Enhanced Reduction of Perchlorate by Zero-Valent Iron: Effect of Temperature, pH, and Buffering Capacity

다국어 초록 (Multilingual Abstract)

The objective of this study was to enhance the reduction of perchlorate by zero-valent iron (ZVI) to ensure that perchlorate-contaminated water can be significantly treated by employing the iron reduction process. Experiments were designed to accelerate the reduction rate of perchlorate by ZVI by using pH control, alteration of buffering capacity, and elevated temperatures.
Batch experiments with pure iron granules demonstrated that chloride was a reduction product of perchlorate at elevated temperature. It was hypothesized that under pH-controlled conditions,perchlorate may be significantly reduced in an iron-packed column at moderately elevated temperatures (< 100oC), i.e. without the need to increase the temperature more than 100oC. The results showed that approximately 60% of perchlorate could be reduced at 75oC and pH 4.7 with 0.2 M acetate after 120 min. At 99oC and pH 4.7 with 0.6 M acetate, more than 99% of perchlorate could be removed after 490 min. Most hydrogen ions in the buffer solutions were consumed with short retention times (<120 min), indicating that buffering capacity is critical for enhancing the extent and kinetics of perchlorate reduction in iron-packed columns. However, even without buffering capacity,perchlorate could be completely reduced by ZVI at 150oC in 5 hrs.
Our results suggested that a series of iron-packed columns equipped with heating and buffer-control devices are a viable option for treating perchlorate-laden water continuously at moderately high temperatures (< 100oC). A steam-assisted temperature/ pressurecontrolled batch reactor may be another option for treating perchlorate within a temperature range of 150 to 200oC.

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