Enhanced selective adsorption of cation organic dyes on polyvinyl alcohol/agar/maltodextrin water‐resistance biomembrane

Maltodextrin-modified graphene oxide composite membrane applied to the enantioseparation of amino acids

The separation of enantiomers using chiral membranes has garnered much research interest. In this study, the enantioseparation of amino acids using chiral membranes, namely graphene oxide-ethylenediamine-maltodextrin (GO-EDA-MD) and GO-EDA-hydroxypropyl-MD (GO-EDA-HP-MD), was evaluated. HP-MD and MD were investigated as chiral selectors due to their inherent chirality. Various characterization techniques, including atomic force microscopy, Fourier transform infrared spectrometry, field emission scanning electron microscopy, water contact angle analysis, tensile properties, and thermal gravimetric analysis were employed to analyze the membrane structures. The evaluation of enantioseparation performance was conducted by employing tryptophan, phenylalanine, and tyrosine enantiomers. Optimal conditions for enantiomer separation were achived using a GO-EDA-HP-MD chiral composite (1.75 wt%), a feed concentration of 10 mg/L for each enantiomer, a separation time of 15 min, and a membrane effective surface area of 1.0 cm2. Also, the bovine serum albumin rejection was 90.0 %, and the water flux reached 37.1 L m-2 h-1. The highest enantiomeric excess (ee.%) values were 46.33 %, 76.97 %, and 73.04 % for tryptophan, phenylalanine, and tyrosine, respectively. The impact of voltage on ee.% and substance flux was also explored. This membrane was able to separate enantiomers successfully.

New Surface Modification of Hydrophilic Polyvinyl Alcohol via Predrying and Electrospinning of Hydrophobic Polycaprolactone Nanofibers

Despite the excellent oxygen barrier and biodegradability of polyvinyl alcohol (PVA), its poor physical properties owing to its inherent hydrophilicity limit its application. In this paper, we report a novel surface modification technique for PVA films, involving the control of the predrying conditions (i.e., amount of residual solvent) of the coated PVA film and adjusting the electrospinning process of hydrophobic polycaprolactone (PCL) nanofibers onto the PVA films. The residual solvent of the coated PVA film was varied by changing the predrying time. A shorter predrying time increased the residual solvent content significantly (p < 0.05) and the flexibility of the coated PVA film. Moreover, scanning electron microscopy depicted the improved physical binding of hydrophobic PCL nanofibers to the hydrophilic PVA surface with increased penetration depth to the PVA film with shorter drying times. The PVA/PCL composite films with different predrying times and electrospun PCL nanofibers exhibited an apparent increase in the contact angle from 8.3° to 95.1°. The tensile strength of the pure PVA film increased significantly (p < 0.05) from 7.5 MPa to 77.4 MPa and its oxygen permeability decreased from 5.5 to 1.9 cc/m2·day. Therefore, our newly developed technique is cost-effective for modifying the surface and physical properties of hydrophilic polymers, broadening their industrial applications.

Dextrin-Based Adsorbents Synthesized via a Sustainable Approach for the Removal of Salicylic Acid from Water

Pharmaceuticals such as salicylic acid are commonly detected in wastewater and surface waters, increasing concern for possible harmful effects on humans and the environment. Their difficult removal via conventional treatments raised the need for improved strategies, among which the development of bioderived adsorbents gained interest because of their sustainability and circularity. In this work, biobased cross-linked adsorbents, synthesized via a sustainable approach from starch derivatives, namely beta-cyclodextrins and maltodextrins, were at first characterized via FTIR-ATR, TGA, SEM, and elemental analysis, showing hydrophilic granular morphologies endowed with specific interaction sites and thermal stabilities higher than 300 °C. Subsequently, adsorption tests were carried out, aiming to assess the capabilities of such polymers on the removal of salicylic acid, as a case study, from water. Batch tests showed rapid kinetics of adsorption with a removal of salicylic acid higher than 90% and a maximum adsorption capacity of 17 mg/g. Accordingly, continuous fixed bed adsorption tests confirmed the good interaction between the polymers and salicylic acid, while the recycling of the adsorbents was successfully performed up to four cycles of use.

Green hydrophobic maltodextrin nanosponges for magnetic solid-phase extraction of hypothalamic peptides from plasma samples

In this work, for the first time, magnetic-phthalated maltodextrin nanosponges (M-PAMDNSs) were synthetized and introduced as efficient and green sorbents. The integration of phthaloyl groups as hydrophobic moieties into networks of maltodextrin nanosponges provided good enrichment for hypothalamic-related peptides (HRPs). The synthesized materials were characterized by 1H nuclear magnetic resonance spectroscopy, water contact angle, attenuated total reflection-Fourier transform infrared spectroscopy, dynamic light scattering, zeta potential, pH point of zero charge, acid-base titration, field-emission scanning electron microscopy, Brunauer-Emmett-Teller, and vibrating sample magnetometer. Under the optimized conditions (sorbent amount: 5.0 mg, desorption solvent volume and type: 300 µL of methanol: H2O: trifluoroacetic acid, extraction time: 15 min, and desorption time: 10 min), the developed magnetic solid-phase extraction (MSPE) method in combination with HPLC-UV was used as a novel and sensitive analytical method for the determination of HRPs in plasma samples. The proposed MSPE-HPLC-UV method provided good linearity (1.5-500 ng mL-1 R2 ≥ 0.9988), low limits of detection (0.1-0.2 ng mL-1) and quantification (0.4-0.8 ng mL-1), desirable precision (RSD ≤ 8.8%, n ₌ 5), satisfactory enrichment factor (EFs ≥ 66.0), and well relative recoveries (92.8-108.8%). Overall, the established method effectively expanded the analytical potential of MSPE approach for the quantification of HRPs in biological samples.

Polypyrrole Aerogels: Efficient Adsorbents of Cr(VI) Ions from Aqueous Solutions

Three-dimensional and porous polypyrrole (PPy) aerogels were prepared using a facile two-step procedure in which cryogels were synthesized via the cryopolymerization of pyrrole with iron (III) chloride in the presence of supporting water-soluble polymers (poly(N-vinylpyrrolidone), poly(vinyl alcohol), gelatin, methylcellulose or hydroxypropylcellulose), followed by freeze-drying to obtain aerogels. The choice of supporting polymers was found to affect the morphology, porosity, electrical conductivity, and mechanical properties of PPy aerogels. PPy aerogels were successfully used as adsorbents to remove toxic Cr(VI) ions from aqueous solutions.

Preparation and characterization of a novel absorbent pad based on polyvinyl alcohol/gellan gum/citric acid with incorporated Perilla leaf oil nanoemulsion for chilled chicken packaging

A novel absorbent pad based on polyvinyl alcohol (PVA)/gellan gum/citric acid (CA) composite with incorporated Perilla leaf oil (PO) nanoemulsion was prepared and characterized. The esterification between PVA and CA and strong hydrogen bonds were detected. The PVA improved the tensile strength and elongation at break by 110% and 73%, respectively, whereas PO concentration ≤ 1.5 % (w/v) had little effect on the material properties. The CA and PO nanoemulsion loaded in the pads showed good antioxidant activity, and the pads with PO concentration ≥ 1.5 % (w/v) had effective antimicrobial activity against Escherichia coli and Staphylococcus aureus. The results of chilled chicken storage experiments indicated that the pad with 1.5% (w/v) PO nanoemulsion extended the shelf life of chicken to at least 9 days, demonstrating that the developed absorbent pads are potential materials for chilled chicken storage packing.

Photocatalytic degradation of remdesivir nucleotide pro-drug using [Cu(1-methylimidazole)4(SCN)2] nanocomplex synthesized by sonochemical process: Theoretical, hirshfeld surface analysis, degradation kinetic, and thermodynamic studies

The first ultrasonic synthesis of [Cu(L)₄(SCN)₂] (L = 1-methylimidazole) nanocomplex was carried out under ultrasonic irradiation, and its photocatalytic performance for the degradation of remdesivir (RS) under sunlight irradiation was comprehensively investigated for the first time in this study. The physicochemical properties of the synthesized photocatalyst were examined by Fourier-transform infrared (FT-IR), field emission scanning electron microscopy (FE-SEM), diffuse reflectance spectroscopy (DRS), and thermogravimetric analysis (TGA) techniques. The band gap of the synthesized [Cu(L)₄(SCN)₂] nanocomplex was determined to be 2.60 eV by the diffuse reflectance spectroscopy method using Kubelka-Munk formula. The photocatalytic performance of nanocomplex was examined for the removal of remdesivir under sunlight from water for which the results indicated that an amount of 0.5 gL^-1 of the [Cu(L)₄(SCN)₂] nanocomplex was sufficient to remove more than 96% remdesivir from its 2 mg L^-1 concentration within 20 min, at pH = 6. The kinetic data showed that the photodegradation onto the [Cu(L)₄(SCN)₂] nanocomplex has a high correlation (0.98) with the pseudo-second-order kinetic model. The decrease in chemical oxygen demand (COD) (from 70.5 mg L^-1 to 36.4 mg L^-1) under optimal conditions clearly confirmed the mineralization of the RS drug. The values of ΔS° (-0.131 kJ mol^-1 K^-1) and ΔH° (-49.750 kJ mol^-1) were negative, indicating that the adsorption process was spontaneous and more favorable in lower temperatures. Moreover, the RS structure in the open shell state and the high HOMO and LUMO gaps based on the M06/6-31 + G (d) level of theory may be a confirmation of this fact. In addition, the Hirshfeld surface analysis (HSA) of the crystal packing of the prepared complex was discussed in detail to evaluate the interactions between the crystal packings. The results of this study confirm that the [Cu(L)₄(SCN)₂] nanocomplex can be successfully used for the photodegradation of pharmaceutical contaminants.

GO-CuO nanocomposites assimilated into CA-PES polymer membrane in adsorptive removal of organic dyes from wastewater

Textile industries are one of the leading environmental pollutants by releasing harmful dye effluents. In many textile distrts, the amount of excess color in treated textile effluent that exceeds regulatory limitations is still being a major concern. The combining usage of nanomaterials and polymer material to solve these issues using various techniques. In this research, graphene oxide-copper oxide (GO-CuO) nanomaterial have been incorporated into cellulose-acetate (CA), poly-ether sulfone (PES) blend polymer by using phase inversion process to fabricate thin film nanocomposite (TFN) membrane for removal of dye pollutant. The physiochemical properties of prepared TFN materials were studied by Fourier transform infra-red spectroscopy (FT-IR), X-ray diffractometer (XRD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), thermo gravimetric analysis (TGA), and mechanical strength analysis. Dye adsorption experiments were performed with four typical water-soluble organic dyes methylene blue (MB), rhodamine blue (Rh. B), methyl orange (MO) and Congo red (CR). After reaching adsorption equilibrium, the composite membrane final removal effectiveness for MB 92.42%, Rh. B 89.39%, CR 68.39%, and MO 58.82% respectively. As a result, the fabricated TFN material proves to be an effective adsorbent material for cationic dye molecules. Also, when the fabricated material was tested with textile industry effluent sample, all physio-chemical properties exhibited a considerable decrease in concentrations when compared to the real textile effluent concentration. The treated effluents permitted for a relatively greater growth and germination index of Tropical amaranth roots than the textile effluent, this demonstrates that phytotoxicity testing was also successful. The most effective temperature, concentration and pH were found to be 273 K, 1 × 10^-5 M and pH 9. The fabricated TFN membrane material (GO-CuO @ CA-PES) can be recommended for water treatment applications.

Aerogels based on cationically modified chitosan and poly(vinyl alcohol) for efficient capturing of viruses

In this study, we developed a new filtering bioaerogel based on linear polyvinyl alcohol (PVA) and the cationic derivative of chitosan (N-[(2-hydroxy-3-trimethylamine) propyl] chitosan chloride, HTCC) with a potential antiviral application. A strong intermolecular network architecture was formed thanks to the introduction of linear PVA chains, which can efficiently interpenetrate the glutaraldehyde(GA)-crosslinked HTCC chains. The morphology of the obtained structures was examined using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The aerogels and modified polymers' elemental composition (including the chemical environment) was determined using X-ray photoelectron spectroscopy (XPS). New aerogels with more than twice as much developed micro- and mesopore space and BET-specific surface area were obtained concerning the starting sample chitosan aerogel crosslinked by glutaraldehyde (Chit/GA). The results obtained from the XPS analysis showed the presence of cationic 3-trimethylammonium groups on the surface of the aerogel, which can interact with viral capsid proteins. No cytotoxic effect of HTCC/GA/PVA aerogel was also observed on fibroblast cells of the NIH3T3 line. Furthermore, the HTCC/GA/PVA aerogel has been shown that efficiently traps mouse hepatitis virus (MHV) from suspension. The presented concept of aerogel filters for virus capture based on modified chitosan and polyvinyl alcohol has a high application potential.

Use of Anionic Surfactant-Modified Activated Carbon for Efficient Adsorptive Removal of Crystal Violet Dye

Studies have been carried out to investigate the removal of crystal violet (CV) cationic dye by using rice husk which was used as a raw material to prepare activated carbon (AC) and it was treated with anionic surfactant. In this process, AC was treated with three different anionic surfactants, namely, lauryl sulfate ACMAS, ACSDS, and ACHTAB. Characterization and analysis of optimum ACMAS were done using different techniques which were used which proves the adsorption of the dye by ACMAS. Effects of various physical parameters like time of contact, additive salts, initial dye concentration, effect of pH, and effect of adsorbent dose were studied. Minute changes in the dye removal capacity were observed due to the presence of various cations. Cations like NO2- caused an increase in the capacity of adsorption but cations like Fe2+decreased the capacity of adsorption in the sample solution. The effectiveness of film diffusion and intraparticle has been shown by mass transfer parameters. The various kinetic studies have shown that pseudo second-order kinetic study best suited with the experimental data. Error analysis and studies of isotherms have shown that the adsorption equilibrium was controlled by Langmuir isotherm study with maximum CV dye adsorption capacity of 235.7 mg/g. Thermodynamics studies revealed endothermicity of the process with negative $\Delta G$ values and positive $\Delta S$ and $\Delta H$ values. Activation energy of 48.31 kJ/mol suggested chemisorption process of the system. Column studies were carried out by using different models to study the variation of bed depth, dye concentration, flow rate, etc. Regeneration experiments have given the ability of the adsorbent to be reused. In this present study, it has been noticed that the use of anionic surfactant-treated activated carbon significantly improved the adsorption of dye and this is a process of adsorption in which not much attention has been given for research till date.

Fabrication of attapulgite-based dual responsive composite hydrogel and its efficient adsorption for methyl violet

In this work, attapulgite (ATP)-based dual sensitive poly (N-isopropylacrylamide-co-acrylic acid) composite hydrogel, P(NIPAM-co-AA)/ATP, was prepared by free radical polymerization. The prepared composite hydrogel was characterized via methods of scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), zeta potential analysis and Brunauer, Emmett, and Teller (BET) etc. The composite hydrogel showed pH and temperature sensitive behaviour, with lower critical solution temperature (LCST) of 35°C and highest swelling occurred at pH 8.0. The adsorption of methyl violet (MV) can be controlled by the hydrogel responsiveness, and 95.78% of MV can be removed at pH 8.0 and 35°C. The addition of a small amount of ATP (3 Wt%) can improve the swelling ratio and adsorption capacity. Kinetic analysis demonstrated that the experimental data were best fitted to the pseudo-second order model. Isotherm analysis showed that the equilibrium data followed Langmuir model with the adsorption capacity of 168.35 mg g^-1. In addition, the composite hydrogel has high adsorption selectivity for cationic dyes, and MV-loaded hydrogel is easy to regenerate, which can be used for successive adsorption cycles. These results demonstrate that the composite hydrogel has potential application in dye wastewater treatment.

Microalgae and bio-polymeric adsorbents: an integrative approach giving new directions to wastewater treatment

This review analyses the account of biological (microalgae) and synthetic (bio-polymeric adsorbents) elements to compass the treatment efficiencies of various water pollutants and mechanisms behind them. While considering pollutant removal, both techniques have their own merits and demerits. Microalgal-based methods have been dominantly used as a biological method for pollutant removal. The main limitations of microalgal methods are capacity, scale, dependence on variables of environment and duration of the process. Biopolymers on the other hand are naturally produced, abundant in nature, environmentally safe and biocompatible with cells and many times biodegradable. Algal immobilization in biopolymers has promoted the reuse of cells for further treatment and protected cells from toxic environment monitoring and controlling the external factors like pH, temperature and salinity can promote the removal process while working with the mentioned technologies. In this review, a mechanistic view of both these techniques along with integrated approaches emphasizing on their loopholes and possibilities of improvement in these techniques is represented. In addition to these, the review also discusses the post-treatment effect on algal cells which are specifically dependent on pollutant type and their concentration. All these insights will aid in developing integrated solutions to improve removal efficiencies in an environmentally safe and cost-effective manner.Novelty statement The main objective of this review is to thoroughly understand the role of micro-algal cells and synthetic adsorbents individually as well as their integrative effect in the removal of pollutants from wastewater. Many reviews have been published containing information related to either removal mechanism by algae or synthetic adsorbents. While in this review we have discussed the agents, algae and synthetic adsorbents along with their limitations and explained how these limitations can be overcome with the integration of both the moieties together in process of immobilization. We have covered both the analytical and mechanistic parts of these technologies. Along with this, the post-treatment effects on algae have been discussed which can give us a critical understanding of algal response to pollutants and by-products obtained after treatment. This review contains three different sections, their importance and also explained how these technologies can be improved in the future aspects.

Mathematical modeling of cinnamon (Cinnamomum verum) bark oil release from agar/PVA biocomposite film for antimicrobial food packaging: The effects of temperature and relative humidity

Antimicrobial biocomposite films were prepared using agar (AG) and polyvinyl alcohol (PVA) as polymer matrix materials and cinnamon bark oil (CBO) as antimicrobial agent. AG and PVA were blended with different mixing ratios. The addition of AG improved the overall water resistance properties of the composite films. To evaluate the effects of temperature and relative humidity (RH) on the release kinetics of CBO from films, CBO release kinetics were analyzed under the 9 combinations of temperature and RH. Then, mathematical modeling of obtained data was conducted using Peleg, Ritger-Peppas, and Peppas-Sahlin models to investigate the release mechanisms of CBO. Consequently, the CBO release rate proportionally increased with the temperature and RH, with the RH being the main factor affecting the release behavior of CBO. In vitro antimicrobial activity tests against gram-positive and gram-negative bacteria showed that the developed composite films have high applicability as an antimicrobial food packaging material.

Adsorption of Crystal Violet Dye Using Activated Carbon of Lemon Wood and Activated Carbon/Fe3O4 Magnetic Nanocomposite from Aqueous Solutions: A Kinetic, Equilibrium and Thermodynamic Study

Activated carbon prepared from lemon (Citrus limon) wood (ACL) and ACL/Fe₃O₄ magnetic nanocomposite were effectively used to remove the cationic dye of crystal violet (CV) from aqueous solutions. The results showed that Fe₃O₄ nanoparticles were successfully placed in the structure of ACL and the produced nanocomposites showed superior magnetic properties. It was found that pH was the most effective parameter in the CV dye adsorption and pH of 9 gave the maximum adsorption efficiency of 93.5% and 98.3% for ACL and ACL/Fe₃O₄, respectively. The Dubinin–Radushkevich (D-R) and Langmuir models were selected to investigate the CV dye adsorption equilibrium behavior for ACL and ACL/Fe₃O₄, respectively. A maximum adsorption capacity of 23.6 and 35.3 mg/g was obtained for ACL and ACL/Fe₃O₄, respectively indicating superior adsorption capacity of Fe₃O₄ nanoparticles. The kinetic data of the adsorption process followed the pseudo-second order (PSO) kinetic model, indicating that chemical mechanisms may have an effect on the CV dye adsorption. The negative values obtained for Gibb’s free energy parameter (−20 < ΔG < 0 kJ/mol) showed that the adsorption process using both types of the adsorbents was physical. Moreover, the CV dye adsorption enthalpy (ΔH) values of −45.4 for ACL and −56.9 kJ/mol for ACL/Fe₃O₄ were obtained indicating that the adsorption process was exothermic. Overall, ACL and ACL/Fe₃O₄ magnetic nanocomposites provide a novel and effective type of adsorbents to remove CV dye from the aqueous solutions.

Theoretical and Experimental Optimization of the Graft Density of Functionalized Anti-Biofouling Surfaces by Cationic Brushes

Diseases and complications related to catheter materials are severe problems in biomedical material applications, increasing the infection risk and medical expenses. Therefore, there is an enormous demand for catheter materials with antibacterial and antifouling properties. Considering this, in this work, we developed an approach of constructing antibacterial surfaces on polyurethane (PU) via surface-initiated atom transfer radical polymerization (SI-ATRP). A variety of cationic polymers were grafted on PU. The biocompatibility and antifouling properties of all resulting materials were evaluated and compared. We also used a theoretical algorithm to investigate the anticoagulant mechanism of our PU-based grafts. The hemocompatibility and anti-biofouling performance improved at a 86–112 μg/cm² grafting density. The theoretical simulation demonstrated that the in vivo anti-fouling performance and optimal biocompatibility of our PU-based materials could be achieved at a 20% grafting degree. We also discuss the mechanism responsible for the hemocompatibility of the cationic brushes fabricated in this work. The results reported in this paper provide insights and novel ideas on material design for applications related to medical catheters.

Agar-reduced graphene oxide selectively adsorbs organic dyes and strengthens double-network hydrogels

A straightforward and environmentally friendly method for synthesizing agar-reduced graphene oxide (ArGO) was devised. The topological features and emergent physical properties displayed by the novel carbon material were controlled by varying its water content. Dehydrated films of ArGO were found to be stable in water due to the π–π stacking interactions that formed between the aromatic components of its constituent sheets. In contrast, porous variants of ArGO afforded hydrogels that exhibited high swelling capacities. The intrinsic mechanical strength, elasticity and chemical stability of the hydrogels were further enhanced through adaption into double-network analogues. Such hydrogels, which were prepared using a facile and efficient one-pot methodology, exhibited a high fracture stress upon compression, and retained their shape in basic aqueous environments. These features can be expected to enable water purification and tissue engineering applications, among others.

Agar-reduced graphene oxide was conveniently synthesized from readily available precursors and found to selectively adsorb cationic organic dyes as well as to enhance the mechanical properties exhibited by various types of double-network hydrogels.