Effect of the Particle Surface on Oil Recovery from Petroleum Sludge

The surface characteristics of solid particles found in two petroleum sludges were studied, along with their effect on oil recovery. The particles were classified into three types based on their microstructures and settling behavior during centrifugation. Wettability of sludge particles and modified quartz was comparatively investigated by the sessile drop method; solids from petroleum sludge were found to have a contact angle close to that of acidified quartz. When the contact angle decreased from 135.1° to 85.8° and 16.9° in unmodified, acidified, and alkylated quartz, respectively, the oil residue following centrifugation increased from 0.9 to 5.2 and 10.0%. Solids found in petroleum sludge are more hydrophobic than solids from oil sand. Pretreatment methods that can decrease the oil–solids interaction, such as anti-alkylation, will improve oil recovery from petroleum sludge.