Adsorption behavior of petroleum asphaltenes dissolved in Toluene by low-cost mineral adsorbents

This paper presents the feasibility of the removal of asphaltenes from aqueous solutions by using low- cost natural adsorbents such as light expanded clay aggregate (LECA), perlite and bentonite. The structure of adsorbents was characterized by XRD, FTIR, and SEM before and after the adsorption of asphaltenes. The effect of the adsorbent type, initial asphaltene concentration, particle size of the adsorbent and temperature on the adsorption capacity was investigated. The results showed that at the initial asphaltene concentration of 125 mg L-1, contact time of 24 h, temperature of 50°C and adsorbent dosage of 1 g, the removal of asphaltenes onto LECA, perlite and bentonite was 53.59, 93.01 and 99.77%, respectively. Also Langmuir and Freundlich models were applied to describe the experimental data. The results indicated a good fit by Langmuir isotherm. Thermodynamic parameters such as ∆H, ∆S and ∆G were also calculated. It was revealed that the adsorption was spontaneous and of exothermic nature, which was evident by decreasing the randomness of the dye at the solid and liquid interfaces. The characteristic results and dimensionless separation factor (RL) showed that perlite and bentonite can be employed as an alternative to commercial adsorbents for the removal of asphaltenes from the aqueous solution and oil.