Poly Acrylic Acid Hydrogel Research Articles

The e-Flower: A hydrogel-actuated 3D MEA for brain spheroid electrophysiology.

Traditional microelectrode arrays (MEAs) are limited to measuring electrophysiological activity in two dimensions, failing to capture the complexity of three-dimensional (3D) tissues such as neural organoids and spheroids. Here, we introduce a flower-shaped MEA (e-Flower) that can envelop submillimeter brain spheroids following actuation by the sole addition of the cell culture medium. Inspired by soft microgrippers, its actuation mechanism leverages the swelling properties of a polyacrylic acid hydrogel grafted to a polyimide substrate hosting the electrical interconnects. Compatible with standard electrophysiology recording systems, the e-Flower does not require additional equipment or solvents and is ready to use with preformed 3D tissues. We designed an e-Flower achieving a curvature as low as 300 micrometers within minutes, a value tunable by the choice of reswelling media and hydrogel cross-linker concentration. Furthermore, we demonstrate the ability of the e-Flower to detect spontaneous neural activity across the spheroid surface, demonstrating its potential for comprehensive neural signal recording.

Lignin sulfonate induced ultrafast fabrication of polypyrrole-based conductive organohydrogel for high performance flexible strain and temperature sensor

The ultrafast preparation of electrically conductive hydrogels to endow high sensing performance and temperature tolerance remains a critical challenge. Herein, lignosulfonate sodium-templated polypyrrole (LS-PPy) nanofillers were rapidly introduced into polyacrylic acid (PAA) hydrogel through ultrafast free radical polymerization in a glycerol/water binary solvent system. The resultant LS-PPy/PAA electrically conductive organohydrogel possesses satisfactory mechanical performance (strength of 56 kPa at a tensile strain of 800 %), strong adhesion, and a desirable low freezing point (−35 °C). Furthermore, this organohydrogel exhibits high strain sensitivity (gauge factor = 2.65), fast response time (~160 ms), low signal hysteresis, and excellent cyclic stability (over 1200 cycles). And the wearable LS-PPy/PAA organohydrogel sensor could accurately and real-time monitor various intense or subtle human movements, such as joint bending, facial expression and hand writing. Besides, the developed LS-PPy/PAA temperature sensor can respond to environmental temperature variations over a wide range of −20–100 °C. High resolution of 0.5 °C with remarkable sensitivity (−0.80 %/°C and linearity of R2 = 0.99) and repeatability were achieved within 36.5–40 °C, which makes it suitable for human body temperature monitoring. All these results demonstrate the substantial prospective value of the LS-PPy/PAA hydrogel in wearable sensors and other associated fields.

Eco-Friendly Carbon Nanotubes Reinforced with Sodium Alginate/Polyacrylic Acid for Enhanced Adsorption of Copper Ions: Kinetics, Isotherm, and Mechanism Adsorption Studies.

This study investigates the removal efficiency of Cu2+ from wastewater using a composite hydrogel made of carbon nanotubes (CNTs), sodium alginate (SA), and polyacrylic acid (PAA) prepared by free radical polymerization. The CNTs@SA/PAA hydrogel's structure and properties were characterized using SEM, TEM, FTIR, XRD, rheology, DSC, EDS, elemental mapping analysis, and swelling. The adsorption performance for Cu2+ was tested in batch adsorption experiments, considering the pH, dosage, initial concentration, and contact time. The optimal conditions for Cu2+ removal were pH 5.0, an adsorbent dosage of 500 mg/L, and a contact time of 360 min. The adsorption followed pseudo-second order kinetics. Isotherm analyses (Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Sips, Toth, and Khan) revealed that the Freundlich isotherm best described the adsorption, with a maximum capacity of 358.52 mg/g. A thermodynamic analysis indicated that physical adsorption was the main interaction, with the spontaneity of the process also demonstrated. This study highlights the high efficiency and environmental friendliness of CNT@SA/PAA composites for Cu2+ removal from wastewater, offering a promising approach for water treatment.

Aminated lignin and phytic acid-assisted polyacrylic acid hydrogel sensors with enhanced mechanical properties and strong adhesion

Excellent comprehensive performance of hydrogels can be achieved by synergistically combining multiple interaction mechanisms. In this study, a series of hydrogels with rapid gelation and excellent adhesive, mechanical, self-healing, and conductive properties, driven by covalent bonds and multiple reversible interactions, were constructed by mixing acrylic acid (AA), aminated alkaline lignin (AAL), phytic acid (PA), and Fe3+. The rigid skeletons of polyacrylic acid (PAA) and AAL, as well as the metal coordination bonds formed between them and Fe3+, enhance the mechanical properties of the samples. The samples exhibit excellent tensile strength and compressive strength, reaching 73.7 kPa and 4.6 MPa (under a compressive strain of 80 %), respectively, with a tensile strain of 1142 % under the same condition. Adding PA enhances the compliance and adhesion (148.2 kPa for porcine skin) of the gel and endowed it with good flame retardancy. Additionally, the sample maintained its good mechanical properties and conductivity even after five cutting-healing cycles. Good durability, robust adhesion, and high electrical conductivity of the sample render it a promising strain sensor for electronic devices. This work provides a design strategy for preparing hydrogels with superior adhesion and good comprehensive performance.

Tough and temperature-tolerance cellulose/polyacrylic acid/bentonite hydrogel with high ionic conductivity enables self-powered triboelectric wearable electronic devices

Solid-state zinc-ion hybrid supercapacitors (ZHSCs) featuring hydrogel electrolytes have become ideal for large-scale flexible energy storage. However, existing polyacrylic acid (PAA) hydrogel electrolytes often lack the combined traits of ionic conductivity, mechanical robustness, and temperature tolerance. Herein, a versatile PAA-based hydrogel electrolyte (ACBH-Zn) containing a ZnCl2-cellulose solution and bentonite (BT) is delivered, facilitated by cooperative coordination bonds and hydrogen bonds. The coordination bonds between Zn2+ and −COOH of PAA, in conjunction with cellulose and BT, alongside the abundant hydrogen bonds within cellulose and PAA, are conducive to upgrading mechanical strength and ionic conductivity, while the BT's lamellar structure further provides sufficient ion migration channels. Consequently, the ACBH-Zn showcases exceptional mechanical properties, satisfying ionic conductivity (88.9 mS cm−1), and excellent temperature tolerance at −60 °C (30.3 mS cm−1). The ACBH-ZHSC, when assembled, attains a remarkable maximum energy density (323.4 Wh kg−1), maintaining an impressive capacity retention rate (92 %) even after undergoing 10,000 cycles at 10.0 A g−1. Furthermore, the assembled self-powered triboelectric wearable electronic device effectively converts mechanical energy from human movement into electrical energy, enabling efficient storage and utilization, and offering promising insights into the application of flexible wearable devices.

Gellan Gum grafted poly acrylic acid hydrogels: Synthesis and adsorption studies

Gellan Gum (GG) grafted poly-acrylic acid (GG-g-pAAc) hydrogels of different composition were synthesized by changing the concentration of GG through free radical polymerization. The hydrogels were characterized through SEM, TGA, and FTIR. The FTIR spectra confirmed the grafting of GG into the network of polyacrylic acid and evidenced the GG-g-pAAc formation. The rough surface nature of the hydrogels was elaborated through SEM analysis provided the information about the materials to be utilized for removal purpose. The thermal stability was confirmed by TGA analysis and the hydrogels were found stable upto a high temperature range. With an efficiency of 96%, Basic Orange-2 dye (BO-2) was successfully removed from wastewater using synthesized hydrogels as an adsorbent. The adsorption parameters were calculated using a number of different kinetic models. According to the findings, the pseudo-second order kinetics model best suited to the kinetics data, while the Langmuir isotherm provided the most comprehensive explanation of the process of adsorption. BO-2 was removed to the greatest extent (257.5 mg/g). Additionally, the results showed that the adsorption process on synthesized hydrogels was exothermic with values of ΔH = −13.2, −219.4 and −12.9 kJ/mol for pAAc, 10%GG-g-pAAc, and 20%GG-g-pAAc respectively. The adsorption process is spontaneous, with negative values of ΔG = −8.2, −214.4 and −7.947 kJ/mol for pAAc, 10%GG-g-pAAc and 20%GG-g-pAAc at 293K, respectively. The adsorption process on synthesized hydrogels showed no dis-orderness with negative values of ΔS = −17.2, −461.16 and −16.42 kJ/mol for pAAc, 10%GG-g-pAAc and 20%GG-g-pAAc, respectively.

Structure, Property Optimization, and Adsorption Properties of N,N'-methylenebisacrylamide Cross-Linked Polyacrylic Acid Hydrogels under Different Curing Conditions.

In this study, polyacrylic acid hydrogels were prepared by modulating the cross-linking agent mass ratio using UV and heat curing methods. The structures and properties of the hydrogels were characterized and analyzed using Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analysis. The results showed that the mechanical properties of the hydrogels prepared through UV curing were better than those prepared through heat curing. The maximum mechanical tensile strength of 139 kPa was achieved at a cross-linking agent mass ratio of 3.85% with 20 min of UV curing, and the maximum mechanical compressive strength of 0.16 MPa was achieved at a cross-linking agent mass ratio of 2.91% with 20 min of UV curing. However, the hydrogels prepared by heat curing had a higher tensile strength than those prepared using the heat curing method. In addition, the thermally cured hydrogels had higher water absorption and adsorption properties. Moreover, the PAA hydrogels prepared at cross-linking agent mass ratios of 1.91 and 2.91% with 2 h of the heat curing method had the best swelling properties. Moreover, the increase in the cross-linker mass concentration led to a decrease in the pore size and porosity and to a more compact structure.

A Universal Strategy for Constructing Hydrogel Assemblies Enabled by PAA Hydrogel Adhesive.

Hydrogel is a significant type of building block for constructing macroscopic assemblies, the construction of which usually entails the incorporation of supramolecular groups. However, supramolecular group recognition is specific and only suitable for assembling two particular modified hydrogels, but not a versatile strategy. Herein, a universal strategy without modification process is proposed using polyacrylic acid (PAA) hydrogel as the adhesive layer to assemble different kinds of hydrogels. Furthermore, hydrogel assemblies with various shapes and multi-stimuli responsiveness are constructed by assembling different stimuli-responsive hydrogels with PAA hydrogel. Therefore, hydrogel assemblies are able to complete bending motions upon applying corresponding stimuli. This strategy provides a universal approach for constructing hydrogel assemblies, and also shows the potential for developing soft robots with versatile functions.

Aptameric photonic structure-based optical biosensor for the detection of microcystin

An optical photonic biosensor for the detection of microcystin (MC) has been developed using an aptamer-immobilized interpenetrating polymeric network (IPNaptamer) intertwined with solid-state cholesteric liquid crystals (CLCsolids). The IPN was constructed with a polyacrylic acid hydrogel (PAA). Aptamer immobilization enhances polarity while blocking hydrogen bonding between the carboxylic groups of PAA-IPN hydrogel, thereby increasing the swelling ratio of the PAA-IPN hydrogel. This leads to an expansion in the helical pitch of the corresponding IPNaptamer-CLCsolid biosensor chip and results in a red-shift in the reflected color. Upon exposure to an aqueous MC solution, the IPNaptamer-CLCsolid biosensor chip exhibits aptamer-mediated engulfment of MC, resulting in reduced polarity of the IPNaptamer complex and a consequential blue-shift in the biosensor chip color occurred. The wavelength shift of the IPNaptamer-CLCsolid biosensor chip demonstrates a linear change with an increase in MC concentration from 3.8 to 150 nM, with a limit of detection of 0.88 nM. This novel optical biosensor is characterized by its low cost, simplicity, selectivity, and sensitivity, offering a promising strategy for designing similar toxin biosensors through the modification of biological receptors.

Diffusiophoretic Fast Swelling of Chemically Responsive Hydrogels.

Acid-induced release of stored ions from polyacrylic acid hydrogels (with a free surface fully permeable to the ion and acid) was observed to increase the gel osmotic pressure that leads to rapid swelling faster than the characteristic solvent absorption rate of the gel. The subsequent equilibration of the diffusing ion concentration across the gel surface diminishes the osmotic pressure. Then, the swollen gel contracts, thereby completing one actuation cycle. We develop a continuum poroelastic theory that explains the experiments by introducing a "gel diffusiophoresis" mechanism: Steric repulsion between the gel polymers and released ions can induce a diffusio-osmotic solvent intake counteracted by the diffusiophoretic expansion of the gel network that ceases when the ion gradient vanishes. For applications ranging from drug delivery to soft robotics, engineering the gel diffusiophoresis may enable stimuli-responsive hydrogels with amplified strain rates and power output.

Coordination interaction based two-dimensional photonic crystal polyacrylic acid hydrogel material for sensitive and visual detection of uranyl ion in water

Coordination interaction based two-dimensional photonic crystal polyacrylic acid hydrogel material for sensitive and visual detection of uranyl ion in water

Synthesis of carboxymethyl starch co (polyacrylamide/ polyacrylic acid) hydrogel for removing methylene blue dye from aqueous solution

Natural polysaccharides, notably starch, have garnered attention for their accessibility, cost-effectiveness, and biodegradability. Modifying starch to carboxymethyl starch enhances its solubility, swelling capacity, and adsorption efficiency. This research examines the synthesis of an effective hydrogel adsorbent based on carboxymethyl starch for the elimination of methylene blue from aqueous solutions. The hydrogel was synthesized using polyacrylamide and polyacrylic acid as monomers, ammonium persulfate as the initiator, and N,N′-methylenebisacrylamide as the cross-linker. Through FESEM, swelling morphology was evaluated in both distilled water and methylene blue dye. The adsorption data elucidated that the adsorption capacity of the hydrogel significantly depends on the dosage of the adsorbent, pH, and concentration of the MB dye. At a pH of 7 and a dye concentration of 250 mg/L, the hydrogel exhibited an impressive 95 % removal rate for methylene blue. The results indicate that the adsorption process follows pseudo-second-order kinetics and conforms well to the Langmuir adsorption isotherm, indicating a maximum adsorption capacity of 1700 mg/g. According to the pseudo-second-order kinetic model and FTIR analysis, methylene blue chemisorbs to the adsorbent material. Hydrogel absorbents regulate adsorption through both intra-particle diffusion and liquid film diffusion. These results highlight the potential of the new hydrogel absorber for water purification.

Synthesis, characterization and adsorption studies of hydroxy ethyl cellulose grafted polyacrylic acid hydrogels; using basic yellow-28 as model dye

Novel hydrogels of hydroxy ethyl cellulose and polyacrylic acid (HEC-G-pAAc) were created by varying the ratio of hydroxy ethyl cellulose to acrylic acid and were characterized using analytical techniques. The synthesized hydrogels were characterized through SEM, TGA, FTIR, pH studies and Fick’s law. The SEM images revealed that the fabricated hydrogels have different adsorption sites for the dyes. According to the TGA results the decomposition of the hydrogels occurs in three successive stages (22–200 °C, 200–310 °C, 310–500 °C). The optimum pH for the adsorption of basic yellow-28 is on the HEC-G-pAAc is pH-8 as it was observed in the pH studies. The optimum temperature for the adsorption of basic yellow-28 is on the HEC-G-pAAc was found to be 293 K.The Basic Yellow-28 dye was successfully removed from wastewater with a 98% effectiveness using synthetic hydrogels as an adsorbent. The adsorption parameters were calculated using a number of different kinetic models like pseudo-second order, Elovich, intraparticle-diffusion and Bangham kinetic models. The pseudo-2nd order kinetics model was found to best fit the kinetics data, while the Langmuir isotherm offered the most thorough explanation of the adsorption process. Basic Yellow-28 dye was removed to the greatest extent by the synthesized hydrogels (pAAc = 156 mg/g, 10%HEC-G-pAAc =166.3 mg/g, 20%HEC-G-pAAc =176.2 mg/g) after 90 min of contact at 293 K. The process was exothermic because the values of ΔH were found to be negative (ΔH = −4.93, −6.49 and −5.741 kJ/mol for pAAc, 10%HEC-G-pAAc and 20%HEC-G-pAAc respectively). The adsorption process in this study is spontaneous, as clear from the negative values of ΔG, (ΔG = −4.81, −5.34 and −5.40 kJ/mol for pAAc, 10%HEC-G-pAAc and 20%HEC-G-pAAc at 293 K respectively). The adsorption process on synthesized hydrogels showed decrease in dis-orderness that was clear from its negative values.

Coordination enhanced high-seebeck coefficient n-type gel-based thermocells for low-grade energy harvesting and n-p type connected devices

Thermocells (TECs) have shown potential for commercial applications in low-grade heat harvesting, but the development of n-type TECs has always been lagging behind p-type TECs, hindering the practical utilization of integrated devices. Here, n-type and p-type TECs of polyacrylic acid (PAA) and bacterial cellulose (BC) composite hydrogel are developed, respectively. By coordinating Fe3+ with carboxyl groups, the thermal entropy difference between Fe2+ and Fe3+ increases, resulting in a record high Seebeck coefficient (S) of 2.51 mV K−1 of Fe3+/Fe2+ redox couple in n-type TEC. In p-type TEC, a S of −1.29 mV K−1 based on [Fe(CN)6]4‒/[Fe(CN)6]3‒ redox couple is achieved. The 22-pair n-p type connected device generated a voltage of 1.8 V at a temperature difference of 30 K, which is enough to power a calculator and light up an LED without an amplifier. This work offers a fresh perspective for enhancing the performance of n-type TECs and promoting the practical application of n-p type connected devices.

Investigation of electrochemical characteristics of intergel systems based on polyacrylic acid

Currently, hydrogels are polymer materials in high demand due to their physicochemical properties, and recent years have seen significant attention given to the study of their physicochemical properties [1,2]. The purpose of this research is to investigate the effect of remote interaction on the electrochemical properties of intergel systems containing hydrogels of polyacrylic acid, poly-4-vinylpyridine, poly-2-methyl-5-vinylpyridine, and polyethyleneimine hydrogels with various initial states. The dependency of conductivity and pH levels in aqueous solutions of intergel systems was examined. The obtained results have shown thatin the 5:1 ratio of the PAAswollen:P4VPdry intergel system, the conductivity of the aqueous medium reaches its maximum value after 24 hours, with a corresponding decrease in pH level. For the PAAdry:P2M5VPdry hydrogels at ratios of 5:1, 1:5, and 2:4, the high electroconductivity was observed at the sixth hour. The maximum pH value was achieved at a ratio of 4:2, indicating a low presence of nitrogen heteroatoms in the aqueous solution. The maximum conductivity in the PAAswollen:PEIswollen system at a 3:3 ratio was reached after 8.5 hours, while the pH showed its minimum value. In the study of the PAAdry:PEIdry intergel system, the pH of the aqueous medium decreased over time in all hydrogel ratios. An exception was noted at a 4:2 ratio, where pH slightly increased after 0.5 hours, then fell again, showing a deviation from the general pH trend. Conclusion. The conducted research has shown that specific conductivity varies across all molar ratios of hydrogels. It was established that changes in pairs and states of hydrogels in the intergel system affect specific conductivity, indicating the ratio of ionized and dissociated groups in the chain changes normally. These results demonstrate that these intergel systems can be used to get high-selectivity sorbents.

Exploring the potential applications of amphiphilic carbon dots based nanocomposite hydrogel in liquid chromatographic separations

BackgroundDue to their excellent stability, low toxicity, flexible modification and adjustable functionality, carbon dots (CDs) have a promising application prospect in the field of chromatographic stationary phases. Hydrogels are new functional polymer materials with three-dimensional network structure that have excellent hydrophilicity, high porosity and unique mechanical properties, which are also good candidate materials for liquid chromatography. Nevertheless, a review of the literature reveals that CDs based nanocomposite hydrogels have not yet been reported as HPLC stationary phases. ResultsIn this work, amphiphilic CDs with multiple functional groups and polyacrylic acid hydrogel were grafted to the surface of silica gel by an in-situ polymerization method, and a CDs/polyacrylic acid nanocomposite hydrogel stationary phase (CDs/hydrogel@SiO2) was prepared. CDs act as the macroscopic cross-linking agents to form a cross-linked network with polyacrylic acid chains through physical cross-linking by hydrogen bonding and chemical cross-linking by amidation and esterification reactions, which not only improve the swelling property of the hydrogel but also increase its stability. Additionally, the introduction of CDs with multifunctional groups modulates the hydrophilic-hydrophobic balance of the hydrogel that also imparts good hydrophobicity to the composite hydrogel. Through the study of retention mechanism and influencing factors, it is certificate that the CDs/hydrogel@SiO2 has mixed-mode chromatographic performance. Furthermore, the CDs/hydrogel@SiO2 column shows great potential for the determination of organic contaminants in environmental water samples. SignificanceThis work confirms the potential application of CDs/hydrogel composite for the separation of various samples and provides the possibility of developing CDs based nanocomposite hydrogel in the field of liquid chromatography. Introducing CDs into hydrogel can open up a new way for nanocomposite hydrogels to be used in HPLC, which expands the advance of hydrogel and CDs in separation field.

Synthesis of a novel clay/polyacrylic acid-tannic acid hydrogel composite for efficient removal of crystal violet dye with low swelling and high adsorption performance

Hydrogels are versatile materials with numerous applications; however, their potential in water treatment is hindered by their tendency to exhibit high swelling, degradation, and excessive water absorption. In this study, a hydrogel composed of natural clay, polyacrylic acid (PAA), and tannic acid (TA) was prepared with varying ratios of TA to control swelling ratio, reduce degradation and enhance adsorption efficiency for removal of cationic dye-contaminated wastewater. The effect of the TA ratio on the physical, chemical, and adsorption properties of prepared hydrogel (clay/PAA-TA) was studied by preparing a series of hydrogel composites and characterizing them using various techniques. The swelling ratio of pure PAA hydrogels was 7061%, but by incorporating TA into the polymer mixture, the swelling ratio decreased to less than 500%, with the lowest observed swelling of 250% occurring at a 5% tannic acid. In adsorption studies, the target pollutant was crystal violet dye (CV) and the pH effect, time effect, temperature and initial dye concentration for the adsorption CV dye were investigated using batch adsorption parameters. Adsorption studies showed that using 5% of TA is the optimal ratio to achieve the highest adsorption capacity of the prepared clay/PAA-TA to uptake CV dye. With an adsorption capacity of 444.5 mg/g, the Langmuir-Freundlich model suited the adsorption isotherm. The adsorption kinetics were best explained by the pseudo-first-order model. The results of thermodynamic studies indicated that the adsorption was spontaneous, favorable, and endothermic.

Boron nitride microfiber reinforced polyacrylic acid hydrogels with excellent self-adhesion, fast pH response, and strain sensitivity.

Hydrogels are widely utilized in the sensor field, but their inadequate adhesion presents a significant obstacle. Herein, a new multifunctional BNMFs/PAA composite hydrogel was prepared via the incorporation of one-dimensional porous boron nitride microfibers (BNMFs) and polyacrylic acid (PAA) hydrogels. BNMFs, as a reinforcing filler, play a very important role in enhancing the properties of the composite hydrogels. In particular, the porous micrometer structure plays a unique role in improving the adhesion properties of PAA hydrogels. The steric hindrance and the rich hydroxyl functional groups coming from BNMFs are key factors for the excellent adhesion of the composite hydrogels. The composite hydrogels show strong adhesion to various substrate materials. For iron plates and biological tissues, the adhesion energy can reach 1377 J m-2 and 317 J m-2, respectively. In addition, the developed BNMFs/PAA composite hydrogels exhibit excellent mechanical properties. The fracture strain of the composite hydrogels is increased by 2.4 times compared to pure PAA hydrogels. The hydrogen bonds formed between BNMFs and PAA are conducive to the mechanical properties of the BNMFs/PAA composite hydrogels. Meanwhile, BNMFs as fillers play a role in carrying and dissipating force. Furthermore, the BNMFs/PAA composite hydrogels have excellent strain and pH response characteristics. This is because the crosslinking network of the composite hydrogels becomes loose after the addition of BNMFs, resulting in rapid ion transport pathways. Therefore, the developed BNMFs/PAA composite hydrogels will have broad application prospects in the fields of motion monitoring, intelligent skin and biological adhesives.

Comprehensive analysis of cationic dye removal from synthetic and industrial wastewater using a semi-natural curcumin grafted biochar/poly acrylic acid composite hydrogel.

Polymer composites offer a tailored framework as an exceptional candidate for water treatment due to their tunable chemical structure, porous 3D architecture, physiochemical stability, accessibility, pH-sensitivity and ease of use. In this study, curcumin-engineered biochar is embedded into a cross-linked polyacrylic acid hydrogel matrix using in situ polymerization for developing a semi-natural adsorbent for the removal of cationic dye from an aqueous solution. The physicochemical features of the generated composite hydrogel are significantly influenced by the implementation of curcumin-grafted biochar into the polyacrylic acid substrate. Comprehensive characteristic approaches were employed to explore all aspects of the adsorbent's properties, especially its removal efficacy. The methodical adsorption study was accomplished by monitoring dynamic factors such as pH, adsorbent content, time frame, and initial dye concentration. The presence of the porous aromatized structure of biochar, active oxygen-enrich functional groups (carboxyl, hydroxyl, keto, enol, ether) coupled with the conjugated curcumin structure facilitate the effective establishment of hydrogen bonds, electrostatic interactions, π-π interactions, electron donor-acceptor and charge-assisted H-bonding with the malachite green (MG) and rhodamine B (Rho) molecules. The highest adsorption capacities of MG and Rho reached 521 mg g-1 and 741 mg g-1 respectively, in the range of neutral pH, considering their molecular nature, functionalities, and unique adsorption mechanisms. The isothermal modeling was carried out with Henry, Langmuir, Jovanovic, Freundlich, Temkin, and Koble-Corrigan models to determine the adsorption system. Additionally, the kinetic data were assessed with Bangham, pseudo-first-order, pseudo-second-order, intra-particle, and liquid film diffusion models to ascertain the rate-limiting phase. The Koble-Corrigan and Langmuir isotherm models (R2 > 0.997) as well as pseudo-second-order (R2 > 0.998) and Elovich (R2 = 0.983 and 0.995) kinetics models provide a substantial level of concordance with empirical findings. The analysis of non-linear diffusion models revealed that the Bangham (R2 > 0.995) pore and liquid film diffusion (R2 > 0.960) models has major influence on the rate of the adsorption procedure. The binary adsorption test demonstrated higher efficacy of the synthesized adsorbent in the removal of malachite as compared to rhodamine. This study sheds light on the design of a cost-effective semi-natural polymeric composite for treating dye-polluted wastewaters, a major milestone toward environmental and ecological sustainability.

Water retention and sustained release of magnesium-based biochar modified hydrogel composite materials

In recent years, the low utilization efficiency of fertilizers and the scarcity of freshwater resources caused by globalization have received widespread attention. To address these issues, this study used an in-situ polymerization method to prepare a magnesium-based biochar modified hydrogel slow-release fertilizer (Mg-NBC/PAA) by combining magnesium-based biochar slow-release fertilizer (Mg-NBC) with polyacrylic acid hydrogel. The composition and properties of the material were characterized using various techniques, including FT-IR, SEM, XPS, and CA. The results show that the Mg-NBC successfully entered the network structure of the hydrogel material, and the hydrogel with added biochar exhibited higher water absorption performance than the pure hydrogel, with an improvement of 47.12%. Under the optimal synthesis conditions, the maximum water absorption capacity of the material was 1395.12 ± 35.45 g/g, which can increase soil water retention and holding capacity after being added to the soil. Moreover, the material also significantly promoted the growth of maize seedlings. Therefore, Mg-NBC/PAA has the potential to be widely used in sustainable agriculture, especially in dry and semi-arid areas, due to its ability to maintain soil moisture, reduce irrigation water use, and improve nutrient utilization efficiency.