John Adekunle Oyedele Oyekunle

Speciation study of lead and manganese in roadside dusts from major roads in Ile-Ife, South Western Nigeria

A speciation study of Pb and Mn in roadside dust along major roads in Ile-Ife, South Western Nigeria, was investigated. Pb and Mn values obtained by total digestion ranged from 22.23 ± 3.52 to 43.48 ± 3.05 μg/g and 35.93±0.15 to 83.76 ± 0.06 μg/g, respectively. The results of speciation analysis of Pb and Mn in the samples showed that the mean levels of these metals in the various fractions followed the order: organic matter>residual>Fe-Mn>carbonate>exchangeable and organic matter-bound>exchangeable>carbonate-bound>residual>Fe-Mn oxide-bound respectively. The speciation study therefore revealed that most of the Pb and Mn were associated with the organic matter fraction and that they were least available in the exchangeable and Fe-Mn oxide fractions, respectively. The apparent mobility and potential bioavailability for these metals in the road dust was Mn>Pb. There is a significant difference between the means of Pb and Mn in the road dust of the study area at p≤0.05, which strongly suggests that they may not have come from the same source; different sources may be responsible, which may be anthropogenic, such as tyre wear, vehicular emission, brake linings and natural.

Electrochemical response of nitrite and nitric oxide on graphene oxide nanoparticles doped with Prussian blue (PB) and Fe2O3 nanoparticles

Electrocatalytic behaviour of graphene oxide (GO), iron(III) oxide (Fe2O3) and Prussian blue (PB) nanoparticles and their nanocomposite towards nitrite (NO2−) and nitric oxide (NO) oxidation in neutral and acidic media respectively was investigated on a platinum (Pt) modified electrode. Successful synthesis of these nano materials was confirmed using microscopic and spectroscopic techniques. Successful modification of the electrode was confirmed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results showed that the Pt–GO–Fe2O3 and Pt–GO–PB nanocomposite modified electrodes gave a faster electron transfer process in both a 5 mM Ferri/Ferro ([Fe(CN)6]3−/4−) redox probe and 0.1 M phosphate buffer solution (PBS). The Pt–GO–Fe2O3 and Pt–GO–PB electrodes also gave an enhanced NO2− and NO oxidation current compared with bare Pt and the other electrodes studied. Electrocatalytic oxidation of the analyte occurred through a simple diffusion process but were characterized with some level of adsorption. Tafel slopes b of 468.4, 305.2 mV dec−1 (NO2−, NO); and 311.5, 277.2 mV dec−1 (NO2−, NO) were obtained for the analyte at the Pt–GO–Fe2O3 and Pt–GO–PB electrode respectively. The Pt–GO–Fe2O3 limit of detection and sensitivity in NO2− and NO are 6.60 μM (0.0084 μA μM−1) and 13.04 μM (0.0160 μA μM−1) respectively, while those of the Pt–GO–PB electrode are 16.58 μM (0.0093 μA μM−1) and 16.50 μM (0.0091 μA μM−1). The LoD compared favourably with literature reported values. Pt–GO–Fe2O3 gave a better performance to NO2− and NO electrooxidation, good resistance to electrode fouling, a higher catalytic rate constant and lower limit of detection. The adsorption equilibrium constant β and the standard free energy change ΔG0 due to adsorption are 10.29 × 103 M−1 (−22.89 kJ mol−1) and 3.26 × 103 M−1 (−20.04 kJ mol−1) for nitrite and nitric oxide respectively at the Pt–GO–Fe2O3 electrode. An interference study has also been reported. The fabricated sensors are easy to prepare, cost effective and can be applied for real sample analysis of nitrite and nitric oxide in food, water, biological and environmental samples.

A Comparative Study of the Removal of Heavy Metal Ions from Synthetic Wastewaters Using Different Adsorbents

A comparison has been made of the efficiency of heavy metal ion adsorption from synthetic wastewaters by charcoal prepared locally from the burnt remnants of plantain peel with more conventional adsorbents such as industrial activated wood charcoal, technical charcoal animal powder and Amberlite resin. Thus, mixed standard solutions (100 mg/ℓ) of copper and lead ions adjusted by buffer solutions to pH values of 5, 7 and 9, respectively, were allowed to flow through adsorbent columns which were 10, 20, 30, 40 and 50 cm in length. The concentrations of the heavy metal ions in the mixed standard solutions were determined before and after contact with the adsorbents via atomic absorption spectrophotometry (AAS). The adsorption capacities of the various adsorbents based on the overall percentage removal of Cu2+ ions at pH 9 employing a column of 50 cm length were in the order: Amberlite resin (98.89 ± 7.59%) > plantain peel charcoal (98.56 ± 6.72%) > technical charcoal animal powder (96.87 ± 5.78%) > activated wood charcoal (93.64 ± 7.29%). The corresponding order for Pb2+ ions at a pH value of 7 employing a column of 50 cm length was: Amberlite resin (99.98 ± 7.53%) > plantain peel charcoal (98.37 ± 7.95%) > technical charcoal animal powder (97.91 ± 6.83%) > activated wood charcoal (96.39 ± 7.06%).

Bromate and trace metal levels in bread loaves from outlets within Ile-Ife Metropolis, Southwestern Nigeria

Highlights • This study evaluates the levels of bromate and trace metals in the bread loaves sold within Ile-Ife, Nigeria.• Bromate was determine via spectrophotometric method while trace metals were profiled using Atomic Absorption Spectrophotometer.• Study revealed that many bread bakers had not fully complied with the bromate-free rule stipulated by government contrary to “bromate free” inscribed on the labels of the bread.• The bread samples contained both essential and toxic trace metals to levels that could threaten the health of consumers over prolonged regular consumption.

Speciation study of the heavy metals in commercially available recharge cards coatings in Nigeria and the health implication

This work assessed levels of heavy metals exposure from silver coatings of mobile phones recharge cards of three major companies (designated as A, B and C) with price denominations 100, 200 and 400 from companies A, B and C respectively, which were carefully scratched using a plastic scraper into a glass tube. The coatings were acid digested for total metal concentration, while speciation experiment for Mn, Cu, Cd and Pb was carried out. Total metals and speciation analysis were done using AAS and XRF techniques. The total metal concentration from XRF analysis was in the range: Ca (70–2140 μg/g), K (20–4930 μg/g), Sc (80–270 μg/g), Ti (1530–12,580 μg/g), Fe (50–6660 μg/g), Ni (20–2040 μg/g), Cu (20–850 μg/g) and Zn (40–460 μg/g). Cr had the lowest concentration (10 μg/g) in A ( 400) while Ti had the highest concentration (12,580 μg/g) in C ( 500) for all the coatings analyzed. AAS and XRF results agreed closely except for Fe with higher concentration. A ( 100) contained high concentration of the metals compared with others. Speciation study identified Mn as the most mobile element when present in the environment.

Determination of polycyclic aromatic hydrocarbon levels of groundwater in Ife north local government area of Osun state, Nigeria

This study determined the presence and levels of Polycyclic Aromatic Hydrocarbons (PAHs) of groundwater in Moro, Edun-Abon, Yakoyo and Ipetumodu communities in Ife-North Local Government Area of Osun State. This was with a view to create public awareness about the safety of groundwater as a source for domestic purposes (e.g., drinking, cooking etc.) in non-industrial area. Water samples were collected on seasonal basis, comprising of three months (August–October) in the wet season and three months (December–February) in the dry season. The PAHs in the water samples were extracted with n-hexane using liquid–liquid extraction method, while their qualitative identifications and quantitative estimations were carried out with the use of gas chromatography. Levels of PAHs detected showed predominance of light PAHs (less than four fused rings) for both wet and the dry seasons. Higher concentrations of PAHs were recorded during the wet season than the dry season. The study concluded that the groundwater in the communities was contaminated with light PAHs and the total PAHs in this area exceeded the maximum permissible limit of 10 μg L−1 recommended by World Health Organization (WHO) for safety of groundwater.

Organochlorine pesticide residues in dried cocoa beans obtained from cocoa stores at Ondo and Ile-Ife, Southwestern Nigeria

Graphical abstract

Determination of polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) in some personal care products in Nigeria

Graphical abstract Experimental Procedures for OCPs and PAHs Determination in Personal Care Products

Concentrations of Polybrominated Diphenyl Ethers (PBDEs) in Water from Asunle Stream, Ile-Ife, Nigeria

This study assessed the concentrations of polybrominated diphenylethers (PBDEs) in stream water obtained from Asunle stream, an adjoining stream of the Obafemi Awolowo University dumpsite. Water samples were collected for a period of eight months from six different locations comprising of a spot upstream in an uphill area relative to the refuse dumpsite and five others downstream along the stream course. The sampled waters were extracted with dicholoromethane using liquid-liquid extraction method and cleanup was carried out with silica gel. The final extracts after concentration were analyzed using GC-MS/MS. The recovery experiments were adequate (105%–110%). The mean levels of Ʃ6PBDEs compounds analyzed ranged from 0.03 to 0.45 ng/mL. Seasonal variability of PBDEs indicated that higher levels were found during the wet season. The levels of PBDEs recorded in this work were relatively lower compared to the values reported in the literature from other developed nations.