Iron nanoparticles based nanofluids for in situ environmental remediation

Abstract

The injection of nanoscale zerovalent iron particles (nZVI) suspensions in the ground is a technology employed for in situ water and soil remediation. Due to its nature, nZVI forming these nanofluids (NFs), tend to agglomerate, but this can be overcome by polyelectrolyte coatings, that also improve their mobility. In this work, stabilization of nZVI with carboxymethylcellulose (CMC) was studied. NFs prepared with CMC (CMC-NSTAR) were compared with non-stabilized NFs (b-NSTAR). First, the stabilization efficiency was evaluated by the analysis of the nanoparticles sedimentation rate. Then, the mobility of stabilized and non-stabilized NFs was studied in columns filled with porous media at laboratory and pilot scale. Finally, NFs reactivity for the removal of aqueous Cr(VI) was tested in batch and columns experiments. In the column experiments, a porous media bed was loaded with NSTAR and then a Cr(VI) solution was injected upwards. CMC-NSTAR showed good mobility at both scales being successfully eluted from the porous media. In the case of b-NSTAR, the accumulation of nanoparticles in the bottom of the column was observed and elution was not achieved. Using b-NSTAR as reactive barrier, a total removal of 15.5 mg Cr(VI)/g Fe was achieved. Better removal rates were found in batch experiments (22.8 mg Cr(VI)/g Fe). Reactivity experiments in batch with CMC-NSTAR showed 39.9 mg Cr(VI)/g Fe removal. In conclusion, the NF was proved to have good transport properties and Cr(VI) removal capacity.