Remediation of pyrene-contaminated soil by synthesized nanoscale zero-valent iron particles

Laboratory experiments were conducted to assess pyrene removal from soil using synthesized nanoscale zero-valent iron (nZVI) particles. Batch experiments indicated that nZVI particles were more efficient in removing pyrene than commercially available microscale ZVI (mZVI, < 10 microm) particles. Reaction kinetics of pyrene removal were dominated by the iron dosage and approximated by a pseudo-first-order model. The reaction rate constants (k) were 0.135 +/- 0.030 and 0.103 +/- 0.023 min(-1) when 0.01 g nZVI and mZVI particles were amended to batch vessels containing one gram of pyrene-spiked soil (100 mg pyrene per kg dried soil), respectively. The pH and oxidation-reduction potential (ORP) did not change significantly in experiments with mZVI particles. In experiments with nZVI particles, however, pH slowly increased from 4.8 to 8.5 due to hydroxide production, and ORP rapidly decreased from +400 to -550 mV. ORP continued to decline to -700 mV when additional nZVI particles were added. The results from this study indicate that nZVI particle addition produced strongly reducing conditions and suggest that remediation of pyrene-contaminated soils using nZVI particles is a promising technology.