Department of Chemistry and Biochemistry

Influence of chemical activation on the strength and durability of lime–corn cob ash cement

Sat, 01 Aug 2026 00:00:00 GMT

Influence of chemical activation on the strength and durability of lime–corn cob ash cement Odiwuor, Vincent O.; Barasa, Stephen S.; Onyambu, Onyambu The slow rate of strength gain and the relatively poor durability of lime–pozzolana binders limit their broader use in sustainable construction applications. This study examined how chemical activation influences the physicochemical characteristics, compressive strength, porosity, and sulfuric acid resistance of lime–corn cob ash (CCA) mortars. CCA was analyzed using X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and electrical conductivity tests to evaluate its pozzolanic behavior. Mortars containing a 50:50 lime–CCA ratio were prepared using water, 0.5 M NaOH, and 0.5 M Na2SO4 as mixing media. The results indicated that CCA is rich in silica (61.61% SiO2), with a combined SiO2 + Al2O3 + Fe2O3 content of 72.19%, confirming its suitability as a pozzolanic material. The reduction in electrical conductivity of about 28.1% after 240 min suggests moderate pozzolanic reactivity of CCA. Chemical activation markedly enhanced performance. Compressive strength increased from 2.91 MPa in the non-activated system to 5.92 MPa and 7.77 MPa for Na2SO4 and NaOH-activated mortars, respectively. Porosity showed a decreasing trend from L100–H2O to LCCA50–0.5 M NaOH. Under sulfuric acid exposure, activated mortars experienced lower mass and strength losses than non-activated ones, with NaOH activation providing the best resistance. In contrast, pure lime mortar fully disintegrated under acidic conditions. The results confirm that chemical activation significantly improves the mechanical performance and durability of lime–CCA binders. The study demonstrates the viability of corn cob ash as a sustainable pozzolanic material for low-carbon, non-structural construction applications and highlights the effectiveness of different chemical activators in enhancing lime-based systems.

Performance and Durability of Chemically Activated Lime-Based Cement Blended With Rice Husk Ash

Wed, 01 Jul 2026 00:00:00 GMT

Performance and Durability of Chemically Activated Lime-Based Cement Blended With Rice Husk Ash Odiwuor, Vincent O.; Samita, Fidelis N.; Wetungu, Martin W. Lime–pozzolana binders ofer a low-carbon alternative to conventional materials; however, their practical application is limited by slow strength development and insufcient durability, particularly under aggressive chemical environments. In addition, existing studies on chemical activation have largely focused on OPC-based systems, with limited attention to lime-based binders and their durability performance. This study investigates the efect of chemical activation on the performance and durability of lime–rice husk ash (RHA) mortars. The objective was to evaluate how sodium hydroxide (NaOH) and sodium sulfate (Na2SO4) infuence compressive strength, porosity, and resistance to sulfuric acid attack of lime mortars. Physicochemical characterization confrmed that the RHA contained 94.95% SiO2 with high amorphous content and strong pozzolanic reactivity (> 60% conductivity loss). Results showed that RHA incorporation improved lime mortar performance, while chemical activation signifcantly enhanced these properties. NaOH activation increased compressive strength by 132%, compared to 53% for Na2SO4, relative to the non- activated system. Porosity decreased progressively across the systems, with the lowest values observed in NaOH-activated mortars. Under acid exposure, all RHA-containing mortars outperformed pure lime, which disintegrated completely. Strength and mass losses were lower in activated systems, particularly with NaOH. Deterioration was more severe in 3% H2SO4 than in a 0.5% solution. The fndings indicate that chemical activation improves the short-term performance of lime–RHA mortars, although reaction products were not directly quantifed. These results highlight the potential of chemically activated lime–RHA mortars as sus- tainable construction materials, particularly in resource-constrained regions.

Using Pozzolanic Materials to Improve Mechanical Properties of Lime-Based Mortar

Mon, 01 Jun 2026 00:00:00 GMT

Using Pozzolanic Materials to Improve Mechanical Properties of Lime-Based Mortar Odiwuor, Vincent O.; Ayabei, Kiplagat; Okoth, Maurice O.; Munyao, Onesmus M. The environmental impact associated with the production of Portland cement has intensifed interest in sustainable alternatives such as lime-based binders. However, their application is constrained by low early strength and slow hardening. This study evaluates rice husk ash (RHA) and sugarcane bagasse ash (SCBA) as pozzolanic additives to enhance the mechanical performance and durability of lime mortars. Hydrated lime was partially replaced (50%) with RHA or SCBA, and the mortars were air-cured for 28 days. Both ashes satisfed the standard pozzolanicity requirements. RHA exhibited a higher amorphous silica content and greater reactivity, whereas SCBA demonstrated slower but sustained pozzolanic activity. The incorporation of these pozzolans signifcantly improved performance. Compressive strength increased from 0.43 MPa for pure lime to 4.64 and 3.84 MPa for RHA and SCBA mortars, respectively. Flexural strength improved from 0.17 to 2.70 MPa and 0.97 MPa for RHA and SCBA mortars, respectively. Water absorption was substantially reduced in the modifed mortars, indicating improved pore structure and du- rability. RHA provided superior strength development and lower permeability, while SCBA ofered moderate strength en- hancement with improved fexibility. These characteristics make both materials suitable for nonstructural applications, including heritage conservation and restoration. The fndings demonstrate that agricultural waste ashes can serve as efective, low-carbon pozzolanic materials for durable lime-based construction.

Pozzolanic reactivity and mortar performance of sugarcane bagasse and sawdust ashes in lime based binders

Sat, 01 Aug 2026 00:00:00 GMT

Pozzolanic reactivity and mortar performance of sugarcane bagasse and sawdust ashes in lime based binders Odiwuor, Vincent O.; Wambu, Enos W.; Okoth, Maurice O.; Kipkemboi, Pius K. The growing energy demand, rising production costs, and environmental impacts associated with ordinary Portland cement have intensified the search for sustainable, low-carbon binders. Lime–pozzolana systems incorporating agricultural waste ashes present a viable alternative; however, their development is often based primarily on strength results, limiting insight into the role of material structure and reactivity. This study comparatively evaluates sugarcane bagasse ash (SCBA) and sawdust ash (SDA) as supplementary cementitious materials in lime-based binders, with emphasis on linking physicochemical properties to performance. The ashes were produced under controlled calcination at 600–700 °C and characterized for oxide composition, mineralogy, particle size distribution, specific surface area, and loss on ignition. SCBA exhibited a high combined content of SiO2 + Al2O3 + Fe2O3 (86.60%) and was predominantly amorphous, whereas SDA showed a significantly lower content (23.16%), higher loss on ignition (15.33%), and a largely crystalline structure, despite possessing a higher specific surface area. Pozzolanic activity was assessed via electrical conductivity measurements. The results revealed faster early reactivity for SDA, attributed to its higher surface area, while SCBA demonstrated more sustained reactivity due to its high amorphous silica content. At 28 days, SCBA–lime mortars achieved compressive strengths of 2.98–3.72 MPa, compared to 1.51–2.52 MPa for SDA–lime mortars across pozzolan-to-lime ratios of 3:1 to 1:1. Similarly, SCBA mortars exhibited higher bulk density (930.6 kg/m3) and lower water absorption (14.14%) than SDA mortars (812.4 kg/m3 and 18.14%, respectively). All mixes exceeded the minimum strength requirement of 2 MPa for lime–pozzolana binders, although they remained significantly lower than the OPC control (48.06 MPa). Overall, SDA enhances early-age reactivity, whereas SCBA provides superior long-term mechanical performance. These findings establish a clear relationship between material characteristics, pozzolanic behavior, and mortar performance, offering practical guidance for the selection of locally available agricultural ashes in sustainable construction.

Physicochemical And Mechanical Performance Of Lime- Based Binders Incorporating Rice Husk Ash And Calcined Clay

Sat, 01 Aug 2026 00:00:00 GMT

Physicochemical And Mechanical Performance Of Lime- Based Binders Incorporating Rice Husk Ash And Calcined Clay Odiwuor, Vincent Onyango,; Wambu, Enos W.; Okoth, Maurice O.; Kipkemboi, Pius K. The environmental concerns linked to ordinary Portland cement have increased the demand for alternative binder systems that utilize locally available resources efficiently and still provide adequate performance. This study investigates the potential of rice husk ash (RHA) and calcined clay (CC) as supplementary pozzolanic materials in lime-based binders. The objective was to comparatively evaluate the influence of these materials on physicochemical properties, reactivity, and mechanical performance and to establish relationships between these parameters. RHA and CC were produced under controlled calcination conditions and characterized using chemical, mineralogical, and surface analyses. Pozzolanic reactivity was assessed through electrical conductivity measurements, while performance was evaluated using water absorption and compressive strength tests. The results showed that both materials satisfied standard chemical requirements for pozzolans; however, their reactivity differed significantly due to variations in structure and surface characteristics. RHA exhibited a predominantly amorphous structure and a high specific surface area, resulting in faster reaction kinetics, greater calcium hydroxide consumption, and slightly higher compressive strength when used in lime-based mortars. In contrast, CC displayed a mixed amorphous–crystalline composition and lower surface area, leading to slower but sustained reactivity. The incorporation of both pozzolans improved compressive strength and reduced water absorption compared to pure lime mortar. After 28 days, blended mortars achieved strengths of approximately 4.2–4.3 MPa, indicating suitability for non-structural applications. The findings demonstrate that binder performance is governed by the combined effects of chemical composition, phase structure, surface properties, and reaction kinetics rather than composition alone. This study provides a systematic comparative assessment of RHA and CC in lime-based systems and highlights the importance of integrating physicochemical characteristics with reactivity measurements to better understand and optimize the performance of sustainable binder materials.

Effects of Adsorbent Dosage and Particle Size on Fluoride Removal Using Calcium-Spiked Moringa oleifera Seed Powder

Mon, 01 Sep 2025 00:00:00 GMT

Effects of Adsorbent Dosage and Particle Size on Fluoride Removal Using Calcium-Spiked Moringa oleifera Seed Powder Chavaregi, Geoffrey,; Lusweti, John; Keronei, Pius Access to safe drinking water remains a major challenge in fluoride-endemic regions, where excessive fluoride concentrations can lead to dental and skeletal fluorosis. This study evaluated the effects of adsorbent dosage, particle size, and particle size classification (mesh size) on the fluoride removal performance of Moringa oleifera seed powder (MOSP) in both calcium-spiked and non-spiked forms. A three-factor factorial batch adsorption experiment was conducted using initial fluoride concentration of 1ppm, dosages of 0.25–2.0 g/100 mL, particle sizes of <250 μm, 250–500 μm, and >500 μm, and mesh classifications of 20 (850 μm), 40 (425 μm), and 60(250 μm). Response variables included fluoride removal efficiency, residual fluoride concentration, and adsorption capacity (qe), measured using a fluoride ion-selective electrode. ANOVA and linear regression were applied to evaluate the dose and size response relationships. Results showed that calcium-spiked MOSP consistently outperformed non-spiked MOSP across all parameters. Fluoride removal efficiency increased with dosage, reaching 88.95% for spiked and 70.34% for non-spiked MOSP at 2.0 g. Finer particle sizes and smaller mesh fractions significantly enhanced removal efficiency and reduced residual fluoride levels, with spiked MOSP at ≤250 μm achieving 89.80% removal and residual fluoride below WHO guidelines. Regression analysis confirmed strong inverse relationships between particle size/mesh size and fluoride removal performance, and positive correlations with dosage. The improved performance of calcium-spiked MOSP is attributed to increased surface-active Ca2+ sites enabling precipitation of CaF2 and enhanced adsorption via electrostatic attraction and ion exchange. These findings indicate that calcium-spiked MOSP, optimally prepared at fine particle size and moderate dosage, is a viable, locally sourced defluoridation medium suitable for rural water treatment systems.

Fluoride Removal Efficiency of Calcium-spiked and Non-spiked Moringa Oleifera Seed Powder

Wed, 01 Oct 2025 00:00:00 GMT

Fluoride Removal Efficiency of Calcium-spiked and Non-spiked Moringa Oleifera Seed Powder Chavaregi, Chavaregi; Lusweti, John; Keronei, Pius Fluoride contamination in drinking water remains a widespread public health concern, particularly in arid and semi-arid regions where groundwater is the primary source of potable water. Chronic exposure to elevated fluoride levels—commonly above the World Health Organization’s (WHO) recommended limit of 1.5 mg/L—can result in dental and skeletal fluorosis, affecting millions of people globally. Affordable and effective defluoridation technologies are urgently needed, especially in low-income rural settings. In this study, the fluoride removal efficiency of calcium-spiked and non-spiked Moringa oleifera seed powder was investigated through controlled laboratory batch adsorption experiments. Biosorbents were prepared by treating ground seed powder with 1% calcium chloride solution and characterised based on their performance across five fluoride concentrations (1-20 ppm). Key parameters such as removal efficiency, residual fluoride levels, and adsorption capacity (qe) were evaluated under consistent operating conditions (pH 7, 2 g/50 mL dose, mesh 40, 120 minutes). Results indicated that calcium-spiked Moringa oleifera powder significantly outperformed its non-spiked counterpart. At 1 ppm, the spiked adsorbent achieved 94.35 ±1.15% removal efficiency, compared to 81.45 ±1.35% for the non-spiked. At the highest tested concentration (20 ppm), the spiked biosorbent still removed 72.31 ±1.80% of fluoride, while the non-spiked removed only 54.21 ±1.95%. Linear regression models showed strong inverse correlations between fluoride concentration and removal efficiency (R2 > 0.99, p < 0.001). The spiked adsorbent also resulted in significantly lower residual fluoride concentrations, with final values closer to the WHO guideline. One-way ANOVA confirmed significant differences in adsorption capacity and efficiency between treatments (p < 0.001). These findings highlight the effectiveness of calcium modification in enhancing biosorption performance and suggest that calcium-spiked Moringa oleifera seed powder is a promising, low-cost, and environmentally friendly solution for mitigating fluoride contamination in drinking water.

DETERMINATION OF DIABETIC WOUND HEALING, ANTIOXIDANT AND ANTI-INFLAMMATORY ACTIVITY OF Cyathula uncinulata CRUDE LEAF EXTRACT IN FRUCTOSE-INDUCED DIABETIC WISTAR RATS

Wed, 01 Jan 2025 00:00:00 GMT

DETERMINATION OF DIABETIC WOUND HEALING, ANTIOXIDANT AND ANTI-INFLAMMATORY ACTIVITY OF Cyathula uncinulata CRUDE LEAF EXTRACT IN FRUCTOSE-INDUCED DIABETIC WISTAR RATS KILONZO, MUTUKU The treatment of a wound in a diabetic patient is difficult for clinicians and researchers since it often heals very slowly, due to lasting inflammation and is subject to prolonged oxidative stress. The current treatments have adverse side effects, are expensive, inaccessible and sometimes inefficient leading to death, infections, reduced quality of life and amputation. Therefore, there is a critical need for affordable, accessible and effective alternatives for diabetic wound management. C. uncinulata has been traditionally used in treatment of wounds and despite the wide spread use there is no scientific evidence to support it in the management of diabetic wounds. Therefore, this study aimed to investigate the phytochemicals, antioxidant activity and Wound healing (WH) features of C. uncinulata leaves extracts in fructose-induced diabetic Wistar rats. Phytochemical screening of the methanolic leaf extract showed higher presence of a high concentration of flavonoids, alkaloids and tannins, as compared to aqueous extract; methanolic extract was selected for in vivo studies. Thirty-five male rats were randomly assigned to seven groups. Two groups received topical methanolic extract, with one group treated with a low dose of 300 mg/kg and the other with a high dose of 600 mg/kg. One group was administered Floxapen (0.2 mL/day). The remaining groups served as controls, with some receiving a vehicle treatment or no treatment at all in this case diabetic control group. The rats were induced with a specific type of injury, which was then topically treated as per the experimental design. The low dose of 300 mg/kg was considered the lower dose, while 600 mg/kg represented the higher dose in the study. In vitro, the methanolic leaf extract showed significant antioxidant activity at all tested concentrations, comparable to ascorbic acid, as well as Hydrogen Peroxide (HP) scavenging, reducing power and catalase enzyme activity (P<0.05). Additionally, the methanolic leaf extract showed significant protection of albumin against protein denaturation at higher doses. In vivo studies, rats treated with the high dose of methanolic extract exhibited faster wound contraction, with their wounds completely healed by day 21. This outcome was similar to the group treated with the standard drug Floxapen, which also showed complete wound healing by the same time point. The Kaplan-Meier curves for the healing rate demonstrated that the treated groups healed faster than the control groups. According to this study’s findings, Cyathula uncinulata had the potential as one of the natural therapeutic agents for the management of diabetic patient wounds due to its antioxidant, anti-inflammatory, and WH properties. These effects indicated that further studies need to be conducted to identify and describe the molecules that act in this way.

AQUEOUS FLUORIDE BIOSORPTION USING CALCIUM-SPIKED AND NON- SPIKED Moringa oleifera SEED POWDER: INFLUENCE OF DOSAGE, PARTICLE SIZE, AND PROCESS PARAMETERS

Wed, 01 Jan 2025 00:00:00 GMT

AQUEOUS FLUORIDE BIOSORPTION USING CALCIUM-SPIKED AND NON- SPIKED Moringa oleifera SEED POWDER: INFLUENCE OF DOSAGE, PARTICLE SIZE, AND PROCESS PARAMETERS CHAVAREGI, GEOFFREY Excessive fluoride concentrations in drinking water pose serious public health risks, including dental and skeletal fluorosis, particularly in rural, semi-arid and arid regions of developing countries where groundwater is the primary source of potable water. Traditional defluoridation methods remain costly, chemically intensive, or environmentally unsustainable, prompting the search for low-cost, eco-friendly alternatives. Moringa oleifera seed powder (MOSP) has emerged as a promising biosorbent, though its native adsorption capacity remains limited. This study aimed to enhance fluoride removal efficiency by modifying MOSP with calcium (Ca-MOSP) and to evaluate the influence of key process parameters including adsorbent dosage,particle size,pH,contact time, temperature and initial fluoride concentration; adsorption equilibrium behaviour, kinetic rates, and thermodynamic properties. Batch experiments were conducted under controlled laboratory conditions using both calcium-spiked and non-spiked MOSP to assess the effect of dosage, particle size, contact time, pH, temperature, and initial fluoride concentration. The biosorption performance was analysed using Langmuir and Freundlich isotherm models, pseudo-first-order and pseudo-second-order kinetics, and thermodynamic parameters such as enthalpy (ΔH°), entropy (ΔS°), and Gibbs free energy (ΔG°). Results showed that calcium spiking significantly improved fluoride removal efficiency, with Ca-MOSP achieving over 90% removal under optimal conditions (2 g/50 mL dosage, 40 mesh size, pH 7-, and 120- minute contact time), compared to 78% for the non-spiked powder. Finer particle sizes led to increased surface area and binding site availability, while increased dosage improved performance up to a saturation threshold. Adsorption was found to be pH- dependent, with neutral pH offering the best removal efficiencies for both biosorbent types. The adsorption isotherm data fitted best with the Langmuir model, suggesting monolayer adsorption on homogeneous surfaces. Ca-MOSP exhibited a higher maximum adsorption capacity (q e = 4.98 mg/g) and affinity constant (Kₗ = 0.442 L/mg) than the non-spiked variant. Kinetic data followed the pseudo-second-order model, indicating chemisorption as the dominant uptake mechanism, with high R² values (>0.99) and strong agreement between experimental and theoretical adsorption capacities. Thermodynamic analysis confirmed that biosorption was endothermic (ΔH° = +28.45 kJ/mol for Ca-MOSP), spontaneous (ΔG° < 0), and associated with an increase in system randomness (ΔS° = +85.6 J/mol·K). Thus, calcium-modified Moringa oleifera seed powder offers a significantly enhanced, sustainable, and low-cost alternative for fluoride remediation in drinking water. The findings support its potential for practical application in areas with fluoride endemism, particularly in rural and resource-limited settings. Recommendations include adopting Ca-MOSP in decentralised treatment systems and optimising operational conditions for field deployment. Future research should explore regeneration potential, competing ion effects, and long-term performance in continuous- flow and field-scale systems.

GREEN TECHNOLOGY FOR WASTEWATER MANAGEMENT: UTILIZING RICE HUSKS, COCONUT SHELLS AND CLAY AS ADSORBENTS FOR BASIC DYE RHODAMINE B AND SELECTED HEAVY METALS

Wed, 01 Jan 2025 00:00:00 GMT

GREEN TECHNOLOGY FOR WASTEWATER MANAGEMENT: UTILIZING RICE HUSKS, COCONUT SHELLS AND CLAY AS ADSORBENTS FOR BASIC DYE RHODAMINE B AND SELECTED HEAVY METALS GICHUKI, JOHN Accumulation of heavy metals such as cobalt, copper, and lead and dyes such as rhodamine B (RB) released by various industries, poses a potential ecological risk of contamination due to their persistent nature and non-biodegradability. A remedial action is needed to mitigate this risk. A study was carried out to look into the possibility of eco-friendly and cost effective activated rice husk charcoal (ARC), coconut shell charcoal (ACC) and activated clay soil (ACS) in removal of heavy metals and rhodamine B dye from waste water. Three metal ions were selected, Cu2+, Co2+ and Pb2+ and were determined using atomic absorption spectrophotometer, AAS. The charcoal was obtained by burning rice husk and coconut shells which had been soaked in phosphoric acid in limited air. The ability of adsorbents to adsorb metal ions from water was investigated by carrying out batch experiment and varying parameters such as initial concentration, adsorbent dose, contact time, agitation speed, temperature and pH. Fourier Transform Infrared (FTIR) analysis detected presence of functional groups of Si-OH, Si-O, Si-O-Si, O-H and C=C in adsorbents upon activation which are responsible for adsorption. For the dye, a characteristic peak at 3200 cm-1 to 3070 cm-1 for aromatic stretch which was confirmed by a stretching vibration peak at around 1400 cm-1 was observed after adsorption. X-ray diffraction (XRD) data indicated that ACS was crystalline while ARC and ACC were amorphous. The X-ray fluorescence (XRF) results show that SiO2, Al2O3, and K2O were the main components where SiO2 were dominant especially in ARC and ACS. With Transmission emission spectroscopy (TEM) analysis, these nanostructures showed significantly different morphologies. Highly porous and hollow structures were visible in all cases though with differences. Brunauer, Emmett and Teller (BET) surface area and average pore diameter determination study showed that there was a relatively equal adsorption-desorption efficiency. This indicated that the adsorbents were highly reusable and that they had good stability. The efficiency of all the adsorbents towards the removal of heavy metals and dye increased with increase in temperature, time and surface area. Varying the pH showed that metals were adsorbed at a maximum pH of 6 while RB was highly adsorbed at pH 4. The equilibrium fitted the Langmuir equation well as compared to Freundrich. The R2 values for Langmuir ranged between 0.9928 to 0.9989 as compared to Freundlich which ranged between 0.9200 to 0.9671. The negative values of change in Gibb’s free energy (-1.55 to -0.581, -1.074 to -0.449 and -1.14 to -0.194 kJ mol-1 for ARC, ACC and ACS respectively) and positive values of change in enthalpy (32.034 to 37.562, 30.615 to 36.193 and 30.08 to 34.76 kJ mol-1 for ARC, ACC and ACS respectively) revealed the process to be spontaneous and endothermic. The use of a pseudo-second-order model, which indicates that chemical adsorption governed the process, allowed for a more accurate description of the adsorption process.