Remediation of diesel oil contaminated sand by micro-emulsion

Abstract

Abstract Micro-emulsion has unique advantages in repairing diesel oil contaminated sand due to its low interfacial tension and strong solubility. By Winsor phase diagram, it was found that with the increase of salinity, the phase of micro-emulsion transformed from Winsor I to Winsor III to Winsor II. Under cryogenic electron microscope, it was observed that Winsor I was O/W type, Winsor II was W/O type, and Winsor III type was bi-continuous type. The effect of inorganic salts, alcohol and temperature on the oil removal rate of diesel oil contaminated sand was investigated by static recovery of micro-emulsion precursor. The results showed that for the anionic micro-emulsion system, with the increase of salinity and alcohols, the oil yield of the upper phase increased first and then decreased, and the two components had a certain compensation effect. For non-ionic micro-emulsion system, with the increase of temperature, the oil yield in the upper phase rose first and then decreased. At the same time, the influence of leaching conditions on oil removal rate was investigated by one-dimensional sand column leaching experiment. It was found that for diesel oil contaminated sand with 15% oil content, when the formulation was 2.00 wt% SDBS, 4.05 wt% n-butanol and 0.40 wt% sodium chloride, the optimum leaching conditions were leaching rate of 4 ml·min−1 and leaching amount of 400 ml. Under such conditions, the oil removal rate was up to 82.84%, that is, the oil content of the sand was reduced to 2.57%. Moreover, the micro-emulsion has good cyclicity, and it can still achieve high oil yield after six cycles.