Network interpenetrating slow-release nitrogen fertilizer based on carrageenan and urea: A new low-cost water and fertilizer regulation carrier

Advancing agricultural efficiency and sustainability: Bio-inspired superabsorbent hydrogels for slow and controlled release fertilizers

Bio-inspired superabsorbent hydrogels (BiSAHs) represent a versatile polymeric material class that has garnered significant interest due to their multifunctional attributes and extensive range of applications. A thorough examination of the literature and patents on BiSAHs highlights their critical role across diverse sectors. This review provides an in-depth analysis of BiSAHs, focusing on their classification, synthesis methodologies, and potential applications in agriculture. It critically examines biopolymer-based SAHs as soil conditioners and slow and controlled, focusing on their classification, synthesis methodologies, and potential applications in agriculture. It critically examines biopolymer-based SAHs as soil conditioners and slow and controlled-release fertilizers, elucidating the mechanisms governing water retention, swelling capacity, and nutrient release kinetics. The review further presents detailed case studies illustrating the enhancement of crop growth and productivity facilitated by BiSAHs and their effectiveness as agrochemical carriers. Moreover, it explores the role of SAHs in crop protection, particularly in mitigating adverse abiotic stresses such as heavy metal toxicity, salinity, and drought. The ecological, economic, and societal impacts of BiSAH-based controlled-release fertilizers are evaluated, providing a balanced perspective on their sustainability. Ultimately, the review offers insights into future directions and emerging advancements in the development and application of BiSAHs in agricultural settings.

Effect on N release by urea coating with chitosan, starch and urease inhibitor

Food production often relies on nitrogen fertilizers, which can harm the environment when dispersed in agroecosystems. A new urea coating additive, made from chitosan, starch, and N-(n-butyl) thiophosphoric triamide (a urease inhibitor), has been developed to mitigate these effects. The additive was tested for its impact on ammonium (NH4) production and urea release in water, characterized using Fourier transform infrared spectroscopy (FTIR), and subjected to bioassays on lettuce and rocket. The additive decreased the urea release rate in water by 12 %, as predicted by the Korsmeyer and Peppas model, indicating Fickian diffusion controlled by concentration gradients. FTIR analysis revealed that the interaction between chitosan's amine groups and urea's hydroxyl groups slowed the release. In lettuce and rocket, the additive enhanced root development, increasing surface area by 97 %, root volume by 100 %, and thin and thick root growth by 65 % and 131 %, respectively. After 24 h, the fertilizer produced less ammonium when in contact with urease. The production cost of this fertilizer was only 20 % higher than conventional fertilizers, showing that applying NBPT, starch, and chitosan to urea can reduce waste and improve key aspects of sustainable food production.

Evaluation of Sustained Persulfate Oxidant Release for Remediating Trichloroethylene Contaminated Low Permeability Soil in the Phreatic Zone

The back diffusion of trichloroethylene (TCE) between low permeability zones (LPZ) and transmissive zones in the subsurface presents remediation challenges. This study investigates in situ chemical oxidation (ISCO) using a sodium persulfate sustained release rod (SPS SR-rod) for potential TCE remediation in the LPZ within a two-dimensional sand tank. The tank simulates a dual permeability porous medium with hydraulic gradients of 0.01 and 0.05. The SPS SR-rod placed within the LPZ released an average PS concentration of ∼625 mg/L laterally, with initial peak concentrations of 7000-10,000 mg/L. When the rod was placed atop the LPZ, lower PS concentrations were observed compared to placement within the LPZ. A separate evaluation of both SPS SR-rod placements in a 2D sand tank injected with pure TCE tested the oxidant's ability to address soil-sorbed TCE. The rod atop the LPZ can mitigate dual permeability layers and creates a depletion zone at the high permeability zone to reduce contaminant transport from the LPZ. The rod within the LPZ reduces TCE lateral dispersion. The persistence and slow release of SPS in the LPZ suggest that the SPS SR-rod could effectively extend the time period of ISCO remediation of low-concentration TCE in the LPZ and the surrounding environment.

Superabsorbent Polymers: Innovations in Ecology, Environmental, and Diverse Applications

Significant progress has been achieved in the development of superabsorbent polymers (SAPs), focusing on enhancing their performance and expanding their applications. Efforts are particularly directed at increasing water absorbency while promoting environmental sustainability. Biodegradable materials such as starch and potassium humate have been successfully integrated with SAPs for desert greening, improving water retention, salt resistance, and seedling survival. The inclusion of nutrient-rich organic-inorganic composites further enhances the durability, efficiency, and recyclability of SAPs. In drought mitigation, polymeric absorbent resins such as polyacrylamide and starch-grafted acrylates have shown efficacy in ameliorating soil conditions and fostering plant growth. In arid environments, agents enriched with humic acid and bentonite contribute to improved soil aeration and water retention, creating optimal conditions for plant establishment. Additionally, the adoption of innovative waste management solutions has led to the production of amphiphilic SAPs from residual sludge, effectively addressing soil nutrient deficiencies and environmental pollution. In the food industry, SAPs containing protease, tea polyphenols, and chitosan exhibit potential for enhancing the stability and quality of seafood products. These advancements highlight the growing relevance of structural optimization approaches in SAP development across diverse applications and underline the importance of continued innovation in these fields. As novel materials emerge and environmental challenges intensify, the potential applications of SAPs are anticipated to expand significantly.

Environmentally friendly membrane based on chitosan, citric acid, and calcium for slow-release fertilizer

In agriculture, fertilizers are important for plant growth. Among them, conventional fertilizers, particularly urea fertilizers, are popular owing to their low cost and high nitrogen content. However, their use often leads to uneven nitrogen absorption and environmental pollution. Slow-release fertilizers (SRFs), particularly those based on chitosan, offer a solution. This research aims to produce biodegradable chitosan/citric acid/calcium-urea (CS/St/Ca-urea) films to increase the absorption efficiency and use of artificial nitrogen fertilizers (especially urea). Herein, chitosan/citric acid/calcium (CS/St/Ca) films were synthesized and applied as SRFs. Chitosan was dissolved in 1 % acetic acid and added to citric acid at 55 °C for 24 h. Then, calcium oxide (CaO) and urea were added to the CS/St mixture and stirred until homogeneous. Subsequently, the membrane product was characterized by ATR-IR, SEM-EDX, and elemental analysis and its nitrogen solubility was determined using a UV-vis spectrophotometer. The physical properties of the CS/St/Ca were investigated via swelling, hydrophobicity, and tensile strength tests. Results showed that a CS/St at weight ratio of 1:1 can increase the tensile strength by up to 13.6 %. The addition of a filler with a Ca additive, as well as the addition of CaO, can increase the mechanical strength of the membrane. The CS/St/Ca film membranes can function optimally as a urea SRF coating material with a release rate of 3.37-9.46 ppm day-1. The applied kinetic model follows the Higuchi kinetic model, with an R 2 value of 0.9505.

Design and preparation of reticular superabsorbent hydrogel material with nutrient slow-release and high shear strength for ecological remediation of abandoned mines with steep slopes

In order to solve ecological remediation issues for abandoned mines with steep slopes, a kind of hydrogels with high cohesion and water-retaining were designed by inorganic mineral skeleton combining with polymeric organic network cavities. This eco-friendly hydrogel (MFA/HA-g-p(AA-co-AM)) was prepared with acrylic acid (AA)-acrylamide (AM) as network, which was grafted with humic acids (HA) as network binding point reinforcement skeleton and polar functional group donors, KOH-modified fly ash (MFA) as internal supporter. The maximum water absorption capacities were 1960 g/g for distilled water, which followed the pseudo-second-order model. This super water absorption was attributed to the first stage of 62 % fast absorption due to the high specific surface area, pore volume and low osmotic pressure, moreover, the multiple hydrophilic functional groups and network structure swell contributed to 36 % of the second stage slow adsorption. In addition, the pore filling of water in mesoporous channels contributed the additional 2 % water retention on the third stage. The high saline-alkali resistance correlated with the electrostatic attraction with MFA and multiple interactions with oxygen-containing functional groups in organic components. MFA and HA also enhanced the shear strength and fertility retention properties. After 5 cycles of natural dehydration and reabsorption process, these excellent characteristics of reusability and water absorption capacity kept above 97 %. The application of 0.6 wt% MFA/HA-g-p(AA-co-AM) at 15° slope could improve the growth of ryegrass by approximately 45 %. This study provides an efficient and economic superabsorbent material for ecological restoration of abandoned mines with steep slopes.

Design and manufacture of new hybrid hydrogel and superabsorbent polymer for controlled release of fulvic acid based on grafted xanthan gum/gelatin using electron irradiation and its use in fodder corn cultivation

A humic acid-gelatin (HA-Gel) hydrogel, a gallic acid-xanthan gum (GA-XG) hydrogel, a HA-Gel/GA-XG hydrogel, and superabsorbent polymer (SAP) of HA-Gel/GA-XG/polyacrylamide (PAM) hydrogel were synthesized using electron beam irradiation method. The capability of synthesized hydrogels in loading and controlled release of fulvic acid (FA) was studied. The chemical and physical structure of sorbents was confirmed by various analyses. The effect of irradiation dose on mechanical properties, gel percentage, swelling, and absorbency under load (AUL) of the sorbents was investigated. By changing the hydrogel structures into the SAP form, its swelling capacity was increased from 37 to 320 g/g. Both hybrid hydrogel and SAP were reusable for up to 7 cycles. The maximum fertilizer loading capacities for SAP and hybrid hydrogel were 402.1 and, 175.5 mg g-1, respectively. In comparison to hydrogels, the SAP showed a slower FA-release performance. Thus, in soil media, 86 % of FA was released in 15-20 days from the hybrid hydrogel while with the SAP, 81 % of FA was released in 30-35 days. The significant improvement in the growth of fodder corn treated with FA-loaded SAP in the greenhouse media in comparison to the control groups showed the effective performance of the designed SAP, favoring its practical applications.

Research Advances in Superabsorbent Polymers

Superabsorbent polymers are new functional polymeric materials that can absorb and retain liquids thousands of times their masses. This paper reviews the synthesis and modification methods of different superabsorbent polymers, summarizes the processing methods for different forms of superabsorbent polymers, and organizes the applications and research progress of superabsorbent polymers in industrial, agricultural, and biomedical industries. Synthetic polymers like polyacrylic acid, polyacrylamide, polyacrylonitrile, and polyvinyl alcohol exhibit superior water absorption properties compared to natural polymers such as cellulose, chitosan, and starch, but they also do not degrade easily. Consequently, it is often necessary to modify synthetic polymers or graft superabsorbent functional groups onto natural polymers, and then crosslink them to balance the properties of material. Compared to the widely used superabsorbent nanoparticles, research on superabsorbent fibers and gels is on the rise, and they are particularly notable in biomedical fields like drug delivery, wound dressing, and tissue engineering.