Urea Release Research Articles

Coating of urea granules by in situ polymerization in fluidized bed reactors

Abstract The main objective of the present work is to produce and characterize urea granules coated with polymers prepared with aqueous solutions of acrylic acid and glycerol. Both coating and drying of urea granules were performed in a fluidized bed reactor. Fourier transform infrared spectroscopy analyses indicated the presence of poly(acrylic acid) and acrylic acid / glycerol copolymers on the granule coating and the formation of chemical bonds between urea and the polymer coating. Scanning electron microscopy images showed that the original and coated urea granules presented different characteristics, reinforcing the idea that coating occurs in the fluidized bed. Finally, rates of urea release showed that the coated granules presented slightly slower rates of urea dissolution in water due to the presence of the coating layer. Therefore, it is shown that it is possible to produce coated urea granules through in-situ polymerization onto the granule surface using a fluidized bed.

Biochemical effects of banding limit the benefits of nitrification inhibition and controlled-release technology in the fertosphere of high N-input systems

Enhanced efficiency fertilisers (EEFs) may have an important role in improving nitrogen (N) use efficiency in agricultural systems. The performance of EEFs when applied by broadcasting and incorporation is well documented; however, little information is available for sub-surface banded N-fertiliser. This study aimed to determine the effectiveness of EEFs within the fertosphere in several soils. This was determined by: (i) establishing the key chemical effects and N-transformation activity within a urea band, and (ii) contrasting these findings with nitrification inhibitor (NI)-coated urea and a controlled-release polymer-coated urea (PCU). A 112-day incubation experiment was conducted with the EEFs band-applied in three contrasting soils with a history of sugarcane production. In standard urea and NI-urea treated soils, the pH within the fertosphere significantly increased to a maximum of ~pH 9.2–9.3. Alkaline conditions and high ammonium concentrations promoted elevated aqueous ammonia concentrations, resulting in complete nitrification inhibition. The PCU granules released ~40% of total urea content within 14 days, followed by subsequent release at significantly lower rates. The initial rapid urea release was attributed to damaged polymer coats, while close proximity of neighbouring granules within the band may have contributed to the subsequent slower release phase through reduced concentration gradients and restricted diffusion from granules. Variation between soils suggests that soil properties such as clay content and pH buffer capacity may influence urea hydrolysis, but not nitrification. These results suggest that both NI and controlled-release technology may not have the expected impacts on N transformations and availability when applied in a concentrated band.

Controlled-release urea encapsulated by ethyl cellulose/butyl acrylate/vinyl acetate hybrid latex

Abstract Fertilizer encapsulation through polymer membranes can reduce fertilizer losses and minimize environmental pollution. In this paper, an emulsion of ethyl cellulose (EC)/vinyl acetate (VAc)/butyl acrylate (BA) was successfully prepared by pre-emulsified semi-continuous seed emulsion polymerization. EC/BA/VAc films showed biodegradability. The influence of the EC content on the properties of EC/BA/VAc films was also investigated by DSC, a water absorbency analysis, etc. Controlled-release urea encapsulated by EC/BA/VAc latex was prepared in a film coating machine and conformed to the standards for slow-release fertilizers of the Committee of European Normalization. The release of urea from controlled-release urea encapsulated by EC/BA/VAc latex containing 0%, 5%, 10%, and 15% EC was 75.1%, 65.8%, 70.1% and 84.1%, respectively, after 42 days, and controlled-release urea encapsulated by EC/BA/VAc latex (5% EC) had the best controlled-release ability. Therefore, controlled-release urea encapsulated by EC/BA/VAc latex has many potential applications in agricultural industry.

Slow release urea fertilizer synthesized through recrystallization of urea incorporating natural bentonite using various binders

Abstract In this study, various slow release urea fertilizers (SRUFs) were prepared by incorporation of urea into local natural bentonite with various binder i.e. corn starch and hydroxypropyl methylcellulose (HPMC). In the preparation, a binder was added to a mixture of natural bentonite and melted urea. Then, the admixture was put into a mould and extruded to obtain SRUF in the form of pellets. The SRUF was dried at 50 °C for 8 h before use. Urea desorption mechanisms of the SRUF was examined through static release experiments. The structural properties of SRUF was characterized through scanning electron microscopy with energy dispersive x-ray (SEM-EDX) analysis and Fourier-transform infrared spectroscopy (FTIR). It was found from static release experiments that the SRUFs more slowly released urea in water than conventional urea fertilizer. After 500 min of the experiment, the slowest release of urea was achieved by SRUF using corn starch. Meanwhile, conventional urea fertilizer completely released urea in water after less than 50 min. Release mechanisms of the SRUF using corn starch and SRUF using HPMC were anomalous transport and Fickian diffusion, respectively.

Microparticles from Wheat-Gluten Proteins Soluble in Ethanol by Nanoprecipitation: Preparation, Characterization, and Their Study as a Prolonged-Release Fertilizer

At present, the development of natural polymeric microparticles is carried out to obtain release systems. Prolonged-release systems are a potential solution to avoid nitrogen (N) losses in agricultural fields. The aim of this study was to develop microspheres from wheat-gluten proteins soluble in ethanol 70% (v/v), to ascertain their characterization, and to study their potential application in agricultural fields. Soluble-protein extraction was performed with 1600 mL of ethanol 70% (v/v). Likewise, ethanolic solutions with protein concentrations of 0.5%, 1%, and 2% (w/v) are classified as non-Newtonian fluids with pseudoplastic behavior. Using the nanoprecipitation method, it was possible to develop urea-loaded microspheres with a diameter ranging from 900 nm–1.7 μm. The Fourier transform infrared spectroscopy (FTIR) test exhibited interaction through hydrogen bonds between carbonyls and amino groups from the urea and proteins. Also, the thermogravimetric analysis (TGA) test demonstrated thermal stability at 130°C. The release experiment showed that the microspheres achieved equilibrium when 88% of the urea was released. Finally, according to the empirical model of Ritger and Peppas, urea release is carried out through Fickian diffusion. We conclude that the microspheres could be applied in the fields and with this improve agricultural practices. Also, they could reduce the potential environmental pollution and developing a sustainable agriculture.

The involvement of estrogen receptors α and β in the in vitro effects of 17β-estradiol on secretory profile of peritoneal macrophages from naturally menopausal female and middle-aged male rats.

The systemic and extra- gonadal levels of 17β-estradiol (E2) change during aging, and affect the expression of estrogen receptors (ERs) in the immune cells of both females and males. The age-related cessation of ovarian function in females, as well as the tissue-specific expression of enzyme aromatase (estrogen synthase which significantly rises with the advancing age) in both males and females, both determine the concentration of E2 to which immune cells may be exposed. The present study was set up to investigate the direct influence of E2 in vitro on the secretory profile of peritoneal macrophages from young and naturally menopausal female rats, and from young and middle-aged male rats. The involvement of receptor(s) responsible for mediating the effects of E2 in vitro was examined by use of antagonists specific for ERα or ERβ. Whereas in macrophages from young female rats E2 treatment diminished interleukin (IL)-1β secretion, it increased it in young males, and the middle-aged females. The in vitro E2 treatment increased tumor necrosis factor (TNF)-α release by macrophages from young rats of both sexes, while it increased macrophage IL-6 release independently of both sex and age. At the same time, E2 decreased hydrogen peroxide (H2O2) production in macrophages from females, and increased it in male rats of both ages, whereas it diminished nitric oxide (NO) release in all experimental groups. Inspite of the sex- and age-specific effects of E2 on macrophage urea release, E2 did not affect the NO/urea ratio in macrophages from female rats, and diminished it in macrophages from both young and middle-aged male rats. Independently of the sex and age, E2 stimulated the release of inflammatory cytokines predominantly via macrophage ERα, and inhibited the IL-1β release in young females via ERβ. In contrast, E2 increased macrophage H2O2 and urea production by activating ERβ, but diminished their release via ERα. Our study may contribute to better understanding of the complex role(s) that E2 may play in innate immunity during aging, and that are dependent of sex.

Carnauba wax as a wall material for urea microencapsulation

The high ureolytic activity of rumen microbiota is a concern when urea is used in ruminant feed, because it leads to fast urea conversion, resulting in possible intoxication and lower nitrogen utilization. This study intended to microencapsulate urea using carnauba wax to obtain slow-release systems in the rumen. The experiment was conducted in a randomized block design, arranged in a 3 × 2 factorial, with the urea encapsulated with carnauba wax in ratios of 1 : 2; 1 : 3, and 1 : 4 (UME 2; UME 3, and UME 4) and two particles sizes (small, PS ; and large, PL ). All formulations showed excellent properties, including inhibition of urea hygroscopicity. The formulation UME 2 exhibited the greatest yield (91.6%) and microencapsulation efficiency (99.6%) values, whereas the formulation UME 4 presented the greatest thermal stability (259.5 °C) and lowest moisture content (1.81%). The UME 2 formulation presented a slower release than the other UME formulations studied. The production of urea microspheres using carnauba wax was successful for all microencapsulated systems developed, evidencing the promising potential for use in ruminant animal diets. The UME 2 formulation with large particles is the most recommended because it permitted greater resistance to microbial attack, allowing a slower release of urea into the rumen, reducing the risk of intoxication or ruminal alkalosis. © 2018 Society of Chemical Industry.

Comportamento ingestivo de novilhas Nelore em pastejo no período seco suplementadas com sal mineral e tipos de ureia

In this study, the feeding behavior of Nellore heifers receiving supplements containing mineral salt, conventional urea and slow release urea during the grazing stage at Brachiaria brizantha-based pastures during the dry period of the year was evaluated. Fifty-six heifers with approximately 284.72 ± 27.48 kg of body weight were used, distributed in a completely randomized design with four different treatment types: mineral salt; Urea - supplementation with 8.18% conventional urea; Mixed urea - supplementation with 4.09% conventional urea and 4.39% slow release urea and slow urea - supplementation with 8.78% slow release urea. Animals supplemented with mineral salt had longer grazing times compared to those supplemented with mixed urea, slow urea and regular urea. The dry matter intake, neutral detergent fiber and total digestible nutrients presented a similar effect, with higher values for heifers consuming supplements containing regular urea and slow urea compared to those of mixed urea. However, when the efficiency of hourly intake was evaluated, the animals that received urea supplement were more efficient in relation to the other treatments. The number of grazing periods for heifers receiving slow urea supplementation was higher compared to heifers receiving salt and mixed urea. The duration of grazing and rumination periods was longer for heifers receiving salt supplementation and mixed urea than those receiving regular urea and slow urea. It is recommended to use supplements at the level of 0.3% of body weight for heifers receiving conventional urea.

Controlled‐release fertilizer based on poly(butylene succinate)/urea/clay and its effect on lettuce growth

ABSTRACTControlled‐release fertilizer is one of the most critical tools in agribusiness for decreasing environmental impacts. Thus, the development of bio‐based systems able to induce the slow release of fertilizers has become the focus of numerous researchers. In this sense, this work presents a slow‐release fertilizer prepared by melt mixing of poly(butylene succinate) filled with 30 wt % urea and 5 wt % montmorillonite clay. The obtained materials were characterized using FTIR, XRD, and SAXS. Also, the release of urea was investigated using gravimetric and spectrophotometric tests. Finally, a vegetable growth analysis was performed to evaluate the development of lettuce (Lactuca sativa L.). The best composite material can increase the diameter of the lettuce by 67%, whereas the conventional use of urea increased this diameter by 48%. Therefore, the presented materials are useful as fertilizer systems.

The Effect of Hyperbaric Oxygenation on the Circulation of Urea in Rats Following Experimental Partial Hepatectomy

Material and methods. The studies were performed on 75 white mature rats (females) weighing 180—220g. Partial hepatectomy was performed by resection of a part of the left lobe of the liver (15—20% of the organ weight). Hyperbaric oxygenation (HBO) was performed three times (3 ata, 50 min). The first, second and third sessions were performed 4—8 hours, 24 hours and 48 hours after the surgery, respectively. The urea level was determined in the tissues of visceral organs, as well as in arterial blood (aorta), portal blood, blood from renal and hepatic veins, bile from common bile duct, and in urine on the 1st, 4th and 11th days of posthyperoxic period (days 3, 7 and 14 post-surgery).Results. Activation of the urea incretion from the operated liver to the bloodstream under hyperoxic conditions was accompanied by increased urea concentration in the arterial blood and excretion from the body with urine that was facilitated by the elimination of a stimulating effect of PHE on the reabsorption of urea in the kidneys by the HBO procedure. At the same time, the production of urea in the renal tissue was activated and further released to the circulation through the renal vein. Stimulation of the liver and intestinal urea circulation by HBO was accompanied by the preservation of the stimulating effect of PHE on its accumulation in duodenum and colon tissues. In the thyroid gland, spleen, heart, and lungs of operated rats, HBO activated the transition of the «arterial» urea from the free form to the bound one. Termination of HBO normalized the urea concentration in the arterial blood by the 11th day of the posthyperoxic period whereas urea continued to be accumulated the heart, spleen, lungs, and intestine. A preserved increased release of urea from the operated liver into the bloodstream after HBO was accompanied by partial retention in the hepatocytes of urea delivered via bloodstreem through the portal vein. On the 11th day after HBO, the repeated hyperoxic activation of the liver and intestinal urea circulation occured, as well as HBO-restored stimulation of its production in the kidneys resulted in urea release into the renal vein and excretion with urea.Conclusion. HBO provides a correcting effect on alteration of circulating urea caused by PHE.

The Facile Modification of Polyacrylate Emulsion via Hexadecane to Enhance Controlled-release Profiles of Coated Urea

Development of controlled-release urea (CRU) has attracted research attention because of food scarcity problems and environmental concerns. To slow down the nutrient release of CRU coated with waterborne polyacrylate, conventional emulsion polymerization (CEP), conventional emulsion polymerization containing hexadecane (CEP + HD), and miniemulsion polymerization (MP) were carried out to discern the influence of polymerization technique and hexadecane on the properties of emulsions, films, and on the resultant nutrient release profiles of controlled-release urea. The addition of hexadecane improved water resistance, decreased the glass-transition temperature, and slowed down the nutrient release. CEP + HD was superior to MP in retarding nutrient release since the majority of HD was distributed in the exteriors of the particles of the former and interiors of the particles of the latter. Exterior HD improved water resistance more effectively, while interior HD reduced glass-transition temperature more significantly. Overall, our findings showed that incorporation of HD into polyacrylate emulsion produces excellent coatings that delay the release of urea. It has great potential application in controlled-release fertilizers coated with waterborne polymers.

Oil Biodegradation Systems Based on γ Irradiated Poly (Butylene Succinate)

The risks of environmental damage are inherent in oil activities, being a constant concern to our modern society. Among the remediation strategies, the biological one is safer and more inexpensive compared to physic‐chemicals approaches. Bioremediation can be enhanced using biodegradable polymers as coating materials of the nutrient release systems. However, some of these polymers can be improved using electromagnetic radiation, able to modify their properties, such as, molar mass, changing the materials physicochemical behavior. Thus, immobilizing urea in poly (butylene succinate) (PBS) matrix, producing a petroleum bioremediation tool was the primary goal in the paper herein. The composites were obtained by melting at 110 °C with subsequent application of gamma (γ) radiation at doses of 15, 25, 50, and 75 kGy. The obtained results allowed to infer that the increase of the γ radiation doses improved the immobilization, thus reducing the immediate urea release. Besides that, the preliminary biodegradation results showed that the highest rates of hydrocarbon reduction at the end of the analysis period were reached using the material irradiated at 25 kGy. These results are encouraging and proved that irradiated PBS‐urea systems could be used as oil spill disasters tool.

Preparation and Properties of a Double‐Coated Slow‐Release Urea Fertilizer with Poly(propylene carbonate), a Sodium Polyacrylate Hydroscopicity Resin and Sodium Alginate

AbstractA double‐coated slow‐release urea fertilizer was designed and successfully prepared. Its core was urea, and the shell was biodegradable poly(propylene carbonate) (PPC) derived from CO2 copolymer as the inner coating, and sodium polyacrylate hydroscopicity resin (SPHR) and sodium alginate (SA) as the outer coating. The effects of the molecular weight of PPC, the amount of SPHR and SA on the slow release behavior of urea were investigated. The experimental results indicated that the coating materials had a good slow‐release property for urea release. The urea slow‐release time can reach 500 min in water. The double‐coated slow‐release urea fertilizer has water‐retention capacity. The product has the wild applications in agriculture.

Lignin linked to slow biodegradability of urea-crosslinked starch in an anaerobic soil environment

Abstract For slowing fast solubility and increasing the period of urea’s release in soil, urea-crosslinked starch (UcS) was prepared and applied as a slow release fertilizer. The higher environmental biodegradability of UcS is a major drawback for slow release of urea yet it provides an important challenge for large scale production and application on anaerobic farm lands. Hence, in order to reduce biodegradability of UcS, impregnation of UcS with 5–20 wt% of lignin is proposed. Lignin impregnated UcS was buried for a maximum period of 28–64 days under a constructed anaerobic soil environment. Hill’s model predicted that mineralization of UcS by lignin would be reduced by 5.48%. Microbial growth on UcS was inhibited by lignin at the rate of 0.84 day−1. The α-amylase activity was retarded in response to UcS impregnation with lignin at the rate of 810.94 μg h−1 g−1 soil. Lignin also showed improvement in half-life of UcS up to 0.51 days. This work concluded that lignin impregnation was an efficient approach for improvement of UcS through increasing resistance against natural biodegraders.

Bead Gel sebagai Controlled Release Urea : Pengaruh Konsentrasi Crosslinker Glutaraldehid

The structure of carboxymethylcellulose (CMC)-carrageenan mixture was chemically modified using glutaraldehyde in order to prepare bead hydrogel form. The obtained beads gel were applied to control the urea release rate. The aim of this research was to compose mathematical model describing the mass transfer rate of urea release and determine the effect of concentration glutaraldehid on the bead gel endurance in water as medium release. The bead gels (CMC/carrageenan mass ratio =1 and 2) were physic crosslinked with CaCl 2 solution and then followed by chemically crosslinked with glutaraldehyde solution (4% & 1%) using immersion method and thermal curing at 110 o C for 25 minutes. After being washed and dried, the beads gel were immersed in urea solution. The rate release of urea from dried crosslinked beads gel in water was determined by measuring the concentration of urea in various time of immersion. The result showed that the mathematical model arranged could describe the mass transfer rate of urea release. The higher glutaraldehid concentration on beads gel, the higher beads gel endurance in water.

EFFECT OF FLUIDIZED-BED PROCESS VARIABLES ON CONTROLLED-RELEASE OF NITROGEN AND COATING

Abstract Pristine urea is lost due to ammonia volatilization and leaching causing toxic emissions and eutrophication. Controlled-release urea is employed as an abatement strategy. Most of the synthetic polymers used to produce controlled-release urea are non-biodegradable and expensive. To offset this problem, modified-starch biopolymer is used as coating material to produce controlled-release urea in fluidized bed. The effect of different process variables is studied on release characteristics and coating uniformity of coated urea. The product has better release characteristics. The statistical analysis reveals that fluidizing gas temperature and coating time are the most influential variables. The nutrient release time increases with increase in coating time and decreases with increase in fluidizing gas temperature beyond a certain limit. Coating uniformity, significant thickness and film integrity are required for promising release characteristics. Urea release followed non-Fickian diffusion and Case-II transport. This study can help produce green fertilizer at bigger scale.

Preparation and characterization natural rubber-urea-tablets coated by chitosan

Excessive urea leaching causes water pollution and fabricating slow release coated urea is usually performed at high temperature or using synthetic polymers and toxic solvent which might generate environmental pollution. This study aims to formulate “green process” of urea slow release tablets and characterize urea slow release tablets. The formula was composed of rice husk ash, urea, and liquid natural rubber (LNR). Several proportions were studied and characterized based on the stability in water and urea leaching. The immobilizing urea was carried in two models; core-shell and mixed model composite either coating or uncoated with chitosan. The slow release urea tablets were stable in water without decomposition at least 9 days of incubation times depending on LNR content but at least 15 mL of LNR was required to obtain stable tablets. Urea leaching from core-shell tablet was 0.045% and 0.75% for mixed model tablet in 10 days incubation times. Chitosan coating did not affect significantly on urea leaching for core-shell model but it caused urea release faster in mixed model after 12 days incubation times. Low LNR and chitosan coating retarded fungus growth on the urea slow release tablet.

Preparation of a low-cost and eco-friendly superabsorbent composite based on wheat bran and laterite for potential application in Chinese herbal medicine growth.

A low-cost and eco-friendly superabsorbent composite is prepared through the free-radical graft co-polymerization of wheat bran (WB), acrylic acid (AA) and laterite (LA) in an aqueous solution. Elemental map, scanning electron microscopy and Fourier transform infrared spectra revealed that the LA evenly distributed in the superabsorbent composite and wheat bran-g-poly(acrylic acid)/laterite (WB-g-PAA/LA) formed successfully. Thermogravimetric analysis confirmed that the WB-g-PAA/LA had high thermal stability. Furthermore, the properties of the WB-g-PAA/LA, such as swelling in saline solutions and degradation, are also assessed. The final WB-g-PAA/LA (5 wt%) superabsorbent composite attained an optimum water absorbency of 1425 g g−1 in distilled water and 72 g g−1 in 0.9 wt% NaCl solution. The water absorbency of WB-g-PAA/LA (10 wt%) is even greater than that of the WB-g-PAA. Moreover, the water-retention capacity of WB-g-PAA/LA (5 wt%) is high, and the water-retention process followed a zero-order reaction. The reaction rate constant is 8.2428 × 105 exp(−Ea/RT) and the apparent activation energy (Ea) is 35.11 kJ mol−1. Furthermore, WB-g-PAA/LA (5 wt%) may regulate the release of urea, indicating that the superabsorbent composite could provide a promising application as a urea fertilizer carrier. Additionally, it increased the germination and growth rates of Glycyrrhiza uralensis Fisch, suggesting it could influence the growth of Chinese herbal medicine.

Polyvinyl alcohol based hydrogels for urea release and Fe(III) uptake from soil medium

Poly(vinyl alcohol) (PVA) based biocompatible, non-toxic and environmentally benign polymeric hydrogels were synthesized by cross-linking with poly(ethylene glycol) (PEG) and sodium sulfate. Further modification was carried out with incorporation of urea into the hydrogel at the time of synthesis. The prepared gels were characterized by scanning electron microscopy (SEM), Fourier Transform Infra Red (FTIR) spectroscopy, nitrogen adsorption desorption isotherms and swelling. Prediction of the possibility of using these hydrogel beads in agriculture fields is the main objective of this work. In this particular article, the release of urea from urea extracted and urea incorporated beads in the soil medium was studied along with inspection of Fe(III) uptake from the same soil sample. The gel matrices were found as potential candidates for slow release of urea and high sorption of Fe(III) from soil sample. Thus the problem of frequent application of urea containing fertilizer to the agricultural field can be overcome and at the same time the trouble for high concentration of Fe(III) in the soil can also be diminished.

Nanoscaled free volume holes and slow release of urea for poly(vinyl alcohol)/urea composite films

Nanoscaled free volume holes and slow release of urea for poly(vinyl alcohol)/urea composite films