Isolation and characterization of humic acids from Alberta oil sands and related materials

Thirteen humic acid samples were isolated from a number of oil sand feedstocks using 0.5 N NaOH or a mixture of 0.1 N NaOH + 0.1 M Na₄P₂O₇. The feedstocks included three different grades of Athabasca oil sand, two samples of overburden, a sample of centrifuge tailings from the Syncrude Canada Ltd plant in Alberta and a heavy minerals fraction from oil sand tailings containing adsorbed organic matter. Based on the extraction efficiency of the two solvents it appears that the humic acids from oil sand and overburden feedstocks are strongly associated with calcium, while the humic acids from other feedstocks could be bound to non-silicate aluminum and/or iron. Comparison of analytical data for the various humic acid samples with corresponding data for humic acids from subbituminous coal, peat, soil and asphaltenes from bituminous feedstock, shows the similarity of these humic acids to those from subbituminous coal. Examination of the elemental analyses in terms of a van Krevelen diagram shows that most of the data either overlap or fall directly in the region of the recent and shallow kerogens. This kind of organic matter has very little potential for oil production, suggesting that the origin of this organic matter could be different from that of the greater part of the bitumen of the Athabasca oil sands.