title: Metals Bioaccumulation Mechanism in Neem Bark.
abstract: The aim of this work was to define the bioaccumulation mechanism of metals onto the non-living biomaterial prepared from an extensively available plant bark biomass of neem (Azadirachta indica). Based on maximum ultimate fixation capacities (mmol/g) of the product, metals ions could be arranged as Hg(2+) < Cd(2+) < Pb(2+) ≅ Cu(2+). Surface properties of the biomaterial were characterized by X-ray photoelectron spectroscopy and X-ray diffraction techniques for their sorption mechanism. Whewellite (C2CaO4 · H2O) was identified in the biomaterial, which indicated that calcium ions are electrovalently bonded with carboxylate ions facilitating the ion exchange mechanism with metal ions. Bioaccumulation of metal ions was also studied by Fourier transform infrared spectroscopy, which indicated the presence of functional groups implicated in adsorbing metal ions. Biomaterial did not adsorb anionic As(III), As(V) and Cr(VI), because of their electrostatic repulsion with carboxylic functional groups. Neem bark can be used as bioindicators, bioaccumulators and biomonitors while determining environmental pressures. Metal bioaccumulative properties and structural investigation of plant bark has potential in providing quantitative information on the metal contamination in the surrounding environment.
authors.affiliation: National Institute of Abiotic Stress Management, Baramati, Pune, 413115, India, krishnanik@hotmail.com.
authors.forename: Kishore K
authors.initials: KK
authors.lastname: Krishnani
authors.forename: Veera M
authors.initials: VM
authors.lastname: Boddu
authors.forename: Deok Hyun
authors.initials: DH
authors.lastname: Moon
authors.forename: S V
authors.initials: SV
authors.lastname: Ghadge
authors.forename: Biplab
authors.initials: B
authors.lastname: Sarkar
authors.forename: M P
authors.initials: MP
authors.lastname: Brahmane
authors.forename: K
authors.initials: K
authors.lastname: Choudhary
authors.forename: V
authors.initials: V
authors.lastname: Kathiravan
authors.forename: Xiaoguang
authors.initials: X
authors.lastname: Meng
mesh_terms: D000327:Adsorption; D001151:Arsenic / Q000737:chemistry; D031601:Azadirachta / Q000737:chemistry*; D018533:Biomass; D004784:Environmental Monitoring; D019216:Metals, Heavy / Q000737:chemistry*; D056951:Photoelectron Spectroscopy; D024301:Plant Bark / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D014961:X-Ray Diffraction
chemical_list: D019216:Metals, Heavy; D001151:Arsenic