Superabsorbent nanocomposite based on maize bran with integration of water-retaining and slow-release NPK fertilizer

Preparation of superabsorbent composite(s) based on dialdehyde cellulose extracted from banana fiber waste

The study focus is the valorization of banana agriculture by products by the extraction and derivatization of cellulose and its incorporation in formulations to produce superabsorbent materials endowed with high water absorption performances. The extracted cellulose (BP) was subjected to a controlled oxidation by sodium periodate to convert it to cellulose dialdehyde (DAC) with controlled aldehyde content. The cellulosic materials were incorporated into a suspension containing acrylic acid (AA) and itaconic acid (IA) to produce composite hybrid hydrogels (SA-BP/SA-DAC) by radical chain polymerization in water, using N,N-methylene-bis-acrylamide (MBA) as a cross-linking agent and potassium persulfate (KPS) as an initiator. The prepared materials were characterized using techniques such as Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and rheological analysis. Additionally, the absorption and re-swelling capacities of the superabsorbent composites (SAPs) were assessed through kinetic studies in water and NaCl solution. Notably, dialdehyde cellulose (DAC), due to its low crystallinity index, hydrophilicity (attributed to aldehyde and hemiacetal functions), and high polarity, holds promise for enhancing the swelling and water retention capacity of the hydrogel. A water absorption capacity as high as 1240±60 g.g-1 was obtained for SA-DAC with a DAC content of 5 %wt. Additionally, the reusability of the SAPs was evidenced.

Recent Advances in Superabsorbent Hydrogels Derived from Agro Waste Materials for Sustainable Agriculture: A Review

Superabsorbent hydrogels made from agro waste materials have the potential to promote sustainable agriculture and environmental sustainability. These hydrogels not only help reduce water consumption and increase crop yields but also contribute to minimizing waste and lowering greenhouse gas emissions. Recent research on superabsorbent hydrogels derived from agro wastes has focused on the preparation of hydrogels based on natural polymers isolated from agro wastes, such as cellulose, hemicellulose, and lignin. This review provides an in-depth examination of hydrogels developed from raw agro waste materials and natural polymers extracted from agro wastes, highlighting that these studies start with raw wastes as the main materials. The utilization strategies for specific types of agro wastes are comprehensively described. This review outlines different methods utilized in the production of these hydrogels, including physical cross-linking techniques such as dissolution-regeneration and freeze-thawing, as well as chemical cross-linking methods involving various cross-linking agents and graft polymerization techniques such as free radical polymerization, microwave-assisted polymerization, and γ radiation graft polymerization. Specifically, this review explores the applications of agro waste-based superabsorbent hydrogels in enhancing soil properties such as water retention and slow-release of fertilizers for sustainable agriculture.

Rational Design of a Multifunctional Hydrogel Trap for Water and Fertilizer Capture: A Review

Water scarcity and land infertility pose significant challenges to agricultural development, particularly in arid and semiarid regions. Improving soil-water-retention capacity and fertilizer utilization efficiency through the application of soil additives has become a pivotal approach in agricultural practices. Hydrogels exhibit exceptional water absorption and fertilizer retention capabilities, making them extensively utilized in the fields of agriculture, forestry, and desert control. Currently, most reviews primarily focus on the raw materials, classification, synthesis methods, and application prospects of hydrogels, with limited attention given to strategies for enhancing water-retention performance, mechanisms underlying fertilizer absorption, and environmental risks. This review covers the commonly used cross-linking methods in hydrogel synthesis and the structure-activity relationship between hydrogels and water as well as fertilizer. Additionally, a thorough analysis of the ecological benefits and risks associated with hydrogels is presented. Finally, future prospects and challenges are delineated from the perspectives of material design and engineering applications.

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.

Superabsorbent hydrogels based on natural polysaccharides: Classification, synthesis, physicochemical properties, and agronomic efficacy under abiotic stress conditions: A review

Superabsorbent polymers (SAPs) are a class of polymers that have attracted tremendous interest due to their multifunctional properties and wide range of applications. The importance of this class of polymers is highlighted by the large number of publications, including articles and patents, dealing with the use of SAPs for various applications. Within this framework, this review provides an overview of SAPs and highlights various key aspects, such as their history, classification, and preparation methods, including those related to chemically or physically cross-linked networks, as well as key factors affecting their performance in terms of water absorption and storage. This review also examines the potential use of polysaccharides-based SAPs in agriculture as soil conditioners or slow-release fertilizers. The basic aspects of SAPs, and methods of chemical modification of polysaccharides are presented and guidelines for the preparation of hydrogels are given. The water retention and swelling mechanisms are discussed in light of some mathematical empirical models. The nutrient slow-release kinetics of nutrient-rich SAPs are also examined on the basic of commonly used mathematical models. Some examples illustrating the advantages of using SAPs in agriculture as soil conditioners and agrochemical carriers to improve crop growth and productivity are presented and discussed. This review also attempts to provide an overview of the role of SAPs in mitigating the adverse effects of various abiotic stresses, such as heavy metals, salinity, and drought, and outlines future trends and prospects.

Cellulosic wastepaper modified starch/ itaconic acid/ acrylic acid-based biodegradable hydrogel as a sustain release of NPK fertilizer vehicle for agricultural applications

In this work, wastepaper powder was used as a modifying agent for a biodegradable hydrogel composite of starch, itaconic acid, and acrylic acid. After the addition of an optimum amount of the modifying agent, the swelling ability of the hydrogel was enhanced from 503 g/g to 647 g/g. Further, the hydrogel was also used for sustained release of NPK fertilizer and subsequent effect of the fertilizer loaded hydrogel in okra seed germination was also studied. The NPK loaded-hydrogel showed good sustained-release behavior and 98 % of N, 81 % of P and 95 % of K release were observed after 20th day of incubation. Moreover, the release study was explained by using different kinetic models. In seed germination study, a higher and faster germination rate for okra seeds was observed in case of NPK loaded hydrogel compared to the control system, which was attributed to the synergistic effect of essential macronutrients (N, P, and K) and water that were inside the hydrogel. Most importantly, the hydrogel was found to be biodegradable by using soil burial method and further confirmed by FTIR and SEM analyses. Thus, this work provides an efficient way for utilization of wastepaper in the production of a biodegradable hydrogel for agricultural applications.

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.

Environmentally friendly hydrogel: A review of classification, preparation and application in agriculture

Superabsorbent hydrogel (SH) is three-dimensional (3D) cross-linked hydrophilic polymer that can absorb and retain large quantities of water or other aqueous solutions. SH is made of water-affinity monomers and is widely used in biomedicine, wastewater treatment, hygiene and slow-release fertilizers (SRFs). This article focused on the preparation methods of SH, superabsorbent hydrogel composite and the application of SH in agriculture. By selecting various synthetic technologies and cross-linking agents, a series of chemical cross-linking or physical networks can be designed and tailored to meet specific applications. In view of the excellent characteristics of water absorption, biodegradability, water retention and slow-release capacity, SH occupies a dominant position in the SRFs market. In this work, the agricultural application of SH in double coated SRFs and nutrients carriers is also discussed. Some mechanisms related to the nutrient release were analyzed by mathematical models. In addition, some agronomic benefits of using superabsorbent hydrogels in improving water absorption, water holding capacity and increasing crop yields were also discussed. Although SH has certain shortcomings, from the perspective of long-term development, it will further show great potential in sustainable agriculture.

Fe3O4-urea nanocomposites as a novel nitrogen fertilizer for improving nutrient utilization efficiency and reducing environmental pollution

Almost 81% of nitrogen fertilizers are applied in form of urea but most of it is lost due to volatilization and leaching leading to environmental pollution. In this regard, slow-release nano fertilizers can be an effective solution. Here, we have synthesized different Fe₃O₄-urea nanocomposites with Fe₃O₄ NPs: urea ratio (1:1, 1:2, 1:3) ie. NC-1, 2, and 3 respectively, and checked their efficacy for growth and yield enhancement. Oryza sativa L. cv. Swarna seedlings were treated with different NCs for 14 days in hydroponic conditions and significant up-regulation of photosynthetic efficiency and nitrogen metabolism were observed due to increased availability of nitrogen and iron. The discriminant functional analysis confirmed that the NC3 treatment yielded the best results so further gene expression studies were performed for NC-3 treated seedlings. Significant changes in expression profiles of ammonia and nitrate transporters indicated that NC-3 treatment enhanced nitrogen utilization efficiency (NUE) due to sustained slow release of urea. From pot experiments, we found significant enhancement of growth, grain nutrient content, and NUE in NC supplemented sets. 1.45 fold increase in crop yield was achieved when 50% N was supplemented in form of NC-3 and the rest in form of ammonium nitrate. NC supplementation can also play a vital role in minimizing the use of bulk N fertilizers because, when 75% of the recommended N dose was supplied in form of NC-3, 1.18 fold yield enhancement was found. Thus our results highlight that, slow-release NC-3 can play a major role in increasing the NUE of rice.

Materials diversity of hydrogel: Synthesis, polymerization process and soil conditioning properties in agricultural field

BACKGROUND

The cumulative influence of global warming, climate abrupt changes, growing population, topsoil erosion is becoming a threatening alarm for facing food challenges and upcoming global water issues. It ultimately affects the production of food in a water-stressed environment and slows down the production with more consumption of fertilizers by plants. The superabsorbent hydrogels (SAHs) have extensive applications in the agricultural field and proved very beneficial for plant growth and soil health. These polymeric materials are remarkably distinct from hygroscopic materials owing to their multidimensional network structure. It retains a lot of water in its 3D network and releases it slowly along with nutrients to plant in stressed environment.

AIM OF REVIEW

A soil conditioner boosts up the topology, compactness, and mechanical properties (swelling, water retention, and slow nutrient release) of soil. The superabsorbent hydrogel plays an astonishing role in preventing the loss of nutrients during the heavy flow of rainwater from the upper surface of soil because these SAHs absorb water and get swollen to keep water for longer time. The SAHs facilitate the growth of plants with limited use of water and fertilizers. Beyond, it improves the soil health and makes it fertile in horticulture and drought areas.

KEY SCIENTIFIC CONCEPT OF REVIEW

The SAHs can be synthesized through grafting and cross-linking polymerization to introduce value-added features and extended network structure. The structure of superabsorbent hydrogel entirely based on cross-linking that prompts its use in the agricultural field as a soil conditioner. The properties of a SAHs vary due to its nature of constituents, polymerization process (grafting or cross-linking), and other parameters. The use of SAHs in agricultural field comparatively enhances the swelling rate up to 60-80%, maximum water retaining, and slowly nutrient release to plants for a longer time.

Synthesis of a novel superabsorbent with slow-release urea fertilizer using modified cellulose as a grafting agent and flexible copolymer

In this work, a number of glucose unites in polymeric structure of cellulose was converted to 2,4-dihydroxy-3-(1-hydroxy-2-oxoethoxy)butanal (cellulose containing di aldehyde units (CCDAUs)) by oxidation with sodium periodate, followed by condensation with acetone to produce 5,7-dihydroxy-6-((1-hydroxy-4-oxopent-2-en-1-yl)oxy)hept-3-en-2-one unites (cellulose containing di ene units (CCDEUs)). This modified cellulose was characterized by different methods and applied as a copolymer and grafting agent to synthesize an eco-friendly (CCDEUs-g-poly(AA)/urea) superabsorbent with slow-release urea fertilizer. The created double bonds in C₂ and C₃ positions of β-d-glucose units increased the linkage between cellulose and acrylic acid, leading to the formation of a strong network for slow-release urea fertilizer. Also, this modification created an expanded network for storage a high amount of water by increasing the cellulose flexibility. The reaction conditions for modification and synthesis of the superabsorbent, the oxidation degree value of glucose units, kinetics models, the effect of different saline solutions, various pH and reswelling time on the water absorbency, water retention capacity, reusability, biodegradability, and slow-release property were investigated. Also, the effect of synthesized CCDEUs-g-poly(AA)/urea on plant growth was tested and excellent results were obtained.

Study on Seed Emergence and Seedling Growth of Artemisia Desertorum with Superabsorbent Polymers

In this study, the emergence rate, emergence potential, root length, stem length, water consumption, and biomass around a root system were used as evaluation indexes, and we used the laboratory-prepared super absorbent resin watermelon rind (WMR)-p (AA-co-DAAM) (superabsorbent polymer 1-SAP₁), WMR-p (AA-co-DAAM)/palygorskite (PGS) (SAP₂) in a laboratory and commercially available water-retaining agents (SAP_RX and SAP_HDB) to assist the emergence of Artemisiadesertorum seeds and seedling growth; then, their water absorption and thermal stability were discussed. The results showed that the thermal stability of an SAP prepared in the laboratory and the water consumption during seed emergence, root length, and stem length after emergence were better than those of an SAP purchased on the market, and this information could help to promote the emergence and seedling growth of Artemisiadesertorum. While enhancing the drought resistance of plants, using a laboratory-produced SAP can effectively reduce the number of artificial irrigations.

Nanocomposites for Delivering Agrochemicals: A Comprehensive Review

Excessive application of fertilizers negatively affects soil health, causes low nutrient utilization efficiency in plants, and leads to environmental pollution. The application of controlled-release fertilizer is gaining momentum to overcome this crisis. Engineered nanocomposites (ENCs) have shown tremendous promise for need-based delivery of agrochemicals (macro- and micronutrients, pesticides, and other agrochemicals). This review provides comprehensive coverage of synthesis of nanocomposites, their physical-chemical characterization, and techniques to achieve sustained release and targeted delivery to the crops, emphasizing their beneficial role in plant production and protection. Related aspects like feasibility of the application, commercialization of the nanoformulations, and biosafety concerns are also highlighted. This will be helpful to develop a critical understanding of the current state of the art in the controlled release of agrochemicals through nanocomposites. The pressing issues like scale up production, cost analyses, field-based trials, and environmental safety concerns should be given greater attention in future studies.

Slow release fertilizer hydrogels: a review

Slow release fertilizer hydrogels combine fertilizer and hydrogel into one system.