Application of nanocomposite hydrogels in the controlled release of fertilizers

Application of nanocomposite hydrogels in the controlled release of fertilizers
A. Bortolin1,3, F. A. Aouada1,2, L. H. C. Mattoso1, C. Ribeiro1 LNNA, Embrapa – CNPDIA, São Carlos, SP, Brazil IQ, State University of São Paulo, Araraquara, SP, Brazil 3 DQ, Federal University of Sao Carlos, São Carlos, SP, Brazil
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Nitrogen is an essential component for soil fertility, and amongst the available commercial options, one of the most economically viable is urea, CO(NH2)2. However, this compound has its efficiency severally reduced by volatilization and leaching in soils [1]. An alternative to solve this problem is the application of urea mixed or incorporated into nanocomposite hydrogels structures, to gain a controlled release behavior. Thus, the present study aimed to investigate the controlled release of urea from biodegradable nanocomposite hydrogels based on polyacrylamide (PAAm), methylcellulose (MC) and montmorillonite (MMT). In addition, the structural and mechanical properties of these hydrogels were also investigated. The hydrogels were synthesized with the same amount of PAAm and MC, but the MMT concentrations varied from 0 to 50% (w/w). The mechanical properties were obtained using Universal Testing Machine Mechanical - EMIC based on the procedure described in ASTM D638M-91 method utilizing the compression tests [2]. Measures of sorption and desorption urea nutrient were quantified using a UV-VIS spectrophotometer, according to the methodology proposed by With et al [3]. The results indicated that the presence of MMT causes a significant improvement of mechanical properties. This trend is related to the cross interactions formed between the MMT layers and the polymeric chains (PAAm and MC). These interactions cause reduction of swelling degree, but improve mechanic resistance. The diffractogram of pure clay showed an intense peak in X-Ray diffraction at 2 θ = 6.56º, corresponding to an interlayer distance d001 = 1.35 nm. In the hydrogels with 6.25,