The containment of oil spills in unconsolidated granular porous media using xanthan/Cr(III) and xanthan/Al(III) gels

Abstract

The gelation in situ of aqueous solutions of the biopolymer xanthan gum may be a method for temporarily containing oil spills in soil whilst the remediation procedure is planned and accomplished. The gelling reaction has been carried out using as crosslinking agents either Cr(III) or Al(III) cations. By using Cr(III) the gelation time, which has been measured for a range of xanthan and/or Cr(III) concentrations, is of the order of the hour. On the contrary, the gelation by means of Al(III) cations takes place at quite low pH and is instantaneous. Therefore, depending on the crosslinker adopted, rather different techniques must be used for generating the gel structure in situ. The gels have proven to be suitable for the containment of water and of many hydrocarbons without loosing their strength even for a long period of time. The rheological properties of xanthan aqueous solutions evidence a shear-thinning behaviour that is most favourable for the application. Theoretical considerations have permitted the establishment of the mobility conditions of xanthan solutions in porous media before the gelation, and the estimation of a suitable injection pressure. The experiments for investigating the mobility of xanthan solutions in porous media, and for simulating the containment of an oil spill, have been done using packed beds of uniformly sized spherical glass beads, in glass columns. The glass assembly made it possible to visualize the evolution of the phenomena of interest.