Faculty of Science

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Adsorption of Cadmium Ions on Geopolymers Derived from Ordinary Clay and Rice Husk Ash
(International Journal of Materials and Chemistry, 2018-10-07) Maingi, Francis M.; Mbuvi, H. M.; Ng’ang’a, M. M.; Mwangi, H.
The presence of heavy metals in water is of growing concern. One crucial global strain is the existing disparity in water distribution resulting into millions of people lacking access to safe clean water. This is exasperated by the looming climate change and increased pollution impendence posed by industrialization and population growth. Consequently, pursuance of sustainable materials and technologies for wastewater remediation is critical. Adoption of adsorbents for water treatment is desirable due to their simplicity and cheap materials involved. Geopolymers are prepared hydrothermally using alumina and silica gleaned from clay and rice husks waste materials respectively. These materials are locally attainable and environmentally benign. This work reports synthesis of geopolymers GP-1, GP-2 and GP-3 prepared using clays from three different regions. The XRD diffraction patterns obtained revealed the presence of quartz (SiO2), albite (NaAlSi3O8), vermiculite (Mg,Fe,Al)3((Al,Si)4O10)(OH)2.4H2O), microcline (KAlSi3O8), analcime (NaAlSi2O6•H2O) and natrite (Na2CO3) among other crystalline phases. The initial adsorption rates were found to increase as the Si/Al ratio of the geopolymers increased. The adsorption rates were found to fit into the second order kinetic model. This implies that Cd (II) ions adsorb on geopolymer adsorbents through chemisorption.
Aluminophosphates Derived from Tea Leaves and Pumpkin Seeds Ashes Adsorb Lead Ions from Contaminated Water
(Frontiers in Science, 2018-10-08) Maingi, Francis M.; Mbuvi, H. M.; Ng’ang’a, M. M.
One major global challenge is the existing disparity in water distribution resulting to millions of people lacking access to safe clean water. This will certainly be exacerbated by the impending climate change and increased pollution threats posed by industrialization and population growth. Therefore pursuing sustainable materials and technologies for water remediation is crucial. Adsorbents use for water treatment is preferable owing to its simplicity and cheap materials involved. Aluminophosphates molecular sieves have open-framework structures that possess a wide range of pore openings and large surface area for use as adsorbents that can be synthesized hydrothermally using alumina and phosphates. Literature reports indicate that accumulation of aluminum in tea leaves correlates positively with leaf age. The EDXRF analysis showed that tea leaves ash used contained 30.09% of Al2O3. Similarly, literature findings indicate that pumpkin seeds contain relatively large amounts of phosphorous with the pumpkin seed ash used containing 37.01% of P2O5. Consequently, aluminophosphate APA and APB were synthesized using tea leaves to pumpkin seeds ash ratios of 1:1 and 1:2 respectively. XRD characterization and lead ions batch sorption experiments were done. Turbidity column experiment was done. Data for adsorption of Pb (II) ions data on the adsorbents best fitted into the Langmuir isotherm model. Adsorption capacities obtained from the linearized graphs were 90.91 and 50.0 mg/g for APA and APB respectively. This shows that tea leaves and pumpkin waste can synthesize aluminophosphate adsorbents. Aluminophosphates have shown good potential of removing Pb (II) ions from wastewaters.
Measurement of Radiological Parameters in Harvested Sand in Bungoma County Rivers, Kenya
(Journal of Engineering and Technology for Industrial Applications, 2022-02-08) Waswa, Michael Nakitare; Maingi, Francis M.; Wanyama, Conrad Khisa; Sindani, Lazarus
Samples of sand were collected along the course of ten selected rivers two from each river through random sampling. Activity concentration of 238U, 232Th and 40K were measured using high resolution NaI(Ti) gamma ray spectrometer. Activity concentration of the three primordial radionuclides obtained were used to calculate, absorbed dose rate, annual effective dose rate, interna and external hazard indices and radium equivalent. The average activity concentration for the three primordial radioactive nuclides were; 2±0.1Bq/kg with a range of 0± 0.03Bq/kg to 4±0.24Bq/kg for 238U, 55±2.78Bq/kg with a minimum value of 32±1.6Bq/kg and a maximum value of 87±4.38Bq/kg for 232Th and 51±2,56Bq/kg with a minimum value of 27±1.37Bq/kg and a maximum value of 76±3.8Bq/kg for 40K. The mean activity concentrations for 238U and 40K were below the world averages of 33Bq/kg and 420Bq/kg respectively. The indoor and outdoor annual effective dose rate varied from 0±0mSv/y to 0.2±0.01mSv/y with an average of 0.1±0 mSv/y and 0±0.003mSv/y to 0.1±0.009mSv/y with a mean of 0.1±0.006 mSv/y respectively. The annual effective dose rates were below the safe limits of 1mSv/y. Therefore, use of sand from the selected rivers in Bungoma County, Kenya for construction has minimal health risks to the inhabitants.
Physical-Chemical Characterization of Soils in Selected Potato Growing Areas of Molo, Nakuru County Kenya
(SSRG International Journal of Agriculture & Environmental Science, 2020-08-07) Maingi, Francis M.; Mbuvi, Harun Mbatha; Abdulhameed, Adamu
Characterization of soils in selected potato growing farms of Molo, Nakuru County in Kenya was compelled by the decline in potatoes acreage yields observed in the study area over the years. In the pursuit of reasons behind the decline, this study determined levels of some key soil fertility indices in soil samples obtained from selected farms. Four farms that have been in intensive potatoes farming were used. The soil was randomly collected from a depth of 0-10 cm separately for all the investigated sites. Collected site-wise samples were air-dried, ground, and passed through a 2 mm sieve and stored in plastic containers ready for analysis. Analytical techniques employed were Walkley black for carbon, Kjeldahl for nitrogen, standard wet chem soil analysis, saturation method for water porosity, glass electrode determined soil pH, bulk density, particle density, water holding capacity were determined by methods of Keen box. The mean levels of essential soil fertility indices obtained were; soils pH (5.46 ± 0.43), soil bulk density (g/cm3) (1.03 ± 0.01), particle density (2.51 ± 0.08), water holding capacity (%) (36.07 ± 2.57), porosity (0.59 ± 0.01), exchangeable cations (uS/cm) (83.63 ± 14.22), cation exchange capacity (meq/100g) (18.48 ± 0.89), organic carbon (%) (3.50 ± 0.24), total nitrogen (%) (0.17 ± 0.03). Mean micro and macronutrients available (mg/Kg) were; phosphorous (7.11 ± 2.77), potassium (100.27± 8.32), calcium (198.2 ± 35.1), magnesium (20.97 ±4.28), manganese (15.26 ± 1.12), sulphur (2.31 ± 1.88), copper (0.59 ± 0.12), boron (0.38 ± 0.07), zinc (12.96 ± 2.04), sodium (8.61 ± 0.51), iron (147.92 ± 4.10). These findings reveal the extent of some fertility indices depletion in the soils and will form a base for decreased acreage yield of potatoes in this region. The results further form the baseline for future research on the working acreage of key soil fertility indices required for remediation.
Thermodynamic, Kinetic and Equilibrium Studies of Pb (II) Ions Adsorption Using Ordinary Clay/Rice Husk Ash Based Geopolymers
(IOSR Journal of Applied Chemistry, 2018-08-08) Maingi, Francis M.; Ng’ang’a, M. M.; Mwangi, H.; Mbuvi, H. M.; Abdulhameed, Adamu
One key global challenge is the existing disparity in water distribution resulting to millions of people lacking access to safe clean water. It is currently assessed that 1.1 billion individuals on the planet lacks access to improved quality water supplies. This is aggravated by the looming climate change and increased pollution threats posed by industrialization and population growth. Use of adsorbents for water treatment is preferable due to simplicity of the technique and cheap materials involved. Geopolymers can be easily synthesized hydrothermally using alumina and silica and possess amorphous surface for use as adsorbents. Clay minerals have been reported to contain alumina and silica and previous research show that rice husk ash as well contain substantial amounts of silica. Geopolymers can be easily synthesized hydrothermally using alumina and silica and possess amorphous surface that is useful for adsorption. Hence this work reports information on adsorption of Pb (II) using geopolymers GP-1, GP-2 and GP-3 synthesized with SiO2/Al2O3 ratios of 4.16, 4.18 and 8.29 respectively. Adsorption of metal ions was found to increase from 70.54%± 0.43 to 90.23% ± 0.04 with increase in Si/Al ratio from 4.16 to 8.29 in geopolymers. Equilibrium studies unveiled that experimental data for adsorption of Pb (II) ions best fitted in modified Langmuir Freundlich model. The adsorption capacities of 27.0, 79.58 and 209.9mg/g were obtained for GP-1, GP-2 and GP-3 respectively. Adsorption thermodynamics showed the process corresponded on spontaneous physiosorption activated by increase in temperature. Kinetic study on adsorption of Pb (II) ions onto clay based geopolymers was a Pseudo second order. This information may facilitate the development of optimized procedures for wastewater treatment, thus providing an alternative solution to environmental menace caused by heavy metal pollutants.

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