title: Removal of molybdate anions from water by adsorption on zeolite-supported magnetite.
abstract: Industrial wastewater may contain high molybdenum concentrations, making treatment before discharge necessary. In this paper, the removal of molybdate anions from water is presented, using clinoptilolite zeolite coated with magnetite nanoparticles. In batch experiments the influence of pH, ionic strength, possible interfering (oxy)anions, temperature and contact time is investigated. Besides determination of kinetic parameters and adsorption isotherms, thermodynamic modeling is performed to get better insight into the adsorption mechanism; molybdenum is assumed to be adsorbed as a FeOMoO2(OH).2H2O inner-sphere complex. At the optimum pH of 3, the adsorption capacity is around 18 mg molybdenum per gram adsorbent. The ionic strength of the solution has no influence on the adsorption capacity. Other anions, added to the molybdenum solution in at least a tenfold excess, only have a minor influence on the adsorption of molybdenum, with the exception of phosphate. Adsorption increases when temperature is increased. It is demonstrated that the adsorbent can be used to remove molybdenum from industrial wastewater streams, and that the limitations set by the World Health Organization (residual concentration of 70 microg/l Mo) can easily be met.
authors.affiliation: University of Leuven, Laboratory of Applied Physical Chemistry and Environmental Technology, Department of Chemical Engineering, K.U. Leuven, W. De Croylaan 46, B-3001 Leuven, Belgium. bram.verbinnen@cit.kuleuven.be
authors.forename: Bram
authors.initials: B
authors.lastname: Verbinnen
authors.forename: Chantal
authors.initials: C
authors.lastname: Block
authors.forename: Dries
authors.initials: D
authors.lastname: Hannes
authors.forename: Patrick
authors.initials: P
authors.lastname: Lievens
authors.forename: Miroslava
authors.initials: M
authors.lastname: Vaclavikova
authors.forename: Katarina
authors.initials: K
authors.lastname: Stefusova
authors.forename: Georgios
authors.initials: G
authors.lastname: Gallios
authors.forename: Carlo
authors.initials: C
authors.lastname: Vandecasteele
mesh_terms: D000327:Adsorption; D052203:Ferrosoferric Oxide / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008982:Molybdenum / Q000737:chemistry / Q000302:isolation & purification*; D009994:Osmolar Concentration; D013816:Thermodynamics; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*; D017641:Zeolites / Q000737:chemistry*
chemical_list: D014874:Water Pollutants, Chemical; D017641:Zeolites; C044659:molybdate; D008982:Molybdenum; D052203:Ferrosoferric Oxide