title: Mechanistic investigation of mercury sorption by Brazilian pepper biochars of different pyrolytic temperatures based on X-ray photoelectron spectroscopy and flow calorimetry.
abstract: We investigated the mechanisms of Hg sorption onto biochars produced from Brazilian pepper (BP; Schinus terebinthifolius) at 300, 450, and 600 °C using different analytical techniques. The Hg sorption capacity of BP300, BP450, and BP600 was 24.2, 18.8, and 15.1 mg g(-1) based on Langmuir isotherm. FTIR data suggested the participation of phenolic hydroxyl and carboxylic groups in Hg sorption by biochars. XPS analysis showed that 23-31% and 77-69% of sorbed Hg was associated with carboxylic and phenolic hydroxyl groups in biochars BP300-450, 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(-1). 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 -19.7, -18.3, and -25.4 kJ mol(-1) 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).
authors.affiliation: Soil and Water Science Department, University of Florida , Gainesville, Florida 32611, United States.
authors.forename: Xiaoling
authors.initials: X
authors.lastname: Dong
authors.forename: Lena Q
authors.initials: LQ
authors.lastname: Ma
authors.forename: Yingjia
authors.initials: Y
authors.lastname: Zhu
authors.forename: Yuncong
authors.initials: Y
authors.lastname: Li
authors.forename: Binhe
authors.initials: B
authors.lastname: Gu
mesh_terms: D000327:Adsorption; D027926:Anacardiaceae; D002118:Calcium / Q000737:chemistry; D002151:Calorimetry / Q000379:methods; D002606:Charcoal / Q000737:chemistry*; D004785:Environmental Pollutants / Q000737:chemistry; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008628:Mercury / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning / Q000379:methods; D056951:Photoelectron Spectroscopy; D011188:Potassium / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D004785:Environmental Pollutants; C540010:biochar; D002606:Charcoal; D008628:Mercury; D011188:Potassium; D002118:Calcium