Epoxy-functionalized polyethyleneimine modified epichlorohydrin-cross-linked cellulose aerogel as adsorbents for carbon dioxide capture

Cellulose-keratin polymer based on "thiol-ene" click reaction and ease-to-process performance

In this work, we provided a new method for preparing cellulose-keratin (CK) polymer by "thiol-ene" click reaction. Firstly, the allyl cellulose (AC) was prepared in alkali/urea system, and then CC double bond of AC was reacted with -SH of keratin (Ker) to produce CK polymer under UV irradiation. FTIR, XRD, XPS, and NMR provided the evidences for producing AC and CK, and the integrity of the keratin polypeptide chain could be preserved. CK polymer showed ease-to-process performance, and the composite film formed by casting showed the characteristics of high transmittance, dense cross-section morphology, and easy to twist, bend, and fold. The breaking strength and elongation at break of CK film could reach 44.93 MPa and 22 %, respectively, which exceeded that of the cellulose-protein polymer films obtained by cross-linking with epichlorohydrin in our previous work. The breaking strength and elongation at break of CK fiber formed by wet-spinning could reach 28.8 MPa and 15 %, respectively, which exceeded that of cellulose/keratin composite fiber formed by the co-solvent ionic liquid. Interestingly, the CK fiber exhibited excellent moisture absorption and could be equipped with other functions such as fluorescence, thermochromic, and flame retardancy, which is conducive to improving the wearing comfort of functional fibers.

High-efficiency mass-transfer Marangoni cellulose hydrogel reactor for the degradation of pollutants

Noble metal nanoparticles have been widely used in catalysis, environmental studies, and other fields. However, the loading of noble metals is challenging because of their unfavorable mass transfer. Herein, a simple, green dual-template method was developed for the synthesis of a Marangoni cellulose hydrogel rotor catalytic reactor (MCR). The rotor had a two-component asymmetrical network structure, which was constructed via different crosslinking methods and enabled the MCR to achieve a fast (6190 r/h) and prolonged (25 min) rotation. In addition, we propose a new refueling method, which only requires 80uL solvent to continue to drive the rotor for over 13 min, effectively prolonging the rotation time of the rotor. During rotation, the speed of the catalyst was greater than that of the substrate, which is conducive for the entry of the substrate into the reactor channel. The spin-induced fluid disturbance promoted substrate replenishment around the catalyst, thereby improving the mass-transfer efficiency and increasing the primary kinetic constant to 16.5-fold of that of the stationary hydrogel while maintaining stability. Therefore, the MCR proposed in this study offers a novel approach for improving the catalytic mass-transfer efficiency of precious metals and exhibits potential application value in remediating environmental pollution and catalysis.

Cellulose/covalent organic framework aerogel for efficient removal of Cr(VI): Performance and mechanism study

Cellulose composites have exceptional qualities, particularly in removing heavy metal ions. Nevertheless, these materials' poor mechanical qualities and the restricted exposure of surface-active sites reduce the effectiveness of their removal. The removal efficiency of adsorbent materials largely depends on their macroscopic structural characteristics. This study successfully developed a novel cellulose composite aerogel adsorbent (TBPM). TBPM aerogel possesses not only numerous active sites but also excellent mechanical strength. It is particularly suitable for the efficient removal of hexavalent chromium (Cr(VI))-containing wastewater. The aerogel exhibited a low density of 0.0238 g/cm3 and high porosity of 98.51 %. Incorporating the covalent organic framework (BT-Dg) increased the active sites in the composite aerogel, enhancing its adsorption performance. Compared with other common heavy metal ion adsorbents, the TBPM aerogel demonstrated superior removal performance, with a maximum adsorption capacity of 411.12 mg/g and a removal efficiency of 95.01 % in Cr(VI) solution at 15 °C, pH = 3. The adsorption of Cr(VI) followed pseudo-second-order kinetics and the Langmuir isotherm model. Even after seven adsorption-desorption cycles, TBPM aerogel maintained over 80 % removal efficiency. In addition, the TBPM aerogel successfully filtered 3439 mL of Cr(VI)-containing wastewater. This composite aerogel expands the application of cellulose composites in purifying wastewater.

Polyethylene Polyamine-Modified Chitosan Aerogels: Enhanced CO2 Adsorbents with Lamellar Porous Structures

Due to the continuous growth of global carbon dioxide emissions, the development of cost-effective carbon dioxide capture technology has attracted extensive attention. Amino-modified chitosan aerogels with lamellar porous structures are good candidates as carbon dioxide adsorbents because of their degradable properties and low energy consumption. Polyethylene polyamine-modified chitosan aerogels (PEPA-CSs) were prepared through a process of crosslinking and freeze-drying using a chitosan solution, polyethylene polyamine (PEPA), and epichlorohydrin (ECH) as raw materials. The amino group of PEPA was proven to be successfully grafted on the chitosan surface by FITR and XPS. The SEM and TEM analysis showed a rich three-dimensional porous structure and a good rigidity and bearing capacity of the PEPA-CS. The adsorption capacity was significantly increased by PEPA grafting with a maximum value of 1.59 mmol/g at 25 °C and 1 bar through both physical and chemical interactions, which indicates a potential for broad application prospects in industrial CO2-capture applications.

Pore-Controllable Synthesis of Phthalic Acid-Derived Hierarchical Activated Carbon for Dilute CO2 Capture

Carbon capture and storage (CCS) from dilute sources is an important strategy for stabilizing the concentration of atmospheric carbon dioxide and global temperature. However, the adsorption process is extremely challenging due to the sluggish diffusion rate of dilute CO2. Herein, p-phthalic acid (PTA)-derived hierarchical porous activated carbon (PTA-C) with abundant micro- and mesopores was successfully prepared for dilute CO2 (2 vol %) capture at ambient conditions. The optimal PTA-C sample exhibits an improved BET surface area and total pore volume of 1012.527 m2/g and 2.257 cm3/g, respectively, which endowed a dilute CO2 (2 vol %) adsorptive capacity of 0.89 mmol/g at 25 °C and atmospheric pressure. The dilute CO2 adsorptive capacity is increased to 2.71 mmol/g under the same conditions on amine-modified PTA-C (PTA-NC), which is much higher than that of amine-modified commercial coconut husk AC. In addition, the crude p-phthalic acid as feedstocks for production of PTA-C is widely available from polyester fabrics, which makes these PTA-C cost-effective for large-scale CCS from dilute CO2 sources in industry.

Highly stable 3D cellulose micro-rolls support TiO2 for efficient photocatalysis degradation experiment under weak light conditions

Immobilization of nanometer-scale photocatalysts on a 3D polymeric substrate could play several complementary roles in photocatalysis, such as providing mechanical stability, facilitating easy recycling after usage, enhancing adsorption capability, and improving light harvesting properties through multiple reflections. To achieve stable and efficient photocatalysis under weak light conditions, 3D cellulose micro-rolls were introduced into the photocatalytic composites. Here, the formation of micro-rolls is attributed to the presence of titania nanoparticles, which generate uneven shrinkage stress in cellulose during the freeze-drying process, thereby inducing the cellulose to curl up. The dramatic structural transformation of the 3D micro-rolls increased the Brunauer-Emmett-Teller (BET) surface area of the sample. The 3D micro-roll structure is more favorable for photocatalysis due to its efficient mass transfer and exposed reactive sites, laying the foundation for enhanced adsorption capacity and photocatalytic reactions. The adsorption experiments suggested that the inner space of the micro-rolls provides a sufficient reaction zone, enabling fast mass transfer of molecules and easy access to the active sites. The samples could stand a high strain of 80 % and retain 96 % of the original maximum stress after 200 cyclic compressions, indicating excellent long-term stability. In addition, the photocatalytic tests show that with the help of micro-rolls, TiO2 can convert and utilize weak light that would otherwise be unused, and the catalysate exhibits almost no toxicity towards Escherichia coli.

Enhanced hydrophilicity and antibacterial efficacy of in-situ silver nanoparticles decorated Ti3C2Tx/Polylactic acid composite membrane for real hospital wastewater purification

This study investigates the integration of Ti3C2Tx (MX) and Ag/Ti3C2Tx (Ag/MX) nanocomposites into polylactic acid membranes to enhance hydrophilicity and impart antibacterial properties, targeting hospital wastewater treatment. MX and silver nanoparticles are known for their hydrophilicity and antimicrobial capabilities, were synthesized and incorporated into PLA; a green polymer. The impact of nanocomposite concentration on the membrane's chemical structure, morphology, and overall performance were characterized using various PLA membrane properties and to evaluate the nanocomposite's performance in enhancing pure water flux and antibacterial efficacy. The pure water permeability increased from 1512 L m-2 h-1 bar-1 to 3108 L m-2 h-1 bar-1 in PLA/AgMX4 compared to PLA. Furthermore, a total bacteria count (TBC) rejection of up to 97 % was obtained using the PLA/AgMX4 membrane. The results demonstrated significant improvements in PLA/AgMX membranes compared to pristine PLA, showing a large potential for hospital wastewater treatment.

Sustainable chloramine-functionalized iron hydroxide nanofiber membrane for arsenic(Ⅲ) removal via oxidation-adsorption mechanism

Arsenic-contaminated groundwater is an intractable environmental problem worldwide, particularly As(III), which is not only highly toxic but also resistant to removal. In this study, sustainable chloramine-functionalized iron hydroxide cellulose nanofibrous membrane (Fe-CNFM-Cl) was prepared by electrostatic spinning followed by chemical grafting for As(III) decontamination. In situ engineered iron hydroxides were uniformly dispersed in cellulose nanofibers for As adsorption. The oxidative chlorine (+1) in the grafted chloramine could oxidize As(III) to readily removable As(V). Benefiting from oxidation-enhanced adsorption, Fe-CNFM-Cl was able to remove As(III) reliably. Using Fe-CNFM-Cl, As(III) levels were purified from 1418.73 μg L-1 to meet drinking water standards within 300 min. Additionally, Fe-CNFM-Cl exhibited high iron utilization with a normalized As adsorption capacity of 214.55 ± 15.52 mg g-iron-1. Fe-CNFM-Cl performed effectively over a broad pH range of 3-9. Common anions and humic acid hardly inhibit As(III) removal except at high concentrations of phosphate. During the removal of As(III), a portion of As(III) was oxidized to As(V) by activated chlorine. The adsorption and oxidation capacity of the used Fe-CNFM-Cl could be well recovered by desorption with NaOH solution followed by chlorination with NaClO solution. In addition, it could reliably purify the As(III) levels in natural groundwater to below 10 μg L-1. The study contributes a novel strategy for the development of multifunctional iron-based cellulose biocomposite sorbents for the effective removal of As(III) from water.

Continuously enhanced versatile nanocellulose films enabled by sustaining CO2 capture and in-situ calcification

Cellulose possesses numerous favorable peculiarities to replace petroleum-based materials. Nevertheless, the extremely high hygroscopicity of cellulose severely degrades their mechanical performance, which is a major obstacle to the production of high-strength, multi-functional cellulose-based materials. In this work, a simple strategy was proposed to fabricate durable versatile nanocellulose films based on sustaining CO2 capture and in-situ calcification. In this strategy, Ca(OH)2 was in-situ formed on the films by Ca2+ crosslinking and subsequent introduction of OH-, which endowed the films with high mechanical strength and carbon sequestration ability. The following CO2 absorption process continuously improved the water resistance and durability of the films, and enabled them to maintain excellent mechanical properties and promising light management ability. After a 30-day CO2 absorption process, the water contact angle of the films can be increased from 43° to 79°, and the weight gain rate of the films in a 30 h water-absorption process can be sharply decreased from 331.2 % to 52.2 %. The films could maintain a high tensile strength of 340 MPa, and result in a CO2 absorption rate of 3.5 mmol/gcellulose after 30 days. In this study, the improvement of durability and carbon sequestration of nanocellulose films was achieved by a simple and effective method.

Water resistant, biodegradable and flexible corn starch/carboxymethyl cellulose composite film for slow-release fertilizer coating materials

The inherent limitations of Cornstarch (CS) and Carboxymethyl Cellulose (CMC) membranes, such as brittleness, fragility, and water solubility, limit their use in controlled-release fertilizers. This study reports on the synthesis of crosslinked CMC/CS-20-E composite membranes using the casting technique, with epichlorohydrin (ECH) as the crosslinking agent in an acidic environment to crosslink CS and CMC. The synthesized composite film demonstrates remarkable water resistance, as evidenced by the insignificant alteration in its morphology and structure post 72 h of water immersion. Its flexibility is reflected in its capacity to endure knotting and bending, with an elongation at break reaching 78.1 %. Moreover, the degradation rate surpasses 90 % within a span of seven days. The CMC/CS-20-E-x-urea controlled-release fertilizer was subsequently produced using a layer-by-layer self-assembly technique, where urea particles were incorporated into the crosslinked composite solution. This CMC/CS-20-E-x-urea controlled-release fertilizer displayed superior controlled-release performance over a duration of seven days when juxtaposed with pure urea. In particular, the CMC/CS-20-E-3 %-urea controlled-release fertilizer showed a cumulative release rate of 84 % by the seventh day. The controlled-release fertilizers developed in this study offer a promising strategy for creating eco-friendly options that are crucial for fertilizing crops with short growth cycles.

Amino-functionalized nanocellulose aerogels for the superior adsorption of CO2 and separation of CO2/CH4 mixture gas

Nanocellulose-based aerogels have been considered as one of the ideal candidates for CO2 capture in practical applications owing to their lightweight and porous properties. Additionally, various adsorbents with amine groups have been widely used as effective CO2 capture and storage strategies. Herein, amino-functionalized aerogels were prepared by sol-gel and freeze-drying methods using two typical nanocelluloses (cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs)) as substrates. In addition, the reaction parameters for grafting and amino functionalization were optimized. The CNC and CNF aerogels could be easily modified by the hydrothermal growth of the amino group, and they exhibited attractive properties in terms of CO2 adsorption, recyclability, thermal stability, hydrophobicity, and CO2/CH4 mixture separation. The amino-functionalized CNF aerogel exhibited superior performance to the CNC aerogel, which was attributed to the increased cross-linking binding sites for hydrogen bonding in the CNF aerogel. The results of this study indicated that amino-functionalized nanocellulose aerogels can be considered a promising biodegradable, sustainable, and environmentally friendly material for CO2 capture and removal of CO2 from CH4.

Nanocellulose-based composite aerogels toward the environmental protection: Preparation, modification and applications

Nanocellulose aerogel has the advantages of porosity, low density and high specific surface area, which can effectively realize the adsorption and treatment of wastewater waste gas. The methods of preparing nanocellulose mainly include mechanical, chemical and biological methods. Nanocellulose is formed into nanocellulose aerogel after gelation, solvent replacement and drying processes. Based on the advantages of easy modification of nanocellulose aerogels, nanocellulose aerogels can be functionalized with conductive fillers, reinforcing fillers and other materials to give nanocellulose aerogels in electrical, mechanical and other properties. Through functionalization, the properties of nanocellulose composite aerogel such as hydrophobicity and adsorption are improved, and the aerogel is endowed with the ability of electrical conductivity and electromagnetic shielding. Through functionalization, the applicability and general applicability of nanocellulose composite aerogel in the field of environmental protection are improved. In this paper, the preparation and functional modification methods of nanocellulose aerogels are reviewed, and the application prospects of nanocellulose composite aerogels in common environmental protection fields such as dye adsorption, heavy metal ion adsorption, gas adsorption, electromagnetic shielding, and oil-water separation are specifically reviewed, and new solutions are proposed.

Comparing the separation performance of poly(ethyleneimine) embedded butyric and octanoic acid based chromatographic stationary phases

Poly(ethyleneimine) (PEI) modified silica spheres were used to graft butyric acid and octanoic acid onto their surfaces, forming two stationary phases named Sil-PEI-BAD and Sil-PEI-CAD, respectively. Characterized methods including fourier transform infrared spectroscopy (FT-IR), elemental analysis (EA) and thermogravimetric analysis (TGA) were utilized to determine the successful synthesis of these two stationary phase materials. The chromatographic performance of these two stationary phases was analyzed with hydrophobic and hydrophilic compounds as analytes. Compared with Sil-PEI-CAD column, Sil-PEI-BAD column was more effective in separating hydrophilic compounds including nucleosides, alkaloids and vitamins. Hydrophobic substances including polycyclic aromatic hydrocarbons (PAHs) and alkylbenzenes obtained excellent separation results on Sil-PEI-CAD column than Sil-PEI-BAD column. Additionally, according to the separation of phenols, Sil-PEI-CAD column can be used in HILIC/RPLC mixed-mode. The results showed that the properties and retention mechanisms of the prepared stationary phases depended on the length of the alkyl chains bonded on the silica surface.

Carbonized Aminal-Linked Porous Organic Polymers Containing Pyrene and Triazine Units for Gas Uptake and Energy Storage

Porous organic polymers (POPs) have plenteous exciting features due to their attractive combination of microporosity with π-conjugation. Nevertheless, electrodes based on their pristine forms suffer from severe poverty of electrical conductivity, precluding their employment within electrochemical appliances. The electrical conductivity of POPs may be significantly improved and their porosity properties could be further customized by direct carbonization. In this study, we successfully prepared a microporous carbon material (Py-PDT POP-600) by the carbonization of Py-PDT POP, which was designed using a condensation reaction between 6,6'-(1,4-phenylene)bis(1,3,5-triazine-2,4-diamine) (PDA-4NH₂) and 4,4',4'',4'''-(pyrene-1,3,6,8-tetrayl)tetrabenzaldehyde (Py-Ph-4CHO) in the presence of dimethyl sulfoxide (DMSO) as a solvent. The obtained Py-PDT POP-600 with a high nitrogen content had a high surface area (up to 314 m² g^-1), high pore volume, and good thermal stability based on N₂ adsorption/desorption data and a thermogravimetric analysis (TGA). Owing to the good surface area, the as-prepared Py-PDT POP-600 showed excellent performance in CO₂ uptake (2.7 mmol g^-1 at 298 K) and a high specific capacitance of 550 F g^-1 at 0.5 A g^-1 compared with the pristine Py-PDT POP (0.24 mmol g^-1 and 28 F g^-1).