Superabsorbent hydrogels based on N,N-dimethylacrylamide and maleic acid for applications in agriculture as water purifier and nitrogen carrier

Abstract

To reduce water pollution caused by fertilizers in agricultural irrigation, highly swelling crosslinked hydrogels (p(DMAAm-co-MA) or DM 1 ) based on N,Ndimethylacrylamide (DMAAm) and maleic acid (MA) were prepared using a chemical initiator with the redox polymerization technique. Negative and positive surface modifications of DM 1 were achieved using hydrochloric acid (HCl) (p(DMAAm-co-MA)/HCl or DM 2 ) and sodium hydroxide (NaOH) (p(DMAAm-co-MA)/NaOH or DM 3 ), respectively. The synthesized hydrogels were named DM 1 , DM 2 and DM 3 , respectively. The swelling properties, urea sorption and urea release kinetics of synthesized hydrogels were analyzed in deionized water at different pHs. The sorption isotherms and sorption parameters were investigated thoroughly for all hydrogels and the Langmuir (L) isotherm showed the best fit. In order to examine the urea release mechanism from all hydrogels, four mathematical models of zero-order kinetic model (Z-O), first-order kinetic model (F-O), Higuchi (H) and the Korsmeyer-Peppas power law (K-P) were studied to fit the experimental data. The hydrogels exhibited swelling and releasing properties that were highly dependent on their functional groups and the ionic forces in the medium. Cumulative urea release values for DM 1 , DM 2 and DM 3 were calculated as 100% at pH 10, 100% at pH 8 and 100% at pH 8 within 48, 41 and 18 h, respectively. It was confirmed by experimental studies that the prepared hydrogels and their derivatives can be used as carriers for fertilizers, particularly urea, as well as controlled water release sources. As a result, the use of the synthesized hydrogels to prevent contamination of water resources with agricultural products and to provide a nitrogen source that plants require comprise the innovative and original aspect of the article.

Impact of Modifications from Potassium Hydroxide on Porous Semi-IPN Hydrogel Properties and Its Application in Cultivation

“…In addition, DMA-based hydrogels possess antioxidant and antibacterial properties, which is a very important premise for finding their versatile applications [36,37]. To the best of our knowledge, this is the first time the linear polymers PAM, DMA, and MA were combined in a semi-IPN hydrogel modified with KOH and applied as a phosphorous fertilizer carrier compared to previous conventional hydrogels [26,38].…”

“…On the other hand, conventional hydrogels have several disadvantages, such as brittleness, low swelling ratios, uncontrolled absorption and release, and poor mechanical properties that hinder their reuse [25]. In comparison with the PAM-based hydrogel, the swelling ratios of the PDMA-based hydrogel were usually much lower because the chemical structure of the DMA monomer has two hydrophobic methyl -CH 3 groups [26,27]. In our previous reports, semi-IPN hydrogels were synthesized and solved the disadvantages of conventional hydrogels [8,11,28].…”

“…It was reported that, when modified in a KOH solution, a porous structure was created in the hydrogel. Modified hydrogels have been used for specialized applications, such as tissue engineering scaffolds, carriers of solvents, nutrients, and other agents [26,32].…”

Highly efficient electrocatalytic oxidation of furfural to maleic acid over MOF-derived MnCeOx

“…[6][7][8][9] In this regard, partial oxidation of furfural to produce maleic acid (MA) has attracted much attention for a long time [10][11][12][13][14] because MA is a critical chemical intermediate having extensive applications in surface coating, 15 polyester resins, 16 agriculture chemicals and lithium ion batteries. 17,18 Currently, oxidation of furfural to synthesize MA is mainly conducted in vapor-phase and liquid-phase systems. 19 However, complex and rigorous conditions, i.e., high reaction temperature and pressure and utilization of H 2 O 2 as the oxidant, [20][21][22][23] usually result in the low yield and poor selectivity of MA in these traditional catalytic systems, 19 thus severely limiting the potential for the large-scale production of MA from oxidation of furfural.…”

“…6–9 In this regard, partial oxidation of furfural to produce maleic acid (MA) has attracted much attention for a long time 10–14 because MA is a critical chemical intermediate having extensive applications in surface coating, 15 polyester resins, 16 agriculture chemicals and lithium ion batteries. 17,18 Currently, oxidation of furfural to synthesize MA is mainly conducted in vapor-phase and liquid-phase systems. 19 However, complex and rigorous conditions, i.e.…”