Zinc Alginate Research Articles

Flame retardant polyurethane foam prepared from compatible blends of ammonium ligninsulfonate-based and zinc alginate

Abstract Zinc alginate (ZnAlg) was prepared and subsequently employed to modify ammonium ligninsulfonate-based polyurethane foams (PUFs). A range of analytical techniques, including thermogravimetry, integral programmed decomposition temperature, activation energy, smoke density, cone calorimetry and scanning electron microscopy, were employed to characterise the modified PUFs. The results demonstrated that the PUFA15Z5 (15 % ammonium lignin sulfonate and 5 g ZnAlg) with the lowest mass loss exhibited the second-highest sample decomposition temperature (T50 %), second-highest peak temperature (TMAX2), IPDT and activation energy. Furthermore, the PUFA15Z5 sample exhibited the smallest smoke density (23.11) and the highest light transmittance (67.11 %). The peak heat release rate, total heat release, smoke production rate, total smoke release and four fire risk assessment indicators of the PUFA15Z5 were the lowest, while its carbon residue was the densest. The results demonstrated that the PUFA15Z5 exhibited the most favourable thermal stability, flame retardant properties and the lowest smoke toxicity. These findings provided a valuable reference for subsequent biomass-based flame retardant modified polyurethane foams (PUFs).

Production and simulated digestion of high-load beads containing Schizochytrium oil encapsulated utilizing prilling technique

The oil from the heterotroph Schizochytrium is a rich source of n-3 PUFA, particularly DHA, and therefore highly susceptible to oxidation. The present work reports the first application of coaxial prilling for the protection of this oil through microencapsulation. After process optimization, core-shell microparticles were produced with calcium or zinc alginate at different concentrations. Encapsulates were analyzed in their tocopherol and PUFA content. Prilling lowered the earlier but had little effect on the latter. Microcapsules coated with calcium alginate (1 % and 1.75 %) had higher oil load and encapsulation efficiency and were therefore submitted to in vitro digestion together with a simulated meal. Digesta were also analyzed with HPLC-qTOF and 1H NMR and compared to undigested encapsulates. While 1 % calcium shell granted lower oil release and protection from oxidation in the simulated gastrointestinal tract, chromatographic and spectroscopic data of digesta showed higher presence of lipid digestion products.

Ternary Heterostructure Membranes with Two-Dimensional Tunable Channels for Highly Selective Ion Separation.

Selective ion separation from brines is pivotal for attaining high-purity lithium, a critical nonrenewable resource. Conventional methods encounter substantial challenges, driving the quest for streamlined, efficient, and swift approaches. Here, we present a graphene oxide (GO)-based ternary heterostructure membrane with a unique design. By utilizing Zn2+-induced confinement synthesis in a two-dimensional (2D) space, we incorporated two-dimensional zeolitic imidazolate framework-8 (ZIF-8) and zinc alginate (ZA) polymers precisely within layers of the GO membrane, creating tunable interlayer channels with a ternary heterostructure. The pivotal design lies in ion insertion into the two-dimensional (2D) membrane layers, achieving meticulous modulation of layer spacing based on ion hydration radius. Notably, the ensuing layer spacing within the hybrid ionic intercalation membrane occupies an intermediary realm, positioned astutely between small-sized hydrated ionic intercalation membrane spacing and their more extensive counterparts. This deliberate configuration accelerates the swift passage of diminutive hydrated ions while simultaneously impeding the movement of bulkier ions within the brine medium. The outcome is remarkable selectivity, demonstrated by the partitioning of K+/Li+ = 20.9, Na+/K+ = 31.2, and Li+/Mg2+ = 9.5 ion pairs. The ZIF-8/GO heterostructure significantly contributes to the selectivity, while the mechanical robustness and stability, improved by the ZA/GO heterostructure, further support its practical applicability. This report reports an advanced membrane design, offering promising prospects for lithium extraction and various ion separation processes.

Hydrogel electrolyte membrane with regulated pore effect to stabilize zinc anode in aqueous zinc-ion batteries

The unregulated dendrite growth and deleterious derivative reactions at Zn anodes lie in the path of research and industrialization of aqueous Zn-ion batteries (AZBs). The pore of the separator is a natural sieve for ion diffusion, but the high energy barrier for transmembrane transport can cause the “bridging” effect of ion congestion at the pore entrance, and induce the incubation of dendrites instead. In this work, a continuous, stable and fast ion transport channel is constructed by in-situ guided cross-linking of zinc alginate (ZA) hydrogels through the porous membrane to conquer the negative pore effect. The homogeneity and continuity of the channel structure, as well as the high ionic conductivity and zincophilicity of the ZA, can homogenize the electric field and reduce the energy barrier for ion transport. In battery systems, the physical ion shunting effect of a homogeneous pore structure, combined with the chemical/electrochemical effects of ZA guiding the diffusion of Zn2+ and binding free water, combat zinc dendrites and interfacial side reactions. The novel electrolyte membrane enables a highly reversible Zn plating/stripping to stabilize the Zn anode. This work provides illuminating insights into the regulation and application of pore effects in porous electrolyte membranes in metal-based batteries.

Self‐Adapting and Self‐Healing Hydrogel Interface with Fast Zn2+ Transport Kinetics for Highly Reversible Zn Anodes

AbstractConstruction of polymer‐based artificial solid‐electrolyte interphase films on Zn metal anode holds great potential in the suppression of both dendrite growth and side reaction in rechargeable aqueous Zn‐ion batteries. However, the traditional polymer films suffer from the critical issues of sluggish Zn2+ transport kinetics and rigid interface. Herein, zinc alginate (ZA) hydrogel is designed and prepared as a dynamic interface and Zn2+ redistributor on Zn anode via in situ cross‐linking reaction. The zincophilic and negatively charged carboxyl groups of ZA promote the transport of Zn2+ ions along a “Z‐type” pathway, the repulsion of free SO42‐ anions, and the desolvation of Zn2+ ions, consequently leading to the homogeneous deposition of Zn and the effective suppression of side reaction. Additionally, the dynamic flexibility of ZA hydrogel endows the Zn anode with self‐adapting interface to accommodate the volume variation and repair the possible ruptures, thereby guaranteeing the long‐term cycling stability. Assisted by the ZA layer, the Zn anode achieves a prolonged lifespan over 2200 h without the formation of Zn dendrites and by‐products. Outstanding cycling stability is also demonstrated for the Zn anode when coupled with MnO2 cathode, further demonstrating its prospects for practical application.

Low-Cost Zinc–Alginate-Based Hydrogel–Polymer Electrolytes for Dendrite-Free Zinc-Ion Batteries with High Performances and Prolonged Lifetimes

Aqueous zinc-ion batteries (ZIBs) represent an attractive choice for energy storage. However, ZIBs suffer from dendrite growth and an irreversible consumption of Zn metal, leading to capacity degradation and a low lifetime. In this work, a zinc-alginate (ZA) hydrogel-polymer electrolyte (HGPE) with a non-porous structure was prepared via the solution-casting method and ion displacement reaction. The resulting ZA-based HGPE exhibits a high ionic conductivity (1.24 mS cm-1 at room temperature), excellent mechanical properties (28 MPa), good thermal and electrochemical stability, and an outstanding zinc ion transference number (0.59). The ZA-based HGPE with dense structure is proven to benefit the prevention of the uneven distribution of ion current and facilitates the reduction of excessive interfacial resistance within the battery. In addition, it greatly promotes the uniform deposition of zinc ions on the electrode, thereby inhibiting the growth of zinc dendrites. The corresponding zinc symmetric battery with ZA-based HGPE can be cycled stably for 800 h at a current density of 1 mA cm-2, demonstrating the stable and reversible zinc plating/stripping behaviors on the electrode surfaces. Furthermore, the quasi-solid-state ZIB with zinc, ZA-based HGPE, and Ca0.24V2O5 (CVO) as the anode, electrolyte, and cathode materials, respectively, show a stable cyclic performance for 600 cycles at a large current density of 3 C (1 C = 400 mA g-1), in which the capacity retention rate is 88.7%. This research provides a new strategy for promoting the application of the aqueous ZIBs with high performance and environmental benignity.

Redistributing zinc-ion flux by constructing a hybrid conductor interface for dendrite-free zinc anode

Rechargeable aqueous zinc-metal batteries have attracted soaring attention as alternative to conventional lithium-ion batteries for energy storage systems due to the high safety, low cost, and environmental benignancy. However, the spontaneous side reaction and dendrite growth lead to the poor electrochemical performance as well as serious safety issues. Herein, a multifunctional layer composed of zinc alginate (ZA) and vermiculite sheets (VS) is coating on zinc foil surface to simultaneously suppress the side reaction and dendrite growth. Unique Zn2+ channels built by ZA polymer and VS endow the ZAVS film with high zinc-ion transference number (tZn2+ = 0.81), which can both improve the migration of Zn2+ and redistribute the Zn2+ flux on the electrode surface. Consequently, dendrite growth is obviously inhibited. In addition, ZAVS film can serves as a buffer layer to isolate zinc anode from aqueous electrolyte, alleviating the zinc corrosion and hydrogen generation. Benefiting from the inhibition of dendrite growth and side reaction, superior electrochemical performance can be achieved as evidenced by the high Coulombic efficiency of 99.18% for 520 cycles, and ultra-long cycling stability over 1000 h with small voltage hysteresis. The construction of ZAVS artificial layer could be a promising strategy for advanced RAZMBs.

Zinc alginate hydrogels with embedded RL-QN15 peptide-loaded hollow polydopamine nanoparticles for diabetic wound healing therapy

Chronic wound healing remains a considerable clinical challenge worldwide. We previously identified a pro-regenerative agent, i.e., hollow dopamine nanoparticles (HPDA) loaded with potent pro-healing peptide RL-QN15 (HPDAlR), with significant skin wound healing activity. In the current study, in consideration of clinical application, we successfully prepared a new zinc alginate hydrogel embedded with HPDAlR (HPDAlR&ZA) to treat diabetic wounds. HPDAlR&ZA exhibited no obvious toxicity against keratinocytes, human umbilical vein endothelial cells (HUVECs), human skin fibroblasts (HSFs), and mice. HPDAlR&ZA significantly promoted keratinocyte, HUVEC, and HSF proliferation, as well as HUVEC migration and angiogenesis. HPDAlR&ZA also modulated the expression of cytokines from macrophages. Diabetic mouse full-thickness skin wound and diabetic patient in vitro skin wound models showed that HPDAlR&ZA resisted the inflammatory response by rapidly polarizing M1 macrophages to M2 macrophages, thereby reconstructing blood supply, increasing collagen deposition, and accelerating diabetic wound repair and skin regeneration. In summary, HPDAlR&ZA is a biodegradable hydrogel wound dressing and an efficient treatment strategy for diabetic wound repair, with strong anti-oxidant, anti-inflammatory, and pro-angiogenic features.

Zn2+ Cross-Linked Alginate Carrying Hollow Silica Nanoparticles Loaded with RL-QN15 Peptides Provides Promising Treatment for Chronic Skin Wounds.

Chronic and non-healing wounds pose a great challenge to clinical management and patients. Many studies have explored novel interventions against skin wounds, with bioactive peptides, nanoparticles, and hydrogels arousing considerable attention regarding their therapeutic potential. In this study, the prohealing peptide RL-QN15 was loaded into hollow silica nanoparticles (HSNs), with these HSN@RL-QN15 nanocomposites then combined with zinc alginate (ZA) gels to obtain HSN@RL-QN15/ZA hydrogel. The characteristics, biological properties, and safety profiles of the hydrogel composites were then evaluated. Results showed that the hydrogel had good porosity, hemocompatibility, biocompatibility, and broad-spectrum antimicrobial activity, with the slow release of loaded RL-QN15. Further analysis indicated that the hydrogel promoted skin cell proliferation and keratinocyte scratch repair, regulated angiogenesis, reduced inflammation, and accelerated re-epithelialization and granulation tissue formation, resulting in the rapid healing of both full-thickness skin wounds and methicillin-resistant Staphylococcus aureus biofilm-infected chronic wounds in mice. This peptide-based hydrogel provides a novel intervention for the treatment of chronic skin wounds and shows promise as a wound dressing in the field of tissue regeneration.

Kinetic and thermodynamic synergy of spongiform nanostructure and alien dopants enables promoted sodium-ion transfer for high-performance sodium storage

Chlorine-doped spongiform TiO 2 /C composite is synthesized by an NH 4 Cl-assisted annealing strategy with zinc alginate and commercial TiO 2 nanoparticles as precursors, demonstrating superior sodium-ion diffusion kinetics and reaction thermodynamics with well-designed spongiform structure and rational element doping. • A novel NH 4 Cl-assisted annealing strategy is developed to prepare ZATC-Cl. • The spongiform structure of ZATC-Cl results in fast sodium-ion diffusion kinetics. • Cl dopants in ZATC-Cl achieve preferable sodium-ion reaction thermodynamics. • ZATC-Cl delivers remarkable sodium storage performance. To address the bottlenecks of sluggish sodium-ion transfer processes, the electrode materials of sodium-ion battery (SIB) are always designed from the viewpoints of sodium-ion diffusion kinetics or reaction thermodynamics for high-performance sodium storage. Herein, starting with spongiform TiO 2 /C composite derived from zinc alginate, a NH 4 Cl-assisted annealing strategy is developed to prepare chlorine-doped spongiform TiO 2 /C composite (ZATC-Cl). Acting as the anode of SIBs, the obtained ZATC-Cl delivers excellent sodium storage performance with a high reversible capacity of 352.4 mAh g −1 at 50 mA g −1 , a superior rate capability of 246.8 mAh g −1 at 2 A g −1 and a considerable high-rate cycling performance of 248.5 mAh g −1 at 2 A g −1 for 1000 cycles. It is believed that the unique spongiform structure and ultra-small sized TiO 2 particles in ZATC-Cl can achieve fast sodium-ion insertion/extraction, realizing rapid sodium-ion diffusion kinetics. Moreover, as well evidenced by experiment results and theoretical calculations, the Cl dopants introduced in ZATC-Cl can provide more active sites for robust sodium-ion chemical adsorption, optimizing sodium-ion reaction thermodynamics. This study demonstrates an alternative approach to improve the sodium storage capability of TiO 2 anodes by the synergistically engineering the morphological and structural properties and manipulating the surface active sites, from both kinetic and thermodynamic viewpoints of sodium storage processes.

Evaluating Five Consolidants for Black-Dyed Māori Textile Artefacts

ABSTRACT This article reports testing of the efficacy of five consolidants (sodium alginate, zinc alginate, Paraloid® B-72, TRI-Funori™, Methocel® A4C) used by conservators for consolidation. The consolidants were tested for potential use on deteriorated black-dyed plant fibres, specifically paru-dyed muka (iron-tannate dyed fibre from harakeke; New Zealand flax, Phormium tenax), building on previous experimental work. Paru-dyed test fibres were pre-aged (light, with UV) to simulate museum artefacts, and then consolidated, after which their colour stability, strength retention, and acidity were measured. Consolidated test fibres were then artificially light-aged (UV-filtered) to test the stability of the consolidants over time (10 MLux hours; UV-filtered light), with colour stability, strength retention, and acidity re-measured after this ageing stage. A full factorial experimental design with four factors was used for testing: dye type, consolidant type, consolidant concentration, and accelerated light-ageing. Data were analysed using generalised linear models (GLM) coupled with analysis of variance (ANOVA) and simple effects procedures to test for interactions between factors and determine significant differences. Overall, this study found that using criteria of pH, strength, colour stability, and visual properties, that 0.5% w/v Methocel® A4C™ in H2O and TRI-Funori™ 0.5% w/v in H2O were recommended for further exploration for use on deteriorated paru-dyed muka.

Electrophoretic deposition of zinc alginate coatings on stainless steel for marine antifouling applications

Abstract The protection of steel against marine biofouling is usually achieved by the application of protective coatings. In this work, an antifouling coating based on alginate biopolymer was developed using the electrophoretic deposition method. Zinc cations have been incorporated into the material to obtain some anti-algae / bacteria properties and calcium cations have been included to contribute to its jellification. The coatings produces were characterized by XRD, SEM, EDX and XPS techniques: the microscopic coatings fully and uniformly covered the steel samples. Results of the biological assays have demonstrated the impact of the coating on marine bacteria and microalgae; the values are comparable to those obtained in bioassays using copper-based alginate coatings. The antifouling effect of the coatings was equivalent to the potency of a high-volume hydrogel effect. These low-cost biocompatible coatings can be attractive in a wide variety of marine applications.

Understanding consolidants on harakeke fibres using Raman microscopy: Implications for conservation

Abstract Many customary Māori textiles are produced from harakeke fibres (muka) which are extracted from New Zealand flax (Phormium tenax) and some are dyed with paru (black) iron-tannate dyes. These tannate-dyed textiles degrade via iron catalysed oxidation and acid catalysed hydrolysis. To mitigate this degradation, conservators can potentially use various types of natural and synthetic consolidants; however, there is a lack of systematic study of the interaction between muka and consolidants. As part of a larger research project investigating the efficacy of six consolidants for treatment of deteriorated black-dyed muka in Māori textiles, the penetration of different consolidants applied to muka was investigated. By using Raman microscopy combined with chemometrics, this study was able to aid in selection, and concentration of, consolidants for use in the larger project. Six different consolidants; sodium alginate, zinc alginate, Paraloid B-72™ (ethyl-methyl methacrylate), TRI-Funori™ (seaweed extract, polysaccharide), Klucel G™ (hydroxypropyl cellulose), and Methocel A4C™ (methylcellulose) were applied at three concentrations (0.5, 1.0, and 2.0% w/v) to muka. The consolidated samples were sectioned and analysed using Raman microscopy mapping with a 532 nm incident laser. Relative intensity levels of the signals from the fibres and the consolidants were used to generate maps of the chemical composition across the fibre. Univariate analysis (with unique band integrals) and multivariate analysis (true component analysis) of the chemical images was able to distinguish the penetration pattern of consolidants, Paraloid B-72™, TRI-Funori™, and Klucel G™ into the fibres. The analysis of Methocel A4C™ was not possible because the spectral characteristics were too similar between the two. Sodium and zinc alginate consolidated samples tended to burn and no useful data could be collected. The consolidants accumulated in the intercellular spaces/middle lamella of the fibre's morphological structure and did not appear to penetrate into the fibre cell walls. The results from the study demonstrated the usefulness of Raman microscopy for understanding the properties and behaviour of consolidants applied to important cultural materials.

Metal alginates for polyphenol delivery systems: Studies on crosslinking ions and easy-to-use patches for release of protective flavonoids in skin

Incorporation of bioactive natural compounds like polyphenols is an attractive approach for enhanced functionalities of biomaterials. In particular flavonoids have important pharmacological activities, and controlled release systems may be instrumental to realize the full potential of these phytochemicals.Alginate presents interesting attributes for dermal and other biomaterial applications, and studies were carried here to support the development of polyphenol-loaded alginate systems. Studies of capillary viscosity indicated that ionic medium is an effective strategy to modulate the polyelectrolyte effect and viscosity properties of alginates. On gelation, considerable differences were observed between alginate gels produced with Ca2+, Ba2+, Cu2+, Fe2+, Fe3+ and Zn2+ as crosslinkers, especially concerning shrinkage and morphological regularity. Stability assays with different polyphenols in the presence of alginate-gelling cations pointed to the choice of calcium, barium and zinc as safer crosslinkers. Alginate-based films loaded with epicatechin were prepared and the kinetics of release of the flavonoid investigated. The results with calcium, barium and zinc alginate matrices indicated that the release dynamics is dependent on film thicknesses, but also on the crosslinking metal used.On these grounds, an alginate-based system of convenient use was devised, so that flavonoids can be easily loaded at simple point-of-care conditions before dermal application. This epicatechin-loaded patch was tested on an ex-vivo skin model and demonstrated capacity to deliver therapeutically relevant concentrations on skin surface. Moreover, the flavonoid released was not modified and retained full antioxidant bioactivity. The alginate-based system proposed offers a multifunctional approach for flavonoid controllable delivery and protection of skin injured or under risk.

Alginate-Derived Porous Carbon Obtained by Nano-ZnO Hard Template-Induced ZnCl2-Activation Method for Enhanced Electrochemical Performance

Biomass-derived hierarchical porous carbons have attracted considerable attention due to their low cost, environmental friendliness and sustainability. However, the preparation of porous carbon with typically hierarchical pores is still challengeable. In this work, a facile and efficient strategy was proposed to obtain alginate-derived porous carbon by a combination of hard-template and chemical-activation technique. During the fabrication process the nano-ZnO particles displayed triple functions: (a) The nano-ZnO particles were behaved as the hard template to generate more pores. (b) ZnCl2 derived from the nano-ZnO particles acted as a cross-linking agent for obtaining zinc alginate (Zn-SA) hydrogel beads. (c) ZnCl2 was also employed as an activating agent to form micropores during the high-temperature carbonization process. As a subsequence, the obtained carbon exhibited well-developed hierarchical porous structure with high specific surface area of up to 2589 m2 g−1. Due to the high specific surface area, good electrical conductivity and synergistic effect among the typically hierarchical pores, the PC-ZnO-ZnCl2-650 exhibited a high specific capacitance of 316 F g−1 at the current density of 0.5 A g−1 and excellent cycling stability with capacitance retention of 94.4% at 5 A g−1 over 5000 cycles. This ingenious synthesis strategy can provide a new way for efficient preparation of hierarchical porous material.

A Novel Inherently Flame-Retardant Composite Based on Zinc Alginate/Nano-Cu2O.

A novel flame-retardant composite material based on zinc alginate (ZnAlg) and nano-cuprous oxide (Cu2O) was prepared through a simple, eco-friendly freeze-drying process and a sol-gel method. The composites were characterized and their combustion and flammability behavior were tested. The composites had high thermal stability and achieved nearly non-flammability with a limiting oxygen index (LOI) of 58. The results show remarkable improvement of flame-retardant properties in the ZnAlg/Cu2O composites, compared to ZnAlg. Furthermore, the pyrolysis behavior was determined by pyrolysis–gas chromatography–mass spectrometry (Py-GC-MS) and the flame-retardant mechanism was proposed based on the combined experimental results. The prepared composites show promising application prospects in building materials and the textile industry.

Graphene oxide in zinc alginate films: Antibacterial activity, cytotoxicity, zinc release, water sorption/diffusion, wettability and opacity.

Alginate is considered an exceptional biomaterial due to its hydrophilicity, biocompatibility, biodegradability, nontoxicity and low-cost in comparison with other biopolymers. We have recently demonstrated that the incorporation of 1% graphene oxide (GO) into alginate films crosslinked with Ca2+ cations provides antibacterial activity against Staphylococcus aureus and methicillin-resistant Staphylococcus epidermidis, and no cytotoxicity for human keratinocyte HaCaT cells. However, many other reports in literature have shown controversial results about the toxicity of GO demanding further investigation. Furthermore, the synergic effect of GO with other divalent cations with intrinsic antibacterial and cytotoxic activity such as Zn2+ has not been explored yet. Thus, here, two commercially available sodium alginates were characterised and utilized in the synthesis of zinc alginate films with GO following the same chemical route reported for the calcium alginate/GO composites. The results of this study showed that zinc release, water sorption/diffusion and wettability depended significantly on the type of alginate utilized. Furthermore, Zn2+ and GO produced alginate films with increased water diffusion, wettability and opacity. However, neither the combination of GO with Zn2+ nor the use of different types of sodium alginates modified the antibacterial activity and cytotoxicity of the zinc alginates against these Gram-positive pathogens and human cells respectively.

Development of alginate hydrogels active against adhesion of microalgae

Microorganisms have the ability to settle on nearly all man-made surfaces in contact with seawater and subsequently to form biofilm. Biofilms control and removal is necessary in the sectors of maritime transport, energy… In this work, we present the development of new pure calcium, zinc or copper alginate, but also mixed Ca/Cu and Ca/Zn alginate hydrogels. These materials have been evaluated for their potential inhibition of adhesion of two key biofilm-forming microalgae (Halamphora coffeaeformis and Cylindrotheca closterium). All the tested materials have presented high adhesion inhibition (about 80%). Copper-base materials present a high toxicity against H. coffeaeformis. Pure zinc alginate is also toxic for this strain. However, the addition of calcium in zinc alginate leads to the toxicity reduction. The toxicity of these materials differs according to the strains. Consequently, mixed zinc/calcium alginate are efficient at inhibiting microalgal adhesion with a low level of cells toxicity. These alginate hydrogels are promising materials because they are efficient, cheap, easy to develop and eco-friendly.

Efficiency of Zinc and Calcium Ion Crosslinking in Alginate-coated Nitrogen Fertilizer

The work evaluated the difference of nitrogen retention in sodium alginate hydrogel microspheres with 50% of nitrogen, to allow the production of controlled release fertilizers. The crosslinking with the calcium and zinc ions occurs in a differentiated way, and it is emphasized that zinc binds more slowly and covalently. After the spheres were elaborated, a leaching test was performed to simulate the release of nitrogen by soil moisture. In this case, the zinc nitrate-reticulated beads showed a lower loss of the nitrogen content compared to calcium, with values of 6.7129% of nitrogen for zinc nitrate, corresponding to about 50% of the initial value, and 43.6345 % of nitrogen for calcium chloride corresponding to about 90% of the initial value. The characterization of the samples was performed by fourier transformed infrared (FTIR) analysis, and characteristic calcium and zinc alginate compounds were observed, in the same way as the connections caused by nitrogen. It can be defined that the zinc-crosslinked alginate obtained a lower swelling capacity and higher retention of nitrogen than with calcium chloride, being an alternative for the preparation of slow-release fertilizer. DOI: http://dx.doi.org/10.17807/orbital.v10i3.1103

Spray-Drying-Assisted Layer-by-Layer Assembly of Alginate, 3-Aminopropyltriethoxysilane, and Magnesium Hydroxide Flame Retardant and Its Catalytic Graphitization in Ethylene-Vinyl Acetate Resin.

Alginates (nickel alginate, NiA; copper alginate, CuA; zinc alginate, ZnA) and 3-aminopropyltriethoxysilane (APTES) were alternately deposited on a magnesium hydroxide (MH) surface by the spray-drying-assisted layer-by-layer assembly technique, fabricating some efficient and environmentally benign flame retardants (M-FR, including Ni-FR, Cu-FR, and Zn-FR). The morphology, chemical compositions, and structures of M-FR were investigated. With 50 wt % loading, compared with EVA28+MH, the peak heat release rate, smoke production rate, and CO production rate of EVA28+Ni-FR decreased by 50.78%, 61.76%, and 66.67%, respectively. The metals or metal oxide nanoparticles arising from alginates could catalyze the pyrolysis intermediates of EVA into graphene and amorphous carbon, which could bind the inorganic compounds (the decomposition products of MH and APTES) together and form some more protective barriers. For each M-FR, the flame retardant and smoke suppression efficiency were different, which were caused by the diverse carbonization and graphitization behaviors of three alginates. ZnA generated some ZnO aggregations and could not catalyze the graphitization of intermediates. For CuA, the catalytic graphitization was limited by the tightly binding graphene layer. As for NiA, the configuration of the Ni atom could not provide strong binding of Ni substrate and carbon. The liquid-like Ni nanoparticles could restructure and get out from firm graphene shells, so the catalytic graphitization of NiA was efficient and sustainable. This work displayed the catalytic graphitization mechanism of alginates while exploring a simple and novel strategy for fabricating efficient green flame retardants.