title: Innovative developments in the selective removal and reuse of heavy metals from wastewaters.
abstract: Sulphide precipitation of heavy metal containing wastewaters results in low effluent concentrations. However, sulphide precipitation is not widely applied in practice because the dosing of sulphide cannot adequately be controlled. A new process was developed where the combination of a sulphide-selective electrode (pS-electrode) and pH electrode controls the sulphide addition. Precipitation experiments were performed on a laboratory-scale in batch and continuous reactor systems with synthetic wastewaters containing Cd, Cu, Ni, Pb or Zn. The response of the pS-electrode during precipitation was unique for each heavy metal and was directly related to the solubility product of the corresponding metal sulphide. The metals were removed to levels < 0.05 mg l(-1) at pH 6.0 by sulphide precipitation while maintaining a total sulphide concentration < 0.02 mg l(-1). By the control of pS at different levels and keeping the pH constant at 6.0, the metals in solutions of both Cu and Zn could be precipitated selectively from solution in a batch and continuous reactors. The use of a membrane reactor in combination with control of pH and pS offers a simple, cheap, efficient and sustainable technique with respect to obtaining very low effluent concentrations and selective removal of metals as pure metal sulphides which can be reused.
authors.affiliation: Sub-department of Environmental Technology, Wageningen University, PO Box 8129, 6700 EV Wageningen, The Netherlands. Adrie.Veeken@algemeen.mt.wau.nl
authors.forename: A H M
authors.initials: AH
authors.lastname: Veeken
authors.forename: W H
authors.initials: WH
authors.lastname: Rulkens
mesh_terms: D011232:Chemical Precipitation; D004566:Electrodes; D006863:Hydrogen-Ion Concentration; D019216:Metals, Heavy / Q000302:isolation & purification*; D013440:Sulfides / Q000737:chemistry; D014865:Waste Disposal, Fluid; D014873:Water Pollutants / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods*
chemical_list: D019216:Metals, Heavy; D013440:Sulfides; D014873:Water Pollutants