Pollution of soils and sediments by heavy metals is an environmental concern. Among the remedial techniques, soil washing is proving to be reliable. Biosurfactant rhammolipid has shown its potential as a washing agent. In this research, small angle neutron scattering (SANS) was employed to investigate the size and morphology of rhamnolipid aggregates and micelle structure in the presence of heavy metals Cu, Zn, and Ni. The results indicate the importance of the pH of the system in the morphology of the ag regates in the rhamnolipid solution. Creation of a basic condition by addition of 1% NaOH led to the formation of large aggregates (>2000 angstrom) + micelles with R-G similar to 17 angstrom while in the acidic environment with 1% NaCl, large polydisperse vesicles with a radius about 550-600 angstrom were formed. The size of the aggregates in both acidic and C basic condition is fine enough to ease the flow of the rhamnolipid solution through the porous media with the pore sizes as small as 200 nm. (c) 2007 Elsevier Inc. All rights reserved.