title: Adsorption kinetics of magnetic biochar derived from peanut hull on removal of Cr (VI) from aqueous solution: Effects of production conditions and particle size.
abstract: Magnetic biochar was made from peanut hull biomass using iron chloride in a simplified aqueous phase approach and pyrolysis at alternative peak temperatures (450-650 °C). Magnetic biochar showed an extreme capacity for adsorption of hexavalent chromium Cr (VI) from aqueous solution, which was 1-2 orders of magnitude higher compared to standard (non-magnetic) biochar from the same feedstock. Adsorption increased with pyrolysis temperature peaking at 77,542 mg kg(-1) in the sample pyrolysed at 650 °C. In contrast to magnetic biochar, the low adsorption capacity of standard biochar decreased with increasing pyrolysis temperature. The fine particle size of magnetic biochar and low aqueous pH were also important for adsorption. Surfaces of products from batch adsorption experiments were characterized by scanning electron microscopy, energy-dispersive X-ray analysis, X-ray diffraction, X-ray photoelectron spectroscopy and vibrating sample magnetometer. This revealed that γ-Fe2O3 was crucial to the properties (adsorbance and magnetism) of magnetic biochar. The removal mechanism was the Cr (VI) electrostatic attracted on protonated -OH on γ-Fe2O3 surface and it could be desorbed by alkaline solution. Findings suggest that pyrolysis has potential to create effective, magnetically recoverable adsorbents relevant to environmental application.
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, PR China.
authors.forename: Yitong
authors.initials: Y
authors.lastname: Han
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, PR China.
authors.forename: Xi
authors.initials: X
authors.lastname: Cao
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, PR China.
authors.forename: Xin
authors.initials: X
authors.lastname: Ouyang
authors.affiliation: UK Biochar Research Centre, School of GeoSciences, University of Edinburgh, The King's Buildings, Edinburgh EH9 3JN, UK.
authors.forename: Saran P
authors.initials: SP
authors.lastname: Sohi
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, PR China. Electronic address: chenjiawei@cugb.edu.cn.
authors.forename: Jiawei
authors.initials: J
authors.lastname: Chen
mesh_terms: D000327:Adsorption; D010367:Arachis; D002606:Charcoal / Q000737:chemistry*; D002857:Chromium / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry; D007700:Kinetics; D060328:Magnetic Phenomena; D009754:Nuts; D010316:Particle Size; D056951:Photoelectron Spectroscopy; D013052:Spectrometry, X-Ray Emission; D013696:Temperature; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D005290:Ferric Compounds; D014874:Water Pollutants, Chemical; C540010:biochar; D002857:Chromium; D002606:Charcoal; C074702:chromium hexavalent ion; C000499:ferric oxide
keywords: Adsorption and desorption; Magnetic biochar; Magnetic properties; Particle size; Pyrolysis temperature