Preparation of superabsorbent slow release nitrogen fertilizer by inverse suspension polymerization

Abstract

A superabsorbent, slow release nitrogen fertilizer (SSRNF) was prepared by inverse suspension polymerization of partially neutralized acrylic acid using N,N′‐methylene bisacrylamide as a crosslinker and ammonium persulfate as an initiator in the presence of urea. The polymer was characterized using infrared spectral analysis, and network structural parameters such as molecular weight between crosslinks (Mc) and crosslink density (q) were calculated. The effects of reaction conditions, such as reaction time, reaction temperature, initiator, crosslinker and the degree of neutralization of acrylic acid, on water absorbency were investigated. The nitrogen content of SSRNF synthesized under optimal conditions was 22.7%, and the water absorbencies were about 965 g g−1 in distilled water and 185 g g−1 in tap water. The nitrogen slow release behaviors of the SSRNF in water and water retention capacity of soil with the SSRNF were also investigated. A possible slow release mechanism was proposed and the release rate constant K and the diffusion coefficient D of urea in the hydrogel was calculated. The results showed that the product not only had good slow release properties but also excellent soil moisture preservation capacity, which could effectively improve the utilization of fertilizer and water resources simultaneously. Therefore, the SSRNF is a multifunctional water managing material, which would find application in agriculture and horticulture, especially in drought‐prone areas where the availability of water is limited. Copyright © 2006 Society of Chemical Industry

Encapsulated Urea-Kaolinite Nanocomposite for Controlled Release Fertilizer Formulations

“…In point of fact, urea is the most widely used nitrogen fertilizer in most parts of east Africa because of its high nitrogen (N) content (46%) and comparatively low cost of production; however, due to surface runoff, leaching, and vaporization, the utilization efficiency or plant uptake of urea is generally below 50% [1]. In fact, it is associated with up to 60 to 70% loss of the nitrogen being applied and contributes to greenhouse gases (GHG) emissions and water pollution [2] which in turn causes adverse effects during seed germination, seedling growth, and early plant growth in soil due to urea itself, to biuret and other impurities in urea fertilizers, and to products formed by hydrolysis or other transformations of urea in the soil [3,4].…”

“…Control over the release pattern depends on the thickness of the coatings within the formulation [8]. Precisely, CRFs exhibit superior features over traditional forms, such as decreased rate of nutrient losses from the soil by rain or irrigation water, sustained supply of nutrition for a prolonged time, increased fertilizer use efficiency (FUE), reduced frequency of application, minimized potential negative effects associated with overdosage, and reduced toxicity, thus making CRFs' manufacturing and usage inevitable in the agricultural revolution era [1]. This paper describes the application of both intercalation reactions and encapsulation mechanisms to prepare urea based CRF by using Pugu kaolinite and gum arabic biopolymer.…”

Meticulous Overview on the Controlled Release Fertilizers

“…According to Liu et al [22], intercalation of nutrients into the excipients is normally achieved by two methods. In the first method, the compound to be loaded is added to the reaction mixture and polymerized in situ whereby the compound is entrapped within the gel matrix, whereas in the second method, the dry gel is allowed to swell in the compound solution and after equilibrium swelling, the gel is dried and the device is obtained.…”

“…In addition to that, surfactants such as sodium octadecyl phosphate and sometimes a dispersion medium such as cyclohexane (which is normally used to disperse surfactant molecules) are also known in the release formulation practices [22]. In fact, different surfactants have been used in CRFs designs and the commonly used ones include nonionic surfactant molecules [90].…”

Polymer in Agriculture: a Review

“…Du et al studied the differential release rate and patterns of nitrate, ammonium, potassium and phosphate from two polyurethane-coated controlled release fertilizer (CRFs) and the effect of the temperature, the water content and type of release medium on it [36] . A superabsorbent with slow release nitrogen fertilizer (SSRNF) was prepared by inverse suspension polymerization of partially neutralized acrylic acid using N,N'-methylene bisacrylamide as a crosslinker and ammonium persulfate as an initiator in the presence of urea [37] . All these superabsorbent polymers showed excellent water absorbency, water retention, moisture preservation besides its slow-release properties and generally the water absorbency is strongly influenced by the amount of initiator, crosslinker, and the degree of neutralization of acrylic acid.…”