Fabrication of stable superabsorbent hydrogels for successful removal of crystal violet from waste water

Synthesis and characterization of copper nanoparticle-based hydrogel and its applications in catalytic reduction and adsorption of basic blue 3

Most of the dyes used in various industries are non-biodegradable and carcinogenic in nature. Therefore, elimination of dyes from textile wastes is mandatory to safeguard the life of human, aquatic animals and aquatic plants. In this connection an effective and eco-friendly hydrogel was synthesized from acrylamide, cellulose, clay, and copper salt abbreviated as AMPS(PHE-Ce)/MC-Cu. The fabricated hydrogel was used as sorbent and catalyst for the adsorption and catalytic reduction of basic blue 3. SEM analysis showed granular texture with small holes or cracks which is basic criteria for an adsorbent surface. The results showed that the BET surface area and the Langmuir surface area were, respectively, 27.87 and 40.32 m2/g. The FTIR analysis confirmed the synthesis of hydrogel, as is evident from peaks at 3500, 3439, 2996, 2414, and 1650 cm-1, which indicated the presence of OH or NH, -C-O-C-, CH3, (C[bond, double bond]O), C-N bonds correspondingly. Thermal stability was confirmed by TGA analysis where weight loss in three stages has been observed. The presence of copper was confirmed through EDX (5.02%) indicating the incorporation of cupper nanoparticles in hydrogel surface. The high adsorption capability of 1590 mg/g as recorded for basic blue-3 dye indicates it to be an efficient adsorbent. The swelling behavior characterized by Fickian diffusion up to 7898% clearly indicated significant swelling. Pseudo 2nd-order kinetics and the Langmuir isotherm models were more fit in unfolding kinetics and isothermal data indicating chemisorption with monolayer sorption as evident from the high R2 values (0.999) of each model. Thermodynamics considerations indicated that the adsorption process is endothermic with a positive enthalpy value of 1371.32 Jmol-1. The positive entropy value of 19.70 J/mol.K signifies a higher degree of disorder at the solid-liquid interface. The findings provided a valuable insights into the hydrogel's capacity to adsorb cationic dyes and reduce them catalytically, pointing towards its potential applications in addressing environmental challenges.

Synthesis of Poly(GG-co-AAm-co-MAA), a Terpolymer Hydrogel for the Removal of Methyl Violet and Fuchsin Basic Dyes from Aqueous Solution

A novel adsorbent designated as terpolymer hydrogel (gellan gum-co-acrylamide-co-methacrylic acid) was prepared by free radical polymerization of gellan gum (GG), methacrylic acid (MAA), and acrylamide (AAm) using N,N-methylene bis-acrylamide (MBA) as cross-linker and ammonium per sulfate (APS) as the initiator of the reaction. The synthesized gel was characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and thermogravimetric analysis (TGA) and was used for the adsorptive removal of methyl violet (MV) and Fuchsin Basic (FB) dyes from aqueous solution. The effect of temperature, contact time, pH, and concentration on them under the study adsorption process was evaluated. Freundlich isotherm and pseudo-second-order kinetic models were found to be best in fitting the isothermal and kinetics data. The water diffusion and % swelling of hydrogel were studied at various pH in distilled water and at neutral pH in tap water. The diffusion was found to be of Fickian type with a maximum swelling of 5132%. The maximum adsorption capacity was 233 mg/g against MV and 200 mg/g against FB dyes. The swelling and adsorption were pH dependent and increased with increase in pH. The enthalpy, Gibbs free energy, and entropy changes of adsorption for both the dyes indicated the adsorption process to be exothermic, feasible, and spontaneous. The hydrogel was successfully regenerated using acetone and distilled water for five cycles and still, its dye removal efficiency was 80% of its original value. The poly(GG-co-AAm-co-MAA) hydrogel successfully removed the selected dyes from water and could thus be used as an efficient alternative sorbent for cationic dye removal from aqueous solutions.

Sponge-like biodegradable polypyrrole-modified biopolymers for selective adsorption of basic red 46 and crystal violet dyes from single and binary component systems

Recently, several researchers have been trying to reduce the ecological effects of water pollution by considering the use of biodegradable materials that prevent the generation of secondary pollution in our environment and enable water reuse. Here, new biodegradable hydrogels based on alginate (Alg), gelatin (Gel) and polypyrrole (PPy) were successfully implemented to remove two known highly toxic cationic dyes from wastewater. The design process was performed in two steps: in-situ polymerization of polypyrrole within the Alg/Gel mixture, followed by hydrogel formation. Biocomposites showed promising efficacy for the removal of both basic red 46 (BR46) and crystal violet (CV) dyes from real and demineralized water samples. However, Alg-Gel-PPy hydrogel showed better selectivity for BR46 than for CV as compared to the pristine Alg-Gel hydrogel. Adsorption of both pollutants on biocomposite hydrogel beads followed the Langmuir isotherm and pseudo-second order kinetic models. Besides, the highest adsorption capacities (125 mg g-1 for BR46 and 88.5 mg g-1 for CV) were obtained for the Alg-Gel-PPy hydrogel, compared with those determined for PPy-free hydrogel (103.09 mg g-1 for BR46 and 86.96 mg g-1 for CV) and remained at a satisfactory level for five adsorption-desorption cycles. Finally, the obtained hydrogels showed excellent biodegradability by natural soil microorganisms, with 91 % decomposition.

Activated Carbon-Incorporated Tragacanth Gum Hydrogel Biocomposite: A Promising Adsorbent for Crystal Violet Dye Removal from Aqueous Solutions

Biomaterials-based adsorbents have emerged as a sustainable and promising solution for water purification, owing to their eco-friendly nature and remarkable adsorption capacities. In this study, a biocomposite hydrogel was prepared by the incorporation of activated carbon derived from pomegranate peels (PPAC) in tragacanth gum (TG). The hydrogel biocomposite (PPAC/TG) showed a porous structure, a negative surface charge at a pH of more than 4.9, and good stability in aqueous media. The adsorption properties of the PPAC/TG hydrogel biocomposite were assessed for the removal of crystal violet dye (CV) from aqueous solutions using a batch adsorption. The equilibrium adsorption data followed the Sips isotherm model, as supported by the calculated R2 (>0.99), r-χ2 (<64), and standard error values (<16). According to the Sips model, the maximum values of the adsorption capacity of PPAC/TG were 455.61, 470.86, and 477.37 mg/g at temperatures of 25, 30, and 35 °C, respectively. The adsorption kinetic of CV onto the PPAC/TG hydrogel biocomposite was well described by the pseudo-second-order model with R2 values more than 0.999 and r-χ2 values less than 12. Thermodynamic studies confirmed that the CV dye adsorption was spontaneous and endothermic. Furthermore, the prepared hydrogel exhibited excellent reusability, retaining its adsorption capacity even after being used more than five times. Overall, this study concludes that the prepared PPAC/TG exhibited a significant adsorption capacity for cationic dyes, indicating its potential as an effective and eco-friendly adsorbent for water treatment.

Exploiting High-Voltage Stability of Dual-Ion Aqueous Electrolyte Reinforced by Incorporation of Fiberglass into Zwitterionic Hydrogel Electrolyte

Rechargeable zinc aqueous batteries are key alternatives for replacing toxic, flammable, and expensive lithium-ion batteries in grid energy storage systems. However, these systems possess critical weaknesses, including the short electrochemical stability window of water and intrinsic fast zinc dendrite growth. Hydrogel electrolytes provide a possible solution, especially cross-linked zwitterionic polymers that possess strong water retention ability and high ionic conductivity. Herein, an in situ prepared fiberglass-incorporated dual-ion zwitterionic hydrogel electrolyte with an ionic conductivity of 24.32 mS cm-1 , electrochemical stability window up to 2.56 V, and high thermal stability is presented. By incorporating this hydrogel electrolyte of zinc and lithium triflate salts, a zinc//LiMn0.6 Fe0.4 PO4 pouch cell delivers a reversible capacity of 130 mAh g-1 in the range of 1.0-2.2 V at 0.1C, and the test at 2C provides an initial capacity of 82.4 mAh g-1 with 71.8% capacity retention after 1000 cycles with a coulombic efficiency of 97%. Additionally, the pouch cell is fire resistant and remains safe after cutting and piercing.

Novel hydrogel poly (GG-co-acrylic acid) for the sorptive removal of the color Rhodamine-B from contaminated water

Textile effluent's treatment is highly desired due to the presence of hazardous, water-soluble and non-biodegradable dyes that not only have harmful effect on the environment but on living beings as well. Treatment of these pollutants by sorption through biosorbents is considered to be a best method of choice due to greener nature of the processes. In this connection hydrogel sorbents might be an intriguing option due to its straightforward application, great efficacy, easy synthesis, rapid turnaround, and potential of recycling. Herein, novel hydrogel was prepared using Gellan Gum and acrylic acid (GG-co-AAc) which were then characterized by instrumental techniques like UV/visible and FTIR spectroscopy, SEM, EDX and XRD. The anionic hydrogel's adsorption capacity, swelling behavior, and sorption potential were determined using Rhodamine-B as potential environmental pollutant. The hydrogel exhibited an impressive adsorption capacity of 1250 mg/g. Swelling experiments were performed in Milli-Q distilled water at different pH levels, reaching maximum swelling of 3230% after 23 h as determined through Fickian diffusion. At pH 7, the anionic hydrogel's sorption potential was thoroughly studied in the subsequent experiments. The adsorption process was found to follow the Langmuir isotherm, indicating a monolayer adsorption mechanism supported by higher R2 values compared to the Freundlich isotherm. Thermodynamic analysis revealed the exothermic nature of the adsorption process, with a negative enthalpy value of -11371 KJmol-1 and negative entropy value of -26.39 Jmol-1K-1, suggesting a less ordered system. These findings provide valuable insights into the adsorption characteristics and potential applications of the synthesized anionic hydrogel.

Starch Biocryogel for Removal of Methylene Blue by Batch Adsorption

A green monolithic starch cryogel was prepared and applied for the removal of methylene blue (MB) using a batch system. The influence of various experimental parameters on MB adsorption was investigated. High removal efficiency (81.58 ± 0.59%) and adsorption capacity (34.84 mg g^-1) were achieved. The Langmuir model better fitted the experimental data (determination coefficient (R²) = 0.9838) than the Freundlich one (R² = 0.8542), while the kinetics of MB adsorption on the cryogel followed a pseudo-second-order model. The adsorption process was spontaneous and endothermic with an activation energy of 37.8 kJ mol^-1 that indicated physical adsorption. The starch cryogel was used for MB removal from a wastewater sample collected from a local Batik production community enterprise in Phuket, Thailand, and a removal efficiency of 75.6% was achieved, indicating that it has a high potential as a green adsorbent for MB removal.

Sugar-Based Phase-Selective Supramolecular Self-Assembly System for Dye Removal and Selective Detection of Cu2+ Ions

Simple, effective, and eco-friendly sugar-based phase-selective gelators were synthesized at a low cost. They showed high gelling ability toward a wide range of solvents at lower concentrations (minimum gelation concentration ∼0.3%). Preliminary tests reveal that these low molecular weight organogelators can immediately and phase-selectively gel benzene, toluene, petrol, and kerosene in water at room temperature. We also identified G13 in toluene as the good gelator, and the corresponding organogel proficiently removes water-soluble dyes from their concentrated aqueous solutions. This efficient removal of toxic organic solvents and dyes from water suggests promising applications in removing organic substances from contaminated water resources. The thermoreversible gel exhibits effective rechargeability up to five cycles of burning and gelation, which imply the flame stability of the gel. Interestingly, these compounds had a high detection ability toward Cu²⁺ ions with a state change from gel to the solution. The physical justification for gelation mechanisms and the molecular interaction with metal ions were further confirmed by computational studies.

Gellan gum/bacterial cellulose hydrogel crosslinked with citric acid as an eco-friendly green adsorbent for safranin and crystal violet dye removal

In this study, ex-situ crosslinked gellan gum (GG)/bacterial cellulose (BC) hydrogels have been investigated as good absorbents for the removal of safranin and crystal violet dye pollutants. The preparation involves a cost-effective and easy-to-perform crosslinking procedure, using citric acid (CA) as a green crosslinker. The physicochemical and mechanical properties of the crosslinked hydrogels were examined by FTIR, TGA, SEM, XRD, and unconfined compression analyses. The swelling capacity of the hydrogels as a function of pH was investigated. CA depicted to improve structural stability as a crosslinker. The dye removal capacity of the hydrogels as good adsorbents was explored and showed higher efficiency in the removal of safranin dye as compared to crystal violet with optimum adsorption capacities obtained as 17.57 and 13.49 mg/g, respectively. Adsorption kinetics and isotherm models as well as thermodynamics examined. Results showed the adsorption process well fitted the pseudo 2nd-order kinetic and Langmuir-Freundlich models while temperature dependence study depicted to be exothermic. Furthermore, no significant loss of removal efficiency of the hydrogel adsorbent was observed even after five adsorption-desorption cycles. Based on the revealed results, the prepared hydrogel may serve as an effective adsorbent for the removal of dyes from the aqueous phase.

Biobased hydrogels and their composite containing MgMOF74 for the removal of textile dyes and wastewater treatment

In this work, we report the synthesis of a biobased hydrogel comprised of collagen, chitosan, and polyurethane for the removal of textile dyes. The adsorption capacity of this hydrogel was improved by adding a magnesium metal-organic framework to the semi-interpenetrating polymer matrix yielding a composite hydrogel. Removal of Bismarck Brown and Congo red was studied, and the experimental results fit Freundlich's model. Both hydrogel formulations were tested for the removal of textiles dyes from wastewaters. The magnesium-metal organic framework improved the efficiency of the biobased hydrogel for the removal of direct and mordant dyes reaching up to 89 ± 2%. The composite hydrogel was tested for the removal of Congo Red in a fixed bed column observing the breakthrough point after 168 min. Also, a flocculant material was prepared from collagen and chitosan and was tested for the removal of direct red dye from wastewater removing up to 80 ± 1%. The pretreated wastewater by coagulation-flocculation was treated by adsorption yielding a global removal efficiency of 99%. Finally, the studied hydrogels are potentially biodegradable being completely degraded by the proteolytic action after 22 days. PRACTITIONER POINTS: Composite hydrogels of collagen, chitosan, and MgMOF74 removed efficiently textile dyes from wastewater in batch systems and fixed bed columns. A biobased flocculant of collagen and chitosan significantly improved water quality after coagulation flocculation. Hydrogels were reusable for four cycles, and they can be proteolytically degraded after 22 days.

Sargassum fusiforme Polysaccharide-Based Hydrogel Microspheres Enhance Crystal Violet Dye Adsorption Properties

In this study, a polysaccharide-based hydrogel microsphere (SFP/SA) was prepared using S. fusiforme polysaccharide (SFP) and sodium alginate (SA). Fourier transform infrared spectroscopy (FT-IR) demonstrated that SFP was effectively loaded onto the hydrogel microsphere. Texture profile analysis (TPA) and differential scanning calorimetry (DSC) showed that, with the increase of SFP concentration, the hardness of SFP/SA decreased, while the springiness and cohesiveness of SFP/SA increased, and the thermal stability of SFP/SA improved. The equilibrium adsorption capacity of SFP/SA increased from 8.20 mg/g (without SFP) to 67.95 mg/g (SFP accounted 80%) without swelling, and from 35.05 mg/g (without SFP) to 81.98 mg/g (SFP accounted 80%) after 24 h swelling. The adsorption of crystal violet (CV) dye by SFP/SA followed pseudo-first order and pseudo-second order kinetics (both with R2 > 0.99). The diffusion of intraparticle in CV dye was not the only influencing factor. Moreover, the adsorption of CV dye for SFP/SA (SFP accounted 60%) fit the Langmuir and Temkin isotherm models. SFP/SA exhibited good regenerative adsorption capacity. Its adsorption rate remained at > 97% at the 10th consecutive cycle while SFP accounted for 80%. The results showed that the addition of Sargassum fusiforme polysaccharide could increase the springiness, cohesiveness and thermal stability of the hydrogel microsphere, as well as improve the adsorption capacity of crystal violet dye.

Effects of Cu2+/Zn2+ on the electrochemical performance of polyacrylamide hydrogels as advanced flexible electrode materials

Previously, solid-state electrode materials have been utilized for the fabrication of energy storage devices; however, their application is impeded by their brittle nature and ion mobility problems. To address issues faced in such a modern era where energy saving and utility is of prior importance, a novel approach has been applied for the preparation of electrode materials based on polyacrylamide hydrogels embedded with reduced graphene oxide and transition metals, namely, Cu²⁺ and Zn²⁺. The fabricated hydrogel exhibits high electrical properties and flexibility that make it a favorable candidate to be used in energy storage devices, where both elastic and electrical properties are desired. For the first time, a multi-cross-linked polyacrylamide hydrogel was constructed and compared in the presence of other electro-active materials such as reduced graphene oxide and transition metals. Polyacrylamide hydrogels embedded with reduced graphene oxide demonstrate excellent electrical properties such as specific capacitance, least impedance, low phase angle shift and AC conductivity of 22.92 F g^-1, 2115 Ω, 2.88° and 0.67 μδ m^-1 respectively as compared to Cu²⁺- and Zn²⁺-loaded hydrogels, which block all available active sites causing an increase in impedance with a parallel decrease in capacitance. The capacitance retention and coulombic efficiency calculated were 88.22% and 77.23% respectively, indicating high stability up to 150 cycles at 0.1 A g^-1. Storage moduli obtained were 10.52 kPa, which infers the more elastic nature of the hydrogel loaded with graphene oxide than that of other synthesized hydrogels.

Removal of Safranin-T and Toluidine from Water through Gum Arabic/Acrylamide Hydrogel

Hydrogels as “smart sorbents” for wastewater treatment have attracted much attention due to their facile fabrication, rapid regeneration, environment friendly nature, and strong interaction with pollutants. In this study, gum arabic/acrylamide (GA/AM) hydrogel was developed via the free radical polymerization method by employing acrylamide (AM) (monomer), gum arabic (GA) (grafting backbone), N,N-methylenebisacrylamide (MBA) (chemical crosslinker), and tetramethylethylenediamine (TEMED) (accelerator). The fabricated adsorbent was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and surface area analyzer. The adsorption properties of the subject hydrogel were explored against cationic safranin and toluidine dyes in aqueous media. The point of zero charge (PZC) for the GA/AM sorbent was found to be $\text{p}{\text{H}}_{\text{PZC}}=7.1$ whereas maximum sorption occurred at pH 11. Different kinetic and isotherm models were applied to evaluate the adsorption mechanism and estimate values of different adsorption parameters. The adsorption isotherm and kinetics were better explained by the Langmuir isotherm and pseudo-second-order kinetic model whereas the adsorption thermodynamics depicted the endothermic, spontaneous, and favorable nature of the process. The adsorbent was regenerated with acetone and reused for the selected dyes for many cycles. After the 5th cycle, the hydrogel retained safranin/toluidine removal $\text{capacity}\ge 60\%$ which pointed toward the reusability of the prepared adsorbent for cycles without appreciable reduction in its adsorption capacity. Hence, the GA/AM sorbent can be applied as an alternative of activated carbon to treat dye-contaminated waters.

Effective mitigation of single-component and mixed textile dyes from aqueous media using recyclable graphene-based nanocomposite

The present study reported the synthesis and utilization of a graphene-based hybrid nanocomposite (MnFe₂O₄/G) to mitigate several synthetic dyes, including methylene blue, malachite green, crystal violet, and Rhodamine B. This adsorbent was structurally analyzed by several physicochemical techniques such as X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, Raman spectroscopy, N₂ adsorption-desorption isotherm measurement, point of zero charge, and Boehm titrations. BET surface area of MnFe₂O₄/G was measured at 382.98 m²/g, which was substantially higher than that of MnFe₂O₄. MnFe₂O₄/G possessed diverse surface chemistry properties with the presence of many functional groups such as carboxylic acid, phenolic, lactone, and basic groups. MnFe₂O₄/G was used to remove synthetic dyes in the aqueous media. The effect of many factors, e.g., concentration (5-50 mg/L), pH (4-10), dose (5-20 mg), and temperature (25-45 °C) on adsorption performance of MnFe₂O₄/G was conducted. Kinetic, isotherm, intraparticle, and thermodynamic models were adopted for investigating adsorption phenomenon of dyes on MnFe₂O₄/G. The maximum adsorption capacity of dyes over MnFe₂O₄/G was found as Rhodamine B (67.8 mg/g) < crystal violet (81.3 mg/g) < methylene blue (137.7 mg/g) < malachite green (394.5 mg/g). Some tests were performed to remove mixed dyes, and mixed dyes in the presence of antibiotics with total efficiencies of 65.8-87.9% after 120 min. Moreover, the major role of π-π stacking interaction was clarified to gain insight into the adsorption mechanism. MnFe₂O₄/G could recycle up to 4 cycles, which may be beneficial for further practical water treatment.

Swelling and kinetic investigations of basic blue-3 sorption by polyacrylamide/Gum Arabic hybrid hydrogel in aqueous medium

Removal of noxious dyes from waste water is highly desirable for the safety of humans, aquatic life and natural environment. The issue was addressed in the present work by one pot fabrication of polyacrylamide/Gum Arabic (pAAm/GA) composite hydrogel which was applied as sorbent for basic blue-3 (BB3) eradication. The synthesis of the material was confirmed by scanning electron microscopy (SEM), Fourier Transformed Infrared (FTIR) spectroscopy and thermo gravimetric analysis (TGA). Besides, the same techniques also evidenced BB3 uptake by the hydrogel. In distilled water, the swelling capacities of the hydrogel was investigated at pH 7 and the nature of water diffusion into the hydrogel was probed from the resultant data. The composite hydrogel reached equilibrium point in 24 h after which no appreciable water absorption occurred. The adsorption of BB3 by the hybrid material was comprehensively investigated which involved the effect of contact time, temperature and pH on the sorption capacity of the hybrid sorbent. The obtained data fitted well into pseudo second order kinetic model and the adsorption took place in three consecutive kinetic phases. Moreover, sorption thermodynamics revealed non spontaneous and endothermic nature of BB3 sorption accompanied with increase in degree of order.

Nanocomposite hydrogel based on sodium alginate, poly (acrylic acid), and tetraamminecopper (II) sulfate as an efficient dye adsorbent

In this study, a novel nanocomposite hydrogel (NCH) was prepared by in situ crosslinking and radical polymerization of acrylic acid (AA) in the presence of sodium alginate (Na-Alg), followed by loading of Cu²⁺ ions and reaction with ammonia. The main advantage of the synthesized NCH is the high adsorption of dye due to the large contact area. The structure of the NCH was studied by FT-IR spectroscopy, TEM, and SEM. TEM showed that the size of nanoparticles is about 5-30 nm. The adsorption of dye was studied by changing the different factors. The removal efficiency of Crystal Violet (CV) and Malachite Green (MG) was found to be more than 96% at concentration of 10 mg/L and pH = 6. The dye adsorption on the NCH is well described by Freundlich isotherm and pseudo-second-order kinetic models. The reusability experiments showed that about 95% of the initial adsorption was obtained after eight cycles.

A pH-sensitive and sustained-release oral drug delivery system: the synthesis, characterization, adsorption and release of the xanthan gum-graft-poly(acrylic acid)/GO-DCFP composite hydrogel

In this study, graphene oxide (GO) was successfully prepared using the improved Hummers method, and the prepared GO powder was dissolved in distilled water and subjected to ultrasonic stripping. Diclofenac potassium (DCFP) was selected as a model drug to systematically evaluate the adsorption mechanism of DCFP by GO. Different reaction models were constructed to fit the adsorption kinetics and adsorption isotherms of DCFP on GO, in order to further explore the underlying adsorption mechanism. The results demonstrated that the pseudo-second-order kinetic model and Freundlich model could better delineate the adsorption process of DCFP by GO. Both π–π stacking and hydrophobic interaction were mainly involved in the adsorption process, and there were electrostatic interaction and hydrogen bonding at the same time. Then, the xanthan gum-graft-poly(acrylic acid)/GO (XG-g-PAA/GO) composite hydrogel was synthesized by in situ polymerization as a slow-release drug carrier. For this reason, a XG-g-PAA/GO–DCFP composite hydrogel was synthesized, and its in vitro drug release and pharmacokinetic data were assessed. The results showed that the synthesized XG-g-PAA/GO composite hydrogel had a certain mechanical strength and uniform color, indicating that GO is evenly distributed in this composite hydrogel. Moreover, the results of a swelling ratio test demonstrated that the swelling ratios of the XG-g-PAA/GO composite hydrogel were significantly increased with increasing pH values, implying that this material is sensitive to pH. The in vitro drug release experiment showed that the cumulative release of DCFP after 96 h was significantly higher in artificial intestinal fluid than in artificial gastric fluid. These findings indicate that the XG-g-PAA/GO–DCFP composite hydrogel exhibits pH sensitivity under physiological conditions. Besides, the results of in vivo pharmacokinetic analysis revealed that the t_1/2 of DCFP group was 2.03 ± 0.35 h, while that of the XG-g-PAA/GO–DCFP composite hydrogel group was 10.71 ± 2.04 h, indicating that the synthesized hydrogel could effectively prolong the drug action time. Furthermore, the AUC_(0–t) of the DCFP group was 53.99 ± 3.18 mg L⁻¹ h⁻¹, while that of the XG-g-PAA/GO–DCFP composite hydrogel group was 116.79 ± 14.72 mg L⁻¹ h⁻¹, suggesting that the bioavailability of DCFP is greatly enhanced by this composite hydrogel. In conclusion, this study highlights that the XG-g-PAA/GO–DCFP composite hydrogel can be applied as a sustained-release drug carrier.

In this study, graphene oxide (GO) was successfully prepared using the improved Hummers method, and the prepared GO powder was dissolved in distilled water and subjected to ultrasonic stripping.

Biodegradable gelatin composite hydrogels filled with cellulose for chromium (VI) adsorption from contaminated water

Biopolymers are promising materials for water treatment applications due to their abundance, low cost, expandability, and chemical structure. In this work, gelatin hydrogels filled with cellulose in the form of pristine eucalyptus residues (PER) or treated eucalyptus residues (TER) were prepared for adsorption and chromium removal in contaminated water. PER is a lignocellulosic compound, with cellulose, hemicellulose, and lignin, while TER has cellulose as a major component. FT-Raman Spectroscopy and FTIR analysis confirmed the crosslink reaction with glutaraldehyde and indicated that fillers altered the gelatin molecular vibrations and formed new hydrogen bonds, impacting the hydrogels' crystalline structure. The hydrogen bond energy was altered by the cellulosic fillers' addition and resulted in higher thermal stability (~10 °C). Hydrogels presented a Fickian diffusion, where gelatin hydrogel showed the highest swelling ability (466%), and composites showed lower values with the filler content increase. The chromium adsorption capacity presented values between 12 and 13 mg/g, i.e., featuring an excellent removal capacity which is related with hydrogel crosslinked structure and fibers surface hydroxyl groups, highlighting gelatin hydrogel TER 5% with better removal capacity. The developed hydrogels were produced from biomacromolecules with low-cost and potential application in contaminated water.

In-situ stabilization of silver nanoparticles in polymer hydrogels for enhanced catalytic reduction of macro and micro pollutants

The in-situ stabilization of Ag nanoparticles is carried out by the use of reducing agent and synthesized three different types of hydrogen (anionic, cationic, and neutral) template. The morphology, constitution and thermal stability of the synthesized pure and Ag-entrapped hybrid hydrogels were efficiently confirmed using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and thermo gravimetric analysis (TGA). The prepared hybrid hydrogels were used in the decolorization of methylene blue (MB) and azo dyes congo red (CR), methyl Orange (MO), and reduction of 4-nitrophenol (4-NP) and nitrobenzene (NB) by an electron donor NaBH4. The kinetics of the reduction reaction was also assessed to determine the activation parameters. The hybrid hydrogen catalysts were recovered by filtration and used continuously up to six times with 98% conversion of pollutants without substantial loss in catalytic activity. It was observed that these types of hydrogel systems can be used for the conversion of pollutants from waste water into useful products.

Synthesis of copolymeric hydrogels of acrylamide and 2-(hydroxyethyl methacrylate) and its use for the adsorption of basic blue 3 dye

Homo and copolymer hydrogels of acrylamide and 2-hydroxyethyl methacrylate (HEMA) were synthesized by free radical addition polymerization. The synthesized hydrogels were characterized by scanning electron microscopy (SEM), thermal gravimetric and differential thermal analysis (TGA/DTA). The hydrogels were used as an adsorbent for the removal of toxic azo dye Basic blue 3 (BB3) in aqueous medium. To check the swelling property the equilibrium swelling of these synthesized hydrogels were established within 24 h. The effect of pH, time and temperature in the process of BB3 adsorption was studied in detail. The maximum adsorption of BB3 on hydrogels was occurred at pH 9 with 60 min equilibration time. The kinetic data were applied to pseudo first order, pseudo second order and intraparticle diffusion model. The obtained results indicate that the adsorption process, obey pseudo second order kinetics and is diffusion control. The negative value of ΔS and positive values of ΔG and ΔH showed that the adsorption process is orderliness, non-spontaneous and endothermic respectively in nature. The hydrogels were successfully regenerated from the mixture and used again in several steps without a reduction in their efficiency.