Browsing by Author "Shiundu, Paul M"

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Adsorption and detection of some phenolic compounds by rice husk ash of Kenyan origin
(2002) Mbui, Damaris N; Shiundu, Paul M; Ndonye, Rachel M; Kamau, Geoffrey N
Rice husk ash (RHA) obtained from a rice mill in Kenya has been used as an inexpensive and effective adsorbent (and reagent) for the removal (and detection) of some phenolic compounds in water. The abundantly available rice mill waste was used in dual laboratory-scale batch experiments to evaluate its potential in: (i) the removal of phenol, 1,3-dihydroxybenzene (resorcinol) and 2-chlorophenol from water; and (ii) the detection of 1,2-dihydroxybenzene (pyrocatechol) and 1,2,3-trihydroxybenzene (pyrogallol) present in an aqueous medium. The studies were conducted using synthetic water with different initial concentrations of the phenolic compounds. The effects of different operating conditions (such as contact time, concentration of the phenolic compounds, adsorbent quantity, temperature, and pH) were assessed by evaluating the phenolic compound removal efficiency as well as the extent of their color formation reactions (where applicable). RHA exhibits reasonable adsorption capacity for the phenolic compounds and follows both Langmuir and Freundlich isotherm models. Adsorption capacities of 1.53 × 10−4, 8.07 × 10−5, and 1.63 × 10−6 mol g−1 were determined for phenol, resorcinol and 2-chlorophenol, respectively. Nearly 100% adsorption of the phenolic compounds was possible and this depended on the weight of RHA employed. For the detection experiments, pyrocatechol and pyrogallol present in water formed coloured complexes with RHA, with the rate of colour formation increasing with temperature, weight of RHA, concentration of the phenolic compounds and sonication. This study has proven that RHA is a useful agricultural waste product for the removal and detection of some phenolic compounds.
Adsorption of Congo Red Dye from Aqueous Solutions Using Roots of Eichhornia Crassipes: Kinetic and Equilibrium Studies
(Elsevier, 2014) Wanyonyi, Wycliffe Chisutia; Onyari, , John Mmari; Shiundu, Paul M
Adsorption of Congo red (CR) from aqueous solution using dried roots of Eichhornia crassipes was studied. Batch experiments were carried out for sorption kinetics and isotherms. Experimental results obtained showed that adsorption process was highly dependent on contact time, adsorbent dosage, initial dye concentration and particle size. The sorption equilibrium for Congo red dye by E. crassipes (roots) was reached within 90 minutes and adsorption efficiency of up to 96% achieved. The sorption kinetics followed a pseudo-second-order kinetic model while Freundlich isotherm model was best applicable for obtaining the equilibrium parameters. These results demonstrate that roots of E. crassipes are effective, environmentally friendly and low-cost biomaterial for dye removal from aqueous dye solutions and industrial effluents.
Adsorption of methylene blue dye from aqueous solutions using Eichhornia crassipes
(2013) Wanyonyi, Wycliffe Chisutia; Onyari, John Mmari; Shiundu, Paul M
Adsorption of methylene blue (MB) from aqueous solution using dried roots, stems, and leaves of Eichhornia crassipes biomass obtained from Lake Victoria was studied. Batch experimental results revealed that the adsorption process was highly dependent on adsorbent dosage, initial MB concentration, E. crassipes particle size and aqueous solution temperature. The isotherm data fitted Freundlich mathematical models with maximum dye adsorption of 35.37 mg g−1. Roots adsorbed over 99 % of the MB in <5 min. Sorption kinetics followed a pseudo-second-order model. Results provide evidence that E. crassipes is an effective and inexpensive biomaterial for dye removal from aqueous dye solutions and industrial effluents.
Adsorption of Pb (II) Ions from Aqueous Solutions by Water Hyacinth (Eichhornia Crassipes): Equilibrium and Kinetic Studies
(2014) Anzeze, Davis Amboga; Onyari, John Mmari; Gichuki, John W; Shiundu, Paul M
The Eichhornia crassipes roots for the removal of Pb (II) ions from aqueous solutions has been investigated. The adsorption of Pb (II) ions was found to be affected by solution pH, contact time, adsorbent dosage, initial metal ion concentration, and temperature. The equilibrium was analysed using Langmuir and Freundlich isotherm models. The data was found to have a closer correlation with the Freundlich isotherm as evidenced by a higher correlation coefficient (R2). The biosorption capacity for E. crasippes was found to be 16.350 mg g-1. The Kinetics data was also subjected to pseudo-first-order and the pseudo-second-order kinetic models. The data could be explained better using the pseudo-second-order kinetic model.
Air and blood lead levels in lead acid battery recycling and manufacturing plants in Kenya
(Taylor & Francis, 2012) Were, Faridah H; Kamau, Geoffrey N; Shiundu, Paul M; Wafula, Godfrey A; Moturi, Charles M
The concentration of airborne and blood lead (Pb) was assessed in a Pb acid battery recycling plant and in a Pb acid battery manufacturing plant in Kenya. In the recycling plant, full-shift area samples taken across 5 days in several production sections showed a mean value ± standard deviation (SD) of 427 ± 124 μg/m3, while area samples in the office area had a mean ± SD of 59.2 ± 22.7 μg/m3. In the battery manufacturing plant, full-shift area samples taken across 5 days in several production areas showed a mean value ± SD of 349 ± 107 μg/m3, while area samples in the office area had a mean ± SD of 55.2 ± 33.2 μg/m3. All these mean values exceed the U.S. Occupational Safety and Health Administration's permissible exposure limit of 50 μg/m3 as an 8-hr time-weighted average. In the battery recycling plant, production workers had a mean blood Pb level ± SD of 62.2 ± 12.7 μg/dL, and office workers had a mean blood Pb level ± SD of 43.4 ± 6.6 μg/dL. In the battery manufacturing plant, production workers had a mean blood Pb level ± SD of 59.5 ± 10.1 μg/dL, and office workers had a mean blood Pb level ± SD of 41.6 ± 7.4 μg/dL. All the measured blood Pb levels exceeded 30 μg/dL, which is the maximum blood Pb level recommended by the ACGIH®. Observations made in these facilities revealed numerous sources of Pb exposure due to inadequacies in engineering controls, work practices, respirator use, and personal hygiene
Biosorption of Malachite Green from Aqueous Solutions onto Polylactide/Spent Brewery Grains Films: Kinetic and Equilibrium Studies
(2012) Chanzu, Harry Amuguni; Onyari, John Mmari; Shiundu, Paul M
Batch experiments were conducted to study the biosorption of Malachite Green (MG) onto polylactide (PLA)/spent brewery grains (SBGs) films. Films were prepared by solvent-casting method using dichloromethane. Effects of contact time, pH, salt concentration, and optimal experimental condition was evaluated. At pH 6.89 and low salt concentration, Malachite Green was removed effectively. The isotherm data fitted the Freundlich model with 0.969 R2 value and 0.738 slope implying chemisorptions process. The biosorption process followed pseudo-second order kinetics with calculated adsorption capacity at equilibrium (qe) of 0.572 mg/g at 23 °C. The investigation showed that PLA/SBGs films are effective in dye removal from textile, paper and leather industries effluents.
Biosorption of Zn (II) ions from aqueous solutions by water hyacinth (Eichhornia crasippes): Equilibrium and Kinetic studies
(2014) Anzeze, Davis Amboga; Onyari, John Mmari; Shiundu, Paul M; Gichuki, John W
The biosorption characteristics of Zn (II) ions were investigated. Experimental parameters affecting the biosorption process such as pH, contact time, biomass dosage, initial metal ion concentration, and temperature were studied in batch adsorption experiments. Langmuir and Freundlich isotherm models were applied to the adsorption data .The biosorption capacity for E. crasippes was found to be 16.50 mg g-1. The data was also subjected to pseudo-first-order and the pseudo-second-order kinetic models.
Computer-controlled apparatus for automated development of continuous flow methods
(1989) Wentzell, Peter D; Hatton, Michael J; Shiundu, Paul M; Ree, Ronald M; Wade, Adrian P
An automated apparatus to assist in the development ofanalytical continuous flow methods is described. The system is capable of controlling and monitoring a variety ofpumps, valves, and detectors through an IBM PC-AT compatible computer. System components consist of two types ofperistaltic pumps (including a multiplepump unit), syringepumps, electrically andpneumatically actuated valves, and an assortment of spectrophotometric and electrochemical detectors. Details ofthe interface circuitry are given where appropriate. To demonstrate the utility of the system, an automatically generated response surface is presentedfor theflow injection determination of iron(II) by its reaction with 1,10-phenanthroline.
Development of catalytic photometric flow injection methods for the determination of selenium
(1991) Shiundu, Paul M; Wade, Adrian P
Effects of heavy metal pollution on ω3 polyunsaturated fatty acids levels in tilapia fish from Winam Gulf of Lake Victoria
(2013) Muinde, V; Nguu, E; Ogoyi, D; Shiundu, Paul M
Essentiality of a Newly Identified Carbohydrate-Binding Module for the Function of CelB (BH0603) from the Alkaliphilic Bacterium Bacillus halodurans▿
(2006) Wamalwa, Benson Munyali; Sakka, Makiko; Shiundu, Paul M; Ohmiya, Kunio; Kimura, Tetsuya; Sakka, Kazuo
CelB (BH0603) from Bacillus halodurans is a modular glycoside hydrolase with a family 5 catalytic module, an immunoglobulin-like module, and module PfamB of unknown function. The recombinant PfamB module bound to Avicel and was essential for CelB hydrolytic function. We propose that module PfamB be designated a new carbohydrate-binding module.
FACTORS AFFECTING PARTICLE RETENTION IN THERMAL FIELD-FLOW FRACTIONATION
(2002) Shiundu, Paul M; Munguti, Stephen M; Wamalwa, Ben. M
In this paper, we report a range of factors which affect the retention of colloidal particles in thermal field-flow fractionation (ThFFF). These results are observed among different sizes of polystyrene (PS) latex particles suspended in both aqueous and nonaqueous liquid carriers and very low density lipoproteins in a phosphate buffer. These factors include particle size and chemical composition, field strength, cold-wall temperature of the channel and the nature of the suspension medium. These results show that ThFFF can be used to fractionate colloidal particles according to size and that for an unknown colloidal sample material, a calibration curve must be obtained using particles of similar composition. This is necessary because the degree of retention of the colloidal material is dependent on chemical composition of sample material as evidenced by the chemical composition study. The potential of using ThFFF for physico-chemical characterization of colloidal material is illustrated through the evaluation of thermal diffusion coefficient of PS particles as a function of size, cold-wall temperature, and carrier solution composition. The tunabiliy of the extent of retention of the colloidal particles in a ThFFF channel is illustrated by results of the influence of field strength on retention.
High-level heterologous expression of Bacillus halodurans putative xylanase xyn11a (BH0899) in Kluyveromyces lactis
(2007) Wamalwa, Benson Munyali; Zhao, Guangshan; Sakka, Makiko; Shiundu, Paul M; Kimura, Tetsuya; Sakka, Kazuo
The putative xyn11A structural gene (BH0899) encoding a family-11 xylanase from alkaliphilic Bacillus halodurans strain C-125 was heterologously expressed in the yeast Kluyveromyces lactis CBS 1065 and secreted to a level of 156 μg/ml under selective culture conditions in shake flasks. The Xyn11A production level in shake flask cultures of K. lactis CBS 1065 was higher than that reported for other xylanase genes placed under the control of the regulated LAC4 promoter on a plasmid containing an entire sequence of pKD1 from Kluyveromyces drosophilarium. Recombinant Xyn11A was highly active over pH range from 3 to 10, with maximal activity around pH 7. The enzyme showed a specific activity of 628 U/mg-protein on birchwood xylan as substrate, but no cellulase or β-xylosidase activity.
Influence of bulk and surface composition on the retention of colloidal particles in thermal field-flow fractionation
(Elsevier, 1995) Shiundu, Paul M; Giddings, J. Calvin
In this paper we report a wide range of cases in which the retention of colloidal particles in thermal field-flow fractionation (FFF) shows a strong dependence on the chemical composition of the particles or of the particle surfaces. These results are observed among similar particles (such as different latexes) or between dissimilar particles (including latexes as well as inorganic and metallic colloids). These compositional effects are observed for particles suspended in both aqueous and nonaqueous carrier liquids. The dependence of retention on composition is complementary to its dependence on particle size, which has been amply demonstrated in previous studies. The compositional effect is attributed to the dependence of the thermal diffusion coefficient on compositional factors. A number of cases are presented here where compositional effects are significant. Examples include the baseline resolution of 0.30-μm silica particles and 0.300-μm polystyrene (PS) particles and a large difference in retention times between 0.232-μm PS and 0.229-μm polymethylmethacrylate (PMMA) latexes in aqueous suspensions. Also, metallic particles (e.g., palladium) were less retained than silica particles, with latex particles most retained. The resolution of equal-size particles in the nonaqueous carrier liquid acetonitrile is also demonstrated. Surface compositional effects have also been found in this study. These effects suggest the possibility of colloidal surface analysis by thermal FFF. The potential for performing both bulk and surface compositional analysis of particles by thermal FFF makes this FFF technique complementary to both sedimentation FFF and flow FFF techniques for the analysis of complex particulate materials.
Isolation and characterization of polymeric and particulate components of acrylonitrile–butadiene–styrene (ABS) plastics by thermal field-flow fractionation
(Wiley, 1996) Shiundu, Paul M; Remsen, Edward E; Giddings, J. Calvin
Thermal field-flow fractionation (ThFFF) is shown here to be capable of isolating the polymeric and rubber particulate components of acrylonitrile–butadiene–styrene (ABS) plastic in a simple analytical procedure. To facilitate the separation, the ionic strength of the two carrier liquids used here (THF and DMF) was brought up to 0.10 mM to increase the retention of the rubber particles. At a field strength (temperature drop) δT of 50 K, the two components were well separated, although the polymer component was not completely resolved from the void peak due to its low molecular weight. To facilitate a more rapid separation of the components, both field programming and high flow-rate conditions were examined in some detail. Both the particle-size distribution (PSD) of the rubber particles and the molecular weight distribution (MWD) of the polymer components were obtained using ThFFF. Measured MWD and PSD agreed favorably with PSD determined by dynamic light scattering and MWD obtained by size-exclusion chromatography.
Kinetics and thermodynamics of aqueous Cu(II) adsorption on heat regenerated spent bleaching earth
(2011) Wambu, Enos W; Muthakia, Gerald K; wa-Thiong’o, Joseph K; Shiundu, Paul M
This study investigated the kinetics and thermodynamics of copper(II) removal from aqueous solutions using spent bleaching earth (SBE). The spent bleaching earth, a waste material from edible oil processing industries, was reactivated by heat treatment at 370 oC after residual oil extraction in excess methyl-ethyl ketone. Copper adsorption tests were carried out at room temperature (22±3 oC) using 5.4 x 10-3 M metal concentrations. More than 70% metal removal was recorded in the first four hours although adsorption continued to rise to within 90% at 42 hours. The pH, adsorbent dosage and initial concentrations were master variables affecting RSBE adsorption of Cu(II) ions. The adsorption equilibrium was adequately described by the Dubinin-Radushkevich (D-R) and the Temkin isotherms and the maximum sorption capacity derived from the D-R isotherm was compared with those of some other low cost adsorbents. The adsorption process was found to follow Lagergren Pseudo-second order kinetics complimented by intra-particle diffusion kinetics at prolonged periods of equilibration. Based on the D-R isotherm adsorption energy and the thermodynamic adsorption free energy ∆G, it was suggested that the process is spontaneous and based on electrostatic interactions between the metal ions and exposed active sites in the adsorbent surface.
Lead Exposure and Blood Pressure among Workers in Diverse Industrial Plants in Kenya
(Taylor & Francis, 2014) Were, Faridah H; Moturia, M. Charles; Gottesfeld, P; Wafula, Godfrey A; Kamau, Geoffrey N; Shiundu, Paul M
The study evaluated airborne exposures and blood lead (BPb) levels in 233 production workers at six diverse industrial plants in Kenya. Blood and personal breathing zone air samples were collected and analyzed for lead (Pb) using atomic absorption spectroscopy. Blood pressure (BP) levels were measured using a standard mercury sphygmomanometer. The results indicated mean airborne Pb levels ± standard deviation (SD) as follows: 183.2 ± 53.6 μg/m3 in battery recycling, 133.5 ± 39.6 μg/m3 in battery manufacturing, 126.2 ± 39.9 μg/m3 in scrap metal welding, 76.3 ± 33.2 μg/m3 in paint manufacturing, 27.3 ± 12.1 μg/m3 in a leather manufacturing, and 5.5 ± 3.6 μg/m3 in a pharmaceutical plant. The mean airborne Pb levels exceeded the U.S. Occupational Safety and Health Administration (OSHA) 8-hr time-weighted average (TWA) permissible exposure limit (PEL) for Pb of 50 μg/m3 in the battery manufacturing, battery recycling, welding, and paint manufacturing plants. Similarly, mean BPb concentrations exceeded the American Conference of Governmental Industrial Hygienists (ACGIH®) biological exposure index (BEI) for Pb of 30 μg/dl. A significant positive association was observed between BPb and breathing zone air Pb (R2 = 0.73, P < 0.001). Approximately 30% of the production workers (N = 233) were in the hypertensive range with an average systolic and diastolic blood pressure (BP) of 134.7 ± 12.7 mmHg and 86.4 ± 8.9 mmHg, respectively. In the multivariate regression analysis, age, duration of work, airborne Pb and BPb levels were significantly associated (P < 0.05) with a change in BP. We recommend improved engineering controls, work practices, and personal hygiene to reduce Pb exposures. In addition, workers should undergo comprehensive medical surveillance to include BPb and BP testing, and airborne Pb assessments in all industries with significant lead exposures.
Magnitude and direction of thermal diffusion of colloidal particles measured by thermal field-flow fractionation
(Elsevier, 2003) Shiundu, Paul M; Williams, P.Stephen; Giddings, J.Calvin
In this paper we provide experimental evidence showing that various types of submicrometer-sized particles (latexes, inorganic, and metallic), suspended in either aqueous or nonaqueous carrier liquids to which a temperature gradient dT/dx is applied, experience a force in the direction opposite to that of dT/dx. This behavior is similar to that of small particles such as soot, aerosols, and small bubbles suspended in stagnant gases across which temperature gradients are applied, a phenomenon known as “thermophoresis in gases.” We report the use of a thermal field-flow fractionation (ThFFF) apparatus in two different configurations to establish the direction of particle motion subject to a temperature gradient. The first approach employed the conventional horizontal ThFFF channel orientation. In this case, small electrical potentials were applied across the narrow channel thickness either to augment or to act in opposition to the applied thermal gradient, depending on whether the accumulation wall was maintained at a positive or negative potential relative to the depletion wall. Thus, by observing the changes in the retention behavior of surface-charged latices or silica particles with changes in potential difference across the channel thickness, we were able to ascertain the direction of migration of the particles in the thermal gradient. The second approach involved the use of a ThFFF column oriented vertically in an implementation of a technique known as thermogravitational FFF. In this approach, the convective flow along the channel length (due to density gradients associated with the temperature gradient) couples with the thermal diffusion effect across the channel thickness to result in a combined particle retention mechanism. A retarded upward migration rate is indicative of accumulation of particles at the cold wall, while enhanced upward migration would indicate a hot-wall accumulation. From the results of our investigations, we conclude that submicrometer-sized particles suspended in either aqueous or nonaqueous carrier liquids and subjected to a temperature gradient migrate from the hot wall toward the cold wall of a ThFFF channel.
Microbiology & Fermentation Technology-High-Level Heterologous Expression of Bacillus halodurans Putative Xylanase Xyn11A (BH0899) in Kluyveromyces lactis.
(2007) Wamalwa, Benson Munyali; Zhao, Guangshan; Sakka, Makiko; Shiundu, Paul M; Kimura, Tetsuya; Sakka., Kazuo
Optical Immunosensor and ELISA for the Analysis of Pyrethroids and DDT in Environmental Samples
(American Chemical Society, 2007) Krämer, Petra M; Weber, Cristina M; Kremmer, Elisabeth; Räuber, Christina; Martens, Dieter; Forster, Stephan; Stanker, Larry H; Rauch, Peter; Shiundu, Paul M; Mulaa, Francis J
An optical immunosensor (AQUA-OPTOSENSOR) and ELISA (enzyme-linked immunosorbent assay) for the analysis of pyrethroids and DDT in river water and/or sediment, are described. The optical immunosensor consists of a bench-top optical read-out-device and disposable single-use sensor chips. ELISA was carried out in the coating antigen format. As examples, phenothrin (pyrethroid) and p,p'-DDT were chosen. Herein we describe the overall strategy, the set-up and principle of the immunosensor platform, and show representative results for immunosensor and ELISA analysis. The immunosensor employs fluorophore (Oyster®-645)-labeled monoclonal antibodies (mouse mAb Py-1 and rat mAb DDT 7C12), and makes use of the evanescent field, thus operating without washing steps. ELISA in the coating antigen format uses a second antibody labeled with peroxidase. Both, phenothrin and p,p'-DDT can be analyzed with these immunochemical techniques in the low ppb levels. Advantages and drawbacks of both immunochemical platforms are discussed