Browsing by Author "Maingi, Francis M."

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Adsorption Kinetics and Isotherms of Methylene Blue by Geopolymers Derived from Common Clay and Rice Husk Ash
(Physical Chemistry, 2017-10-07) Maingi, Francis M.; Mbuvi, H. M.; Ng’ang’a, M. M.; Mwangi, H.
With the onset of industrialization mankind has witnessed various environmental issues in the society. Industrialization has not only brought development and prosperity but eventually disturbed the ecosystem. It is currently estimated that 1.1 billion people in the world lack access to enhanced clean water supplies. Consequently, pursuance of sustainable materials and technologies for wastewater remediation is critical. Use of adsorbents for wastewater treatment is preferable due to their simplicity and cheap materials involved. Geopolymers are synthesized hydrothermally using alumina and silica which possesses amorphous surface for use as adsorbents. There is adequate information and reports in literature that indicate clay contain alumina and silica. Similarly, findings have shown that rice husk ash contains substantial amounts of silica. This work reports synthesis of geopolymers GP-1, GP-2 and GP-3 prepared by using different SiO2/Al2O3 ratios and consequently equilibrium and kinetics behaviour of adsorption of methylene blue. The geopolymers were characterized using FT-IR, EDS, XRD and SEM. Geopolymer adsorbents were subjected to methylene blue batch sorption experiments thate indicated the adsorption of MB increased with increased Si/Al ratio in geopolymers. The adsorption isotherms were described by Langmuir, Freundlich, Temkin and Sips isotherms. Data for adsorption of MB onto geopolymers fitted best in Sips adsorption model. Kinetic studies showed that Pseudo -second order model were more suitable than the Pseudo- first order model in explaining the kinetics of adsorption.
Adsorption of Cadmium Ions on Geopolymers Derived from Ordinary Clay and Rice Husk Ash
(International Journal of Materials and Chemistry, 2018-10-07) Maingi, Francis M.; Mbuvi, H. M.; Ng’ang’a, M. M.; Mwangi, H.
The presence of heavy metals in water is of growing concern. One crucial global strain is the existing disparity in water distribution resulting into millions of people lacking access to safe clean water. This is exasperated by the looming climate change and increased pollution impendence posed by industrialization and population growth. Consequently, pursuance of sustainable materials and technologies for wastewater remediation is critical. Adoption of adsorbents for water treatment is desirable due to their simplicity and cheap materials involved. Geopolymers are prepared hydrothermally using alumina and silica gleaned from clay and rice husks waste materials respectively. These materials are locally attainable and environmentally benign. This work reports synthesis of geopolymers GP-1, GP-2 and GP-3 prepared using clays from three different regions. The XRD diffraction patterns obtained revealed the presence of quartz (SiO2), albite (NaAlSi3O8), vermiculite (Mg,Fe,Al)3((Al,Si)4O10)(OH)2.4H2O), microcline (KAlSi3O8), analcime (NaAlSi2O6•H2O) and natrite (Na2CO3) among other crystalline phases. The initial adsorption rates were found to increase as the Si/Al ratio of the geopolymers increased. The adsorption rates were found to fit into the second order kinetic model. This implies that Cd (II) ions adsorb on geopolymer adsorbents through chemisorption.
Aluminophosphates Derived from Tea Leaves and Pumpkin Seeds Ashes Adsorb Lead Ions from Contaminated Water
(Frontiers in Science, 2018-10-08) Maingi, Francis M.; Mbuvi, H. M.; Ng’ang’a, M. M.
One major global challenge is the existing disparity in water distribution resulting to millions of people lacking access to safe clean water. This will certainly be exacerbated by the impending climate change and increased pollution threats posed by industrialization and population growth. Therefore pursuing sustainable materials and technologies for water remediation is crucial. Adsorbents use for water treatment is preferable owing to its simplicity and cheap materials involved. Aluminophosphates molecular sieves have open-framework structures that possess a wide range of pore openings and large surface area for use as adsorbents that can be synthesized hydrothermally using alumina and phosphates. Literature reports indicate that accumulation of aluminum in tea leaves correlates positively with leaf age. The EDXRF analysis showed that tea leaves ash used contained 30.09% of Al2O3. Similarly, literature findings indicate that pumpkin seeds contain relatively large amounts of phosphorous with the pumpkin seed ash used containing 37.01% of P2O5. Consequently, aluminophosphate APA and APB were synthesized using tea leaves to pumpkin seeds ash ratios of 1:1 and 1:2 respectively. XRD characterization and lead ions batch sorption experiments were done. Turbidity column experiment was done. Data for adsorption of Pb (II) ions data on the adsorbents best fitted into the Langmuir isotherm model. Adsorption capacities obtained from the linearized graphs were 90.91 and 50.0 mg/g for APA and APB respectively. This shows that tea leaves and pumpkin waste can synthesize aluminophosphate adsorbents. Aluminophosphates have shown good potential of removing Pb (II) ions from wastewaters.
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.
Clay-Rice Husk Ash based Geopolymers for Remediation of Pb (II) and Cd (II) from Wastewater
(Egerton Journal of Science & Technology., 2019-10-31) Maingi, Francis M.; Mbuvi, Harun Mbatha; Ng'ang'a, M M; Mwangi, Henry
Industrialization and technological advancements have led to the generation of numerous pollutants such as heavy metals into the aquatic ecosystem. These toxic compounds are extremely dangerous to human health and the environment due to their non-biodegradability, severe toxicity, ability to accumulate and contaminate ground and surface waters. Subsequently, pursuance of sustainable materials and technologies for better attainment of environmental sustainability is critical. This study reports the synthesis of geopolymers GP-1, GP-2 and GP-3 from different clays. Geopolymers were hydrothermally synthesized using clay and rice husks waste as an alumina and silica source respectively. The geopolymers were characterized using Fourier transform-infra red, energy dispersive spectrometry, X-ray diffraction and scanning electron microscope. Batch and gravitational column experiments using Pb (II) and Cd (II) ions were carried out. Increased metal ion uptake was recorded with raised Si/Al ratio of the adsorbents. The mean percentage uptake of 90.23 ± 0.4 and 89.63 ± 0.18 of Pb (II) and Cd (II) were achieved at pH of 4.0 and 5.0 respectively using GP-3. Langmuir, Freundlich and modified Langmuir Freundlich isotherms were used in equilibrium studies. Data for adsorption of Pb (II) and Cd (II) fitted best in the modified Langmuir Freundlich model. The highest adsorption capacities of Pb (II) and Cd (II) were 209.9 and 136.2 mg/g respectively, attained using GP-3. Based on the results obtained, geopolymers produced from common clay and rice husk waste displayed promising potentials in the removal of heavy metal ions from the aqueous phase. Considering the availability of raw materials for geopolymerization and the high metal ions uptake capacities of geopolymers, they can also be used as adsorbents for removal of heavy metals in industrial wastewater.
Effect of potassium dosage on selected growth parameters and yield response modeling on potatoes grown in Molo, Kenya
(Journal of Scientific Agriculture, 2020-10-07) Maingi, Francis M.; Mbuvi, Harun Mbatha
The Molo region of Kenya has experienced decreased potato acreage yields over the years. This has impacted negatively economic endeavors and food security of the region and Kenya at large. A preliminary study on the physical-chemical characterization of the soils indicated that they were deficient in the amount of available potassium. This finding was very important because the majority of the farmers in the region replenish phosphorous and nitrogen but not potassium. Subsequently, the present study was undertaken to determine the effect of replenishing selected farm soils with various potassium levels on the growth and productivity of ‘Shangi’ a variety grown in Molo Sub-county and ultimately determine the soil optimum potassium dose requirement. A field experiment was conducted with seven model-based K fertilizer treatments (0, 33.3, 41.5, 55.3, 133.3, 200 and 266.7 kg K2O/ha) and three replications in Randomized Complete Block Design (RCBD). The potassium sorption study was conducted using soil samples as adsorbent while varying the K+ concentration in solution. The data obtained were treated using both linearized and non-linearized Freundlich adsorption isotherms. The optimum potassium fertilizer rate was evaluated using yield response models (Quadratic, linear-plateau, quadratic-plateau, and square root). The results of the study showed that the increase in soil potassium levels led to a significant increase in growth and yield parameters. Aerial stem number, leaf number per plant, and plant height recorded increase with an increase in K levels. The sorption data were found to fit best in linearized Freundlich isotherm based on correlation coefficient values (R2) and error function analysis. The potassium buffering capacity ranged from 13.667-46.068 with a mean of 33.6 ± 17.4mg/Kg. The quadratic model fitted the data better than other models with R2 (0.9559) and SSE (18.237). K2O fertilizer application at 200 Kg/ha maximized the potato tuber yield to 30.111 Ton/ha. The result showed clearly that there is a need to adopt the use of potassium-based fertilizer according to soil requirements in this region to realize good tuber yield.
Equilibrium, Kinetic, and Thermodynamic Studies of Pb (II) ions Adsorption onto Modified Tamarind Fruit Pulp
(American Journal of Chemistry, 2026-10) Mukhalisi, Stellah Nelima; Maingi, Francis M.; Kowanga, Keno
The challenge of accessing clean drinking water in urban Kenya is compounded by contamination from heavy metals, leading to serious health risks such as kidney and brain damage. Industrialization and technological advancement have exacerbated the problem of increase of Pb (II) ions and other heavy metals in water ecosystem through industrial effluents. This study investigated the use of modified tamarind fruit pulp (MTFP) for the adsorption of (Pb II) ions from synthetic wastewater. Characterization techniques like XRF and FT-IR were utilized, and adsorption experiments were conducted by varying pH, contact time, temperature, dosage, and initial concentrations of the metals. The results were analysed statistically using ANOVA, with significant differences at P ≤ 0.05. The equilibrium studies indicated that the adsorption of Pb (II) ions was best represented by the Freundlich model, with adsorption capacities of 1.30 and 1.67 mg/g for unmodified tamarind fruit pulp (UTFP) and modified tamarind fruit pulp (MTFP), respectively. Thermodynamic study showed that the adsorption process was thermodynamically spontaneous and endothermic. Kinetic studies revealed that chemisorption was the rate limiting step in the adsorption of Pb (II) ions. This information revealed the enhanced capabilities of MTFP to effectively remove Pb (II) ions from wastewater, showcasing its potential as an eco-friendly adsorbent.
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.
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.
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.
Measurement of Radiological Parameters in Harvested Sand in Bungoma County Rivers, Kenya
(Journal of Engineering and Technology for Industrial Applications, 2022-02-08) Waswa, Michael Nakitare; Maingi, Francis M.; Wanyama, Conrad Khisa; Sindani, Lazarus
Samples of sand were collected along the course of ten selected rivers two from each river through random sampling. Activity concentration of 238U, 232Th and 40K were measured using high resolution NaI(Ti) gamma ray spectrometer. Activity concentration of the three primordial radionuclides obtained were used to calculate, absorbed dose rate, annual effective dose rate, interna and external hazard indices and radium equivalent. The average activity concentration for the three primordial radioactive nuclides were; 2±0.1Bq/kg with a range of 0± 0.03Bq/kg to 4±0.24Bq/kg for 238U, 55±2.78Bq/kg with a minimum value of 32±1.6Bq/kg and a maximum value of 87±4.38Bq/kg for 232Th and 51±2,56Bq/kg with a minimum value of 27±1.37Bq/kg and a maximum value of 76±3.8Bq/kg for 40K. The mean activity concentrations for 238U and 40K were below the world averages of 33Bq/kg and 420Bq/kg respectively. The indoor and outdoor annual effective dose rate varied from 0±0mSv/y to 0.2±0.01mSv/y with an average of 0.1±0 mSv/y and 0±0.003mSv/y to 0.1±0.009mSv/y with a mean of 0.1±0.006 mSv/y respectively. The annual effective dose rates were below the safe limits of 1mSv/y. Therefore, use of sand from the selected rivers in Bungoma County, Kenya for construction has minimal health risks to the inhabitants.
Microwave synthesis of Carboxymethylcellulose (CMC) from Rice Husk
(IOSR Journal of Applied Chemistry, 2019-12-07) Abdulhameed, Adamu; Mbuvi, Harun M.; Changamu, Evans O.; Maingi, Francis M.
Carboxymethylcellulose is an important non-toxic cellulose derivative which plays vital roles in paper coating, pharmaceuticals, food, detergents, and others. Research work involving the extraction of cellulose from agricultural biomass and its modification cellulose using a microwave has been reported, but not much work has been done on the rice husk, thus helping in managing associated waste. In this study, cellulose extracted from rice husks was used as the raw material for the synthesis of food-grade carboxymethylcellulose (CMC). In the process of the synthesis of carboxymethylcellulose from rice husk, cellulose was carried out by alkalization, an etherification process, using sodium hydroxide (NaOH) and monochloroacetic acid (MCA). Characterizations of CMC products was carried out by Fourier Transform Infrared (FTIR) spectroscopy and Xray Diffraction (XRD). The reaction conditions optimized include power (microwave), sodium hydroxide concentration, amount of monochloroacetic acid and reaction time. The degree of substitution (DS) was determined using a potentiometric titration method and the maximum DS of 0.79 was obtained when 30% NaOH was used.
Oxalic Acid Functionalized Diatomite for Enhanced Lead (II) ions Adsorption from Wastewater
(Physical Chemistry, 2026-06-08) Masai, Winny Chebeni; Maingi, Francis M.; Makhanu, Maximilla
Increased global demand for batteries and paints has resulted in higher levels of heavy-metal contamination in waterways, harming aquatic life and human health. Lead is of particular concern due to its non-biodegradable nature and persistence at trace levels. Various technologies have been developed for heavy metal removal from wastewater, with adsorption being the most effective and resource-efficient. Information in literature shows that diatomite has the ability to adsorb heavy metal ions from aqueous media but suffers from a low adsorption capacity and specific surface area. This study therefore focused on enhancing the adsorption capacity of low-cost diatomite by functionalizing it with carboxyl groups via oxalic acid. Characterization techniques, including XRF, FT-IR, XRD, and Raman spectroscopy, confirmed the successful functionalization. Batch adsorption experiments demonstrated that functionalized diatomite effectively removed over 80% of Pb (II) ions, with an adsorption capacity of 8.00 mg/g. These findings suggest that functionalized diatomite is a promising potential adsorbent for remediation of heavy metal ions from wastewater.
Physical-Chemical Characterization of Soils in Selected Potato Growing Areas of Molo, Nakuru County Kenya
(SSRG International Journal of Agriculture & Environmental Science, 2020-08-07) Maingi, Francis M.; Mbuvi, Harun Mbatha; Abdulhameed, Adamu
Characterization of soils in selected potato growing farms of Molo, Nakuru County in Kenya was compelled by the decline in potatoes acreage yields observed in the study area over the years. In the pursuit of reasons behind the decline, this study determined levels of some key soil fertility indices in soil samples obtained from selected farms. Four farms that have been in intensive potatoes farming were used. The soil was randomly collected from a depth of 0-10 cm separately for all the investigated sites. Collected site-wise samples were air-dried, ground, and passed through a 2 mm sieve and stored in plastic containers ready for analysis. Analytical techniques employed were Walkley black for carbon, Kjeldahl for nitrogen, standard wet chem soil analysis, saturation method for water porosity, glass electrode determined soil pH, bulk density, particle density, water holding capacity were determined by methods of Keen box. The mean levels of essential soil fertility indices obtained were; soils pH (5.46 ± 0.43), soil bulk density (g/cm3) (1.03 ± 0.01), particle density (2.51 ± 0.08), water holding capacity (%) (36.07 ± 2.57), porosity (0.59 ± 0.01), exchangeable cations (uS/cm) (83.63 ± 14.22), cation exchange capacity (meq/100g) (18.48 ± 0.89), organic carbon (%) (3.50 ± 0.24), total nitrogen (%) (0.17 ± 0.03). Mean micro and macronutrients available (mg/Kg) were; phosphorous (7.11 ± 2.77), potassium (100.27± 8.32), calcium (198.2 ± 35.1), magnesium (20.97 ±4.28), manganese (15.26 ± 1.12), sulphur (2.31 ± 1.88), copper (0.59 ± 0.12), boron (0.38 ± 0.07), zinc (12.96 ± 2.04), sodium (8.61 ± 0.51), iron (147.92 ± 4.10). These findings reveal the extent of some fertility indices depletion in the soils and will form a base for decreased acreage yield of potatoes in this region. The results further form the baseline for future research on the working acreage of key soil fertility indices required for remediation.
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.
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.
Remediation of Water Contaminated with Cr6+ and Cd2+ Using Aluminophosphates Derived from Ashes of Tea Leaves and Pumpkin Seeds
(Chemistry and Materials Research, 2016-10-07) Maingi, Francis M.; Mbuvi, H.M.; Nganga, M. M.
Access to clean water is an ever increasing challenge that is not only fuelled by climate change and phenomenally growth in population but also by pollution by heavy metals arises from many sources that include automobiles, purification of metals, smelting industries, paint industries and textile industries. Water pollution is on the increase owed to industrial development and population increases. Commercial adsorbents frequently used as adsorbents in water remediation remain expensive out of reach to majority low income earners. It is therefore essential to develop cheap adsorbent materials capable of removing Cr6+, Cd2+ ions and turbidity from wastewaters. Tea leaves ash (TLA) and pumpkin seeds ash (PSA) was used to generate aluminophosphates materials by hydrothermal reactions for removal of selected heavy metals from contaminated waters. Two adsorbents A and B were also prepared by varying ratios of TLA and PSA. Material A, (APA) was prepared by mixing TLA and PSA as in ratio of 1:1 while material B, (APB) was prepared by mixing them in ratio of 1:2. XRay diffraction was used for phase identification and characterization of synthesized material. The effects of metal ion concentration, initial pH, contact time, temperature, shaking speed and dosage on percentage removal of Cd+2, and Cr+6 were determined. The equilibrium adsorption data fitted best in Langmuir isotherm model, as it had the highest value of correlation coefficient. Maximum monolayer adsorption capacities were 45.45 mg/g for cadmium and 50.00 mg/g for chromium using APA. Adsorption capacities of APB were 40.00 mg/g for cadmium and 41.67 mg/g for chromium. Based on adsorption capacities, APA was a better adsorbent than APB. The results from this study shows agro based aluminophosphates are potential adsorbents for remediation of heavy metals from waste waters.
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.
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