TREATMENT OF NITRATES IN THE SUBSURFACE ENVIRONMENT BY NANOSIZED ZERO-VALENT IRON WALL ENHANCED BY ELECTROKINETIC REMEDIATION

摘要

A laboratory-scale treatment system coupled of electrokinetic remediation and permeable reactive barrier (EK/PRB) made of nanosized (50-80 nm) or microsized (75-150 μm) iron was used for evaluating its capacity in removing nitrate from a soil matrix. Experimental results have indicated that the treatment capability of the nanosized iron is much superior to that of microsized one. More specifically, it would need 20 g of microsized iron to obtain a 95.08% of nitrate degradation. However, it needed only 2.5 g of nanosized iron to attain a nitrate degradation of 98.06% for a treatment time of 6 days. Using the present experimental set-up it was found that the most suitable location for PRB installation was 5 cm from the anode reservoir. The treatment efficiency was found to increase as the mass of nanosized iron increased to an optimal one, then began to drop. Experimental results also showed that nitrate degradation increased with increasing electric potential gradient applied. A practice of polarity reversal in the course of EK/PRB processing has been proved to be beneficial to nitrate degradation.