Faculty of Science

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Geopolymers Filters from Calcined Clay and Sugarcane Bagasse Blended with Activated Carbon for Removal of Selected Heavy Metals from Wastewater
(American Journal of Chemistry, 2022-10-08) Mwaura, D. M.; Mbuvi, H. M.; Maingi, Francis M.
The growth of industries and the exploitation of natural resources have led to increase of heavy metals concentrations in the earth’s surface, atmosphere and water bodies. Heavy metals pose serious environmental and health effects in the society since they are toxic and non-biodegradable. Removing heavy metals from aqueous solutions especially wastewater has become an area of study in the recent past. Various methods like ion exchange, reverse osmosis, coagulation and adsorption among others have been put forth in the removal of heavy metal ions. Geopolymers are zeolite analogues and there is little information on their use as water filters in literature. Incorporation of geopolymers and activated carbon to form wastewater filters have not been studied. This study focused on fabricating geopolymer filters derived from calcined clay and sugarcane bagasse ash incorporated with activated carbon for removal of heavy metals from aqueous media. Characterization of the Geopolymer, and activated carbon were done using XRF, XRD and FT-IR. Column adsorption using geopolymer/activated carbon filters was employed with Pb (II) and Cu (II) as the test heavy metal ions while varying concentration, filter thickness, and pH. Halo broad peaks were observed in the diffraction patterns at angle 2-theta between 20°- 34° in both geopolymer and activated carbon an indication that they were amorphous. Geopolymer: activated carbon ratio of 2:1, filter thickness of 4cm and pH range of 4-6.5 gave removal percentage of above 85% for both heavy metal ions. The experimental data fitted best in Freundlich adsorption isotherm with correlation coefficient (R2) of 0.854, 0.978 for Pb (II) ions, and Cu (II) respectively. Adsorption capacities of 0.028 mg/g and 0.015mg/g for Pb (II) ions, and Cu (II) ions were obtained respectively. The study shows that geopolymers/activated carbon filters have a potential of removing heavy metal ions from aqueous solution and hence can be applied for remediation of wastewater from industrial effluents.
Iron uptake in spinach (Spinacia oleracea) using biochar-iron complex derived from sugarcane bagasse under greenhouse conditions
(Journal of Scientific Agriculture, 2025-10-30) Kamaau, Meshack Mutungi; Mbuvi, Harun; Maingi, Francis M.
Iron deficiency limits spinach (Spinacia oleracea) growth and nutritional quality, particularly in alkaline soils. By investigating the complexation of iron with sugarcane bagasse-derived biochar, this study aimed to bridge that gap and offer insights into an innovative approach for improving iron nutrition in spinach crops. This study also evaluated the efficacy of sugarcane bagasse-derived biochar-iron complexes in enhancing iron uptake under controlled greenhouse conditions. Biochar-iron complexes were synthesized via pyrolysis and treated with iron (FeCl3) at 0.25 M, 0.50 M, and 0.75 M. In the greenhouse, using a Randomized Complete Design (RCD), the experiment compared treatments including FeCl3 only, biochar only and biochar-iron complexes at 0.25 M, 0.50 M, and 0.75 M concentrations against an untreated control. Iron uptake in spinach leaves was measured over three months using Atomic Absorption Spectroscopy (AAS). Infrared Fourier Transform Spectroscopy (FT-IR) analysis confirmed key functional groups involved in biochariron chelation, while X-Ray Fluorescence (XRF) revealed increased iron loading, peaking at 0.75 M. Analysis of variance from the greenhouse study revealed significant effects of treatment, time, and their interaction (p<0.001). Although the 0.75 M treatment produced the highest iron content (220 to 300 ppm), the 0.50 M biochar-iron complex is considered optimal, as it achieved iron levels within the FAO guideline range (80-250 ppm). In contrast, conventional FeCl3 treatment-maintained leaf iron at only 1.7-1.9 ppm throughout the three months, reflecting poor soil retention and rapid leaching of FeCl3. These findings highlight the composite’s superior magnitude and temporal stability of iron delivery. Sugarcane bagasse biochar–iron composite thus emerges as a promising, eco-friendly alternative to synthetic iron fertilizers for improving soil fertility and crop nutrition, addressing iron deficiency in sustainable food production.
Radiological Measurement of Hazardous Levels in Construction Tiles in Bungoma County, Kenya
(Journal of Engineering and Technology for Industrial Applications, 2022-02-07) Nalianya, John Simiyu; Waswa, Michael Nakitare; Maingi, Francis M.; Wanyama, Conrad Khisa
Twenty (20) different local and imported tiles were sampled from major hardware’s in Bungoma. The samples collected were separately ground, sieved, through a 0.5mm mesh, dried at 110° C, weight and packed in a 200ml stoppered plastic bottles. The samples were stamped with identification numbers and kept for 30 days for secular equilibrium to be reached between the activity of 238U,232Th ,40K radium and their progeny. The average activity concentration of 238U, 232Th and 40K was found to be 109±5.48Bqkg-1, 11±0.55 Bqkg-1 and 1574±78.7 Bqkg-1 respectively. The average absorbed dose rate was found to be 140±7.03 nGyh-1 which is higher than the worlds average value of 60 nGyh-1. The average radium equivalent was found to be 288±14.44 Bqkg-1 which is lower than the world limit value of 370Bqkg-1. External and internal hazard indices were found to be 0.70±0.03 msvy-1 and 0.80±0.04 msvy-1respectively. Therefore, the sampled tiles used in Bungoma county for construction has minimal radiological threat to population.
Synthesis and characterization of cellulose phosphate-based superabsorbent hydrogels from rice husk under microwave heating
(Science Direct, 2025-06-07) Abdulhameed, Adamu; Mbuvi, Harun; Changamu, Evans; Githinji, Irene; Maingi, Francis M.
The current study deals with the synthesis and characterization of superabsorbent hydrogels from rice husk cellulose. Rice husks are slow decomposing waste from the milling of rice with an estimated composition of cellulose (50 %), lignin (25–30 %), silica (15–20 %), and moisture (10–15 %). The aim of using it as a source of cellulose was to provide an alternative use of the otherwise incinerated waste product that is abundantly available in rice producing countries like Kenya. Cellulose-based hydrogels continue to attract interest because of their biocompatibility and biodegradability for which they have found use in several fields including drug release, packaging films, agriculture, among others. The cellulose was extracted from rice husk and crosslinked with phosphoric acid under microwave oven heating. The products were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, x-ray diffraction and x-ray fluorescence. Four parameters namely, heating time, microwave oven power out-put, percent swelling and the amount of cross-linker required for complete reaction were optimized for the synthesis of superabsorbent hydrogels. The optimum percentage swelling was found to be 877 %, heating time of 3 minutes, microwave oven power output of 420 watts (level 6 on the microwave oven dial), 10 mL of cross-linker when 2 g cellulose was used. The efficacy of the hydrogel in maize growing was determined by planting maize in pots in a greenhouse under varied hydrogel dose treatments and measuring growth and yield parameters over a period of twelve weeks. The values of plant growth and yield parameters were found to increase with hydrogel dose with the best results being observed among maize plants grown under the hydrogel dose of 5 g per pot. It was observed that the maize plants in pots treated with hydrogel continued to thrive while those in pots without any hydrogel dried off as expected when rains fail. These results are significant in that they demonstrate that rice husk cellulose-based hydrogels are efficacious in maize growing in a greenhouse.
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.

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Browsing Faculty of Science by Author "Maingi, Francis M."