Department of Chemical Sciences
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- ItemThe Uptake Potential of Santa Barbara Amorphous Silica/Zeolite Composite for Environmental Microplastics in Wastewater(American Chemical Society, 2024-12) Martins O. OmorogieRecently, the challenge of environmental microplastics (enMPs) in ecosystems has become a serious global concern. This is because the transport of enMPs has been known as a precarious culprit in depleting ecosystems, likely decreasing life expectancy, reducing the quality of human life, and threatening the future survival of fauna and flora. This menace is seriously threatening the continued existence and well-being of all biomes. Hence, this research attempts to provide a panacea to this global environmental issue through the application of Santa Barbara Amorphous silicas/zeolite composite (SSZC) for the removal of polystyrene microplastics (PMPs) from water and wastewater. This research showed that the adsorption capacity of SSZC for PMPs was 2.41 mg·g–1. This was achieved by chemisorption between SSZC and PMPs via electrostatic attraction and hydrophobic interactions, such as covalent bonding, noncovalent aromatic π-system, and electron donor–acceptor interactions. The surface morphology of SSZC showed that C–H, C–O, C═C, N–H, Al–O, Si–O–Si, and Si–OH were the functional moieties present on its surface and available for adsorption.
- ItemThermally-treated MgO/nanocrystalline cellulose immobilized onto a Santa Barbara-16 mesoporous SiO 2 template for the sequestration of antibiotics from polluted water(Royal Society of Chemistry, 2022-10-11) Martins O. OmorogieClean technologies using functional materials as adsorbents for removing antibiotics from polluted water are of great interest, especially for water scarce sub-African countries. In this study, adsorbent MgO/nanocrystalline cellulose immobilized on a Santa-Barbara-16 mesoporous SiO2 template was synthesized at 450 1C, 650 1C and 850 1C (MNCS-450, MNCS-650 and MNCS-850), respectively, and characterized by pH point of zero charge (pHPZC), Fourier transform infrared (FTIR) spectrophotometry, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), energy dispersive analysis of X-ray (EDAX), X-ray diffraction (XRD), and N2 physisorptometry. To evaluate the applicability for the removal of antibiotics, sorption experiments were carried out with two antibiotics representatives, namely ampicillin (AMP) and ciprofloxacin (CIP). The functional moieties, high surface areas (115 to 190 m2 g 1) and pore volumes (0.185 to 0.277 cm3 STP g 1) of the adsorbents were responsible for AMP and CIP removal, probably by hydrogen bonding, hydrophobic and p–p stacking interactions. The experimental data of the sorption experiments best fit the three-parameter Langmuir–Freundlich model (LFM) and the mixed-1,2-order model (MOM), respectively. The maximum LFM monolayer adsorption capacity (qmax LF) was achieved by MNCS-850 for AMP and CIP, which was 4.89 mg g 1 and 4.90 mg g 1 , respectively. Ethanol effectively removed AMP and CIP from MNCS-450, MNCS-650 and MNCS-850 adsorbents. Therefore, the developed adsorbents can be reused and are environmentally friendly.
- ItemDistribution, Correlations, and Risk Evaluation of Endocrine Disrupting Chemicals from Indoor Aerosols within Universities in Nigeria(American Chemical Society, 2024-04-29) Martins O. OmorogieAerosols from filters in air conditioning systems in three indoor environments (staff offices, libraries, and laboratories) across nine universities in Southwest Nigeria were analysed for the presence of endocrine disrupting chemicals (EDCs): methylparaben (MeP), ethylparaben (EtP), propylparaben (PrP), butylparaben (BuP), triclosan (TCS), and bisphenol A (BPA). A total of 102 indoor aerosol samples were collected. The trend for the mean of mean concentrations (𝜇𝜒¯) of MeP (405 ng/g) < EtP (698.8 ng/g) < PrP (4326 ng/g) > BuP (2962 ng/g) < BPA (4316 ng/g) < TCS (4943 ng/g) in staff offices is consistent with those found in libraries (MeP = 452 ng/g; EtP = 1936 ng/g; PrP = 4046 ng/g; BuP = 2584 ng/g; BPA = 2472 ng/g; and TCS = 5109 ng/g). However, the 𝜇𝜒¯ values for EDCs in laboratory aerosols are higher than those found in either staff offices or libraries. Aerosols from indoor environments in universities located in high-population-density areas show higher concentrations of EDCs than in universities established in less populated areas. PrP and TCS were predominant in aerosols from staff offices and libraries, while BuP and TCS were the largest contributors to EDCs in aerosols from the laboratories. PrP is the main contributor to the Hazard Quotients of these EDCs, while PrP and BPA contribute more to the Hazard Index. Data for antimicrobials (parabens and TCS) in aerosols from libraries showed a strong correlation with those from staff offices and laboratories, while for BPA there was a strong correlation between data from libraries and laboratories. The strong correlations between pairs of EDCs in aerosols from different indoor environments suggest that they may have similar accumulation tendencies and the same anthropogenic sources, especially in laboratories. Aerosols in offices of most female staff had higher levels of EDCs compared to those of the male. There is a need to focus on regulating the amount of PrP, TCS, and BPA in pharmaceutical, plastics, and personal care products in Nigeria. This study is the first attempt to report the occurrence and distribution of parabens and TCS in indoor aerosols from the West African sub-region.
- ItemPrevalence and health risk evaluations of mycotoxins in drinking water sources in Nigeria(Royal Society of Chemistry, 2024) Martins O. OmorogieMycotoxins in drinking water are neglected pollutants that have serious health implications when ingested. Common mycotoxins with health concerns include deoxynivalenol (DON), ochratoxin A (OTA), and zearalenone (ZEN). This study considers the distribution and apparent health risks of these mycotoxins in drinking water sources (groundwater, surface water, bottled water, sachet water) in three Southwest Nigeria States: Osun, Oyo, and Lagos States, using the UHPLC-ESI-QTOF. ZEN and DON were found in all 95 water samples across all three states. ZEN in sachet water samples has the highest mean concentrations, with those from Osun, Oyo, and Lagos States having concentrations of 14.96 ± 4.46, 8.59 ± 3.86, and 10.56 ± 2.84 mg L−1, respectively. In contrast, the mean concentrations of all three mycotoxins (± Standard Error of Mean) in bottled water samples are the lowest across the three States. The mean concentrations of OTA in sachet water samples (2.93 ± 0.79, 1.24 ± 0.40, and 3.01 ± 1.50 mg L−1) are slightly higher than those in bottled water (1.47 ± 0.28, 1.53 ± 0.31, and 0.75 ± 0.31 mg L−1) for Osun, Oyo, and Lagos States, respectively. Groundwater samples across the three States had the lowest average pH values, below the WHO's lowest limit of 6.5. Principal Component Analysis studies indicate that all three mycotoxins in water samples are closely associated by source. Possible human exposure values for ZEN suggest some health concerns, especially with the use of sachet water type based on the estrogenicity of this mycotoxin. However, OTA values for all water samples analyzed, are much lower than the tolerable daily intake (TDI) of 4.73 mg kg−1 bw per day provided by European Food Safety Authority (EFSA). The levels of DON in all water sample types were of no serious health concern. However, human exposure levels to all three mycotoxins in bottled water fall within safe limits of health-based guidance values (HBGV) indicating that this drinking water type is better treated, unlike sachet water. Nevertheless, stakeholders need to re-examine water quality with respect to these mycotoxins and adopt stringent guidelines and new water treatment strategies to provide consumers with safe drinking water in line with the UN SDG #6.
- ItemPerovskite oxides: syntheses and perspectives on their application for nitrate reduction(American Chemical Society, 2024-04-23) Martins OmorogieOver the decades, the rise in nitrate levels in the ecosystem has posed a serious threat to the continuous existence of humans, fauna, and flora. The deleterious effects of increasing levels of nitrates in the ecosystem have led to adverse health and environmental implications in the form of methemoglobinemia and eutrophication, respectively. Different pathways/routes for the syntheses of perovskites and their oxides were presented in this review. In recent times, electrocatalytic reduction has emerged as the most utilized technique for the conversion of nitrates into ammonia, an industrial feedstock. According to published papers, the efficiency of various perovskites and their oxides used for the electrocatalytic reduction of nitrate achieved a high Faradaic efficiency of 98%. Furthermore, studies published have shown that there is a need to improve the chemical stability of perovskites and their oxides during scale-up applications, as well as their scalability for industrial applications.