Mechanistic Investigation of Mercury Sorption by Brazilian Pepper Biochars of Different Pyrolytic Temperatures Based on X-ray Photoelectron Spectroscopy and Flow Calorimetry

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• 作者：Xiaoling Dong ; Lena Q. Ma ; Yingjia Zhu ; Yuncong Li ; Binhe Gu
• 刊名：Environmental Science & Technology
• 出版年：2013
• 出版时间：November 5, 2013
• 年：2013
• 卷：47
• 期：21
• 页码：12156-12164
• 全文大小：413K
• 年卷期：v.47,no.21(November 5, 2013)
• ISSN：1520-5851

文摘

We investigated the mechanisms of Hg sorption onto biochars produced from Brazilian pepper (BP; Schinus terebinthifolius) at 300, 450, and 600 掳C using different analytical techniques. The Hg sorption capacity of BP300, BP450, and BP600 was 24.2, 18.8, and 15.1 mg g^鈥? based on Langmuir isotherm. FTIR data suggested the participation of phenolic hydroxyl and carboxylic groups in Hg sorption by biochars. XPS analysis showed that 23鈥?1% and 77鈥?9% of sorbed Hg was associated with carboxylic and phenolic hydroxyl groups in biochars BP300鈥?50, whereas 91% of sorbed Hg was associated with a graphite-like domain on an aromatic structure in BP600 biochar, which were consistent with flow calorimetry data. Based on flow calorimetry, sorption of K and Ca onto biochar was exchangeable with the molar heat of sorption of 3.1 kJ mol^鈥?. By comparison, Hg sorption was via complexation with functional groups as it was not exchangeable by K or Ca with molar heat of sorption of 鈭?9.7, 鈭?8.3, and 鈭?5.4 kJ mol^鈥? for BP300, BP450, and BP600. Our research suggested that Hg was irreversibly sorbed via complexation with phenolic hydroxyl and carboxylic groups in low temperature biochars (BP300 and BP450) and graphite-like structure in high temperature biochar (BP600).