利用蛇木屑去除水溶液中之鉛離子
Removal of Lead Ions from Aqueous Solution by Using Tree Fern
中文摘要
本研究使用蛇木屑吸附水溶液中之鉛離子，主要內容分為兩個部分，第一部份為 吸附等溫線探討；第二部份為動力學模式探討。吸附劑則選用市售條狀蛇木屑；
吸附質則以硝酸鉛配製不同濃度的鉛離子，以蛇木屑進行吸附實驗。吸附等溫線 探討，包括以理論為基礎衍生出之吸附等溫線 Langmuir isotherm，經驗式等溫線 Freundlich isotherm 及三個變數的等溫線 Redlich-Peterson isotherm。本研究目的 是由等溫吸附研究結果找出較適合描述蛇木屑吸附水溶液中鉛離子之等溫線，並 經由吸附模式參數推估蛇木屑吸附鉛離子的平衡吸附量。在動力學吸附模式方 面，以目前被廣泛利用的吸附模式有 Lagergren 的偽一級動力學模式（pseudo-first order model, PFOM）及 Ho 的偽二級動力學模式（pseudo-second order model, PSOM）等，本研究選擇此兩種模式比較蛇木屑對鉛離子的動力學吸附行為。而 探討等溫線的變項包括：蛇木屑粒徑與反應溫度。針對動力學吸附研究，探討的 影響變數包括：鉛離子初濃度、反應溫度、水溶液 pH 值及蛇木屑的不同劑量等。
研究結果顯示，等溫吸附實驗結果發現，Redlich-Peterson 判定係數為 1.000，
Langmuir 為 0.999，Freundlich 為 0.964，因此，以 Langmuir 及 Redlich-Peterson 為較適合描述之等溫吸附模式。在不同溫度影響下，Redlich-Peterson、Langmuir 及 Freundlich 之判定係數分別大於 0.999、0.998 以及 0.892。而在不同粒徑下，
Redlich-Peterson、Langmuir 及 Freundlich 之判定係數分別大於 0.999、0.999 以及 0.892。由此可知，以 Langmuir 及 Redlich-Peterson 模式較適合描述蛇木屑在等溫 下吸附水中鉛離子之狀況。在所有探討變項中，動力學吸附模式以 Ho 的偽二級 動力學模式較適合描述此吸附系統，判定係數（correlation coefficient）高達 0.994 以上。而在鉛離子初濃度愈高、吸附劑劑量愈大、溫度愈高、pH 值愈高時，其 平衡吸附量愈大。
英文摘要
The study is on sorption of lead(II) from aqueous solutions by using tree fern. This study includes two parts: (1) to analyze the equilibrium sorption based on isotherm models, (2) to analyze the sorption kinetic models. The raw tree fern, which is commercially available, is used as a sorbent; the sorbate is the solutions of lead(II) were prepared using lead nitrate. To investigate the sorption isotherm, three
equilibrium models were analyzed. These included the theoretical Langmuir sorption isotherm, the empirical Freundlich isotherm and the Redlich-Peterson isotherm contains three parameters. The experimental results were fitted to the sorption isotherms which were the best of all isotherms describing tree fern sorbed lead(II)
from aqueous solutions, and according to the evaluation using sorption equilibrium constant, the equilibrium sorption capacities of lead ions onto tree fern. On the kinetic sorption models, the most widely used sorption models were the Lagergren’s
pseudo-first order model and the Ho’s pseudo-second order model. This study
selected two kinds of kinetic models to compare kinetic sorption behavior of tree fern sorbed lead ions. Variables of the sorption isotherm system studied include tree fern particle size and solution temperature. To the kinetic sorption model was analyzed the variables include initial lead concentration, solution temperature, solution pH and sorbent concentration dose.
Experimental results showed that the correlation coefficients are 1.000, 0.999 and 0.964 for the Redlich-Peterson, Langmuir and Freundlich sorption isotherms, respectively. Thus, the results from this study are extremely well described by the Langmuir and Redlich-Peterson isotherm. The variation in temperatures showed that the correlation coefficients are >1.000, >0.999 and >0.964 for the Redlich-Peterson, Langmuir and Freundlich sorption isotherms, respectively. In addition, variables of the particle size also showed that the correlation coefficients are >0.999, >0.999 and
>0.892 for the Redlich-Peterson, Langmuir and Freundlich sorption isotherms, respectively. The results from this study are extremely well described by the Langmuir and Redlich-Peterson isotherm, to analyze three fern sorbed lead ions.
Variable factors of the kinetic sorption models, the results from this study are
extremely well described by the Ho’s pseudo-second order model, which showed that the correlation coefficients are >0.994. Equilibrium sorption capacity increases with increasing initial lead concentration, solution temperature, solution pH and sorbent concentration dose.
