title: Chemical fractionation and speciation modelling for optimization of ion-exchange processes to recover palladium from industrial wastewater.
abstract: Palladium is used in several industrial applications and, given its high intrinsic value, intense efforts are made to recover the element. In this hydrometallurgic perspective, ion-exchange (IEX) technologies are principal means. Yet, without incorporating the chemical and physical properties of the Pd present in real, plant-specific conditions, the recovery cannot reach its technical nor economic optimum. This study characterized a relevant Pd-containing waste stream of a mirror manufacturer to provide input for a speciation model, predicting the Pd speciation as a function of pH and chloride concentration. Besides the administered neutral PdCl2 form, both positively and negatively charged [PdCln](2-n) species occur depending on the chloride concentration in solution. Purolite C100 and Relite 2AS IEX resins were selected and applied in combination with other treatment steps to optimize the Pd recovery. A combination of the cation and anion exchange resins was found successful to quantitatively recover Pd. Given the fact that Pd was also primarily associated with particles, laboratory-scale experiments focused on physical removal of the Pd-containing flow were conducted, which showed that particle-bound Pd can already be removed by physical pre-treatment prior to IEX, while the ionic fraction remains fully susceptible to the IEX mechanism.
authors.affiliation: Laboratory of Analytical Chemistry and Applied Ecochemistry, Ghent University, Coupure Links 653, Ghent 9000, Belgium E-mail: Karel.Folens@UGent.be.
authors.forename: K
authors.initials: K
authors.lastname: Folens
authors.affiliation: Laboratory of Water and Ecotechnology, Ghent University, Graaf Karel de Goedelaan 5, Kortrijk 8500, Belgium.
authors.forename: S
authors.initials: S
authors.lastname: Van Hulle
authors.affiliation: Department of Analytical Chemistry, Ghent University, Krijgslaan 281 S12, Ghent 9000, Belgium.
authors.forename: F
authors.initials: F
authors.lastname: Vanhaecke
authors.affiliation: Laboratory of Analytical Chemistry and Applied Ecochemistry, Ghent University, Coupure Links 653, Ghent 9000, Belgium E-mail: Karel.Folens@UGent.be.
authors.forename: G
authors.initials: G
authors.lastname: Du Laing
mesh_terms: D000837:Anion Exchange Resins / Q000737:chemistry; D005591:Chemical Fractionation / Q000379:methods*; D002712:Chlorides; D007220:Industrial Waste / Q000032:analysis*; D007474:Ion Exchange; D007475:Ion Exchange Resins / Q000737:chemistry; D008956:Models, Chemical; D010165:Palladium / Q000737:chemistry*; D012996:Solutions; D062065:Wastewater / Q000737:chemistry*
chemical_list: D000837:Anion Exchange Resins; D002712:Chlorides; D007220:Industrial Waste; D007475:Ion Exchange Resins; D010165:Palladium; D012996:Solutions; D062065:Wastewater; C008756:palladium chloride