零價鐵批次瓶杯去除水中重金屬

Heavy Metal Removal from Water by Zero-Valent Iron

蔡淑清(Shu-Ching Tsai)

指導教授 ： 羅煌木

朝陽科技大學/理工學院/環境工程與管理系/碩士(2012年)

摘要

本研究主要探討零價鐵批次瓶杯實驗於不同影響因子如 : 重金屬濃度、零價鐵添加量、pH值、溫度和攪拌速度下，對重金屬污染物之處理效率，並進一步以最佳化操作條件探討零價鐵對於不同重金屬 ( Cr、Cd、Ni、Cu、Zn、Pb、As、Hg ) 污染物之處理效率。並將實驗所得之數據代入一階及二階動力方程式作動力學探討，可獲得零價鐵對八種重金屬去除效率之有用資訊。
研究結果顯示，當(1)零價鐵添加量分別為 0.1、0.3及0.5 g/L，於反應終點時，其去除率分別為 37、89 及 91%。(2)零價鐵於鹼性環境 (pH 11 ) 下，其反應終點時，Cr 污染物去除率為 20% ，略高於中性 pH 7 之14% ，而在酸性環境 ( pH 3 及 pH 5 ) 下，其反應終點時，Cr 污染物去除率分別為87 及 19%，其pH 3之去除率遠高於中性 pH 7 之14%。(3) 零價鐵於不同溫度 (10、25及40℃) 下，其反應終點時，Cr 污染物去除率分別為16、16 及 37%。 (4) 零價鐵於不同轉速 ( 50、150及 350 rpm ) 下，其於反應終點時，Cr 污染物去除率分別為 32、37 及 47%。(5)於酸性pH 3、高溫45℃條件下，零價鐵對八種不同重金屬之去除效率由高至低依序為 As > Cr > Cu > Hg > Pb > Zn > Cd > Ni。於反應終點時，其去除率分別為 97、92、72、56、38、9、7 及 2%。 (6) 動力學研究結果顯示八種重金屬與零價鐵顆粒二階動力反應，其迴歸值R2比一階動力反應來得高，故反應較遵循二階反應動力學方程。

關鍵字：零價鐵、重金屬、去除率、一階反應動力學、二階反應動力學

關鍵字

二階反應動力學 ； 一階反應動力學 ； 零價鐵 ； 重金屬 ； 去除率

並列摘要

The purpose of the study is to explore waste treatment efficiency of zero-valent iron on eight major heavy metals (Cr, Cd, Ni, Cu, Zn, Pb, As, and Hg). Experiment of batch jar tests explores responsive kinetics of heavy metal removal under different influential factors. Operation conditions include thickness, pH values, stirring speed, temperature and addition of zero-valent iron of waste. Best operation conditions are found with preceding environment factors to conduct ensuing heavy metal jar test with best operation parameters to explore removal efficiency of zero-valent iron on metal waste. Data after experiments will be included into first order and second order kinetics equations to discuss kinetics in attempt to build database of ability of zero-valent iron in removing waste.
Study results show: (1) operation conditions: (i) each gram of zero-valent iron has limited activator address for reaction. Once content of zero-valent iron is increased or waste thickness is decreased, removal rate goes up. (ii) although zero-valent iron reduces activator address to participate in reaction in high pH value environment, the generated hydroxide or salt residue enhances precipitation. Removal rate in high pH value is slightly higher than that under pH 7. In lower pH values, the coating by ferric hydroxide and zero-valent iron formed by ferric ion and hydroxide ion makes zero-valent iron in full contact with waste and tend to remove waste in acid environment. (iii) Response rate of zero-valent iron in reduction increase with rise of temperature. When control temperature is increased, removal rate goes up. (iv) Reduction of zero-valent iron is affected by mass transfer. Thus, higher stirring speed enhances response speed and removal rate. (2) Comparison among eight major heavy metals: under acid and high temperature, removal efficiency of zero-valent iron ranked from top to bottom: As > Cr > Cu > Hg > Pb > Zn > Cd > Ni. At the end of reaction, the removal rate is 97%, 92%, 72%, 56%, 38%, 9%, 7% and 2%. Removal rate over 50% after 60 minutes includes As, Cr, Cu and Hg. (3) kinetics: study results show eight major heavy metal and zero-valent iron particle reaction are pseudo- second order kinetics reaction; the regression line R2 is higher than pseudo-first order kinetics reaction. Thus, the reaction conforms to pseudo-second order kinetics equation.

Keywords: zero-valent iron, heavy metal, removal efficiency, first-order reaction kinetics, second-order reaction kinetics

並列關鍵字

removal efficiency ； first-order reaction kinetics ； zero-valent iron ； heavy metal ； second-order reaction kinetics

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