Theses and Dissertations
Permanent URI for this collection
Browse
Browsing Theses and Dissertations by Author "Ayinde, W. B."
Now showing 1 - 3 of 3
Results Per Page
Sort Options
Item Open Access Fabrication of Biomass-Polymeric Adsorbent for the Removal of Selected Metal Species, Nutrients and Pathogens in Aqueous Solutions(2021-06-23) Mhlarhi, Nsovo; Gitari, W. M.; Tavengwa, N. T.; Ayinde, W. B.Environmental pollution is a major problem that has increased rapidly many decades ago. This has affected the quality of water and has created serious environmental, social, economic, and political issues. Water pollution is mainly caused by chemical species such as chromium and cadmium; nutrients (nitrates and phosphates) and pathogens from natural and anthropogenic activities which cause health problems and in some cases death to both human and aquatic organisms. South Africa is a water-scarce country, and many of the water resources are threatened by human factors. In many cases, most of the water-treatment plants have been abandoned and are in a dire state which often leads to alternative sources of water for domestic activities. The consumption of this untreated water resulted in a lot of diseases and child mortality. In this sense, the biosorption process using a sustainable biomaterial for removing these pollutants has gained prominence due to several advantages it has over other technologies in solving these environmental menaces. The present study successfully developed and evaluated a systemic biomass polymeric adsorbent for the removal of toxic metals such as chromium and cadmium ions, nutrients (nitrate and phosphate ions), and pathogens from aqueous solutions. The bio-sorbent was fabricated by incorporating biomass (grapefruit peels) and algae (diatom) on a polymeric network for improved overall properties towards the selective toxic chemical and microbial pollutants. The structural and morphological properties of the various adsorbents were done by FTIR which show the various functional groups present in the adsorbents responsible for the sorption processes of Cr6+, Cd2+, and PO43-. The SEM-EDS showed different shapes and the elemental compositions that constitute each of the adsorbents. Furthermore, the XRD revealed an amorphous structure for grapefruit peel powder (GFP), diatom biomass, grapefruit peel/diatom (GFP/diatom), while the overall synthesized poly-phenylenediamine based biomass (pPD/GFP/diatom) was crystalline. The batch sorption studies on the uptakes of Cr6+, Cd2+, and PO43- from aqueous solutions by the various adsorbents were investigated as a function of pH, contact time, adsorbent dosage, and initial concentration. The respective adsorption kinetics processes by the GFP, diatom biomass, GFP/diatom, and pPD/GFP/diatom sorbent materials on Cr6+, Cd2+, and PO43- ions revealed that physisorption and chemisorption mechanisms were responsible for the adsorption processes as well governed by intra-particle diffusions. Freundlich and Langmuir adsorption isotherm models proved to be responsible for the sorption of Cr6+, Cd2+, and PO43- ions by the different adsorbents. The thermodynamic data revealed that the adsorption process was spontaneous and feasible in all the adsorbents across all temperatures. Furthermore, the antimicrobial activity of Escherichia coli, Staphylococcus aureus, and Klebsiella pneumoniae by GFP, diatom biomass, GFP/diatom, and pPD/GFP/diatom showed that they had antimicrobial potency. Overall, these adsorbents present a promising ability to remediate inorganic pollutants in wastewater, allowing for the protection of the environment and living organisms.Item Embargo Synthesis of Zr4+/Ag+ metal oxides modified zeolite for application in fluoride and pathogens removal from water(2024-09-06) Nemakanga, Selby; Mudzielwana, R.; Ayinde, W. B.People living in developing nations are challenged by acute water scarcity, hence they often rely on groundwater as their primary drinking water sources. Unfortunately, in most cases, groundwater is often contaminated with high levels of fluoride and pathogens, posing a significant health risk. This dissertation aims to synthesize Zr4+/Ag+ metal oxides modified zeolite adsorbent for use in fluoride and pathogens removal from water. The first section of this research aimed at optimizing the synthesis of zeolite from bentonite clay using the response surface methodology (RSM). The process involved alkali dissolution of calcined bentonite clay through ultrasonication, followed by hydrothermal treatment to obtain zeolite. The ultrasonication conditions were optimized by varying NaOH concentration (0.5 to 2.5 M) and aging time (10 to 120 minutes). Temperature (70 °C to 140 °C) and time (1.5 to 6 hours) were evaluated for hydrothermal treatment. The X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDX) and Fourier transform infrared (FTIR) analysis were used to characterize the obtained materials, revealing that crystallinity of the obtained synthesized materials increased at higher hydrothermal temperatures and times. Furthermore, the XRD analysis indicated there was the formation of zeolite NaP phases at lower temperatures and times, while higher temperatures and times led to hydroxy sodalite mineral phases. Preliminary defluoridation experiments were conducted on all hydrothermally treated samples, with the sample prepared at 2 hours sonication, 105°C hydrothermal treatment, and 1 hour 30 minutes exhibiting a capacity for adsorbing fluoride of 0.19 mg/g hence, this zeolite was used subsequent experiments. The second chapter of results presented the evaluated effectiveness of the synthesized zeolite NaP on fluoride and pathogen removal. Batch experiments were conducted to assess zeolite NaP's effectiveness in removing fluoride from water under various operating conditions while the well-assay diffusion method was used to study the antimicrobial potency of the zeolite. The optimum conditions for achieving maximum fluoride adsorption were identified as a contact time of 60 minutes, an initial concentration of 6.2 mg/L using a synthetic fluoride solution, an initial pH of 2, and an adsorbent dosage of 0.5 g/100 mL. Under these conditions, the maximum adsorption capacity reached 0.16 mg/g. Additionally, it was determined that the fluoride adsorption process followed a chemisorption mechanism, as evidenced by the fitting of experimental data to a pseudo-second-order kinetic model. Moreover, the adsorption isotherm data fitted well with the Langmuir model. This indicates that fluoride adsorption occurred on a surface in a single layer, with a limit on the number of active sites at any given time. Antimicrobial assessments revealed that zeolite NaP lacked v potency against gram-negative E. coli and gram-positive S. aureus strains. In conclusion, zeolite NaP demonstrated minimal defluoridation efficiency and no antimicrobial efficacy. The chapter suggests enhancing fluoride adsorption, antimicrobial potency, and material reusability through the introduction of cations into the zeolite frameworks. The third chapter of results focused on the modification of zeolite NaP by incorporating zirconium/silver metal oxides to enhance its efficacy in removing fluoride and pathogens from water. The Zr4+/Ag+ modified zeolite NaP was prepared using 0.5 M and 0.3 M ZrCl4 and AgNO3 respectively. The mixture of 10 g of calcined bentonite, 2 M of NaOH, and Zr and Ag solutions was subjected to ultrasonication for 2 hours followed by hydrothermal treatment at 105 °C for 90 minutes. The obtained material was therefore characterized using XRD, XRF, FTIR, Particle Distribution Analysis, and SEM-EDS. Defluoridation and antimicrobial potency were evaluated through batch adsorption experiments and well-assay diffusion method, respectively. Under optimal conditions, including a pH of 6 ± 0.5, a contact time of 270 minutes, an initial fluoride concentration of 6.2 mg/L, and an adsorbent dosage of 0.5 g/100 mL at an agitation speed of 250 rpm, the modified zeolite demonstrated a peak fluoride removal percentage of approximately 50%. The data fitted better to the pseudo-second-order kinetic model suggesting the dominance of chemisorption as the fluoride removal mechanism while adsorption isotherm data followed the Langmuir isotherm model suggesting that adsorption occurred on a monolayered surface for the Zr4+/Ag+ modified zeolite. Antimicrobial studies revealed a 15 mm and 12 mm zone of inhibition against the gram-negative E. coli and gram-positive S. aureus strains, respectively. In conclusion, the synthesized zeolite functionalized with zirconium and silver metal oxides exhibited improved fluoride removal efficiency and antimicrobial potency. Further research is recommended to improve the properties of synthesized zeolite for better removal of fluoride and pathogens from water.Item Open Access Synthesis, characterization of a sustainable Fe/Ce Doped Poly-(para-phenylenediamine) adsorbent and its potential for simultaneous removal of fluoride, arsenite and pathogens in aqueous(2021-06-23) Munzhelele, Elisa Pandelani; Gitari, W. M.; Ayinde, W. B.Water pollution due to natural and anthropogenic sources remains one of the global problems which require attention due to its long-term effect on human and the environment. Prolonged exposure to chemical and microbial contaminated water may cause both acute and chronic health hazards. The occurrence of arsenic, fluoride, and pathogen in drinking water has raised severe health issues to human beings. The health impact of consuming arsenite, fluoride, and pathogens has resulted in adverse health effects such as skin cancer, dental and skeletal fluorosis, and water-borne diseases. Thus, the present research has been conducted for their simultaneous removal from water bodies. Generally, various methods have been developed to remediate water pollution which includes membrane filtration, ion-exchange, and adsorption. Within, these developed methods adsorption methods have gained attention due to the use of various materials including natural adsorbents such as clays, agro-waste, etc, and novel conjugated polymeric composites because they are easy to operate, less expensive, and eco-friendly. The use of hydrous oxides (Fe, Ce, and Mn) of rare earth elements have been studied and have shown high affinity for fluoride, arsenite, and other toxic elements. This study focused on the systemic synthesis of novel conjugated polymeric adsorbents by the incorporation of Fe/Ce oxides onto a phenylenediamine (pPD) polymer matrix through chemical co-polymerization route and its fluoride, arsenic and pathogen removal potentials at optimal conditions in an aqueous solution evaluation. The morphology and structural analysis of the synthesized Fe; Ce and Fe/Ce doped pPD were comparatively evaluated using the Fourier Transform Infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), energy dispersive-X-ray spectroscopy (EDS), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Modified Fe/Ce was successfully incorporated onto the pPD matrix as confirmed by the different morphological characterizations. The functional groups of pPD were not altered by the incorporation of the metal oxides as shown by the FTIR results. The synthesized material has an irregular shape within an average particle size between 20 -100 nm, with a low crystalline phase pattern when compared to the amorphous plain pPD. Relatively, the optimized composite samples of 2.5 % Fe-pPD, 5 % Ce-pPD and 1:1 Fe/Ce-pPD (2.5%) showed efficient and higher fluoride and arsenic sorption as well as disinfection ability against water borne pathogens. ii Moreover, the effect of contact time, adsorbent dosage, pH, initial concentration, temperature, and co-ions was assessed to determine their significance in Fˉ and As3+ removal in aqueous solution. The obtained results revealed that all the reported experimental conditions have significant effect on pollutants uptake. The kinetic data for 2.5 % Fe-pPD, 5 % Ce-pPD and 1:1 Fe/Ce-pPD composite fitted well to pseudo-second-order kinetic model for both Fˉ and As3+. Thus, chemo-sorption is the limiting step for fluoride and arsenite uptake. However, the intra-particle diffusion plot has shown three distinctive phases for the synthesized adsorbents, thus, the adsorption process occurs with more than one sorption mechanism step. Equally, the Freundlich isotherm model better described the sorption process of the synthesized materials, hence, adsorption process was occurring on a heterogeneous surface. The fitness of the kinetics and isotherm data was validated by lower values of goodness of fit (error factors). Thermodynamically, the removal process for both pollutants when using the 2.5 % Fe-pPD and 1:1 Fe/Ce-pPD adsorbents was endothermic, whereas for 5 % Ce-pPD was exothermic and endothermic (As3+ (1.86, 2.11, 4.71 mg/g) and Fˉ(6.79, 13.29, 14.75 mg/g)). The synthesized adsorbents can be regenerated up to four cycles when using H2O, NaOH and HCL, with H2O being the best regenerant for both adsorbents. Further, antibacterial results showed that 2.5 % Fe-pPD, 5 % Ce-pPD and 1:1 Fe/Ce-pPD (25 % :2.5%) composite inhibited the growth of common water-borne bacterial strains. Thus, the modified composites have not only portrayed the potential ability for metal ions removal but also showed strong antimicrobial activity against water-borne pathogens.