Superabsorbent Hydrogel Research Articles

Modified corn stalk carboxymethyl cellulose, acrylic acid and SBA‐15 based composite hydrogel used for agricultural water retention

AbstractSBA‐15 is successfully incorporated into a composite superabsorbent hydrogel polymer (SAHP) by in situ graft polymerization of acrylic acid (AA) on a carboxymethyl cellulose (CMC) backbone using SBA‐15 as a filler. The structure and properties of the SAHPs are studied in detail by means of a variety of characterization methods, including Fourier transform infrared spectroscopy, X‐ray diffraction, and field emission scanning electron microscopy. And the effects of the originating mate‐rials (such as SBA‐15, initiator, cross‐linker, ratio of CMC to AA, and neutralization of AA) and pH on the water absorption properties are discussed. The obtained results show that the introduction of SBA‐15 have significant effect on the intrinsic structure of the superabsorbent. Importantly, the composite SAHP exhibit higher thermal stability and significant swelling as well as water retention capacity. The prepared SAHP show good sensitivity to various surfactant solutions, which not only have water retention applications in agriculture but also show potential applications in the field of biomaterials.

Studies on Agrochemical Controlled Release Behavior of Copolymer Hydrogel with PVA Blends of Natural Polymers and Their Water-Retention Capabilities in Agricultural Soil.

Agricultural technical development relies exclusively on the effective delivery of agrochemicals and water to plants and on reducing the harmful effects of agrochemicals on useful organisms in the soil. In this study, super-absorbent hydrogels were prepared in the form of microspheres using gum Arabic (GA), which was copolymerized once with chitosan (CS) and once with poly (vinyl alcohol) (PVA). To impart mechanical strength to the hydrogel microspheres, a covalent cross-linker (N,N'-methylenebisacrylamide (MBA)) was used for the PVA/GA hydrogel, and an ionic cross-linker (sodium hexametaphosphate (SHMP)) was used for the CS/GA hydrogel. The prepared PVA/GA-CH and CS/GA-PH hydrogel microspheres showed different degrees of swelling (DSs) in the following solution media: deionized water (DW), river water (RW), and buffered solutions (pH 4; pH 9). The PVA/GA-CH hydrogel microspheres showed a maximum DS of 84 g/g in the RW, while the CS/GA-PH hydrogel microspheres showed a maximum DS of 63 g/g in the buffered solution at a pH 9. The water-retention capabilities of the hydrogels were studied using a mixture of 0.5% (w/w) hydrogel microspheres in agricultural soil; the composite showed an additional 20 days of water retention in comparison with a control sample consisting of soil alone. The hydrogels were loaded with urea, which is an important fertilizer in the field of agriculture. The PVA/GA-CH hydrogel microspheres showed a maximum loading percentage (Lmax%) of 89% (w/w), while the CS/GA-PH hydrogel microspheres showed an Lmax% = 79.75% (w/w) for urea. The urea-release behaviors of the hydrogel microspheres were studied under different release media and temperature conditions. In practice, the PVA/GA-CH hydrogel microspheres showed a better release profile in the RW at 10 °C, while the CS/GA-PH hydrogel microspheres showed a more controlled release in media at a pH 9 and at 30 °C. The urea-loaded microspheres, aside from those following the release, were characterized via FTIR and SEM. In contrast, virgin microspheres were characterized using XRD,1H NMR, (TGA and DSC), and the maximum degree of swelling, in addition to being subjected to SEM and FTIR analyses.

Preparation of fast-swelling porous superabsorbent hydrogels with high saline water absorbency under pressure by foaming and post surface crosslinking

Superabsorbent hydrogels have wide applications in many fields because of their unique water absorbing performance. In spite of decades of research about superabsorbent hydrogels, high water absorbency under pressure and fast-swelling are still challenging and highly desired for their applications in hygienic products and others. Here, we report preparation of fast-swelling porous starch-g-poly(acrylic acid)/poly(vinyl alcohol) superabsorbent hydrogels with high saline water absorbency under pressure by foaming and post surface crosslinking. 2,2′-Azobis(2-amidinopropane) dihydrochloride (AIBA) was used as a new porogen instead of conventional porogens like NaHCO3. Post surface crosslinking of the hydrogel was achieved using glycerol via the esterification reaction. AIBA is a better porogen than NaHCO3 regarding porosity and swelling performance of the hydrogels, and its content has great influences on structure and swelling performance of the hydrogels including water absorbency and swelling rate. Also, the surface crosslinking using glycerol can significantly enhance the saline water absorbency under pressure (2 kPa) but at the sacrifice of the swelling rate. Consequently, the hydrogels show high water absorbencies for deionized water (560 g/g), 0.9 wt% NaCl solution (58 g/g), 0.9 wt% NaCl solution under 2 kPa pressure (28 g/g) and fast-swelling (31 s to achieve a highly swelling state).

Salicylic Acid and Superabsorbent Polymers Could Alleviate Water Deficit Stress in Camelina (Camelina Sativa L.)

ABSTRACT Agronomic management and application of growth regulators mitigated the negative effects of water deficit and improved seed oil yield and other traits in camelina. This study assessed the effects of salicylic acid (SA) foliar application and soil application of superabsorbent polymer hydrogel (SPH) on the growth and antioxidant production of camelina (Camelina sativa L.) in 50% and 75% field capacity (FC) groups, as well as in a well-watered treatment. Application of SA and SPH significantly increased camelina yield and its components in 75% FC and well-watered treatments. In the control (no SA or SPH), water deficit reduced seed oil by 13% and 35% in 75% FC and 50% FC, respectively. Application of SA and SPH increased seed oil by 5% and 11%, respectively. Photosynthetic rate (A), stomatal conductance (gs), and chlorophyll content decreased in the 75% FC and 50% FC treatments. Application of SA and SPH increased in A (26% and 19%) and gs (17% and 12%) compared to the control. Superoxide dismutase (SOD), peroxidases (POD), catalases (CAT), and ascorbate peroxidase (APX) activity increased with increased drought stress. The activity of these enzymes increased when SA was applied. Generally, foliar application of SA was more effective than soil application of SPH in camelina to alleviate the injurious effects of drought stress.

Itaconic acid-derived reactive protic ionic liquid (PIL)-containing superabsorbent green hydrogel adsorbent for the removal of anionic textile dyes

Recently, hydrogels containing bio-based building blocks have become very common as adsorbents for toxic dye removal. Herein, we prepared gelatin-containing semi-IPN hydrogels that contain different amounts of itaconic acid-based protic ionic liquids (PILs). We then used these hydrogels for the removal of two different anionic textile dyes (Reactive Red 21 and Reactive Blue 19). The synthesized PIL was characterized by 1H NMR and the hydrogels were characterized by FTIR spectroscopy. The hydrogels displayed up to 670 % swelling in water depending on their compositions. The hydrogels containing none or lower amounts of PIL were found to display maximum adsorption capacities under acidic conditions within 120 min. When the concentration of the PIL within the hydrogels was over a certain value, the adsorption became almost independent of pH. The adsorption behavior was found to well correlate with the Langmuir isotherm and the Gibbs free energy change values for the adsorption were calculated to be negative, meaning that the adsorption of both dyes at room temperature occurs spontaneously. The best-performing hydrogel composition was tested in real wastewater samples without any pH adjustments and over 75 % removal efficiency was obtained.

The effect of processing design and the stabilizing effect of nanostructures on the swelling and adsorption properties of polyvinylpyrrolidone macroporous ferrogels obtained through a cryogenic route

AbstractThis paper reports the synthesis of macroporous polyvinylpyrrolidone (PVP) hydrogels modified with in‐situ generated magnetic nanoparticles (NPs). The hydrogels were formed by an optimized thermally induced crosslinking route, initiated by the presence of ammonium persulfate, whereas the macroporosity was created through a cryogenic technique. Crosslinking stabilizes the three dimensional (3D) gel structure, allowing the replacement of expensive and time‐consuming lyophilization steps in favor of simpler drying procedures at atmospheric pressure. The in‐situ formation of iron oxide NPs (IONPs) was achieved through oxide precursors impregnation followed by precipitation of the IONPs in the highly swellable hydrogels. This reaction was performed by addressing two strategies, namely, before or after cryogenic processing, to evaluate its effect on the final swelling and adsorption properties of the gel matrices. It is demonstrated that the inclusion of the magnetic NPs before cryo‐structuring allows the stabilization of the gel against collapse, favoring the conservation of a highly swellable environment. The synergy between the adsorption capacity of the IONPs and the high swelling of the macroporous structure allows obtaining materials with potential in adsorption processes. Preliminary analyses showed that macroporous samples obtained with 32 wt% IONPs led to methylene blue (MB) adsorption capacities as high as 400 mg dye/g ferrogel, for dye concentrations as low as 10 mg/L. These results show that the use of an adequate strategy for the processing of macroporous ferrogels can be of high importance in the design of new adsorbents and superabsorbent hydrogels.

Poly(Acrylic Acid)-Sodium Alginate Superabsorbent Hydrogels Synthesized by Electron Beam Irradiation Part I: Impact of Initiator Concentration and Irradiation Dose on Structure, Network Parameters and Swelling Properties.

In the present paper, hydrogels based on acrylic acid (20%), sodium alginate (0.5%) and poly(ethylene oxide) (0.1%) were obtained by electron beam irradiation at room temperature with doses between 5 and 20 kGy, using potassium persulfate in concentrations up to 0.3% as a reaction initiator. The influence of initiator concentration and irradiation dose on hydrogel network parameters, swelling and deswelling behavior, gelation and degradation points, structure and morphology were investigated. Cross-link density increased with the irradiation dose and initiator addition, except at 20 kGy. The gel fraction was over 87.0% in all cases. Swelling experiments in distilled water showed swelling degrees of 40,000% at an irradiation dose of 5 kGy when a concentration of 0.1% initiator was added. A relationship between the swelling degree and irradiation dose, cross-linking degree (that increases from 0.044 × 102 to 0.995 × 102 mol/cm3) and mesh size (that decreases from about 220 nm to 26 nm) was observed. The addition of only 0.1% of PP led to the obtaining of hydrogels with a swelling degree of 42,954% (about 430 g/g) at an irradiation dose of 5 kGy and of 7206% (about 62 g/g) at 20 kGy, which are higher percentages than those obtained in the same irradiation conditions but without PP.

90-LB: Real-World Effectiveness of an Oral Superabsorbent Hydrogel for Weight Management

Background and Objective: Plenity is a non-systemic oral superabsorbent hydrogel which promotes fullness by increasing the volume and elasticity of ingested food in the stomach and small intestine. The efficacy and safety of the oral hydrogel have been demonstrated in clinical trials. This study evaluated weight change in people with overweight or obesity following treatment with the oral hydrogel in a real-world setting. Research Design and Methods: Data was analyzed using chart records from a national telehealth platform. Demographic and health information and anthropometric measures were self-reported by patients during online visits. Patients were included in the analysis if they had received a prescription for the oral hydrogel, had a follow-up visit at 180 ± 30 days, reported having access to treatment for ≥ 75% of days, and reported taking it at least 1 day per week. Descriptive statistical analysis and tests of differences (χ2, t-tests) were performed in R Version 4.2.2. Results: Patients (n=894) were 74% female, aged 50 ± 11 years, with a mean pre-treatment body weight of 90 ± 16 kg and BMI of 32.0 ± 4.1 kg/m2. One-third (35%) of patients had overweight (BMI 25-30 kg/m2) at baseline and mean treatment duration was 160 ± 16 days. Weight loss of any amount (>0 kg) was reported by 85.9% of patients, with a mean weight change of -6.1 ± 3.9% (-5.6 ± 3.8 kg) in this group. About half (48%) of all patients achieved clinically significant weight loss of ≥ 5%. Among these treatment responders, mean weight loss was 8.7 ± 3.3% (8.0 ± 3.4 kg). Clinically significant weight loss response ≥ 5% was more likely among people that reported poor baseline diet quality (P = 0.02). Conclusions: Treatment with an oral superabsorbent hydrogel in people with overweight and mild obesity in a real-world environment was associated with clinically significant weight loss response at 6 months. People with self-assessed poor baseline diet quality, in particular, were more likely to have a meaningful response to therapy. Disclosure D. Bialonczyk: Employee; Gelesis. M. S. Zhou: Employee; Ro. L. Broffman: Employee; Roman Health Adventures. T. Y. Doron: Employee; Roman Health Adventures. J. Bowles: Employee; MCPHS University, Gelesis. E. Chiquette: Consultant; Gelesis.

Gamma Radiation-Induced Advanced 2,3-Dimethylacrylic Acid-(2-Acrylamido-2-methyl-1-propanesulfonic Acid) Superabsorbent Hydrogel: Synthesis and Characterization

Gamma radiation technique for the preparation of pure hydrogels is gaining popularity worldwide. Superabsorbent hydrogels play vital roles in different fields of application. The present work mainly focuses on the preparation and characterization of 2,3-Dimethylacrylic acid-(2-Acrylamido-2-methyl-1-propane sulfonic acid) (DMAA-AMPSA) superabsorbent hydrogel by applying gamma radiation and optimization of the proper dose. To prepare DMAA-AMPSA hydrogel, different doses ranging from 2 kGy to 30 kGy were imparted on the blend aqueous solution of the monomers. The equilibrium swelling increases with increasing radiation dose, followed by decreasing after reaching a certain level, and the highest result is found to be 26,324.9% at 10 kGy. Fourier Transform Infrared (FTIR) and Nuclear Magnetic Resonance (NMR) spectroscopy confirmed the formation of co-polymer by showing the characteristic functional groups and proton environment of the gel. X-ray Diffraction (XRD) pattern indicates the crystalline/amorphous nature of the gel. The Differential Scanning Calorimetry (DSC) and Thermogravimetry Analysis (TGA) revealed the thermal stability of the gel. The surface morphology and constitutional elements were analyzed and confirmed by Scanning Electron Microscopy (SEM) equipped with Energy Dispersive Spectroscopy (EDS). Finally, it can be stated that hydrogels can be usable in metal adsorption, drug delivery, and other relevant fields.

Applying Copolymerization Kinetics to Understand and Optimize Swelling Responses in Superabsorbent Hydrogels

While acrylic acid (AA)-based superabsorbent hydrogels (SAHs) have been widely used in multiple applications, the effects of counterion condensation and the polyelectrolyte effect at suppressing the effective degree of ionization in such systems limit their superabsorbency. Herein we describe the use, and investigate the mechanism, of sulfate comonomers containing different types of polymerizable functional groups for increasing the superabsorbency of acrylic acid-based SAHs. Specifically, acrylamido-2-methylpropanesulfonic acid (AMPS), 3-sulfopropyl acrylate (SPAK), and 3-sulfopropyl methacrylate (SPMK) sulfated monomers featuring similar distances between the polymer backbone and the sulfate group but different polymerizable groups were copolymerized with acrylic acid to fabricate SAHs. Measurements of the effective homopolymerization rate constants and copolymerization ratios associated with each copolymerization enabled the prediction of the relative chain distributions of monomers in each copolymer, as quantified by the blockiness parameter (i.e., the instantaneous or average number of consecutive monomers of each type polymerized). While all sulfated comonomers significantly enhanced swelling relative to an acrylic acid control, copolymers in which longer AA blocks are produced (AA-AMPS) resulted in lower swelling than copolymers in which shorter AA blocks are produced (AA-SPAK, AA-SPMK), a result attributed to the suppressed polyelectrolyte effect in copolymers with shorter AA blocks. The formation of limited length blocks of the sulfated monomer SPMK showed additional benefits for enhancing swelling, consistent with enhanced direct charge–charge repulsion between fixed charges in such copolymer systems. We anticipate this linkage between copolymerization kinetics and swelling properties offers the potential to enable improved rational design of superabsorbent hydrogels with higher sorbency.

Sodium Salt of Partially Carboxymethylated Sodium Alginate-g-Poly(acrylonitrile): I. Photo-Induced Synthesis, Characterization, and Alkaline Hydrolysis.

An efficient redox initiating system, ceric ammonium nitrate/nitric acid, has been employed for the first time to carry out photo-induced graft copolymerization of acrylonitrile (AN) onto sodium salt of partially carboxymethylated sodium alginate, having an average degree of substitution value to be 1.10. The photo-grafting reaction conditions for maximum grafting have been systematically optimized by varying the reaction variables such as reaction time, temperature, the concentration of acrylonitrile monomer, ceric ammonium nitrate, and nitric acid, as well as the amount of the backbone. The optimum reaction conditions are obtained with a reaction time of 4 h, reaction temperature of 30 °C, acrylonitrile monomer concentration of 0.152 mol/L, initiator concentration of 5 × 10-3 mol/L, nitric acid concentration of 0.20 mol/L, amount of backbone of 0.20 (dry basis) and the total volume of the reaction system of 150 mL. The highest percentage of grafting (%G) and grafting efficiency (%GE) achieved are 316.53% and 99.31%, respectively. The optimally prepared graft copolymer, sodium salt of partially carboxymethylated sodium alginate-g-polyacrylonitrile (%G = 316.53), has been hydrolyzed in an alkaline medium (0.7N NaOH, 90-95 °C for ~2.5 h) to obtain the superabsorbent hydrogel, H-Na-PCMSA-g-PAN. The chemical structure, thermal characteristics, and morphology of the products have also been studied.

Sodium Salt of Partially Carboxymethylated Sodium Alginate-Graft-Poly(Acrylonitrile): II Superabsorbency, Salt Sensitivity and Swelling Kinetics of Hydrogel, H-Na-PCMSA-g-PAN.

The water absorption measurements of a novel superabsorbent anionic hydrogel, H-Na-PCMSA-g-PAN, has been reported first time in water with a poor conductivity, 0.15 M saline (NaCl, CaCl2, and AlCl3) solutions, and simulated urine (SU) solutions at various times. The hydrogel has been prepared by the saponification of the graft copolymer, Na-PCMSA-g-PAN (%G = 316.53, %GE = 99.31). Results indicated that as compared to the swelling capacity values evaluated in water with a poor conductivity, the ability of the hydrogel to swell in various saline solutions with the same concentration is significantly reduced at all different durations. The swelling tends to be Na+ > Ca2+ > Al3+ at the same saline concentration in the solution. Studies of the absorbency in various aqueous saline (NaCl) solutions also revealed that the swelling capacity decreased as the ionic strength of the swelling medium rose, which is consistent with the experimental results and Flory's equation. Furthermore, the experimental results strongly suggested that second-order kinetics governs the swelling process of the hydrogel in various swelling media. The swelling characteristics and equilibrium water contents for the hydrogel in various swelling media have also been researched. The hydrogel samples have been successfully characterized by FTIR to show the change in chemical environment to COO- and CONH2 groups after swelling in different swelling media. The samples have also been characterized by SEM technique.

Rapid Preparation of Superabsorbent Self-Healing Hydrogels by Frontal Polymerization.

Hydrogels have received increasing interest owing to their excellent physicochemical properties and wide applications. In this paper, we report the rapid fabrication of new hydrogels possessing a super water swelling capacity and self-healing ability using a fast, energy-efficient, and convenient method of frontal polymerization (FP). Self-sustained copolymerization of acrylamide (AM), 3-[Dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]azaniumyl]propane-1-sulfonate (SBMA), and acrylic acid (AA) within 10 min via FP yielded highly transparent and stretchable poly(AM-co-SBMA-co-AA) hydrogels. Thermogravimetric analysis and Fourier transform infrared spectroscopy confirmed the successful fabrication of poly(AM-co-SBMA-co-AA) hydrogels with a single copolymer composition without branched polymers. The effect of monomer ratio on FP features as well as porous morphology, swelling behavior, and self-healing performance of the hydrogels were systematically investigated, showing that the properties of the hydrogels could be tuned by adjusting the chemical composition. The resulting hydrogels were superabsorbent and sensitive to pH, exhibiting a high swelling ratio of up to 11,802% in water and 13,588% in an alkaline environment. The rheological data revealed a stable gel network. These hydrogels also had a favorable self-healing ability with a healing efficiency of up to 95%. This work contributes a simple and efficient method for the rapid preparation of superabsorbent and self-healing hydrogels.

Crosslinked poly(hydroxybutyl acrylate-co-acrylamide) based hydrogels: synthesis, characterization, and performance evaluation in heavy metal removal

By radical polymerization, two series of superabsorbent hydrogels of hydroxybutyl acrylate and acrylamide copolymers, poly(HBA-co-AAm), were obtained. In the first series, the ratio of hydroxybutyl acrylate to acrylamide was optimized with a constant amount of methylene bisacrylamide (MBA) as a cross-linking agent. In the second series, the amount of MBA was changed at a fixed monomer ratio. The structure of the copolymers was confirmed by the FTIR method. Swelling parameters and mechanical properties were tested. Hydrogels with a high Young’s modulus and a high degree of swelling were selected for the study of adsorption properties towards Co2+, Ni2+ and Cd2+ ions. The influence of basic factors such as adsorbent dose, exposure time and pH on adsorption efficiency was also investigated. The ability to adsorb heavy metal ions changed as follows: Co2+> Ni2+> Cd2+.

Starch‐Based Superabsorbent Hydrogel with High Electrolyte Retention Capability and Synergistic Interface Engineering for Long‐Lifespan Flexible Zinc−Air Batteries

AbstractThe advent of wearable electronics has strongly stimulated advanced research into the exploration of flexible zinc−air batteries (ZABs) with high theoretical energy density, high inherent safety, and low cost. However, the half‐open battery structure and the high concentration of alkaline aqueous environment pose great challenges on the electrolyte retention capability and the zinc anode stability. Herein, a starch‐based superabsorbent hydrogel polymer electrolyte (SSHPE) with high ionic conductivity, electrolyte absorption and retention capabilities, strong alkaline resistance and high zinc anode stability has been designed and applied in ZABs. Experimental and calculational analyses probe into the root of the superiority of SSHPEs, confirming the significance of the carboxyl functional groups along their polymer chains. These features endow the as‐fabricated ZAB a long cycle life of 300 h, much longer than that with commonly used poly(vinyl alcohol)‐based electrolyte.

Starch-Based Superabsorbent Hydrogel with High Electrolyte Retention Capability and Synergistic Interface Engineering for Long-Lifespan Flexible Zinc-Air Batteries.

The advent of wearable electronics has strongly stimulated advanced research into the exploration of flexible zinc-air batteries (ZABs) with high theoretical energy density, high inherent safety, and low cost. However, the half-open battery structure and the high concentration of alkaline aqueous environment pose great challenges on the electrolyte retention capability and the zinc anode stability. Herein, a starch-based superabsorbent hydrogel polymer electrolyte (SSHPE) with high ionic conductivity, electrolyte absorption and retention capabilities, strong alkaline resistance and high zinc anode stability has been designed and applied in ZABs. Experimental and calculational analyses probe into the root of the superiority of SSHPEs, confirming the significance of the carboxyl functional groups along their polymer chains. These features endow the as-fabricated ZAB a long cycle life of 300 h, much longer than that with commonly used poly(vinyl alcohol)-based electrolyte.

Temperature- and pH-Responsive Super-Absorbent Hydrogel Based on Grafted Cellulose and Capable of Heavy Metal Removal from Aqueous Solutions

In this work, we prepared highly swelling, stimuli-responsive hydrogels capable of the highly efficient adsorption of inorganic pollutants. The hydrogels were based on hydroxypropyl methyl cellulose (HPMC) grafted with acrylamide (AM) and 3-sulfopropyl acrylate (SPA) and were synthesized via the growth (radical polymerization) of the grafted copolymer chains on HPMC, which was activated by radical oxidation. These grafted structures were crosslinked to an infinite network by a small amount of di-vinyl comonomer. HPMC was chosen as a cheap hydrophilic and naturally sourced polymer backbone, while AM and SPA were employed to preferentially bond coordinating and cationic inorganic pollutants, respectively. All the gels displayed a pronounced elastic character, as well as considerably high values of stress at break (several hundred %). The gel with the highest fraction of the ionic comonomer SPA (with an AM/SPA ratio = 0.5) displayed the highest equilibrium swelling ratio (12,100%), the highest volume response to temperature and pH, and the fastest swelling kinetics, but also the lowest modulus. The other gels (with AM/SPA = 1 and 2) displayed several times higher moduli but more modest pH responses and only very modest temperature sensitivity. Cr(VI) adsorption tests indicated that the prepared hydrogels removed this species from water very efficiently: between 90 and 96% in one step. The hydrogels with AM/SPA ratios of 0.5 and 1 appeared to be promising regenerable (via pH) materials for repeated Cr(VI) adsorption.

FORMULATION AND EVALUATION OF SUPERABSORBENT HYDROGEL FROM NATURAL POLYMER

Objective: The objective of the present study was to synthesize the hydrogel from natural polymer and evaluation of its physical and chemical properties. Methods: Hydrogel was synthesized using graft co-polymerization technique from wheat starch, by crosslinking with acrylic acid. The product was purified, dried and micronized. It was then evaluated for water absorption and retention property at varying pH, FTIR, PXRD and Thermal analysis, microscopic, micromeritic and stability studies etc. Furthermore, the effect of NaOH treatment on prepared hydrogel material was studied. Results: Result of the studies revealed that superabsorbent hydrogel (SAH) product shows good water absorption capacity of 120g/g at neutral pH. Maximum water absorption capacity was at pH 9 which is 146.28g/g. Product shows good thermal stability, less cohesiveness and is amorphous in nature. In hygroscopicity study weight gain by SAH was 6.65% only while for unpurified SAH and NaOH treated SAH, it was 10.5% and 23.42% respectively. NaOH treatment shows a decrease in water absorption capacity by more than 40% also there is change in surface morphology of the product. Additionally, hygroscopicity was more and degradation rate was faster for NaOH treated hydrogel. Conclusion: Crosslinking with acrylic acid can form superabsorbent hydrogel material from the natural polymer such as wheat starch. The product shows excellent water absorption and retention capacity. pH affects water absorption capacity and shows maximum at pH 9 and at lower and higher pH it decreases to a significant level. There was decline in water absorption capacity and increase in hygroscopicity, when NaOH treatment is given to the SAH powder.

Nanoporous hydrogel absorbent based on salep: Swelling behavior and methyl orange adsorption capacity

This study used the gas-blowing method to develop a nanoporous hydrogel using poly (3-sulfopropyl acrylate-co-acrylic acid-co-acrylamide) grafted onto salep. The synthesis of the nanoporous hydrogel was optimized by various parameters for maximum swelling capacity. The nanoporous hydrogel was characterized using FT-IR, TGA, XRD, TEM, and SEM analyses. Images from SEM showed numerous pores and channels in the hydrogel with an average size of about 80 nm, forming a honeycomb-like shape. The change in surface charge was investigated by zeta potential and revealed that the surface charge of the hydrogel ranged from 20 mV at acidic conditions to −25 mV at basic conditions. The swelling behavior of optimum superabsorbent hydrogel was determined under different environmental conditions, such as different pH values, ionic strengths of the environment, and solvents. In addition, the swelling kinetics and the absorbance under loading of the hydrogel sample in different environments were investigated. Moreover, Methyl Orange (MO) dye was removed from aqueous solutions using the nanoporous hydrogel as an adsorbent. The adsorption behavior of the hydrogel was examined under various conditions, and the adsorption capacity of the hydrogel was found tobe 400 mg g−1. The maximum water uptake was obtained under the following conditions: Salep weight = 0.01 g, AA = 60 μL, MBA = 300 μL, APS = 60 μL, TEMED = 90 μL, AAm = 600 μL, and SPAK = 90 μL. Lastly, the adsorption kinetics was studied by employing pseudo-first-order, pseudo-second-order, and intra-particle diffusion models.

Addition of sodium alginate capsules containing Lysinibacillus sphaericus for self-healing of cracks in mortars

The biomineralization technique of crack remediation in construction mortar can be achieved through the incorporation of calcifying bacteria within the mortar matrix. However, the thermal and autogenous shrinkage associated with the hydration of cement can be detrimental to the survival of the bacterial spores. Encapsulation of the spores in a matrix such as superabsorbent hydrogels, specifically sodium alginate, can provide protection from such detrimental conditions while also serving as a water reservoir for the metabolic activity of the bacterial cells. This paper investigated the addition of sodium alginate capsules prepared through spherification in construction mortars, aiming to preserve and optimize rheological, physical and mechanical properties, and to release bacteria when cracks occur. Mortar formulations with capsules containing Lysinibacillus sphaericus were calculated in order to maintain the granulometric distribution of standard formulation, thus obtaining products with excellent rheological, physical and mechanical properties, and allowing the addition of up to 1% capsules. Multivariate analysis of variance was applied at each age, showing that formulations with capsules kept the same properties as the original formula. After cracking, it was possible to observe the action of the released bacteria, through the formation of crystalline structures at the cracks. The capsules were prepared through a simple and cheap process, and it was proved that not only they do not affect concrete properties, but also are effective in both protecting the bacteria during mixing and hardening and releasing it after cracking.