| 摘要: | 本研究探討電磁場輔助連續分批式奈米級零價鐵反應槽對於去除水中六價鉻離子之效果。研究過程中以化學還原法於實驗室合成奈米級零價鐵粉，並藉由掃描式電子顯微鏡觀測得粒徑介於 50~100 nm間；利用比 表面積分析儀測得其比表面積為 80±5 m2/g。
研究之控制變數包括不同溶液 pH 值(起始 pH = 3、5及持續控制 pH = 3 )、零價鐵與六價鉻質量比( Fe0：Cr6+ = 10：1、20：1及40：1)、六價鉻起始濃度( 20 及 50 mg/L)及不同曝氣氣體等，探討不同操作條件下反應系統對水中六價鉻離子在不同反應時間之總去除量及單位去除量( g-Cr6+/g-Fe2+ )，並且在反應的過程中一併分析溶液中 pH、DO、ORP、亞鐵離子濃度等參數，作為探討六價鉻與零價鐵細部反應作用機制之依據。
研究結果發現，奈米鐵去除水中六價鉻過程中，水中六價鉻起始濃度為 20 mg/L，起始 pH=3，持續以二氧化碳曝氣，分別以不同零價鐵與六價鉻之質量比為 10：1、20：1及 40：1，進行五批次反應後，水中六價鉻五批次總去除率分別達 39.21、63.06及 87.85%，增加質量比有助於六價鉻之去除；於控制六價鉻起始濃度為 20、50 mg/L，質量比 10：1之條件下，經過五批次反應後，兩者於第一批次反應之六價鉻去除率可達 100 %，但第二至五批次六價鉻去除率則隨著批次數增加而下降，顯示於固定質量比條件下，增加六價鉻起始濃度不影響六價鉻之去除率；在控制不同起始 pH=3、5和持續控制 pH=3 之條件下，發現水中六價鉻之去除量，依次為持續控制 pH=3 大於控制起始 pH=3 等於控制起始 pH=5。於不同曝氣條條件下，發現使用二氧化碳和空氣曝氣之水中六價鉻總去除量分別為 31.53及 40.72 mg，顯示空氣曝氣可導致較佳之六價鉻去除率。
In this study, the feasibility of removing chromium (VI) which is a major pollutant from the electroplating wastewater, by nano scale zero valent irons (NZVI) in sequential batch reactors assisted with electric magnetic field was evaluated. Firstly, the nano-scale zero valent irons was prepared through chemical reduction method in the laboratory. It was found that the particle size of nano-scale zero valent iron was in the range of 50 and 100 nm. and the surface area of NZVI was 80 ± 5 m2/g.
This study investigated the effect of solution pH (initial pH 3、pH 5 and constant pH at 3), Fe0：Cr6+ mass ratio ( Fe0：Cr6+ = 10：1、20：1 and 40：1), initial chromium(VI) concentration ( 20 and 50 mg/L), and different kinds of aeration gases on the removal of chromium(VI) and NZVI capability for chromium(VI) removal( g-Cr6+/g-Fe0 ). In the reduction reaction, the solution pH, ORP, DO, Fe2+ ions, total iron, total Cr were also monitored or analyzed.
The results showed that the removals of aqueous chromium (VI) reduced by NZVI using initial Cr6+ concentration at 20 mg/l, initial pH at 3, carbon-dioxide as aeration gas with Fe0：Cr6+ mass ratio from 10：1、20：1 and 40：1 were 39.2, 63.1 and 87.9%, respectively, after 5 batches process. By using Fe0：Cr6+ mass ratio 20：1 at different initial Cr6+ concentration (20, 50 mg/l) in 5 batch runs, the removals of Cr6+ were both 100% in first run. The following run from 2 to 5 resulted in decreasing of removal efficiency.The solution pH plays a important role on the removal of Cr6+. At initial pH 3 and pH 5, the removals of Cr6+ were almost the same ( 74.2 and 73.1% ). However, when solution pH was controlled at constant pH 3 a higher removal of Cr6+ ( 91.9 % )was observed. The removal of Cr6+ using air as aeration gas was found to be 40.7 mg which was larger than that using CO2 as aeration gas ( 31.5 mg ). |
