- 學位論文
化學混凝去除水中鉬、銦之研究
Removal of molybdenum and indium from water by chemical coagulation process
摘要
我國環保署於2009年增訂鉬(molybdenum, Mo)、銦(Indium, In)限值皆為0.07 mg/L，但淨水程序去除鉬、銦之研究相當少。本研究探討化學混凝去除鉬、銦，以混凝劑種類(硫酸鋁、多元氯化鋁與氯化鐵)與加藥量、pH及金屬初始濃度為實驗參數。採瓶杯實驗(Jar test)，In(III)採用ICP-MS 分析級(In)，Mo採用AA分析級((NH4)2MoO4)，Mo、In之分析採用ICP-MS感應耦合電漿質譜儀。 研究結果顯示，天然水體 pH 5-9 範圍時，鉬主要以溶解態帶負電MoO42-型態存在，銦則主要為非溶解態不帶電In(OH)3(aq)型態存在。混凝劑去除鉬之效果依序為氯化鐵＞多元氯化鋁＞硫酸鋁，鋁鹽混凝劑去除鉬不佳(低於20%)，鐵鹽混凝劑去除鉬可達75%以上，單位鐵鹽混凝劑Mo之去除量為鋁鹽混凝劑之1.6-3.5倍，建議去除鉬採用鐵鹽混凝劑。鐵鹽混凝劑去除鉬最適pH範圍為4-6，pH於5之單位鐵鹽Mo之去除量為pH於7之約2.8倍。鉬初始濃度愈高單位鐵鹽混凝劑Mo之去除量亦愈高。 銦則主要為非溶解態不帶電In(OH)3(aq)型態存在，混凝去除銦較去除鉬所需混凝劑加藥量低，且三種混凝劑(硫酸鋁、多元氯化鋁與氯化鐵)單位加藥量In去除量約相同，三種混凝劑皆適合用於去除銦。氯化鐵、硫酸鋁及多元氯化鋁混凝去除銦之最適pH分別為pH 7-9、pH 6-8及pH 8-9，於最適pH去除率皆可達90%以上。銦初始濃度愈高單位鐵鹽、鋁鹽混凝劑之In去除量亦愈高。
並列摘要
The Environmental Protection Administration (EPA) Taiwan sets regulated limitation of molybdenum (Mo) and Indium (In) as 0.07 mg/L in 2009. However, researches in removal of Mo and In from drinking water by chemical coagulation process are scarcely reviewed. This study investigated removal of Mo and In by coagulation process. The operational parameters of coagulation are type and dosage of coagulant (ferric chloride, aluminum sulfate and poly aluminum chloride), pH and initial concentration of Mo and In. The results show that in the natural water when pH ranging from 5 to 9, the predominant species of Mo is in dissolved form of MoO42- and In in un-dissolved non-charged form of In(OH)3(aq). The removal efficiency of Mo by different coagulants is following the order of ferric chloride> poly aluminum chloride >aluminum sulfate. The removal efficiency of Mo by aluminum is low (lower than 20%), while removal by ferric chloride could reach more than 75% of efficiency. The amount of Mo been removed by unit mass of ferric is 1.6 to 3.5 times larger than aluminum salt. It is recommended that to use ferric chloride as a coagulant to remove Mo. The optimum pH range to remove Mo by ferric salt is from 4.5 to 6.0. The amount of Mo been removed by unit mass of ferric is 2.8 times larger in pH 5.0 than in pH 7.0. The removal of Mo in unit mass of ferric is higher in higher initial concentration of Mo. The removal efficiency of In by different coagulants is the same. The optimum pH range to remove In by ferric salt and aluminum salt is from 7.0 to 9.0 、 6.0 to 8.0(alum) and 8.0 to 9.0(PACL). The capability of removing In by unit mass of ferric and aluminum are higher in higher initial concentration of In.