A SIMPLE APPROACH FOR THE ESTIMATION OF THE MASS-TRANSFER COEFFICIENTS AND DIFFUSION-COEFFICIENTS OF VANADIUM IN KUWAIT CRUDE OILS - AN ELUTION STUDY

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.