Metal leaching from fluid petroleum coke under different geochemical conditions

Please join us for our first Grad Student seminar of the year presented by Mojtaba Abdolahnezhad, MSc candidate:

Metal leaching from fluid petroleum coke under different geochemical conditions

In 2017, the upgrading processes of bitumen to synthetic crude oil within the Athabasca Oil Sands Region (AOSR) of northern Alberta resulted in 10.1 M tonnes of petroleum coke and 60 M m3 synthetic crude oil. Results of bulk elemental analysis from this project revealed elevated concentrations of V (1372± 37 mg kg-1), Ni (540 ±10 mg kg-1), Mo (75±3 mg kg-1), and other metals were found to be present in fluid petroleum coke. Fluid coke leachate with the elevated metal concentration in the AOSR and the associated increase in toxicity is a potential risk to water quality and aquatic organisms. A variety of studies has investigated the geochemical and toxicological aspect of coke deposits and their leachate (i.e., V, Ni, Mo); however, the geochemical conditions controlling the leaching and mobility of these metals is lacking and requires further examination. This project examined leaching and transport of trace element from fluid petroleum coke (i.e., fresh and slurry coke) under different geochemical conditions (i.e., DI, Oil Sand Processing-Water, and Acid Rock Drainage) in lab scale. These geochemical conditions were selected based on their prevalence as discovered by previous field studies. Pore-water samples were collected during the experiment and analyzed for dissolved trace elements. The measured cumulative mass released for metals indicate that Ni release was higher under ARD, while Mo cumulative mass released was found to be higher under OSPW solution (at neutral to alkaline pH condition and it is due to desorption of Mo). For V, it was found to be leached under both ARD and OSPW solutions. Also measured cumulative mass released for metals showed noticeable higher metals leaching for slurry coke in comparison with dry coke. Since mine closure landscapes within AOSR employ overburden, mine wastes, and upgrading by-products, including petroleum coke, these studies can help minimize the potential impacts of released metals on water quality.