Treatment of a Trichloroethylene Source Zone using Persulfate Activated by an Emplaced Nano-Pd-Fe0 Zone

Recently, metal nanoparticles have attracted attention as promising peroxygen activators for the rapid and effective remediation of organic contaminants. In this work, a one-dimensional physical model experiment was designed to investigate the mobility of the metal nanoparticles in porous media and the potential use of metal nanoparticles as peroxygen activators for in situ treatment of source zones. We found that our synthesized nano-Pd-Fe-0 particles were mobile in a non-geological porous medium and relatively immobile in a geological porous medium. In addition, we observed that iron-based bimetallic nanoparticles were able to remain in suspension in an ideal aqueous system much longer (>6 weeks) than iron-based monometallic nanoparticles (<1 h). To overcome the nano-Pd-Fe-0 particle delivery issue in geological porous media, an activation zone approach was adopted. Nano-Pd-Fe-0 particles were injected in order to create a zone to activate persulfate for the treatment of a trichloroethylene source zone. Trichloroethylene mass destruction was only 9 % higher in the nano-Pd-Fe-0 activated persulfate system compared to the non-activated persulfate system as revealed by a short-duration chloride concentration spike in the effluent. In addition, the nano-Pd-Fe-0 activation zone was rapidly deactivated after being exposed to persulfate as visually observed by a color change, indicating that the longevity of the activation zone is limited.