Article

Synthesis of a slow‐release and superabsorbent nitrogen fertilizer and its properties

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Abstract

A slow-release and superabsorbent nitrogen fertilizer (SSNF) was synthesized by aqueous solution copolymerization of acrylic acid and maleic anhydride using N,N′-methylene bisacrylamide as a crosslinker, ammonium persulfate and sodium sulfite as an initiator in the presence of urea. The effects on water absorbency such as amount of crosslinker, initiator, urea and maleic acid, degree of neutralization, etc. were investigated. To improve slow release and water retention properties, the product was surface-crosslinked with trihydroxymethyl propane glycidol ether (6360). The nitrogen content of the SSNF synthesized under optimal conditions was 28.5%, and the water absorbencies were about 900 (g/g) in distilled water and 180 (g/g) in tap water. The nitrogen slow release behavior of the SSNF in water and water retention capacity of the soil with SSNF were also investigated. The results showed that the surface-crosslinked product not only had good slow release property but also excellent soil moisture preservation capacity, which could effectively improve the utilization of fertilizer and water resources simultaneously. The results of the present work indicated that the SSNF could be found an application in agriculture and horticulture, especially in drought-prone areas where the availability of water is insufficient. Copyright © 2006 John Wiley & Sons, Ltd.

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... The binding agent helps form a compact composite structure and water absorption. 74,86 The water absorption properties are closely related to the diffusion mechanism or the release of the environmental fertilizer. Water absorption can increase along with the increase in crosslinking content from 0.065% to 0.093% in the synthesis of sustained-release N fertilizer and superabsorbent (SSNF) using MBA bisacrylamide as a crosslinker and trihydroxymethyl propane glycidol ether (6360) as surface crosslinker (see the mechanism in Fig. 7). ...
... Water absorption can increase along with the increase in crosslinking content from 0.065% to 0.093% in the synthesis of sustained-release N fertilizer and superabsorbent (SSNF) using MBA bisacrylamide as a crosslinker and trihydroxymethyl propane glycidol ether (6360) as surface crosslinker (see the mechanism in Fig. 7). 86 As a result, the surface crosslinked product can provide slowrelease properties to maintain excellent soil moisture. If the crosslinking agent increases, the superabsorbent crosslink density also increases, decreasing the space between the polymer chains and water absorption. ...
... If the crosslinking agent increases, the superabsorbent crosslink density also increases, decreasing the space between the polymer chains and water absorption. 86 The same thing was also reported by Guo et al. 74 that over-crosslinking the polymer gel network can inhibit polymer chain stretching in the gel network, thereby reducing the water absorption value in the urea-formaldehyde SRF development with superabsorbent and moisture preservation (USFSMP). Over crosslinking the polymer gel network can inhibit polymer chain stretching in the gel network, thereby reducing the water absorption value. ...
Article
The increase in global population puts pressure on food supplies in the agricultural sector, whose productivity depends on the soil nutrient availability. This demand has an impact on the high chemical fertilizer consumption. Simultaneously, another problem arises owing to unsustainable agricultural practices, namely low fertilizer efficiency. Controlled/slow-release (CRF/SRF) fertilizers using cellulose biopolymers as composite matrices are a sustainable prospect owing to their being abundant, renewable, and biodegradable. Furthermore, cellulose contains surface chemical properties that are easily modified to play a role in the fertilizers’ release. In addition, the high cellulose hydrophilicity helps maintain soil moisture for plant growth. This article reviews the prospects of cellulose and its derivatives for CRF/SRF development, including cellulose modification, slow/controlled-release mechanisms, and their impact on sustainable agricultural practices, which are discussed based on environmental, economic and social aspects. In addition, selecting environmentally friendly and low-cost technologies is a concern to support sustainability.
... Due to the outstanding properties of superabsorbent materials over traditional waterabsorbing materials such as cotton, pulp, sponge, etc., they are widely used in agriculture, horticulture, health, hygiene products, controlled drug delivery systems, oil and gas exploitation, and coal dehydration having attracted considerable interests and researches [2,6,7]. However, the applications of superabsorbent polymers in agricultural and horticultural areas have been most prominent, especially for the effective usage of water in drought-prone areas and desert regions [8,9]. ...
... Urea is the most widely used nitrogen fertilizer because of some advantages such as its high nitrogen content (46%) and comparatively low cost of production [8,25,26]. Urea shows high hydrophilic properties due to its amide structure. The unique structure of urea makes it a good candidate for application in water-retaining material. ...
... As seen, this reduction was negligible at urea:AA ratio of 10:10. This phenomenon can be attributed to the excessive urea which cannot be connected by AA and would be encapsulated in the polymer making the overloose networks of hydrogels resulting in lower crosslink density [1,8,15,25]. Fig. 5 shows the water absorption of the samples in three levels of urea: acrylic acid ratios (0:10, 5:10, 10:10) for acrylic in comparison with AA-CNFs hybrid hydrogels in distilled water. ...
Article
In this study, acrylic acid (AA) and cellulose nanofibers (CNFs) were used as main materials to synthesize an acrylic-nanocellulose hybrid hydrogel nanocomposite in the presence of urea. The interpenetrating polymer networks were obtained by radical polymerization in different urea: AA ratios (0:10, 1:10, 3:10, 5:10, 10:10). Fourier transform infrared spectroscopy (FTIR) combined with X-ray diffraction (XRD) and elemental analysis techniques confirmed the chemical interaction of urea in the network structure. Free absorption and water absorption under load (AUL) of the synthesized hydrogels varying in urea: acrylic acid weight ratios were measured in distilled and saline (0.9 wt%) solution for hybrid (5 wt% CNFs) and pure polyacrylic acid (0 wt% CNFs) hydrogels. It was found that incorporation of urea and CNFs in the hybrid structure generating compact hydrogel networks with high crosslink density leading to lower absorption with and without pressure, whereas, incorporation of urea in the structure resulted in a more extended network with higher absorption capacity (about 3×) than hybrid structure.
... The minimization of acrylic acid dimer (DAA) in the monomer is important due to its indirect adverse effects on the final product. As soon as AA is produced, diacrylic acid (β-acryloxypropionic acid) is formed spontaneously in the bulk of AA via a sluggish Michael-addition reaction as shown in Fig.1 Major disadvantage about these synthetic polymers is poor in degradability, and then there remains an environmental problem with superabsorbent polymers [33]. ...
... A typical AUL tester picture and various parts [33]. ...
... Fig.1.8)shows two ways to prepare acrylic SAP networks, i.e., simultaneous polymerization and crosslinking by a polyvinylic crosslinker, and cross-linking of a water-soluble prepolymer by a polyfunctional cross-linker[33]. ...
Thesis
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New Sucrose – based monomers were prepared. The prepared monomers are Allyl Sucrose (AS) and Epoxy Ally Sucrose (EAS). Allyl sucrose was prepared by reacting sugar with allyl chloride in an alkaline medium. Allyl sucrose was then converted into epoxy allyl sucrose by epoxidation with m-chloroperoxybenzoic acid (m-CPBA). The prepared sucrose-based monomers were characterized by 1H and 13C NMR spectroscopy. Both sucrose-based monomers were then used as cross-linking agents to prepare an entirely new class of special biodegradable superabsorbent polymers. In addition, other cross-linking agent were also used including 1,4-butanediol diglycidyl ether (1,4-BDGE), and ethylene glycol diacrylate (EGDA). Ethylene glycol diacrylate was chosen because it is a well known cross-linking agent that is reported in the literature as a cross-linking agent for superabsorbent polymers. 1,4-Butanediol diglycidyl ether was used for the first time as cross-linking agent for superabsorbent polymer. The absorbency for the prepared SAP’s were evaluated. Free swell for the prepared polymers was measured using the tea bag test, and the absorbency under load was measured using the hanging cell test method. Results showed that the free swells and absorbency under load decrease by increasing percentage of cross-linking agent, lowest absorbency observed at cross-linking about 4%. SAP cross-linked with EAS has the highest absorbent capacity and absorbency under load. This could be because it has the highest polarity and highest number of hydroxyl groups. The advantages of the prepared polymers over the commercial one are that: first; they are biodegradable as shown by the biodegradability test; second, they are prepared in one step process. Since the commercial SAP is prepared in a two-step process, in the first step the acrylic acid is polymerized with the cross-linking agent then the produced SAP is surface cross-linked to enhance it absorbency under load.
... 2-5% Fixation in soils Table a Raising the rate of fertilizer utilization and reducing the contamination caused by illogical fertilization were the key steps for the sustainable development of agriculture. However, the progressional aims of the fertilizer were slow/controlled release, precision, and eco-environmental health in the world [7]. There has been an interest in the use of nanotechnology in agriculture for nearly 15 ...
... Application of nano composites proved to improve the fertilizer use efficiency as a result of physical and chemical properties adsorption and combination between nutrient elements and also due to higher reactivity. Nanocomposties act as a multifunctional fertilizer [7]. ...
Article
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Global population is rapidly increasing and is predicted to reach 9.6 billion by 2050 and the limited resources tend to push the sector forward demanding the development of a highly efficient agriculture thus allowing reduction of worldwide poverty and hunger [1]. To meet the food demands of this growing population the agriculture sector is being pressurized to assure food security. Hence chemical fertilizers are being considered as an inevitable source of plant nutrition for improving the crop production. This lead to a notion in farmers that using higher quantities of chemical fertilizers gains higher crop yields. However, only less than half of the amount of applied fertilizers will be utilized by the crop whereas the remaining amount of fertilizer which is intended to be taken up by plant may get lost through leaching, become fixed in soil or contribute to water pollution which is even worse. According to recent statistical reports it has been observed that the key macronutrient elements Nitrogen, Phosphorous and Potassium applied to the soil are lost at a rate of 40-70%, 80-90% and 50-90%, respectively, thus causing a considerable loss of applied resources [2]. Additionally, farmers tend to apply fertilizers repeatedly in order to achieve yields at desired levels, this overdose of chemicals counter acts and lead to decreased soil fertility and increased salt concentrations thereby causing future crop losses. Furthermore, irregular use of fertilizers without control on nutrient release patterns causes deterioration of product quality. Therefore, developing slow or controlled release fertilizers plays a crucial role not only in enhancing the crop production, productivity and quality, but also helps towards upgradation of sustainability in agricultural production. Given the unique properties of nano-materilas such as high surface-to-volume ratio, controlled-release kinetics of nutrients to the targeted sites and sorption capacity, nanotechnology has a high importance for designing and using of new fertilizers. Nanofertilizers are nutrients encapsulated/coated with different types of nanomaterials for the control and slow delivery of one or more nutrients in order to satisfy the imperative nutrient requirements of plants [3]. These "smart fertilizers" are now being regarded as a promising alternative, to an extent that they are to be considered as preferred form of fertilizers over the conventional ones in several cases.
... 2-5% Fixation in soils Table a Raising the rate of fertilizer utilization and reducing the contamination caused by illogical fertilization were the key steps for the sustainable development of agriculture. However, the progressional aims of the fertilizer were slow/controlled release, precision, and eco-environmental health in the world [7]. There has been an interest in the use of nanotechnology in agriculture for nearly 15 ...
... Application of nano composites proved to improve the fertilizer use efficiency as a result of physical and chemical properties adsorption and combination between nutrient elements and also due to higher reactivity. Nanocomposties act as a multifunctional fertilizer [7]. ...
... Fertilizer treatment increased green and blackgram yields by 13% and 38% over the control. [13], revealed that adding organic layer to the clay could regulate release of nutrients. Nanotechnology would be used to release nutrients from membranes. ...
... Nanofertilizer technology can increase crop productivity. There is an increasing interest in the integration of nanoporous zeolites in agricultural inputs over the years as a result of society's growing concern for the harmful effects of chemical fertilizers on the agro-ecosystem [13,15]. Nanofertilizer may be a strategy to enhance crop yields and productivity in nutrient usage [10]. ...
Article
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Nano fertilizers are essential resources in agriculture in order to increase crop production, quality, productivity, and boost nutrient uptake. Nano-fertilizer is efficient for specific use of nutrients at appropriate time of plant growth and can provide nutrients as a whole with the crop. Growing crops with heavier fertilizer concentrations further increases may be limiting to crop growth due to nutrient toxicity. Nano-fertilizers provide more area for photosynthesis, leading to more sunlight absorption and greater yields of the crop. It will help plants survive challenging environmental factors such as drought. Limitations in agricultural land and water supplies can improve production land and water use productivity through the use of new technologies. Nanotechnology has the potential of transforming both personal use and development. Nanostructured formulations may also be developed in order to deliver active ingredients in response to environmental cues and biological demands more properly. The principle of fertilizer use is known to use less resource and to be free from chemical side effects. Nanotechnology has enormous potential to contribute significantly to sustainable agricultural production, particularly in developing countries.
... One technique to effectively decrease the nutrient components losses and environmental pollution is utilizing slow-release fertilizers [3,5] which can be categorized in three groups including (1) slightly soluble materials, such as urea-formaldehyde; (2) materials for deep placement, such as urea super granules; as well as (3) coated fertilizers [6]. Although controlled released fertilizers are mostly made of polymers [3][4][5][6][7][8], eco-friendly polymer controlled-release fertilizer has been reported [9]. ...
... One technique to effectively decrease the nutrient components losses and environmental pollution is utilizing slow-release fertilizers [3,5] which can be categorized in three groups including (1) slightly soluble materials, such as urea-formaldehyde; (2) materials for deep placement, such as urea super granules; as well as (3) coated fertilizers [6]. Although controlled released fertilizers are mostly made of polymers [3][4][5][6][7][8], eco-friendly polymer controlled-release fertilizer has been reported [9]. In polymer-coated fertilizers, the solubility of nitrogen is temperature-dependent which limits their application [10]. ...
Article
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Overusing nitrogen fertilizer causes some serious problems for water resources, soil, and agriculture products. Researchers have been trying to develop effective means which may use less amount of fertilizers containing nitrogen. In this work, cost-effective ceramic granule adsorbent was prepared to be used as a fertilizer carrier of controlled release behavior. A mixture of 70 wt.% domestic kaolin and 30 wt.% gibbsite was used to produce the granules. By utilizing thermal analysis of raw granule, the calcination temperatures were obtained and the effect of various calcination temperatures of 500, 600, and 700˚C on the water adsorption was studied. The characteristics of granules were investigated by XRD, BET, FTIR, and SEM analyses. The results showed that by increasing the calcination temperature, the crystal structure of the granules was transformed into a dehydrated form and by calcination at 600°C the specific surface area of granules increased from 7.50 to 53.45m2/g. The granules were soaked in a 500g/lit solution of urea, where they adsorbed about 10wt.% urea. The dried urea-loaded granules were placed in water where the release of urea was measured by UV-vis spectrophotometry. Finally, different portions of urea-loaded granules were evaluated as fertilizer in the growing bed of corn plant where the height and the stem diameter of samples were compared with a control sample as well as a sample fertilized by urea directly. The results showed that by using the loaded granules, the urea consumption can be reduced by 50%.
... These include their small sizes (1-100 nm), larger surface to volume ratio, alteration in the physiochemical properties with reference to their shapes and sizes, chemically adjustable physical properties, strong relation towards the target proteins. These characters cause the enhancement in the aggregation of particles which was dependent on surface modification types, structural strength, enhanced photoemission, high heat and electric conductivity as well as improved surface catalytic activity (Garg et al. 2008;Liu 2006;Rosi and Mirkin 2005;McNeil 2005) (Fig. 7.6). ...
... The study substantiated that the products having cross linkages are excellent slow releasers of nutrients and have a high-water retention capacity which in turn enhances the water and fertilizer use efficiency by the crop. In arid regions SSNF have remarkable application in agricultural practices (Liu et al. 2006). ...
Chapter
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Plant infection is a major alarming situation in sustainable crop production affecting 20–30% of the total annual loss (Nezhad 2014). Nutritional sustainability has declared as one of the most crucial concerns of human race. Nation-states, societies and administrations have been fraught with this problem from a long time ago. The imminent appearances even miserable with food deficiency matter approaching hefty. Plant infections also lead towards economic loss by communal attack of plant pathogens on other cash crops than food cash crops resulting in loss in achievable yield (Pan et al. 2010; Thind 2012). World population is increasing day by day therefore the main task exactly is how to fulfill the requirement of growing population with limited resources (less input expense, limited land) and to reduce the dangers to the environment. Main task, sometimes, appears to be disease management.
... These include their small sizes (1-100 nm), larger surface to volume ratio, alteration in the physiochemical properties with reference to their shapes and sizes, chemically adjustable physical properties, strong relation towards the target proteins. These characters cause the enhancement in the aggregation of particles which was dependent on surface modification types, structural strength, enhanced photoemission, high heat and electric conductivity as well as improved surface catalytic activity (Garg et al. 2008;Liu 2006;Rosi and Mirkin 2005;McNeil 2005) (Fig. 7.6). ...
... The study substantiated that the products having cross linkages are excellent slow releasers of nutrients and have a high-water retention capacity which in turn enhances the water and fertilizer use efficiency by the crop. In arid regions SSNF have remarkable application in agricultural practices (Liu et al. 2006). ...
Chapter
The world population has increased tremendously within last few decades and there is a great challenge of food security worldwide. The challenge of providing adequate food supply becomes more significant when we observe a reduction in crop yield annually. Plant pests, pathogens and various environmental factors contribute towards low crop productivity. Rapidly changing climatic conditions further add in epidemics of new pathogens. Classical breeding programs have significantly helped us in management of a sustainable food supply but with exponentially increasing population pressure together with high insurgence of pathogens/pests, we require multiple tasking to achieve better results. Modern techniques like plant tissue culture, transformation, RNAi, nanotechnology combined with classical techniques may rescue us from food shortage and help in achieving adequate supply of quality food in future.
... Amendment of SAP's in soil can yield results such as; (i) decreases bulk density, (ii) escalation in soil aggregation, porosity, aeration and water retention capacity [10,11,12,13,14], (iii) decreases hydraulic conductivity (saturated) of soil and drainage [15,16] and (iv) reduces pant sensitivity for salinity and work as a source of cautious release of nutrients, [9,17,18,19]. The analysis showed that, the use of SAP increases soil water content at field capacity and at permanent wilting point, which may lead to a significant increase in available water content in various soils textures used under numerous crops' management [20,21,22,23]. ...
... The concentration of soil potassium and soil sodium present in each soil pit was determined using flame photometer. The samples were collected at pre specified depths and they were analyzed accordingly [18]. ...
Article
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This research aimed to evaluate the effect of different forms of Super Absorbent Polymers (SAP) on soil physical and chemical properties under orchard field condition. Total area under the experiment was divided into twelve plant pits of size 0.46 m × 0.46 m having the depth of 0.60 m, with three replications and four treatments. The treatments were Control, Polymer Water pad, super absorbent polymers (SAP) in Powder form and super absorbent polymers (SAP) in Crystal form. The size of plant pit was set according to the size of polymer water pad. A plastic polythene sheet at a depth of 0.6 meters was given from all the four sides of pits, to prevent the seepage. Water absorbent polymers in powder as well as in crystal forms were mixed with the soil of pit at the rate of 3g/kg of soil. Lemon plants of one year old were transplanted in pits. The samples of soil were taken for physical and chemical properties, before and after applying the treatments. The results reveal that soil bulk density under SAP (Powder) and SAP (Crystal) treatment was reduced thereby soil porosity increased under both treatments while it was unchanged under control and water pad treatments. The field capacity of soil under both treatments was increased as compared to control and water pad treatment. The pH of soil under all treatments was decreased. EC of soil under water pad and SAP (Powder) was increased while there was a minimum increase in EC of soil under Control and SAP (Crystal) treatment. Under water pad and SAP (Powder) treatments, cations (K & Na) and minerals (Ca + Mg) were accumulated. The SAR and ESP of soil under all SAP treatments were increased as compared with control.
... Some of the advantages of SAPs for producing SRFs include improving soil through aeration, mitigating soil degradation, reducing water evaporation losses, controlling environmental pollution, reducing plant mortality, and extending nutrient retention in soil. SPAs can be prepared from hydrophilic polymers in which the polymer chains cross-linked by physical entanglement and chemical grafting form a three-dimensional structure that allows them to absorb and retain a large amount of water even under external pressure (Guo et al., 2005;Liang and Liu, 2006a;Liang et al., 2009;Liu et al., 2006Liu et al., , 2007Ni et al., 2009;Ni et al., 2011;Qiao et al., 2014;Tao et al., 2011;Wang et al., 2012;Xie et al., 2011;Xu et al., 2007). SAPs can be divided into natural, synthetic, and synthetic-natural polymers, depending on their material resources. ...
Article
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The development of slow-release fertilizers (SRFs) has attracted increasing attention, especially in the last two decades since the well-recognized environmental problem caused by overusing fertilizers. Different kinds of SRFs have been developed, including chemical or physical reactions, loading into the holders with porous and layer structures, coating, and holding by hydrogels, etc. Various techniques have been reviewed at different development stages and from different angles. Meanwhile, various methodologies have been developed and used to evaluate the release performances of different kinds of SRFs. However, the reported results are significantly different from the different evaluation methodologies. In this work, we have firstly briefly reviewed the development of SRFs according to the fabrication classification: (1) chemical synthesizing, (2) loading, (3) coating, (4) application of biodegradable polymers, and 5) hydrogel-based systems, then focused on reviewing different evaluation methodologies and their mechanisms. Various models used to describe and predicate release behaviors were also discussed. Generally, there are four kinds of evaluation methodologies: (1) immersing in water, (2) leaching by soil, (3) planting in greenhouse, and (4) yield comparison. It was found that most of the traditional synthesized products and coated fertilizers by conventional polymers are reasonably stable in water, so the method of immersing in water is suitable. Still, most of the water-sensitive coating or mixture-based products need to be evaluated through leaching by soil. Both greenhouse and yield comparison are simple and reliable methods and has been widely used for final evaluation and confirmation, but the weakness of time issue and unpredictable weather conditions limit their application during the initial developing step. It was found that there is no direct relationship between different methodologies since their releasing mechanisms are different even though the releasing trend is similar. Various evaluation methodologies need to be modified according to different products and adjusted according to laboratory capability (measurement techniques). The methods of element detection and environmental issues were also discussed. Various models used to describe and predicate releasing behaviors were reviewed in this paper. This paper also summarized the standards of SRFs from different countries. It was pointed out that the nutrient delivery to plants by actual controlled-release fertilizers should closely match the growing demand of the plants. A sustained supply of nutrients for the entire crop growth in a single dose (fertilizing) can save labor and handling costs. Furthermore, it is understandable that different plants grow favorably in different soil and conditions, so the fertilizers should also be evaluated in different environments and situations. The evaluation method should closely match plant growth requirements, such as rice in the water while corn is in solid soil.
... According to reports, the nanostructure of nanofertilizers possesses a high surface-area-to-volume ratio, allowing plants to absorb nutrients gradually and sustainably as required [121][122][123]. Furthermore, nanofertilizers offer several advantages, including increased soil fertility, reduced nutrient loss, increased crop output, and reduced environmental contamination, and provide a viable habitat for microorganisms [124]. Many researchers have synthesized slow-release fertilizers by combining hydroxyapatite (HA) with urea to improve nutrient delivery to plants [50,125]. ...
Article
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Nutrient management is always a great concern for better crop production. The optimized use of nutrients plays a key role in sustainable crop production, which is a major global challenge as it depends mainly on synthetic fertilizers. A novel fertilizer approach is required that can boost agricultural system production while being more ecologically friendly than synthetic fertilizers. As nanotechnology has left no field untouched, including agriculture, by its scientific innovations. The use of nanofertilizers in agriculture is in the early stage of development, but they appear to have significant potential in different ways, such as increased nutrient-use efficiency, the slow release of nutrients to prevent nutrient loss, targeted delivery, improved abiotic stress tolerance, etc. This review summarizes the current knowledge on various developments in the design and formulation of nanoparticles used as nanofertilizers, their types, their mode of application, and their potential impacts on agricultural crops. The main emphasis is given on the potential benefits of nanofertilizers, and we highlight the current limitations and future challenges related to the wide-scale application before field applications. In particular, the unprecedent release of these nanomaterials into the environment may jeopardize human health and the ecosystem. As the green revolution has occurred, the production of food grains has increased at the cost of the disproportionate use of synthetic fertilizers and pesticides, which have severely damaged our ecosystem. We need to make sure that the use of these nanofertilizers reduces environmental damage, rather than increasing it. Therefore, future studies should also check the environmental risks associated with these nanofertilizers, if there are any; moreover, it should focus on green manufactured and biosynthesized nanofertilizers, as well as their safety, bioavailability, and toxicity issues, to safeguard their application for sustainable agriculture environments.
... The analyzed gel used here contains 4 substances: H2O, hydroxyethyl cellulose, sodium citrate and the phenalene-1-one based photosensitizer. Hydroxyethyl cellulose is well known and frequently used in cosmetics (115), pharmaceutical industry (116), and other industrial applications (117)(118)(119)(120). ...
Preprint
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The antibiotic crisis increasingly threatens the health systems world-wide. Especially as there is an innovation gap in the development of novel antibiotics, treatment options for bacterial infections become fewer. The photodynamic inactivation (PDI) of bacteria appears to be a potent, new technology that may support the treatment of colonized or infected skin. In photodynamic inactivation, a dye - called photosensitizer - absorbs light and generates reactive singlet oxygen. This singlet oxygen is then capable of killing bacteria independent of species or strain and their antibiotic resistance profile. In order to provide a practical application for the skin surface, the photosensitizer was included in an aqueous hydrogel (photodynamically active hydrogel). The efficacy of this gel was initially tested on an inanimate surface and then on the human skin ex vivo. NBTC staining and TUNEL assays were carried out on skin biopsies to investigate potential harmful effects of the surface PDI to the underlying skin cells. The photosensitizer in the gel sufficiently produced singlet oxygen while showing only little photobleaching. On inanimate surfaces as well as on the human skin, the number of viable bacteria was reduced by over or nearly up to 4 log10 steps, equal to 99.99% reduction or even more. Furthermore, histological staining showed no harmful effects of the gel towards the tissue. The application of this hydrogel represents a valuable method in decolonizing human skin including the potential to act against superficial skin infections. The presented results are promising and should lead to further investigation in a clinical study to check the effectivity of the photodynamically active hydrogel on patients.
... SAPs can take up as much water as a thousand times of their own weight while general hydrogels can only take up no more than 10 times their own weight. They have become increasingly important nowadays and are widely used in many fields including hygiene and bio-related areas [9-17] , agriculture [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] , construction [38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55] and so forth [56][57][58][59][60][61][62][63] . Disposable health care products (DHCPs), such as baby diapers, female sanitary and adult incontinence products are the biggest application area of SAPs, taking more than 95% market share ( Fig. 1 ) [ 56 , 64 ]. ...
Article
Superabsorbent polymers (SAPs) play important roles in our daily life, as they are applied in products for hygiene, agriculture, construction, etc. The most successful commercially used types of SAPs are acrylate-based, which include poly(acrylic acid)s, poly(acrylamide)s, poly(acrylonitrile)s and their salts. The acrylate-based SAPs have superior water-absorbent properties, but they have high molecular weight and in addition an entirely carbon atom-based and cross-linked backbone. These factors endow them with poor (bio)degradability, which has a devastating impact on the environment where such SAP-containing materials may end up at the end of their lifetime. Furthermore, the raw materials for production of acrylate-based SAPs are mostly petroleum-based. From the viewpoint of sustainability, a bio-based resource would be the ideal candidate to replace the fossil-based ones. To overcome the shortcomings of the existing SAPs, bio-based and degradable SAPs are required. This review will then cover the following topics: (1) the technology development history and state-of-the-art of current SAPs; (2) the product designing principles of SAPs; (3) an in-depth introduction and discussion of the structural characteristics and properties of different kinds of SAPs derived from both fossil or renewable resources and (4) novel polycondensate-based, potentially biodegradable SAPs with promising industrial applicability.
... Nitrogen, which promotes the formation of leaves and stems in plants, is a nutrient that directly affects important physiological functions, product amount and product quality [1][2][3]. Since the amount of nitrogen in the soil is not sufficient for plants to grow healthily and to provide high quality and high yields, the nitrogen needed by plants should be added to the soil with nitrogen fertilizers [4,5]. However, since nitrogenous fertilizers are very mobile fertilizers in the soil, they may be lost by washing with excessive rainfall and irrigation water or in gaseous form [6]. Also, these nitrogen losses are one of the major problems that cause water and air pollution [7][8][9][10]. ...
Article
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To reduce water pollution caused by fertilizers in agricultural irrigation, highly swelling crosslinked hydrogels (p(DMAAm-co-MA) or DM1) based on N,N-dimethylacrylamide (DMAAm) and maleic acid (MA) were prepared using a chemical initiator with the redox polymerization technique. Negative and positive surface modifications of DM1 were achieved using hydrochloric acid (HCl) (p(DMAAm-co-MA)/HCl or DM2) and sodium hydroxide (NaOH) (p(DMAAm-co-MA)/NaOH or DM3), respectively. The synthesized hydrogels were named DM1, DM2 and DM3, respectively. The swelling properties, urea sorption and urea release kinetics of synthesized hydrogels were analyzed in deionized water at different pHs. The sorption isotherms and sorption parameters were investigated thoroughly for all hydrogels and the Langmuir (L) isotherm showed the best fit. In order to examine the urea release mechanism from all hydrogels, four mathematical models of zero-order kinetic model (Z-O), first-order kinetic model (F-O), Higuchi (H) and the Korsmeyer–Peppas power law (K-P) were studied to fit the experimental data. The hydrogels exhibited swelling and releasing properties that were highly dependent on their functional groups and the ionic forces in the medium. Cumulative urea release values for DM1, DM2 and DM3 were calculated as 100% at pH 10, 100% at pH 8 and 100% at pH 8 within 48, 41 and 18 h, respectively. It was confirmed by experimental studies that the prepared hydrogels and their derivatives can be used as carriers for fertilizers, particularly urea, as well as controlled water release sources. As a result, the use of the synthesized hydrogels to prevent contamination of water resources with agricultural products and to provide a nitrogen source that plants require comprise the innovative and original aspect of the article.
... (10) Ha sido reportado que estas estructuras granulares contribuyen a estabilizar la estructura del suelo, a mejorar la aireación, la permeabilidad y la calidad del suelo, reduciendo el agrietamiento, minimizando la compactación del suelo para prevenir que se endurezca, y ofrecen un ambiente favorable para el crecimiento de los cultivos. (11) Los hidrogeles de poliacrilamida entrecruzada, añadidos a los suelos en proporciones de entre 5 y 10 g/kg, reducen la infiltración del agua en los suelos hasta en un 87-94 %. (4) ...
Article
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Polyacrylamide hydrogels were produced by simultaneous synthesis and crosslinking, induced by gamma radiation in a 60Co irradiator, from a monomeric solution of 1, 26 M acrylamide. Obtained hydrogels were chemically modified by incomplete basic hydrolysis, using potassium hydroxide to achieve a poly(acrylamide-co-potassium acrylate) copolymer. The swelling process of samples in distilled water fits first order kinetic models, and second order kinetics in conditions of both acid and basic pH at constant ionic force. The best swelling values are obtained for samples irradiated at 10 kGy and modified with potassium hydroxide for 1 h, thus achieving a weight gain of over 1000 times its weight in distilled water, whereas in pH buffers the optimum absorption capacity for an agricultural-used hydrogel was slightly exceeded, increasing its weight 60 times over.
... Simultaneously it is reported by several scientist that the fertilizers mixed with nano-clays and Zeolites may increase the fertilizers use efficiency in both agro-ecosystem and forest system. It also increases the soil fertility by releasing fixed nutrients into the soil [20][21][22][23]. Azizi and Safaei [24] used nano-fertilizer on Nigella sativa L. and found positive effect on its yield, other yield components and essential oil content. ...
Article
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Relatively a new branch of technology, Nanotechnology has been found effective and applicable in various scientific disciplines. Its effectiveness has attracted many researchers to use it for solving various issues related to the natural resource management. Lots of studies have been carried out so far and published related to the applications of nanotechnology in climate science, forestry, agro-ecosystem, medical science and industrial sectors. Solving climate change issues in forestry sector, development of new nanomaterials for the management of forests from risks like drought, flood, salinity, fire, invasion, pathogen etc., water resource management in forest system, increasing energy efficiency of forests, improved forest produce, applications in forest based paper industries and other potential domains and its application has been reviewed in this paper along with some of frequently used nanomaterials, generally used or have potential to be used. Some industries currently using this technology are also enlisted. It was concluded that the nanotechnology has significant scope in the field of forestry as an enabling technology yet the future directions and requirements of applying nanotechnology in forestry sector are still in budding stage especially in India and may be applied at large scale by facilitating technical and legal institutions, large R&D grants and research collaborations.
... (10) Ha sido reportado que estas estructuras granulares contribuyen a estabilizar la estructura del suelo, a mejorar la aireación, la permeabilidad y la calidad del suelo, reduciendo el agrietamiento, minimizando la compactación del suelo para prevenir que se endurezca, y ofrecen un ambiente favorable para el crecimiento de los cultivos. (11) Los hidrogeles de poliacrilamida entrecruzada, añadidos a los suelos en proporciones de entre 5 y 10 g/kg, reducen la infiltración del agua en los suelos hasta en un 87-94 %. (4) ...
Article
Se producen hidrogeles de poliacrilamida mediante síntesis y reticulación simultáneas inducidas por radiación gamma en un irradiador de 60Co. Los hidrogeles obtenidos se modifican químicamente mediante hidrólisis básica incompleta con hidróxido de potasio, para lograr un copolímero de poli(acrilamida-co-acrilato de potasio). El proceso de hinchamiento de las muestras se ajusta a modelos de cinética de primer orden en agua destilada y de segundo orden en condiciones de pH ácido y básico a fuerza iónica constante. Los mejores valores de hinchamiento se obtienen para las muestras irradiadas a 10 kGy y modificadas con hidróxido de potasio durante 1 hora, alcanzando estas una ganancia en peso considerable para agua destilada, mientras que en los tampones de pH se excede ligeramente la capacidad de absorción óptima para un hidrogel de aplicación agrícola. Polyacrylamide hydrogels were produced by simultaneous synthesis and crosslinking, induced by gamma radiation in a 60Co irradiator. Obtained hydrogels were chemically modified by incomplete basic hydrolysis, using potassium hydroxide to achieve a poly(acrylamide-co-potassium acrylate) copolymer. The swelling process of samples in distilled water fits first order kinetic models, and second order kinetics in conditions of both acid and basic pH at constant ionic force. The best swelling values are obtained for samples irradiated at 10 kGy and modified with potassium hydroxide for 1 hour, thus achieving a remarkable weight gain in distilled water, whereas in pH buffers the optimum absorption capacity for an agricultural-used hydrogel was slightly exceeded.
... This process is called the swelling process. 1 Therefore, SAHs are water-preserving products used for the delivery of drugs, 2 enzymes immobilization, 3-5 protein dewatering, separation of solutes, and soil conditioners in agriculture. 6,7 When copolymerized with synthetic polymer or monomer, seminatural polymer form semi-interpenetrating polymer (semi-IPNs). 8,9 . ...
Article
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A copolymer hydrogel consisting of Polyacrylic Acid (PAAc) combined with an irradiated solution of carboxymethyl cellulose (CMC, 1 wt%) was prepared. The focus was on controlling the radiation degradation of CMC by exposing it to different six doses of γ‐irradiation from 0 up to 3 kGy. After the irradiation process, the six CMC solution samples were mixed with 10 vol% of Acrylic Acid (AAc) monomer and re‐irradiated at a dose of 25 kGy to begin the polymerization process. A scanning electron microscope (SEM) was used to image the macroporous structure of the obtained (CMC/PAAc) hydrogel. Moreover, the SEM image confirmed the interpenetrating and semi‐interpenetrating polymer network structure based on the irradiation process. The controlled release of urea is achieved due to the binding between urea and the functional groups of the investigated hydrogel by hydrogen bonds. The growth of common bean plant (Phaseolus vulgaris L.) and chlorophyll contents were increased when soils were treated with (CMC/PAAc) compared with soils with free hydrogel in water‐stress conditions.
... 7−10 Besides, nanofertilizers have many benefits such as improving soil fertility, reducing nutrient loss, increasing crop yield, lowering environmental pollution, and giving a feasible environment for microorganisms. 11 Many researchers have formulated slow-release fertilizers by incorporating hydroxyapatite (HA) and urea to increase delivery of nutrients to the plants. 12−14 In this background, we report here a hybrid nanofertilizer (HNF) composition with some extension, which is made by incorporating nanourea-modified hydroxyapatite nanoparticles into copper, iron, and zinc nanoparticles. ...
Article
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In this work, we have proposed a new formulation of a hybrid nanofertilizer (HNF) for slow and sustainable release of nutrients into soil and water. Urea-modified hydroxyapatite was synthesized, which is a rich source of nitrogen, calcium, and phosphate. Nanoparticles such as copper, iron, and zinc were incorporated into urea-modified hydroxyapatite to increase the efficiency of the proposed fertilizer. Different techniques including powder X-ray powder diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy were used to get insight into the properties, morphology, and structure of the as-prepared fertilizer. The developed HNF was used in a field experiment on the ladies' finger (Abelmoschus esculentus) plant. The slow release of HNF was observed during leaching studies and confirmed the availability of Ca 2+ , PO 4 3− , NO 2− , NO 3− , Cu 2+ , Fe 2+ , and Zn 2+. Furthermore, the presence of Cu 2+ , Fe 2+ , and Zn 2+ nutrients in ladies' finger was confirmed by the inductively coupled plasma-optical emission spectrometry (ICP-OES) experiment. A considerable increase in the physicochemical properties such as swelling ratio and water absorption and retention capacities of the proposed fertilizer was observed, which makes the fertilizer more attractive and beneficial compared with the commercial fertilizer. The composition of the proposed HNF was functionally valuable for slow and sustainable release of plant nutrients. The dose of prepared HNF applied was 50 mg/week, whereas the commercial fertilizer was applied at a dose of 5 g/week to A. esculentus. The obtained results showed a significant increase of Cu 2+ , Fe 2+ , and Zn 2+ nutrient uptake in A. esculentus as a result of slow release from HNF.
... With the use of controlled-released systems, nutrients are released at a slower rate throughout the seasons, plants are able to take up most of the nutrients without waste by leaching (Kanjana, 2017;Nayan et al., 2018). Superabsorbent polymers (SAP), a new functional polymer material, can absorb a large amount of water, swell to many times their original size and weight and the water is hardly removed even under pressure, and so it has been widely used in agriculture as controlled-release fertilizer (Liu et al., 2006). Hydrogel is a loosely cross-linked three dimensional networks of hydrophilic monomer with the ability to absorb great amount of water. ...
Conference Paper
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This paper reported on the reinforcement of superabsorbent (SA) fertilizer based from polyvinyl alcohol (PVA) using chitosan via superficial freeze-thawing method. The obtained SAP beads are well developed with excellent mechanical properties and high NPK compound fertilizer loading at 6 wt% chitosan loading. The effect of PVA/chitosan hydrogel on plant growth and fruiting yield was observed using Capsium sp.by comparing with conventional fertilizer. The studies showed plant samples with PVA/chitosan hydrogel growth exceptionally in term of its number of fruits(43±1), total mass fruit yield (1654±1.3g), fresh and dry weight of plant (139.5±1.2%), leaf number (130.6±0.2%) and width (19.8±0.6%) as well as chlorophyll content (0.036659) compared to conventional fertilizer method. Overall, these give good indication of the modified SAP fertilizer as a new technology to be used in future agriculture.
... Bhattacharya et al. (2004) reported that the balanced application of nitrogen, phosphorous, and potassium along with sulfur, zinc, boron, and molybdenum will be an effective solution for higher grain yield of pulses in red and lateritic soils. Liu et al. (2006) have shown that the organic material (polystyrene) intercalated in the layers of kaolinite clay forms a cementing of nano-and subnano-composites which are capable of regulating the release of nutrients from the fertilizer capsule. Thus nanoparticles could be used in the membrane control release of nutrients. ...
Chapter
Nanotechnology plays a significant role in promoting agriculture and agricultural products. Agriculture and food industry aims for the sustainability and the protection of agricultural products, including crops for human and livestock. It helps in the manufacturing of innovative agrochemicals and novel delivery mechanisms to enhance crop production and decrease the use of chemical fertilizers and pesticides. It acts as an important tool in agriculture to improve crop growth, yield, and quality parameters with increased nutrient use efficiency, reduced wastage of fertilizers and cost of cultivation. These nanostructures have shown slow degradation and controlled release of active ingredient for long time. Because of the limitation in arable lands and water resources, the development of agriculture sector is only possible by increasing resources use efficiency with minimum damage to production bed through effective use of modern technologies. These nano-agro-formulations increase nutrient use efficiency, reduce soil toxicity, minimize the potential negative effects associated with over dosage, and reduce the frequency of the application. Hence, nanotechnology has high potential for achieving sustainable agriculture, especially in developing countries. Here we summarize the scope and economic aspects of nano-formulations.
... It may be noted that protein-based hydrogels, such as collagen derived from industrial by-products, are promising materials for controlled-release applications in agriculture. Copolymers bearing functional groups cross-linked with the collagen matrix will efficiently incorporate the desired nutrients and act as biostimulators in controlled-release fertilizer technology [21,22]. With that knowledge in mind, the development of novel cross-linked hydrogels through the modification of collagen derivatives with water-soluble polymers was an interesting challenge for us. ...
Article
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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.
... Superabsorbent polymers (SAPs) have the ability to absorb liquids up to several thousand times of their own weight, keeping this water in the structure for long periods of time. Superabsorbent polymers are extensively used in baby diapers [16] and agriculture [17][18][19][20] but their use in self-healing coatings is limited to a handful of works. Yabuki et al. showed that a SAP could act as a self- healing agent in a vinyl-epoxy liquid coating [21] and some patents were filed showing the potential of SAPs for water blocking in optical cables [22]. ...
Article
Superabsorbent polymers (SAPs) are well known for their ability to absorb and hold high water amounts accompanied by a high volume expansion. In this work we show the benefits of this underlying property of SAPs to induce underwater crack closure with subsequent barrier restoration in damaged protective coatings. For the proof of concept, three layer epoxy-polyester (EP) powder coating systems were developed and applied on carbon steel. In these systems the middle EP layer (also called functional layer) contained crosslinked acrylamide/acrylic acid copolymer SAPs in different amounts ranging from 0 to 40 wt%. The capability of the SAPs to close damages and extend barrier and corrosion protection was evaluated by electrochemical impedance spectroscopy (EIS), NaCl aqueous solution immersion test and optical microscopy. It was found that coatings loaded with a 20 wt% SAP led to the best overall corrosion protection for the studied systems. In order to proof the potential use of this extrinsic healing concept for multiple healing events wet-dry cycles on scratched systems were performed and the corrosion performance was followed by EIS. Although not yet optimal, the results show the potential of the concept for multiple healing events under wet-dry conditions.
... In the initial stage, the polymerization and the crosslinking reactions processed normally, more cross-linking reactions happened, and more network structure of the composite formed. The monomer conversion ratio increased and then the soluble fraction of the composite decreased [41], thus, the water absorbency of composite rose as the reaction time prolonged. However, when the reaction time was too long, many branched chains would be formed in the network structure, the chains would entangle with each other and hinder the expansion and stretching of the polymer. ...
Article
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Cellulose-based superabsorbent was synthesized by bacterial cellulose (BC) grafting acrylic acid (AA) in the presence of N,N′-methylenebisacrylamide (NMBA) as a crosslinker and ammonium persulfate (APS) as an initiator. The influence of different factors on composite synthesis, including the weight ratio of the monomer to BC, initiator content, crosslinker content, AA neutralization degree, reaction temperature, and reaction time on the water absorbency of the composite, were systematically learned. Under the optimized conditions, the maximum water absorbency of the composite was 322 ± 23 g/g distilled water. However, the water absorbency was much less for the different salt solutions and the absorption capacity of the composite decreased as the concentration of the salt solutions increased. The pH value had a significant influence on water absorption performance, and with the increase of temperature, the water retention rate of the composite decreased. Additionally, the structure of this composite was characterized with nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The results of NMR and FT-IR provided evidence that the composite was synthesized by BC and AA, and the microstructure showed that it had good performance for water absorption. In addition, the composite possessed suitable thermal stability, and that it could be used in a few high-temperature environments. Overall, this composite is promising for application in water absorption.
... As a result, the driving force for water diffusing into the superabsorbent is weakened, and then the water absorbency decreases. [17,10,3,20] . ...
Article
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Use of innovative nano clay polymer composite (NCPC) superabsorbent was explored particularly to ameliorate moisture stress condition under rainfed ecosystem. NCPC were synthesized by polymerization reaction with 10% acrylic acid, acrylamide, 0.9% ammonium per sulphate as initiator, 0.12% N, N′-methylene bis acrylamide loaded with 10% kaolinite clay at 65 0 C reaction temperature in presence of inert nitrogen gas. The water sorption was found maximum (131.25 g H 2 O/g NCPC) when kaolinite clay was modified by hot water FYM extract irrespective of amount of loaded phosphorus in NCPC (treatment 15 & 16) as compared to pure clay 90.04 g H 2 O/g NCPC without any modification (T14). The average water desorption pattern was also found to be conducive when clay was modified by hot water FYM extract. The rate kinetics for water sorption and desorption was studied under different innovative modified NCPC. The present study revealed that when NCPC added in alluvial soil it helps to maintain soil moisture regime for additional 8-13 days more (depending on composition) as compared to no application of NCPC in soil. Superabsorbent polymeric materials in combination with modified clay play a significant role in improving and retaining soil moisture regime and further reducing the rate of desorption of water act as an effective material for higher water use for agricultural applications.
... Superabsorbents are crosslinked hydrophilic polymers which can absorb large amount of water. They can be used widely in the field of drug delivery, immobilization of enzymes, solute separation, baby diapers and soil conditioner for agriculture and horticulture [1,2]. The agricultural application of superabsorbent hydrogels especially for use in dry and desert regions may improve soil for cultivation [3]. ...
Article
Superabsorbent hydrogels (PVP/CMC) based on polyvinylpyrrolidone (PVP)/carboxylmethyl cellulose (CMC) of different copolymer compositions were prepared by gamma radiation. Factors affecting the gel content (%) and the swelling ratio (g/g) of hydrogel such as irradiation dose as well as copolymer composition were investigated. With increasing the CMC content in PVP/CMC hydrogels, increases the swelling and improves the water retention capability. The high swelling ratio was observed at copolymer composition of PVP/CMC (60/40). Fast swelling of the hydrogels was obtained after 20 min. The effect of different fertilizers and buffers of different pH’s on equilibrium swelling of hydrogels was investigated. Fertilizers such as urea, monopotassium-phosphate (MPK), and nitrogen-phosphate-potassium (NPK) were loaded onto the hydrogel to supply nitrogen, potassium and phosphorous nutrients. PVP/CMC hydrogels retained 28–36% after 72 h and slow retention was noticed up to 9 days. The swelling of hydrogel in fertilizer solutions is lower than that in water. The hydrogels showed adsorption desorption of fertilizers which governs by slow release property. The release rate of urea is much higher 10 times than that of phosphate. After 3 days, urea released 60%, while phosphate released 10–12%. The applicability of PVP/CMC hydrogels in the agricultural fields shows greater growth effect on zea maize plants. The growth of zea maize plant in soil mixed with PVP/CMC hydrogels loaded fertilizers is greater than untreated soil. The slow release fertilize, the high swelling and the slow water retention behaviors of PVP/CMC hydrogels encourage their use as safer release systems for fertilizers and as soil conditioner in agricultural applications.
Chapter
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Synthetic polymer hydrogels and modified natural polymer hydrogels are widely and increasingly used in agriculture, health care textiles, effluent treatment, drug delivery, tissue engineering, civil concrete structure, etc. Among them, the use of hydrogels in agricultural and horticultural sectors as matrices for the controlled release of water, various primary and secondary nutrients has drawn significant attraction from researchers, scientists, and industry persons due to their smartness with reference to controlled release characteristics based on plant requirement. Since the use of these hydrogels for controlled release application ensures the minimum utilization of water and plant nutrients in fields. Besides, this will bring down the overloading of fertilizer, soil contamination, and water pollution such as eutrophication, nitrate pollution, and micronutrient imbalance. This chapter is focused on the class of hydrogels that are used for the controlled release application in the agricultural and horticultural sectors as matrices, the possible methods of fine-tuning their structures for improving their fertilizer uptake and release behavior, safety aspects, and environmental issues.
Article
Nowadays, the development of mucoadhesive systems for drug delivery have gained keen interest, with enormous potential in applications through different routes. Mucoadhesion characterizes an attractive interaction between the pharmaceutical dosage form and the mucosal surface. Many polymers have shown the ability to interact with mucus, increasing the residence time of local and/or systemic administered preparations, such as tablets, patches, semi-solids, micro-and nanoparticles. Cellulose is the most abundant polymer on the earth. It is widely used in the pharmaceutical industry as an inert pharmaceutical ingredient, mainly in its covalently modified forms: methylcellulose, ethylcellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methylcellulose and carboxymethylcellulose salts. Aiming to overcome the drawbacks of oral, ocular, nasal, vaginal, and rectal routes, and thereby maintaining patient compliance, innovative polymer blends have gained the interest of the pharmaceutical industry. Combining mucoadhesive and thermoresponsive polymers allows for simultaneous in situ gelation and mucoadhesion, thus enhancing the retention of the system at the site of administration and drug availability. Thermoresponsive polymers have the ability to change physicochemical properties triggered by temperature, which is particularly interesting considering physiological temperature. The present review provides an analysis of the main characteristics and applications of cellulose derivatives as mucoadhesive polymers and their use in blends together with thermoresponsive polymers, aiming platforms for drug delivery. Patents were reviewed, categorized, and discussed focusing the applications and pharmaceutical dosage forms using this innovative strategy. This review manuscript also provides a detailed introduction to the topic and a perspective on further developments.
Article
The elimination and recycling of NH3 from the vented circulating stream of NH3 synthesis process is of great significance to the protection of air environment and saving of NH3 product. Deep eutectic solvents (DESs) with as many weak acidic sites as possible are anticipated to exhibit high efficiency for NH3 absorption at low pressures. Herein, we designed and prepared a series of metal‐based DESs by mixing EaCl, metal chloride (SnCl2, ZnCl2, FeCl3 or CoCl2) and Gly. The physiochemical properties, NH3 absorption performance and mechanism of prepared metal‐based DESs were investigated systematically. It is found that considerably high solubilities of NH3 in DESs can be achieved by utilizing the multiple coordination and hydrogen‐bond interaction with NH3 provided by metal ions and Gly respectively. The values of NH3 solubilities (17.55 mol/kg at 298.2 K and 103.0 kPa, and 10.24 mol/kg at 298.2 K and 6.8 kPa) are the highest reported to date.
Chapter
Hydrogels are hydrophilic crosslinked polymeric structures with versatile properties. There are numerous ways to synthesize hydrogel materials, namely physical crosslinking involving freeze and thawing, ionic interaction , etc., and chemical crosslinking involving free radical polymerization, esterification, etherification, etc. Based on the chemical structure, hydrogels can be classified into homopolymeric hydrogels, copolymeric hydrogels, interpenetrating hydrogels, etc.. Due to their polymeric versatility, they have been in use as carrier for various bioactive materials, including drugs, nutraceuticals, and agricultural inputs such as fertilizers, pesticides, etc.. Hydrogels application alone finds its superiority in enhancing water use efficiency in water stress farming. Furthermore, fertilizer-and pesticide-encapsulated hydrogels leads to slow release of the same leading to less environmental pollution and judicious use of agricultural inputs. Despite their well-recognized role in improving water use efficiency and fertilizer application explored in individual research and academic pieces of work, the hydrogels still find difficulty in finding a widespread adoption in tropical agriculture, particularly in India. CHAPTER 17
Article
There have been a lot of reports on the preparation and properties of superabsorbent polymers, but there are still some problems and limitations in practical application. Therefore, a superabsorbent polymer (SAP) was synthesized by solution polymerization with tap water as reaction medium, acrylic acid and cross-linked polyvinylpyrrolidone (PVPP) as raw materials. The results of its performance and application show that the particle size was 0.425~0.85 mm, and the maximum water absorption rate of SAP in distilled water, tap water and 0.9% wt% NaCl solution was 2297 g/g, 333 g/g and 120 g/g, respectively. The water absorption rate can reach about 80% of maximum water absorption rate in 30 minutes. In addition, when the SAP mass addition amount was 0.56% and the particle size was 0.15 ~ 0.25 mm, the saturated moisture of sandy soil increased by 187%, the infiltration rate of sandy soil decreased by 96.7% and at 45°C and 25°C, the water evaporation rate of sandy soil decreased by 57.52% and 43.61%, respectively. So the material have a good application prospect in desertification and agriculture, and the way of preparation can be more effectively applied in practical production.
Article
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Superabsorbent polymers (SAP) and modified natural polymer hydrogels are widely and increasingly used in agriculture, health care textiles, effluent treatment, drug delivery, tissue engineering, civil concrete structure, etc. However, not many comprehensive reviews are available on this class of novel polymers. A review covering all the viable applications of SAP will be highly useful for researchers, industry persons, and medical, healthcare, and agricultural purposes. Hence, an attempt has been made to review SAPs with reference to their classifications, synthesis, modification by crosslinking, and physicochemical characterization such as morphology, swellability, thermal and mechanical properties, lifetime prediction, thermodynamics of swelling, absorption, release and transport kinetics, quantification of hydrophilic groups, etc. Besides, the possible methods of fine-tuning their structures for improving their absorption capacity, fast absorption kinetics, mechanical strength, controlled release features, etc. were also addressed to widen their uses. This review has also highlighted the biodegradability, commercial viability and market potential of SAPs, SAP composites, the feasibility of using biomass as raw materials for SAP production, etc. The challenges and future prospects of SAP, their safety, and environmental issues are also discussed.
Chapter
Heavy metals are environmental pollutants that affect air, water, and land because of highly toxic and recalcitrant nature. Due to their adverse impacts on the natural environment and human health, there is dire need for their eradication. Various remediation technologies were employed for clean up the environment which includes chemical coagulants, electrochemical, photocatalytical oxidation, ion exchange, etc. Among all of these, nanotechnology is the most suitable approach for the remediation because of its enhanced properties encompasses high surface area to volume ratio disposable quality, high reactivity which offers a profound potential remediation of environmental contaminants. This chapter summarizes recent nano techniques employed for the removal of elimination of heavy material.
Chapter
Nanotechnology has proved its potential in bringing improvement in the agricultural sector via application of nanofertilizers, nanopesticides, and use of products such as nanosensors. Nanofertilizers facilitate slow and steady release of nutrients thereby increasing productivity of the soil. They enhance nutrient use efficiency and reduce the loss of nutrients. Enhancement in the photosynthetic capacity in plants caused due to increased availability of nutrients leads to production of high yield and dry matter. Use of nanofertilizers proves advantageous because it reduces frequency of application of chemical fertilizers and hence soil toxicity. Nanotechnology can thus prove as a technique with immense potential for improving agricultural productivity and help us in achieving sustainable agriculture.
Article
Novel nanocomposite hydrogels were successfully prepared by blending and crosslinking sodium alginate (SA), poly(vinyl alcohol) (PVA) and cellulose nanofibers (CNFs) in the presence of a fertilizer formulation containing nitrogen (N), phosphorus (P) and potassium (K). The hydrogels had a macroporous flexible core and a microporous semi- interpenetrating polymer network (IPN) shell. The crystalline nature of the NPK chemicals was retained in the hydrogel nanocomposite network. Furthermore, the SA/CNF/PVA-based hydrogels showed a higher water-retention capacity in both deionized water and mixed soil. The swelling behavior in various physiological pH, salt and alkali solutions exhibited good sensitivity. The NPK release from SA/CNF/NPK and SA/CNF/PVA/NPK hydrogels was controlled by Fickian diffusion in both water and soil based on the Korsmeyer-Peppas release kinetics model (n < 0.5). Therefore, the prepared hydrogels have the potential for applications in drought-prone and/or fertilizer-loss regions for future development of precision agriculture and horticulture.
Article
An efficient cellulosic superabsorbent based on a novel functional monomer 4-(6-aminohexyl) amino-4-oxo-2-butenoic acid (AHOB) and acrylic acid was successfully synthesized by free-radical solution polymerization and the effect of the AHOB monomer on the structure, morphology, thermal behavior and viscoelastic features of this superabsorbent was investigated by FTIR, SEM, TGA and rheology methods. Also, the influence of this monomer on the water absorption capacity in various pH and different saline solutions, kinetic behavior, water retention capacity and reusability of the superabsorbent was perused. The results of these experiments confirmed the significant role of the AHOB monomer in improving the properties of the superabsorbent. The excellent absorbency (800.37 g/g in distilled water and 78.02 g/g in 1 wt.% NaCl solution) and high water retention capacity of the prepared superabsorbent showed that it can be used as an efficient water-saving material for agricultural applications.
Chapter
Effect of reactants concentration on swelling properties of cellulose-acrylic hydrogels was investigated in this study. The composite hydrogels with interpenetrated polymer networks (IPNs) comprising low amount of cellulose nanofibrils (CNFs) were synthesized through radical polymerization. Cellulose concentration was changed from 0.5 wt% to 2.5 wt% by using different amounts of water. The swelling behavior was measured in different aqueous media and fertilizers such as urea and ammonium sulfate solution. The absorption ranges of hydrogels in saline water (0.9 wt%) and ammonium sulfate (0.12 mol/L) are significantly lower than those in other absorption media (<25 g/g). The equilibrium absorption of the prepared hydrogels in urea solution, drinking water and distilled water changed from 62 g/g to 64 g/g, 54 g/g to 68 g/g, and 71 g/g to 79 g/g, respectively. Absorptions under load (AUL) data presented a slight decrease in strength at low cellulose concentration (0.5 wt%).
Chapter
Fertilizers are long being utilized in agricultural sector for crop maintenance but the problem with the conventional fertilizers is their persistence in soil for longer period of time causing barrenness of soil. As a result, plants are deprived of essential nutrients. Nano fertilizers provide best possible solution to overcome this problem as they are released on demand, site specific, efficient and easily soluble. In recent years bio nanofertilizers have gained much interest over the conventional chemical fertilizers as these are environment friendly and cost effective. Increased demand of food with outburst of global population can be dealt with the nanofertilizers in agricultural system. It is an efficient way to produce early germination of seed which in turn can help rapid and early crop production in short period of time. The application of these fertilizers at optimum concentration boosts the crop yield though the overdose can cause a decline or reduction in crop production because of their mineral toxicity. For various metabolic reactions nanofertilizers offers great surface area that increases photosynthesis rate, improves the crop biomass and also help the crop to combat environment stress.
Article
Hydroxyethylcellulose (HEC) is a biocompatible, biodegradable, nontoxic, hydrophilic, non- ionic water soluble derivative of cellulose. It is broadly used in biomedical field, paint industry, as a soil amendment in agriculture, coal dewatering, cosmetics, absorbent pads, wastewater treatment and gel electrolyte membranes. Industrial uses of HEC can be extended by the its grafting with different polymers including poly acrylic acid, polyacrylamide, polylactic acid, polyethyleneglycol, polydimethyleamide, polycaprolactone, polylactic acid and dimethylamino ethylmethacrylate. This permits the formation of new biomaterials with improved properties and versatile applications. In this article, a comprehensive overview of graft copolymers of HEC with other polymers/compounds and their applications in drug delivery, stimuli sensitive hydrogels, super absorbents, personal hygiene products and coal dewatering is presented.
Chapter
Fundamental definitions, classification, and applications of smart polymer gels are the main discussions of this chapter. Smart polymer gels are polymer network structure which swell or shrink as a response to the changing in surrounding environment. Smart polymer gels are able to absorb high amount of water or biological fluid and release it when particular characteristic such as temperature, light, pH, and electric field of the surrounding medium is changed. Chemical compositions of the main materials of smart polymer gels are the main factors that determine the final properties. Smart polymer gels have an extensive range of application in medical such as drug delivery system, artificial muscle, and actuators. In addition, smart polymer gels are used in water treatment as ions and dyes adsorbents.
Article
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In this study, composite hydrogels with interpenetrated polymer networks (IPNs), based on bacterial cellulose (BC) and poly(acrylic acid-co-N,N′-methylene-bis-acrylamide) (PAA), were synthesized by radical polymerization and characterized herein for the first time. Liquid fertilizer (LF) formulations, containing potassium, phosphorus, ammonium oxides and micronutrients, were encapsulated directly into the IPNs of the composite hydrogels during synthesis. Thermal analyses and scanning electron microscopy of control and composite xerogels highlighted the formation of IPNs between BC and PAA. Swelling determinations confirmed the influence of the crosslinker and of the liquid fertilizer concentration upon the density of the IPNs. Further rheology studies and release profiles indicated how the presence of BC and the increase of the crosslinking density of IPNs improved the mechanical strength and the release profile of LF for the innovative composite BC-PAA hydrogels. Results regarding the fertilizer release indicated that the presence of the BC led to a more controlled liberation of the fertilizer proving that this new formulation is potentially viable for application in agricultural practices.
Article
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Superabsorbent hydrogels based on polyacrylamide (PAAm) and Na-alginate (Alg) or chitosan (CS) were synthesized by γ-rays. The effect of dose and copolymer composition on gel content and water absorbency of PAAm/Alg, PAAm/CS and PAAm/Alg/CS hydrogels were studied. The gel content and water absorbency follows the order PAAm/Alg > PAAm/Alg/CS > PAAm/CS. The effect of different cations, fertilizers, buffers on water absorbency of the hydrogels was investigated. Water retention capability of swollen hydrogels as a function of time was studied. PAAm/Alg hydrogel has a high water retention capability. An application of the prepared hydrogels in agricultural fields was performed using maize plants. The results showed that the presence of hydrogels had growth promotion effect on quality and quantity of maize plants. The plants treated by PAAm/Alg hydrogels showed 50% increase in the grain yield suggesting their possible use as a soil conditioner and a water reservoir for plant-soil system.
Article
Starch-g-poly(acrylic acid)/organo-mordenite superabsorbent composite microsphere, was prepared by grafting partially neutralized acrylic acid onto starch in the presence of organo-mordenite as an inorganic component. The morphology was characterized with scanning electron microscope (SEM). The swelling properties of the superabsorbent composite microsphere were evaluated in distilled water, various NaCl solutions, solutions with different pH values, and urea solutions. Swelling kinetics of the superabsorbent composite microsphere in above environments were discussed by means of a Schott’s second-order model. The results showed that the incorporation of 10 wt% organo-mordenite enhanced the water absorbency by 144% (from 268 to 655 g · g⁻¹) and possessed the maximum swelling absorbency (75 g · g⁻¹) in the 0.9% NaCl solution and (667 g · g⁻¹) in 0.04 mol · l⁻¹ urea solution. Moreover, swelling of starch-g-poly(acrylic acid)/organomordenite (with 10 wt% organo-mordenite) in distilled water and in all other environments followed Schott’s second order kinetics. Swelling was extremely environmental-responsive to the concentration of the NaCl solution, the pH values, and urea solutions, respectively. The overall results inferred that the novel superabsorbent composite can be exploited for many potential applications.
Conference Paper
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A new hydrophilic network polymer based on polystyrene is used as a soil conditioner in cultivation of a leguminous plant (Medicago sativa).The effects of this resin on a selective strain of Rhizobium meliloti which is used by this plant for nitrogen fixation is investigated. No adverse effects were observed in the growth rate of Rhizobium in liquid cultures. Optimum pH value in contact with resin was found to be 6.8. No loss of effectiveness was also observed on Rhizobia isolated from nodules of plants of Medicago sativa. It was found that the soil conditioner considerably increased dry biomass yield.
Article
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Cerium(IV) mediated grafting of polyacrylonitrile on to guar gum was studied. Grafting parameters were studied gravimetrically, as a function of temperature, initiator concentration and Guar to acrylonitrile ratio. Higher temperatures resulted in higher monomer conversion and homopolymer formation. Both monomer conversion and extent of grafting increased with increase in cerium ion concentration in the range studied (0.91–9.12 mmol/l). Similar results were obtained with increase in monomer to guar gum ratio from 1 to 5. Grafting with this initiator was found to be generally good with high grafting efficiencies and low homopolymer formation for most experiments. The copolymers obtained were subjected to alkaline hydrolysis to convert nitrile groups in to carboxylic acid groups and the water absorbency of the resulting anionic guar gum was studied. Materials with water absorption up to 300 g/g could be obtained from this study. Copyright © 2003 John Wiley & Sons, Ltd.
Article
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In this study, highly swollen acrylamide/crotonic acid hydrogels (in a rod form) containing some inorganic salts such as ammonium nitrate, potassium nitrate and ammonium sulphate used as fertilizer, an agricultural drug such as Dalapon (sodium 2,2-dichloropropionate) and two crosslinkers such as ethylene glycol dimethacrylate and 1,4-butandiol dimethacrylate were prepared by copolymerization of acrylamide and crotonic acid with γ-radiation. As a result of swelling tests, the influence of γ-ray dose and relative content of crotonic acid on the swelling properties, the diffusional behavior of water, diffusion coefficients and network properties of the hydrogel systems were examined. Acrylamide/crotonic acid hydrogels containing these salts and agricultural drug were swollen in the range 2045–400% in water, while polyacrylamide hydrogels swelled in the range 660–700%. Water intake of hydrogels followed a nonFickian-type diffusion. Copyright © 2000 John Wiley & Sons, Ltd.
Chapter
Superabsorbent polymers, used in infant diapers to absorb body fluids, are prepared from acrylic acid and a crosslinker, in aqueous solution or in a suspension of the aqueous solution in a hydrocarbon. The product is partially neutralized either before or after the polymerization step. Combinations of redox and thermal free-radical initiators, chelating agents, chain-transfer agents, and grafting agents are used to control the polymerization kinetics and molecular characteristics of the network. The key properties of swelling capacity and gel modulus are controlled by the choice and amount of cross-linker. The gel-like polymer mass resulting from the polymerization is dried in continuous ovens, and the dry polymer milled to the desired size. Particle size of the product from suspension polymerization is controlled by choice of suspending agent.
Article
The water uptake and swelling behaviour of physically crosslinked, inhomogeneous poly(acrylonitrile-acrylamide-acrylic acid) hydrogels from 10 to 60°C were determined by gravimetry/differential scanning calorimetry and volume measurement, respectively. The contents of water and its non-bound portion were found to reach a minimum value at acrylamide content around 33.5 mol%, at which the water uptake of this gel does not vary with the temperature. The non-bound water was found to decrease gradually and then increase with increasing amide concentration. The duration of the post-gelation treatment between − 10 and 10°C was also shown to be one of the factors affecting the extent of the water uptake in gels. The critical endpoint temperatures (Tcs) of hydrogels, obtained from volume phase transition data upon changing the acetone concentration in aqueous solutions at various temperatures, were shown to decrease with the increasing acid or amide contents. The water uptake for gels with lower amide contents decreases with increasing temperature. However, there is an opposite trend for water uptake in gels with higher amide content, and the critical points on the plots of the amount of water uptake versus temperature appear at a temperature equal to Tc.
Article
The combined action of a soil conditioner and a controlled‐release fertilizer was followed by conducting soil column leaching and tomato growth experiments. The change in soil water‐holding capacitiy and the release of potassium sulfate (K2SO4) from conventional and controlled‐release forms was evaluated using leaching experiments in soil columns. Tomato growth was followed by the comparison of biomass yields on a dry matter basis with experiments where different combinations of controlled‐release or conventional fertilizer rates and soil conditioner applications. It was demonstrated that the combined usage of controlled‐release fertilizers and soil conditioners increased tomato yield and enhanced the nutritional status of the tomato plants in comparison to conventional fertilizer materials.
Article
A slow-release membrane-encapsulated urea fertilizer with a superabsorbent and moisture preservation was prepared by cross-linked starch (the first layer), acrylic acid (AA) and acrylamide (the second layer; AM), ammonia, borax, urea, and so on. The variable affecting the water absorbency was investigated and optimized. The water absorbency of the product was 80 times its own weight if it was allowed to swell in tap water at room temperature for 80 min. Elemental analysis results showed that the product contained 26.74% nitrogen. The water retention property of the product and the slow-release behavior of nitrogen in the product were also investigated, and the results showed that the product not only had good slow-release property but also excellent water retention capacity. This will efficiently improve the utilization of fertilizer and water resources at the same time.
Article
Three polymers (polyacrylate, vinyl‐alcohol, starch‐based) were evaluated for controlled‐release properties when expanded in urea, ammonium sulfate ((NH4)2SO4), and potassium nitrate (KNO3) solutions, at five nitrogen (N) concentrations (0,10,15, 20 g N/L, and saturation). The expansion capacity (mL solution absorbed/g dry polymer) of each polymer varied and was dependent on the type and concentration of fertilizer solution. On average, polymers incorporated with urea, (NH4)2SO4, and KNO3 fertilizer solutions had expansion capacities of 275, 24, and 30 mL/g, respectively. All three polymers reacted with ammonium ions in solution and resisted normal extraction procedures of ammonium with 2N KCl. To determine gel characteristics when applied to a soil medium, selected gel treatments were incubated in containers of loamy sand soil up to 28 days and then assessed for the quantity of gel recovered, N content, and N concentration. Although most gels released a large portion of N after only 7 days, some gels slowed diffusion better than the dry fertilizer controls up to 28 days.
Article
Dilute solution behaviour of poly(maleic anhydride-co-ethyl vinyl ether) and poly(maleic acid-co-ethyl vinyl ether) has been investigated by light scattering, osmotic pressure, and viscosity measurements. The molecular weights ( and ), the second virial coefficients A2, and the intrinsic viscosities [η] have been determined for three states of this copolymer: anhydride-form, H-form, and Na-salt independently. The constants in the Mark-Houwink relations were obtained for the above three states under different solvent conditions. The molecular weight of the anhydride-form is found to be higher than that of the acid-form or the Na-salt, suggesting the degradation in a process of hydrolysis. The second virial coefficient A2 as well as the Mark-Houwink relation indicates that the anhydride-form and H-form behave as flexible polymer chains in good solvents. However, the polymer coil of Na-salt is highly expanded even at saturated NaCl concentration.
Article
Collated bread-line NMR and DSC measurements sensitively probe the behavior of water in hydrated poly(hydroxyethyl methacrylate) (PHEMA). NMR reveals that bound water becomes mobile at ∼ 180 K in keeping with observations in many other hydrated polymers; DSC is insensitive to events at these temperatures. In samples with a high water content, a fraction of this mobile water subsequently freezes between 230 and 260 K. The amount of freezable and nonfreezable water in hydrated PHEMA is determined quantitatively. Preliminary cross-relaxation experiments at 253 and 293 K indicate that NMR spin-lattice relaxation rates for water will be overestimated if the effects of cross-relaxation between the polymer and water proton spin systems are neglected. Although PHEMA is less hydrophilic than poly(N-vinyl-2-pyrrolidone/methyl methacrylate), studied in part 1, the relative fraction of bound water is significantly higher. Hysteresis effects in hydrated PHEMA are investigated in some detail.
Article
A superabsorbent polymer with slow-release phosphate fertilizer was prepared by esterification of polyvinyl alcohol (PVA) and phosphoric acid (H3PO4), which was a slow-release fertilizer at the same time. The product's water absorbency (WA) was about 480 times its own weight if it was allowed to swell in distilled water at room temperature for 24 h. WA under various conditions, such as varying the reaction time, the amount of sodium carbonate (Na2CO3), the reaction temperature, and the concentration of phosphoric acid ([H3PO4]), were investigated and optimized. The optimal sample of the product was characterized by FTIR and elemental analysis. The results showed that phosphoric groups had grafted on PVA molecule chains, and the content of P2O5 in the product was 31.2%. The water retention property and phosphate slow-release mechanism of the product were studied as well. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3417–3421, 2004
Article
The superabsorbent's ability to resist deformation and to resist deswelling under externally applied pressures is important in practical application. For instance, it is used in infant diapers, in soil for agriculture, and in forestry. In this article, we report on the synthesis of a superabsorbent/starch-graft-poly(potassium acrylate-co-acrylamide) by inverse suspension polymerization. The effects of reaction conditions, such as monomeric concentration, ratio of water to oil, reaction temperature, and obtaining spherical resin, were investigated. Experiments showed that the superabsorbent has a good compressive strength and keeps the shape of particles after absorbing water. After mixing with soil it does not become sticky, and the loose structure can better retain air. It is fit to retain water in soil. In addition, thermogravimetric analysis revealed the superior thermal stability of the grafted product and its large particle size also reduces risk of air pollution. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1536–1542, 2003
Article
High water-absorbent copolymers comprising acrylic acid (AA) and acrylamide (AM) were prepared in the presence of a crosslinking agent, monofunctional aldehyde, by a solution polymerization technique using a redox initiation system. Such copolymers have very high water absorbency and absorbing kinetics to the distilled water. The copolymer formed which absorbed about 900 g water/g dry copolymer was used to study the influence of sodium chloride on the absorption capacity at 24°C. The swelling of this copolymer was studied in alcohol/water mixtures of increasing alcohol content at 294, 304, and 314 K. The main transition for ethanol/water and methanol/water mixtures is a rapid decrease of the retention capacity of the copolymer at 50–60 vol % ethanol and 55–65 vol % methanol, respectively. Swelling in distilled water at different temperatures (T) and the effect of solvent composition were also studied. Among the variables examined were initiator concentration, polymerization temperature, and amount of AM in the copolymer. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1345–1353, 1997
Article
A novel poly(acrylic acid)/sodium humate superabsorbent composite was synthesized by aqueous solution polymerization of acrylic acid using N, N′-methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator in the presence of sodium humate. The effects on water absorbency such as initial monomer concentration, degree of neutralization of acrylic acid, amount of crosslinker, initiator and sodium humate, etc. were investigated. The water absorbency of the superabsorbent composite synthesized under optimal synthesis conditions with a sodium humate content of 20% exhibited an absorption of 1268 g H2O/g sample and 93 g H2O/g sample in distilled water and in 0.9 wt% NaCl solution, respectively. Swelling rate and water retention tests were also carried out. The results show that sodium humate, as a kind of functional filler, can enhance comprehensive properties of superabsorbent composite and reduce the product cost significantly. Copyright © 2005 John Wiley & Sons, Ltd.
Article
In this work, we were interested in the study of the kinetic behavior of the reaction of drying soil representing the Marrakesh region (south of Morocco) in the presence of an superabsorbent polymer. The presence of a polymer in the soil diminished the kinetic drying of the soil, which will have as an application a reduction in water loss in the process of irrigation. The presence of a polymer in the soil enables a complete modification of the kinetic regimes controlling the soil-drying kinetic. We also realized the first study of the behavior of certain selected plants in the melange of a soil and a polymer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 234–243, 2002
Article
Crosslinked sodium polyacrylate was prepared by solution polymerization with N,N-methylene-bisacrylamide (bisAM) as crosslinking agent; it was subsequently surface-crosslinked by ethylene glycol diglycidyl ether (EGDE) and then was modified with inorganic salt to obtain a superabsorbent with water absorbency in 0.9 wt % NaCl aqueous solution at atmosphere and applied pressure (P ≈ 2 × 103 Pa) of 55 and 20 g.g−1, respectively. Moreover, it also had excellent hydrogel strength. The effects of reaction temperature, reaction time, neutralization degree (ND) of acrylic acid, amount of initiator, crosslinking agent, and surface-crosslinking agent, mass ratio of inorganic salt to initial superabsorbent, molar ratio of sodium aluminate (NaAlO2) to potassium dihydrogen hyphosphate (KH2PO4) on water absorbency (WA) in 0.9 wt % NaCl aqueous, and the hydrogel modulus were investigated and optimized. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2532–2541, 2004
Article
Acrylamide/maleic acid hydrogels in the form of rods were prepared by γ-irradiating ternary mixtures of acrylamide–maleic acid–water with 2.00–5.71 kGy γ-rays. The influence of dose and relative content of maleic acid on the spectroscopic, thermal and mechanical properties, swelling properties, diffusional behavior of water and diffusion coefficients of hydrogel systems are examined. Acrylamide/maleic acid hydrogels were swelled in the range of 1000–2800%, While polyacrylamide hydrogels were swelled in the range of 650–700%. Water diffusion to hydrogels in non-Fickian type diffusion. The diffusion coefficients varied from 4.5 × 10−2 to 12.2 × 10−7 cm2 sec−1.
Article
About 40–70% of the applied urea fertilizer is lost to the environment, causing serious pollution. Controlled-release technology is useful in increasing the efficiency of fertilizer urea as well as in checking environment pollution. Four laboratory-level controlled-release urea fertilizers were formulated based on polymers which are soil conditioners and then evaluated for their slow-release property. Urea was coated with the copolymer of acrylamide and divinylbenzene/N,N′-methylenebisacrylamide /tetraethyleneglycol diacrylate or pentaerythritol triacrylate and sealant materials (wax and polystyrene). Urea coated with co-polymer of acrylamide-tetraethyleneglycol diacrylate was found to be having a better slow-release property among the systems prepared. © 1996 John Wiley & Sons, Inc.
Article
A novel multifunctional superabsorbent composite from acrylic acid (AA), acrylamide (AM), sodium humate (SH) and attapulgite (APT), PAA-AM/SH/APT, was synthesized by aqueous solution polymerization, using N,N′-methylenebisacrylamide (MBA) as a crosslinker and ammonium persulfate (APS) as an initiator. In this paper, not only the effects of the ratio of AA to AM, SH and APT content on the saturated water absorbency, but also various swelling behaviors of the composite were systematically investigated. The results show that comprehensive performances of the superabsorbent are improved by introducing functional components into a poly(acrylic acid-acrylamide) (PAA-AM) network. Functionality of the composite in practice was also investigated by studying the release of SH and by growing Elymus dahuricus Turcz (a kind of grass) plants in soil with and without using the superabsorbent composite. The roots and stems of Elymus dahuricus Turcz were found to be sturdier compared with the plants grown without the superabsorbent composite. Copyright © 2005 John Wiley & Sons, Ltd.
Article
A salt-resistant superabsorbent, poly(acrylamide-co-acrylic acid) was synthesized from solution polymerization. To improve the properties of swollen hydrogel such as strength, resilience and dispersion, the copolymer was surface-crosslinked with ethylene glycol diglycidyl ether, and then the surface-crosslinked copolymer was blended with aluminum sulphate (Al2(SO4)3) together with sodium carbonate (Na2CO3) to obtain the aim sample. The factors that influenced the aim sample’s properties were investigated, and the optimum conditions were obtained as follows: the molar ratios of sodium hydroxide (NaOH) to acrylic acid, acrylamide to acrylic acid, initiator [denoted with hydrogen peroxide (H2O2)] to acrylic acid, and ethylene glycol diglycidyl ether to acrylic acid were 65–70%, 30%, (7–11) × 10−5, and (2.5–3.5) × 10−4, respectively, the mass ratio of Al2(SO4)3 to crosslinked copolymer was 4.25% and the reaction time was 0.5–2 h. The water absorbency of the sample prepared at the above conditions in 0.9 wt% NaCl aqueous solution under certain load (P ≈ 2 × 103 Pa) and at atmosphere pressure were 17 and 60 g g−1, respectively. Moreover, excellent strength, resilience and dispersion could be shown by this sample.
Article
Paraffin and polyethylene waxes were found to be efficient as controlled delivery systems for six different commercial-grade fertilizers. These fertilizers are monoammonium phosphate, diammonium phosphate, NP, NPK-4, and NPK-14 grades, and granular triple superphosphate fertilizers. Dissolution tests were performed for matrix-type formulations in order to determine the influence of waxes on the fertilizers release rate. Three different diffusion release formulas were tested for describing the release rate of the different fertilizers. The release times were at least doubled for all of the fertilizers while using either paraffin wax or polyethylene wax. The polyethylene wax gives longer release times than the paraffin wax.
Article
Polyacrylate superabsorbents were prepared by in situ aqueous solution polymerization in a polyethylene bag, which was submerged in a water bath. The influence of the initiator content, bath temperature, isopropanol content, initial monomer concentration, and crosslinker content (Cc) on water absorbency (Q) were investigated. The temperature change of the monomer mixture during polymerization was also analyzed. Increase of the chain ends in networks resulting from decrease of the molecular weight in free-radical polymerization causes an increase of the water absorbency of superabsorbents and also reduces the crosslinking efficiency. The results are in conformity with the classical network theory. An empirical relation of Q = 2.45 Cc−0.600 was obtained and the validity of Flory's swelling equation was confirmed indirectly. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 808–814, 2000
Article
This article reviews research on the use of reactive polymers in one of the important areas of international needs for health, nutrition, environmental pollution control and economic development. Controlled release polymers could reduce pollution and other side effects accompanying the use of conventional agrochemicals. Polymers may also enhance the conservation of the water in sandy soils and allow the release of fertilizer components by degradation of the polymer backbone.
Article
Encapsulation of fertilizers in polymeric coatings is a method used to reduce fertilizer losses and to minimize environmental pollution. Polysulfone was used for a coating preparation for soluble NPK granular fertilizer in controlled-release fertilizer formulations. The coatings were formed by the phase inversion technique (wet method). The influence of the polymer concentration in the film-forming solution on the physical properties of the coatings was examined. The coating structure controls the diffusion of the elements from the interior of the fertilizer granule. It was experimentally confirmed that the use of polysulfone as a coating for a soluble fertilizer decreases the release rate of components. Moreover, the release rate of nutrients from coated granules decreases with the decrease of the coating porosity. In the case of coating with 38.5% porosity, prepared from 13.5% polymer solution after 5 h of test, 100% of NH(4)(+) was released, whereas only 19.0% of NH(4)(+) was released after 5 h for the coating with 11% porosity. In addition, coating of fertilizers leads to improvement of handling properties, and the crushing strength of all coated fertilizers was an average 40% higher than that for uncoated NPK fertilizer.
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