Ws. Bouhamra et al., A SIMPLE APPROACH FOR THE ESTIMATION OF THE MASS-TRANSFER COEFFICIENTS AND DIFFUSION-COEFFICIENTS OF VANADIUM IN KUWAIT CRUDE OILS - AN ELUTION STUDY, Kuwait journal of science & engineering, 23(2), 1996, pp. 217-231
One of the major concerns following the Iraqi invasion is the possibil
ity of ground water contamination due to massive oil spillage. Nickel
and vanadium are the major metals which exist in trace amounts in crud
e oils. The leaching of vanadium was studied on a laboratory scale usi
ng four different crude oils. Kuwait export (KE), Burgan (B), Ratawi (
R) and Weathered (W). Nitric, sulphuric and acetic acids (pH 4 and 6)
were the leaching medium. The role of a polar medium like de-ionized w
ater was also checked. In the case of an acid medium, the rate of leac
hing was found to be significantly dependent on the type of crude and
the pH value of the leaching medium. The values for the mass transfer
coefficient of vanadium are in the range 0.04-6.4 x 10(-3) cm(3) min(-
1). The diffusion coefficient Values for vanadium are in the range 0.0
6-45.4 x 10(-7) cm(2) day(-1). An overall study of these values sugges
ts that nitric acid is the most effective leachant for vanadium in the
four crude oils. The values for the mass transfer coefficient and dif
fusion coefficient using de-ionized water as the eluent stresses the i
mportance of hydrogen ion concentration in elution studies. Time for 1
0% leaching vanadium in the oils is estimated. A novel feature stemmin
g from this study is the values for the rate for 10% leaching. The tim
e required for the leaching of 10% of vanadium ranged between 4-54.6 x
10 years. An analysis of variance (ANOVA) of different experimental p
arameters is presented. The confidence interval for the concentration
of vanadium was estimated. Parameters such as the type of acid, pH val
ue of the acid and the type of crude were considered. The ANOVA tests
indicated that the leaching ability of the acids Varied with the type
of crude. The tests showed that there exists a relationship between th
e initial pH value of the acid and the metal concentration. Better lea
ching results were obtained with acids having pH 4.