Removal of the Anionic Dye Congo Red from an Aqueous Solution Using a Crosslinked Poly(vinyl alcohol)-ZnO-Vitamin M Nanocomposite Film: A Study of the Recent Concerns about Nonlinear and Linear Forms of Isotherms and Kinetics.

This paper deals with the preparation, characterization, and application of a crosslinked poly(vinyl alcohol)/ZnO-vitamin M (PVA/ZnO-VM) nanocomposite film for the removal of Congo red (CR) from an aqueous solution. The characterization of a crosslinked PVA/ZnO-VM nanocomposite film showed that the structure became more regular and also the surface morphology appeared smooth in comparison with pure PVA. The obtained data from Brunauer-Emmett-Teller (BET) proved the mesoporous structure for this nanocomposite film. Several effective factors were examined for the adsorption ability of the nanocomposite film, including solution pH (2-10), sorbent amount (0.02-0.08 g), contact time (3-240 min), initial concentration of the adsorbate (30-300 mg·L-1), and temperature (318-358 K). The optimal conditions are as follows: pH = 10, adsorbent amount = 0.06 g, and C0 = 200 mg·L-1. The removal efficiency of the nanocomposite film was 92% after 4 h at the ambient temperature. To interpret the adsorption process, nonlinear and linear forms of kinetic and isotherm models were considered. The obtained data followed nonlinear pseudo-second-order and linear Langmuir isotherm models, which indicated the monolayer formation of CR over the crosslinked PVA/ZnO-VM nanocomposite film with the maximum adsorption capacity of about 56.49 mg·g-1. Also, the adsorption process of CR by the crosslinked PVA/ZnO-VM nanocomposite film is a spontaneous and exothermic reaction.

Recent breakthroughs of antibacterial and antiviral protective polymeric materials during COVID-19 pandemic and after pandemic: Coating, packaging, and textile applications.

The global epidemic owing to COVID-19 has generated awareness to ensuring best practices for avoiding the microorganism spread. Indeed, because of the increase in infections caused by bacteria and viruses such as SARS-CoV-2, the global demand for antimicrobial materials is growing. New technologies by using polymeric systems are of great interest. Virus transmission by contaminated surfaces leads to the spread of infectious diseases, so antimicrobial coatings are significant in this regard. Moreover, antimicrobial food packaging is beneficial to prevent the spread of microorganisms during food processing and transportation. Furthermore, antimicrobial textiles show an effective role. We aim to provide a review of prepared antimicrobial polymeric materials for use in coating, food packaging, and textile during the COVID-19 pandemic and after pandemic.

Adsorption of Methyl Orange from Aqueous Solution Using PVOH Composite Films Cross-Linked by Glutaraldehyde and Reinforced with Modified α-MnO2.

A poly(vinyl alcohol) (PVOH) composite cross-linked with glutaraldehyde (GL) containing α-MnO2 modified with stearic acid (ST) was fabricated as an efficient sorbent for capturing methyl orange (MO) dye from the water system. We investigated the factors affecting MO adsorption in detail. The adsorption process showed a high dependence on the pH value. The highest removal efficiency (96.5%) was obtained at pH 2. The adsorption isotherm study indicated that the linear Freundlich isotherm was a more appropriate model for the adsorption process. The adsorption kinetics study revealed that the adsorption data matched with a nonlinear pseudo-first-order model. Physical adsorption interactions, including electrostatic interactions, hydrogen bonds, and dipole-dipole forces, play dominant roles in this process. Thermodynamic investigations confirmed that MO adsorption was spontaneous and exothermic with physical interactions. The outcomes demonstrated that the cross-linked PVOH-GL/α-MnO2-ST composite could be a hopeful sorbent for the efficient uptake of MO molecules from polluted waters.

Tragacanth gum mediated green fabrication of mesoporous titania nanomaterials: Application in photocatalytic degradation of crystal violet.

Water remediation is a crucial subject in present century. Hence, several processes have been used for this aim, which the photodegradation method with high activity, cost-effectiveness, and durability has been remarkable. In this project, the various novel mesoporous Titania nanomaterials (MTN) were green synthesized using Tragacanth gum as coupling agent. The effect of calcination times on the crystalline structure of the resulted MTNs was examined. MTNs displayed the dramatically specific surface area with negative surface charge and nano-sheet structure, and they applied for photodegradation of crystal violet under ultraviolet irradiation due to proper band gaps energy. The obtained MTN in 8 h calcination time (MTN-8) showed the best photoreduction activity. Also, the superoxide radicals, electrons, and hole pairs represented the main degradation agents as the reduction rate of crystal violet. Next, the transformation pathways were proposed, which could be transformation singlet oxygen addition, hydroxyl addition, and N-demethylation reactions.

The synthesis of poly(vinyl chloride) nanocomposite films containing ZrO2 nanoparticles modified with vitamin B1 with the aim of improving the mechanical, thermal and optical properties.

In the present investigation, solution casting method was used for the preparation of nanocomposite (NC) films. At first, the surface of ZrO2 nanoparticles (NPs) was modified with vitamin B1 (VB1) as a bioactive coupling agent to achieve a better dispersion and compatibility of NPs within the poly(vinyl chloride) (PVC) matrix. The grafting of modifier on the surface of ZrO2 was confirmed by Fourier transform infrared spectroscopy and thermogravimetric analysis (TGA). Finally, the resulting modified ZrO2 (ZrO2-VB1), was used as a nano-filler and incorporated into the PVC matrix to improve its mechanical and thermal properties. These processes were carried out under ultrasonic irradiation conditions, which is an economical and eco-friendly method. The effect of ZrO2-VB1 on the properties and morphology of the PVC matrix was characterized by various techniques. Field emission scanning electron microscopy and transmission electron microscopy analyses showed a good dispersion of fillers into the PVC matrix with the average diameter of 37-40 nm. UV-Vis spectroscopy was used to study optical behavior of the obtained NC films. TGA analysis has confirmed the presence of about 7 wt% VB1 on the surface of ZrO2. Also, the data indicated that the thermal and mechanical properties of the NC films were enhanced.

Preparation, characterization and solid-state emission of metal complex-cloisite nanohybrids (MC-C, M = Ru (II) and Cu (II)).

The presence of Na(+) in the Cloisite Na(+) mineral allows modification of its interlayer space to achieve a better compatibility with the host matrix and ion-exchange with a cationic metal complex. The aim of this research is to prepare two new metal complex-Cloisite (MC-C) nanohybrids using reaction of Cloisite Na(+) with the cationic Ru (II) and Cu (II) complexes, [Ru (tpy) 2] (2+) and [Cu (Pir) (phen) (H2O) 2](+), in an aqueous solution for the first time. The X-ray diffraction (XRD) analysis of the modified clays has shown an increase in its interlayer distance as compared to the unmodified Cloisite Na(+). The positions of the basal reflections in the XRD patterns of the modified clays were shifted to a higher d value indicating the expansion in their interlayer distances. The field-emission scanning electron microscopy has shown a homogeneous morphology for the modified clays. The thermal behavior of these novel hybrid materials was also investigated by thermogravimetric analysis. The solid state fluorescence spectra of the modified clays have shown that both cationic complexes exhibit a significant fluorescence emission at room temperature when intercalated into Cloisite.

Chiral bio-nanocomposites based on thermally stable poly(amide-imide) having phenylalanine linkages and reactive organoclay containing tyrosine amino acid.

Montmorillonite clay modified with the bio-active trifunctional L-tyrosine amino acid salt was used as a reactive organoclay (OC) for the preparation of poly(amide-imide) (PAI)/OC hybrid films. One of the functional groups of the L-tyrosine as the swelling agent formed an ionic bond with the negatively charged silicates, whereas the remaining functional groups were available for further reaction with polymer matrix. The soluble PAI with amine end groups including phenylalanine amino acid was synthesised under green condition using molten tetra-butylammonium bromide by direct polymerization reaction of chiral diacid and 2-(3,5-diaminophenyl)benzimidazole. PAI/OC bio-nanocomposites films containing different contents of OC were prepared via solution intercalation method through blending of OC with the PAI solution. X-ray diffraction and transmission electron microscopy revealed that the dispersion of silicate layers in the PAI created an exfoliated structure as a result of using the trifunctional groups of the swelling agent. The structure and thermal behavior of the synthesised materials were characterized by a range of methods, including X-ray diffraction, Fourier transform infrared spectroscopy, (1)H-NMR, electron microscopy, elemental and thermogravimetric analysis techniques. Thermogravimetric analysis results indicated that the addition of OC into the PAI matrix was increased in the thermal decomposition temperatures of the resulted bio-nanocomposites.

Chitosan/tannic acid/ZnFe layered double hydroxides and mixed metal oxides nanocomposite for the adsorption of reactive dyes.

The fabrication of the environmentally friendly nanocomposite beads containing chitosan (Chi), tannic acid (TA), layered double hydroxides (LDH), and mixed metal oxides (MMO) was carried out. The synthesized ZnFe LDH, ZnFe MMO, and fabricated beads (Chi/TA@LDH and Chi/TA@MMO) were characterized using FESEM, XRD, FTIR, BET, and TGA. The beads were applied for the simultaneous removal of three reactive dyes. The design of experiments was based on a full factorial design considering the effect of six independent variables (initial dye concentrations, adsorbent dosage, time, and adsorbent type) on the dye removal percentages (DR%) of each dye. Regression equations were extracted from the experimental results (R2 > 0.983) and high obtained F-values from analysis of variance (ANOVA) proved the significance of the models. The maximum adsorption capacity of the dyes onto, Chi/TA@LDH and Chi/TA@MMO beads were between 257 and 483 mg g-1. The spontaneity and exothermic nature of the adsorption processes were determined by thermodynamic studies (-8 < ΔH° (KJ mol-1) < -1, -22 < ΔG° (KJ mol-1) < -18). Reusability studies showed that the fabricated beads could be regenerated and applied several times.

Removal of cationic and anionic dyes using Ca-alginate and Zn-Al layered double hydroxide/metal-organic framework.

In this study, a novel effective bio adsorbent was produced and employed to remove congo red and methylene blue dyes from water matrices. First, Zn-Al layered double hydroxide (Zn-Al LDH) was manufactured in a hydrothermal process. Next, through in-situ nucleation and growing of crystalline NH2-modified Ti metal-organic framework (NH2-MIL-125(Ti) on Zn-Al sheets by solvothermal method, Zn-Al LDH@NH2-MIL-125(Ti) hybrid was produced. The prepared hybrid showed good adsorption capacity (qmax values: 294 mg/g and 158 mg/g) for congo red and methylene blue dyes in optimum condition (adsorbent amount = 5-7 mg, dye concentration = 100-150 mg/L, V = 10 mL, pH = no adjustment, and contact time = 2-5 h). Based on the isotherm and kinetic models, the Langmuir isotherm, as well as the pseudo-second-order model, were fit to the equilibrium data. In the next attempt, to improve the reusability of the powder and particle form of Zn-Al LDH@NH2-MIL-125(Ti) hybrid, as well as prevent of formation of secondary contamination in water, Na-alginate, as a cheap and effective substrate, was used. Novel architectures of robust, reusable, and efficient Ca-alginate/Zn-Al LDH@NH2-MIL-125(Ti) microgel beads were prepared and the performances of the microbeads were compared with pure LDH@NH2-MIL-125(Ti) hybrid.

Comparative study for removal of cationic and anionic dyes using alginate-based hydrogels filled with citric acid-sawdust/UiO-66-NH2 hybrid.

Nowadays, a big challenge is developing a sustainable and effective method for removing contaminants like dyes from aqueous solutions. In this regard, Zr-based metal-organic framework (UiO-66-NH2) and sawdust as the ideal adsorbents were used. Due to their low separation in adsorption processes, embedding into alginate and obtaining composite beads are suggested as a suitable strategy. The achieved Ca-alginate/citric acid (CA)-sawdust/UiO-66-NH2 hydrogel beads were used to compare cationic and anionic dyes removal. This sorbent indicated an excellent selectivity for removing methylene blue versus methyl orange in a binary system. pH = 6, adsorbent amount = 80 mg, methylene blue concentration = 10 mg/L, and contact time = 420 min were achieved as optimal parameters on methylene blue adsorption with an adsorption capacity of about 26 mg/g. The removal process of methylene blue followed linear Freundlich isotherm and nonlinear pseudo-2nd-order kinetic models. The regeneration test demonstrated methylene blue removal efficiency higher than about 89 % after 9 cycles. According to the outcomes, methylene blue could be attached to the adsorbent surface through the electrostatic, hydrogen bonding, and π-π interactions of the aromatic rings. These results confirm the potential of Ca-alginate/CA-sawdust/UiO-66-NH2 hydrogel beads as a selective bio-sorbent for cationic dye removal.

Worldwide fight against COVID-19 using nanotechnology, polymer science, and 3D printing technology.

One of the lethal illnesses that humanity has ever seen is COVID-19 irrefutably. The speed of virus spread is high and happens through polluted surfaces, respiratory droplets, and bodily fluids. It was found that without an efficient vaccine or specific treatment using personal protective equipment, preventing contamination of hands, and social distancing are the best ways to stay safe during the present pandemic. In this line, polymers, nanotechnology, and additive manufacturing, or 3D printing technology have been considered to probe, sense, and treat COVID-19. All aforementioned fields showed undeniable roles during the COVID-19 pandemic, which their contributions have been reviewed here. Finally, the effect of COVID-19 on the environment, alongside its positive and negative effects has been mentioned.

Novel nanostructure amino acid-based poly(amide-imide)s enclosing benzimidazole pendant group in green medium: fabrication and characterization.

In the present work, several novel optically active nanostructure poly(amide-imide)s (PAI)s were synthesized via step-growth polymerization reaction of chiral diacids based on pyromellitic dianhydride-derived dicarboxylic acids containing different natural amino acids such as L-alanine, S-valine, L-leucine, L-isoleucine, L-methionine, and L-phenylalanine with 2-(3,5-diaminophenyl)-benzimidazole under green conditions using molten tetrabutylammonium bromide. The new optically active PAIs were achieved in good yields and moderate inherent viscosity up to 0.41 dL/g. The synthesized polymers were characterized with FT-IR, (1)H-NMR, X-ray diffraction, field emission scanning electron microscopy (FE-SEM), elemental and thermogravimetric analysis (TGA) techniques. These polymers show high solubility in organic polar solvents due to the presence of amino acid and benzimidazole pendant group at room temperature. FE-SEM results show that, these chiral nanostructured PAIs have spherical shapes and the particle size is around 20-80 nm. On the basis of TGA data, such PAIs are thermally stable and can be classified as self-extinguishing polymers. In addition due to the existence of amino acids in the polymer backbones, these macromolecules are not only optically active but also could be biodegradable and thus may well be classified under environmentally friendly materials.

Preparation and characterization of novel optically active poly(vinyl alcohol-co-vinyl ester) in nonaqueous medium using L-phenylalanine as a chiral material.

In this investigation, poly(vinyl alcohol) was chemically modified by the introduction of different amounts of N-phthaloyl-L-phenylalanine. The modification was carried out by the reaction of PVA hydroxyl groups with (2S)-3-phenyl-2-phthalimidylpropanoyl chloride using N,N-dimethyl acetamide/lithium chloride as a reaction media. The novel copolymers obtained were characterized by spectroscopic techniques, elemental analysis, X-ray diffraction and thermal methods. Optical rotation and viscosities were also measured. The degree of esterification was determined by (1)H-NMR. The influence of reagent molar ratio on the degree of modification was also evaluated. The vinyl(3-phenyl-2-phthalimidopropanoate) content in the copolymer was attained up to 52%. Thermal stability of the copolymers was checked by thermogravimetric analysis and differential thermogravimetric analysis. All copolymers displayed improved thermal stability compared to the parent polymer.

Synthesis and properties of optically active nanostructured polymers bearing amino acid moieties by direct polycondensation of 4,4'-thiobis(2-tert-butyl-5-methylphenol) with chiral diacids.

Four derivatives of N-trimellitylimido-L-amino acid (4a-4d) were prepared by the reaction of trimellitic anhydride (1) with the L-amino acids (2a-2d) in acetic acid as diacid monomers and were used with the aim to obtain a new family of amino acid based poly(ester-imide)s (PEI)s. The polymerization was performed by direct polycondensation of chiral diacids (4a-4d) with 4,4'-thiobis(2-tert-butyl-5-methylphenol) (5) in the presence of tosyl chloride (TsCl), pyridine and N,N-dimethyl formamide (DMF). Step-growth polymerization was carried out by varying the time of heating and the molar ratio of TsCl/diacid and the optimum conditions were achieved. The synthesized polymers were characterized by means of specific rotation experiments, FT-IR, 1H-NMR, X-ray diffraction techniques and elemental analysis. The surface morphology of the obtained polymers was studied by field emission scanning electron microscopy. The result showed nanostructure morphology of the resulting polymers. The obtained PEIs were soluble in polar aprotic solvents such as DMF, N,N-dimethyl acetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone and protic solvents such as sulfuric acid. Thermal stability and the weight-loss behavior of the PEIs were studied by thermal gravimetric analysis (TGA) techniques. TGA showed that the 10% weight loss temperature in a nitrogen atmosphere was more than 402°C, therefore they had useful levels of thermal stability associated with excellent solubility.

Fabrication of biodegradable poly(ester-amide)s based on tyrosine natural amino acid.

N,N'-Bis[2-(methyl-3-(4-hydroxyphenyl)propanoate)]isophthaldiamide (5), a novel diol monomer containing chiral group, was prepared by the reaction of S-tyrosine methyl ester (3) with isophthaloyl dichloride (4a). A new family of optically active and potentially biodegradable poly(ester-amide)s (PEAs) based on tyrosine amino acid were prepared by the polycondensation reaction of diol monomer 5 with several aromatic diacid chlorides. The resulting new polymers were obtained in good yields with inherent viscosities ranging between 0.25 and 0.42 dL/g and are soluble in polar aprotic solvents. They showed good thermal stability and high optical purity. The synthetic compounds were characterized and studied by FT-IR, 1H-NMR, specific rotation, elemental and thermogravimetric analysis (TGA) techniques and typical ones by 13C-NMR, differential scanning calorimetry (DSC), X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM) analysis. Soil burial test of the diphenolic monomer 5, and obtained PEA6a, and soil enzymatic assay showed that the synthesized diol and its polymer are biologically active and probably biodegradable in soil environment.

Development of sodium alginate-pectin/TiO2 nanocomposites: Antibacterial and bioactivity investigations.

In this research, sodium alginate-pectin composite (ALG-PEC CS) and nanocomposites (NCs) films with 0.5, 1, and 2 wt% TiO2 nanoparticles (NPs) were prepared using CaCl2 and glutaraldehyde (Glu) as cross-linkers. The cross-linking produces rigid scaffolds for sedimentation of hydroxyapatite (HA), it can also decrease solubility in water and simulated body fluid (SBF) solution to 10% or less. The increase of the adsorbed water and SBF extends the pores and consequently the surface area for HA growth. Bioactive ability was confirmed via HA's presence on the all films. It was revealed that the film containing 2 wt% TiO2 NPs had the best bioactivity without any in vitro cytotoxicity on MG-63 cell line and the best antibacterial performance against Staphylococcus aureus, and after 1 h all the bacteria were killed.

Bio-sorbent alginate/citric acid-sawdust/Fe3O4 nanocomposite beads for highly efficient removal of malachite green from water.

Sawdust is a by-product of wood-related industries with striking features for pollutant uptake. For the first time in the current study, sustainable magnetic alginate composite beads containing citric acid-modified sawdust (CA-sawdust) as a bio-waste and Fe3O4 nanoparticles were designed. This novel eco-friendly composite (Alginate/CA-sawdust/Fe3O4 beads) was successfully applied to remove cationic malachite green (MG). Easy separation under a magnetic field and reusability could be mentioned as two significant properties of this bio-sorbent. The removal percentage of MG using alginate/CA-sawdust/Fe3O4 beads was calculated to be 90-95 %. This process was well-described with Langmuir isotherm and nonlinear pseudo-first-order kinetic models. Moreover, both film and intraparticle diffusion models were found to be probable removal mechanisms.

Fabrication of air filters with advanced filtration performance for removal of viral aerosols and control the spread of COVID-19.

COVID-19 is caused via the SARS-CoV-2 virus, a lipid-based enveloped virus with spike-like projections. At present, the global epidemic of COVID-19 continues and waves of SARS-CoV-2, the mutant Delta and Omicron variant which are associated with enhanced transmissibility and evasion to vaccine-induced immunity have increased hospitalization and mortality, the biggest challenge we face is whether we will be able to overcome this virus? On the other side, warm seasons and heat have increased the need for proper ventilation systems to trap contaminants containing the virus. Besides, heat and sweating accelerate the growth of microorganisms. For example, medical staff that is in the front line use masks for a long time, and their facial sweat causes microbes to grow on the mask. Nowadays, efficient air filters with anti-viral and antimicrobial properties have received a lot of attention, and are used to make ventilation systems or medical masks. A wide range of materials plays an important role in the production of efficient air filters. For example, metals, metal oxides, or antimicrobial metal species that have anti-viral and antimicrobial properties, including Ag, ZnO, TiO2, CuO, and Cu played a role in this regard. Carbon nanomaterials such as carbon nanotubes, graphene, or derivatives have also shown their role well. In addition, natural materials such as biopolymers such as alginate, and herbal extracts are employed to prepare effective air filters. In this review, we summarized the utilization of diverse materials in the preparation of efficient air filters to apply in the preparation of medical masks and ventilation systems. In the first part, the employing metal and metal oxides is examined, and the second part summarizes the application of carbon materials for the fabrication of air filters. After examination of the performance of natural materials, challenges and progress visions are discussed.

Optimization of chitosan/tannic acid@ ZnFe layered double hydroxide bionanocomposite film for removal of reactive blue 4 using a response surface methodology.

Layered double hydroxides (LDH) are great adsorbents for anionic pollutants, but are in a powder form that leads to challenges in solid-liquid separation, low hydraulic conductivity, and handling. Herein, novel bionanocomposite films containing chitosan (Cs), tannic acid (TA), and LDH were fabricated and applied for the removal of reactive blue 4 (RB4). A response surface methodology with Box-Behnken design was applied to study the effect of operating parameters (TA%: 0-20, LDH%: 0-20, pH: 5-9, adsorbent dosage: 0.5-1.5 g L-1, time: 30-90 min) on RB4 dye removal (DR%). A quadratic regression equation was successfully developed to predict the response (R2: 0.95). The obtained optimized condition was TA%: 10, LDH%: 20, pH: 5, adsorbent dosage: 1.5 g L-1, and time: 71 min that resulted in DR%: 98.2. The best-fitted adsorption isotherm and kinetic models were linear Langmuir and nonlinear pseudo-second-order models, respectively. The maximum capacity of adsorption for the optimized film was 406 mg g-1. The obtained thermodynamic parameters implied that the process of adsorption was exothermic and spontaneous. The reusability studies showed that the DR% was decreased from 93% for the first cycle to 69%, 57%, and 56% for the second, third and fourth cycle, respectively.

A new trend of using poly(vinyl alcohol) in 3D and 4D printing technologies: Process and applications.

Recently, 3D/4D printing technologies have been the researchers' interest, and they are getting improved more important. They are applicable in various fields like medical fields, pharmaceutics, construction, tissue engineering, dentistry, water treatment, etc. These technologies overcame the difficulty of the conventional methods in producing complicated structures. They can be fed by different materials such as nanomaterials, smart polymers, responsive polymers, metamaterials, synthetic polymers, natural polymers, and so forth. One of the smart and stimuli-responsive polymers is poly(vinyl alcohol) (PVA). In addition to numerous applications of PVA like medicine, environmental fields, etc., researchers are showing a tendency to use PVA in 3D/4D printing technologies. The main reasons for PVA's increased interest in 3D/4D printing technologies are suitable flowability, stimuli-responsivity, extrudability, biocompatibility, biodegradability, cost-effectiveness, and other features. This review aims to introduce the 3D/4D printing technologies' knowledge and then the applications of PVA as a feed in these novel technologies.