Browsing by Author "Costa, Mirian Cristina Gomes"

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    Durability indicatives of hydrogel for agricultural and forestry use in saline conditions
    (Elsevier, 2021-09-06) Nascimento, Carla Danielle Vasconcelos do; Andrade Feitosa, Judith Pessoa de; Simmons, Robert; Dias, Carlos Tadeu dos Santos; Nascimento, Ícaro Vasconcelos do; Mota, Jaedson Cláudio Anunciato; Costa, Mirian Cristina Gomes
    This research tested the hypothesis that the interaction between time and salinity reduces the water absorption potential of a hydrogel – Poly (Acrylamide-co-Potassium Acrylate) and influence the degradation of residual acrylamide monomer. The experimental design was completely randomized split-plot with four replications. The treatments were time periods (30, 60, 90 and 120 days) and levels of salinity of the hydrating solution (distilled water = 0.003, 0.5; 1.5; 3.0 and 6.0 dS m−1). Swelling, hydrogel composition, and residual acrylamide monomer concentration were evaluated. The hydrogel showed lowest water absorption potential (8.1 g g−1) in a saline solution of 4.20 dS m−1 after 120 days. The C/N ratio of the hydrogel increased by up to 47% in a hydrating solution with an EC of 4.4 dS m−1 at 120 days. Additionally, there was an observed shift in the wavelength of methylene, amide, and acrylate bands, that indicates degradation. Residual acrylamide monomer concentration was <0.5 mg g−1 (safe for agricultural use). After 120 days up to 85% of the residual acrylamide monomer was degraded. About the water absorption potential, the results suggest that under semi-arid conditions hydrogel durability for forestry and crops applications may be impaired by the salinity of the hydrating solution.
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    Potential of superabsorbent hydrogels to improve agriculture under abiotic stresses
    (Elsevier, 2021-03-23) Nascimento, Carla Danielle Vasconcelos; Simmons, Robert W.; Feitosa, Judith Pessoa de Andrade; Dias, Carlos Tadeu dos Santos; Costa, Mirian Cristina Gomes
    Hydrogels are a promising management option to increase the efficiency of water use in agriculture in arid and semi-arid regions. However, abiotic factors may affect hydrogel efficacy. The effect of abiotic stress on the swelling and residual acrylamide in hydrogels was evaluated. The treatments were three hydrogels (A, B and C), four temperatures (20, 30, 40 and 65 °C) and two salinities (0.003 and 3.0 dS m−1). The swelling degree and the residual acrylamide concentration of the hydrogels were measured. Data were analyzed with univariate and multivariate statistics. The swelling order of hydrogels under low salinity was A>C>B; at high salinity was B>A>C. All hydrogels presented swelling reduction at high salinity, with swelling reductions in A and C of 97% and 85%, respectively, while B presented a swelling reduction of 37% at 20 °C and greater than 89% at higher temperatures. Hydrogel B achieved good swelling under saline conditions, but only at 20 °C. Thus, the temperature tolerance of this hydrogel should be improved so it can be used to improve water use efficiency in regions with high temperatures and salinity levels. Residual acrylamide levels of hydrogels decreased by 95% over 30 days, being safe for agricultural applications