George W Nyakairu - Academia.edu (original) (raw)

Papers by George W Nyakairu

Environmental Pollution, Aug 1, 2023

Advances in environmental and engineering research, May 24, 2023

Developing adsorbents with appreciable morphology will create new approaches for better phosphate... more Developing adsorbents with appreciable morphology will create new approaches for better phosphate adsorption performance. This study aims to investigate the design of an adsorbent by impregnating silver nanoparticles (AgNPs) onto calcium oxide-activated carbon (CaO-AC). The Ag/CaO-AC nanocomposite was used as an adsorbent to remove phosphate. Batch adsorption studies were performed to evaluate the effects of adsorbent dose, initial phosphate concentration, contact time, and pH on removing phosphate from an aqueous solution. The optimized conditions were applied to a real wastewater sample. The optimum condition for phosphate adsorption on Ag/CaO-AC nanocomposite was at an adsorbent dose of 0.02 g, an initial phosphate concentration of 40 mg•L-1 , an equilibrium contact time of 45 minutes, and pH 7. Pseudo-second-order proved to be more accurate in representing the data of phosphate adsorption onto Ag/CaO-AC nanocomposite. The adsorption isotherm fitted well on the Langmuir model with a maximum adsorption capacity of 77.4 mg•g-1. From the kinetics and isotherm studies, chemisorption was the primary adsorption mechanism through ion exchange and ligand exchange mechanisms. The results of this study show that Ag/CaO-AC nanocomposite is a promising adsorbent for removing phosphate from wastewater.

Applied Geochemistry, May 1, 2023

Water Science and Technology

Phosphate is considered the main cause of eutrophication and has received considerable attention ... more Phosphate is considered the main cause of eutrophication and has received considerable attention recently. Several methods have been used for removal of phosphates in water and these include biological treatment, membrane filtration processes, chemical precipitation, and adsorption. Adsorption technology is highly effective in the removal of phosphate from wastewater even at low phosphate concentrations. Nanomaterials/nanoparticles, carbon-based materials (activated carbon and biochar), and their composites have been widely employed for the adsorptive removal and recovery of phosphate from wastewater due to their exceptional properties such as high surface area and high phosphate adsorption properties. This article is a review of the recently reported literature in the field of nanotechnology and activated carbon for the adsorption of phosphate from wastewater. Highlights of the adsorption mechanisms, adsorption behaviour, experimental parameters, effects of co-existing ions, and ad...

Clay from Iliri was activated using hydrochloric and sulfuric acid of differing concentrations to... more Clay from Iliri was activated using hydrochloric and sulfuric acid of differing concentrations to acquire differing acidities. The chemical compositions of the raw clay and clay activated at different acid concentrations were analyzed to investigate the extent of cation dissolution. From the Na2O to CaO ratio, Iliri clay is swelling sodium bentonite mixed with feldspars, illite, kaolinite and plagioclase. The Langmuir isotherms of 1-aminobutane in isohexane agitated with clay slurries showed increase in clay acidity with increase in concentration of mineral acid used to leach the clay as well as the temperature at which the clay was thermally activated prior to experimentation involving adsorption of 1-aminobutane. The values of surface acidity, nm, for acid-leached Iliri clays ranged from 0.811x10-3 molg-1 to 6.7705x10-3 molg-1 and the kinetic equilibrium constant of adsorption, K, varied from 0.07828 to 0.7233 yet the surface area, A increased from 5.2702 x10-3 m2g-1 to 50.6700 x1...

American Ceramic Society Bulletin, 1998

A systematic study of clay samples from various deposits in Uganda indicates that these clays are... more A systematic study of clay samples from various deposits in Uganda indicates that these clays are kaolinitic-illitic with quartz as a minor mineral.

This study was carried out to determine the influence of tides to the quality of cave water in Za... more This study was carried out to determine the influence of tides to the quality of cave water in Zanzibar Island, part of Tanzania. It was to establish the effect of tidal change on the cave water quality using pH, temperature, EC, TDS, and nutrients (NO3-N, NH3-N, PO4) in the water as indicators. Overall results indicated that, the cave water quality changes with tides regardless of the fluctuation of the investigated parameters. Moreover, most of the tested parameters were not in range compared to those proposed by World Health Organization (WHO). This confirms that the quality of the cave water has been influenced by low and high tides due to high intrusion of the sea water entered in the caves.

International Journal of Chemical Engineering Research, 2017

Book Publisher International (a part of SCIENCEDOMAIN International), Jun 22, 2022

Current Topics on Chemistry and Biochemistry Vol. 1

American Journal of Analytical Chemistry, 2015

The available data have shown that acid-leached clays had sites for adsorption of impurities in o... more The available data have shown that acid-leached clays had sites for adsorption of impurities in oils. Data obtained on residual impurities in cotton and sunflower-seed oils bleached with the same clay materials produced linear Langmuir and Freundlich isotherms. The increase in constant, k with increase in both temperature of thermal activation and concentration of acid used to leach the clay, suggests that bleaching efficiency increased. The value of n decreased with increase in temperature of activation and concentration of acid used to leach the clay suggesting that bleaching capacity increased. The mineral compositions of the clays influenced their surface, structural and bleaching properties.

Bulletin of Pure & Applied Sciences- Geology, 2014

The Langmuir isotherms of 1-aminobutane in isohexane slurries showed increase in clay acidity wit... more The Langmuir isotherms of 1-aminobutane in isohexane slurries showed increase in clay acidity with increase in concentration of mineral acid used to leach the clay as well as the temperature at which the clay was thermally activated prior to experimentation involving adsorption of 1-aminobutane. The values of acidity for Central Uganda were low ranging from 0.07 mol/g to 0.32 mol/g yet those for clays from Eastern Uganda were high ranging from 0.1 mol/g to 1.85 mol/g. Based on acidity, pH, elemental and mineral compositions, the clays from Central Uganda were found to be kaolinites or halloysites, yet Eastern Uganda clays were resolved to contain nontronite and kaolinite.

Advances in Materials Physics and Chemistry, 2015

The results on the elemental and mineralogical compositions of clays from Central Uganda differed... more The results on the elemental and mineralogical compositions of clays from Central Uganda differed from those from the volcanic sediments of the Mt. Elgon in Eastern Uganda. Utilisation of the two types of clays should be strict after understanding their structural differences. Whereas elemental, mineralogical, DTA, IR, XRD and pH data on selected clays from Kumi, Nakawa, Seeta, Kajansi, Kawuku, Lwanda, Chodah and Umatengah indicated that they were kaolinites. Similar data on clays from Mutufu, Budadiri, Chelel and Siron indicated that they were largely smectites. The IR data accumulated on Kawuku, Kajansi, Lwada, Seeta, Chodah, Umatengah, Kumi and Nakawa clays revealed they were largely kaolinites yet that on Mutufu, Chelel, Budadiri and Siron clays indicated they were smectite-rich.

Bulletin of Pure & Applied Sciences- Chemistry, 2014

The efficiency of recycled clays to bleach oils measured by decrease in absorbance of bleached oi... more The efficiency of recycled clays to bleach oils measured by decrease in absorbance of bleached oils was largest when recycled clays had been calcined at 450°C and leached in boiling mixture of 20% acid strength for 16 hours. The Langmuir constant a varied from 0.4x10−2 to 16 x10−2 and b increased from 4.7x10−2 to 95.38x10−2. The Freundlich constant n increased from 8x10−3 to 33x10−3 and k from 3.9x10−2 to 11.8 x10−2 as concentration of acid increased. The enthalpy of adsorption increased from -6.7x10−2 to 22.2x10−2 kJmol−1.

This study was carried out to determine the chemical composition of cave water in Zanzibar Island... more This study was carried out to determine the chemical composition of cave water in Zanzibar Island, part of Tanzania. It was done by studying major cations (Ca, Mg, Na, K), and major anions (HCO3, SO4, Cl), in the water as indicators. Overall results indicated that, the cave water was influenced by marine and weathering contribution. However, weathering was more pronounced at Chomvi ndogo, Chomvi kubwa, and Miza wa Miza caves where it was more than 87% compared to Kilindi, Choweni and Makutani caves where it was less than 77%. Therefore marine contributed more in these last three caves. The trend for concentration contributed from marine water was similar to all sampling sites which was K<Ca<Mg<SO4<Na. The trend for weathering contribution was SO4< K Mg<Na<Ca at Chomvi ndogo, Chomvi kubwa and Miza wa Miza caves while at Kilindi, Choweni and Makutani caves the trend was Mg<K <SO4 <Na <Ca. These trends show that Na contributed more in marinogenic conten...

African Journal of Pure and Applied Chemistry, Apr 30, 2013

Hot smoking is among the oldest methods of preservation which mankind has used in food processing... more Hot smoking is among the oldest methods of preservation which mankind has used in food processing. Potential health hazards associated with smoked foods may be caused by carcinogenic components of wood smoke-mainly polycyclic aromatic hydrocarbons (PAHs) and their derivatives. This paper presents results based on the determination of PAHs in smoked Lates niloticus from three markets in Gulu district, northern Uganda. The samples were analysed using gas chromatography-mass spectrometry (GC-MS). The PAHs detected in the fish samples were acenaphthylene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, chrysene, benzo[b]fluoranthene and indeno [1,2,3cd]pyrene. The analysed samples showed PAH levels ranging from non-detectable (n.d) levels to 53.23 µg/kg of smoked fish. High molecular weight (HMW) PAHs constituted 71.1% by mass of the total PAHs detected and quantified in the samples, with indeno [1,2,3-cd]pyrene and benzo[b]fluoranthene featuring substantially in 95.8% of all the samples analysed. However, seven of the nine (77.8%) compounds detected in the samples were low molecular weight (LMW) PAHs. The higher concentrations of HMW PAHs suggest that the fish could have been smoked using soft wood or smoked for longer time and, also, may be due to the resistance of these PAHs to environmental degradation. Generally most of the samples analysed had ∑BaPeq and ∑PAH4 levels within the maximum acceptable risk limits of 5 and 30 µg/kg respectively, as recommended by European Commission Regulations for muscle meat of smoked fish. Hence the fish could therefore be deemed fit for human consumption.

Kaolin from the Buwambo deposit, located about 27 km north of Kampala (Uganda), has been analyzed... more Kaolin from the Buwambo deposit, located about 27 km north of Kampala (Uganda), has been analyzed for its mineralogical and chemical composition. The kaolin is derived from granite of the basement, which is exposed due to deeply weathered Buganda-Toro cover rocks. Kaolinite is the dominant mineral, with quartz and muscovite/illite as accessory minerals. Chemical data show that the kaolin is composed mainly of SiO2 and Al2O3, with the other oxides being present in trace amounts. The depletion in Ti, Fe, Mn, Mg, Ca, Na, and K not only shows the extent of the kaolinization, but also gives Buwambo kaolin its almost white color. The kaolinization and weathering processes have enriched Ni and depleted other trace ele-ment contents in the Buwambo kaolin. The chondrite-normalized rare earth element (REE) patterns show enrichment in the light REEs, with a negative Ce anomaly. The REE pattern and the content of the other trace elements, show evidence of alteration and weathering processes rel...

African Journal of Pure and Applied Chemistry, 2013

International Journal of Scientific Research, Mar 1, 2013