Browsing by Author "Mbuvi, Harun M."

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Biodegradable Superabsorbent Hydrogel from Activated Hydrochar-Glycerol Cross-linked with Maleic Acid
(American Journal of Polymer Science, 2025-08-13) Mukulu, Stanley M.; Mbuvi, Harun M.; Kasimu, Titus M.; Maingi, Francis M.
amounts of water or aqueous solutions due to the presence of hydrophilic functional groups in their network structures. The increasing population, coupled with advanced technologies, has led to a fourfold increase in demand in industrial applications, technological fields, medical fields, and agriculture. This study reports on the synthesis and characterization of superabsorbent hydrogels derived from activated hydrochar. The preparation of hydrochar was done via the dehydration process of sugarcane bagasse, followed by activation using acidified potassium permanganate to form activated hydrochar (AH). The AH was then reacted with glycerol to form polymer units (AHGL). The polymeric units were then reacted with maleic acid to form a superabsorbent hydrogel (SAH). Characterization of the synthesized SAH was carried out using FT-IR, SEM, and XRD. The swelling capacity was optimized by varying contact time and doses of both glycerol and maleic acid. The FT-IR spectra showed a C=O carbonyl spectral absorption peak at 1711.85 cm⁻¹ in SAH, indicating successful crosslinking. The XRD analysis portrayed the amorphous nature of hydrochar and AH, while AHGL and SAH showed semi-crystalline and crystalline nature, respectively. SEM analysis showed dense porous surfaces in SAH compared to rigid surfaces with fewer and unevenly distributed pores in AHGL. The gravimetric technique showed that the maximum absorption capacity of the SAH was obtained at the optimum reaction mole ratio of AH:GL:MA of 10:4:1. The maximum absorption capacity of the synthesized superabsorbent hydrogel relative to its dry mass was found to be 905% and was achieved in a period of 8 hours. Crosslinking the hydrogel improved the water absorption capacity, and hence, it has potential application in agriculture in arid and semi-arid regions.
Green superabsorbent hydrogel derived from activated charcoal and glycerol with maleic acid as a cross-linker
(Journal of Experimental Sciences, 2024-02-16) Kasimu, Titus M.; Mbuvi, Harun M.; Maingi, Francis M.
Superabsorbent hydrogels characterize a set of polymeric materials with three-dimensional structures capable of absorbing large amounts of water due to their hydrophilic functional groups on their surface. Their application in industries, agriculture, and the environment is of primary significance. This study reports the synthesis and characterization of green superabsorbent hydrogels derived from activated charcoal. The process involved a polymerization reaction between activated charcoal (AC) with glycerol (G) using sodium hydroxide as an initiator in the absence and presence of maleic acid as a crosslinker to synthesize HCG-1 and HCG-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). Optimization conditions were done by synthesizing hydrogel with varying dosages of both activated carbon and maleic acid as well as swelling time. The FT-IR results showed the appearance of strong sharp peaks at 1591.34 cm-1 and 1400.28 cm-1 in HCG-1 associated with -COO¯ symmetric stretching and asymmetric bending vibrations, indicating interlink between reacting monomers. A new absorption band at 1639.48 cm-1 associated with -COO¯ bending in non-conjugated ester indicates ester-crosslink in HCG-2 hydrogel. XRD analysis showed a phase shift from semi-crystalline to crystalline structure upon crosslinking. SEM analysis showed a crystalline intact, rigid structure without voids and pores on its surface in HCG-1 compared to the smooth irregular pores and lamina structure observed in HCG-2 hydrogel. The dosage ratio of AC: G: maleic acid of 8:5:1 produced hydrogel with an optimal water absorption capacity of 1255.80±0.70%. Maleic acid was found to improve the water absorption capacity of the superabsorbent. The study is an eye opener towards the application of biodegradable hydrogels in agriculture, especially in semi and arid regions.
Pyro-processed Coconut Fibre for Removal of Lead Ions from Aqueous Solution
(American Journal of Chemistry and Pharmacy, 2026-05-25) Kasimu, Titus M.; Maingi, Francis M.; Mbuvi, Harun M.; Ng’ang’a, Margaret M.; Abdulhameed, Adamu
Approximately 80% of the population in developing countries lacks access to clean, safe water. A major source of water contamination is heavy metal ions, which pose great risks to human health. This is expected to increase with the projected population and industrial growth if immediate remediation is not taken. Current operational methods for removing the heavy metal ions in wastewater include: chemical coagulation, ion exchange, electrochemical methods, adsorption using activated carbon, natural zeolite, membrane process, ultra-filtration, among others, which are uneconomical due to high costs and unaffordable to low-income earners. Coconut fibres are locally available agricultural waste that can be converted by activation into adsorbents for water remediation due to their fineness and large surface area. This study reports the synthesis and characterization of coconut fibre charcoal (CFC) and activated coconut fibre charcoal (ACFC) to remediate water contaminated with Pb2+ ions. This involved burning dry coconut fibre in a limited amount of air to obtain coconut fibre charcoal followed by dissolving fine powder of charcoal in 2 M phosphoric acid for 24 hours at a temperature of 25 ºC to obtain activated coconut fibre charcoal. The adsorbents were characterized using FT-IR and SEM. Batch sorption studies were carried out while varying parameters of contact time, shaking speed, temperature, adsorbent dose, pH, and initial concentration of metal ions in solution. Residue Pb2+ ion concentrations were determined using atomic absorption spectroscopy (AAS). The FT-IR results showed absorption peaks at 1423 cm-1 and 840 cm-1 attributed to symmetric –COO- stretch and -OH deformation in ACFC adsorbent, these peaks shifted to 1384 cm-1 and 813 cm-1 while PO4- aromatic strain vibration in ACFC disappeared upon saturation of ACFC with Pb2+ ions respectively. SEM analysis showed pores of different sizes and shapes in ACFC compared to a rigid, concrete, and smooth surface upon saturation with Pb2+ ions. Adsorption data for Pb2+ ions best fitted into the Freundlich model with maximum adsorption capacities of 32.09 mg lead/g activated coconut fibre charcoal. The results from this study suggest that coconut fibre charcoal and activated coconut fibre charcoal are potential adsorbents of Pb2+ions.
Synthesis and Characterization of Superabsorbent Hydrogel from Activated Hydrochar-Sucrose Crosslinked with Maleic Acid
(Open Journal of Applied Sciences, 2026-01-30) Mukulu, Stanley M.; Mbuvi, Harun M.; Kasimu, Titus M.; Maingi, Francis M.
Superabsorbent hydrogels are hydrophilic materials forming three-dimensional polymer networks capable of absorbing large amounts of water. They are utilized in various fields, though most current types are non-biodegradable and costly to produce. This research explored a more sustainable approach by synthesizing superabsorbent hydrogels from activated hydrochar derived from sugarcane bagasse, using acidified potassium manganate for activation and sucrose for polymerization. Maleic acid was employed to create crosslinked structures, optimizing swelling capacity through varying conditions. Characterization through FT-IR confirmed successful crosslinkage. XRD analysis showed the amorphous nature of hydrochar and AH as compared to the increased crystallinity exhibited by AHSU polymer units and SAH superabsorbent hydrogel. SEM analysis revealed that the superabsorbent hydrogel had compact permeable surface network structures. The optimal synthesis ratio was found to yield a swelling capacity of 778% within 12 hours, highlighting the potential of these biocompatible hydrogels for agricultural applications in semi-arid and arid regions.
Synthesis of Silicon Nitride from Rice Husk and Sugarcane Bagasse Ashes
(Journal of Water technology and Treatment methods, 2018-01-22) Abdulhameed, Adamu; Mbuvi, Harun M.; Changamu, Evans O; Maingi, Francis M.
Silicon nitride (Si3N4) SNA, SNB, SNC and SND were synthesized by hydrothermal process at temperature of 100oC, 150oC, 200oC and 300oC using Rice Husk Ash (RHA) and Sugarcane Bagasse Ash (SBA) respectively. The percentage of silica ranges from 90.10 to 94.19 with minute impurities.Based on their infrared spectra, for SNA absorption band at 470.6 cm-1 is attributed to Si-N (stretching), which were also observed with SNB, SNC and SND, a weak band at 671.2 cm-1 which is characteristic of a silicon nitride Si-N-Si stretching vibration was observed, for SNC, peak at 574 cm-1 attribute to α-silicon nitride, as temperature increases the spectrum becomes sharper. X-ray diffraction pattern indicates that SNA material contained 64.6% α-phase and 27.8% β-phase silicon nitride. Therefore, rice husks and sugarcane bagasse have great potential as a raw material for producing Si3N4, by the hydrothermal method