Browsing by Author "Ouma, Linda"

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Activity Concentration and Associated Radiation Dose in Machinjoni Dumpsite in Trans-Nzoia County, Kenya.
(International Journal of Novel Research and Development, 2023-09-22) Barasa, Ezekiel Simyu; Waswa, Michael Nakitare; Ouma, Linda
The activity concentration in Machinjoni dumpsite has been investigated. Activity concentration was measured using a 76 mm x76 mm NaI (Tl) detector using gamma ray spectrometry technique and various radiological parameters calculated to quantify the level of radiological hazardousness posed by the dumpsite on those interacting with the dumpsite. The mean activity concentration of 238U, 232Th and 40K in the dumpsite were 16±0.83 BqKg-1, 68±3.4 BqKg-1 and 60±3 BqKg-1 respectively. 232Th exceeded the permissible limit of 45 BqKg-1 while 238U and 40K were within permissible limits. The radiological hazard calculated in this study was absorbed dose rate. The calculated values of absorbed dose rate ranged from 29±1.45 to 140±7.03 nGyhr-1 with a mean of 51±2.56 nGh-1 and were lower than the world mean value of 84 nGhr-1. From the values it can be seen that there is significant radiation it parts of the dumpsite even though the mean values were all below permissible world values.
Effects of alum, soda ash, and carbon dioxide on 40–50 year old concrete wastewater tanks
(Physical Sciences Review, 2023-11-06) Maundu, Mutua; Ouma, Linda; Maingi, Francis
Concrete is among the foremost used construction materials around the world, however, there is limited information to determine how aging concrete is affected by chemicals. Concrete is used in the construction of domestic and industrial infrastructure including walls, beams, roof slabs, pipes and drainage systems. With increasing industrialization, chemicals are continuously released contributing to concrete degradation. Sulfuric acid is one of the most detrimental chemicals to concrete, yet it is commonly used in most industries. The effects of carbon dioxide, alum, and soda ash on 40–50 year old concrete structures were determined. Results showed the presence of Fe3+ ions with a mean concentration of 3.24 ± 0.02 mg/L in the residuum on the alum tank. This was due to the slightly acidic alum solution reacting with calcium hydroxide and iron in the concrete matrix over years thus depriving concrete of its binding power. The high amount of soda ash, a strong base, corrodes the concrete walls and surfaces hence creating cracks on the concrete matrix. Carbonation effects brought about by carbon dioxide were also observed at the time of the study.
Optimization studies of BTX removal by magnetite coated oleic acid obtained from microwave‑assisted synthesis using response surface methodology
(Scientific Reports, 2022-12-13) Masuku, Makhosazana; Ouma, Linda; Sanni, Saheed; Pholosi, Agnes
Benzene, toluene and xylene (BTX) are volatile organic compounds released into the environment, that require urgent removal to avoid adverse health effects. In this work, the modelling and optimization of the preparation factors for magnetite coated oleic acid (MNP-OA) composite from microwave synthesis using response surface methodology were conducted to maximize BTX removal, and iron content. The influence of five crucial preparation variables: the Fe3+/Fe2+ solution volumes, microwave power, volume of ammonia water (VAW), reaction time and volume of oleic acid (VOA) on the iron content (% Fe), and BTX adsorption capacity were investigated. The analysis of variance results revealed that VOA and VAW were the most influential factors for high % Fe content, and improved BTX removal. The % Fe, and BTX adsorption capacity for MNP-OA composite at optimized experimental conditions were estimated to be 85.57%, 90.02 mg/g (benzene), 90.07 mg/g (toluene), and 96.31 mg/g (xylene).
Probing the interaction effects of metal ions in MnxFe(3 x)O4 on arsenite oxidation and adsorption
(Royal Society of Chemistry, 2019-12-27) Ouma, Linda; Ofomaja, Augustine
Wastewater treatment is still a global concern and materials capable of pollutant sequestration continue to be improved in a bid to ensure water reusability and curb water shortages. Some of the most promising materials so far are nanosized materials because of their unique properties and the ease of manipulation to improve their properties. In this work we investigated the effects of varying Fe3+ : Fe2+ ratios in magnetite nanoparticles and the influence of manganese doping. Diffraction measurements indicated that the manganese introduced into the magnetite matrix displaced some Fe atoms resulting in the formation of a uniform phase matching the card data for magnetite with no additional manganese phases being formed. XPS confirmed the presence of manganese on the surface of the doped nanomaterials and that both As(III) and As(V) were bound on the adsorbent surface. The central composite design (CCD) of response surface methodology (RSM) was used to determine the effects the nanoparticle compositions had on As(III) adsorption and oxidation. A quadratic equation was used to model the experimental data with a correlation coefficient close to unity indicating that the model was a good fit for the data. The interaction between Fe3+ and Mn had a positive influence in the reduction of As(III) in solution while Fe3+/Fe2+ interactions had antagonistic effects and the Fe2+/Mn interactions were found to be insignificant. Increasing the amounts of Fe3+ and manganese therefore resulted in the highest reduction in As(III) concentration.
Response Surface Methodology Analysis Of Animal Manure Mixtures On Macronutrient Content
(IOSR Journal of Agriculture and Veterinary Science, 2024-08-22) Magero, Simon; Ouma, Linda; Maingi, Francis
The macro and micronutrient composition, pH, and absorptivity of manure from livestock and poultry differ. To increase the nutrient content of soils, several types of manure must be combined. One strategy to increase manure efficiency is mixing ratio optimization. This study aimed to ascertain the nutrient levels of manure from various farm animals and assess the interactions between the manure and the resulting nutrients. Polynomial equations were created as a mathematical model to tie the factors to the responses. The central composite design (CCD) of response surface methodology (RSM) was utilized to investigate the impact of different animal manures on macro nutrients that were chosen as responses. RSM was also used to determine each manure type's level of significance as well as the interactive effects. According to the findings of the study, goat manure was richest in phosphorus (1.27%), potassium (1.24%), and calcium (4.68%), whereas poultry manure was richest in nitrogen (1.45%). The study showed that while a combination of cattle and swine produced a mixture high in nitrogen, blending goats, poultry, and swine manure gave the highest phosphorus levels. A mixture of cattle, goat, and pig manure was provided an organic fertilizer that was rich in calcium and potassium. To assist in blending different types of wellchosen animal manure for the creation of the intended nutrient-rich organic fertilizer, second and third-order polynomials were devised. Calcium, potassium, and phosphorous fitted best in a third–order polynomial while nitrogen was fitted in a second-order polynomial.