title: The effect of inositol hexaphosphate on cadmium sorption to gibbsite.
abstract: OBJECTIVE
  Oxides, hydrous oxides and hydroxides of aluminium and iron are important in determining the availability of trace and heavy metals in soil systems. The presence of complexing anions is also known to affect the binding of these metals in soils. Since organophosphates, such as inositol hexaphosphate (IP6), are present in most soil systems they are expected to affect the nature of the interaction between metal ions and metal (hyr)oxides.
  
  
  METHODS
  Both adsorption edge and isotherm experiments were conducted on Cd(II)-gibbsite and Cd(II)-IP6-gibbsite systems. In addition, solid-state (31)P MAS NMR measurements were performed on the ternary system. All results were used to develop Extended Constant Capacitance surface complexation models of both the Cd(II)-gibbsite and IP6-Cd(II)-gibbsite sorption systems.
  
  
  RESULTS
  The presence of IP6 significantly increased sorption of Cd(II) to gibbsite below pH 8 especially at higher concentrations of Cd(II) and IP6. The (31)P MAS NMR spectra, together with surface complexation modeling, indicated the presence of two outer-sphere ternary complexes with the first, [(SOH2)3(3+)(LHCd)(9-)](6-), important at relatively low concentrations, while the second, [SLH3(8-)Cd(2+)](6-), dominated sorption at higher sorbate concentrations. Thus the presence of organophosphates in soil systems increases sorption and may therefore decrease the availability of trace and heavy metals to plants.
authors.affiliation: La Trobe University, P.O. Box 199, Bendigo, Vic. 3552, Australia.
authors.forename: Maika
authors.initials: M
authors.lastname: Ruyter-Hooley
authors.affiliation: Chemistry of Interfaces, Luleå University of Technology, S-971 87 Luleå, Sweden.
authors.forename: Anna-Carin
authors.initials: AC
authors.lastname: Larsson
authors.affiliation: La Trobe University, P.O. Box 199, Bendigo, Vic. 3552, Australia. Electronic address: B.Johnson@latrobe.edu.au.
authors.forename: Bruce B
authors.initials: BB
authors.lastname: Johnson
authors.affiliation: Chemistry of Interfaces, Luleå University of Technology, S-971 87 Luleå, Sweden.
authors.forename: Oleg N
authors.initials: ON
authors.lastname: Antzutkin
authors.affiliation: La Trobe University, P.O. Box 199, Bendigo, Vic. 3552, Australia.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Angove
keywords: Cadmium; Gibbsite; Inositole hexaphosphate; Solid state (31)P MAS NMR spectroscopy; Sorption; Surface complexation modeling; Ternary complexes