Browsing by Author "Francis M. Maingi"

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Glycerol/lemon juice/based green superabsorbent hydrogel cross-linked with maleic acid
(2022) Titus M. Kasimu; Harun M. Mbuvi; Francis M. Maingi
Superabsorbent hydrogels continue to be very important materials due to their applications in several technologies. Unfortunately, most superabsorbent hydrogels currently on the market are acrylate-based products that are non-biodegradable, and, most importantly, some concerns exist about their toxicity for use in agriculture. This study aimed at synthesizing and characterizing biocompatible superabsorbent hydrogel derived from lemon juice. The process involved polymerizing lemon juice (LJ) with glycerol (G) monomers to form polymeric material (HLG-1). HLG-1 was then converted to HLG-2 by crosslinking with maleic acid. Characterization of the hydrogels was done using Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), and X-ray diffraction (XRD). The synthesis conditions producing optimal swelling capacity were studied by varying contact time and dosage of both lemon juice and the cross-linker. The FT-IR results showed a peak at 1528 cm-1 and 1591.34 cm-1 associated with –COO- stretching indicating successful polymerization and crosslinking processes. XRD analysis showed conversion from amorphous to crystalline phases upon crosslinking. SEM micrographs showed clear pores with large surface area in HLG-2 compared with the rigid and constricted surface of HLG-1 hydrogel. A maximum swelling capacity of 910% was obtained upon synthesizing hydrogel HLG-2 with lemon juice, glycerol, and maleic acid of a volume ratio of 5.4: 3.75: 3.75 respectively. Crosslinking the hydrogel with maleic acid was found to improve the water absorption capacity of the hydrogel. The superabsorbent hydrogel with such high swelling and water absorption ability has the potential of being applied in arid and semi-arid regions to boost agricultural production.
Super Absorbent Hydrogel Derived from Activated Charcoal Functionalized with Ethylenediamine and Cross-linked with Maleic Acid
(International Journal of Materials and Chemistry, 2022-01-13) Titus M. Kasimu; Harun M. Mbuvi; Francis M. Maingi
Superabsorbent hydrogels represent a set of polymeric materials with three-dimensional networks capable of holding a huge amount of water due to their hydrophilic nature in their structure. Their application in industries and the environment is of prime importance. This study reports the synthesis and characterization of superabsorbent hydrogels derived from activated charcoal. The activated charcoal (AC) was functionalized with ethylenediamine (EA) using sodium hydroxide as a catalyst in the absence and presence of maleic acid as a cross linker to synthesize HCE-1 and HCE-2 superabsorbent hydrogel respectively. Characterization of the hydrogels was done using Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), and X-ray diffraction (XRD). The synthesis conditions producing optimal swelling capacity were studied by varying contact time and dosage of both activated carbon and the maleic acid. The results showed presence of C-N- stretching vibration at 1590.99 cm-1 in FT-IR spectrum of HCE-1 indicating interlinking between AC and EA monomers. XRD analysis showed a shift from amorphous to crystalline upon crosslinking. SEM analysis showed dense mast homogenous morphology with clear pores network in HCE-2 compared to the rigid rough surface observed in HCE-1 hydrogel. The dose ratio of AC: EA: maleic acid of 6:5:2 produced hydrogel with highest water absorption capacity of 1089.7±0.6%. Crosslinking the hydrogel with maleic acid was found to improve the water absorption capacity of the absorbent. The study provides a baseline for the application of the hydrogel in agriculture, especially in semi and arid regions.
Superabsorbent Hydrogel derived from Lemon Juice/Ethylenediamine with Maleic Acid as a Cross-Linker
(International Journal of Composite Materials, 2021-10-30) Titus M. Kasimu; Harun M. Mbuvi; Francis M. Maingi
Hydrogels are 3-dimensional polymer network materials with the ability to absorb a large amount of water. The current advancement in technology has increased their demand in the fields of industrial and environmental applications. This study reports the synthesis and characterization of superabsorbent hydrogels derived from lemon juice. The preparation involved linking lemon juice (LJ) with Ethylenediamine (EDA) via an amide linkage to obtain HLE-1 hydrogel. The polymer hydrogel was then cross-linked with maleic acid via an ester linkage to form HLE-2 hydrogel. Characterization was done using FT-IR, SEM, and XRD. The optimization of the swelling conditions was studied by varying contact time and the dosage of both lemon juice and the cross-linker. XRD analysis showed the conversion of amorphous hydrogel HLE-1 to crystalline hydrogel HLE-2 upon cross-linking. The FT-IR spectra showed a new strong symmetric stretching -COO- peak at 1079.83 cm-1 in HLE-2 indicating successful ester linkage. SEM analysis showed pores of different sizes and shapes in HAE-2 compared to a rigid, concrete, and smooth surface in HLE-1. Upon the optimization of the synthesis conditions of the cross-linked hydrogel, a swelling capacity of 925% was obtained. Crosslinking the hydrogel improved its water absorption ability. The high swelling capacity of the hydrogel provides a baseline for potential application in agriculture, especially in semi and arid regions.