Neutron Activation Analysis of Some Nigerian Bitumen Samples and their Components

Abstract

Bitumen is a mixture of organic liquids that are viscous, black, sticky and soluble in most organic solvents. The composition of bitumen has been variously reported to consist of highly condensed polycyclic aromatic hydrocarbons (PAH), heterocyclic compounds and heavy metals such as nickel, vanadium, lead, chromium, mercury, arsenic, selenium, manganese and other toxic elements 1 ABSTRACTPreliminary examination of the elemental contents of bitumen samples from three deposits in Odigbo Local Government Area of Ondo State, Nigeria and their respective major components (maltene and asphaltene) was undertaken using neutron activation analysis technique. Samples were obtained from tar sand outcrop, near-surface and borehole deposits in Ilubirin and Agbabu mines of the Afowo Formation in the Benin Basin of Southwestern Nigeria. 30 Elements were detected in measurable quantities in these samples with variation in the elemental distribution reflecting the chemical composition of the source. Notable among the elements were Al, Na, K, V, La, Sm, Ni and Pa to mention a few. For instance, 21 elements were detected at measureable concentration in the borehole sample compared with 18 from the tar sand and 20 from near surface bitumen sample. It is noteworthy that the highest concentration level of most elements was encountered in the tar sand sample compared with the other two sources. Maximum concentrations of Al (2624 µg/g), Ti (856.4 µg/g) and V (142.6 µg/g) were recorded for the tar sand sample. Generally, the concentrations of these elements in the samples were significantly different from each other (P≤0.05). The result showed strong positive correlation among the 3 bitumen samples indicating that they are geologically and genetically related. The findings were also complemented with the x-ray diffraction of the sand residue; which was largely characterized by silica (SiO 2 ).