Bio

Publications


2017

Muinde, VM, Onyari JM, Wamalwa B, Wabomba J, Nthumbi RM.  2017.  Adsorption of Malachite Green from Aqueous Solutions onto Rice Husks: Kinetic and Equilibrium Studies. Journal of Environmental Protection. 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.

2015

W.O.Osawa, Sahoo PK, J.M.Onyari, F.J.Mulaa.  2015.  Effects of antioxidants on oxidation and storage stability of Croton megalocarpus biodiesel.. International Journal of Energy and Environmental Engineering. 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.  2015.  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. 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

Anzeze DA, Onyari JM, SPMGPW.  2014.  Adsorption of Pb (II) ions from aqueous solutions by water hyacinth (Eichhornia crassipes): Equilibrium and Kinetic studies,. International Journal of Environmental Pollution and Remediation. Volume 2,(DOI: 10.11159/ijepr.2014):9p.
Anzeze DA, Onyari JM, SPMGJW.  2014.  Biosorption of Zn (II) ions from aqueous solutions by water hyacinth (Eichhornia crasippes): Equilibrium and Kinetic studies,. International Journal of Innovation and Scientific Research,. Vol. 8(No. 2 Sep. 2014,):224-233.
Wanyonyi WC, Onyari JM, SPM.  2014.  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. 50:862–869.
Anzeze DA, Onyari JM, SPMGJW.  2014.  Equilibrium and Kinetics studies for the biosorption of aqueous Cd (II) ions onto Eichhornia crasippes biomass,. IOSR Journal of Applied Chemistry. Volume 7(Issue 1 Ver. II. (Feb. 2014)):29-37.
Shee Ali, Onyari JM, WJNMD.  2014.  Methylene Blue Adsorption onto Coconut husks/Polylactide Blended Films: Equilibrium and Kinetic Studies. Chemistry and Materials Research. Vol.6(No.11):28-37.
Osawa W.O, Onyari JM, SPKMFJ.  2014.  Process optimization for production of biodiesel from croton oil using two-stage process. IOSR Journal of Environmental Science, Toxicology and Food Technology. Volume 8(Issue 11 Ver. III (Nov. 2014)):49-54.
Wanyonyi WC, Onyari JM, SPMMFJ.  2014.  Enzymatic Decolorization of Malachite Green Dye by a Newly Isolated Bacillus Cereus Strain wwcp1. IOSR Journal of Environmental Science, Toxicology and Food Technology. Vol 8(Issue 12 Ver. III (Dec. 2014)):58-64..

2013

2012

David M. Maina, Lydia W. Njenga, John M. Onyari, Kyalo BN.  2012.  Trace Element Concentrations in Some Traditional Diets Consumed in Selected Parts of Eastern Province of Kenya. Journal of Environmental Protection. 3
Teshome, 3. A, Fritz Vollrath, Suresh K. Raina, J.M. Kabaru, Onyari J.  2012.  Study on the microstructure of African wild silk cocoon shells and fibers. Journal of Biological Macromolecules. 50 :63–68.
Addis Teshome, Onyari JM, Raina SK, Jacques M. Kabaru, Fritz Vollrath, Suresh K. Raina.  2012.  Mechanical and Thermal Degradation Properties of Silk from African Wild Silkmoths. J. APPL. POLYM. SCI. (DOI: 10.1002/APP.37873):5-15.
Harry Amuguni Chanzu • John Mmari Onyari, Shiundu PM.  2012.  ), Biosorption of Malachite Green from Aqueous Solutions onto Polylactide/Spent Brewery Grains Films: Kinetic and Equilibrium Studies. J Polym Environ. DOI 10.1007/s10924-012-0479-5

2011

Teshome A, Raina SK, Vollrath F, Kabaru JM, Onyari J, EK N, Nguku.  2011.  Study on weight loss and moisture regain of Silk Cocoon shells and Degummed Fibers from African Wild Silkmoths. Journal of Entomology . 8(5):450-458.
Maube OM, Nyang’aya JA, JM, Onyari.  2011.  Evaluation of Chemical and Physical Properties of Biodiesel Produced from Used Edible Vegetable Oil. Journal of Agriculture, Pure and Applied Science and Technology. (ISSN 2073-8749):14p.
Kimilu R.K, Nyang’aya J.A, Onyari JM.  2011.  The effect of Temperature and blending on the specific gravity and viscosity of Jatropha Methyl ester. Journal of Engineering and Applied Sciences. 6(12):97-105.

2010

Nguta, CM, WO O, Onyari, Onyiego.  2010.  ). Levels of Selected Heavy Metals & Fluoride in water around Fluorspar Factory in Kerio Valley, Kenya. Kenya J Sci Tech Inn. . 1:12-22.
Dharani N, Onyari JM, Kinyamario JI, Maina, Mavuti.  2010.  Distribution of Cd and Zn levels in Soils and Acacia xanthophloea Benth. From Lake Nakuru National Park, Kenya. Bulletin of Environmental Contamination and Toxicology. 85(3):318-323.

2009

Nyunja, J, Ntiba M, Onyari J, Mavuti K, Soetaert K, Bouillon S.  2009.  Autotrophic carbon sources for fish communities in a tropical coastal ecosystem (Gazi bay, Kenya). Website
Nyunja, J, M. Ntiba, J. Onyari, K. Mavuti, Bouillon S.  2009.  Carbon sources supporting a diverse fish community in a tropical coastal ecosystem (Gazi Bay, Kenya). Estuarine, Coastal and Shelf Science. 83(3):265-378.
Onyari, JM, Huang SJ.  2009.  Synthesis and Properties of Novel Polyvinyl alcohol-Lactic acid Gels. Journal of Applied Polymer Science . 113:2053-2061.

2008

JM, O, Mulaa F, J M, P S.  2008.  Biodegradability of PLA, Preparation and Properties of PLA/Gum Blends. Journal of Polymers and the Environment. 16:205-212.

2007

Dharani N, JM O, DM M.  2007.  The Distribution of Cu and Pb Levels in soils and Acacia xanthoploea Benth. From Lake Nakuru National Park Kenya. Bulletin Environmental Contamination and Toxicology. 79(2):172-177.

2006

Dharani N, Kinyamario JI, JM O.  2006.  Structure and Composition of Acacia xanthophloea woodland in Lake Nakuru National Park, Kenya. Africa Journal of Ecology . 44(4):523-530.

2003

M, DRONYARIJOHN.  2003.  Heavy Metals in sediments from Makupa and Port-Reitz creek systems: Kenyan Coast ,. Adsorption Science Technology , 21 (3), 269-283. : University of Nairobi Press Abstract
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M, DRONYARIJOHN.  2003.  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,. Adsorption Science Technology , 21 (3), 269-283. : University of Nairobi Press Abstract
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M, DRONYARIJOHN.  2003.  Heavy metal distribution in surface sediments from Mtwapa and Shirazi Creeks, Kenyan coast, Bulletin Environmental Contamination and Toxicology , 70, 1220-1227. From Sessional Paper No.10 to Structural Adjustment: Towards Indigenising the Policy Debate. The Regal Press Kenya.. : University of Nairobi Press 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.  2003.  Preparation and Mechanical Properies of PCLCellulose polymer blends , 9 th NAPRECA Symposium proceedings , August, pp 70-74.. From Sessional Paper No.10 to Structural Adjustment: Towards Indigenising the Policy Debate. The Regal Press Kenya.. : University of Nairobi Press 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.  2003.  Triblock copolymers of lactide with poly(ethylene glycol) and Influence of stereochemical composition, Macromolecular Symposia , Vol 193,1, pp 143-158. From Sessional Paper No.10 to Structural Adjustment: Towards Indigenising the Policy Debate. The Regal Press Kenya.. : University of Nairobi Press 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

1996

JM, O.  1996.  Multi-component polymers containing polylactic acid. (Prof Sam J Huang, Ed.)., Storrs, Connecticut, USA: University of Connecticut, Institute of Materials Science,
Munyua JM, OJM.  1996.  Introduction to Environmental Management,. :125pages.: Jomo Kenyatta Foundation

1995

Huang SJ, OJM.  1995.  Multi-component comb shaped and networks containing poly(lactic acid). Polym.Mat.Sci.Eng.,. 72((1)):137.

1991

and Onyari JM, WSONJO.  1991.  Lead contamination in street soils of Nairobi city and Mombasa island,. , Bull. Environ. Contam. Toxicol., . 46:782-789.

1989

and SO, OJMW.  1989.  Distribution of Cr, Pb, Cd, Zn, Fe and Mn in Lake Victoria sediments, East Africa,. Bull. Environ. Contam. Toxicol., . 42:807-813.

1987

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