Aged oil sludge solubilization using new microemulsion systems: Design of experiments

Microemulsion systems (MES) show valuable properties which allow them to solubilize the bottom sludge of oil storage tanks. In this work, the composition of bottom sludge was determined and MES were developed in order to study their application on the treatment of aged oil sludge using Factorial Design with Central Composite (FDCC). Soxhlet extractions of both crude and aged oil sludges were used to quantify oil (43.9 wt.% and 84.7 wt.% - 13° API), water (38.7 wt.% and 9.15 wt.%), and solid (17.3 wt.% and 6.15 wt.%) contents, respectively. Two pseudoternary diagrams were obtained and, from MES A and MES B, two statistical plans were set by varying the concentration of active matter ([cosurfactant (C) + surfactant (S)]), the C/S ratio, and the concentration of the oil phase ([OP]), with values ranging from 25 to 40 wt.%, 0.5 to 1, and 2 to 5 wt.%, respectively. The FDCC established that the influence of MES constituents in the solubilization of the aged sludge had to be within the microemulsion domain, with predictive and/or significant models showing efficiencies between 77 and 84%, with particular emphasis to MES A.