Facile and cost-effective preparation of PVA/modified calcium carbonate nanocomposites via ultrasonic irradiation: Application in adsorption of heavy metal and oxygen permeation property

Development of a multifunctional active food packaging membrane based on electrospun polyvinyl alcohol/chitosan for preservation of fruits

To mitigate environmental impacts in food preservation, the development of a multifunctional membrane for packaging is of importance. In this study, we have successfully fabricated a nanofibrous membrane using an eco-friendly electrospinning technique, comprising polyvinyl alcohol (PVA), chitosan (CS), and tannic acid (TA). The resulting nanofibrous membranes were crosslinked with glutaraldehyde (GA) and surface modified with ZnO. Our findings demonstrate that the crosslinking process enhances water resistance, reduces water vapor permeability, improves tensile strength (from 3 to 18 MPa), and enhances thermal stability (increasing decomposition temperature from 225 °C to 310 °C). Furthermore, the incorporation of TA and ZnO provides antioxidant properties to the membrane, effectively preventing food decomposition caused by UV-induced oxidation. Additionally, CS, TA, and ZnO synergistically exhibit a remarkable antibacterial effect with a bacteriostasis rate exceeding 99.9 %. The strawberry fresh-keeping experiment further confirms that our developed membrane significantly extends shelf life by up to 6 days. Moreover, cytotoxicity assays confirm the non-toxic nature of these membranes. The innovative significance of this study lies in proposing a robust GA-PVA/CS/TA@ZnO nanofibrous membrane with excellent mechanical properties, biocompatibility, and multiple functionalities including antibacterial, anti-ultraviolet, and anti-oxidation capabilities. It has tremendous potential for applications in active food packaging materials.

High performance polyvinyl alcohol/lignin fibers with excellent mechanical and water resistance properties

To address the shortcoming of Polyvinyl alcohol (PVA) fibers for food or medical packaging materials including low mechanical strength and poor water resistance, lignin (LN) was used as raw material, acetone/H2O as solvent to self-assemble into lignin nanoparticles (LNP) by adverse solvent precipitation approach, and then PVA/LNP composite fibers with different LNP contents were fabricated successfully by wet and dry spinning. Herein, vast hydrophilic hydroxyl groups in PVA decreased owing to the hydrogen bond between LN and PVA, Especially, with only 0.5 wt% loading of LNP into the PVA/LNP fibers, the diameter was 94.4 dtex, tensile strength was 10.1 cN/dtex (1279.8 MPa), initial modulus was 94.7 cN/dtex (12.0 GPa), the crystallinity was 56.7 %, the orientation was 97.1 %, and water contact angle was 103.1°. Compared with pure PVA fibers, the tensile strength of PVA/LNP-0.5 fibers was increased by 44.2 % and the contact angle was increased 37°. This work provides novel insights into obtaining lignin-reinforced PVA composite fibers with strong mechanical properties and excellent water resistance properties, indicating the potential of the PVA/LNP fibers for food or medical packaging application.

Application and mechanism of carbonate material in the treatment of heavy metal pollution: a review

Among the many heavy metal pollution treatment agents, carbonate materials show strong flexibility and versatility by virtue of their high adsorption capacity for heavy metals and the characteristics of multiple and simple modification methods. It shows good potential for development. This review summarizes the application of carbonate materials in the treatment of heavy metal pollution according to the research of other scholars. It mainly relates to the application of surface-modified, activated, and nano-sized carbonate materials in the treatment of heavy metal pollution in water. Natural carbonate minerals and composite carbonate minerals solidify and stabilize heavy metals in soil. Solidification of heavy metals in hazardous waste solids is by MICP. There are four aspects of calcium carbonate oligomers curing heavy metals in fly ash from waste incineration. The mechanism of treating heavy metals by carbonate in different media was discussed. However, in the complex environment where multiple types of pollutants coexist, questions on how to maintain the efficient processing capacity of carbonate materials and how to use MICP to integrate heavy metal fixation and seepage prevention in solid waste base under complex and changeable natural environment deserve our further consideration. In addition, the use of carbonate materials for the purification of trace radioactive wastewater and the safe treatment of trace radioactive solid waste are also worthy of further exploration.

Lignin-xylan nanospheres prepared by green and quick method from lignocellulose and used as additive in PVA films

Lignin, as an amorphous three-dimensional aromatic polymer, was able to self-assemble into lignin nanoparticles (LNPs) to realize valorization of lignin. Here, lignin-xylan extractives were extracted from grape seed (GS) and poplar by acidic THF at room temperature, and effectively produced lignin-xylan nanospheres via spin evaporation. The morphology and chemical properties of nanospheres were determined by its natural origins, consequently influencing its application. For the lignin-xylan extractive from grape seed, the lignin was composed of guaiacyl (G) and p-hydroxylphenyl (H) units and the hollowed nanospheres (GS-LNPs) with 362.72 nm diameter was produced. The extractive from poplar was composed of G-syringyl (S) typed lignin (80.30 %) and xylan (12.33 %), that can assemble into LNPs with smaller size (229.87 nm), better PDI (0.1), and light color. The hybrid particles showed the qualities of lignin and xylan, that properties led to the LNPs@PVA composite films with UV-blocking capability, strong mechanical strength and hydrophobicity, and transparency ability of visible light. P-LNPs showed better performance as the film additives, due to its lower particles size and high content of unconjugated -OH from xylan. Xylan was significant in the composite films, and lowering the xylan content resulted in the decrease of the composite film's mechanical properties and hydrophobicity.

Sustainable use of Ca(OH)2 modified biochar for phosphorus recovery and tetracycline removal from water

To prevent possible secondary pollution from phosphorus-loaded biochar (BC) in agricultural systems, this study investigated the sustainable use of Ca(OH)₂ modified wood biochars (Ca-BCs) for P recovery while significantly lowering the tetracycline (TC) adsorption onto Ca-BCs. Ca-BCs were prepared via calcination of mixtures of Ca(OH)₂ and wood BC under 100-500 °C for removing P and TC from water. Compared to the pristine BC (without Ca(OH)₂ modification), Ca-BC100 (Ca-BC prepared at 100 °C) showed a significant increase of P adsorption capacity from 4.00 to 138.70 mg/g due to reactive interaction between P and Ca(OH)₂ on Ca-BC while decrease of TC adsorption capacity from 62.17 to 20.86 mg/g owing to decrease of surface area from 260.50 to 120.26 m²/g. Batch adsorption tests implied that the P adsorption on Ca-BC100 would occur mainly via electrostatic attraction (pH > 2.1) and formation of hydroxylapatite (Ca₅(PO₄)₃(OH)) between phosphate and Ca(OH)₂. In addition, Ca-BC100 reacted with TC via electrostatic attraction (pH > 7.6), complexation, hydrogen bond, and π-π interactions. P and TC adsorption onto Ca-BC100 was a chemical, endothermic, and spontaneous process. The dynamic adsorption experiments using a fixed bed column filled with Ca-BC100 indicated that Ca-BC100 could continuously and effectively remove P and TC from water. Ca-BC100 also effectively lowered P and COD in the dairy wastewater. Under the environmentally relevant conditions, continuous treatment of water containing P and TC using the pristine BC followed by Ca-BC100 showed the pristine BC removed 96% of TC and only 6% of P from water while Ca-BC100 made high recovery of P (94% of P) with negligible TC. Therefore, Ca-BC100 could be used for effective recovery of P with negligible TC from wastewater, and then applied to agricultural systems as a sustainable and safe P-rich biofertilizer.

CaCO3-coated PVA/BC-based composite for the simultaneous adsorption of Cu(II), Cd(II), Pb(II) in aqueous solution

A polymer composite material comprising polyvinyl alcohol/bacterial cellulose/calcium carbonate (PVA/BC/CaCO₃) was prepared for enabling the selective adsorption of toxic heavy metal ions, such as Cd(II), Cu(II), and Pb(II) from solution. FT-IR, SEM and XRD analyses confirmed the successful incorporation of CaCO₃ into the PVA-based polymer by chemical cross-linking with epichlorohydrin. The optimal pH for adsorption of the metal ions onto PVA/BC/CaCO₃ was determined to be 6.0. The pseudo-first-order kinetics model was best-suited for fitting the adsorption kinetics data, and the Langmuir model was best-suited for fitting the thermodynamic adsorption data. The maximum adsorption capacities of PVA/BC/CaCO₃ for Cu(II), Pb(II), and Cd(II) were found to be 57.1, 513.6, and 238.6 mg/g, respectively, at 40 °C. In addition, the adsorbent was found to be highly recyclable. Overall, PVA/BC/CaCO₃ adsorbent has the applicable potential in the removal of heavy metal ions from contaminated solution.

Nanostructured materials via green sonochemical routes - Sustainability aspects

The production of environmentally friendly nanostructured materials with well-defined properties is a major challenge. Characteristics of the nanomaterials such as dimensionality, size and morphology strongly affect their performance in various applications. Additionally, sustainability considerations require an acceptable level of efficiency while being economically feasible and environmentally benign. The use of ultrasonic irradiation (UI) is a green and powerful technology, which can be applied for the synthesis of a variety of nanostructured materials. This review critically discusses the progress made in the fabrication of environmentally benign engineered nanomaterials with various dimensionalities (i.e., zero, one, two, or three dimensions) assisted by UI. The evolution and current status in this area are further illustrated using a scientometric approach. Application of UI for the synthesis of nanostructured materials has been also assessed according to the main sustainability pillars including the performance and environmental compatibility, as well as the relevant economic and social considerations. The outlook as well as recommendations for future research has been also provided and discussed towards the promotion of sustainable nanomaterials synthesis and application in various fields.

Preparation and bacteriostatic research of porous polyvinyl alcohol / biochar / nanosilver polymer gel for drinking water treatment

Microbial contamination in drinking water has become an important threat to human health. There is thus an urgent need to develop antibacterial materials to treat drinking water. Here, porous silver-loaded biochar (C–Ag) was prepared using corn straw as the substrate and silver as the antibacterial agent. C–Ag was then uniformly distributed in polyvinyl alcohol gel beads of eluted calcium carbonate to prepare p-PVA/C–Ag antibacterial composite. The polymer composites were tested by FT-IR, XRD, SEM and TG-DSC. The results showed that C–Ag was more evenly distributed in the PVA gel spheres. Antibacterial experiments showed that p-PVA/C–Ag greatly inhibited Escherichia coli. Practical application tests revealed that p-PVA/C–Ag showed high and sustained bactericidal inhibition and reusability. Generally, p-PVA/C–Ag composite shows high potential to be applied to drinking water treatment.

Green synthesis of nano-Al2O3, recent functionalization, and fabrication of synthetic or natural polymer nanocomposites: various technological applications

Environmentally friendly fabrication of nano-Al₂O₃, recent functionalization, and preparation of polymer nanocomposites including natural and man-made polymers with various industrial applications are reviewed.

Immune-adjuvant activity of lentinan-modified calcium carbonate microparticles on a H5N1 vaccine

In recent years, the high prevalence of avian influenza viruses especially H₅N₁ subtype isolated from poultry and human has become a major public health concern. Vaccination is still a major strategy for preventing H₅N₁ infections. Lentinan (LNT), a β-1,3-glucohexaose with β-1,6-branches, is extracted from Lentinus edodes and has been extensively studied for its immunoenhancement effects. In this study, we synthesized and characterized calcium carbonate (CaCO₃) microparticles which modified with LNT as an adjuvant for H₅N₁ vaccine and investigated their ability to enhance immune responses. We prepared spherical and uniform CaCO₃-LNT microparticles with a mean hydrodynamic size was around 2 μm. The H₅N₁ antigen-loaded CaCO₃-LNT particles were injected into mice to evaluate their effectiveness as an adjuvant for H₅N₁ vaccines. The results demonstrated that CaCO₃-LNT/H₅N₁ significantly enhanced the expression of MHC-II and CD86 in lymph node dendritic cells, and increased the ratio of CD4⁺ to CD8⁺ T cells in lymphocytes. Moreover, CaCO₃-LNT/H₅N₁ surprisingly increased the HI titers and induced the secretion of IgG subtypes (IgG1 and IgG2b) and Th-associated cytokines (TNF-α, IFN-γ and IL-4) in immunized mice. Therefore, by combining with the immunostimulatory activity of LNT and the drug/antigen delivery capabilities of CaCO₃, the CaCO₃-LNT/H₅N₁ could induce a stronger cellular and humoral immune response and could be a potential adjuvant for the H₅N₁ vaccine.

Development of ultrasound treated polyvinyl alcohol/tea polyphenol composite films and their physicochemical properties

In this study, polyvinyl alcohol (PVA) was used as a film-forming substrate, added to extracted tea polyphenols (TPs) in various ratios and processed with ultrasonication to form films using the tape-casting method. The effects of ultrasonic processing duration on the properties of PVA/TP antibacterial active materials were explored via material property testing. The results showed that, overall, ultrasonic processing degraded the tensile strength and elongation at break of the composite films. When PVA/TP composite films with a PVA-to-TP mass ratio of 8:2 were processed with ultrasonication for 30 min, the swelling capacity was (740.19 ± 64.67)% and solubility was (5.26 ± 1.31)%. Ultrasonication also improved the degradability and barrier properties of composite films. Moreover, 8/2 composite films with the PVA/TP ratio of 8:2 exhibited excellent bacteriostatic properties; after ultrasonication processing, the films had a bacteriostatic rate of (95.5 ± 4.2)% and (91.8 ± 3.7)% against Staphylococcus aureus and Escherichia coli, respectively, making them suitable for use as antibacterial active materials in food packaging.

Sonochemical synthesis and properties of two new nanostructured silver(I) coordination polymers

Two new Ag(I) coordination polymers (CPs), namely, Ag(L)(Htp) (1) and [Ag(L)]·(Htp)·2H₂O (2) were synthesized from the long flexible ligand of 1,6-bis(2-methylbenzimidazolyl)hexane (L), terephthalic acid (H₂tp) and different silver(I) salts using hydrothermal and sonochemical methods, These CPs were characterized by elemental analysis, IR spectra, scanning electron microscopy, single-crystal and powder X-ray diffraction analysis. 1 features a uninodal 3-connected 2D hcb layered structure, while 2 exhibits an infinite 1D linear chain and ultimately extended into 3D supramolecular framework via O-H⋯O and Ag⋯O interactions. In addition, the effect of various sonication concentrations of the initial reagents, ultrasonic time and power of ultrasound irradiation on the size and morphology of nanostructured 1 and 2 were evaluated. Nano-sized 1 and 2 exhibit relatively high performance as UV light driven photocatalysts for the degradation of methylene blue.

Chitosan/CaCO3-silane nanocomposites: Synthesis, characterization, in vitro bioactivity and Cu(II) adsorption properties

Chitosan nanocomposites containing 2, 5, 8wt% of calcium carbonate-γ-aminopropyl triethoxy silane (CS/CC-ATS NCs) were prepared by ultrasonic irradiation. After characterizing of physicochemical properties of the obtained CS/CC-ATS NCs, their performance was evaluated for both the bone-like apatite mineralization and the removal of Cu(II). The field emission-scanning electron microscopy images from the in vitro bioactivity of the CS and the CS/CC-ATS NC 5wt% displayed that the hydroxyapatite was produced on the samples surface. However, the distribution of it on the surface of CS/CC-ATS NC 5wt% was better than the pure CS. The uptake of Cu(II) on the CS/CC-ATS NC 5wt% was studied under different adsorption conditions such as contact time, the initial concentration of metal ion and adsorbent amount. The results of isothermal adsorption of the pure CS and the CS/CC-ATS NC 5wt% were well fitted by Langmuir model for Cu(II) with adsorption capacity of 33.33 and 33.90mg·g^-1, respectively. As a result, the CS/CC-ATS NC has great potencies in both the bone tissue engineering and the uptake of toxic metal from solution.

Ultrasonic-assisted manufacturing of new hydrogel nanocomposite biosorbent containing calcium carbonate nanoparticles and tragacanth gum for removal of heavy metal

This article reports the first incorporation of calcium carbonate nanoparticles (CC NPs) into tragacanth gum (TG) to prepare a new hydrogel nanocomposite (HNC) system using a green, safe, and eco-friendly method, ultrasound irradiation as an efficient biosorbent of heavy metal ions from wastewater. Morphological studies revealed that the surface of obtained HNCs is rough, homogeneous, and porous-like due to the embedding of CC NPs as well as sonication in comparison to the neat TG which has a smooth surface. The particle size reduction was observed for CC NPs in the matrix (from 57 to 10 nm), which is owing to the extraordinary effect of sonication on this process. Thermal stability of HNCs has been increased after using CC NPs from 8.5 wt% for TG to about 22 wt% for HNCs. The optical band gap of TG/CC HNC 5 wt% calculated to be 4.46 eV which is less than that of CC NPs (5.58 eV) and even TG (6.28 eV) and this result indicated that TG/CC HNC 5 wt% is relatively more conductive than CC NPs and TG. The nitrogen adsorption-desorption disclosed an isotherm type III of Brunauer classification for TG/CC HNC 5 wt% and the surface area has been increased from 0.7 m².g^-1 for TG to 2.3 m².g^-1 for TG/CC HNC 5 wt%. Also, the BET surface area for TG/CC HNC 5 wt% calculated to be 7.8 nm which is classified into mesoporous materials. The Pb²⁺ ions were significantly removed from water using TG/CC HNC 5 wt% and the removal efficiency was determined as 83% at optimized conditions (pH = 5, adsorbent dosage = 0.015 g, time = 3 h, and Pb²⁺ concentration = 70 mg.L^-1).

Ultrasonic-promoted rapid preparation of PVC/TiO2-BSA nanocomposites: Characterization and photocatalytic degradation of methylene blue

In the present project in order to prevent agglomeration and better dispersion of TiO₂ nanoparticles (NPs) in the poly(vinyl chloride) (PVC) matrix, initially, the surface of TiO₂ NPs was covered by bovine serum albumin protein (BSA) via sonication method. Then, the TiO₂-BSA powders were embedded into the PVC matrix using ultrasonic irradiations. With mechanical and magnetic stirring homogenous mixture was not obtained. So sonication process was very essential and vital. Physical, chemical and structural properties of the samples were investigated with various tools. Morphology studies showed the well distribution of spherical TiO₂ NPs in the PVC matrix. TGA analysis showed that nanocomposites (NCs) have higher thermal stability than the pristine polymer. The photocatalytic activity tests by destroying the methylene blue dye on the pristine TiO₂ NPs, TiO₂-BSA NPs and PVC/TiO₂-BSA NC 6 wt% were examined. The results showed that the photocatalytic activity of TiO₂ NPs was reduced in the presence of BSA and PVC. It can be concluded that the TiO₂-BSA NPs and PVC/TiO₂-BSA NC 6 wt% have UV shielding properties and can protect film from degradation by UV.

Ultrasonic-assisted fabrication of starch/MWCNT-glucose nanocomposites for drug delivery

The principal focus of this investigation is to prepare starch nanocomposite (NC) films containing multi-walled carbon nanotube (MWCNT) and apply these NCs for drug delivery. Firstly, to raise the hydrophilicity of carboxyl functionalized MWCNT, the surface of them was modified with d-glucose (Gl) as a low cost and environmentally friendly biomolecule. Different percentages of MWCNT-Gl (0.5, 1 and 2wt%) were embedded in starch matrix through sonochemical method as an economical, fast, eco-friendly, and effective method. The properties of starch/MWCNT-Gl NCs were characterized using Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, field emission scanning electron microscopy and transmission electron microscopy (TEM). Afterwards, pure starch and starch/MWCNT-Gl NCs were reacted with oleic acid to obtain amphiphilic (Amph) esters. Except Amph obtained from pure starch, other Amph esters could convert to drug-loaded nanoparticles which were characterized by dynamic light scattering and TEM. The sizes of nanoparticles depended on the value of MWCNT-Gl. The thinnest particles obtained from starch/MWCNT-Gl NCs containing the highest value of MWCNT-Gl (2wt%), and this system was chosen for measurement of entrapment efficiency, loading capacity and in vitro release study for zolpidem as a hydrophobic drug model.