炭化材之基本性質及其竹活性碳對重金屬離子吸附效能之探討

Basic Properties of Bamboo Charcoals and Adsorption acities of Heavy Metal Ions by Bamboo Activated Carbons

羅盛峰(Sheng-Fong Lo)

指導教授 ： 王松永

國立臺灣大學/生物資源暨農學院/森林環境暨資源學研究所/博士(2008年)

https://doi.org/10.6342/NTU.2008.01773

摘要

本研究探討孟宗竹及麻竹在昇溫速率1℃/min∼20℃/min，導入500 mL/min氮氣，最高炭化溫度400℃至1600℃（間隔以200℃），持溫1 hr等缺氧條件之炭化材的基本性質，並探討活化溫度為800℃，活化劑以水蒸氣400 mL/hr注入1 hr，所得之竹活性碳，對Pb（Ⅱ）、Cu（Ⅱ）及Cr（Ⅲ）及Cd（Ⅱ）等四種金屬離子水溶液之吸附效能與移除效率，結果歸納如下：
炭化材收炭率會隨著炭化溫度增大而降低，在800℃以上時之收炭率降低漸趨緩和，至1600℃時則減為25.68~27.68％。而其碳元素（C）含量則各為98.38％（孟宗竹炭）與96.48％（麻竹炭）。另竹炭之視密度會隨著炭化溫度升高而增大，與竹炭之收炭率呈相反之趨勢；視密度在1200℃時，孟宗竹炭可達到2.154~2.468 g/cm3而麻竹炭為2.147~2.322 g/cm3，但炭化溫度升至1600℃時，孟宗竹炭反而降低為1.347~1.416 g/cm3，麻竹炭為1.359~1.397 g/cm3。
孟宗竹與麻竹經高溫炭化後，炭化材之收縮率（縱向、弦向與徑向）及體積收縮率均會隨著炭化溫度增高而增大，在400℃∼800℃炭化溫度範圍會急速增大，但800℃∼1200℃炭化溫度範圍則其增加趨勢緩和，且有弦向>徑向>縱向的趨勢。炭化材之電阻係數（ρ, logρ）均會隨炭化溫度增加而減低，當炭化溫度達800℃時，其ρ值各會減低至10Ω•cm又ρ與logρ值均會隨著C元素含量（％）與C/H比值增加而下降，並且以徑向之ρ值大於縱向與弦向。
炭化材之調濕性能（％），炭化溫度1000℃時，孟宗竹炭為3∼3.5％，會顯著大於其他炭化溫度者，而麻竹炭則在600∼800℃者會達到6.31-6.42％較大，1000℃時反而會降低。以吸濕速度曲線A＝A0（1-e-kt）關係式表示時，其A0值均兩種竹炭均以1000℃炭化溫度者較大，孟宗竹炭為134.89-167.75 mg/g，麻竹炭為154.07-172.67 mg/g，但k值則與炭化溫度，昇溫速率間無一定趨勢。
就孟宗竹與麻竹竹炭之微細構造觀察，兩種竹材炭化後仍可維持竹材原有之導管，薄壁組織，與纖維組織之架構，但隨炭化溫度之增高，當炭化溫度達1200∼1600℃時，可看到導管腔內，薄壁細胞壁上附有各種不同形狀之結晶，而其成分主要為矽（Si）。
孟宗竹與麻竹活性碳對於Pb（Ⅱ）、Cu（Ⅱ）及Cr（Ⅲ）及Cd（Ⅱ）等四種金屬離子水溶液之吸附效能最適的攪拌時間各為2-8 hr與1 hr，而孟宗竹活性碳對重金屬離子吸附效能依序為Pb（Ⅱ）> Cu（Ⅱ）> Cr（Ⅲ）> Cd（Ⅱ），而麻竹活性碳則為Pb（Ⅱ）> Cd（Ⅱ）> Cu（Ⅱ）> Cr（Ⅲ） 。對重金屬離子之最大移除效率所需活性碳量各為Pb（Ⅱ）：孟宗竹活性碳0.1-0.3 g；100％，麻竹活性碳0.1 g；100％。、Cu（Ⅱ）：孟宗竹活性碳0.5 g；100％，麻竹活性碳0.1-0.3 g；100％。Cr（Ⅲ）：孟宗竹活性碳0.5 g；53.1％（S1C1group），100％（S2C1group）；麻竹活性碳0.3 g；100％。Cd（Ⅱ）：孟宗竹活性碳0.5 g；43.9-65.8％，麻竹活性碳0.5 g；100％。

關鍵字

炭化 ； 活化 ； 視密度 ； 電阻係數 ； 重金屬離子 ； 吸附效能 ； 移除效率

並列摘要

The purpose of this research was to investigate different carbonization and activation processes of bamboo charcoals made from moso bamboo（Phyllostachys pubesens） and ma bamboo（Dendrocalamus latiflorus）in order to realize the basic properities, adsorption capacity, and removal effiency of heavy metal ions (Pb（Ⅱ）, Cu（Ⅱ）, Cr（Ⅲ）, Cd（Ⅱ）). The bamboo charcoals were carbonized at final temperatures ranging from 400℃ to 1600℃ and temperature with increasing rate from 1℃/min to 20℃/min. Nitrogen at normal atmospheric pressure was induced into carbonizing chamber in all cases. Carbon was activated at 800℃ for one hour and steam as activator induced 400 mL per hour. Results were summarized as follows:
The yields of moso bamboo carbonized at final temperatures ranging from 200℃ to 1600℃ were different. When material was heated to 200ºC, the yields were 98.74% to 99.15％. The charcoal yields decreased sharply between 200℃and 600℃, and yield appeared to steady within 24.18~28.76％ at 1200℃. At 1600℃, yields were 25.68~27.68％. It showed that the yields of two bamboo charcoal decreased with the increasing of the final temperatures. It also showed that carbon content of two bamboo charcoals increased with the final temperature increasing while hydrogen and oxygen content decreased. Carbon content of moso bamboo and ma bamboo carbonized at the final temperature of 1600℃ was 98.38% and 96.48%, respectively. Comparing the yields of two bamboos carbonized at three different temperature increasing rates of 1℃/min, 3℃/min, and 5℃/min, it showed there was no significant difference of charcoal yield among those. However, it showed significant difference of lower temperature increasing rate from higher ones of 10℃/min and 20℃/min. The apparent density of moso bamboo and ma bamboo carbonized at the final temperature of 1200℃ were 2.154~ 2.468 (g/cm3) and 2.147~2.322 (g/cm3), respectively. At 1600℃, apparent density decreased apparently to 1.347~1.416 (g/cm3) of moso bamboo charcoal and 1.359~1.397 (g/cm3) of ma bamboo charcoal, respectively.
The shrinkage of longitudinal, tangential, and radial directions and volume of two bamboo charcoals increased with the final carbonization temperature rapidly between 400℃ and 800℃. It showed steady between 800℃ to 1200℃ and the largest shrinkage was occurred in tangential direction, on the other the axial direction was the least one. The electrical resistivity (ρ) of these two kinds of bamboo charcoals decreased with the increasing of the carbonized temperature. When the carbonized temperature increased to 800℃ and 1000℃, the ρ values decreased to 10Ω•cm and 10-1Ω•cm∼10-2Ω•cm, respectively.
Bamboo charcoals showed larger values of conditioning hygroscopic capacity (effective adsorption capacity, %) at carbonization temperature of 1000℃ for moso bamboo charcoal, and carbonization temperature of 600℃∼800℃ for ma bamboo charcoal. When the adsorption rate of curve expressed by the formula of A＝A0(1-e-kt), coefficients of A0 and k were the adsorption weight and adsorption rate until equilibrium condition, respectively. The larger A0 showed at carbonization temperature of 1000℃ for moso bamboo and ma-bamboo charcoals. However, ma bamboo charcoal was slightly larger than that of moso bamboo charcoal. Coefficient of k was showed no significant difference among various carbonized temperatures, and temperature increasing rates.
Moso and ma bamboo charcoals could maintained their original structure of vessel, parenchyma and fiber tissues after carbonization treatment, when the carbonized temperature increased to 1,200∼1,600℃. It was found that the various shape of crystals in the vessel lumen and parenchyma walls. The crystals in spined-shape, granular-shape, and flake-bar-shape were found in moso-bamboo charcoals, and the circular-shape, rectangular-shape, multilayer-block-shape was found in ma bamboo charcoals. The main component of crystals was silica (Si).
The optimal agitation times of activated moso bamboo carbon and ma bamboo carbon to remove heavy metal ions from aqueous solution were 2-8 hours and 1 hour, respectively. The adsorption capacity of activated moso bamboo carbon removal 4 heavy metal ions as follow: Pb（Ⅱ）> Cu（Ⅱ）> Cr（Ⅲ）> Cd（Ⅱ）while activated ma bamboo carbon was Pb（Ⅱ）> Cd（Ⅱ）> Cu（Ⅱ）> Cr（Ⅲ）. The maximum weight to remove heavy metal ions from aqueous solution of activated moso-bamboo carbon and removal efficiency were 0.1~0.3 g (Pb（Ⅱ）: 100%)), 0.5 g (Cu（Ⅱ）：100％), 0.5 g (Cr（Ⅲ）：53.1％ (S1C1group) ;100％ (S2C1group）), 0.5 g (Cd（Ⅱ）：43.9-65.8％). And the maximum weight to remove heavy metal ions of activated moso-bamboo carbon and removal efficiency were 0.1 g (Pb（Ⅱ）: 100%), 0.1-0.3 g (Cu（Ⅱ）：100％), 0.3 g (Cr（Ⅲ）：100％), 0.5 g (Cd（Ⅱ）：100％).

並列關鍵字

Charcoalization ； Activation ； Apparent density ； Electrical resistivity ； Heavy metal ions ； Adsorption capacity ； Removal efficiency

參考文獻

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