| Summary: | 碩士 === 嘉南藥理科技大學 === 環境工程與科學系暨研究所 === 93 === Traditional ways, such as “chemical precipitation”, ion exchange” and so on, are used for the treatment of chromium (VI) containment wastewater. However, new treatment technologies, such as Zero Valent Iron (ZVI) reduction, is developed in order to replace the traditional methods.
This study focuses on the feasibility of reducing the aqueous chromium (VI) ions by using ZVI. Experiments were designed to investigate the effects of different ZVI dosage, Cr6+/Fe0 ratio, particle size of ZVI (10, 50, 150mm), acid pretreatment of ZVI, initial solution pH (3, 4, 5), initial Cr6+ concentration (9, 20mg/L) on the removal of Cr6+. In the reduction reaction, not only the concentration of aqueous Cr6+ remained in the solution, but also the solution pH, ORP, DO, Fe2+ ions, total iron, total Cr were also monitored and analyzed.
There are several finding regarding the reduction process of Cr6+ using ZVI iron. First of all, when the parameters were set at 9mg/L of Cr6+, 10mm of ZVI particle size, Cr6+/ZVI ratio weight ration 1:120, solution pH was designed as the variable. The solution pHs were controlled in pH 3, pH 4, and pH 5, respectively. Result show that under pH 3, Cr6+ was removed completely in a 12 hours reaction time. Furthermore, when the ratio of Cr6+/ZVI changed from 1:120 to 1:80 to 1:40, removal of Cr6+ was still unchanged for Cr6+/ZVI ration 1:80. As for the weight ratio of 1:40, the removal efficiency dropped significantly to be 23%. Regarding the effect of initial Cr6+ concentration on the Cr6+ removal, it was found the removal efficiency reduced from 100% of initial concentration 9mg/L to 28% of initial concentration 20mg/L in a 12 hours of reaction period. In addition, acid pretreatment of ZVI promoted the Cr6+ removal rate. The reaction time for total removal of Cr6+ reduced from 12 hours to 30 minutes. Base on the experimental data, the best condition for the removal of Cr6+ concluded as following: pH 3, the weight ratio of (Cr6+：Fe0) 1：120 and using 10mm of acid pretreated ZVI. The species of chromium on the surface of ZVI was verified as FeCr2O4 by X-Ray Diffratometer.
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