Sorption of Cyclohexane on Oil Sands Tailings

The use of solvents for extraction of bitumen is attractive because no wet tailings are produced. Studies have already shown that hydrocarbon solvents can achieve the same level of bitumen recovery as the current aqueous extraction method. However, the recovery of solvent must be very efficient to avoid environmental impact and to make the process economic. In order to scale up solvent extraction processes, the adsorption and desorption interactions with mineral surfaces must be quantified. In this study, cyclohexane adsorption and desorption behaviour on clay is characterized by isotherms performed at constant pressure for various temperatures from 20 to 40°C, partial pressures of cyclohexane in nitrogen gas up to 10 kPa, and sample sizes from 50 mg to 2000 mg. These isotherms were classified; the monolayer was calculated, the kinetic behaviour was measured, and the enthalpies of adsorption and desorption were found and compared to the literature value. Only one literature value could be found for comparison.;The isotherm for cyclohexane on clay was classified as a Type II isotherm according to BDDT classification. The BET monolayer coverage varied with temperature. For the range of 20°C to 40°C, the average BET monolayer coverage was calculated to be 0.056 mmol/g for a 50 mg sample. The BET monolayer coverage was calculated to be 0.081 mmol/g for a 2000 mg sample of clay at 30°C, which is comparable to the 0.083 mmol/g monolayer coverage of a sample of pure kaolinite of the same size at the same temperature. Increasing temperature resulted in decreasing adsorbed amount of cyclohexane. There was minimal effect on adsorbed amount when the sample size was changed, as long as it was sampled correctly. The average enthalpy of adsorption and desorption was calculated to be about 40 kJ/mol which is similar to the literature value for cyclohexane on kaolinite. Increasing temperature tended to result in increasing kinetic rate constants while increasing sample size decreased kinetic rate constants. Increasing sample size resulted in decreasing mean kinetic rate constants in general.