Nanocomposite PAAm/Methyl Cellulose/Montmorillonite Hydrogel: Evidence of Synergistic Effects for the Slow Release of Fertilizers

Abstract

In this work, we synthesized a novel series of hydrogels composed of polyacrylamide (PAAm), methylcellulose (MC), and calcic montmorillonite (MMt) appropriate for the controlled release of fertilizers, where the components presented a synergistic effect, giving very high fertilizer loading in their structure. The synthesized hydrogel was characterized in relation to morphological, hydrophilic, spectroscopic, structural, thermal, and kinetic properties. After those characterizations, the application potential was verified through sorption and desorption studies of a nitrogenated fertilizer, urea (CO(NH2)2). The swelling degree results showed that the clay loading considerably reduces the water absorption capability; however, the hydrolysis process favored the urea adsorption in the hydrogel nanocomposites, increasing the load content according to the increase of the clay mass. The FTIR spectra indicated that there was incorporation of the clay with the polymeric matrix of the hydrogel and that incorporation increased the water absorption speed (indicated by the kinetic constant k). By an X-ray diffraction technique, good nanodispersion (intercalation) and exfoliation of the clay platelets in the hydrogel matrix were observed. Furthermore, the presence of the montmorillonite in the hydrogel caused the system to liberate the nutrient in a more controlled manner than that with the neat hydrogel in different pH ranges. In conclusion, excellent results were obtained for the controlled desorption of urea, highlighting the hydrolyzed hydrogels containing 50% calcic montmorillonite. This system presented the best desorption results, releasing larger amounts of nutrient and almost 200 times slower than pure urea, i.e., without hydrogel. The total values of nutrients present in the system show that this material is potentially viable for application in agriculture as a nutrient carrier vehicle.

Polysaccharides as safer release systems for agrochemicals

“…The investigation of the fertilizer release mechanism from hydrogel composite indicated that in this system the fertilizer nutrients release followed a Fickian diffusion type transport mechanism. Similar water-retaining and controlled-release fertilizers formulations have been reported in case of starch-based (Zhong et al 2013) and methyl cellulose-based (Bortolin et al 2013) formulations. Super absorbent polymer (SAP) in three levels, 0.15, 0.3, and 0.45 % have been mixed with sandy loam soil.…”

Controlled release of nitrogen‐source fertilizers by natural‐oil‐based poly(urethane) coatings: The kinetic aspects of urea release

“…This showed that the castor oil PU based coatings were better able to retain/release macronutrients. These comparisons between the curves and the release behavior were interpreted from a model modified from that suggested by Peppas to obtain the release process kinetic parameters 26 :…”

Synthesis and characterization of zeolite based nano–composite: An environment friendly slow release fertilizer

“…WA [52], SR [53], EWC [29] are essential features for the SRF. The results of experiment for NZ and ZNC for all these three parameters are 49, 63%; 3.28, 3.53 g/g and 76.63, 77.92%, respectively.…”