| Summary: | 碩士 === 明志科技大學 === 環境與資源工程研究所 === 99 === Arsenic compound is one of the commonly found pollutants in groundwater. In this study, one bagasse and two compost samples with different maturity were pyrolyzed at either 400℃ or 800℃ to produce carbon chars. The aim of this study was to evaluate whether the adsorption capacity of sodium arsenite (sodium arsenite) by those carbon chars could be enhanced by adsorbing the different concentrations of ferric ion first. The function content of selected compost samples and carbon chars were analyzed by Bohem titration method. The C, N, H, S, and O of the selected samples were analyzed by element analyzer. The surface area and pore structure were analyzed by specific surface analyzer. The adsorption capacity of ferric ion and arsenite by selected samples were evaluated using inductively coupled plasma atomic emission spectroscopy (ICP-AES). Finally, the distributions of iron and arsenite on the carbon surface were observed by using the scanning electron microscope coupled with energy-dispersive X-ray spectroscopy (SEM-EDX).
The experiment results showed that the more matured compost samples had larger functional group contents and surface area, and thus had greater sorption capacity for ferric and arsenite. After pyrolysis, the functional group contents decreased significantly. Therefore, the 400℃ carbon chars had less sorption capacity for iron when compared with compost samples. However, the surface area of 800℃ carbon chars increased, and thus the sorption capacity of iron and arsenite increased. After 6-month compost sample was pyrolyzed at 800℃ and adsorbed 500ppm ferric iron, the sorption capacity for arsenite increased ten time when compared with raw bagasse sample. The sorption affinity for arsenite increased as the pH increased initially, but decreased after pH reached 9 because hydroxyl iron would compete with arsenite for the binding sites on the carbon surface. The iron did not aggregate on the carbon surface from the SEM-EDX observation, and the sorption capacity for arsenite did not decrease with increasing iron concentration.
Keywords: pyrolysis, compost maturity; ferric iron, arsenic; adsorption
|
|---|
