Environmental factors influencing remediation of TNT-contaminated water and soil with nanoscale zero-valent iron particles.

This study evaluated the application of nanoscale metallic particles (nanoscale zero-valent iron (nZVI) particles) in the remediation of TNT in contaminated water and soil samples. The effects of treatment dosages of synthesized nZVI particles and reaction time on degradation rate of TNT were determined. The synthesized nZVI particles (99.99% pure) size distribution was between 20-100 nm (average particle size 80 nm), with a surface area of 21.63 +/- 0.24 m(2)/g. The optimum dosage of nZVI for degradation of 10 mg/L TNT in the contaminated water was 2000 mg/L (w/v) at a reaction time 20 min. However, trace level of TNT remained since the BOD(5) and COD levels at the optimum nZVI treatment dosage were 834 +/- 8 mg/L and 1280 +/- 900 mg/L, respectively. The BOD(5)/COD ratio was 0.65, which was higher than the BOD(5)/COD ratios for the other nZVI dosages which supports the beneficial effect of using nZVI particles for enhancing degradation of TNT. The observed first-order degradation rate of TNT at 25 degrees C was 0.137 min(-1) corresponding to a degradation rate of 0.156 L/m(2) h. In experiments using sandy clay loam soil containing 20 mg/kg TNT in slurry form (1:2 soil to solution ratio, the optimum nZVI treatment dosage that resulted in 99.88% TNT removal was 5000 mg/kg soil. Less toxic intermediate products and their concentrations following degradation were 2-ADNT and 4-ADNT at 0.90 and 0.10 mg/kg, respectively. Results of this study indicate it is feasible to use nZVI for the remediation of TNT-contaminated water and soil samples as a pre-treatment step however secondary treatments such as phyto-remediation or other biological processes may be needed to remove any residue or intermediate products of TNT degradation.