Novel Semi-IPN Nanocomposites with Functions of both Nutrient Slow-Release and Water Retention. 1. Microscopic Structure, Water Absorbency, and Degradation Performance

Effect of chain structures of monomer on hydroxyethyl cellulose-based superabsorbent properties and improvement of chickpeas plant growth of water deficit-stressed

The aim of this research was evaluation of the influence of distance between zwitterionic monomer ions on the performance of superabsorbents. For this purpose, two zwitterionic monomers 4-(3-aminopropyl) amino-4-oxo-2-butenoic acid (APOB) and 4-(6-aminohexyl) amino-4-oxo-2-butenoic acid (AHOB) were prepared and applied for synthesis of two new superabsorbents through graft copolymerization onto hydroxyethyl cellulose (HEC) in the presence of acrylic acid (AA). In synthesis of superabsorbents factors such as the highest water absorbency capacity, absorbency rate, gel strength, and environmental problems should be resolved or improved. The results demonstrated that the water absorbency capacity and rate parameters (τ) of HEC-g-p(AA-co-APOB) and HEC-g-p(AA-co-AHOB) in distilled water were 986.62, 664.38 g/g, and 98.04, 140.84 min, respectively. The biodegradability of HEC-g-p(AA-co-APOB) was approximately 4 times more than HEC-g-p(AA-co-AHOB). However, based on the rheological analyses (G'/G″) HEC-g-p(AA-co-AHOB) was stronger than the other. Additionally, studies of water retention on soil containing HEC-g-p(AA-co-AHOB) superabsorbent (soil with 0.25 wt% material) showed that the after 30 days has ≤5 % water while soil in the absence of superabsorbent after 10 days completely dried. Studies of the growth of plants in soil demonstrated in the presence of HEC-g-p(AA-co-AHOB) the average length of shoots was 36 cm while without superabsorbent were 25 cm.

A Comprehensive Review of Polysaccharide-Based Hydrogels as Promising Biomaterials

Polysaccharides have emerged as a promising material for hydrogel preparation due to their biocompatibility, biodegradability, and low cost. This review focuses on polysaccharide-based hydrogels' synthesis, characterization, and applications. The various synthetic methods used to prepare polysaccharide-based hydrogels are discussed. The characterization techniques are also highlighted to evaluate the physical and chemical properties of polysaccharide-based hydrogels. Finally, the applications of SAPs in various fields are discussed, along with their potential benefits and limitations. Due to environmental concerns, this review shows a growing interest in developing bio-sourced hydrogels made from natural materials such as polysaccharides. SAPs have many beneficial properties, including good mechanical and morphological properties, thermal stability, biocompatibility, biodegradability, non-toxicity, abundance, economic viability, and good swelling ability. However, some challenges remain to be overcome, such as limiting the formulation complexity of some SAPs and establishing a general protocol for calculating their water absorption and retention capacity. Furthermore, the development of SAPs requires a multidisciplinary approach and research should focus on improving their synthesis, modification, and characterization as well as exploring their potential applications. Biocompatibility, biodegradation, and the regulatory approval pathway of SAPs should be carefully evaluated to ensure their safety and efficacy.

Synthesis of Cellulose-Poly(Acrylic Acid) Using Sugarcane Bagasse Extracted Cellulose Fibres for the Removal of Heavy Metal Ions

In this study, sugarcane bagasse (SCB) was treated with sodium hydroxide and bleached to separate the non-cellulose components to obtain cellulose (CE) fibres. Cross-linked cellulose-poly(sodium acrylic acid) hydrogel (CE-PAANa) was successfully synthesised via simple free-radical graft-polymerisation to remove heavy metal ions. The structure and morphology of the hydrogel display an open interconnected porous structure on the surface of the hydrogel. Various factors influencing batch adsorption capacity, including pH, contact time, and solution concentration, were investigated. The results showed that the adsorption kinetics were in good agreement with the pseudo-second-order kinetic model and that the adsorption isotherms followed the Langmuir model. The maximum adsorption capacities calculated by the Langmuir model are 106.3, 333.3, and 163.9 mg/g for Cu(II), Pb(II), and Cd(II), respectively. Furthermore, X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectrometry (EDS) results demonstrated that cationic exchange and electrostatic interaction were the main heavy metal ions adsorption mechanisms. These results demonstrate that CE-PAANa graft copolymer sorbents from cellulose-rich SCB can potentially be used for the removal of heavy metal ions.

Nanocomposite-based smart fertilizers: A boon to agricultural and environmental sustainability

Fertilizers are indispensable agri-inputs to accomplish the growing food demand. The injudicious use of conventional fertilizer products has resulted in several environmental and human health complications. To mitigate these problems, nanocomposite-based fertilizers are viable alternative options. Nanocomposites, a novel class of materials having improved mechanical strength, barrier properties, and mechanical and thermal stability, are suitable candidates to develop eco-friendly slow/controlled release fertilizer formulations. In this review, the use of different nanocomposite materials developed for nutrient management in agriculture has been summarized with a major focus on their synthesis and characterization techniques, and application aspects in plant nutrition, along with addressing constraints and future opportunities of this domain. Further detailed studies on nanocomposite-based fertilizers are required to evaluate the cost-effective synthesis methods, in-depth field efficacy, environmental fate, stability, etc. before commercialization in the field of agriculture. The present review is expected to help the policy makers and all the stakeholders in the large-scale commercialization and application of nanocomposite-based smart fertilizer products with greater societal acceptance and environmental sustainability in near future.

Preparation and Characterization of a Novel Cassava Starch-Based Phosphorus Releasing Super-Absorbent Polymer, and Optimization of the Performance of Water Absorption and Phosphorus Release

To prepare a novel cassava starch-based phosphorus releasing super-absorbent polymer (CST-PRP-SAP), the single factor and orthogonal experiment were applied to analyze the effects of different reaction conditions on the absorption and phosphorus release capacities of CST-PRP-SAP samples. The structural and morphological characteristics of the cassava starch (CST), powdered rock phosphate (PRP), cassava starch-based super-absorbent polymer (CST-SAP) and CST-PRP-SAP samples were all compared with various technologies, such as the Fourier transform infrared spectroscopy and X-ray diffraction pattern, etc. The results showed that the CST-PRP-SAP samples had good performances of water retention and phosphorus release which were synthesized, such as the reaction temperature, starch content, P₂O₅ content, crosslinking agent, initiator, neutralization degree, and acrylamide content, which were 60 °C, 20% w/w, 10% w/w, 0.02% w/w, 0.6% w/w, 70% w/w, and 15% w/w, respectively. The water absorbency of CST-PRP-SAP was almost larger than that of the CST-SAP sample with a P₂O₅ content of 5.0% and 7.5%, and they all gradually decreased after three consecutive water absorption cycles. The CST-PRP-SAP sample could maintain about 50% of the initial water content after 24 h, even at the temperature of 40 °C. The swelling process of CST-PRP-SAP conformed to the non-Fickian diffusion, which was determined by the diffusion of water molecules and the relaxation process of polymer chain segments. The cumulative phosphorus release amount and release rate of the CST-PRP-SAP samples were increased with the increasing PRP content and the decreasing neutralization degree. After a 216 h immersion, the cumulative phosphorus release amount and release rate of the CST-PRP-SAP samples with different PRP contents were increased by 17.4 and 3.7 times, respectively. The rough surface of the CST-PRP-SAP sample after swelling was beneficial to the performance of water absorption and phosphorus release. The crystallization degree of PRP in the CST-PRP-SAP system was decreased and most of the PRP existed in the form of physical filling, and the available phosphorus content was increased to a certain extent. It was concluded that the CST-PRP-SAP synthesized in this study has excellent properties of continuous water absorption and retention with functions of promotion and the slow-release phosphorus.

Cellulose/nanocellulose superabsorbent hydrogels as a sustainable platform for materials applications: A mini-review and perspective

Superabsorbent hydrogels (SAH) are crosslinked three-dimensional networks distinguished by their super capacity to stabilize a large quantity of water without dissolving. Such behavior enables them to engage in various applications. Cellulose and its derived nanocellulose can become SAHs as an appealing, versatile, and sustainable platform because of abundance, biodegradability, and renewability compared to petroleum-based materials. In this review, a synthetic strategy that reflects starting cellulosic resources to their associated synthons, crosslinking types, and synthetic controlling factors was highlighted. Representative examples of cellulose and nanocellulose SAH and an in-depth discussion of structure-absorption relationships were listed. Finally, various applications of cellulose and nanocellulose SAH, challenges and existing problems, and proposed future research pathways were listed.

Bagasse Cellulose Composite Superabsorbent Material with Double-Crosslinking Network Using Chemical Modified Nano-CaCO3 Reinforcing Strategy

To improve the salt resistance of superabsorbent materials and the gel strength of superabsorbent materials after water absorption, a bagasse cellulose-based network structure composite superabsorbent (CAAMC) was prepared via graft copolymerization of acrylamide/acrylic acid (AM/AA) onto bagasse cellulose using silane coupling agent modified nano-CaCO₃ (MNC) and N,N′-methylene bisacrylamide (MBA) as a double crosslinker. The acrylamide/acrylic acid was chemically crosslinked with modified nano-CaCO₃ by C-N, and a stable double crosslinked (DC) network CAAMC was formed under the joint crosslinking of N,N′-methylene bisacrylamide and modified nano-CaCO₃. Modified nano-CaCO₃ plays a dual role of crosslinking agent and the filler, and the gel strength of composite superabsorbent is two times higher than that of N,N′-methylene bisacrylamide single crosslinking. The maximum absorbency of CAAMC reached 712 g/g for deionized water and 72 g/g for 0.9 wt% NaCl solution. The adsorption process of CAAMC was simulated by materials studio, and the maximum adsorption energy of amino and carboxyl groups for water molecules is −2.413 kJ/mol and −2.240 kJ/mol, respectively. According to the results of CAAMC soil water retention, a small amount of CAAMC can greatly improve the soil water retention effect.

Synthesis of cellulose-based superabsorbent hydrogel with high salt tolerance for soil conditioning

In this study, cellulose-based superabsorbent hydrogel was synthesized from sodium carboxymethyl cellulose (CMC-Na), acrylic acid (AA), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) to enhance its water absorbency and salt tolerance for soil-conditioning applications in areas suffering from drought and soil salinization. Superabsorbent hydrogels (SHs) were prepared by CMC-Na and AMPS successfully, using chemical graft technology. Structure, morphology, thermal stability, and water absorbency of SHs were deduced. The cellulose-based hydrogel showed a high salt tolerance that the maximum water absorbency reached 604 and 119% in distilled water and saline water, respectively. The swelling behavior in aqueous solvents indicated that the water absorption of hydrogels was improved with the increasing ratio of CMC-Na. All SHs exhibited adsorption of nitrogen with the maximum adsorption of ammonia nitrogen 30 mg·g^-1 and the presence of hydrogels could slow down the loss of nutrients in the soil. This study provided a feasible strategy that AMPS was substituted by CMC-Na to synthesize SHs with strong water absorbency and high salt tolerance which could be efficiently applied in agriculture as a soil conditioner.

Biodegradation of novel bioplastics made of starch, polyhydroxyurethanes and cellulose nanocrystals in soil environment

Plastic pollution is recognized as a major environmental problem in many countries. Over the last decade, academics have embraced research on bioplastics to discover newer high-end green materials. However, the end-of-life environmental fate of such materials is not adequately understood. Non-isocyanate polyhydroxyurethanes (PHUs) are green engineering materials with huge potential to replace traditional polyurethanes. Despite this immense potential, a number of questions about their environmental fate remain unanswered. The present study investigated the extent and mechanisms underlying soil biodegradation of PHUs and determined whether the deterioration of PHUs within starch bioplastics (ST) can improve the biodegradation of starch (ST)-PHU hybrids. Soil microbiomes managed to effectively and quickly digest not only PHUs but also ST-PHU hybrids. All ST-PHU hybrids were characterized by exceptional biodegradability with mass losses of up to ~88% following a soil burial time of only 120 days. The biodegradation of ST-alone bioplastics was 69% under identical conditions. The presence of cellulose nanocrystals (CNC) reduced the potential for the soil microbial community to degrade nanohybrids (ST-PHU-CNC). Microbially digested bioplastics with PHU presented less stages of thermal degradation, and reduced intensities of FTIR, NMR and XPS signals compared to the original films, indicating improvement of the biodegradation mechanism. These findings suggested the positive environmental implications of PHU in improving the bioplastic's degradation and their potential for future applications.

Biochar-based slow-release of fertilizers for sustainable agriculture: A mini review

Increasing global population and decreasing arable land pose tremendous pressures to agricultural production. The application of conventional chemical fertilizers improves agricultural production, but causes serious environmental problems and significant economic burdens. Biochar gains increasing interest as a soil amendment. Recently, more and more attentions have been paid to biochar-based slow-release of fertilizers (SRFs) due to the unique properties of biochar. This review summarizes recent advances in the development, synthesis, application, and tentative mechanism of biochar-based SRFs. The development mainly undergoes three stages: (i) soil amendment using biochar, (ii) interactions between nutrients and biochar, and (iii) biochar-based SRFs. Various methods are proposed to improve the fertilizer efficiency of biochar, majorly including in-situ pyrolysis, co-pyrolysis, impregnation, encapsulation, and granulation. Considering the distinct features of different methods, the integrated methods are promising for fabricating effective biochar-based SRFs. The in-depth understanding of the mechanism of nutrient loading and slow release is discussed based on current knowledge. Additionally, the perspectives and challenges of the potential application of biochar-based SRFs are described. Knowledge surveyed from this review indicates that applying biochar-based SRFs is a viable way of promoting sustainable agriculture.

Recent Advances in Plant Nanoscience

Plants have complex internal signaling pathways to quickly adjust to environmental changes and harvest energy from the environment. Facing the growing population, there is an urgent need for plant transformation and precise monitoring of plant growth to improve crop yields. Nanotechnology, an interdisciplinary research field, has recently been boosting plant yields and meeting global energy needs. In this context, a new field, "plant nanoscience," which describes the interaction between plants and nanotechnology, emerges as the times require. Nanosensors, nanofertilizers, nanopesticides, and nano-plant genetic engineering are of great help in increasing crop yields. Nanogenerators are helping to develop the potential of plants in the field of energy harvesting. Furthermore, the uptake and internalization of nanomaterials in plants and the possible effects are also worthy of attention. In this review, a forward-looking perspective on the plant nanoscience is presented and feasible solutions for future food shortages and energy crises are provided.

A new class of biochar-based slow-release phosphorus fertilizers with high water retention based on integrated co-pyrolysis and co-polymerization

The development of slow-release phosphorus fertilizers (SRFs) with high water retention is of significance for modern agriculture. Herein, a new class of biochar-based SRFs are developed by an integrated co-pyrolysis and co-polymerization process (PSRFs). The water-retention performance and P slow-release behavior of PSRFs are evaluated, which are compared with other types of biochar-based SRFs derived from biochar-based phosphorus adsorption (MSRFs), co-pyrolysis of biomass-bentonite-nutrients (BSRFs), and the application of coating on BSRFs (CSRFs). The results show that the obtained PSRFs exhibits high water retention with the maximum swelling capacity of 94.2 g/g, far outstripping other tested SRFs. The water-retention performance of PSRFs is found to be positively correlated with their crosslinking agent contents. In addition, PSRFs has excellent P slow-release performance which is comparable with CSRFs (~51.5% of P release after 30 days), but much better than MSRFs and BSRFs with a complete P release after 30 days. Furthermore, pot experiments reveal that PSRFs has the highest P utilization efficiency (75.83% after 60 days), which can promote the growth of pepper seedlings better than other SRFs. Moreover, the soil burial tests indicate that PSRFs has a good biodegradability with the degradation ratio of 33.46% in 75 days. Finally, biological abundance analysis further reveals that Actinobacteria in soil is mainly responsible for the metabolism of starch and sodium alginate in PSRFs.

A potential Mg-enriched biochar fertilizer: Excellent slow-release performance and release mechanism of nutrients

A potential Mg-enriched biochar fertilizer (MBF) was successfully synthesized via pyrolysis of MgCl₂-enriched corn straw and high-efficiency reclaiming of N- and P-containing nutrients from biogas effluent. Mathematical modeling and column leaching method demonstrated that the MBF exhibited excellent slow-release performances of total P and N with sustainable release rates. Leaching experiment indicated that the final accumulative release ratios of N and P from MBF were 7 times and 6 times lower than those of chemical fertilizer (CF), respectively. The mechanism study reveals that the P-release performance of MBF was not only controlled by the low solubility of MgP precipitates formed on the biochar surface, but also enhanced by the 'P-trap' effect of MgO through re-precipitation process of PO₄^3-. Meanwhile, the N-release behavior of MBF was dominated by the multi-effects of biochar carrier, including the confinement effect and electrostatic attraction for NH₄⁺, as well as the hydrogen bonds and pore-filling effect for N-containing organic matter. In addition, MBF significantly promoted the corn growth and enhanced the nutrient uptake efficiency of corn. These results suggested that MBF may therefore have promising potential in sustainable agriculture application with multiple environmental benefits.

Mussel-inspired agarose hydrogel scaffolds for skin tissue engineering

Polysaccharide hydrogels are widely used in tissue engineering because of their superior biocompatibility and low immunogenicity. However, many of these hydrogels are unrealistic for practical applications as the cost of raw materials is high, and the fabrication steps are tedious. This study focuses on the facile fabrication and optimization of agarose-polydopamine hydrogel (APG) scaffolds for skin wound healing. The first study objective was to evaluate the effects of polydopamine (PDA) on the mechanical properties, water holding capacity and cell adhesiveness of APG. We observed that APG showed decreased rigidity and increased water content with the addition of PDA. Most importantly, decreased rigidity translated into significant increase in cell adhesiveness. Next, the slow biodegradability and high biocompatibility of APG with the highest PDA content (APG3) was confirmed. In addition, APG3 promoted full-thickness skin defect healing by accelerating collagen deposition and promoting angiogenesis. Altogether, we have developed a straightforward and efficient strategy to construct functional APG scaffold for skin tissue engineering, which has translation potentials in clinical practice.

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Agarose-polydopamine hydrogel scaffold was developed via a simple two-step approach.

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In vitro and in vivo experiments show that the scaffold holds biocompatibility and biodegradability.

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The cell migration rate on the scaffold is high and cells can migrate from the surface to the inside of scaffold.

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The scaffold can facilitate wound healing by promoting collagen deposition and angiogenesis.

Positron annihilation spectroscopic characterization of free-volume defects and their correlations with the mechanical and transport properties of SBR-PMMA interpenetrating polymer networks

A series of interpenetrating polymer networks (IPNs) and semi-interpenetrating polymer networks (s-IPNs) of styrene butadiene rubber (SBR) and poly(methyl methacrylate) (PMMA) have been synthesized by adopting the sequential interpenetration and in situ polymerization method. The size and the concentration of free volume defects in these systems are monitored and their variations accurately traced using positron annihilation lifetime (PALS) and coincidence Doppler broadening spectroscopic (CDBS) measurements. The morphologies of the IPNs were analyzed with transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Confocal Raman mapping had been employed to elucidate the mechanism of PMMA interpenetration in the SBR matrix with reference to the blend ratio. The results of free volume analysis lead to the conclusion that the increase of PMMA content in IPN was accompanied by enhancement of interpenetration in the system. Also the morphology changes from dispersed island pattern to a co-continuous one. Besides, the transport parameters and mechanical behavior of IPNs were studied in detail. The results of PALS and CDBS measurements have found to exhibit striking correlations with the sorption, mechanical properties and morphology of the polymer networks. The specific physics involved in the characterization protocol is effectively utilized to explore the chemistry of IPN formation. This new modality of characterization versus composition uplifts and widens the application prospects of elastomer-thermoplastic IPNs.

Novel Semi-IPN Nanocomposites with Functions of both Nutrient Slow-Release and Water Retention. 2. Effects on Soil Fertility and Tomato Quality

So far, the effects of the semi-interpenetrating polymer network (semi-IPN) composites with functions of both nutrient slow-release and water retention on soil physicochemical properties, yield, and quality of crops have not been studied. In Part 1 of this paper ( Song, J.; Zhao, H.; Zhao, G.; Xiang, Y.; Liu, Y. J. Agric. Food Chem. 2019 , DOI: 10.1021/acs.jafc.9b00888 ), superabsorbent polymers SAP_WS (grafting wheat straw (WS) to poly(acrylic-co-acrylamide), which is WS-g-P(AA-co-AM)) and SAP_HEC (HEC (hydroxyethyl cellulose)-g-P(AA-co-AM)), and their semi-IPN nanocomposites SI-PSRF/SAP_WS and SI-PSRF/SAP_HEC (formed by chemical bonding of SAP_WS or SAP_HEC with PSRF (NPK-containing polymeric slow-release fertilizer)) were prepared, and their microstructures and degradation performances were systematically studied. In this study, effects of these two nanocomposites on soil physicochemical properties, crop yield, and quality as well as soil fertility, especially the relationships between these effects and the degradation performances of the materials themselves, were investigated by a pot experiment of the tomato. Results show that SI-PSRF/SAP nanocomposites can regulate the pH values of weak alkaline soils close to 7.0. The changes of soil pH values, in our study, are basically synchronized with the degradation rates of SI-PSRF/SAP, the higher the degradation rate of SI-PSRF/SAP, the lower the pH value of the alkaline soil treated. Compared with PSRF+SAP (the simple physically mixed system of PSRF and SAP) and PSRF, during the whole growth period of the tomato, SI-PSRF/SAP treatments have the lowest nitrogen release amounts, 4.74 g for SI-PSRF/SAP_WS and 4.88 g for SI-PSRF/SAP_HEC, the highest nitrogen contents of soils after day 40, and the highest nitrogen contents of plants on day 100, 1.16 and 1.68 g for SI-PSRF/SAP_WS and 1.26 and 1.86 g for SI-PSRF/SAP_HEC. While for PSRF+SAP_WS, PSRF+SAP_HEC, and PSRF, they are 5.16 g, 0.81 g, 0.63 g and 5.26 g, 0.87 g, 0.66 g and 5.17 g, 0.63 g, 0.52 g, respectively. There is a significant positive correlation between the material degradation rates and their nitrogen release amounts in this study, while SI-PSRF/SAP systems have the highest correlation coefficient, 0.950. In addition, compared to the control blank, the SI-PSRF/SAP system significantly increases tomato yield, 270.1% for SI-PSRF/SAP_WS and 301.7% for SI-PSRF/SAP_HEC. Compared with PSRF+SAP, the SI-PSRF/SAP system can make the soil treated become a high-quality soil by influencing the soil pH value, conductivity, cation exchange capacity, and the contents of nitrogen, phosphorus, organic carbon, and active organic carbon, which have significant impact on the soil quality. The chemical-bonded functional nanocomposites with a semi-IPN three-dimensional network structures formed by hydrogen-bonding interactions among functional groups of their components can more efficiently improve soil fertility, increase soil nutrient supply capacity, and promote plants growth and development as well as solve the environmental pollution caused by traditional fertilizers. The technology reported in this paper is simple and feasible for large-scale production of fertilizer with both water retention and nutrient slow-release, even nanofertilizer, which has great application potential.