Publications

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2017
Muinde VM, Onyari JM, Wamalwa B, Wabomba J, Nthumbi RM. "Adsorption of Malachite Green from Aqueous Solutions onto Rice Husks: Kinetic and Equilibrium Studies." Journal of Environmental Protection. 2017;8(03):215. AbstractWebsite

A study was done to evaluate the removal of a cationic dye from simulated waste water onto rice husks (RH). Spectroscopic methods such as FTIR and SEM/EDX were used for adsorbent characterization. Experimental dependency on solution pH, initial dye concentration, agitation speed, adsorbentparticle size, temperature of the solution and contact time was evaluated. The adsorption data was tested using both Langmuir and Freundlich isotherms. The data fitted well into Langmuir isotherm model with a monolayer adsorption capacity of 6.5 mg/g. Further, the separation factor (RL) value was less than unity indicating a favorable adsorption process. Adsorption kinetics was determined using pseudo-first-order, pseudo-second-order and intra-particle diffusion models. The results showed that the adsorption of malachite green onto rice husks followed pseudo-second-order model with a determination coefficient of 0.986. This work has revealed that rice husks have a great potential to sequester cationic dyes from aqueous solutions and therefore it can be utilized to clean contaminated effluents.

Mureithi AW, Onyari JM, Wanyonyi WC, Mulaa FJ. "Amino acid Composition of Gelatin Extracted from the Scales of Different Marine Fish Species in Kenya.". 2017. AbstractFull text link

Gelatin in this study was extracted by an enzymatic process from the scales of three marine fish species; Lutjanus
sebea (Red snapper), Lethrinus harak (Black spot emperor) and Scalus ghobban (Blue barred parrot fish).
Concentration of bacteria for mass production of enzyme was done in a fermentation medium using a bio reactor.
Scales were hydrolyzed at 500C and the pH maintained at 12. Complete hydrolysis took between 20 and 23 days for
all species. The yield for the dried gelatin was between 28.2% and 41.4% for the marine fish scales under study.
Fourier transform infrared spectra showed the presence of amide bands and two other additional absorption bands,
indicating the presence of amide bonds for all the three species. The amino acid composition analysis for the gelatin
of three species was then done showing the presence of 16 amino acids. Glycine was the most abundant for all the
three species with about 35% followed by Alanine both adding up to around 50% of the total amino acid
compositions. The amount of Proline was high for red snapper at over 14.2% compared to 11.1% and 11.6% for
blue barred parrot fish and black spot emperor respectively.

Wanyonyi WC, Onyari JM, Shiundu PM, Mulaa FJ. "Biodegradation and Detoxification of Malachite Green Dye Using Novel Enzymes from Bacillus cereus Strain KM201428: Kinetic and Metabolite Analysis.". 2017. AbstractFull text link

Enzyme based degradation of organic pollutants is a promising detoxifying approach due to the promiscuous nature of the enzyme, efficiency, cost effective and ecofriendly. In the present study, we have carried out detailed decoloration and degradation studies on a model triphenyl methane group of dyes (Malachite Green dye (MG)) using a newly isolated enzyme from Bacillus cereus KM201428 under the static condition. Biodegradation of dyes was monitored by UV-VIS spectrophotometer and the resultant metabolites analyzed by Liquid Chromatography–Hybrid Quadrupole Time of Flight Mass Spectrometry (LC–QToF-MS) and Gas Chromatography/Mass Spectrometry (GC - MS). Metabolite analysis results revealed that enzymatic degradation of MG dye resulted in complete mineralization and benzene ring-removal; the latter known for organic dye toxicity. Kinetic study results revealed that first-order kinetic model was best applicable for describing MG dye decoloration. Michaelise-Menten kinetics, Lineweaver–Burk plot and Eadie-Hofstee plot models were used to establish the kinetic parameters for the dye decoloration. Lineweaver–Burk plot provided the best theoretical correlation of the experimental data with maximum rate (Vmax) of 17.70 mg l-1h-1 and Michaelis constant (Km) of 124 mgl-1. Results provide evidence that crude enzyme from Bacillus cereus strain KM201428 offers an effective, renewable, ecofriendly and affordable biotechnology for treatment of industrial effluents polluted with organic dye.

Mwaguni S, Ayiemba E, Onyari J. "DANCING TO THE TUNE OF OPPORTUNITIES –HUMAN SETTLEMENTS ALIGNED TO SHARE THE JACKPOT OF KENYA’S COASTAL TOURISM BENEFITS SPOIL THE BROTH.". 2017. AbstractFull text link

This paper highlights how human settlements aligned themselves to share the benefits to arise from coastal tourism development in
the Kenya coast, but have come to bedevil the industry through poor management of domestic waste. The study area comprised of
Nyali-Bamburi-Shanzu and Diani-Chale, which are two important tourist destinations in the country. It attempted to establish
population numbers in these habitations, the waste loads generated, and how it was managed. The study was accomplished through
field visits, library research and application of the World Health Organization (WHO 1989) rapid assessment methods for land, air
and water pollution. The relevant data for assessment was obtained from records of population census, bed nights, occupancy, and the
waste disposal methods in use. The study revealed that human settlements aligned themselves in clusters inland, reflecting the clusters
of the beach hotels dotting the shore line of the Indian Ocean. Large volumes of domestic waste were being generated in both the
human settlements and in the hotels. Management of the waste in the settlements was largely on-site and mixed, through the use of
both pit latrines and septic-tank/soakage pit systems in the human settlements, and only through septic-tank/soakage pits in the hotel
establishments. None of the settlements had wastewater treatment facilities. Only 5 beach hotels had wastewater treatment plants.
While the settlements positioned themselves to benefit from the tourism industry, tapping in business and employment opportunities,
the arrangement has seemed to spoil the broth as the settlements came to be the main source domestic waste affecting environmental
quality and undermining tourism growth and sustainability. Also, through the large number of visitors, during the peak tourist periods,
the beach hotels themselves have come contribute to large waste generation. On-site sanitation, it is concluded, is not appropriate for
managing domestic waste in coastal areas dependent on good quality environmental to flourish the tourism economic sector. Tourism
thrives in areas where the environment is aesthetically appealing; domestic waste undermine. Consequently, it is recommended that
innovative approaches are pursued for domestic waste management in order to flourish and sustain the industry.

Wabomba JN, Shiundu PM, Onyari JM, Yanful E. "Equilibrium and Kinetic Studies of Cu(Ii) Removal from Aqueous Solutions Using a Kenyan Micaceous Mineral.". 2017. AbstractFull text link

Copper (II) sorption on a Kenyan micaceous mineral (Mica-K) was studied in the batch mode. The effects of different experimental parameters such as; initial concentration, contact time, sorbent dose, pH, particle size, agitation speed, competition and temperature on the kinetics of copper removal were studied. The sorption pattern of copper onto Mica-K followed Langmuir and Freundlich isotherms. Thermodynamic parameters for copper sorption on Mica-K were also determined. X-ray photoelectron spectroscopic (XPS) analysis of metal ion-equilibrated Mica-K, demonstrated that copper, cadmium and Zinc containing nodules existed on the surface of Mica-K.

2015
W.O.Osawa, Sahoo PK, J.M.Onyari, F.J.Mulaa. "Effects of antioxidants on oxidation and storage stability of Croton megalocarpus biodiesel." International Journal of Energy and Environmental Engineering. 2015. Abstractart3a10.10072fs40095-015-0191-z.pdf

The effects of antioxidants and storage on
oxidation stability of croton biodiesel and its blends with
petro-diesel were determined using PetroOxy equipment.
The biodiesel and blends were kept in Pyrex reagent bottles
and stored in a metallic locker at room temperature for
8 weeks, a condition that imitated ordinary storage environment
in tanks before use. The oxidation stability indices
of the biodiesel and blends were determined by measuring
Rancimat induction periods for 8 weeks at intervals of
2 weeks. Although the Rancimat induction period for
freshly prepared biodiesel of 4 h was higher than the
commonly used American standard (ASTM D6751) limit
of 3 h, it was lower than the European standard (EN 14214)
of 6 h. The induction periods of B50 and lower blends
were, however, equal to or greater than 6 h. The Rancimat
induction periods for biodiesel with 100 ppm antioxidants
were 5.6, 6.8 and 7.8 h for Butylated hydroxyanisol
(BHA), Propyl gallate (PRG) and Pyrogallol (PYG),
respectively, while the Rancimat induction periods for
biodiesel with 1000 ppm antioxidants were 6.8, 8.2 and
10 h for BHA, PRG and PYG, respectively. The oxidation
stability index for neat biodiesel decreased by 45 % while
that for biodiesel with 1000 ppm antioxidants depreciated
by 16, 12.2 and 20.59 % for PYG, PRG and BHA,
respectively, during the 8-week storage period. A more
rapid decline in oxidation stability was observed in the
biodiesel and blends without antioxidants than those with
antioxidants. The results from this study showed that the
use of appropriate concentrations of suitable antioxidants
can greatly improve the oxidation stability of biodiesel and
blends which can therefore be stored over longer periods of
time before use without undergoing extensive and deleterious
oxidative deterioration.
Keywords Croton biodiesel Oxidation stability
Antioxidants Storage stability
A

Osawa WO, Sahoo FK, Onyari J, Mulaa F. "Experimental Investigation on performance,emission and combustion characteristics of Croton Megalocarpus of Biodiesel Blends in a Direct injection Diesel Engine." International Journal of Science and International Technology. 2015;4(1):26-33. Abstract6488141691776.pdf

The emission, performance and combustion characteristics of croton biodiesel blends were tested in a direct injection (DI) single
cylinder four stroke diesel engine. The physico-chemical properties of the biodiesel blends were all found to be within the standard
ASTM values. The reduction in exhaust smoke emissions for the biodiesel blends ranged from 10% to 41% at maximum engine load
of 10 Kg while a slight increase in NOx emissions was observed with increase in concentration of biodiesel in the blends. Similar
general increase in brake thermal efficiency (BTE), temperature of exhaust emissions and fuel flow rate was observed with increasing
engine load for both petro-diesel and biodiesel blends. The difference between BTE for petro-diesel and biodiesel blends ranged from
2.04 to 5.03%. The brake specific energy consumption (BSEC) decreased with increasing engine load for both petro-diesel and
biodiesel blends. An increase in both engine pressure and heat released was observed with increase in concentration of biodiesel in the
blends. The difference in maximum engine pressure ranged from 1.05 bar at 0 Kg to 3.77 bar at 10 Kg load. The greatest difference in
maximum engine pressure was recorded between petro-diesel and B50 blend. The observed difference in position of peaks for
maximum heat released showed that there was slight delay in ignition of biodiesel blends as compared to petro-diesel. The results
obtained in this study showed that higher blends of up to 50% biodiesel can be effectively used as an alternative to petro-diesel without
compromising the engine performance.
Key words:Croton biodiesel blends, Diesel engine, Emission and performance characteristics.

2014
Wanyonyi WC, Onyari JM SPM. "Adsorption of Congo Red Dye from Aqueous Solutions Using Roots of Eichhornia crassipes: Kinetic and Equilibrium Studies." The International Conference on Technologies and Materials for Renewable Energy, Environment and Sustainability, TMREES14, Energy Procedia. 2014;50:862-869.
Anzeze DA, Onyari JM SPMGPW. "Adsorption of Pb (II) ions from aqueous solutions by water hyacinth (Eichhornia crassipes): Equilibrium and Kinetic studies,." International Journal of Environmental Pollution and Remediation. 2014;Volume 2,(DOI: 10.11159/ijepr.2014):9p.
Anzeze DA, Onyari JM SPMGJW. "Biosorption of Zn (II) ions from aqueous solutions by water hyacinth (Eichhornia crasippes): Equilibrium and Kinetic studies,." International Journal of Innovation and Scientific Research,. 2014;Vol. 8(No. 2 Sep. 2014,):224-233.
Wanyonyi WC, Onyari JM SPMMFJ. "Enzymatic Decolorization of Malachite Green Dye by a Newly Isolated Bacillus Cereus Strain wwcp1." IOSR Journal of Environmental Science, Toxicology and Food Technology. 2014;Vol 8(Issue 12 Ver. III (Dec. 2014)):58-64.
Anzeze DA, Onyari JM SPMGJW. "Equilibrium and Kinetics studies for the biosorption of aqueous Cd (II) ions onto Eichhornia crasippes biomass,." IOSR Journal of Applied Chemistry. 2014;Volume 7(Issue 1 Ver. II. (Feb. 2014)):29-37.
Shee Ali, Onyari JM WJNMD. "Methylene Blue Adsorption onto Coconut husks/Polylactide Blended Films: Equilibrium and Kinetic Studies." Chemistry and Materials Research. 2014;Vol.6(No.11):28-37.
Osawa W.O, Onyari JM SPKMFJ. "Process optimization for production of biodiesel from croton oil using two-stage process." IOSR Journal of Environmental Science, Toxicology and Food Technology. 2014;Volume 8(Issue 11 Ver. III (Nov. 2014)):49-54.
2013
Onyari JM, Addis Teshome, Suresh K. Raina, Kabaru JM, Fritz Vollrath, Suresh K. Raina. "Mechanical and thermal degradation properties of silk from African wild silkmoths.". 2013. AbstractFull text link

Variations among silk of four African wild silkmoths, Argema mimosae, Anaphe panda, Gonometa postica, and Epiphora bauhiniae, was studied regarding their mechanical properties and thermal degradation behaviors. Cocoon shells and individual degummed fibers were examined using tensile testing, thermogravimetric analysis, and scanning electron microscope (SEM). A. mimosae and G. postica cocoon shells had marginally higher initial moduli and strains at maximum stress. The stress–strain curves of Bobmyx mori and A. panda degummed fibers lacked clear yielding points. G. postica fibers had the highest breaking energy (76.4 J/cm3) and breaking strain (41.3%). The ultimate tensile strength was the highest for B. mori (427 MPa). Fiber pull-out and detachment was predominant in fracture surfaces of both the cocoon shells and the fibers. Wild cocoon shells and degummed fibers had higher temperature for dehydration loss than B. mori. A. mimosae fibers (11.9%) and G. postica cocoon shells (13.3 %) had the highest weight loss due to dehydration. E. bauhinae cocoon shells and B. mori fibers had the highest total weight losses of 97.2 and 93.4%, respectively. The African silks exhibited variations in their mechanical and thermal degradation properties related to their physical and chemical structure and composition. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

2012
Harry Amuguni Chanzu • John Mmari Onyari, Shiundu PM. "), Biosorption of Malachite Green from Aqueous Solutions onto Polylactide/Spent Brewery Grains Films: Kinetic and Equilibrium Studies." J Polym Environ. 2012;DOI 10.1007/s10924-012-0479-5.
Addis Teshome, Onyari JM, Raina SK, Jacques M. Kabaru, Fritz Vollrath, Suresh K. Raina. "Mechanical and Thermal Degradation Properties of Silk from African Wild Silkmoths." J. APPL. POLYM. SCI. 2012;(DOI: 10.1002/APP.37873):5-15.
Teshome 3. A, Fritz Vollrath, Suresh K. Raina, J.M. Kabaru, Onyari J. "Study on the microstructure of African wild silk cocoon shells and fibers." Journal of Biological Macromolecules. 2012;50 :63-68.
David M. Maina, Lydia W. Njenga, John M. Onyari, Kyalo BN. "Trace Element Concentrations in Some Traditional Diets Consumed in Selected Parts of Eastern Province of Kenya." Journal of Environmental Protection. 2012;3.
2011
Kimilu R.K, Nyang’aya J.A, Onyari JM. "The effect of Temperature and blending on the specific gravity and viscosity of Jatropha Methyl ester." Journal of Engineering and Applied Sciences. 2011;6(12):97-105.
Maube OM, Nyang’aya JA, JM, Onyari. "Evaluation of Chemical and Physical Properties of Biodiesel Produced from Used Edible Vegetable Oil." Journal of Agriculture, Pure and Applied Science and Technology. 2011;(ISSN 2073-8749):14p.
Teshome A, Raina SK, Vollrath F, Kabaru JM, Onyari J, EK N, Nguku. "Study on weight loss and moisture regain of Silk Cocoon shells and Degummed Fibers from African Wild Silkmoths." Journal of Entomology . 2011;8(5):450-458.
Nyatebe JO, Njenga GK, Wandiga SO, Orata F, Oduor FDO, Onyari JM. "A survey of heavy metal pollution from automotive emmissions in Kenya's urban Environment.". 2011.Full text link
2010
Nguta, CM, WO O, Onyari, Onyiego. "). Levels of Selected Heavy Metals & Fluoride in water around Fluorspar Factory in Kerio Valley, Kenya." Kenya J Sci Tech Inn. . 2010;1:12-22.
Dharani N, Onyari JM, Kinyamario JI, Maina, Mavuti. "Distribution of Cd and Zn levels in Soils and Acacia xanthophloea Benth. From Lake Nakuru National Park, Kenya." Bulletin of Environmental Contamination and Toxicology. 2010;85(3):318-323.
2009
Nyunja J, Ntiba M, Onyari J, Mavuti K, Soetaert K, Bouillon S. "Autotrophic carbon sources for fish communities in a tropical coastal ecosystem (Gazi bay, Kenya).". 2009.Website
Nyunja J, M. Ntiba, J. Onyari, K. Mavuti, Bouillon S. "Carbon sources supporting a diverse fish community in a tropical coastal ecosystem (Gazi Bay, Kenya)." Estuarine, Coastal and Shelf Science. 2009;83(3):265-378 .
Onyari JM, Huang SJ. "Synthesis and Properties of Novel Polyvinyl alcohol-Lactic acid Gels." Journal of Applied Polymer Science . 2009;113:2053-2061.
2008
JM O, Mulaa F, J M, P S. "Biodegradability of PLA, Preparation and Properties of PLA/Gum Blends." Journal of Polymers and the Environment. 2008;16:205-212.
2007
Dharani N, JM O, DM M. "The Distribution of Cu and Pb Levels in soils and Acacia xanthoploea Benth. From Lake Nakuru National Park Kenya." Bulletin Environmental Contamination and Toxicology. 2007;79(2):172-177.
2006
2003
M DRONYARIJOHN. "Attahiru S, Shiundu PM, Onyari JM and Mathu EM (2003), Removal of Cu (II) from an aqueous solution using a micaceous mineral of Kenyan origin,.". In: Adsorption Science Technology , 21 (3), 269-283. University of Nairobi Press; 2003. Abstract
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M DRONYARIJOHN. "Heavy metal distribution in surface sediments from Mtwapa and Shirazi Creeks, Kenyan coast, Bulletin Environmental Contamination and Toxicology , 70, 1220-1227.". In: From Sessional Paper No.10 to Structural Adjustment: Towards Indigenising the Policy Debate. The Regal Press Kenya. University of Nairobi Press; 2003. Abstract
Staphylococcus aureus strains were isolated from 183 of 300 raw milk samples collected at the Kenya Cooperative Creamery (Dandora). Ninety seven percent of the 183 strains isolated  were assayed for the production of enterotoxin A, B, C and D. Seventy two (74.2 %) of these were found to produce either a single or a combination of enterotoxins. Raw milk is a potential source of enterotoxigenic S. aureus in milk and milk products especially if there is defective pasteurization.
M DRONYARIJOHN. "Heavy Metals in sediments from Makupa and Port-Reitz creek systems: Kenyan Coast ,.". In: Adsorption Science Technology , 21 (3), 269-283. University of Nairobi Press; 2003. Abstract
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M DRONYARIJOHN. "Preparation and Mechanical Properies of PCLCellulose polymer blends , 9 th NAPRECA Symposium proceedings , August, pp 70-74.". In: From Sessional Paper No.10 to Structural Adjustment: Towards Indigenising the Policy Debate. The Regal Press Kenya. University of Nairobi Press; 2003. Abstract
Staphylococcus aureus strains were isolated from 183 of 300 raw milk samples collected at the Kenya Cooperative Creamery (Dandora). Ninety seven percent of the 183 strains isolated  were assayed for the production of enterotoxin A, B, C and D. Seventy two (74.2 %) of these were found to produce either a single or a combination of enterotoxins. Raw milk is a potential source of enterotoxigenic S. aureus in milk and milk products especially if there is defective pasteurization.
M DRONYARIJOHN. "Triblock copolymers of lactide with poly(ethylene glycol) and Influence of stereochemical composition, Macromolecular Symposia , Vol 193,1, pp 143-158.". In: From Sessional Paper No.10 to Structural Adjustment: Towards Indigenising the Policy Debate. The Regal Press Kenya. University of Nairobi Press; 2003. Abstract
Staphylococcus aureus strains were isolated from 183 of 300 raw milk samples collected at the Kenya Cooperative Creamery (Dandora). Ninety seven percent of the 183 strains isolated  were assayed for the production of enterotoxin A, B, C and D. Seventy two (74.2 %) of these were found to produce either a single or a combination of enterotoxins. Raw milk is a potential source of enterotoxigenic S. aureus in milk and milk products especially if there is defective pasteurization.
2001
1997
1996
Munyua JM OJM. "Introduction to Environmental Management,." Jomo Kenyatta Foundation; 1996:.
JM O. Multi-component polymers containing polylactic acid. Huang PSJ, ed. Storrs, Connecticut, USA: University of Connecticut, Institute of Materials Science, ; 1996.
1995
Huang SJ OJM. "Multi-component comb shaped and networks containing poly(lactic acid)." Polym.Mat.Sci.Eng.,. 1995;72((1)):137.
1991
and Onyari JM WSONJO. "Lead contamination in street soils of Nairobi city and Mombasa island,." , Bull. Environ. Contam. Toxicol., . 1991;46:782-789.
1989
and SO OJMW. "Distribution of Cr, Pb, Cd, Zn, Fe and Mn in Lake Victoria sediments, East Africa,." Bull. Environ. Contam. Toxicol., . 1989;42:807-813.
1987
1986
Onyari JM. "The need for aquatic pollution studies in Kenyan inland waters.". 1986. AbstractThe need for aquatic pollution studies in Kenyan inland waters

The need for baseline data on pollution studies to the aquatic biota of Kenyan Inland waters is of profound importance. Aware of the possible contamination of the rivers and Lakes with heavy metals, pesticides and other pollutants used around them for the control of tropical diseases and treatment of agricultural crops, a monitoring programme is necessary.

1985
Onyari JM. "The concentrations of Mn.". 1985.Website
1983
Onyari JM. "A review of the biology of tilapia species in Lake Victoria with special reference to its feeding and breeding habits.". 1983. AbstractFull text link

A review of the biology of tilapia species in Lake Victoria with special reference to its feeding and breeding habits

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