Zero-valent iron nanoparticles assisted purification of rhamnolipid for oil recovery improvement from oily sludge

Biosurfactant utilization to recover oil from hazardous oily wastes is known as an ecofriendly effective strategy in the petroleum industry. This study aims to promote the reduction of oily sludge viscosity and consequently oil recovery using biosurfactants. For this purpose, the effect of rhamnolipid purification on the oil recovery were investigated. Rhamnolipid was purified using Fe-0 nanoparticles. Purification process was optimized by statistical analysis in which the contact time and nanoparticles amount were chosen to be the independent variables. The measurement of surface tension and critical micelle concentration showed an increase in rhamnolipid purity from 47.61% to 83.33% at optimum conditions. The results of rhamnlipid application for oily sludge treatment showed that the purified biosurfactant decrease the interfacial tension of n-decane/water (1/1) from 27 to 1.2 mN/m while the unpurified rhamnolipid decrease the interfacial tension from 27 to 6.7 mN/m. Also the reduction of oily sludge viscosity by purified biosurfactant is 27.2% more than that by unpurified biosurfactant. Therefore, the novel procedure proposed in this paper is expected to improve the efficiency of oil recovery and have the potential to be employed in oil removal from oily sludge.