title: One step bioconversion of waste precious metals into Serratia biofilm-immobilized catalyst for Cr(VI) reduction.
abstract: OBJECTIVE
  For reduction of Cr(VI) the Pd-catalyst is excellent but costly. The objectives were to prove the robustness of a Serratia biofilm as a support for biogenic Pd-nanoparticles and to fabricate effective catalyst from precious metal waste.
  
  
  RESULTS
  Nanoparticles (NPs) of palladium were immobilized on polyurethane reticulated foam and polypropylene supports via adhesive biofilm of a Serratia sp. The biofilm adhesion and cohesion strength were unaffected by palladization and catalytic biofilm integrity was also shown by magnetic resonance imaging. Biofilm-Pd and mixed precious metals on biofilm (biofilm-PM) reduced 5 mM Cr(VI) to Cr(III) when immobilized in a flow-through column reactor, at respective flow rates of 9 and 6 ml/h. The lower activity of the latter was attributed to fewer, larger, metal deposits on the bacteria. Activity was lost in each case at pH 7 but was restored by washing with 5 mM citrate solution or by exposure of columns to solution at pH 2, suggesting fouling by Cr(III) hydroxide product at neutral pH.
  
  
  CONCLUSIONS
  A 'one pot' conversion of precious metal waste into new catalyst for waste decontamination was shown in a continuous flow system based on the use of Serratia biofilm to manufacture and support catalytic Pd-nanoparticles.
authors.affiliation: School of Biosciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.
authors.forename: P
authors.initials: P
authors.lastname: Yong
authors.affiliation: School of Chemical Engineering, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.
authors.forename: W
authors.initials: W
authors.lastname: Liu
authors.affiliation: School of Chemical Engineering, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.
authors.forename: Z
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, CB2 3RA, UK.
authors.forename: D
authors.initials: D
authors.lastname: Beauregard
authors.affiliation: School of Mechanical and Chemical Engineering, University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, Australia.
authors.forename: M L
authors.initials: ML
authors.lastname: Johns
authors.affiliation: School of Biosciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK. l.e.macaskie@bham.ac.uk.
authors.forename: L E
authors.initials: LE
authors.lastname: Macaskie
mesh_terms: D018441:Biofilms; D001709:Biotechnology / Q000379:methods*; D018914:Cells, Immobilized / Q000378:metabolism; D002857:Chromium / Q000737:chemistry / Q000378:metabolism*; D053768:Metal Nanoparticles / Q000737:chemistry; D010084:Oxidation-Reduction; D010165:Palladium / Q000737:chemistry; D012705:Serratia / Q000378:metabolism*
chemical_list: D002857:Chromium; C074702:chromium hexavalent ion; D010165:Palladium
keywords: Biofilm; Catalyst; Chromate reduction; Palladium; Precious metals; Serratia sp.