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Mbugua, JK, Mbui DN, Mwaniki J, mwaura F, Sheriff S.  2020.  Influence of Substrate Proximate Properties on Voltage Production in Microbial Fuel Cells. Journal of Sustainable Bioenergy Systems. 10(02):43. AbstractJournal of Sustainable Bioenergy Systems

In the current study, we investigate the influence of proximate properties of five different fruits on voltage and current generated from a double chamber microbial fuel cell. Fruits comprising of avocado, tomato, banana, watermelon and mango were analyzed for proximate properties using standard methods. Rumen fluid was used as the inoculum in fabricated H-shaped double chamber fuel cells with graphite rods electrodes at room temperature. The voltage and current generated were monitored daily for 30 days using a DT9205A digital multi-meter. The average moisture content for the fruits samples ranged from 82.86% - 95.16% while the crude fat was in the range of 0.12% - 0.33% with avocado having fat levels at 9.03%. Carbohydrates level was the highest in banana at 19.24% and the lowest in tomato waste at 2.93%. Tomato waste produced the highest voltage of 0.702 V on day 20 while lower voltage was noted in watermelon fruit wastes at 0.019 V. The voltage and current increased linearly with time for all the fruit wastes. These results indicate that substrate proximate properties influence the voltage and current generated in microbial fuel cell. In addition, moisture content and carbohydrates level were the major factors that influence microbial fuel cells performance.

Rop, K, Mbui D, Karuku GN, Michira I, Njomo N.  2020.  Characterization of water hyacinth cellulose-g-poly (ammonium acrylate-co-acrylic acid)/nano-hydroxyapatite polymer hydrogel composite for potential agricultural application. Results in Chemistry. 2:100020. AbstractResults in Chemistry

Polymer nano-composite was prepared by grafting partially neutralized acrylic acid onto swollen cellulose isolated from water hyacinth in the presence of nano-hydroxyapatite (nano-HA) using N,N-methylene-bis-acrylamide (MBA) as the cross-linker and ammonium persulphate (APS) as the free radical initiator. Water absorption tests showed an increase in swelling ratio of the copolymer with increased nano-HA content to value of 120 g/g at 2.5% w/v above which it declined. FTIR spectrum of nano-composite revealed grafting of the monomer (acrylic acid/ammonium acrylate) onto cellulose and nano-HA. Transmission electron microscopy (TEM) images of nano-HA synthesized in the presence of Triton X-100 (non-ionic surfactant) displayed rod-shaped agglomerates and nano-particle dispersion within the copolymer matrix. Energy dispersive X-ray (EDX) spectra revealed the constituents of nano-composite to be …

Chebet, EB, Kibet JK, Mbui D.  2020.  The assessment of water quality in river Molo water basin, Kenya. Applied Water Science. 10(4):1-10. AbstractApplied Water Science

The monitoring of water quality for both domestic and commercial use is absolutely essential for policy formulation that affects both public and environmental health. This study investigates the quality of water of river Molo system which lies in the Kenyan Rift Valley. The river is considered a vital source of water for the residents and industrial activities in Nakuru and Baringo Counties. Six water samples were collected during the dry season of December 2017. Various physicochemical parameters were determined in situ by use of a portable pH meter. These parameters included pH, temperature, electrical conductivity and total dissolved solids (TDS). Anions such as fluorides, sulfates, phosphates, nitrates, chlorides, carbonates and bicarbonates were determined using conventional methods such as titrimetry and (ultra-violet visible) UV–Vis techniques. The cations including sodium, potassium, calcium and …
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Rop, K, Mbui D, Njomo N, Karuku GN, Karuku GN, Michira I, Ajayi RF.  2019.  Biodegradable water hyacinth cellulose-graft-poly (ammonium acrylate-co-acrylic acid) polymer hydrogel for potential agricultural application. Heliyon. 5(3):e01416. AbstractHeliyon

Swollen cellulose fibres isolated from water hyacinth were utilized in the synthesis of water hyacinth cellulose-graft-poly(ammonium acrylate-co-acrylic acid) polymer hydrogel (PHG). Acrylic acid (AA) partially neutralized with NH3 was heterogeneously grafted onto swollen cellulose by radical polymerization reaction using N,N-methylene-bis-acrylamide (MBA) as the cross-linker and ammonium persulphate (APS) as the initiator. The reaction conditions were optimized through assessment of grafting parameters such as grafting cross-linking percentage (GCP), percentage grafting cross-linking efficiency (%GCE) and water absorption tests. Characterization of the copolymer by Fourier Transform Infra-red (FTIR) spectroscopy revealed successful grafting of the monomer onto cellulose. Transmission electron microscopy (TEM) image of acetone-extracted PHG displayed micro-porous structure. The optimized product …

Kamau, JM, Mbui DN, Mwaniki JM, Mwaura FB.  2019.  Application of microbial fuel cells in the degradation of 2, 4, 5, 6-tetrachloroisophthalonitrile (chlorothalonil). Journal of Bioscience and Biotechnology Discovery. 4(2):28-35. AbstractJournal of Bioscience and Biotechnology Discovery

Pesticide’s persistence in the environment due to the relatively slow degradation mechanism leads to their bio-accumulation which in turn has adverse impacts on human health. Bio-remediation involves utilization of microbes from nature to the breakdown of organic molecules. The purpose of this study is to investigate the potential of microbes in degrading chlorothalonil. Aerobic-anaerobic combined conditions in an H-shaped double chamber microbial fuel cell (MFC) were employed for the breakdown of chlorothalonil. Decomposing tomatoes were used as the major substrate with their proximate properties being analyzed using standard method. Glucose loaded with different concentrations of chlorothalonil was introduced to the cells on day 10 when voltage production had stabilized. The voltage and current generated were monitored using a digital multi-meter while pesticide concentrations were obtained using a UV-Vis spectrophotometer. The highest voltage readings were obtained on day 9 of degradation, with values ranging from 0.463 to 0.537 V. The current ranged from 0.002 to 0.076 mA. Higher voltage and current values were recorded in solutions with lower pesticide concentration. The obtained degradation level was highest in 10 g glucose at 95.95 and 98.75% for day 10 and 20 respectively. The lowest breakdown was observed in the cells without glucose at 10.54 and 31.04% on day 10 and 20 respectively. The results demonstrate that MFC technology can be employed in mineralization of chlorinated pesticides as an alternative for incineration and photo-degradation.

Rop, K, Karuku GN, Mbui D, Njomo N, Michira I.  2019.  Evaluating the effects of formulated nano-NPK slow release fertilizer composite on the performance and yield of maize, kale and capsicum. Annals of Agricultural Sciences. 64(1):Pages9-19. AbstractAnnals of Agricultural Sciences


Effect of formulated slow release NPK fertilizer [cellulose-graft-poly(acrylamide)/nanohydroxyapatite/soluble fertilizer] composite (SRF) on the performance and yield of maize, kale and capsicum was evaluated in a greenhouse experiment. No significant difference in growth parameters was observed between SRF and commercial fertilizer (CF) treatments. SRF recorded higher dry matter and yields relative to CF with similar application rates, though statistically insignificant. P deficiency was observed in maize at lowest SRF application rate of 45-57-17. N deficiency in CF was observed at the 8th week, but not in SRF with similar application rates during the same period. Kale showed both N and P deficiencies in the 7th week, while capsicum alone showed N deficiency in the 14th week in SRF at low application rates. NPK content in both maize and kale tissues, was significant between the amendments and control. Capsicum tissues had significantly (p ≤ 0.05) higher N content both in SRF and CF higher application rates of 125-159-45 & 100-100-100, respectively, compared to control. At final harvest, soil samples planted with maize and amended with the highest SRF rate showed significantly (p ≤ 0.05) higher P content, compared to lower rates and the control. The agronomic optimal rate of SRF determined by quadratic function were found to be higher than that of CF. SRF was found to enhance growth and yields of crops just like CF and could potentially have greater benefits such as improving soil health and resilience.


Chebet, E, Mbui D, Kibet J, Kamau G.  2018.  The Speciation of Selected Trace Metals in Nairobi River Water, Kenya. Eurasian Journal of Analytical Chemistry. 13(4):1-11. AbstractEurasian Journal of Analytical Chemistry

Metal ions form complexes with naturally occurring ligands released from industrial effluent. The complexes are transported and enter the environment and biological system leading to environmental degradation and health problems. This contribution investigates the speciation of trace metals in water samples collected from Nairobi River. Heavy metals (Pb, Mn, Cu, Fe, Cr and Zn) were determined using spectroscopic techniques whereas sulfaver 4 method, diazotization, and titration methods were used to determine the concentration of SO42+, NO2-, F-and Cl-respectively. It was found that~ 69.8% of total iron was in oxidation state III; the dominant species being Fe2+, Fe (OH) SO4,[FeF4]-, FeSO4, Fe2+ and [Fe (OH) 2]+ during both the dry and wet seasons. Manganese was found exclusively in oxidation state II (100%) in which some of its major chemical forms were Mn2+ and [MnF6] 4-. Copper was present mostly in oxidation state II (Cu2+) while lead and zinc existed chiefly as ([Zn (SO4) 4] 6-and [Pb (SO4) 3] 4-) complexes. Chromium was trivalent with its main complexes being [Cr4 (OH) 6] 6+ and Cr (OH)(SO4)). Traces of free metal ions (Cu, Fe and Mn) were found in Lenana section of Nairobi River. Traces of free metal ions are the most aggressive water toxicants due to their high solubility in biological systems.

Kamau, JM, Mbui DN, Mwaniki JM, Mwaura FB.  2018.  Utilization of rumen fluid in production of bio–energy from market waste using microbial fuel cells technology. J Appl Biotechnol Bioeng. 5(4):227-231. AbstractJ Appl Biotechnol Bioeng

Environmental Protection Agency classifies slaughter house waste as one of the most toxic environmental pollutants due to high pathogen content. Composting and anaerobic digestion are among the most common methods used for its disposal. In this study, utilization of rumen fluid as bio–catalyst in microbial fuel cells is investigated. Different market wastes were converted to electricity by loading them in anodic anaerobic chamber and then adding rumen fluid from Dagoretti slaughterhouse. 0.584 V was obtained on day 19 from avocado fruit waste while the maximum voltage for tomato waste was 0.701 V on day 20. Water melon and fruits mixture produced the least voltage. The maximum power from the tested substrate was obtained from tomato wastes. The power and current density were in the range of 1.825 to 60.041 mW/m2 and 6.762 and 99.174 mA/m2 respectively for tomato wastes. A maximum voltage of 0.584 V was obtained from tomato wastes when 500ml rumen fluid was used while 0.248 Vwas obtained for avocado fruit waste with the same amount of rumen fluid. Electrode surface area of 0.006666 m2 gave the highest voltage and power amongst 0.00399 m2 and 0.01331 m2. When the influence of external resistors was investigated, power, voltage and current obtained across a 45kΩ were 0.385 V, 0.038 Ma and 0.01463 mW on day 7 respectively for tomato wastes.

Rop, K, Karuku GN, Mbui D, Michira I, Njomo N.  2018.  Formulation of slow release NPK fertilizer (cellulose-graft-poly (acrylamide)/nano-hydroxyapatite/soluble fertilizer) composite and evaluating its N mineralization potential. Annals of Agricultural Sciences. 63(2):163-172. AbstractAnnals of Agricultural Sciences

Polymer nano-composite fertilizer formulation has the potential to enhance nutrient use efficiency. Slow release fertilizer (SRF) composite was formulated by incorporating nano-hydroxyapatite (nano-HA) and water soluble fertilizers (urea, (NH4)2HPO4 and K2SO4) into water hyacinth cellulose-graft-poly(acrylamide) polymer hydrogel. Fourier Transform Infra-red spectra revealed existence of chemical interaction between the monomer, cellulose, urea and nano-HA. The release of nutrients was assessed using laboratory incubation experiment. Significantly higher content of mineral nitrogen (MN) was observed in the first 4 weeks in conventional fertilizer (CF) compared to SRF treatments and the control. MN content in SRF treatments increased considerably between the 8th and 12th week, and declined in the 16th week. The values of potentially mineralizable N estimated using first order kinetics model related well …


Kamau, JM, Mbui DN, Mwaniki JM, Mwaura FB, Kamau GN.  2017.  Microbial fuel cells: influence of external resistors on power, current and power density. J Thermodyn Catal. 8(1):100-182. AbstractJ Thermodyn Catal

Copyright:© 2017 Kamau JM, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Mbugua, JK, Mbui D, Kamau GN.  2017.  Investigation of Rate of Photo-Degradation of Chlorothalonil, Lambda Cyhalothrin, Pentachlorophenol and Chlropysis on Tomato and Spinach. Mod Chem Appl. 5(200):2. AbstractMod Chem Appl

Photo-degradation of common pesticides and herbicides on the surface of tomato fruit and spinach leaves were studied. Samples were spiked with 100 mg/ml of lambda cyhalothrin, chlorothalonil, chlorpyriphos and pentachlorophenol standard solutions in acetone. Thy were air dried for 1 minute and exposed to light of various intensities; sunlight, 40 w, 60 w, 75 w and 100 w bulbs after spreading on the surface of spinach and tomatoes for 15, 30, 45 and 60 minutes and then washed in acetone. The pesticide concentration in the samples was analyzed with a UV Visible spectrophotometer. The rate of degradation of chlorothalonil, lambda cyhalothrin, pentachlorophenol and chlorpyriphos was also calculated and rate constants obtained for each residue. The results obtained indicated that the 100 W bulb degradation ranged from 20-95% for all the molecules in both tomato fruit and spinach leave surface. The residues breakdown followed a 1st order kinetics.

Kamau, JM, Mbui DN, Mwaniki JM, Mwaura FB.  2017.  Cow dung to kilo watt using double chamber microbial fuel cell. International Journal of Scientific Research in Science, Engineering and Technology. 3:70-79. AbstractInternational Journal of Scientific Research in Science, Engineering and Technology

In the current study, voltage is generated from cow waste at varying time duration of 6 to 11 days. PVC pipe was used to make a salt bridge using agarose and potassium chloride and Sodium chloride. The performance of microbial fuel cells was evaluated by characterizing the generated voltage, current, power and surface power density. It was observed that despite the high impedance of the substrate, all the generated parameters have shown maximum values at day 6 and then a decline in trend was observed on 7 days onwards. The highest values of voltage, current, power, current density and power density obtained were 0.5090 V, 0.28 μA, 0.0093 μW, 0.05181 mA/m2 and 0.0000006 W/m2 respectively. The study concluded that microbial fuel cells technology can be used to generate electricity from cow dung.

Masese, FA, Wandiga SO, Madadi VO, Mbui DN.  2017.  Water quality status ofselected sources of domestic water in Kenya. International Journal of Scientific Research in Science, Engineering and Technology. 3:193-198. AbstractInternational Journal of Scientific Research in Science, Engineering and Technology

In Kenya, water scarcity is a major issue due to destruction of water catchment, poor management of water supply and contamination of national water resources. The government’s long-term objective is to ensure that all citizens have access to safe drinking water. Although the government has increased the budget for improving access to water, many citizens still do not have access to potable water. The study analysed contaminants from selected sources of domestic water in the counties of Machakos, Nakuru, Kiambu and Nairobi. The following physico-chemical parameters were investigated–pH, conductivity, total suspended solids (TSS) and total dissolved solids (TDS), dissolved oxygen (DO), chemical oxygen demand (COD), anions (Cl-and PO43-), E. Coli and total coliforms. Water samples were collected from eight sampling sites in dry and wet seasons and analysed following standard methods. pH values varied from 6.3–9.1 in the dry season, and 6.9–9.5 in the wet season, conductivity from 244.0–5758.0 µS/cm in the dry season and 141.0–2004.0 µS/cm in the wet season, TDS from 113.0–5,824.0 mg/L in the dry season and 82.0–183.0 in the wet season, temperature from 24.1–25.2 C in the dry season and 25.3–25.8 C in the wet season, TSS from 0.00–0.01 mg/L in the dry season and 0.01–0.02 mg/L in the wet season, COD from 112.0–255.0 mg/L in the dry season and 90.6–154.0 mg/L in the wet season, DO varied from 2.8–4.2 mg/L in the dry season and 3.1–4.2 mg/L in the wet season, nitrates from 2.5–19.6 ppm, phosphates from 0.03–2.24 mg/L, while E. Coli varied from 13–4,300 CFU/ml. The values obtained for most parameters …


Mbui, D, Chebet E, Kamau G, Kibet J.  2016.  The state of water quality in Nairobi River, Kenya. Asian journal of Research in Chemistry. 9(11):579-586. AbstractAsian journal of Research in Chemistry

The contribution explores the most serious problem experienced globally as a consequence of environmental pollution mainly by inorganic, organic, and organometallic materials. This study was conducted to assess the physical chemical characteristics and heavy metal content in a section of Nairobi River which passes through various residential facilities. Water samples were taken twice during the dry season (June 2013) and twice during the wet season (November 2013). The water temperature, pH, dissolved oxygen (DO) and total dissolved solids (TDS) were measured in situ. Determination of heavy metals (Pb, Cu, Mn, Fe, Zn and Cr) was carried out using spectroscopic techniques whereas incubation, reactor digestion, gravimetric, amino acid, sulfaver 4, diazotization and titration methods were used to determine the levels of biochemical oxygen demand (BOD), chemical oxygen demand (COD), total …


Orata, DO, Yusuf A, Claire N, Damaris M, Mukabi M.  2014.  Surface Modified Electrodes Used in Cyclic Voltammetric Profiling of Quinine an Anti-Malarial Drug. IOSR-Journal of Applied Chemistry. 7(5):54-58.
K., MJ, Mbui DN, G.N. K.  2014.  Adsorption of Dursban (Chlorpyrifos) Pesticide by Loam soil fro Limuru, Kenya: Apparent Thermodynamic Properties. African Journal of Physical Sciences. 1(1):1-9.
Damaris, M, O. OD, Jackson GE, Kariuki DK.  2014.  Speciation of Some Heavy Metals in Ngong River using the Joint Expert Speciation System (JESS). BEST-IJHAMS. 2(10):59-70.
Ujeneza, E, Njenga HN, Mbui D, Kariuki DN.  2014.  Optimization of Acid ACtivation Conditions for Athi River Bentonite Clay and Application of the Treated Clay in Palm Oil Bleaching. IOSR-Journal of Applied Chemistry. 7(8):29-38.
N., MD, O. OD, E GJ, D.K K.  2014.  Investigation of Kenyan Bentonite in adsorption of some heavy metals in aqueous systems using Cyclic Voltammetric Techniques. International Journal of Physical Sciences. 5(9):102-108.
D, O, A Y, C N, D M, M. M.  2014.  Surface Modified Electrode Used In the Electro-analysis of N-Acetyl P-Aminophenol- A Pharmaceutical Drug. Journal of Applied Chemistry.


Milandri, S, Winter K, Mbui D, Jackson G, Chimpango S.  2012.  Perfomance of plant species in removing nutrients from storm water in biofiltration systems in Cape Town. Water SA. 38


NDUTA, DRWACHIRA-MBUIDAMARIS.  2007.  Physico-Electrochemical Assessment of Pollutants in Nairobi River. JOURNAL OF ENVIRONMENTAL CHEMISTR. : MBUI DAMARIS Abstract
This is a generalization after my work on the projective space of dimension 4 to n.



NDUTA, DRWACHIRA-MBUIDAMARIS.  2001.  Sorption and Detection of Phenolic Compounds by Rice Husk Ash from Mwea, Kenya. JOURNAL OF ENVIRONMENTAL CHEMISTR. : MBUI DAMARIS Abstract
This is a generalization after my work on the projective space of dimension 4 to n.

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