Biodegradable poly(lactic acid)/cellulose-based superabsorbent hydrogel composite material as water and fertilizer reservoir in agricultural applications

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.

Urea intercalated encapsulated microalgae composite hydrogels for slow-release fertilizers

In agriculture, hydrogels can be addressed for effective operation of water and controlled-release fertilizers. Hydrogels have a significant ability for retaining water and improving nutrient availability in soil, enhancing plant growth while reducing water and fertilizer usage. This work aimed to prepare a hydrogel composite based on microalgae and biopolymers including chitosan and starch for use as a soil conditioner. The hydrogel composite was characterized by FTIR, XRD, and SEM. All hydrogel properties were studied including swelling degree, biodegradability, water-holding capacity, water retention, and re-swelling capacity in soil and water. The urea fertilizer loading and releasing behavior of the prepared hydrogels were investigated. The results revealed that the range of the maximal urea loading was between 99 and 440%, and the kinetics of loading was fitted with Freundlich model. The urea release % exhibited 78-95%, after 30 days, and the kinetics of release was fitted with zero-order, Higuchi, and Korsmeyer-Peppas models. Furthermore, the prepared hydrogels obtained a significant water-holding capacity, after blending soil (50 g) with small amount of hydrogels (1 g), the capacity increased in the range of 99.4-101.5%. In sum, the prepared hydrogels have the potential to be applied as a soil conditioner.

Urea-rich sodium alginate-based hydrogel fertilizer as a water reservoir and slow-release N carrier for tomato cultivation under different water-deficit levels

In this study, a new eco-friendly urea-rich sodium alginate-based hydrogel with a slow-release nitrogen property was prepared, and its effectiveness was evaluated in the cultivation of tomato plants under different water stress levels. The structure and performance of the hydrogel were investigated by FTIR, XRD, TGA, DTG, and SEM. The swelling and release experiments showed that prepared urea-rich hydrogel exhibited a high-water holding capacity (412 ± 4 g/g) and showed a sustained and slow nitrogen release property. A greenhouse pot experiment was conducted using two hydrogel levels (0.1 and 0.5 wt%) under two water deficit levels (30 and 70 % based on required water irrigation). Germination tests indicated that the developed hydrogel fertilizer has no phytotoxicity and has a positive impact on the germination rate even under water deficit conditions. The application of hydrogel fertilizer at 0.5 wt% significantly (p > 0.05) enhanced plant growth parameters such as leaf number, chlorophyll content, stem diameter, and plant length compared to the control treatment. The magnitude of the responses to the hydrogel fertilizer application depended on the concentration of applied hydrogel fertilizer and stress severity with the most positive effects on the growth and yield of tomato observed at a level of 0.5 %. Tomato yield was significantly enhanced by 19.58 %-12.81 %, 18.58 %-22.02 %, and 39.38 %-43.18 % for the plant amended with hydrogel at 0.1-0.5 wt% and grown under water deficit levels of 0, 30, and 70 %, respectively, compared to the control treatment.

Advancements in Cellulose-Based Superabsorbent Hydrogels: Sustainable Solutions across Industries

The development of superabsorbent hydrogels is experiencing a transformative era across industries. While traditional synthetic hydrogels have found broad utility, their non-biodegradable nature has raised environmental concerns, driving the search for eco-friendlier alternatives. Cellulose-based superabsorbents, derived from sustainable sources, are gaining prominence. Innovations include biodegradable polymer hydrogels, natural cellulose-chitosan variants, and cassava starch-based alternatives. These materials are reshaping agriculture by enhancing soil fertility and water retention, serving as potent hemostatic agents in medicine, contributing to pollution control, and providing eco-friendly construction materials. Cellulose-based hydrogels also offer promise in drug delivery and hygiene products. Advanced characterization techniques aid in optimizing their properties, while the shift towards circular economy practices further highlights sustainability. This manuscript provides a comprehensive overview of these advancements, highlighting their diverse applications and environmental benefits.

Renewable whey-based hydrogel with polysaccharides and polyvinyl alcohol as a soil amendment for sustainable agricultural application

This work describes the preparation of a novel biopolymer hydrogel based on acid whey, cellulose derivatives and polyvinyl alcohol (PVA). The hydrogel was prepared and characterized with the aim of producing an environmentally-friendly soil amendment to increase water retention capacity of the soil. The findings showed considerable swelling properties of the hydrogels depending on the PVA content and crosslinking density. The samples with PVA in a concentration 2.5 % and 5 % were more rigid, the gel fraction increased with a subsequently decrease in their swelling capacity. The hydrogels crosslinked with 15 % of citric acid demonstrated a constant swelling ratio (SR) of around 500 % within 10 swelling/drying cycles. The hydrogels crosslinked with 10 % citric acid and supplemented with 1 % of PVA showed SR of 1000-1400 % caused by less crosslinked polymer network and increased pore volume for water uptake. It was found that hydrogel with a higher gel fraction had a stable structure. Supplementing PVA at 5 % extended the period of decomposition of the hydrogel material by almost 60 % in the soil environment and soil humidity was maintained for longer. Applying 2 % of the hydrogel 5PVA to soil increased the water retention capacity by 19 %.

Renewable Poly(Lactic Acid)Lignocellulose Biocomposites for the Enhancement of the Water Retention Capacity of the Soil

This manuscript details the preparation and characterization of a renewable biocomposite material intended as a soil conditioner based on low-molecular-weight poly(lactic acid) (PLA) and residual biomass (wheat straw and wood sawdust). The swelling properties and biodegradability of the PLA-lignocellulose composite under environmental conditions were evaluated as indicators of its potential for applications in soil. Its mechanical and structural properties were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Results showed that the incorporation of lignocellulose waste material into PLA increased the swelling ratio of the biocomposite by up to 300%. The application of the biocomposite of 2 wt% in soil enhanced its capacity for water retention by 10%. In addition, the cross-linked structure of the material proved to be capable of swelling and deswelling repeatedly, indicating its good reusability. Incorporating lignocellulose waste in the PLA enhanced its stability in the soil environment. After 50 days of the experiment, almost 50% of the sample had degraded in the soil.

Use of whey protein as a natural polymer for the encapsulation of plant biocontrol bacteria: A review

Climate changes, drought, the salinity of water and soil, the emergence of new breeds of pests and pathogens, the industrialization of countries, and environmental contamination are among the factors limiting the production of agricultural products. The use of chemicals (in the form of fertilizers, pesticides and fungicides) to enhance products against biotic and abiotic stresses has limitations. To eliminate the effects of agricultural chemicals, synthetic agrochemicals should be replaced with natural substances and useful microorganisms. To be more effective and efficient, plant biocontrol bacteria need a coating layer around themselves to protect them from adverse conditions. Whey protein, a valuable by-product of the cheese industry, is one of the important natural polymers. Due to its high protein content, safety, and biodegradability, whey can have many applications in agriculture and encapsulation of bacteria to resist pests and plant diseases. This compound is a rich source of amino acids that can activate plant defense systems and defense enzymes. Considering the amazing potentialities of formulation whey protein, this review attends to the efficiency of whey protein as coating layers on fruit and vegetables and in the packaging system to increase the shelf life of agricultural products against phytopathogens.

A New Design of Poly(N-Isopropylacrylamide) Hydrogels Using Biodegradable Poly(Beta-Aminoester) Crosslinkers as Fertilizer Reservoirs for Agricultural Applications

Poly(N-isopropylacrylamide) (P(NIPAAm)) hydrogels were prepared by free-radical polymerization with biodegradable poly (β-amino ester) (PBAE) crosslinkers at 1 wt% and 3 wt% ratio, and compared with conventional N,N'-methylene bisacrylamide (MBA)-crosslinked hydrogel. The influence of the type, molecular weight, and diacrylate/amine ratio of the crosslinker on the crosslink density, compressive strength, and swelling and biodegradation behavior of the hydrogels was investigated. The hydrogels synthesized with lower molecular weight PBAE crosslinkers showed higher crosslinking degrees and compressive strength and lower swelling ratios. To reveal the controlled release behavior of the fertilizer, KNO₃ was used as the model, and its loading and release behavior from these hydrogels was also examined. The N/T5/1 sample with 1.5/1.0 diacrylate/amine molar ratio and 1 wt% PBAE ratio demonstrated the most controlled release of KNO₃ with 66.9% after 18 days in soil. In addition, the hydrogel with the porosity of 71.65% and crosslinking degree of 2.85 × 10^-5 mol cm^-3 showed a swelling ratio of 69.44 g/g, biodegradation rate of 23.9%, and compressive strength of 1.074 MPa. Thus, it can be concluded that the new designed biodegradable P(NIPAAm) hydrogels can be promising materials as nitrate fertilizer reservoirs and also for controlled fertilizer release in soil media for agricultural applications.

Polysaccharide-based biopolymer hydrogels for heavy metal detection and adsorption

BACKGROUND

With rapid development in agriculture and industry, water polluted with heavy metallic ions has come to be a serious problem. Adsorption-based methods are simple, efficient, and broadly used to eliminate heavy metals. Conventional adsorption materials have the problems of secondary environmental contamination. Hydrogels are considered effective adsorbents, and those prepared from biopolymers are biocompatible, biodegradable, non-toxic, safe to handle, and increasingly used to adsorb heavy metal ions.

AIM OF REVIEW

The natural origin and easy degradability of biopolymer hydrogels make them potential for development in environmental remediation. Its water absorption capacity enables it to efficiently adsorb various pollutants in the aqueous environment, and its internal pore channels increase the specific surface area for adsorption, which can provide abundant active binding sites for heavy metal ions through chemical modification.

KEY SCIENTIFIC CONCEPT OF REVIEW

As the most representative of biopolymer hydrogels, polysaccharide-based hydrogels are diverse, physically and chemically stable, and can undergo complex chemical modifications to enhance their performance, thus exhibiting superior ability to remove contaminants. This review summarizes the preparation methods of hydrogels, followed by a discussion of the main categories and applications of polysaccharide-based biopolymer hydrogels.

Hydrogel Application in Urban Farming: Potentials and Limitations—A Review

Urban agriculture plays a vital role in ensuring the self-sufficiency of a great variety of fresh vegetables and nutrients. It promotes a sustainable food system as well as reducing the dependency on imports for the growing population. Urban farming has made it possible for agriculture practices to be implemented anywhere at any time in a sophisticated way. Hydrogel has been introduced in urban agriculture in the past few decades. However, the application of hydrogel in urban agriculture is still being explored in terms of hydrogel types, structure, physical and chemical properties, change due to external factors, and its suitability for different plant species. This review discusses the potentials and limitations of hydrogel in different application conditions. We present the state of knowledge on hydrogel production and crosslinking methods, hydrogel characteristics, water absorption and release mechanisms of hydrogel, hydrogel advantages and limitations, and current and future applications in urban farming.

Biopolymer Hydrogel Based on Acid Whey and Cellulose Derivatives for Enhancement Water Retention Capacity of Soil and Slow Release of Fertilizers

This study describes the development of a renewable and biodegradable biopolymer-based hydrogel for application in agriculture and horticulture as a soil conditioning agent and for release of a nutrient or fertilizer. The novel product is based on a combination of cellulose derivatives (carboxymethylcellulose and hydroxyethylcellulose) cross-linked with citric acid, as tested at various concentrations, with acid whey as a medium for hydrogel synthesis in order to utilize the almost unusable by-product of the dairy industry. The water uptake of the hydrogel was evaluated by swelling tests under variations in pH, temperature and ion concentration. Its swelling capacity, water retention and biodegradability were investigated in soil to simulate real-world conditions, the latter being monitored by the production of carbon dioxide during the biodegradation process by gas chromatography. Changes in the chemical structure and morphology of the hydrogels during biodegradation were assessed using Fourier transform infrared spectroscopy and scanning electron microscopy. The ability of the hydrogel to hold and release fertilizers was studied with urea and KNO₃ as model substances. The results not only demonstrate the potential of the hydrogel to enhance the quality of soil, but also how acid whey can be employed in the development of a soil conditioning agent and nutrient release products.

A Novel Hydrogel Based on Renewable Materials for Agricultural Application

This study details the design and characterization of a new, biodegradable, and renewable whey/cellulose-based hydrogel (i.e., agricultural hydrogel). This was formulated from cellulose derivatives (carboxymethylcellulose (CMC) and hydroxyethylcellulose (HEC)) and acid whey cross-linked with citric acid, with the aim to obtain an agricultural product with a high swelling capacity to uphold the quality of soil and conserve water resources. With regard to the swelling behaviour of the prepared hydrogels, the authors initially assessed the swelling ratio and capacity for water uptake. Evaluating the chemical structure of the hydrogel and its thermal and viscoelastic properties involved performing Fourier transform infrared spectroscopy, differential scanning colorimetry, thermal gravimetric analysis, and rheological measurement of the hydrogel films. According to preliminary results, sufficient swelling capacity and stiffness were observed in a hydrogel prepared with 3% CMC and HEC, cross-linked with 5% citric acid. Moreover, the kinetics of water uptake revealed a promising capacity that was sustainable after 5 drying and swelling cycles. The results confirmed that the stability of the hydrogel was enhanced by the presence of the citric acid. As a consequence, it is necessary to utilize an appropriate cross-linking concentration and abide by certain conditions to ensure the swelling properties of the prepared hydrogel are sufficient. Further investigation of the topic, especially in relation to applications in soil, could confirm if the whey-cellulose-based hydrogel is actually suitable for agricultural use, thereby contributing to the advancement of sustainable arable farming.

Modification of Collagen Derivatives with Water-Soluble Polymers for the Development of Cross-Linked Hydrogels for Controlled Release

Novel cross-linked hydrogels were synthesized as potential materials for the development of smart biofertilizers. For this purpose, hydrogels were prepared using collagen hydrolysate recovered from tannery waste. The water-soluble polymer poly(sodium 4-styrenesulfonate-co-glycidyl methacrylate) (P(SSNa-co-GMAx)) was among others used for the cross-linking reaction that combined hydrophilic nature with epoxide groups. The synthetic procedure was thoroughly investigated in order to ensure high percentage of epoxide groups in combination with water-soluble behavior. The copolymer did not show cytotoxicity against normal lung, skin fibroblasts, or nasal polyps fibroblasts. Through the present work, we also present the ability to control the properties of cross-linked hydrogels by altering copolymer's composition and cross-linking parameters (curing temperature and time). Hydrogels were then studied in terms of water-uptake capacity for a period up to six days. The techniques Proton Nuclear Magnetic Resonance (1H NMR), Thermogravimetric Analysis (TGA), Size Exclusion Chromatography (SEC), and Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR) were applied for the characterization of the synthesized copolymers and the cross-linked hydrogels. Three samples of biofertilizers based on collagen hydrolysate functionalized with P(SSNa-co-GMAx) and starch and having nutrients encapsulated (N, P, K) were prepared and characterized by physical-chemical analysis and Energy Dispersive X-ray analysis-Scanning Electron Microscope (EDAX-SEM) in terms of microstructure. Preliminary tests for application as fertilizers were performed including the release degree of oxidable organic compounds.

Cellulose based materials for controlled release formulations of agrochemicals: A review of modifications and applications

Controlled release formulations (CRFs) of agrochemicals have been attracted considerable attention due to their friendliness to environment. The commercial supporting materials for CRFs of agrochemicals are non-degradable, leading to secondary pollution issue. Cellulose, as the most abundant natural materials in the world, is regarded as one of the most ideal substitutes for non-degradable supporting materials thanks to its good biocompatibility and biodegradability. As raw cellulose materials suffer several problems, such as poor mechanical strength, fast release rate, etc., chemical modifications are commonly performed to improve their properties. In this review, modification methods of cellulose materials for CRFs of agrochemicals were introduced. The relationships between release rate and cellulose based materials were discussed in detail. The applications of cellulose materials for CRFs of agrochemicals were also expounded.

Preparation of transparent anti-pollution cellulose carbamate regenerated cellulose membrane with high separation ability

In this study, cellulose pulp and urea were used to synthesize cellulose carbamate (nitrogen content reaches 4.5%) by low-cost and environmentally friendly solid-liquid phase method. Cellulose carbamate fluid was prepared by using sodium hydroxide aqueous solution as solvent. The fluid was regenerated and formed in a coagulation bath, and finally a regenerated cellulose membrane with high transparency and separation ability was obtained. The simple chemical treatment of cellulose not only greatly increased the mass fraction of cellulose dissolution (It has reached 15%) and retains the original crystal form and thermal stability of cellulose. The surface of the membrane was relatively dense, and the inside has regular microchannel. The factors affect the transparency and water flux of regenerated cellulose membranes were discussed by orthogonal experimental range analysis. The ability of the regenerated cellulose membrane to reject dyes was tested. The results showed that the rejection of methyl blue and congo red reached 100%, and the rejection rate of methyl orange reached 60%. The oil/water separation ability and the anti-pollution ability of the regenerated cellulose membrane were tested. The oil/water separation effect reached 100%. This membrane may have application prospect in water treatment, biotechnology.