Double Gel Research Articles

The physical and structural properties of acid–Ca2+ induced casein–alginate/Ca2+ double network gels

The design of protein or polysaccharide interpenetrating network gels according to their physicochemical properties is required to obtain the desired properties of hydrogels. In this study, a method was proposed to prepare casein–calcium alginate (CN–Alg/Ca2+) interpenetrating double-network gels by the release of calcium from a calcium retarder during acidification to form calcium–alginate (Alg/Ca2+) gel and casein (CN) acid gel. Compared with the casein–sodium alginate (CN–Alg) composite gel, the CN–Alg/Ca2+ dual gel network with an interpenetrating network gel structure has better water-holding capacity (WHC) and hardness. The rheology and microstructure results showed that the dual-network gels of CN and Alg/Ca2+ induced by gluconic acid–δ-sodium (GDL) and calcium ions were the network structure of the Alg/Ca2+ gel, which was the “first network”, and the CN gel, which was the “second network”. It was proven that the microstructure, texture characteristics, and WHC of the double-network gels could be regulated by changing the concentration of Alg in the double-network gels and that the 0.3 % CN–Alg/Ca2+ double gels showed the highest WHC and firmness values. The aim of this study was to provide useful information for the preparation of polysaccharide–protein mixed gels in the food industry or other fields.

Study on the inhibition performance of double network physicochemical nanocomposite gel inhibitor on coal spontaneous combustion

To strengthen the inhibition effect of an inhibitor on spontaneous coal combustion throughout the process, this study used solution polymerization to synthesize hyaluronic acid and polyethylene glycol into a double network gel. The double network gel was grafted with a chemical inhibitor, epigallocatechin gallate, and polymerized with nanomaterial attapulgite to prepare a double network gel composite inhibitor with a whole-process inhibition effect. From the results of the scanning electron microscopy test, we found that the folds and pores on the surface of the inhibitor considerably increased with composite treatment. From the results of thermogravimetric analysis, it was proved that the average increase in each characteristic temperature point of the coal sample was 28.15%. According to the results of differential scanning calorimetry, it was found that the heat release interval of the inhibited sample was narrowed, and the total heat release was reduced by 2408.08 J/g. From the results of gas analysis, it was concluded that the production of CO, CO2, and CH4 by the inhibited sample markedly reduced, which verified the environmental friendliness of the inhibitor. Through a diffuse reflection infrared spectrum test, it was found that the inhibition treatment could deactivate the active groups in coal and increase the content of the ether bonds of the stable functional groups, which proved that the composite inhibitor is an excellent fire prevention material.

Formation of Composite Coatings of Layered Double Hydroxide Particles and Hydroxide Gel by Electrophoretic Deposition on Mg Alloy and Corrosion Resistance

To improve the corrosion resistance of Mg alloys, composite coatings of layered double hydroxide intercalated with carbonate (LDH-CO3, hydrotalcite) particles and magnesium and aluminum hydroxide gel were formed on AZ31 Mg alloy by electrophoretic deposition (EPD) using the LDH-CO3 suspension with Mg(NO3)2 and Al(NO3)3 in total of 1.25–125 mmol/L. Wet-dry cyclic corrosion tests were performed for the coated specimens after ultrasonication. LDH-CO3 particle-rich layer and magnesium and aluminum hydroxide gel-rich layer almost alternately piled up to form a composite layer. The hydroxide gel adhered the particles together and to the substrate. At the bottom of the composite layer, flake-shape LDH-structured substance densely covered the substrate surface. The coverage and thickness of the composite layer increased from sub-micrometers to 30 µm with an increase of Mg and Al ion concentrations of the suspension. By ultrasonication, parts of the composite layer delaminated to expose the LDH-structured substance layer, while the coverage by the remaining composite layer increased with an increase of Mg and Al ion concentrations. The LDH-CO3 particles and hydroxide gel composite coatings prevented corrosion initiation even in the areas where the LDH-structured substance layer was exposed.

Fabrication of grape seed proanthocyanidin-loaded W/O/W emulsion gels stabilized by polyglycerol polyricinoleate and whey protein isolate with konjac glucomannan: Structure, stability, and in vitro digestion

In this work, the effects of konjac glucomannan (KGM) concentrations on microstructure, gel properties, stability and digestibility of water-in-oil-in-water emulsion gels stabilized by polyglycerol polyricinoleate and whey protein isolate were investigated. Visual appearance indicated that a non-layered double emulsion gel was formed when KGM increased to 0.75%. Emulsion gels with 1.5% KGM showed the highest encapsulation, freeze-thaw and photochemical stability due to the formation of the smallest droplets, which were supported by microscopic observations. Moreover, the addition of KGM improved water holding capacity, rheological and texture properties of emulsion gels. Particularly, at 1.5% or 1.75% KGM, color and potential of hydrogen showed the most stable level after 14 days of storage. During in vitro digestion, KGM delayed the hydrolysis of protein and oil droplets, and then improved the bioavailability of grape seed proanthocyanidin. These results promoted the application of KGM in emulsion gels and the encapsulation of nutraceuticals.

Agar-PVA/GO double network gel electrolyte for high performance flexible zinc-air batteries

Flexible zinc-air batteries (FZABs) have attracted a lot of attention because of their high energy density, low cost, and good safety. As the ‘blood’ of FZABs, electrolytes are one of the research focuses. In this paper, we report a double network hydrogel as FZABs electrolyte. The hydrogel is cross-linked by stiff agar as the first network and tough polyvinyl alcohol microcrystals and polymer chains as the second network. The maximum extension at maximum tensile strength (388 Kpa) of the prepared double network gel is close to 246%. The gel is suitable for alkaline and neutral electrolytes in FZABs. The alkaline gel electrolyte has high ionic conductivity (75 mS/cm) and the assembled alkaline FZAB has a high power density of 123.7 mW/cm2. While the better water retention of neutral gel electrolyte makes it more stable, the assembled neutral FZAB has a long discharge time and favorable cycle life of more than 60 h at a current density of 0.5 mA/cm2. In addition, FZABs can not only change shape and size but also operate under different bending conditions without reducing the electrochemical performance, indicating that high-performance FZABs assembled by this electrolyte with efficient, safe, and flexible, and have great potential for applications.

Agarose/konjac glucomannan double network hydrogels to mimic the texture of beef tripe

Beef tripe is widely consumed in the world due to its favorable texture. However, the large-scale cultivation of cattle for producing tripe would exacerbate living environment, and therefore the development of artificial beef tripe is necessary. To imitate the texture of authentic beef tripe, we fabricated the agarose (AR)/konjac glucomannan (KGM) double network hydrogels (DNs) with outstanding mechanical properties using heating-cooling combined with sodium carbonate immersion strategy, and further compared them with beef tripe. Notably, the optimized DNs demonstrated a significantly increased mechanical strength of 450% and 340% than single AR and KGM gels, respectively. Further study revealed that the soft networks (KGM) mainly maintained the elasticity of the hydrogels, whereas the rigid networks (AR) were integrated inside the large soft network framework and acted as “load carriers” to efficiently dissipate energy. Correlation analysis and sensory attributes analysis indicated that the AR/KGM DNs with a mass ratio of 1:4 presented the most comparable texture properties with beef reticulum and rumen cooked, showing the great potential as artificial beef tripe. • Agarose/konjac glucomannan double network gel was built by a two-step procedure. • Agarose/konjac glucomannan double network gel had outstanding mechanical property. • Optimized agarose/konjac glucomannan gel showed comparable texture to beef tripe.

The preparation of soy glycinin/sugar beet pectin complex network gels catalyzed by laccase under weakly acidic conditions.

Traditional soy protein gel products such as tofu, formed from calcium sulfate or magnesium chloride, have poor textural properties and water retention capacity. Soy glycinin (SG) is the main component affecting the gelation of soy protein and can be cross-linked with polysaccharides, such as sugar beet pectin (SBP), and can be modified by changing system factors (e.g., pH) to improve the gel's properties. Soy glycinin/sugar beet pectin (SG/SBP) complex double network gels were prepared under weakly acidic conditions using laccase cross-linking and heat treatment. The structural changes in SG and the properties of complex gels were investigated. Soy glycinin exposed more hydrophobic groups and free sulfhydryl groups at pH5.0. Under the action of laccase cross-linking, SBP could promote the unfolding of SG tertiary structures. The SG/SBP complex gels contained 46.77% β-fold content and had good gelling properties in terms of hardness 290.86 g, adhesiveness 26.87, and springiness 96.70 mm at pH5.0. The T22 relaxation time had the highest peak, and magnetic resonance imaging (MRI) showed that the gel had even water distribution. Scanning electron microscopy (SEM) and confocal scanning laser microscopy (CLSM) indicated that the SG/SBP complex network structure was uniform, and the pore walls were thicker and contained filamentous structures. Soy glycinin/ sugar beet pectin complex network gels have good water-holding, rheological, and textural properties at pH5.0. The properties of soy protein gels can be improved by binding to polysaccharides, with laccase cross-linked, and adjusting the pH of the solution. © 2022 Society of Chemical Industry.

Reproducibility of double agar gel immunodiffusion test using stored serum and plasma from paracoccidioidomycosis patients.

Serological evaluation performed by double agar gel immunodiffusion test (DID) is used for diagnosis, evaluation of severity, management of paracoccidioidomycosis patients, and development of new clinical studies. For these reasons, the Botucatu Medical School of UNESP maintains a serum bank at the Experimental Research Unit with patient clinical data. This study aimed to evaluate the influence of the freeze-thaw cycle and different blood matrices on the titration of circulating antibodies. The study included 207 patients with confirmed (etiology-demonstrated) or probable (serology-demonstrated) paracoccidioidomycosis, and DID was performed with culture filtrate from Paracoccidioides brasiliensis B339 as antigen. First experiment: the antibody levels were determined in serum samples from 160 patients with the chronic form and 20 with the acute/subacute form, stored at -80oC for more than six months. Second experiment: titers of 81 samples of serum and plasma with ethylenediaminetetraacetic acid (EDTA) or heparin, from 27 patients, were compared according to matrix and effect of storage at -20oC for up to six months. Differences of titers higher than one dilution were considered discordant. First experiment: test and retest presented concordant results in serum stored for up to three years, and discordant titers in low incidence in storage for four to six years but high incidence when stored for more than six years, including conversion from reagent test to non-reagent retest. Second experiment: serum, plasma-EDTA and plasma-heparin samples showed concordant titers, presenting direct correlation, with no interference of storage for up to six months. Storage at -80oC for up to six years has no or little influence on the serum titers determined by DID, permitting its safe use in studies depending on this parameter. The concordant titrations in different blood matrices demonstrated that the plasma can be used for immunodiffusion test in paracoccidioidomycosis, with stability for at least six months after storage at -20oC.

Effect of temperature, rate, and molecular weight on the failure behavior of soft block copoly(ether-ester) thermoplastic elastomers.

Thermoplastic elastomers (TPEs) based on multiblock copolymers are an important class of engineering polymers. They are widely used in many applications where flexibility and durability are required and are seen as a sustainable (recyclable) alternative to thermoset rubbers. While their high-temperature mechanical behavior has received recent interest, few studies have explored their fracture and fatigue behavior. Understanding how the temperature and rate-dependence of the deformation behavior at both a local and global scale influences the fatigue resistance and failure behavior is critical when designing with these materials. In this study, the failure behavior in tensile, fracture, and fatigue of well-characterized, industrially relevant, model block copoly(ether-ester) based TPEEs were evaluated over a wide range of temperatures, deformation rates, and molecular weights. Small changes in temperature or rate are shown to result in a sharp transition between a highly deformable and notch resistant response, to a more brittle and strongly notch-sensitive response. This behavior surprisingly manifests itself as a threshold strain below which the cracks do not propagate in fatigue and increasing deformation rates decreases the materials toughness in fracture tests, whereas in tensile tests the opposite is observed. The change from homogenous to inhomogeneous stress fields for tensile and fracture experiments coupled with the viscoelasticity and strain-dependent morphology of TPEs explains why a different rate dependency is observed. Strain and stress delocalization is key to achieve high toughness. Digital Image Correlation is used to measure the size and time dependence of the process zone. Comparison with micromechanical models developed for soft, elastic, and tough double network gels highlights the dominance of high strain properties for toughness and explains the strong molecular weight dependence. However, to understand the rate dependence, the characteristic times for stress transfer from the crack tip and the time to nucleate failure must be compared. The results presented in this study demonstrate the complex effect of loading conditions on the intrinsic failure mechanisms of the TPE material, and provide a first attempt at rationalizing that behavior.

Ultrafast Self-Healing, Highly Stretchable, Adhesive, and Transparent Hydrogel by Polymer Cluster Enhanced Double Networks for Both Strain Sensors and Environmental Remediation Application.

Stretchable, healable, biocompatible, and conductive hydrogels are one of the promising candidates for both wearable electronics and environmental remediation applications. To date, the design of hydrogels that integrate ultrafast self-healing with high efficiency (seconds), high stretchability, and biocompatibility and reversibility into one system is not an easy task. Herein, we demonstrate a general oxidation approach to accelerate the hydrogelation of hPEI-based double network gels via the generation of fluorescent polymer clusters at room temperature or triggered by the heating-cooling process. The resulting ohPEI hydrogel has the merit of biocompatibility over most reported hPEI hydrogels for strain sensors. It shows a high conductivity (1.3 S/m), an ultrafast self-healing ability (<3 s, 98% healing efficiency within 60 s), a high stretchability (∼1850 and ∼7000% in deformation), and reversible adhesivity on various material surfaces. The excellent performance of the hydrogel is ascribed to the cooperative and hierarchical interactions of four types of dynamic combinations, including the reversible borate bond, hydrogen bonding, electrostatic interaction, and polymer cluster interactions. The reversible fabrication process by the one-spot method (just by simple mixing of the components) and superior properties of the hydrogel make it an ideal candidate for a wearable strain sensor to monitor human motions and physiological activities. Moreover, it is also a good hydrogel absorbent for phase separation absorption of volatile organic compounds with a high capacity (for acetone: 4.75 g g-1), reusability, and an easy handling process.

Flexible hydrogel with a coupling enhanced thermoelectric effect for low-grade heat harvest

Harvesting abundant and ubiquitous low-grade thermal energy and simultaneously converting it into electrical energy hold the potential of solving the existing energy crisis. Advances in thermoelectric materials now allow thermoelectric ionogel electrolyte to enhance the energy conversion and storage capacities under a thermal gradient. Here, we report an ionic thermoelectric (i-TE) material based on polyacrylamide (PAM) carboxymethyl cellulose (CMC) double network gel substrate with flexible and high thermal-electrical conversion properties. By combining the thermodiffusion effect of lithium sulfate (Li2SO4) ions and the thermogalvanic effect of [Fe(CN)64−/Fe(CN)63−], which achieved a coupled ionic Seebeck effect of up to 11.58 mV/K, exhibiting a high ionic conductivity (18.4 mS cm−1) and low thermal conductivity (0.47 W m−1/K), resulting in a high ionic power factor (198.2 μW m−1K−2) at room temperature. It exhibited an excellent tensile property (634%) and adhesion, and avoids electrolyte leakage to a large extent. Moreover, the application in ionic capacitors also demonstrates the superior thermoelectric conversion capability of i-TE gels. We believe that i-TE materials will pave a new pathway for low-grade thermal harvesting and self-driven flexible wearable electronics.

Tough, highly adaptable and self-healing integrated supercapacitor based on double network gel polymer electrolyte

Flexible supercapacitor has been proved a promising candidate for wearable electronics due to its high power density, fast charge/discharge rates and long life cycle. Gel polymer electrolyte (GPE), an important component of supercapacitor, combines high ionic conductivity of liquid electrolyte and great safety of solid electrolyte. To satisfy the practical application of wearable flexible devices, the GPE should possess outstanding mechanical properties. Herein, a fully physical cross-linked polyacrylamide/κ-carrageenan double network GPE is prepared, in which κ-carrageenan with double-helix structure is used as the first network and polyacrylamide acts as the second network. The double network GPE shows outstanding mechanical properties, including high tensile strength (0.33 MPa), elongation (1143%) and preeminent self-recovery performance. Moreover, owing to thermoreversible characteristic of κ-carrageenan and reversible hydrogen bonds, the GPE exhibits excellent self-healing performance. Furtherly, an integrated supercapacitor is fabricated by in-situ growing polyaniline on the GPE surface. Different from conventional sandwich-like structure of supercapacitor, this seamless connection between electrode and electrolyte layers can significantly lower interfacial resistance, and avoid displacement and separation under deformations. Meanwhile, this supercapacitor also demonstrates splendid self-healing performance and high adaptability during harsh conditions. This flexible self-healing supercapacitor with superior security has broad application prospects in portable and wearable electronics.

Fabrication of double emulsion gel using monoacylglycerol and whey protein concentrate: The effects of primary emulsion gel fraction and particle size

The fabrication of novel double emulgels (DEGs; O/W/O) was examined upon gelling all three phases as oleogel-in-hydrogel-in-oleogel using monoacylglycerol (MAG) and whey protein concentrate (WPC) as gelling agents. Various water proportions from 6.8% to 27.2% (w/w) were incorporated using High-intensity ultrasound (HIU). The HIU effectively stabilised the DEGs for >20 days owing to reducing the particle size of the inner oil phase (from 56.1 μm to 6.5 μm) and causing WPC gelling, immobilising the water phase. The increase in water fraction altered the particle size, whilst the DEG30 sample with 20.4% (w/w) water content reinforced the hardness value (0.48 N) and gel strength. The DEG30 was further treated with various levels of HIU to obtain different particle sizes (104 μm, 67 μm, 88 μm, and 49 μm). The reduction in particle size impacted the final DEGs' rheological behaviour, texture, and Tgel-sol transition temperatures.

Time-resolved microstructural changes in large amplitude oscillatory shear of model single and double component soft gels

Soft particulate gels can reversibly yield when sufficient deformation is applied, and the characteristics of this transition can be enhanced or limited by designing hybrid hydrogel composites. While the microscopic dynamics and macroscopic rheology of these systems have been studied separately in detail, the development of direct connections between the two has been difficult, particularly with regard to the nonlinear rheology. To bridge this gap, we perform a series of large amplitude oscillatory shear (LAOS) numerical measurements on model soft particulate gels at different volume fractions using coarse-grained molecular dynamics simulations. We first study a particulate network with local bending stiffness and then we combine it with a second component that can provide additional cross-linking to obtain two-component networks. Through the sequence of physical processes (SPP) framework, we define time-resolved dynamic moduli, and by tracking the changes in these moduli through the period, we can distinguish transitions in the material behavior as a function of time. This approach helps us establish the microscopic origin of the nonlinear rheology by connecting the changes in dynamic moduli to the corresponding microstructural changes during the deformation including the nonaffine displacement of particles, and the breakage, formation, and orientation of bonds.

Unlocking the potentials of gel conformance for water shutoff in fractured reservoirs: Favorable attributes of the double network gel for enhancing oil recovery

The double-network prepared with an in-situ monomer gel and a fast-crosslinked Cr(III) gel is introduced to develop a thixotropic and high-strength gel (THSG), which is found to have many advantages over the traditional gels. The THSG gel demonstrates remarkable thermal stability, and no syneresis is observed after 12 months with high salinity brine (95,500 mg/L). Moreover, the SEM and XRD results indicate that the gel is intercalated into the lamellar structures of Na-MMT, where the gel can form a uniform and compact structure. In addition, the THSG gel has an excellent swelling behavior, even in the high salinity brine. In the slim tube experiments, the THSG gel exhibits high rupture pressure and improves blocking capacity after being ruptured. The core flooding results show that a layer of gel filter cake is formed on the face of the fracture, which may be promoted by a high matrix permeability, a small aperture fracture, and a high injection rate. After the gel treatment, the fracture can be completely blocked by the THSG gel. It is found that a high incremental oil recovery (65.3%) can be achieved when the fracture was completely blocked, compared to 40.2% if the gel is ruptured. Although the swelling of ruptured gel can improve oil recovery, part of the injected brine may be channeled through the gel-filled fractures, resulting in a decrease in the sweep efficiency. Therefore, the improved blocking ability by gel swelling (e.g., in fresh water) may be less efficient to contribute to an enhancement of oil recovery. It is also found that the pressure gradient and residual resistance factor to water (Frrw) are higher if the matrix is less permeable, indicating that the fractured reservoir with lower matrix permeability may require a higher gel strength for treatment. The findings of this study may provide novel insights on designing robust double network gels for water shutoff in fractured reservoirs.

A double network conductive gel with robust mechanical properties based on polymerizable deep eutectic solvent

Hydrogels with excellent biocompatibility have become hot topics in the field of flexible electronic wearability. However, high water content and poor mechanical properties limit its application, especially in low temperature environment. We filled the deep eutectic solvent (DES) into the porous structure of polyacrylamide hydrogel (PAAM) by impregnation displacement method. Free radical polymerization was performed in the hydrogel pores using a deep eutectic solvent to form a double-network composite gel with excellent mechanical properties and low temperature resistance. By adjusting the substitution ratio of polyacrylamide hydrogel and deep eutectic solvent, the conductive and mechanical properties of the composite gel were flexibly adjusted. There were a large number of amide and carboxyl functional groups in the composite gel with double network structure, which could form strong hydrogen bond interaction and gave the composite gel excellent mechanical properties (strain up to 1373 %, stress up to 3.14 MPa). In addition, the choline chloride in the deep eutectic solvent provided the gel with good electrical conductivity (∼0.21 ms/cm). Since the water in the composite gel was replaced by a deep eutectic solvent, the gel could resist low temperature (−20 ℃). The large stress-strain gels open up a new way to fabricate organic transparent conductive elastomers for a myriad of future applications in flexible electronics.

Fabrication of WPI-EGCG covalent conjugates/gellan gum double network emulsion gels by duo-induction of GDL and CaCl2 for colon-controlled Lactobacillus Plantarum delivery

In this study, we demonstrated the role of whey protein isolate (WPI)/(−)-epigallocatechin-3-gallate (EGCG) covalent conjugates/gellangum double network emulsion gels by duo-induction of glucono-δ-lactone (GDL) and CaCl2 on the digestion viability of Lactobacillus Plantarum powders. We employed a novel one-step continuous cold gelation strategy to product double network emulsion gels. The gellan gum in continuous phase was first induced by CaCl2 to form a gel in a short time. Besides, the GDL was improved covalent cross-linking between WPI-EGCG covalent conjugate Pickering particles or particle-coated oil droplets because of the slowly pH reduction. The first cross-linked gellan gum gels could be more closely integrated into the GDL-induced second gel networks with synergistic role, which promoted the formation of compact and homogeneous networks through hydrophobic interactions and disulfide bonds. Thus, the results provide a promising strategy for probiotic powders encapsulation of double network emulsion gels in oral applications of gel type foods.

A self-designed double cross-linked gel for flexible zinc-air battery with extreme conditions adaptability

Flexible zinc-air batteries have attracted more and more attention as an efficient and promising energy storage system. However, traditional gel electrolytes and flexible batteries have disadvantages such as poor mechanical properties and weak adaptability to extreme conditions. Here, we report a self-designed double cross-linked high-performance gel electrolyte (PAAK-M) for flexible zinc-air batteries,which is synthesized by polymerization of acrylamide (AM) monomer with the neutralized product of acrylic acid (AA) and potassium hydroxide (KOH) under heating conditions. Benefiting from the unique mechanical structure and excellent performance of PAAK-M gel, the assembled flexible zinc-air battery exhibits a high power density of 126 mW cm−2 and a long cycle life of over 55 h at room temperature. More importantly, the battery not only shows remarkable electrochemical performance over a wide temperature range (−20 °C to 100 °C), but also has good stability and practicality under various extreme conditions. Two zinc-air batteries integrated in series canreliably provide energy for LEDs and electronic clock. This study opens up a new idea for the development of high-performance gel electrolytes and provides a new strategy for the research of flexible batteries with the ability to adapt to extreme conditions.

Adsorption of As(V) by magnetic alginate-chitosan porous beads based on iron sludge

Magnetic alginate-chitosan porous beads based on iron (Fe) sludge (M-ACFBs) were prepared by waterworks iron sludge, sodium alginate, chitosan, and magnetic nanoparticles. The magnetic nanoparticles were also synthesized using waterworks iron sludge through the co-precipitation method. In addition, a double gel network of sodium alginate and chitosan was constructed to improve the pH stability of the beads. At the same time, iron sludge served as the functional body for As(V) adsorption. The beads have uniform bead size (∼2 mm), high specific surface area (115.4 m2/g), distinguished mesopores (5.7 nm in size), and strong saturation magnetization (∼15.0 emu/g). The ratio of magnetic nanoparticles to iron sludge was optimized, and the effects of pH, contact time, temperature, and coexisting ions on As(V) adsorption effect were studied. Also, the adsorption kinetics and adsorption isotherms are thoroughly discussed. The adsorption mechanism of M-ACFBs on As(V) is concluded as ligand exchange and electrostatic attraction, and the maximum adsorption capacity is as high as 14.2 ± 0.4 mg/g. It is found that magnetite (Fe3O4) can form a maghemite (γ-Fe2O3) layer in an oxygen-rich environment, and at the surface of this γ-Fe2O3 layer, Fe(II), O2, and As(V) undergo complex redox reactions, leading to the appearance of As(III), which leads to a challenge for the disposal of arsenic-loaded adsorbents. This study provides a reference pathway for the resource utilization of backwash iron sludge and As(V) removal from water.

Design and structural characterization of edible double network gels based on wheat bran arabinoxylan and pea protein isolate

Double network (DN) gels based on wheat bran arabinoxylan (WBAX) and pea protein isolate (PPI) were fabricated by a two-step sequential gelation method with laccase catalyzed cross-linking followed by heating. The rheological properties, water holding capacity, microstructure and molecular structure of WBAX/PPI DN gels were investigated. Increasing the concentrations of WBAX and PPI contributed to an enhanced viscoelastic modulus of DN gel, which exhibited an interconnected, bicontinuous and compact structure with smaller pore sizes, as a result of higher cross-linking intensity of WBAX molecules. Low field nuclear magnetic resonance (LF-NMR) results showed that increasing the contents of PPI and WBAX could further restrict the water mobility within DN gel, which was beneficial for enhancing the water holding capacity of gel samples. The molecular structure analysis showed that the crosslinking of WBAX-WBAX, PPI-PPI and WBAX-PPI participated in the formation of WBAX-PPI DN gels.