of 494 m²/g with optimal pore volume. Within the carbon matrix, H2-TPR affirms the robust integration of Fe3O4, essential for high adsorption rates. In practical applications, NH2-COOH/Fe3O4@CMBs demonstrate exceptional performance, removing ∼ 99 % of Pb2+ ions in 30 min., showcasing an impressive adsorption capacity of 360 mg/g. The rapid and potent adsorption is attributed to the electron-rich graphite layers and the presence of abundant chelating sites. This research introduces NH2-COOH/Fe3O4@CMBs as a commercially viable and environmentally responsible solution for the removal of hazardous heavy metals from wastewater. Scientific understanding of adsorptive material not only advances but also offers a tangible approach to mitigate a pressing public health concern, marking a significant stride towards sustainable water treatment technologies.

Facile preparation of hydrophobic PPy@Si/PU foam for efficient oil adsorption by photothermal effects

AbstractExploring new oil absorbing materials with high adsorption rate remains a global challenge. Hydrophobic porous materials with photothermal conversion property are an attractive option to address oil spills. Herein, the organosilicon (hydroxyl‐terminal polydimethylsiloxane) was used to modify polyurethane (PU) foam to endow it good hydrophobic and compressible properties. Meanwhile, polypyrrole (PPy) with photothermal effect was introduced to endow PU foam with excellent photothermal properties. The PPy@Si/PU composite foams can reach 77.1 and 49.6°C under the laser and simulated sunlight (with the intensity of 1 kW/m2), respectively. The raised temperature of PPy@Si/PU foam makes it adaptable to reduce the crude oil's viscosity and improve its oil adsorption rate. The maximum oil adsorption rate of PPy@Si/PU foam can obtain 175% and 145% under the laser and simulated sunlight, respectively. Therefore, the PPy@Si/PU foam possesses effective photic‐driving oil adsorption capacity, which has a good prospect to be an efficient oil spills treatment material.

Selective isolation of rubidium with mesoporous silica loaded with ammonium phosphomolybdate via an in-pore crystallization reaction

The scarcity of rubidium (Rb) in ore form makes it a valuable metal, prompting the need to develop reusable adsorbent materials for effective separation of rubidium (Rb+) from salt lake brine, which holds significant importance. Herein, a novel Rb+ selective composite adsorbent was prepared by in-pore crystallization. Macromesoporous silica was prepared using polyoxyethylene (10) octadecyl ether (Brij S10) as a templating agent and the effect of different templating agents on the pore size was investigated. An AMP-SiO2 composite adsorbent for Rb+ was obtained by “growing” ammonium phosphomolybdate on the macro-mesoporous silica by in-pore crystallization reaction. The results indicated that the adsorption of Rb+ by the AMP-SO2 adsorbent adhered to monolayer chemisorption, which was verified by fitting the adsorption data using the pseudo-second-order kinetics and the Langmuir isotherm model, respectively. The loading of AMP was 29.4 %, which increased the adsorption capacity by 115 %. Furthermore, the adsorption rate of Rb+ on AMP-SO2 when interfering ions were present still reached 73.2 % (KCl), 76.4 % (CaCl2), and 86.6 % (MgCl2). Density functional theory simulation indicated that AMP-SiO2 exhibited a higher adsorption energy for Rb+ (−9.79 eV) than K+, Li+, Ca2+, and Mg2+. The Rb 3d and Mo 3d X-ray photoelectron spectra of AMP-SiO2 before and after adsorption of Rb+, indicated that the ion-exchange process between rubidium and lattice cations is the controlling mechanism. In addition, AMP-SiO2 also showed good regeneration performance and maintained a high adsorption rate after five adsorption-resolution experiments. In summary, the AMP-SiO2 composite adsorbent can effectively expose adsorption sites and improve mass transfer efficiency, and has significant potential for future application in rubidium separation and extraction.

A Multifunctional Magnetic Fluorescent Nanoprobe for Copper(II) Using ZnS-DL-Mercaptosuccinic Acid-Modified Fe3O4 Nanocomposites

Cu2+ has increasingly become a great threat to the natural environment and human health due to its abundant content and wide application in various industries. DL-Mercaptosuccinic acid and ZnS-modified Fe3O4 nanocomposites were designed, synthesized, and applied in the determination of Cu2+. The prepared nanocomposites were characterized by scanning electron microscopy (SEM), transmission electron microscopes (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), and thermogravimetric analyzer (TG). The magnetic fluorescent nanoprobe exhibited highly selective and sensitive fluorescence-quenching characteristics with Cu2+ ions. The fluorescence detection linear range was 0–400 μM, with the detection limit being 0.489 μM. In addition, the magnetic fluorescent nanoprobe exhibited a high adsorption and removal rate for Cu2+. It had been successfully applied to detect Cu2+ in real water samples with a satisfactory recovery rate. The magnetic fluorescent nanoprobe could simultaneously realize the functions of enrichment, quantitative detection, and separation, reduce the pollution of copper ions and probes, and establish an environment-friendly detection method. Consequently, the magnetic fluorescent nanoprobe offered a new pathway for the removal and detection of not only Cu2+ but also other heavy metal ions in water.

Simultaneously enhancing toluene adsorption and regeneration process by hierarchical pore in activated coke: a combined experimental and adsorption kinetic modeling study.

Activated coke is a type of commonly used adsorbent for benzene series VOCs such as toluene, but traditional microporous activated coke usually faces the challenge of poor regeneration performance. Herein, based on self-made activated cokes with typical pore configuration, we found that adsorption and regeneration of toluene can be simultaneously enhanced by constructing hierarchical pore in activated coke. Correlations of pore configuration with toluene adsorption capacity and regeneration efficiency reveal that micropore contributes for strong toluene adsorption; meso-macropore provides mass transfer channel for toluene desorption and regeneration process. Hierarchical porous activated coke prepared from Zhundong subbituminous coal not only achieves the highest toluene adsorption capacity of 340.92mg·g-1, but also can retain more than 90% of initial adsorption capacity after five adsorption-regeneration cycles. By contrast, micropore-dominant activated cokes can only retain 70% of initial adsorption capacity. Adsorption kinetic modelling on adsorption breakthrough curves shows that hierarchical porous activated coke prepared from Zhundong subbituminous coal exhibits high adsorption and diffusion rate constants of 14.39 and 33.45min-1, respectively, much higher than those of micropore-dominant activated cokes. Due to the accelerated surface adsorption and diffusion processes induced by meso-macropore, toluene adsorption and regeneration behavior can be simultaneously improved. Results from this work validated the role of pore hierarchy in toluene adsorption-regeneration process, providing guidance for designing high-performance activated coke with synergistically improved toluene adsorption capacity and regeneration performance.

Sulfonated Azocalix[4]arene-Modified Metal-Organic Framework Nanosheets for Doxorubicin Removal from Serum.

Chemotherapy is one of the most commonly used methods for treating cancer, but its side effects severely limit its application and impair treatment effectiveness. Removing off-target chemotherapy drugs from the serum promptly through adsorption is the most direct approach to minimize their side effects. In this study, we synthesized a series of adsorption materials to remove the chemotherapy drug doxorubicin by modifying MOF nanosheets with sulfonated azocalix[4]arenes. The strong affinity of sulfonated azocalix[4]arenes for doxorubicin results in high adsorption strength (Langmuir adsorption constant = 2.45-5.73 L mg-1) and more complete removal of the drug. The extensive external surface area of the 2D nanosheets facilitates the exposure of a large number of accessible adsorption sites, which capture DOX molecules without internal diffusion, leading to a high adsorption rate (pseudo-second-order rate constant = 0.0058-0.0065 g mg-1 min-1). These adsorbents perform effectively in physiological environments and exhibit low cytotoxicity and good hemocompatibility. These features make them suitable for removing doxorubicin from serum during "drug capture" procedures. The optimal adsorbent can remove 91% of the clinical concentration of doxorubicin within 5 min.

Preparation and ammonium adsorption behavior of interpenetrating polymer networks hydrogel of chitosan‐g‐poly(acrylic acid)/bentonite and chitosan‐glutaraldehyde

AbstractIn this article, new interpenetrating polymer network (IPN) hydrogel as an efficient adsorbent for ammonium was prepared by a two‐step process. First, semi‐IPN hydrogel of chitosan‐g‐poly(acrylic acid)/bentonite (CAB) and chitosan (CTS) was synthesized by grafting polymerization in the presence of exfoliated bentonite as both cross‐linking agent and nanoscale inorganic filler. Second, cross‐linking polymer network of chitosan‐glutaraldehyde (CGA) was formed by reaction of CTS with glutaraldehyde (GA). The obtained IPN hydrogel (CAB/CGA) was characterized by Fourier‐transform infrared spectroscopy, scanning electron microscopy and its swelling degree and PZC value were also measured. These results demonstrate that copolymerized graft reaction was occurred between CTS, AA and bentonite forming CAB, and CGA presented as a cross‐linker in CAB/CGA polymer network. CAB/CGA has a moderate swelling degree of 7.8. CAB/CGA exhibits high adsorption capacity and fast adsorption rate for ammonium. Adsorption process reaches equilibrium in 30 min and fits well to Langmuir adsorption model with a fairly high maximum adsorption capacity of 41.06 mg g−1. The material has a good regeneration ability. After five times of adsorption–desorption, there was almost no decrease in ammonium adsorption capacity. Moreover, the low swelling degree leads to an improvement in material strength and a reduction of equipment cost.

Tuning physicomechanical properties of PEG-interpenetrated anionically modified semi-IPN cryogels functionalized with carboxylate groups

Anionically modified interpenetrated polymer network (semi-IPN) cryogels containing linear polyethylene glycol chains (PEG) were prepared via in situ synthesis and directed assembly of the negatively charged copolymer poly(acrylamide-co-sodium acrylate) (PAN) network template. The influence of reaction conditions; the concentration of linear PEG chains, and polymerization temperature on the elasticity and swelling of these IPNs was analyzed in detail. The interpenetrating structure of PEG chains and PAN host network have been confirmed by FTIR, TGA and XRD analysis. The equilibrium water content, oscillatory swelling/deswelling kinetics, and water transport mechanism were analyzed as a function of PEG content. The results showed that semi-IPN gels exhibited different swelling behavior as the reaction conditions varied. Addition of 13.9% (w/v) PEG resulted in a 25-fold increase in the swelling ratio of semi-IPN hydrogels. By performing compression tests on semi-IPN gels to determine the change of compression properties, the effective cross-linking density of semi-IPN PAN/PEG was expressed as a second-order polynomial depending on the amount of PEG. The swollen modulus of semi-IPN cryogels was much higher than that of semi-IPN hydrogels for all PEG concentrations. Semi-IPNs showed reversible on-off switching with remarkable sensitivity to external pH stimulus. Structural parameters, degree of swelling, volume fraction of cross-linked polymer in the swollen state, and diffusion coefficients due to pH-induced swelling of semi-IPN gels were determined. The presence of linear PEG chains in the structure promoted swelling by both increasing the swelling rate and significantly reducing the time required to reach the equilibrium-state. The swelling process was Fickian diffusion, and the diffusion coefficients for swelling of PEG-interpenetrated semi-IPNs increased with PEG content. The effectiveness of removing methylene blue (MB) dye from aqueous solutions by semi-IPNs was evaluated. Batch adsorption experiments were performed as a function of the gelation temperature, amount of PEG, contact time, and initial dye concentration. The adsorption isotherm and kinetics were described well by Langmuir isotherm model and pseudo-second-order model, respectively. Adsorption of MB was a multi-step process involving surface adsorption followed by intra-particle diffusion. Semi-IPN PAN/PEG cryogels prepared under cryocondition with high adsorption capacities and fast adsorption rates have been developed as new adsorbents effective in removing dyes and other toxic substances with higher mechanical strength in water and wastewater treatment.