竹炭製備條件對重金屬離子吸附效應

Abstract

本研究選用南投竹山產4年生之桂竹（Phyllostachys makinoi）及孟宗竹（Phyllostachys pubescens）為原料，探討不同炭化及活化製程對竹炭性質及竹炭吸附重金屬離子之效應。竹炭製備採用水蒸氣及二氧化碳活化劑，並針對水蒸氣活化劑之條件，改變水蒸氣注入量為200 ∼ 600 mL/hr及活化時間2 hr和4 hr，在800及900℃進行活化，探討所得竹炭之外觀、收炭率、比表面積、碘值及孔隙性質等。最後依其性質差異，深入研究不同吸附時間及不同竹炭製程、顆粒大小、使用量等對Pb、Cu、Cr、Cd、Ni及As離子之吸附效能。 研究結果顯示，水蒸氣活化之竹炭外觀無光澤、略帶粉粒，且容易折碎，以掃描式電子顯微鏡觀察，以二氧化碳活化之竹炭可得到許多微小孔隙，水蒸氣活化則有矽的析出。以水蒸氣活化之竹炭收炭率較低，並隨著活化劑流量及活化時間、溫度增加而減少。比表面積隨收炭率減少而增加，以水蒸氣活化效果較佳；在增加活化劑流量、活化時間及活化溫度時，竹炭之比表面積性質亦增加，最大可達923.6 m2/g。比較竹炭孔隙性質，以水蒸氣活化可得孔體積較大，而以二氧化碳活化可得到微孔比率較多。 在竹炭吸附重金屬離子方面，隨著吸附時間、竹炭量增加，顆粒尺寸減小，吸附量會增加。使用水蒸氣活化之竹炭吸附效果較二氧化碳活化佳，而未活化之竹炭吸附效果最差，此外，桂竹炭吸附效果較孟宗竹炭佳。比較竹炭對六種金屬離子之吸附效果，以Pb離子吸附效果最佳，Cu、Cr離子次之，而As離子吸附效果最差。

The purpose of the study was to investigate the different carbonized and activated processes of bamboo charcoal in order to realize their properties and the absorbing ability of metal ions. Both four-year makino bamboo (Phyllostachys makinoi）and moso bamboo (Phyllostachys pubescens）planted in the central Taiwan were used in the study. The steam and carbon dioxide were used as activators in the process. The carbonization temperatures, activation time, and the flow rate were carried. The basic properties of bamboo charcoal included the surface properties, charcoal yield, specific surface area, iodine number, and pore characteristics were also investigated. Furthermore, their ability of different metal ion absorption was studied. According to the photos taken by the scanning electron microscope, the charcoal activated by steam was brittle, no brilliance with fine grain, larger pore volume, and the silicon to be separated while that activated by carbon dioxide was smaller micro-pore porosity. The charcoal yield decreased with carbonization temperature and activator flow increasing. The specific surface area increased with charcoal yield decreased, When steam was used as an activator, the charcoal yield was lower than that of carbon dioxide. Their specific surface area increased with steam flow, activation temperature, and activation time increasing. It could reach up to 923.6 m2/g when carbonization temperature at 900℃ and the flow rate was 600 mL/hr. The ability of metal ion absorption increased with absorption time and the amount of bamboo charcoal increasing, and grain size decreasing. Generally, the absorption ability of bamboo charcoal activated by steam was much better than that of the inactivated. In addition, the absorption ability of makino bamboo charcoal was better than that of the moso bamboo charcoal. The lead ion was the easiest to be absorbed of six ions, then followed by the copper and the chromium, and the arsenic was the last.