Alginate Research Articles

Preparation of hydrogels from hydrochloric acid modified attapulgite for environmentally responsive fertilizers

ABSTRACT The inefficiency of traditional fertilizers in nutrient utilization has led to various ecological and environmental problems. Green agriculture requires environmentally friendly fertilizers that can respond to environmental changes to regulate nutrient release. In this study, N-isopropylacrylamide (NIPAm) and sodium alginate (SA) were utilized as monomers sensitive to temperature and pH variations, while hydrochloric acid-modified attapulgite (ATP) served as an inorganic filler to prepare composite hydrogels (SPAA) with environmentally responsive properties, and these composite hydrogels were used as carriers for the preparation of hydrogel fertilizers for urea. The results showed that the compositing of modified ATP could enhance the swelling properties of hydrogels. Compared with the blank sample, the maximum water absorption capacity of the ATP-composite hydrogel was enhanced by about 75.4%, and the water preserved by the ATP-composite hydrogel was about 2.75 times of that of the blank sample under drying condition of 30°C for 6 h. Meanwhile, hydrogel fertilizers SPAA-U(S) and SPAA-U(P) were prepared by solubilization adsorption and polymerization embedding in this study, and both fertilizers possessed slow-release characteristics, with nutrient release time in water exceeding 30 h. The nutrient release behavior of the fertilizers responded to the environment, and the slow-release effect was optimal under the conditions of 20°C and pH = 7. Under acidic, alkaline and high temperature conditions, the ability of the hydrogel to immobilize water molecules decreases, which also leads to easier release of urea from the hydrogel matrix along with water molecules. The hydrogel fertilizer developed in this work can improve the utilization of fertilizer and promote the high quality and sustainable development development of agriculture.

Effects of Cryoprotectants on the Physicochemical Properties of Bonito (Sarda sarda) Fillets Subjected to Multiple Freeze–Thaw Cycles

ABSTRACT In this study, bonito (Sarda sarda) fillets were treated with sucrose-sorbitol, sodium tripolyphosphate, and sodium alginate as cryoprotectants before freezing to prevent changes in fish muscle during multiple freezing cycles and frozen storage. Lower soluble protein contents were determined in cryoprotectant-treated groups than in the control group. Lower polar and non-polar free amino acid contents were determined with the sodium tripolyphosphate group in the last cycle compared to the other groups. Cryoprotectant-added fillets had higher water-holding capacity and lower hardness values than the control. It was determined that the most effective cryoprotectant was sodium tripolyphosphate.

Response of Cucurbit Fruit Fly (Zeugodacus cucurbitae) Coquilette to Gel Formulations of Protein Bait

In the integrated pest management of fruit flies, trapping is the most practical and effective component. Currently, cucurbit fruit flies are being trapped by employing the male attractant, cuelure. Protein baits attract both male and female fruit flies and they may be explored for their management. The present study was conducted at Agricultural College and Research Institute, TNAU, Madurai, Tamil Nadu during 2022 in which, protein baits were compared with the cuelure for their attraction to fruit flies by using electroantennogram. In field conditions, effectiveness of protein bait is restricted due to water loss by evaporation thus making the bait dry. In view of this, studies were conducted to compare the preference of fruit flies to protein baits & cuelure and evaluated advanced gel formulations of protein bait in attracting fruit flies. In electroantennogram studies, female fruit fly response was found to be better to proteinex bait volatiles followed by soybean bait and cue lure volatiles. Responses of male fruit flies were uniform to proteinex bait and cue lure followed by soybean bait. Among the gel formulations of liquid proteinex bait, using olfactometer, attraction response of pectin and sodium alginate gel formulations was similar to the attraction of liquid protein bait. The response recorded in olfactometer were seen in decreasing pattern while using xanthan gum powder and carrageenan powder gel formulations attracxted more number of fruit flies. In gated cup trap choice test, pectin powder gel formulation attracted more number of fruit flies followed by liquid proteinex bait.

Wet-Spinning Fabrication of Poly(3,4-vinyl dioxythiophene): Poly(styrenesulfonate)/Sodium Alginate Fibers Function as Intelligent Off/On Switchable Microwave Absorber

Wet-Spinning Fabrication of Poly(3,4-vinyl dioxythiophene): Poly(styrenesulfonate)/Sodium Alginate Fibers Function as Intelligent Off/On Switchable Microwave Absorber

Plasticizer modulation of dynamic mechanical properties and dielectric performance in sodium alginate-based biopolymer films

Abstract This work focuses on the effects of various plasticizers, such as glycerol (GLY), polyethylene glycol (PEG), and dioctyl phthalate (DOP) at 0%, 25%, and 50% concentrations, on the structure, dynamic mechanical behavior, and relaxation dynamics of charge carriers of sodium alginate (SA) film. The investigation of the structure was conducted using attenuated total reflectance fourier transform infrared (ATR-FTIR) and X-ray diffraction (XRD). The AT-FTIR analysis indicated changes in the OH and C–O bands of plasticized SA films, suggesting potential intermolecular interactions between the SA matrix and the plasticizers. Moreover, XRD revealed that GLY and PEG enhanced the amorphous phase of SA, promoting flexibility, while DOP increased crystallinity. Dynamic mechanical testing revealed that the pristine SA biofilm displayed a high storage modulus ( $$\:E^{\prime}$$ ) of 11 GPa at − 50 °C, indicating a stiff structure. The plasticization process with GLY, PEG, and DOP resulted in a decrease in the values to 0.09, 0.1, and 7.11 GPa, respectively, as well as a decrease in the glass transition temperature, which was attributed to weakened polymer chain interactions. The drastic reduction in storage modulus upon plasticization indicates enhanced flexibility. Dielectric measurements revealed significantly higher dielectric constants ranging from 1.65 × 106 to 0.12 × 106 at 0.1 Hz and direct current conductivity at lower frequencies, also decreasing in relaxation time for films plasticized with GLY and PEG linked to increased hydroxyl groups and higher amorphous content. These findings highlight the potential of SA films plasticized with GLY and PEG as advanced materials for electrochemical and conductive polymer electrode applications.

Cost-reduction strategy to culture patient derived bladder tumor organoids.

Organoids as self-organized structure derived from stem cells can recapitulate the function of an organ in miniature form which have developed great potential for clinical translation, drug screening and personalized medicine. Nevertheless, the majority of patient-derived organoids (PDOs) are currently being cultured in the basement membrane matrices (BMMs), which are constrained by xenogeneic origin, batch-to-batch variability, cost, and complexity. Besides, organoid culture relies on biochemical signals provided by various growth factors in the composition of medium. We propose sodium alginate hydrogel scaffold in addition to the fibroblast conditioned medium (FCM)-enriched culture medium that is inexpensive and easily amenable to clinical applications for the culture of bladder cancer PDOs. PDOs grown in sodium alginate and FCM based medium have proliferation potential, growth rate, and gene expression that are similar to PDOs cultured in BME. According to the results, sodium alginate has substantial mechanical properties and reduces variance in early passage bladder tumor organoid cultures collected from patients. Furthermore, using FCM based medium as an alternative solution to eliminate some essential growth factors can be considered, especially for low-resource situation and develop cost effective tumor organoids.

A Promising Approach for the Food Industry: Enhancing Probiotic Viability Through Microencapsulated Synbiotics

The role of prebiotics and probiotics in promoting gut health is increasingly recognized in food development and nutrition research. This study explored the enhancement of probiotic viability in the food industry through microencapsulated synbiotics, focusing on Lactiplantibacillus plantarum NCIMB 11974 with fructooligosaccharides (FOSs) and inulin as prebiotics. The effect of encapsulation in a chitosan-coated alginate matrix on probiotic survival under simulated gastrointestinal conditions showed a significant effect of 2% FOS concentration on the growth of Lactiplantibacillus plantarum NCIMB 11974. The optimization of microencapsulation parameters by the Taguchi method revealed a 2% sodium alginate concentration, a nozzle size of 200 µm, and a concentration of 0.4% chitosan solution as ideal, producing microcapsules with an estimated average diameter of 212 µm. Viability assessments in simulated gastric juice and simulated intestinal juice showed that chitosan-coated alginate microcapsules notably enhanced probiotic survival, achieving log 8 CFU mL−1 viability in both environments, a marked improvement over the uncoated variant. The study emphasizes the importance of microencapsulation, particularly by sodium alginate and chitosan, as a viable strategy to improve the survival and delivery of probiotics through the digestive system. By improving the stability and survivability of probiotics, microencapsulation promises to expand the use of synbiotics in various foods, contributing to the development of functional foods with health-promoting properties.

Three-dimensional cell culture-derived extracellular vesicles loaded alginate/hyaluronic acid composite scaffold as an optimal therapy for cartilage defect regeneration.

Osteoarthritis (OA) is a chronic musculoskeletal disease characterized by joint inflammation and progressive degeneration of articular cartilage. Currently a definitive cure for OA remains to be a challenge due to the very low self-repair capacity of cartilage, thus development of more effective therapies is needed for cartilage repair. Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) have shown great potential as therapeutic agents for stimulating regeneration of articular cartilage. However, a standardized protocol is still lacking for manufacturing of highly active EVs for clinical applications. This study aimed to investigate the efficient production of highly active EVs by 3-dimensional (3D) MSC culture, verify the reparative efficacy of EVs on cartilage defect and elucidate the repair mechanisms. Umbilical cord MSCs were embedded in alginate to form MSC spheroids for 3D culture in human platelet lysate (hPL)-containing medium, which produced 3D culture-derived EVs (3D-EVs) with a significantly improved yield. The 3D-EVs expressed higher level of VEGF, and appeared superior to 2D monolayer MSC culture-derived EVs (2D-EVs) to improve migration and proliferation in MSCs and inflammatory chondrocytes, and to suppress expression of cartilage-degrading factors. Importantly, the 3D-EVs and sodium alginate (SA)-hyaluronic acid (HA) composite hydrogel (3D-EVs/SA-HA) demonstrated significantly improved therapeutic efficacy than 2D-EVs/ SA-HA hydrogel for repair of cartilage defect in vivo. The underlying mechanisms are associated with the concomitant upregulation of type II collagen and cartilage synthesis and downregulation of MMP13 in cartilage tissues. Collectively, these data showed that highly active MSC EVs could be efficiently manufactured by 3D cell culture with hPL-containing medium, and these EVs were superior to 2D-EVs for the repair of articular cartilage defect.

Form-Factor Control of Alginate Aerogels Via Thixotropic Sols: From Monoliths to Fibers to Films.

Producing homogeneous alginate aerogel monoliths is challenging due to the uncontrollably fast gelation of sodium alginate (NaALG) solutions, which is typically induced with metal ions. This issue is overcome by decoupling molding from gelation. Aqueous NaALG solutions are first converted into thixotropic liquids via in situ acidification with acetic acid (AcOH) generated gradually through the hydrolysis of acetic anhydride (Ac2O), thus, providing time for casting in molds. The resulting solid-like thixotropic liquids are rigidized into wet gels conforming to the molds by a membraneless dialysis process via nonsolvent-induced phase separation, treatment with strong acids (HCl), or aqueous metal ion solutions (Ca2+, Cu2+, Fe3+, Ni2+, Ag+, Au3+). The thixotropic nature of the NaALG/Ac2O mixtures enables extrusion into fibers or spreading into films, followed by rigidization using the same methods. Wet gels in monolithic, fibrous, or film form were dried into aerogels with supercritical fluid (SCF) CO2. All aerogels were characterized by SEM, N2-sorption porosimetry, IR spectroscopy, solid-state CP MAS 13C NMR, and elemental analysis. Oscillatory rheology tracked the transition of NaALG to thixotropic liquids during Ac2O and AcOH titrations run in parallel. Thixotropic liquids from both titrations were rigidized with the nonsolvent-induced phase separation method and were processed into aerogels establishing that AcOH from the hydrolysis of Ac2O converts up to ∼30% mol/mol of NaALG to alginic acid (ALGH). Conversion of the remaining NaALG in thixotropic liquids to ALGH (>95% mol/mol) requires a strong acid (HCl), while rigidization with metal ions just replaces residual Na. Dynamic mechanical analysis (DMA) showed nearly identical storage moduli (E') for wet gels and aerogels, confirming that the solid network is formed during the rigidization step and is unaffected by subsequent processing. Notably, elemental analysis, porosimetry, and DMA data indicated that gels rigidized with Fe3+ included a secondary network, which, based on literature Mössbauer reports, is assigned to sol-gel-derived iron oxide.

In situ swelling of low-friction, high load-bearing self-bending bilayer hydrogels inspired by articular cartilage

The articular cartilage is characterized by its gradient hierarchical structure, which exhibits excellent lubrication and robust load-bearing properties. However, its inherent difficulty in self-repair after damage presents numerous formidable challenges for cartilage repair. Inspired by the unique structure of articular cartilage, a biomimetic bilayer hydrogel composed of PAM (polyacrylamide) and PAM/SA (sodium alginate) is prepared using a two-stepin-situswelling method. The bilayer hydrogel demonstrates exceptional structural stability due to the interlayerin-situchemical cross-linking. Compared to monolayer hydrogels, the PAM-PAM/SA bilayer hydrogel demonstrates superior mechanical attributes, exhibiting a compressive strength of 1 MPa and a compressive modulus of 0.22 MPa. Furthermore, exploration of the tribological performance of the PAM-PAM/SA bilayer hydrogel have revealed its low-friction performance under high loads, with a coefficient of friction as low as 0.032. Finally, leveraging the differential swelling properties between the distinct layers of the PAM-PAM/SA bilayer hydrogel, a self-bending biomimetic cartilage capable of conforming to complex joint surfaces is fabricated. This highly lubricating, mechanically robust, and conformal biomimetic cartilage provides an effective means for addressing cartilage defects and joint diseases.

Effectiveness assessment of the bifidobacteria encapsulation when enriching juice-containing beverages with probiotics

Beverages are among the most popular types of products that attract attention of researchers for enrichment with functional ingredients. The introduction of probiotics into the food matrix can increase the usefulness of food products, including beverages. However, probiotics are extremely sensitive to extreme environmental conditions, which significantly limits their ability to survive in food. The aim of the research is to establish an effect of encapsulation on the preservation of bifidobacteria in an enriched juice-containing beverage. Capsules from sodium alginate were used to protect probiotic microorganisms (bifidobacteria of six strains in the symbiotic starter) from unfavorable conditions of the environment of the food system and the gastrointestinal tract. The capsules were obtained by the drip method. The stability of the capsules was determined under different conditions. Their solubility in water and at pH values typical for the stomach (1.1–1.6), small intestine (7.8–8.2), and large intestine (8.0–8.5) were studied. The tests were carried out upon keeping in buffer solutions for 15 and 30 min. In addition, the stability of the capsules in apple juice with a pH of 3.82 when stored at 4±1°C for 7, 14, 21, and 28 days was assessed. Capsule losses during heat treatment were analyzed. The amount of bifidobacteria extracted from the capsules after mechanical destruction with their subsequent inoculation on the GMK1 medium was also monitored during juice storage. The results of the studies showed that the greatest destructive effect was observed in an acidic environment typical for the stomach, where losses amounted to 47.4% after 30 min. Capsule losses at pH values typical for different parts of the intestine ranged from 25.3 to 30.9%. The selected food system, apple juice, turned out to be a less aggressive environment for the capsules, in which the destruction of capsules was 8.7% after 28 days of storage. Capsule losses under the selected juice pasteurization modes ranged from 60.17% during processing for 10 minutes at 85°C to 67.42% during juice processing for 30 minutes at 98°C. The differences were statistically significant (p≤0.05). Thus, using the obtained data, it is possible to predict the total loss of capsules and probiotic microorganisms during the digestion and storage of the product and inoculate the required amount to impart probiotic properties to the product. The research has development prospects taking into account the possibility of varying the taste and aroma properties of both the food system and the capsules.

Advances in Spray-Drying and Freeze-Drying Technologies for the Microencapsulation of Instant Tea and Herbal Powders: The Role of Wall Materials

The microencapsulation of tea and herbal extracts is gaining considerable attention in the food industry, particularly in the production of instant powders. This review examines the application of spray-drying and freeze-drying technologies for the encapsulation of bioactive compounds, focusing on the role of wall materials. Over the past two decades, carbohydrate-based (e.g., maltodextrin), gum-based (e.g., gum Arabic), and protein-based (e.g., whey protein isolate) materials have been widely used due to their impact on sensory properties, stability, protection of bioactive compounds, and other critical attributes of encapsulated products. Despite their widespread use, these materials have distinct advantages and limitations, such as cost, availability, and compatibility with different extracts. This review provides a comprehensive analysis of their physical and chemical properties, examines alternative and emerging wall materials (e.g., beta-cyclodextrin, sodium alginate, and inulin), and highlights the potential of combining different materials to optimise encapsulation outcomes. It also identifies current research gaps and future directions to improve the efficacy and quality of encapsulated tea and herbal powders.

Adsorptive removal of nickel from waste water using synthesized sodium alginate encapsulated magnetic graphene oxide nanoadsorbent from Strychnous Potatorum seeds

The present study investigated the synthesis of sodium alginate encapsulated magnetic graphene oxide (SAMGO) beads from Strychnous Potatorum seeds. The synthesized SAMGO beads were investigated for adsorptive removal of nickel from aqueous solution. The synthesized SAMGO beads were characterized for surface morphology, functional groups, magnetic property and phase identification using SEM, FT-IR, VSM and XRD analysis. The optimization process involving the SAMGO beads for adsorptive removal of nickel resulted in maximum removal rate under the conditions of contact time – 15 min, SAMGO bead dose – 10 mg/50 mL of solution, nickel ion concentration – 50 mg/L, pH-9 and temperature of 30 °C. Adsorption of nickel onto SAMGO beads was well studied by pseudo-second-order kinetic studies. Also, the adsorption equilibrium study was well fitted towards Freundlich isotherm ( R2 = 0.99). The findings from the regeneration studies demonstrated that the selected desorbing agents, 0.5 M HCl and 0.5 M EDTA were well-suited for desorption. After five experimental cycles, the desorption efficiency decreased by only 10.93% and 7.76% using 0.5 M HCl and 0.5 M EDTA, respectively indicating that the SAMGO beads for reusability. The synthesized SAMGO beads have shown potential to reuse, nontoxic green adsorbent with maximum removal rate.

Sodium alginate coated ferritin as ACE inhibitory peptide carrier: Prolonged release property and enhanced transepithelial transport

Sodium alginate coated ferritin as ACE inhibitory peptide carrier: Prolonged release property and enhanced transepithelial transport

Cardiac repair using regenerating neonatal heart tissue-derived extracellular vesicles

Neonatal mammalian hearts are capable of regenerating by inducing cardiomyocyte proliferation after injury. However, this regenerative capability in adult mammalian hearts almost disappears. Extracellular vesicles (EVs) have been shown to play vital cardioprotective roles in heart repair. Here, we report that EVs from regenerating neonatal heart tissues, after apical resection surgery (AR-Neo-EVs), exhibit stronger pro-proliferative, anti-apoptotic, and pro-angiogenesis activities than EVs from neonatal mouse cardiac tissues (Neo-EVs), effects which are absent in adult mouse heart-derived EVs (Adu-EVs). Proteomic analysis reveals the expression of Wdr75 protein, a regulator of p53, is higher in AR-Neo-EVs than in Neo-EVs. It is shown the regenerative potential of AR-Neo-EVs is abrogated when Wdr75 is knocked down. We further show that delivery of AR-Neo-EVs by sodium alginate hydrogel microspheres is an effective treatment in myocardial infraction. This work shows the potential of using EVs from regenerating tissue to trigger protective and regenerative mechanisms.

Highly Specific and Sensitive SERS Detection of Putrescine Using Au Nanobowls@Cu-MOF Embedded in a Hydrogel Nanoreactor.

Putrescine is of concern due to its toxicity and applications in monitoring food spoilage and water quality. However, it is difficult to realize highly selective and sensitive detection of putrescine with interferences from other biogenetic amines with similar molecular structures. In this work, Au nanobowls modified by Cu-MOF (core-shell Au bowl@Cu MOF) together with o-phthalaldehyde (OPA) are embedded into sodium alginate hydrogel to construct a unique SERS substrate (OPA-Au bowl@Cu MOF/hydrogel) for sensing of putrescine. In the confined space of porous hydrogel, the Schiff base reaction between OPA and putrescine resulted in the product of N, N-dibenzylidene-n-butylenediamine (OPA-Putrescine), which is easily captured by Cu-MOF via copper-nitrogen coordination and then detected thanks to the high SERS activity of Au nanobowls and the large Raman scattering cross-section of OPA-Putrescine. The above reaction contributed to a high selectivity to greatly suppress the interferences from many amino group-containing molecules. The limit of detection (LOD) of gaseous and liquid putrescine is 1.2 × 10-9 and 6.3 × 10-10molL-1, respectively. Further, the application potential of this SERS-sensor in food and environmental fields are demonstrated by the successful detection of putrescine in salmon and seawater samples.

Ultrasound-Assisted Extraction of Phenolic Compounds from Tricosanthes cucumerina Leaves: Microencapsulation and Characterization

This study utilized the ultrasound-assisted extraction method to obtain an extract rich in phenolic compounds from the leaves of Tricosanthes cucumerina. The optimization of the experimental design identified the optimal extraction conditions: a temperature of 40 °C, a duration of 6.25 min, and an amplitude of 40%. Under these conditions, the extraction yielded the highest levels of phenolic compounds, measuring 262.54 mg of GAE (gallic acid equivalent) per gram. Further analysis of these extracts using electrospray ionization mass spectrometry (ESI-MS) demonstrated that ultrasound extraction increased the availability of bioactive compounds, such as p-coumaric acid, ferulic acid, and caffeic acid. The resulting extract was microencapsulated with sodium alginate as the wall material and then lyophilized to enhance the shelf life and stability of the phenolic compounds. The thermogravimetric analysis confirmed that the microcapsules exhibited thermal stability, retaining their properties at temperatures up to 250 °C. Additionally, Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analyses corroborated the effectiveness of the encapsulation process. Consequently, the ultrasound-assisted extraction of T. cucumerina leaves is a promising alternative for incorporating bioactive compounds into food products, nutraceuticals, and cosmetics, thus benefiting consumers.

Enhancing Biodegradable Packaging: The Role of Tea Polyphenols in Soybean Oil Body Emulsion Films

To address the increasingly diverse demands for biodegradable packaging materials, such as for their physical properties and antioxidant properties, this study incorporated tea polyphenols (TPs) into soybean oil body emulsions (SOBs) and added a certain proportion of sodium alginate (SA) and octenyl succinic starch sodium (SSOS) to prepare a biodegradable soybean oil body–tea polyphenol (ST) emulsion film. The study systematically evaluated the effects of different concentrations of TP (0–6 wt.%) on the structure, physicochemical properties, antioxidant activity, and antibacterial activity of ST films. The results showed that the physical properties, such as tensile strength and elongation at break, of the films increased significantly with the addition of TP, and the antioxidant and antibacterial activity also increased with the increase in TP concentration. When TP concentration was 2.5 wt.%, the barrier properties of the film (ST-2.5) significantly improved (p < 0.05), while water content and water solubility decreased. The Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis results showed that the structure of ST films became tighter at this point. The addition of TP also affected the sensory properties of ST films, such as with an increase in the opacity of the film. Compared with the control, the light transmittance of ST-6.0 decreased by 23.68% at a wavelength of 600 nm, indicating a significant reduction in film transparency. Moreover, the biodegradability test showed that ST films have good degradability. Therefore, the ST film, as a functional edible film, has broad application prospects in the food packaging industry.

The influence of sodium alginate on kaolinite flocculation in presence of metal ions: guidance for green processing

In this study, the responsiveness of Na+, Mg2+, Ca2+ and Al3+ to sodium alginate (SA) and their influence on kaolinite dispersion/flocculation behavior were investigated through rheology and turbidity tests. The effects of metal ions on the interaction between SA and kaolinite were analyzed by zeta potential, fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT). The results showed that Na+ and Mg2+ resulted in a decreasing of the viscosity and modulus of SA solution for they have the electrostatic shielding effect on SA. Ca2+ and Al3+ significantly increased the viscosity and modulus of SA solution because Ca2+ and Al3+ not only have the electrostatic shielding effect on SA but also could form the different network structure complexes. The order of the responsiveness of metal ions and SA sorted by intensity level was: Al3+> Ca2+>Mg2+> Na+. SA has a dispersion effect on kaolinite particles under the background of Na+ and Mg2+, and SA has a flocculation effect on kaolinite particles in the presence of Ca2+ and Al3+. The flocculation efficiency of SA on kaolinite suspension containing Al3+ was much higher than that of SA on kaolinite suspension in the presence of Ca2+. Zeta potential and FTIR results showed that SA could be adsorbed on the kaolinite surface through electrostatic force and hydrogen bond in the presence of Na+ and Mg2+. Microscope observation, XPS and DFT results showed SA could not only form chemical adsorption with Ca2+/Al3+ on the kaolinite surface but also be cross-linked with Ca2+/Al3+ to form a network structure, which could sweep and trap kaolinite particles in suspension. This work has strategic significance for the responsiveness of natural polysaccharide to metal ions and their application in environmental protection of mine wastewater, as well as the clean and circular utilization of water.

Preparation of sodium alginate / quaternary ammonium-functionalized chitosan adsorbents: For the removal of high-molecular-weight invert sugar alkaline degradation products.

The composite adsorbent consisting of sodium alginate (SA) and quaternary ammonium-functionalized chitosan (QACS) was prepared using the calcium slow-release method to remove high-molecular-weight invert sugar alkaline degradation products (HISADPs) from the beet juice. The SA/QACS composite adsorbent has a honeycomb porous structure. Comparing the single-component QACS dispersion and SA adsorbent, the incorporation of SA increased the storage/elastic modulus (G') and loss/viscous modulus (G'') of the SA/QACS composite hydrogels, while the incorporation of QACS enhanced the adsorption capacity of the SA/QACS composite adsorbents. Specifically, when 5 % QACS and 2 % SA were added, both G' and G" of the SA/QACS adsorbent were approximately 100 times greater than those corresponding to the QACS dispersion. Concurrently, its maximum adsorption capacity attained 164.5 mg/g, which was superior to that of the SA adsorbent. The adsorption isotherms and adsorption kinetics further demonstrated that the Langmuir model and the pseudo-second-order (PSO) model were congruent with the adsorption data of the SA/QACS composite adsorbent concerning HISADPs. Overall, these findings highlight the potential of the SA/QACS adsorbent as an effective adsorbent for the removal of HISADPs from beet juice.