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  • 1.
    Bakyayita, Grace Kizito
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering. Makerere University, Kyambogo University.
    Batch Sorption Studies of Aqueous Cadmium and Lead from Contaminated Water onto Selected Biosorbents2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Groundwater, wastewater, surface runoff and surface water samples from Lake Victoria basin, Uganda was assessed for trace metals contamination. Untreated, base-treated and peroxide-treated biosorbents from Albizia coriaria, Coffea canephora, Cyperus papyrus, Erythrina abyssinica and Musa spp were investigated for removal of selected trace metals from contaminated water in batch studies. The assessed shallow groundwater and surface water was contaminated with iron and manganese. Selected speciation studies using Visual MINTEQ showed that in leachates from Municipal dumpsites 74% of the metal ions were bound to DOM, 13% were free ions and 13% were in inorganic forms moreover for urban streams 37% of the metal ions were bound to DOM, 44% were free ions and 19% were in inorganic forms. The metal levels in surface water, landfill leachate and surface runoff showed elevated levels and revealed increased risks to environmental health. Risk analysis based on the Swedish EPA showed that varied risks of negative effects in 30% – 76% of the sample sites ranging from high to increased risk in surface water whereas the results from Bio-met tool showed potential risk to toxicity effects of Cu2+, Ni2+, Zn2+ and Pb2+ in 15.3% - 30.8% surface water samples and 8.3% - 62.5% groundwater samples. Batch sorption studies revealed that the optimal conditions for Cd2+ and Pb2+ ions uptake were; pH 3.5 – 5.0 for contact time 3.0 – 3.5 hours and biosorbent dosage 10 – 12.5 g/L. Base-treated biosorbents showed 10 – 17 % sorption enhancement for Cd2+ ions and 1.6 – 2.3 % uptake reduction for Pb2+ ions. The biomass negative potential for binding base cations was in the order; Musa spp. > A. coriaria > E. abyssinica and base treatment reduced DOC leaching from biosorbents in the order; E. abyssinica > A. coriaria > Musa spp. Speciation studies showed that more ions were complexed to DOC in solutions at various pH levels. The maximum sorption intensities for both Cd2+ and Pb2+ ions uptake onto biomass occurred for low initial metal concentration; 5 mg/L. Freundlich model best fitted data for Pb2+ ions ions uptake whereas Temkin model fitted the sorption data for Cd2+ ions onto both treated and untreated biomass. For peroxide treated biomass, the maximum sorption efficiencies for both Cd2+ and Pb2+ ions were between 95.2 – 98.7% for C.canephora, 79.9 – 92.2% for Musa spp. and 42.0 – 91.3% for C.papyrus in non-competitive media and 90.8 – 98.0% for C.canephora, 56.4 – 89.3% for Musa spp. and 19.5 – 90.4% for C.papyrus in competitive media. The Langmiur model fitted non-competitive sorption data with 0.769 ≤ R2 ≥ 0.999 and the Freundlich model fitted competitive sorption data with 0.867 ≤ R2 ≥ 0.989. The pseudo second order kinetic model fitted the sorption data for Cd2+ and Pb2+ ions for untreated, peroxide treated and base treated biomass with 0.917 ≤ R2 ≥ 1.000. The sorption of trace metals was a complex potentially monolayer chemisorption with heterogeneous surface properties exhibited. In competitive sorption, sorption suppression effects observed were greater for Cd2+ than Pb2+ ions. The comparative studies on sorption performance presented agreement and no significant difference between the untreated and base treated biosorbents. 

  • 2.
    Bakyayita, Grace Kizito
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering. Makerere Univ, Dept Civil & Environm Engn, Kampala, Uganda..
    Norrström, Ann-Catrine
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Kulabako, R. N.
    Makerere Univ, Dept Civil & Environm Engn, Kampala, Uganda..
    Assessment of Levels, Speciation, and Toxicity of Trace Metal Contaminants in Selected Shallow Groundwater Sources, Surface Runoff, Wastewater, and Surface Water from Designated Streams in Lake Victoria Basin, Uganda2019In: Journal of Environmental and Public health, ISSN 1687-9805, E-ISSN 1687-9813, article id 6734017Article in journal (Refereed)
    Abstract [en]

    The levels, speciation of elements, and toxicity of selected trace metals as well as other parameters in selected surface water, shallow groundwater sources, landfill leachate, and associated surface runoff in the Lake Victoria basin, Uganda, were studied. The WHO guidelines, Ugandan standards, Canadian guidelines and Swedish EPA were used for assessment. The shallow groundwater was acidic with pH values below 6.5. The pH, dissolved organic carbon, flouride, and sulphate levels for all springs were below the guideline values although 52.8% was contaminated with nitrates while 39% was contaminated with chloride ions. Some surface water samples had levels of major elements, such as iron, chromium, aluminium, and manganese, above the guideline values. Speciation studies showed that 74% of the metal ions was bound to dissolved organic matter in surface water, whereas in landfill leachates, the dominant ionic species was metal hydroxides or fulvic acid bound. Risk analysis based on the Swedish EPA showed varied risks of negative effects in 30%-76% of the sample sites ranging from high to increased risk in surface water, whereas the results from modelling sorption data using the Bio-met tool showed potential risk to toxicity effects of Cu2+, Ni2+, Zn2+, and Pb2+ in 15.3%-30.8% surface water samples and 8.3%-62.5% groundwater samples.

  • 3.
    Bakyayita, Grace Kizito
    et al.
    KTH, School of Architecture and the Built Environment (ABE). Makerere University and Kyambogo University.
    Norrström, Ann-Catrine
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Environmental Geochemistry and Ecotechnology. KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Kulabako, Robinah N.
    KTH, School of Architecture and the Built Environment (ABE). Department of Civil Engineering, CEDAT, Makerere University.
    Assessment of levels, speciation and toxicity of trace metal contaminants in selected shallow groundwater sources, surface runoff, wastewater and surface water from designated streams in Lake Victoria Basin, Uganda2019In: Hindawi Journal of Environmental and Public Health, ISSN 1687-9813, p. 1-18, article id 6734017Article in journal (Refereed)
    Abstract [en]

    The levels, speciation of elements and toxicity of selected trace metals as well as other parameters in selected surface water, shallow groundwater sources, landfill leachate and associated surface runoff in the Lake Victoria basin, Uganda were studied. The WHO guidelines, Ugandan standards, Canadian guidelines and Swedish EPA were used for assessment. The shallow groundwater was acidic with pH values below 6.5. The pH, dissolved organic carbon, flouride and suphate levels for all springs were below the guideline values although 52.8% were contaminated with nitrates while 39% were contaminated with chloride ions. The water samples with had levels of major elements; iron, chromium, aluminium and manganese above the guideline values. Speciation studies showed that 74% of the metal ions were bound to dissolved organic matter in surface water whereas in landfill leachates the dorminant ionic species were metal hydroxides or fluvic acid bound. Risk analysis basing on the Swedish EPA showed that varied risks of negative effects in 30% – 76% of the sample sites ranging from high to increased risk in surface water whereas the results from Bio-met tool showed potential risk to toxicity effects of Cu2+, Ni2+, Zn2+and Pb2+ in 15.3% - 30.8% surface water samples and 8.3% - 62.5% groundwater samples.

  • 4.
    Bakyayita, Grace Kizito
    et al.
    KTH, School of Architecture and the Built Environment (ABE). Makerere University, Kyambogo University.
    Norrström, Ann-Catrine
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering (moved 20130630), Environmental Geochemistry and Ecotechnology. KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Kulabako, Robinah N.
    KTH, School of Architecture and the Built Environment (ABE). Department of Civil Engineering, CEDAT, Makerere University.
    Characterisation and application of untreated and base-treated biosorbents from Albizia coriaria, Erythrina abyssinica and Musa spp. in the uptake of Cd (II) and Pb (II) ions from contaminated waterManuscript (preprint) (Other academic)
    Abstract [en]

    The barks of Albizia coriaria, Erythrina abyssinica and peels of Musa spp. were studied in batch for removal of aqueous Cd2+ and Pb2+ ions at pH 4.5, agitation time 3.0 hours for 10 g/L biomass dosage. The biosorbents’ surfaces contained an array of heterogeneous sorption sites for metal ions. The trace metals in the biomass were in trace amounts.Results form XRD showed that organic species in the biosorbent surfaces were electron rich species expected to play part in the metal ions uptake. The biomass negative potential for binding base cations was in the order; Musa spp. > A. coriaria > E. abyssinica and base treatment reduced DOC leaching from the biosorbents in the order; E. abyssinica > A. coriaria > Musa spp. Speciation studies showed that more ions were complexed to DOC in solutions at various pH levels. The maximum sorption intensities for both Cd2+ and Pb2+ ions uptake onto biomass was highest for lowest initial metal concentration; 5 mg/L. Musa spp had the highest soprtion performance for both Cd2+ and Pb2+ ions. Freundlich model best fitted data for Pb2+ ions uptake whereas Temkin model fitted the sorption data for Cd2+ ions onto both treated and untreated biomass.

  • 5.
    Bakyayita, Grace Kizito
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering. Makerere univ.
    Norrström, Ann-Catrine
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Kulabako, Robinah Nakawunde Akawunde
    Makerere univ.
    Competitive and Noncompetitive Batch Sorption Studies of Aqueous Cd(II) and Pb(II) Uptake onto Coffea canephora Husks, Cyperus papyrus Stems, and Musa spp. Peels2015In: Journal of Chemistry, ISSN 2090-9063, E-ISSN 2090-9071, article id 696098Article in journal (Refereed)
    Abstract [en]

    Coffea canephora, Cyperus papyrus, and Musa spp. were studied for competitive and noncompetitive removal of aqueous Cd2+ and Pb2+. The optimal conditions were pH 4.5 and agitation time 3.0 hours. Biomass constituent ions showed no interference effects whereas cation exchange capacity values corresponded to the sorption efficiencies. XRD spectroscopy revealed surface oxygen and nitrogen groups that provide binding sites for metal ions. The maximum sorption efficiency ranges for metal ions in noncompetitive media were 95.2-98.7% for C. canephora, 42.0-91.3% for C. papyrus, and 79.9-92.2% for Musa spp. and in competitive sorption 90.8-98.0% for C. canephora, 19.5-90.4% for C. papyrus, and 56.4-89.3% for Musa spp. The Pb2+ ions uptake was superior to that of Cd2+ ions in competitive and noncompetitive media. In competitive sorption synergistic effects were higher for Cd2+ than Pb2+ ions. The pseudo-second-order kinetic model fitted experimental data with 0.917 <= R-2 >= 1.000 for Pb2+ ions and 0.711 <= R-2 >= 0.999 for Cd2+ ions. The Langmuir model fitted noncompetitive sorption data with 0.769 <= R-2 >= 0.999; moreover the Freundlich model fitted competitive sorption data with 0.867 <= R-2 >= 0.989. Noncompetitive sorption was monolayer chemisorption whereas competitive sorption exhibited heterogeneous sorption mechanisms.

  • 6.
    Bakyayita Kizito, Grace
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Equilibrium and Kinetic Batch Studies of Cadmium and Lead sorption using Low Cost Biosorbents2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Agricultural wastes; Albizia coriaria, Coffea canephora, Cyperus papyrus, Erythrina abyssinica and Musa spp were evaluated for uptake of aqueous Cd2+ and Pb2+ ions in single- and binary-component solutions. Untreated, base-treated and peroxide-treated biomasses were employed in batch studies. The optimal conditions for Cd2+ and Pb2+ ions biosorption were  pH 3.5 – 5 for contact time 3.0 – 3.5 hours and biosorbent dosage 10 – 12.5 g/L. Base-treated biosorbents showed a 10 – 17 %  sorption enhancement for Cd2+ ions and a 1.6 – 2.3 % uptake reduction for Pb2+ ions. The sorption capacities for Cd2+ and Pb2+ ions for base-treated biosorbents were between 1.738 and 1.760 mg g-1 compared to 1.415 – 1.539 mg g-1 for untreated materials. The maximum biosorption of peroxide treated materials in single component media was between 0.819 and 1.595 mg/g for Pb2+ ions and between 0.044 and 1.343 mg/g for Cd2+ ions while in binary component media it was between 0.472 and 1.303 mg/g for Pb2+ ions and between 0.008 and 0.195 mg/g for Cd2+ ions. The pseudo-second order kinetic model suitably fitted the Cd2+ and Pb2+ ions biosorption data with regression coefficients (R2); 0.892 – 1.000 for peroxide-treated materials and 0.9784 – 0.9999 for base-treated biosorbents which implied that the biosorption was mainly a chemisorption process. The base treated biosorbents had better sorption performance for Cd2+ ions than peroxide treated materials and untreated biomass whereas the order for Pb2+ ions biosorption was untreated > base treated > peroxide treated materials. All materials showed superior selectivity for Pb2+ ions biosorption in comparison to that of Cd2+ ions in single- and binary-component media. A. coriaria performed best of the base treated biosorbents while C. canephora performed best amongst peroxide treated materials for Cd2+ and Pb2+ ions biosorption in single-and binary-component media. In the competitive biosorption, Cd2+ ions showed higher synergistic effects than Pb2+ ions although Pb2+ ions were preferentially sequestered even when the Cd2+:Pb2+ ions ratio was increased through 3:2, 2:1, 3:1 and 5:1. Of the three isotherm models evaluated against the experimental data, the Langmuir model generally fitted the sorption data for both metals. Regression coefficients for the Langmuir model were; 0.983 ≤ R2 ≥ 1.000 for single-component and 0.939 ≤ R2 ≥ 1.000 for binary-component solutions which revealed that the biosorption was potentially monolayer. The biosorption equilibrium coefficient                          values and change in Gibbs’ free energy  values showed that Pb2+ ions biosorption was more thermodynamically favoured than that of Cd2+ ions in single-component and binary-component media. The materials studied displayed potential for use as biosorbents for remediation of aqueous Cd2+ and Pb2+ ions.

  • 7.
    Bakyayita Kizito, Grace
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Kulabako, Robinah
    2Department of Civil and Environmental Engineering, Makerere University, Uganda.
    Nalubega, Mai
    Water and Sanitation Department, African Development Bank, Tunis, Tunisia.
    Norrström, Ann-Catrine
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Equilibrium batch studies for biosorption of Cd(II) and Pb(II) ions from single-and binary-component aqueous mediaManuscript (preprint) (Other academic)
  • 8.
    Bakyayita Kizito, Grace
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Norrström, Ann-Catrine
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Nalubega, Mai
    Water and Sanitation Department, African Development Bank, Tunis.
    Robinah, Kulabako
    Department of Civil and Environmental Engineering, Makerere University, Uganda .
    Kinetic studies of Cd (II) and Pb (II) ions biosorption from aqueous media using untreated and chemically treated biosorbents2014In: Water Science and Technology: Water Supply, ISSN 1606-9749, E-ISSN 1607-0798, Vol. 69, no 11, p. 2230-2236Article in journal (Refereed)
    Abstract [en]

    Untreated and chemically treated Albizia coriaria, Erythrina abyssinica and Musa spp were studied in batch for uptake of Cd2+ and Pb2+ ions at pH 2.0–9.0 and agitation time; 30–390 min. Optimum biosorption conditions were; pH 4 for Pb2+ ions and pH 5 for Cd2+ ions, contact time was 3.5 hours at 24 ± 1 °C for 10 mg/L biosorbent dosage and initial metal ions concentration of 20 mg/L. Chemical treatment had a 10–17% biosorption efficiency enhancement for Cd2+ ions and a 1.6–2.3% reduction effect for Pb2+ ions. The sorption capacities for Cd2+ and Pb2+ ions for treated biosorbents were between 1.760–1.738 mg g−1 compared to 1.415–1.539 mg g−1 for untreated materials. The pseudo second order model suitably fitted the Cd2+ and Pb2+ ions biosorption data with regression coefficients (R2) between 0.9784–0.9999. Fitting of the Ho model to the experimental data showed that the biosorption mechanism for both metal ions studied was mainly a chemisorption process. Therefore, treated A. coriaria, E. abyssinica and Musa spp were potential biosorbents for remediation of Cd2+ ions and the untreated materials suitable for removing Pb2+ ions from contaminated aqueous media.

  • 9.
    Grace, Bakyayita Kizito
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Nalubega, Mai
    2Water and Sanitation Department, African Development Bank, Tunis.
    Norrström, Ann-Catrine
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Kulabako, Robinah
    3Department of Civil and Environmental Engineering, Makerere University, Uganda.
    Single and binary biosorption kinetics for Cd and Pb from aqueous media using Coffea canephora, Cyperus papyrus and Musa sppManuscript (preprint) (Other academic)
1 - 9 of 9
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