Department of Chemical and Earth Sciences

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http://hdl.handle.net/20.500.11837/159
The Department of Chemical and Earth Sciences collection provides access to the academic and research outputs of staff and students. This collection includes research publications, conference papers, and examination question papers. The Department encompasses a broad range of disciplines, including Geography and Environmental Studies, Applied Remote Sensing & Geographic Information Systems (GIS), Geology, and Pure and Applied Chemistry. By integrating theoretical knowledge with practical laboratory and field-based research, the Department equips students with analytical, technical, and problem-solving skills to address scientific, environmental, and societal challenges. Through the preservation and dissemination of these resources, the collection supports teaching, learning, and research, while fostering innovation, environmental stewardship, and sustainable development within the University and the wider community.

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Browsing Department of Chemical and Earth Sciences by Subject "Adsorption"

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    Influence of different chaotropic salts on etched mesoporous silica nanoparticles for the removal of bacteria DNA conveying antibiotic resistance genes from hospital wastewater
    (Elsevier, 2022-08-15) Ezeuko, S.; Ojemaye, O.; Okoh, OO.; Okoh, A.
    The adsorption of bacteria DNA onto mesoporous silica nanoparticles in their original state has been a great challenge due to the high negative charge exhibited by both the DNA and silica surface. The aim of this study is to mediate bacteria DNA onto synthesized mesoporous silica nanoparticles (E-MSN) in combination with different chaotropic salts. E-MSN was synthesized via chemical etching techniques using sodium dodecyl sulfate (SDS) as an etchant. SDS was used to remove unwanted layers and provides a convenient platform for underlining mesopore with different chaotropic salts. Scanning electron microscopy (SEM) coupled with energy-dispersive xray spectroscopy (EDX), Fourier-transformed infrared spectroscopy (FTIR), x-ray diffraction spectroscopy (XRD), and point of zero charges (PZC) results showed that synthesized etched mesoporous silica nanoparticles have a crystalline, non-spherical shape and elemental composition of silica at approximately 2 Kev, functional groups that depict silica particles. Molecular characterization of extracted genes showed that Enterococcus faecium harbors tetA, tetM, and ermB in 201bp, 158bp, and 320bp, with the DNA purity ranging from 1.7 to 1.9. DNA adsorption was studied as a function of operating parameters in different solutions of chaotropic salts (sodium chloride (NaCl), 2 M guanidine HCl (CH5N3.HCl), and urea ((NH3)2CO). Among the different chaotropic salts used to compliment the silica nanoparticles, 2 M guanidine HCl exhibited the highest percentage (%) removal efficiency (90%) compared to urea (75%) and sodium chloride (70%) in simulated water and hospital wastewater. Experimental results revealed that the pseudo-second-order kinetic and Sips isotherm is the best fit for the adsorption process. Therefore, mesoporous silica nanoparticles enhanced by different chaotropic salts in this study showed that this material might be promising and economical for the uptake of bacteria DNA conveying antibiotics resistance genes from hospital wastewater.
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    Preparation and evaluation of Lignocellulose-Montmorillonite nanocomposites for the adsorption of some heavy metals and organic dyes from aqueous solution
    (University of Fort Hare, 2011) Bunhu, Tavengwa; Tichagwa, L
    The need to reduce the cost of adsorption technology has led scientists to explore the use of many low cost adsorbents especially those from renewable resources. Lignocellulose and montmorillonite clay have been identified as potentially low cost and efficient adsorbent materials for the removal of toxic heavy metals and organic substances from contaminated water. Montmorillonite clay has good adsorption properties and the potential for ion exchange. Lignocellulose possesses many hydroxyl, carbonyl and phenyl groups and therefore, both montmorillonite and lignocellulose are good candidates for the development of effective and low cost adsorbents in water treatment and purification. The aim of this study was to prepare composite materials based on lignocellulose and montmorillonite clay and subsequently evaluate their efficacy as adsorbents for heavy metal species and organic pollutants in aqueous solution. It was also important to assess the adsorption properties of the modified individual (uncombined) lignocellulose and montmorillonite. Lignocellulose and sodium-exchanged montmorillonite (NaMMT) clay were each separately modified with methyl methacrylate (MMA), methacrylic acid (MAA) and methacryloxypropyl trimethoxysilane (MPS) and used as adsorbents for the removal of heavy metals and dyes from aqueous solution. The lignocellulose and NaMMT were modified with MMA, MAA and MPS through free radical graft polymerisation and/or condensation reactions. NaMMT was also modified through Al-pillaring to give AlpMMT. The materials were characterised by fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and small angle X-ray scattering (SAXS) and characterisation results showed that the modification of the montmorillonite with MAA, MMA and MPS was successful. The modified lignocellulose and montmorillonite materials were evaluated for the adsorption of heavy metal ions (Cd2+ and Pb2+) from aqueous solution by the batch method. The adsorption isotherms and kinetics of both Cd2+ and Pb2+ onto the NaMMT clay, AlpMMT and lignocellulose materials are presented. The Langmuir isotherm was found to be the best fit for the adsorption of both heavy metals onto all the adsorbents. AlpMMT showed very poor uptake for heavy metals (both Cd2+ and Pb2+). PMMAgMMT, PMAAgMMT, PMAAgLig and PMPSgLig showed improved adsorption for both heavy metals. The mechanism of heavy metal adsorption onto the adsorbents was best represented by the pseudo second-order kinetic model. PMPSgLig, NaMMT and AlpMMT showed relatively high adsorption capacities for methyl orange, while the adsorption of neutral red was comparable for almost all the adsorbents. Neither the Langmuir model nor the Freundlich model was found to v adequately describe the adsorption process of dyes onto all the adsorbents. The pseudo second-order model was found to be the best fit to describe the adsorption mechanism of both dyes onto all the adsorbents. The modification of lignocellulose and montmorillonite with suitable organic groups can potentially produce highly effective and efficient adsorbents for the removal of both heavy metals and dyes from contaminated water. Novel adsorbent composite materials based on lignocellulose and montmorillonite clay (NaMMT) were also prepared and evaluated for the removal of pollutants (dyes and heavy metals) from aqueous solution. The lignocellulose-montmorillonite composites were prepared by in situ intercalative polymerisation, using methyl methacrylate, methacrylic acid and methacryloxypropyl trimethoxysilane (MPS) as coupling agents. The composite materials were characterised by FTIR, TGA, TEM and SAXS. SAXS diffractograms showed intercalated nanocomposites of PMMAgLig-NaMMT and PMAAgLig-NaMMT, whereas PMPSgLig-NaMMT showed a phase-separated composite and the same results were confirmed by TEM. The lignocellulose-montmorillonite composites were assessed for their adsorption properties for heavy metal ions (Cd2+ and Pb2+) and dyes (methyl orange and neutral red) from aqueous solution. Among these composite materials, only PMAAgLig-NaMMT showed a marked increase in the uptake of both Cd2+ and Pb2+ relative to lignocellulose and montmorillonite when used independently. The adsorption data were fitted to the Langmuir and Freundlich isotherms, as well as to the pseudo first-order and pseudo second-order kinetic models. The data were best described by the Langmuir isotherm and the pseudo second-order kinetic model. On the adsorption of dyes, only PMPSgLig-NaMMT showed enhanced adsorption of methyl orange (MetO) compared with lignocellulose and montmorillonite separately. The enhanced adsorption was attributed to the synergistic adsorption due to the presence of MPS, lignocellulose and NaMMT. Competitive adsorption studies were carried out from binary mixtures of MetO and Cd2+ or Pb2+ in aqueous solution. The adsorption process of MetO onto the composite material was found to follow the Freundlich adsorption model, while the mechanism of adsorption followed both the pseudo first-order and pseudo second-order models. This particular composite can be used for the simultaneous adsorption of both heavy metals and organic dyes from contaminated water. The adsorption of neutral red to the composite materials was comparable and the pseudo second-order kinetic model best described the adsorption mechanism.
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    The effectiveness of silver nanoparticles as a clean-up material for water polluted with bacteria DNA conveying antibiotics resistance genes: Effect of different molar concentrations and competing ions
    (Elsevier, 2022-07-22) Ezeuko CS; Ojemaye O; Okoh OO; Okoh A
    This study employed silver nanoparticles to remove DNA conveying antibiotic resistance genes from water. Three different molar concentrations of silver nanoparticles represented as BD1 (0.1M), BD2 (0.5 M), and BD3 (1.0 M) were synthesized as adsorbents and evaluated in a batch adsorption system for the removal of bacteria DNA conveying antibiotic resistance genes from simulated aqueous solution. The authenticity of the adsorbents was confirmed by characterization techniques using Fourier transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM) coupled with energy-dispersive x-ray spectroscopy (EDX), and x-ray diffraction spectroscopy (XRD) indicated the successful synthesis of these AgNPs. Adsorption studies involving the different operating conditions on the synthesized materials showed that pH affects the removal of DNA with increased removal efficiency observed at acidic pH (removal percentage ranging from 50.26-87.61%, 65.80-87.79%, and 69.23-87.92% for BD1, BD2, and BD3 respectively). Maximum adsorption equilibrium was achieved after 180, 195, and 225 mins for BD1, BD2, and BD3. The isotherm study revealed that Langmuir model is the best fit compared to Freundlich model with highest correlation coefficient and reduced Chi-square (X2) of R2 = 0.97625 and X2 = 0.12142, R2 = 0.96049 and X2 = 0.24403, R2 = 0.85108 and reduced X2 = 1.00914 for BD1, BD2, and BD3 respectively. The kinetic study for the adsorption process indicates that the adsorption of bacteria DNA onto AgNPs obeyed pseudo-second-order with the highest R2 values (ranging from 0.90 to 0.98). Similarly, competing ions (cations and anions) influenced the adsorption capacity in this study. Therefore, this study concludes that AgNPs demonstrated effectiveness in removing bacteria DNA-conveying ARGs from water and will serve as an excellent option to tackle the menace of ARGs in water.