Isolation and Sorption Behavior of Humic Acid from Zhongdian Peat of Yunnan Province, China

The Zhongdian swamp meadow in Zhongdian, China is well known as ＂Shangri-la＂, where the peat has never been studied for its potential to interact with pollutants. Humic acid （HA） was extracted from Zhongdian peat using two methods, namely sodium pyrophosphate extraction （SPE） and dilute base extraction （DBE）, and characterized for its functional groups and sorption property. The HAs extracted by both methods contained several active functional groups and had large external specific surface areas. The adsorption mechanism of methylene blue onto HAs was interpreted as Langmuir sorption. SPE-HA showed higher sorption capacity because of its larger specific surface area, whereas the extraction yield of DBE-HA was twice that of SPE-HA. Kinetics modeling indicated that the sorption of methylene blue was a two-component first order reaction. The component with the higher rate constant also showed higher sorption capacity. No pH effect was observed for methylene blue sorption on HA in our experimental design, and the sorption decreased as the temperature increased.