ESTIMATION OF THE MASS-TRANSFER COEFFICIENTS AND DIFFUSION-COEFFICIENTS OF NICKEL AND VANADIUM IN KUWAIT CRUDE OILS - PREDICTION OF LONG-TERM LEACHING UNDER SIMPLE EXPERIMENTAL CONDITIONS

One of the major concerns following the Iraqi invasion is the possibil ity of ground water contamination caused due to massive oil spillage. Nickel and vanadium are the major metals which exist in trace amounts in crude oils. Leaching of nickel and vanadium was studied on a labora tory scale using 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 rate of leaching was found to be significantly dependent on the type of crude and the pH value o f the leaching medium. The values for the mass transfer coefficient of nickel and vanadium are in the range 0.3-3.18x10(-3) cm3min-1 and 0.0 4-6.4x10(-3) cm3min-1. The diffusion coefficient values for nickel and vanadium are in the range 0.17-22.2x10(-9) cm2day-1 and 0.06-45.4x10( -7) cm2day-1. An overall study of these values suggest that nitric aci d is the most effective leachant for both metals in the four crude oil s. Time for 10% leaching of nickel and vanadium in the oils is estimat ed. A novel feature stemming from this study is the values for the rat e for 10% leaching. The time required for the leaching of 10% nickel a nd vanadium ranged from 2-17.2x10 years and 4-54.6x10 years respective ly. Analysis of variance (ANOVA) of different experimental parameters are presented. The confidence interval for the concentration of nickel and vanadium was estimated. Parameters like the type of acid, pH valu e of the acid and the type of crude was considered. The ANOVA tests in dicated that the leaching ability of the acids varied with the type of crude. The tests showed that there exists a relationship between the initial pH value of the acid and the metal concentration. Better leach ing results were obtained with acids having pH 4.