Phytic acid-modified carboxymethyl cellulose hydrogel for uranium adsorption from aqueous solutions

Phytic acid-modified carboxymethyl cellulose-based hydrogels for efficient removal of methylene blue dye

With the rapid development of science and technology, the discharge of industrial wastewater, especially dye wastewater, has caused great harm to the ecological environment. In response to the pollution caused by cationic organic dyes in industrial wastewater, this study employed free radical polymerization to prepare a new hydrogel adsorbent, PAA-PA-CMC, which exhibits both reusability and a large adsorption capacity. Phytic acid (PA) and carboxymethyl cellulose (CMC) were introduced into the acrylic acid-based polymer network using N, N '-methylene-bisacrylamide (MBA) and glycidyl methacrylate (GMA) as cross-linking agents. Phytic acid serves as both a cross-linking agent and an active component in the adsorption of methylene blue cationic dyes. Methylene blue (MB) adsorption experiments demonstrated that PAA-PA-CMC possesses a porous structure and abundant functional groups, primarily utilizing hydrogen bonds and electrostatic interactions for efficient MB adsorption. The adsorption capacity of PAA-PA-CMC for MB can reach 1005.41 mg/g and has good reusability. After 5 cycles, its adsorption efficiency remains at about 85 %. The adsorption behavior of PAA-PA-CMC conforms to the pseudo-second-order kinetic model and the Langmuir isotherm adsorption model, which is a monolayer chemical adsorption. In summary, the PAA-PA-CMC hydrogel prepared in this investigation shows great potential for treating MB dye wastewater.

Fully biobased and robust antibacterial cellulose aerogel for uranium extraction

Developing efficient adsorbent is imperative for the utilization of uranium resources in seawater. Marine microorganisms and bacteria play an important role in the process of adsorption of uranium. In this work, a completely bio-based antimicrobial aerogel (quaternary cellulose/chitosan aerogel-QCNF/CS) was prepared by cross-linking quaternary cellulose nanofibers (QCNF) and chitosan (CS) via citric acid (CA). The QCNF/CS aerogel has a high adsorption capacity of 565.97 mg g1, high selectivity (Kd = 1.6 × 104 mL g-1). Moreover, the incorporation of CS improved the mechanical properties and enhanced the shape recovery property. The adsorption system reached equilibrium within 300 min and had good recovery of 93 % for UO22+. After seven cycles of adsorption-desorption, QCNF/CS aerogel still maintained its original structure and retained 80.7 % of its initial adsorption capacity. The introduction of quaternary ammonium salt groups gives the QCNF/CS aerogel strong antimicrobial activity, and the inhibition rate can be up to 96 %. The aerogel also showed good adsorption performance in spiked natural seawater. DFT results and XPS analysis further indicated that -COOH of CA and -OH of CNF functional groups could enhance the adsorption capacity of QCNF/CS aerogel. Therefore, QCNF/CS aerogel was a potential adsorbent for the extraction of uranium from seawater.

An Amidoxime-functionalized chitosan dual-network hydrogel: Enhanced uranium-water separation capacity

The source and after treatment of uranium, a key aspect of its use as a nuclear fuel, had been a topic of intense debate among developers. Therefore, a novel antimicrobial amidoxime-functionalized chitosan/polyacrylamide dual network hydrogel (CP-AO) had been developed utilizing a straightforward methodology. The results demonstrated excellent adsorption capacity and selectivity for uranium extraction under varying conditions, the U(VI) removal was above 94 % when pH was 4. Batch adsorption experiments revealed that CP-AO attained a maximum uranium adsorption capacity of 886.73 mg/g at 298 K, which was higher than most reported adsorbents. The kinetic and thermodynamic studies presented that adsorption process for CP-AO conformed to spontaneous monolayer chem-adsorption, and it can reach equilibrium quickly within 120 min. In addition, the adsorption mechanism revealed that the chemical-interaction between CP-AO hydrogel and U(VI) was attributed to -OH, -NH2 and amidoxime group. Notably, the hydrogel showed optimistic anti-biosludge performance against three common bacteria (E. coli, S. aureus and B. subtilis) owing to effects of chitosan. CP-AO also especially was susceptible to be recycled, its adsorption capacity was 2.8 mg/g and 38.67 mg/g in simulated and actual seawater, respectively. Hence, this work provides a promising material for the extraction of uranium resources and new insights.

Biodegradable coating constructed from carboxycellulose nanofibers for high photocatalytic decomposition of ethylene and synergistic antibacterial what of perishable fruits

Postharvest fruits, especially climacteric fruits, are prone to ethylene ripening, browning and aging, microbial growth accelerated decay and other problems in natural environment. Herein, a carboxylated cellulose nanofibers/phytic acid‑titanium dioxide nanoparticles (CPT) biodegradable coating with "photocatalytic antibacterial barrier" structure，was developed by homogeneous dispersion of phytic acid(PA) complexed titanium dioxide nanoparticles (TNPs) in carboxylated cellulose nanofibers(CCNF). The CPT coating achieves effective dispersion and efficient utilization of TNPs through the complexation of PA. The coating ethylene clearance rate of CPT up to 70.89 %. Meanwhile, the coating exhibits excellent antibacterial (99.67 %), UV resistance, gas barrier. It was found that the CPT coating delays fruit ripening caused by ethylene, which effectively maintaining the quality of respiratory climacteric fruits and non- climacteric fruits, extending the shelf life of perishable fruit by up to 9 days. In particular, the coating is virtually biodegradable in soil after 21 days, which offers the possibility of replacing non-biodegradable multifunctional coatings in food packaging.

High-efficiency and economical uranium extraction from seawater with easily prepared supramolecular complexes

Developing effective adsorbents for uranium extraction from natural seawater is strategically significant for the sustainable fuel supply of nuclear energy. Herein, stable and low-cost supramolecular complexes (PA-bPEI complexes) were facilely constructed through the assembly of phytic acid and hyperbranched polyethyleneimine based on the multiple modes of electrostatic interaction and hydrogen bonding. The PA-bPEI complexes exhibited not only high uptake (841.7 mg g-1) and selectivity (uranium/vanadium selectivity = 84.1) toward uranium but also good antibacterial ability against biofouling. Mechanism analysis revealed that phosphate chelating groups and amine assistant groups coordinated the uranyl ions together with a high affinity. To be more suitable for practical applications, powdery PA-bPEI complexes were compounded with sodium alginate to fabricate various macroscopic adsorbents with engineered forms, which achieved an extraction capacity of 9.0 mg g-1 in natural seawater after 50 days of testing. Impressively, the estimated economic cost of the macroscopic adsorbent for uranium extraction from seawater ($96.5 ∼ 138.1 kg-1 uranium) was lower than that of all currently available uranium adsorbents. Due to their good uranium extraction performance and low economic cost, supramolecular complex-based adsorbents show great potential for industrial uranium extraction from seawater.

Phytic Acid-Functional Cellulose Nanocrystals and Their Application in Self-Healing Nanocomposite Hydrogels

Cellulose nanocrystals (CNCs) have garnered significant attention as a modifiable substrate because of their exceptional performances, including remarkable degradability, high tensile strength, high elastic modulus, and biocompatibility. In this article, the successful adsorption of phytic acid (PA) onto the surface of cellulose nanocrystals @polydopamine (CNC@PDA) was achieved. Taking inspiration from mussels, a dopamine self-polymerization reaction was employed to coat the surface of CNCs with PDA. Utilizing Pickering emulsion, the CNC@PDA-PA nanomaterial was obtained by grafting PA onto CNC@PDA. An environmentally friendly hydrogel was prepared through various reversible interactions using poly(acrylic acid) (PAA) and Fe3+ as raw materials with the assistance of CNC@PDA-PA. By multiple hydrogen bonding and metal-ligand coordination, nanocomposite hydrogels exhibit remarkable mechanical properties (the tensile strength and strain were 1.82 MPa and 442.1%, respectively) in addition to spectacular healing abilities (96.6% after 5 h). The study aimed to develop an innovative approach for fabricating nanocomposite hydrogels with exceptional self-healing capabilities.

Amidoxime-grafted cotton fibers with anti-microbial sludge for efficient uranium recovery

Uranium as a nuclear fuel, its source and aftertreatment has been a hot topic of debate for developers. In this paper, amidoxime and guanidino-modified cotton fibers (DC-AO-PHMG) were synthesized by the two-step functionalization approach, which exhibited remarkable antimicrobial and high uranium recovery property. Adsorption tests revealed that DC-AO-PHMG had excellent selectivity and anti-interference properties, the maximum adsorption capacity of 609.75 mg/g. More than 85 % adsorption capacity could still be kept after 10 adsorption-desorption cycles, and it conformed to the pseudo-second-order kinetic model and the Langmuir adsorption isotherm model as a spontaneous heat-absorbing chemical monolayer process. FT-IR, EDS and XPS analyses speculated that the amidoxime and amino synergistically increased the uranium uptake. The inhibitory activities of DC-AO-PHMG against three aquatic bacteria, BEY, BEL (from Yellow River water and lake bottom silt, respectively) and B. subtilis were significantly stronger, and the uranium adsorption was not impacted by the high bacteria content. Most importantly, DC-AO-PHMG removed up to 94 % of uranium in simulated seawater and extracted up to 4.65 mg/g of uranium from Salt Lake water, which demonstrated its great potential in the field of uranium resource recovery.

One-step fabrication of millimeter-scale hollow vesicles with chitosan /DADMAC/ sodium alginate graft copolymer for enhanced anionic dye adsorption

Hollow vesicles are promising in water treatment due to their unique structure of the membrane and inner cavity. However, the adsorption capacity needs to be improved for targeted pollutants. Herein, millimeter-scale hollow vesicles were prepared with a one-step process of sequential stirring and grafting using chitosan, diallyldimethylammonium chloride, and sodium alginate as raw materials with the purpose of efficient removal of anionic dyes from wastewater. The composite vesicles were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The hollow vesicles showed the structure of the cationic membrane and the inner cavity, facilitating the dye adsorption. The adsorption capacity for the anionic dye Reactive Black 5 reached 698.1 mg/g, more than twice that of the binary composite vesicles without graft. The adsorption kinetics and isotherm data coincided with the pseudo-second-order and Langmuir models, respectively, and the adsorption mechanism was monolayer chemisorption. Moreover, the vesicles worked well in wide ranges of environment pH, temperature, and co-existing pollutants. They also possessed excellent cyclic regeneration performance, in which 93 % of the initial adsorption capacity was maintained after four cycles. These results indicate that the millimeter-scale hollow vesicles exhibit broad application prospects for wastewater purification.

Anchoring chitosan/phytic acid complexes on polypyrrole nanotubes as capacitive deionization electrodes for uranium capture from wastewater

Capacitive deionization (CDI) technology holds great potential for rapid and efficient uranyl ion removal from wastewater. However, the related electrode materials still have much room for research. Herein, chitosan/phytic acid complexes were anchored on polypyrrole nanotubes (CS/PA-PPy) to fabricate the electrode for the electrosorption of uranyl ions (UO22+). In this system, polypyrrole nanotubes provided specific channels for ion and electron diffusion, and chitosan/phytic acid complexes offered selective sites for UO22+ binding. The results demonstrated that CS/PA-PPy via electrosorption showed faster kinetics and higher uranium uptake than those via physicochemical adsorption. The maximum adsorption capacity toward UO22+ via electrosorption (1.2 V) could reach 799.3 mg g-1, which was higher than most of the reported CDI electrodes. Electrochemical measurements and experimental characterizations showed that the electrosorption of UO22+ by CS/PA-PPy was a synergistic effect of capacitive process and physicochemical adsorption, in which the capacitive mechanism involved the formation of an electric double layer from hollow polypyrrole nanotubes, whereas the coordination of phosphate, amino and hydroxyl groups with UO22+ was attributed to physicochemical adsorption. With the rational design of material, along with its excellent uranium removal performance, this work exhibited a novel and potential composite electrode for uranium capture via CDI from wastewater.

Sequential removal of phosphate and copper(II) ions using sustainable chitosan biosorbent

Although adsorbents are good candidates for removing phosphorus and heavy metals from wastewater, the use of biosorbents for the sequential treatment of phosphorus and copper has not yet been studied. Porous chitosan (CS)-based biosorbents (CGBs) were developed to adsorb phytic acid (PA), a major form of organic phosphate. This first adsorbate (PA) further served as an additional ligand (P-type ligand) for the CGBs (N-type ligand) to form a complex with the second adsorbate (copper). After the adsorption of PA (the first adsorbate), the spent CGBs were recycled and used as a new adsorbent to adsorb Cu(II) ions (the second adsorbate), which was expected to have a dual coordination effect through P, N-ligand complexation with copper. The interactions and complexation between CS, PA and Cu(II) ions on the PA-adsorbed CGBs (PACGBs) were investigated by performing FTIR, XPS, XRD, and SEM-EDS analyses. The PACGBs exhibited fast and enhanced adsorption of Cu(II) ions, owing to the synergistic effect of the amino groups of CS (the original ligand, N-type) and the phosphate groups of PA (an additional ligand, P-type) on the adsorption of Cu(II) ions. This is the first time that sequential removal of phosphorus and heavy metals by biosorbents has been performed using biosorbents.