title: The influence of ferric iron in calcined nano-Mg/Al hydrotalcite on adsorption of Cr (VI) from aqueous solution.
abstract: The influence of ferric iron in calcined nano-Mg/Al hydrotalcite on removal of Cr (VI) from aqueous solution was studied from aspects of structure characteristics, adsorption properties and mechanism discussions. The calcined hydrotalcites (CH-Mg/Al and CH-Mg/Al/Fe) were obtained by thermal decomposition of their corresponding precursors and characterized by XRD, TEM, pH(PZC) and FTIR. The adsorption properties were studied as a function of pH, initial Cr (VI) concentration and contact time. The results showed that the nature of adsorption is endothermic and spontaneous for both CH-Mg/Al and CH-Mg/Al/Fe, but the thermodynamic parameter value changes revealed the addition of Fe(3+) is disadvantage to adsorption process and the theoretical saturated adsorption capacity decreased by approximately 10.2mg/g at tested temperatures. The removal mechanism involved not only intercalation but adsorption on external surface of the layers and interlayer anion exchange for both CH-Mg/Al and CH-Mg/Al/Fe. Furthermore, the results also indicated that intercalation accounts for a large proportion during removal process whatever for CH-Mg/Al, or for CH-Mg/Al/Fe. Additionally, the replacement of Al(3+) by Fe(3+) in CH-Mg/Al led to the interlayer anion exchange more difficult. On the basis of the results, it is concluded that the existence of ferric iron in calcined Mg/Al hydrotalcite is unfavorable to removal of Cr (VI) from aqueous solution.
authors.affiliation: College of Chemistry, Dalian University of Technology, Dalian, Liaoning, PR China.
authors.forename: Lili
authors.initials: L
authors.lastname: Xiao
authors.forename: Wei
authors.initials: W
authors.lastname: Ma
authors.forename: Mei
authors.initials: M
authors.lastname: Han
authors.forename: Zihong
authors.initials: Z
authors.lastname: Cheng
mesh_terms: D000327:Adsorption; D000535:Aluminum / Q000737:chemistry*; D002857:Chromium / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D036103:Nanotechnology; D012996:Solutions; D017550:Spectroscopy, Fourier Transform Infrared; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D005290:Ferric Compounds; D012996:Solutions; D014867:Water; D002857:Chromium; D000535:Aluminum; D008274:Magnesium