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Agricultural production is influenced by the water content in the soil and availability of fertilizers. Thus, superabsorbent hydrogels, based on polyacrylamide, natural cashew tree gum (CG) and potassium hydrogen phosphate (PHP), as fertilizer and water releaser were developed. The structure, morphology, thermal stability and chemical composition of samples of polyacrylamide and cashew tree gum hydrogels with the presence of fertilizer (HCGP) and without fertilizer (HCG) were investigated, using X-ray diffractometry (XRD), Fourier Transformed Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA/DTG) and Energy Dispersive Spectroscopy (EDS). Swelling/reswelling tests, textural analysis, effect of pH, release of nutrients and kinetics were determined; the ecotoxicity of the hydrogels was investigated by the Artemia salina test. The results showed that PHP incorporation in the hydrogel favored the crosslinking of chains. This increased the thermal stability in HCGP but decreased the hardness and adhesion properties. The HCGP demonstrated good swelling capacity (~15,000 times) and an excellent potential for reuse after fifty-five consecutive cycles. The swelling was favored in an alkaline pH due to the ionization of hydrophilic groups. The sustained release of phosphorus in HCGP was described by the Korsmeyer–Peppas model, and Fickian diffusion is the main fertilizer release mechanism. Finally, the hydrogels do not demonstrate toxicity, and HCGP has potential for application in agriculture.

O biodiesel é um biocombustível de fontes renováveis com grande potencial na substituição do diesel no Brasil. Entretanto para sua purificação é utilizado água e isso gera grandes problemas ambientais. Umas das formas de minimizar esses problemas são a recuperação e o reaproveitamento das águas de lavagem para descarte, processo este, que é feito através do uso de argilas, silicatos lamelares, que apresentam grandes potencialidades e aplicações tecnológicas quando modificadas quimicamente. Diante disso, foi realizada uma prospecção tecnológica em busca de artigos e patentes com a finalidade de fazer um estudo sobre a aplicação da argila do tipo vermiculita na adsorção de contaminantes oleosos provenientes da água de lavagem do biodiesel. De acordo com a pesquisa realizada no INPI, EPO e USPTO para a busca de patentes e na base de artigos não foram encontrados resultados que evidenciem o uso da vermiculita para a aplicação descrita, embora muitas outras aplicações já tenham sido investigadas.Palavras chave: Biodiesel. Adsorção. Vermiculita.

Cactus pears face challenges due to global climate change, which is leading to in-depth research to monitor and increase their water activity. The objective of this study was to evaluate the use of the natural test hydrogel (TH) from Orbignya phalerata fibre as nutrients and water for growing cactus pear genotypes (“Baiana” and “Doce” [Nopalea cochenillifera], ‘Gigante’ [Opuntia fícus-indica], and “Mexican Elephant Ear” [Opuntia stricta]) compared to the use of commercial hydrogel (CH), which is based on polymers composed of polyacrylamide, and a treatment without the use of hydrogel (WH). A completely randomized design was used, in a factorial scheme (4 × 3), with four genotypes of cactus pear and three forms of hydration, with five replications. The number and area of cladode was greatest (p < 0.01) in plants with CH and TH irrigation-fertilization in the ‘Doce’ cactus genotype. The dry biomass of the cladode and root in the ‘Gigante’ cactus genotype was greatest (p < 0.01) in the treatments with CH and TH irrigation-fertilisation. The ‘Baiana’, ‘Doce’, and ‘Gigante’ cactus genotypes exhibited more (p < 0.01) dry matter content with the TH irrigation-fertilisation. The highest (p < 0.01) neutral detergent fibre content was observed in the ‘Baiana’ and ‘Doce’ cactus genotypes when irrigation occurred with WH treatment, and the highest acid detergent fibre content in the ‘Gigante’ genotype. The copolymerized natural fibre from the mesocarp of Orbignya phalerata (babassu fruit) induced a better growth and chemical composition of cactus pear genotypes than the hydrogel based on polymers composed of polyacrylamide.

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