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Browsing by Author "Mbuvi, Harun M."

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Biodegradable Superabsorbent Hydrogel from Activated Hydrochar-Glycerol Cross-linked with Maleic Acid
(American Journal of Polymer Science, 2025-08) Mukulu, Stanley M.; Mbuvi, Harun M.; Kasimu, Titus M.; Maingi, Francis
Superabsorbent hydrogels are polymer materials with a three-dimensional structure. They have the potential to absorb large amounts of water or aqueous solutions due to the presence of hydrophilic functional groups in their network structures. The increasing population, coupled with advanced technologies, has led to a fourfold increase in demand in industrial applications, technological fields, medical fields, and agriculture. This study reports on the synthesis and characterization of superabsorbent hydrogels derived from activated hydrochar. The preparation of hydrochar was done via the dehydration process of sugarcane bagasse, followed by activation using acidified potassium permanganate to form activated hydrochar (AH). The AH was then reacted with glycerol to form polymer units (AHGL). The polymeric units were then reacted with maleic acid to form a superabsorbent hydrogel (SAH). Characterization of the synthesized SAH was carried out using FT-IR, SEM, and XRD. The swelling capacity was optimized by varying contact time and doses of both glycerol and maleic acid. The FT-IR spectra showed a C=O carbonyl spectral absorption peak at 1711.85 cm⁻¹ in SAH, indicating successful crosslinking. The XRD analysis portrayed the amorphous nature of hydrochar and AH, while AHGL and SAH showed semi-crystalline and crystalline nature, respectively. SEM analysis showed dense porous surfaces in SAH compared to rigid surfaces with fewer and unevenly distributed pores in AHGL. The gravimetric technique showed that the maximum absorption capacity of the SAH was obtained at the optimum reaction mole ratio of AH:GL:MA of 10:4:1. The maximum absorption capacity of the synthesized superabsorbent hydrogel relative to its dry mass was found to be 905% and was achieved in a period of 8 hours. Crosslinking the hydrogel improved the water absorption capacity, and hence, it has potential application in agriculture in arid and semi-arid regions.
Capacities and efficiencies of electrospun titania nanofibers in removing organic dyes and pesticides from contaminated water
(2014-07-28) Chepngetich, Josphine; Mbuvi, Harun M.
The release of organic dyes and pesticides into water bodies by paint factories and flower farms results in the degradation of both water quality and aquatic life. A complete water treatment system may consist of the application of a number of physical, chemical and biological processes to the waste water. These current water treatments are ineffective in completely removing pollutants; they are not accessible to rural majority facing the challenge of access to clean drinking water, beyond reach to most consumers and cannot be recycled. This work describes the use of nanotechnology in water treatment and environmental remediation. We exploit the use of titaniananofibers as the remediation agent because of its high reduction and oxidation potentials. The high redox potentials can reduce or oxidize any organic and pesticides present in polluted water under sunlight irradiation. The titaniananofibers will be prepared by electro spinning process of titania precursors dissolved in a suitable polymer followed by calcinations. Titanium dioxide fibers will be characterized for morphology and structure by Scanning Electron Microscopy and aspect ratio by Branuer-Emmet-Teller (BET) analysis. UV-visible spectroscopy and high performance liquid chromatography is used to monitor the rate of photodegradation and their products respectively. The developed technique can be used in rural areas and small scale industries to treat water before releasing it to the environment.
Comparative Studies of four Parametric Models for Potassium Adsorption in Soils of Nyamira County, Kenya
(2013-11) Mbuvi, Harun M.; Kenyanya, O; Muthengia, J.M; Omayo, E.K
Determination of Potassium Levels in Intensive Subsistence Agricultural Soils in Nyamira County, Kenya
(2013-10-15) Mbuvi, Harun M.; Kenyanya, Omanga; Muthengia, J. W.
Assessment of potassium levels in agricultural soils ofNyamira County, Kenya wasnecessitated by the observed progressive drops in maize acreage yields over the years despite use of phosphorus and nitrogenousfertilizers. In the study,concentration levels of potassium and other soil fertility indices such as, organic carbon, cation exchange capacity, exchangeable cations, soil pH, available nitrogen, total and available phosphorus were determined. Five composite soil samples were collected at depths of between 0-30 cm from five farms that have consistently been under intensive cultivation. Fractionation of potassium was achieved by sequential extraction of soil sampleswith distilled water, ammonium acetate and nitric acid in that order. Concentration levels of potassium in the extracts were determined using a flame photometer. Potassium concentration levels obtained from the water soluble soil extracts were used to calculate thermodynamic parameters such as free energy of replacement, potassium activity ratio and ionic strength of the soil solution.The relationship between the adsorbed and equilibrium potassium concentration, quantity/intensity was determined by plotting Freundlich adsorption isotherms.The isotherm was used todeterminethe buffering capacity ofpotassium and the concentration levels of potassium adsorbed on un-specific sites in the soil. The suitability of the adsorption equation was determined by applying the least square regression analysis.From the study available potassium in the soilsranged from 57 to 70 mg/kg and had amean value of 60±5.54.2 mg/kg (ammonium acetate method). The water soluble potassium ranged from 1.8 to 2.2 mg/kg with a mean of 2.02±0.16 mg/kg. Nitric acid extracted potassium had a mean of 149.±2.306 mg/kg. The mean free energy of replacement,∆F,was found to be -3572±44.98 cal/molindicating that the soils have low supplying power of potassium. The potassium buffering capacity of the soils was found to have a mean of 1.189±0.06 mg/kg. The amount of potassium adsorbed on un-specific sites of the soilshad a mean value of 6.993±2.378 L/kg. These findingsreveal the extent of potassium depletionin the soils ofthisregion andwill form a baseline for working acreage potassium doses required for remediation. Key words: potassium buffering capacity, adsorption, Freundlich isotherm, thermodynamics parameters, free energy of replacement, soil fertility indices
Effect of Potassium Dosage on Selected Growth Parameters and Yield Response Modeling on Potatoes Grown in Molo, Kenya
(Update Publishing House, 2020) Maingi, Francis M.; Mbuvi, Harun M.
The Molo region of Kenya has experienced decreased potato acreage yields over the years. This has impacted negatively economic endeavors and food security of the region and Kenya at large. A preliminary study on the physical-chemical characterization of the soils indicated that they were deficient in the amount of available potassium. This finding was very important because the majority of the farmers in the region replenish phosphorous and nitrogen but not potassium. Subsequently, the present study was undertaken to determine the effect of replenishing selected farm soils with various potassium levels on the growth and productivity of ‘Shangi’ a variety grown in Molo Sub-county and ultimately determine the soil optimum potassium dose requirement. A field experiment was conducted with seven model-based K fertilizer treatments (0, 33.3, 41.5, 55.3, 133.3, 200 and 266.7 kg K2 O/ha) and three replications in Randomized Complete Block Design (RCBD). The potassium sorption study was conducted using soil samples as adsorbent while varying the K+ concentration in solution. The data obtained were treated using both linearized and non-linearized Freundlich adsorption isotherms. The optimum potassium fertilizer rate was evaluated using yield response models (Quadratic, linear-plateau, quadratic-plateau, and square root). The results of the study showed that the increase in soil potassium levels led to a significant increase in growth and yield parameters. Aerial stem number, leaf number per plant, and plant height recorded increase with an increase in K levels. The sorption data were found to fit best in linearized Freundlich isotherm based on correlation coefficient values (R2 ) and error function analysis. The potassium buffering capacity ranged from 13.667-46.068 with a mean of 33.6 ± 17.4mg/Kg. The quadratic model fitted the data better than other models with R2 (0.9559) and SSE (18.237). K2 O fertilizer application at 200 Kg/ha maximized the potato tuber yield to 30.111 Ton/ha. The result showed clearly that there is a need to adopt the use of potassium-based fertilizer according to soil requirements in this region to realize good tuber yield.
Lead, Cadmium and Zinc speciation in Garage Soils, their Levels in Kales and Water along Katothyani Stream, Machakos Town, Kenya
(2014-02-24) Mutua, Simon Mutuku; Murungi, J.; Mbuvi, Harun M.
Garage waste is a major source of environmental pollution since it contains heavy metals. These heavy metals end up being swept by rain water into rivers. When the water is used for drinking or irrigation the heavy metals end up in animal and human tissues causing adverse health effects. In soil, heavy metals exist in different forms which influence their mobility and bioavailability. These forms include those soluble in water, those exchangeable with other metal ions, the reducible forms (carbonate and oxides), and the oxidisable forms (or-ganic and residual).The water soluble and the exchangeable forms are the most mobile and bioavailable while the oxidisable forms are the least mobile. In Machakos town Kenya, there are many garages situated next to each other and at close intervals. The waste from these ga-rages is swept by rain water to the recipient katothyani stream which is only 50 metres away. Water from this stream is used for irrigation and drinking hence posing as health risk to the community. The objective of the present study was to determine forms of Pb, Zn and Cd in garage soils of Machakos town and levels in the nearby Katothyani stream water and kales by Atomic absorption spectrometry. Nine composite soil samples each made of three replicates from depth intervals of 0-15, 15-30 and 30-60 cm of Kaunda, Industrial area and Mwangi sites were collected by stratified random sampling and extracted sequentially to determine forms. Forms of Pb and Zn were mainly oxides and organic type. The water soluble and ex-changeable fractions were associated with the garage soils at relatively low concentrations with Pb and Zn in these forms contributing less than 5% and 2.6% respectively of the total of each metal extracted. Total heavy metal concentrations (ppm) in soils ranged between 1.61±0.02 to 69.19±0.14 for Pb, 1.61±0.02 to 11.51±0.01 for Zn and Cd was below detection limit. The mobility factors of lead in the top soil profiles ranged between 4.20% and 10.69% while those of zinc were between 9.20 % and 15.71%. Levels of the metals in Katothyani stream obtained by random sampling and irrigated kales obtained purposively were also de-termined. In kales the highest mean concentrations of Pb, Cd and Zn were: 0.03±0.04, 0.01±0.01 and 1.62±0.02 ppm respectively. The mean Pb concentrations for water samples ranged between 0.01±0.01 and 0.14±0.04 ppm while Zn mean concentrations were between 0.00±0.01 and 0.92±0.01 ppm with Cd being below detection limit. ANOVA, SNK test showed significant differences in mean concentrations of Pb and Zn in Industrial area and Mwangi sites with respect to depth. This meant that activities at garage sites caused change in concentrations with depth. In Kaunda garage, the mean concentrations for lead were not sig-nificantly different while the mean concentrations for zinc were significantly different for the three soil profiles fractionated (p˂0.05, Anova,SNK test). Pearson product moment correla-tion of water soluble and exchangeable fractions with the total metals showed negative corre-lation. This indicates that high concentration of heavy metals in garage soils does not neces-sarily infer their mobility and therefore their bioavailability. The stream and garage soils are slightly contaminated with respect to lead while the kales contained all metals within toler-able levels. Due to variation of mean concentrations of Pb and Zn with depth, as an evidence of surface pollution, there is not only need to relocate garages from the town centre but also to plant indigenous plant species on affected soils to mop up the bioavailable heavy metal forms.
New Catalytic Reactions of Iron(III) Porphyrins
(2014) Mbuvi, Harun M.
Metalloporphyrins have long been known to be effective catalysts for a variety of organic reactions. These include cyclopropanation, epoxidation, and aziridination of olefins. Iron porphyrins are also efficient catalysts for the olefination of aldehydes and ketones in the presence of triphenylphosphine. This suggested to us that iron porphyrins might have the potential to mediate a variety of other processes. The work described in this dissertation broadly extends the reactions catalyzed by iron(III) tetraphenylporphyrin chloride by focusing on the use of metalloporphyrins, mainly iron(III), Fe(TPP)Cl, as catalysts for N-H, C-H and O-H insertion reactions and cyclopropanation of arenes using various diazo reagents as sources of carbenes. A tandem N-H insertion/cyclization reaction using ethylenediamine and ethanolamine to give 2-piperazinone and 2-morpholinone respectively has also been investigated. Fe(TPP)Cl is one of the most efficient catalysts for insertion of the carbene derived from EDA into amine N-H bonds. This insertion reaction can be performed at room temperature and atmospheric conditions in relatively short reaction times. Fe(TPP)Cl is also an effective catalyst for O-H insertion reactions to alcohols when substituted methyl 2-phenyldiazoacetates are used as sources of carbene. Aromatic and normal aliphatic alcohols give O-H insertion as the only product.
Oxidation of cyclic amines by molybdenum(II) and tungsten(II) halocarbonyls, [M(CO)4X2]2 (M = Mo, W; X = Cl, Br)
(Chemical Society of Ethiopia, 2013) Onindo, Charles O.; Muriithi, Naftali T.; Mbuvi, Harun M.; Andala, D. M.
The molybdenum(II) and tungsten(II) halocarbonyls, [M(CO)4X2]2 (M = Mo, W; X = Cl, Br) react with a large excess of the nitrogen bases, 1-methylpyrrolidine, 1-methylpiperidine, 1-ethylpiperidine and 2-ethylpiperidine to give aminecarbonyl complexes of the type M(CO)3L3 (L= alkylamine). Excess piperidine reacts with the tungsten halocarbonyls, [W(CO)4X2]2 (X = Cl, Br), to give the trans isomer of the complex, W(CO)3(C5H11N)3. The halogens were recovered as the amminium salts, amine, HX. The oxidized amine dimerized to form a yellow product which was recovered as an oily liquid but in very small amounts. However, in the reaction between Mo(CO)4Br2 and 1-ethylpiperidine, a yellow crystalline solid, with a melting point of 224 oC was recovered in sufficient amounts for elemental analysis, melting point and spectral data. Its mass spectrum showed a molecular ion peak at m+/z = 222, a clear evidence that the oxidized amine dimerizes. The cyclic dibasic amine piperazine, C4H10N2 is not, however, oxidized by these halocarbonyls but rather it reacts by substituting some CO groups to form products of the type, M(CO)3(C4H10N2)2X2 (M = Mo, W; X = Cl, Br). Products were characterized by elemental analysis, IR, UV, 1H NMR and mass spectrometry.
Oxidation of cyclic amines by molybdenum(II) and tungsten(II) halocarbonyls, [M(CO)4X2]2 (M = Mo, W; X = Cl, Br)
(Chemical Society of Ethiopia, 2013) Onindo, Charles O.; Muriithi, Naftali T.; Mbuvi, Harun M.; Andala, D. M.
The molybdenum(II) and tungsten(II) halocarbonyls, [M(CO)4X2]2 (M = Mo, W; X = Cl, Br) react with a large excess of the nitrogen bases, 1-methylpyrrolidine, 1-methylpiperidine, 1-ethylpiperidine and 2-ethylpiperidine to give aminecarbonyl complexes of the type M(CO)3L3 (L= alkylamine). Excess piperidine reacts with the tungsten halocarbonyls, [W(CO)4X2]2 (X = Cl, Br), to give the trans isomer of the complex, W(CO)3(C5H11N)3. The halogens were recovered as the amminium salts, amine, HX. The oxidized amine dimerized to form a yellow product which was recovered as an oily liquid but in very small amounts. However, in the reaction between Mo(CO)4Br2 and 1-ethylpiperidine, a yellow crystalline solid, with a melting point of 224 oC was recovered in sufficient amounts for elemental analysis, melting point and spectral data. Its mass spectrum showed a molecular ion peak at m+/z = 222, a clear evidence that the oxidized amine dimerizes. The cyclic dibasic amine piperazine, C4H10N2 is not, however, oxidized by these halocarbonyls but rather it reacts by substituting some CO groups to form products of the type, M(CO)3(C4H10N2)2X2 (M = Mo, W; X = Cl, Br). Products were characterized by elemental analysis, IR, UV, 1H NMR and mass spectrometry.
Oxidation of cyclic amines by molybdenum(ii) and tungsten(ii) halocarbonyls, [m(co)4x2]2 (m = mo, w; x = cl, br)
(Chemical Society of Ethiopia, 2013) Muriithi, Naftali T.; Onindo, Charles O.; Mbuvi, Harun M.; Andala, Dickson M.
The molybdenum(II) and tungsten(II) halocarbonyls, [M(CO)4X2]2 (M = Mo, W; X = Cl, Br) react with a large excess of the nitrogen bases, 1-methylpyrrolidine, 1-methylpiperidine, 1-ethylpiperidine and 2- ethylpiperidine to give aminecarbonyl complexes of the type M(CO)3L3 (L= alkylamine). Excess piperidine reacts with the tungsten halocarbonyls, [W(CO)4X2]2 (X = Cl, Br), to give the trans isomer of the complex, W(CO)3(C5H11N)3. The halogens were recovered as the amminium salts, amine, HX. The oxidized amine dimerized to form a yellow product which was recovered as an oily liquid but in very small amounts. However, in the reaction between Mo(CO)4Br2 and 1-ethylpiperidine, a yellow crystalline solid, with a melting point of 224 oC was recovered in sufficient amounts for elemental analysis, melting point and spectral data. Its mass spectrum showed a molecular ion peak at m+/z = 222, a clear evidence that the oxidized amine dimerizes. The cyclic dibasic amine piperazine, C4H10N2 is not, however, oxidized by these halocarbonyls but rather it reacts by substituting some CO groups to form products of the type, M(CO)3(C4H10N2)2X2 (M = Mo, W; X = Cl, Br). Products were characterized by elemental analysis, IR, UV, 1H NMR and mass spectrometry
Oxidation of cyclic amines by molybdenum(II) and tungsten(II) halocarbonyls, [M(CO)4X2]2 (M = Mo, W; X = Cl, Br)
(Chemical Society of Ethiopia, 2013) Muriithi, Naftali T.; Onindo, Charles O.; Mbuvi, Harun M.; Andala, Dickson M.
The molybdenum(II) and tungsten(II) halocarbonyls, [M(CO)4X2]2 (M = Mo, W; X = Cl, Br) react with a large excess of the nitrogen bases, 1-methylpyrrolidine, 1-methylpiperidine, 1-ethylpiperidine and 2- ethylpiperidine to give aminecarbonyl complexes of the type M(CO)3L3 (L= alkylamine). Excess piperidine reacts with the tungsten halocarbonyls, [W(CO)4X2]2 (X = Cl, Br), to give the trans isomer of the complex, W(CO)3(C5H11N)3. The halogens were recovered as the amminium salts, amine, HX. The oxidized amine dimerized to form a yellow product which was recovered as an oily liquid but in very small amounts. However, in the reaction between Mo(CO)4Br2 and 1-ethylpiperidine, a yellow crystalline solid, with a melting point of 224 oC was recovered in sufficient amounts for elemental analysis, melting point and spectral data. Its mass spectrum showed a molecular ion peak at m+/z = 222, a clear evidence that the oxidized amine dimerizes. The cyclic dibasic amine piperazine, C4H10N2 is not, however, oxidized by these halocarbonyls but rather it reacts by substituting some CO groups to form products of the type, M(CO)3(C4H10N2)2X2 (M = Mo, W; X = Cl, Br). Products were characterized by elemental analysis, IR, UV, 1H NMR and mass spectrometry
Oxidation of cyclic amines by molybdenum(II) and tungsten(II) halocarbonyls, [M(CO)4X2]2 (M = Mo, W; X = Cl, Br)
(Chemical Society of Ethiopia, 2013) Onindo, Charles O; Muriithi, Naftali T.; Mbuvi, Harun M.; Andala, D. M.
The molybdenum(II) and tungsten(II) halocarbonyls, [M(CO)4X2]2 (M = Mo, W; X = Cl, Br)react with a large excess of the nitrogen bases, 1-methylpyrrolidine, 1-methylpiperidine, 1-ethylpiperidine and 2- ethylpiperidine to give aminecarbonyl complexes of the type M(CO)3L3 (L= alkylamine). Excess piperidine reacts with the tungsten halocarbonyls, [W(CO)4X2]2 (X = Cl, Br), to give the trans isomer of the complex, W(CO)3(C5H11N)3. The halogens were recovered as the amminium salts, amine, HX. The oxidized amine dimerized to form a yellow product which was recovered as an oily liquid but in very small amounts. However, in the reaction between Mo(CO)4Br2 and 1-ethylpiperidine, a yellow crystalline solid, with a melting point of 224 oC was recovered in sufficient amounts for elemental analysis, melting point and spectral data. Its mass spectrum showed a molecular ion peak at m+/z = 222, a clear evidence that the oxidized amine dimerizes. The cyclic dibasic amine piperazine, C4H10N2 is not, however, oxidized by these halocarbonyls but rather it reacts by substituting some CO groups to form products of the type, M(CO)3(C4H10N2)2X2 (M = Mo, W; X = Cl, Br). Products were characterized by elemental analysis, IR, UV, 1H NMR and mass spectrometry.
Oxidation of cyclic amines by molybdenum(II) and tungsten(II) halocarbonyls, [M(CO)4X2]2 (M = Mo, W; X = Cl, Br)
(Chemical Society of Ethiopia, 2013) Mbuvi, Harun M.; Onindo, Charles O.; Muriithi, Naftali T.; Andala, D. M.
The molybdenum(II) and tungsten(II) halocarbonyls, [M(CO)4X2]2 (M = Mo, W; X = Cl, Br) react with a large excess of the nitrogen bases, 1-methylpyrrolidine, 1-methylpiperidine, 1-ethylpiperidine and 2-ethylpiperidine to give aminecarbonyl complexes of the type M(CO)3L3 (L= alkylamine). Excess piperidine reacts with the tungsten halocarbonyls, [W(CO)4X2]2 (X = Cl, Br), to give the trans isomer of the complex, W(CO)3(C5H11N)3. The halogens were recovered as the amminium salts, amine, HX. The oxidized amine dimerized to form a yellow product which was recovered as an oily liquid but in very small amounts. However, in the reaction between Mo(CO)4Br2 and 1-ethylpiperidine, a yellow crystalline solid, with a melting point of 224 oC was recovered in sufficient amounts for elemental analysis, melting point and spectral data. Its mass spectrum showed a molecular ion peak at m+/z = 222, a clear evidence that the oxidized amine dimerizes. The cyclic dibasic amine piperazine, C4H10N2 is not, however, oxidized by these halocarbonyls but rather it reacts by substituting some CO groups to form products of the type, M(CO)3(C4H10N2)2X2 (M = Mo, W; X = Cl, Br). Products were characterized by elemental analysis, IR, UV, 1H NMR and mass spectrometry.
Oxidation of cyclic amines by molybdenum(II) and tungsten(II) halocarbonyls, [M(CO)4X2]2 (M = Mo, W; X = Cl, Br)
(Bulletin of the Chemical Society of Ethiopia, 2013-01) Mbuvi, Harun M.
Oxidation of cyclic amines by molybdenum(II) and tungsten(II) halocarbonyls, [M(CO)4X2]2 (M = Mo, W; X = Cl, Br)
Oxidation of Cyclic Amines by Molybdenum(ii) and Tungsten(ii) Halocarbonyls, [m(Co)4x2]2 (m = Mo, w; x = Cl, Br).
(Bulletin of the Chemical Society of Ethiopia, 2013) Muriithi, Naftali T.; Onindo, Charles O.; Mbuvi, Harun M.; Andala, Dickson M.
The molybdenum(II) and tungsten(II) halocarbonyls, [M(CO)4X2]2 (M = Mo, W; X = Cl, Br) react with a large excess of the nitrogen bases, 1-methylpyrrolidine, 1-methylpiperidine, 1-ethylpiperidine and 2- ethylpiperidine to give aminecarbonyl complexes of the type M(CO)3L3 (L= alkylamine). Excess piperidine reacts with the tungsten halocarbonyls, [W(CO)4X2]2 (X = Cl, Br), to give the trans isomer of the complex, W(CO)3(C5H11N)3. The halogens were recovered as the amminium salts, amine, HX. The oxidized amine dimerized to form a yellow product which was recovered as an oily liquid but in very small amounts. However, in the reaction between Mo(CO)4Br2 and 1-ethylpiperidine, a yellow crystalline solid, with a melting point of 224 oC was recovered in sufficient amounts for elemental analysis, melting point and spectral data. Its mass spectrum showed a molecular ion peak at m+/z = 222, a clear evidence that the oxidized amine dimerizes. The cyclic dibasic amine piperazine, C4H10N2 is not, however, oxidized by these halocarbonyls but rather it reacts by substituting some CO groups to form products of the type, M(CO)3(C4H10N2)2X2 (M = Mo, W; X = Cl, Br). Products were characterized by elemental analysis, IR, UV, 1H NMR and mass spectrometry. KEY WORDS: Molybdenum(II), Tungsten(II), Ammines, Halocarbonyls
Oxidation Of Cyclic Amines By Molybdenum(Ii) And Tungsten(Ii) Halocarbonyls, [M(CO)4X2]2 (M=Mo, W; X = Cl, Br)
(Chemical Society of Ethiopia, 2013) Muriithi, Naftali T.; Onindo, Charles O.; Mbuvi, Harun M.; Andala, Dickson M.
The molybdenum(II) and tungsten(II) halocarbonyls, [M(CO)4X2]2 (M = Mo, W; X = Cl, Br) react with a large excess of the nitrogen bases, 1-methylpyrrolidine, 1-methylpiperidine, 1-ethylpiperidine and 2-ethylpiperidine to give aminecarbonyl complexes of the type M(CO)3L3 (L= alkylamine). Excess piperidine reacts with the tungsten halocarbonyls, [W(CO)4X2]2 (X = Cl, Br), to give the trans isomer of the complex, W(CO)3(C5H11N)3. The halogens were recovered as the amminium salts, amine, HX. The oxidized amine dimerized to form a yellow product which was recovered as an oily liquid but in very small amounts. However, in the reaction between Mo(CO)4Br2 and 1-ethylpiperidine, a yellow crystalline solid, with a melting point of 224 oC was recovered in sufficient amounts for elemental analysis, melting point and spectral data. Its mass spectrum showed a molecular ion peak at m+/z = 222, a clear evidence that the oxidized amine dimerizes. The cyclic dibasic amine piperazine, C4H10N2 is not, however, oxidized by these halocarbonyls but rather it reacts by substituting some CO groups to form products of the type, M(CO)3(C4H10N2)2X2 (M = Mo, W; X = Cl, Br). Products were characterized by elemental analysis, IR, UV, 1H NMR and mass spectrometry
The Reaction Of Molybdenum Halocarbonyls , [Mo(CO)4X2]2 ( X=Cl, Br) With Alkylamines . Part1. Preparation Of Substituted Aminecarbonylcomplexes Of Molybdenum And Aminium Salts Of The Type, HX(X=Cl, Br)
(Journal Of The Kenya Chemical Society, 1999) Mbuvi, Harun M.; Muriithi, Naftali T.; Mahungu, S.M
The reaction of tetrahalooctacarbonyldimolybenum (II) complexes,......... with various alylamines have studied with the aim of finding out the nature of the organic oxidation products. In these reactions, piperidine, I-ethylpiperidine, I-methylpiperdine, 2-ethylpiperidine and benzylamine were used in the study. The results obtained show that as in the previous studies, molybdenum (II) is reduced to molybdenum (0). There is no evidence of molybdenum (III) species, hence the reaction must be proceeding via a redox mechanism. Our studies suggest that the amines are oxidized to imines and in a few cases, it was possible to isolate the imine salts.
Removal of Fluoride Ion by Silicon Nitride Powder
(Sci Forschen, 2017) Abdulhameed, Adamu; Mbuvi, Harun M.; Changamu, E. O.
Adsorption of fluoride was done from its aqueous solution by using silicon nitride. In this study, silicon nitrides, SNA, SNB, SNC and SND were synthesized by hydrothermal process done at temperature of 100°C, 150°C, 200°C and 300°C using Rice husk ash (RHA) and sugarcane bagasse ash (SBA) respectively. A batch study on fluoride sorption was carried out at various experimental conditions, including different pH, initial fluoride concentration, and adsorbent dose, shaking speed, contact time and temperatures. Optimum adsorption efficiencies were achieved at pH 2 for SNA, SNB, SNC and pH 4 for SND, contact time 100 minutes, temperature 25°C and shaking speed 600 rpm. The sorption data was found to best into Langmuir isotherm. The adsorption capacities for fluoride ions were 7.9, 8.9, 13.9 and 49.8 mg/g for SNA, SNB, SNC and SND respectively. This results indicate that the silicon nitride constitute a promising material for the development of an adsorption technology for the removal of fluoride ions from aqueous systems.
Rice Husk Ash Derived Zeolite Blended with Water Hyacinth Ash for Enhanced Adsorption of Cadmium Ions
(Enviro Research Publishers, 2014) Mbuvi, Harun M.; Mbugua, G. W.; Muthengia, J. W.
In order to helpcurtail or imposesustained control to the offensive water hyacinth plant,it is essential to explore ways of generatingwater remediation materials from it. In the current study, the capacity and efficacy of water hyacinth ash (WHA),its insoluble residue (WHAR) and rice husk ash (RHA)to remove cadmium ionsand methylene blue from contaminated water was investigated. Mixtures of the two ashes were used to formulatezeolitic materialsby hydrothermal reactions. Material A, ZMA was prepared by using rice husk ash and the soluble portion of WHA while for material B, ZMB a mixture of equal amounts the two ashes including the insoluble fraction of WHA were used. Batch experiments was carried out to determine the effect of metal ion concentration, initial PH, contact time (t), temperature (T), shaking speed and adsorbent dose on percentage removal of Cd2+ and methylene blue by the ashes and their zeolitic products. The data obtained for adsorption of Cd2+ on RHA, ZMA, and ZMB was found to best fit in the Langmuir isotherm model while WHA and WHAR data best fitted in theFreundlich model. Adsorption capacities for cadmium on RHA, WHA, WHAR, ZMA and ZMB adsorbents ions were 3.745, 52.00, 56.89, 11.24 and 22.22mg/g respectively.The findings showed that incorporating the WHAR during synthesis of the zeolitic material enhanced its adsorption capacity and efficiency for Cd (II) ions and methylene blue.
Speciation Of Cadmium and Lead in Garage Soils From Ngara- Nairobi and Their Levels in Nearby Vegetables and Water
(International Journal of Physical and Social Sciences, 2014-03) Mbuvi, Harun M.; Nasiebanda, Roselyne; Onindo, Charles O.; Mbuvi, C. O.
Mismanagement of chemical wastes from light industries and motor vehicle garages results to pollution of the natural environment and poses substantial danger to public health and welfare. The present study reports levels and forms of Pb and Cd in garage soils obtained from Ngara-Nairobi and their levels in vegetables and water bodies found nearby. The concentration levels of cadmium obtained ranged from 0.40-4.80 mg/kg and a mean of 2.95±0.14 mg/kg. Its concentration levels were highest in the residual, followed by exchangeable, then oxidisable and least amount in the reducible bound fraction. Thus, a high percentage of cadmium is associated with non-residual fractions and can easily be transferred into the food chain through water reservoirs or uptake by plants growing in the soils. The concentration levels of lead were found to be within the range of 22.00-313.60 mg/kg and had a mean of 128.36±6.51 mg/kg. Its concentration levels in the fractions from highest to lowest followed the order; reducible, residual, oxidisable and exchangeable. The mobility factor of cadmium was found to be 33.4405 while that of lead was 7.05. Concentration levels of cadmium in nearby kales ranged from 0.73 to1.50 mg/kg while those of lead ranged from10.25 to 19.60 mg/kg. In spinach the concentration levels of cadmium and lead ranged from 0.84 to 1.75 and 7.83 to 20.53 mg/kg respectively.Concentration levels in water samples ranged from 0.77 to 1.50 mg/L for cadmium and4.60 to 8.89 mg/L for lead.These high concentration levels of the metals in water and vegetable pose great danger to human health as their consumption can lead to serious depletion of some essential nutrients in their bodies thus leading to decrease in immunological defenses.This calls for proper waste management procedures, continuous education and training to the artisans andefficient soil remediation programs at the sites.

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