摘 要
六價鐵是一種具有氧化及混凝多功能的新型水質處理藥劑，可利用濕式氧化法來合成，主要原理乃以強鹼將三價鐵氧化成六價鐵。本研究以廢棄鐵污泥做為原料，進行六價鐵的製備，並評估其對重金屬廢水中之金屬離子之去除效果。首先利用不同的硝酸濃度與鐵污泥進行酸洗，探討較佳之製備條件，接下來在pH5、7、9、未控制pH及不同的加藥量的條件下對人工電鍍廢水進行詴驗，其廢水中含（鉻、鋅、銅、鎳）四種重金屬污染物。評估兩種混凝劑對於實場的有效評估。
實驗結果顯示，在酸洗的過程中濃度0.7M的硝酸可釋出最大量的鐵，在合成中鐵的含量越高所製備的產量越好。對於混沉詴驗的評估，氯化鐵隨pH及加藥量的提升去除效率也增加，但六價鐵只需在高pH的條件下效率達到最佳，六價鐵pH7與pH9去除效率相差不大。在實廠廢水濁度去除方面，六價鐵在低劑量(0.1 mg/L as Fe)下即可達理想的濁度去除效果，而氯化鐵需在較高的加藥量(3 mg/L as Fe)下方能達成。 II
Abstract
A novel and low-cost method in synthesizing ferrate (FeO4-2) from sludge generated from the water treatment plant has been utilized. Ferrate, known as a strong oxidizing and coagulating agent, has been prepared using the wet oxidation method in which Fe(III) salt is oxidized under strong alkaline conditions using hypochlorite as an oxidant. Nitric acid was used to leach out iron from sludge at different concentrations. The maximum amount of Fe(III) was released using 0.7 M HNO3 and was utilized to prepare the ferrate oxidant.
In this study, the ability of ferrate in removing heavy metal ions [Cr(III) , Zn(II), Cu(II), Ni(II)] from aqueous solution has been investigated using the jar test method. The effect of various pH (pH 5, pH 7, and pH 9), and oxidant dosage (0.1 mg/L to 1.0 mg/L) on the removal capacity has been examined. Results revealed that the optimum removal efficiency was achieved at pH 7 while oxidant dosage of 0.1 mg/L. Further increasing in pH value to pH 9 and the oxidant dosage resuleed in significant difference in the removal efficiency.
The feasibility of the synthesized ferrate and ferric chloride as a flocculant has been compared. Optimum turbidity removal was achieved at a low dosage of 0.1 mg/L ferrate as compared to 3.0 mg/L FeCl3.
