In Situ Attachment of Acrylamido Sulfonic Acid-Based Monomer in Terpolymer Hydrogel Optimized by Response Surface Methodology for Individual and/or Simultaneous Removal(s) of M(III) and Cationic Dyes

Synthesis and Characterization of Triticale Starch-Based Hydrogel for pH Responsive Controlled Diffusion

Considering the FAO perspectives for agriculture toward 2030, many natural sources will be no longer profitable for the synthesis of many biomaterials. Triticale (X Triticosecale Wittmack) is a cereal crop synthesized to withstand those marginal conditions; however, it is primarily used as fodder worldwide. We reported for the first time the synthesis of a natural anionic hydrogel with gastrointestinal pH stimulus-response as a new alternative of smart material, based on Eronga triticale starch as sustainable biomass, using citrate (pK a ∼3.1, 4.7, and 6.4) as cross-linking agent. The scanning electron microscopy and X-ray diffraction exhibited A and B-type starch granules, and semicrystallinity A-type. The presence of the anionic sensing group (COOH) was verified by infrared spectroscopy, the interactions by hydrogen bonds between starch and glycerol and esterification between starch and citric acid were identified by 1H NMR spectra, and through thermal analysis hydrogels exhibited four endothermic curves (179-319 °C, ∼0.711-39 kJ/mol E a). The results showed that the slight addition of glycerol increases the thermal stability, but a higher amount of glycerol decreases the intermolecular forces affecting the thermal stability contrary, the mechanical properties could be benefited. The rheological analyses showed viscoelastic tendency (G' > G″) with high stability (Tanδ < 1) in frequency, time, and strain sweeps. Gastrointestinal pH sensitivity (∼2-7.8) was verified (α ≤ 0.01) following Fick's diffusive parameters, which resulted in a tendency to gradually release BSA with increasing pH ∼3-7 by anomalous and case-II diffusion, showing greater release at pH ∼7.8/3.5 h (80-96%). We aim to expand the biomaterials area focusing on triticale starch due to its limited reported investigations, low-cost, green modification, and its rheological performance as plastic.

Starch-based hydrogels for environmental applications: A review

Water sources have become extremely scarce and contaminated by organic and inorganic industrial and agricultural pollutants as well as household wastes. Poisoning water resources by dyes and metals is a problem because contaminated water can leak into subsurface and surface sources, causing serious contamination and health problems. Therefore, developing wastewater treatment technologies is valuable. Today, hydrogels have attracted considerable attention owing to their broad applications. Hydrogels are polymeric network compositions with significant water-imbibing capacity. Hydrogels have potential applications in diverse fields such as biomedical, personal care products, pharmaceuticals, cosmetics, and biosensors. They can be prepared by using natural (biopolymers) and synthetic polymers. Synthetic polymer-based hydrogels obtained from petrochemicals are not environmentally benign; thus, abundant plant-based polysaccharides are found as more suitable compounds for making biodegradable hydrogels. Polysaccharides with many advantages such as non-toxicity, biodegradability, availability, inexpensiveness, etc. are widely employed for the preparation of environmentally friendly hydrogels. Polysaccharides-based hydrogels containing chitin, chitosan, gum, starch (St), etc. are employed to remove pollutants, metals, and dyes. Among these, St has attracted a lot of attention. St can be mixed with other compounds to make hydrogels, which remove dyes and metal ions to variable degrees of efficiency. Although St has numerous advantages, it suffers from drawbacks such as low stability, low water solubility, and fast degradability in water which limit its application as an environmental adsorbent. As an effective way to overcome these weaknesses, various modification approaches to form starch-based hydrogels (SBHs) employing different compounds have been reported. The preparation methods and applications of SBH adsorbents in organic dyes, hazardous materials, and toxic ions elimination from water resources have been comprehensively discussed in this review.

Synthesis and Evaluation of Alginate-Based Nanogels as Sustained Drug Carriers for Caffeine

The objective of this study is to design a polymeric network of nanogels for sustained release of caffeine. Therefore, alginate-based nanogels were fabricated by a free-radical polymerization technique for the sustained delivery of caffeine. Polymer alginate was crosslinked with monomer 2-acrylamido-2-methylpropanesulfonic acid by crosslinker N',N'-methylene bisacrylamide. The prepared nanogels were subjected to sol-gel fraction, polymer volume fraction, swelling, drug loading, and drug release studies. A high gel fraction was seen with the increasing feed ratio of polymer, monomer, and crosslinker. Greater swelling and drug release were observed at pH 4.6 and 7.4 as compared to pH 1.2 due to the deprotonation and protonation of functional groups of alginate and 2-acrylamido-2-methylpropanesulfonic acid. An increase was observed in swelling, loading, and release of the drug with the incorporation of a high feed ratio of polymer and monomer, while a reduction was seen with the increase in crosslinker feed ratio. Similarly, an HET-CAM test was used to evaluate the safety of the prepared nanogels, which showed that the prepared nanogels have no toxic effect on the chorioallantoic membrane of fertilized chicken eggs. Similarly, different characterizations techniques such as FTIR, DSC, SEM, and particle size analysis were carried out to determine the development, thermal stability, surface morphology, and particle size of the synthesized nanogels, respectively. Thus, we can conclude that the prepared nanogels can be used as a suitable agent for the sustained release of caffeine.

Probing the structure-antioxidant activity relationships of four cinnamic acids porous starch esters

For investigation of antioxidant capacity relationship, four cinnamic acids (CNAs), including cinnamic (CA), ferulic (FA), p-coumaric (p-CA) and sinapic (SA) acids, were selected to modify porous starch (PS) with different degrees of substitution by esterification, respectively. The ester linkage of CNAs modified PS was confirmed by ¹H NMR, ¹³C solid-state NMR and FT-IR. The porous structure was maintained after esterification. Three in vitro antioxidant assays were applied to measure antioxidant capacities. The order of antioxidant capacity was SA@PS > FA@PS > p-CA@PS > CA@PS, due to the presence of phenolic hydroxyl groups with hydrogen donating abilities. Besides electron-donating group on ortho or para positions the benzene ring further enhances the hydrogen donating ability and the stability of hydroxyl radical. This study not only investigated the antioxidant mechanism of CNA modified starch derivatives but probed the way for synthesis of biodegradable antioxidant materials for the food industries.

Light-Emitting Multifunctional Maleic Acid-co-2-(N-(hydroxymethyl)acrylamido)succinic Acid-co-N-(hydroxymethyl)acrylamide for Fe(III) Sensing, Removal, and Cell Imaging

The intrinsically fluorescent highly hydrophilic multifunctional aliphatic terpolymer, maleic acid (MA)-co-2-(N-(hydroxymethyl)acrylamido)succinic acid (NHASA)-co-N-(hydroxymethyl)acrylamide (NHMA), that is, 1, was designed and synthesized via C-C/N-C-coupled in situ allocation of a fluorophore monomer, that is, NHASA, composed of amido and carboxylic acid functionalities in the polymerization of two nonemissive MA and NHMA. The scalable and reusable intrinsically fluorescent biocompatible 1 was suitable for sensing and high-performance adsorptive exclusion of Fe(III), along with the imaging of Madin-Darby canine kidney cells. The structure of 1, in situ fluorophore monomer, aggregation-induced enhanced emission, cell-imaging ability, and superadsorption mechanism were studied via microstructural analyses using 1H/13C NMR, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, atomic absorption spectroscopy, ultraviolet-visible spectroscopy, thermogravimetric analysis, dynamic light scattering, high-resolution transmission electron microscopy, solid-state fluorescence, fluorescence lifetime, and fluorescence imaging, along with measuring kinetics, isotherms, and thermodynamic parameters. The location, electronic structures, and geometries of the fluorophore and absorption and emission properties of 1 were investigated using density functional theory and natural transition orbital analyses. The limit of detection and the maximum adsorption capacity were 2.45 × 10-7 M and 542.81 mg g-1, respectively.

Synthesis, characterization and photo-catalytic activity of guar-gum-g-aliginate@silver bionanocomposite material

The green mechanism for the synthesis of nanoparticles and their application to the wastewater treatment is of inordinate curiosity to the research community. Herein we outline a novel method for the synthesis of silver nanoparticles via a green route using alginate-guar gum blend (GG-Alg@Ag) and their application to degrade methylene blue (MB) dye. The synthesized material was characterized by FTIR, XRD, SEM-EDX, TEM, TGA-DTG, AFM, and UV-vis techniques. A combination of RSM and CCD was employed to compute the system and optimized values of various interacting parameters such as exposure time (120 min), pH (4.98), dye concentration (194 mg L⁻¹), and catalyst dose (0.07 g) with a photodegradation capacity of 92.33% and desirability 1.0. The mechanism of degradation reaction was best elucidated by the pseudo-second-order model suggesting chemical deposition of MB on the GG-Alg@Ag surface through followed by the reduction mechanism in the occupancy of visible light. The optical studies indicated a value of 2.5 eV by Tauc's plot for bandgap energy (E_g) for GG-Alg@Ag bionanocomposite.

The green mechanism for the synthesis of nanoparticles and their application to the wastewater treatment is of inordinate curiosity to the research community.

Bentonite-Acrylamide Hydrogels Prepared by the Nonmixing Method: Characterization and Properties

A significant amount of research has been conducted on bentonite-acrylamide hydrogels. These gels are usually prepared by uniformly mixing bentonite with reactive monomers. Herein, a new preparation method of bentonite-acrylamide hydrogels has been proposed to cater to one novel application of bentonite-acrylamide hydrogels. In this method, bentonite-acrylamide hydrogel was obtained by pressing bentonite into a thin mud cake and extruding a mixed liquor of acrylamide, a cross-linking agent, an initiator, and water into the thin mud cake and then subjecting the system to water-bath curing. The effects of extrusion pressure, extrusion time, and acrylamide concentration on the tensile strength and elemental composition of bentonite-acrylamide hydrogel were investigated. The results show that the tensile strength of the bentonite-acrylamide hydrogel first increased and then tended to be stable with the further increase in extrusion pressure and extrusion time. As the concentration of acrylamide increased, the tensile strength of the bentonite-acrylamide hydrogel increased first and then decreased slightly. With the increase in extrusion pressure, extrusion time, and acrylamide concentration, the contents of C and N elements in the thin mud cake gradually increased and then tended to be stable, which reflects the state of the monomer entering the thin mud cake. In addition, the elemental composition of the bentonite-acrylamide hydrogel was analyzed via the scanning electron microscopy-energy dispersive X-ray spectrometry method, and it was found that the composition of the hydrogel was relatively uniform in the direction of mixed liquor extrusion.

Magnetic Hierarchically Macroporous Emulsion-Templated Poly(acrylic acid)-Iron Oxide Nanocomposite Beads for Water Remediation

Tainting of waterbodies with noxious industrial waste is the gravest environmental concern of the day that continues to wreak inevitable havoc on human health. To cleanup these hard-to-remove life-threatening water contaminants, we have prepared hierarchically porous poly(acrylic acid) beads by emulsion templating. These emulsion-templated macroporous polymer beads not only mediate the synthesis of Fe₃O₄ nanoparticles inside their porous network using a coprecipitation approach but, in turn, create diverse anchoring sites to immobilize an additional poly(acrylic acid) active layer onto the nanocomposite beads. These post-synthetically modified nanocomposite beads with macropores and abundant acrylic acid moieties offer the ready mass transfer and fair advantage of relatively higher overall negative charge to efficiently adsorb lead [Pb(II)] and crystal violet with impressive performance-even superior to many of the materials explored in this regard so far. Furthermore, the strong entanglement of nanoparticles in the porous polymeric scaffolds tackles the curb of trade-off between all-round effective remediation and secondary pollution and the millimeter size eases their processing and recovery during the adsorption tests, thereby making these materials practically worthwhile.

Structures, Properties, and Performances-Relationships of Polymeric Membranes for Pervaporative Desalination

For the fulfilment of increasing global demand and associated challenges related to the supply of clean-and-safe water, PV has been considered as one of the most attractive and promising areas in desalinating salty-water of varied salinities. In pervaporative desalination, the sustainability, endurance, and structural features of membrane, along with operating parameters, play the dominant roles and impart paramount impact in governing the overall PV efficiency. Indeed, polymeric- and organic-membranes suffer from several drawbacks, including inferior structural stability and durability, whereas the fabrication of purely inorganic membranes is complicated and costly. Therefore, recent development on the high-performance and cost-friendly PV membrane is mostly concentrated on synthesizing composite- and NCP-membranes possessing the advantages of both organic- and inorganic-membranes. This review reflects the insights into the physicochemical properties and fabrication approaches of different classes of PV membranes, especially composite- and NCP-membranes. The mass transport mechanisms interrelated to the specialized structural features have been discussed. Additionally, the performance potential and application prospects of these membranes in a wide spectrum of desalination and wastewater treatment have been elaborated. Finally, the challenges and future perspectives have been identified in developing and scaling up different high-performance membranes suitable for broader commercial applications.