Palladium(II) chloride complex ions recovery from aqueous solutions using adsorption on activated carbon.

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1 Supporting Information: Palladium(II) chloride complex ions recovery from aqueous solutions using adsorption on activated carbon. arek Wojnicki a,*, Robert P. Socha b, Zbigniew Pędzich c, Krzysztof ech d, Tomasz Tokarski d, Krzysztof Fitzner a. a AGH University of Science and Technology, Faculty of Non-Ferrous etals, 30 ickiewicz Av. 30, Krakow. Poland b Institute of Catalysis and Surface Chemistry Polish Academy of Science, 8 Niezapominajek Str., Krakow, Poland c AGH University of Science and Technology, Faculty of aterials Science and Ceramics, ickiewicza 30 Av., Krakow. Poland d AGH University of Science and Technology, Academic Centre for aterials and Nanotechnology, A. ickiewicza 30 Av., Krakow. Poland * - marekw@agh.edu.pl * Corresponding author., tel , fax: marekw@agh.edu.pl

2 Experimental: Stability constants are given in the table below. Table S Stability constants of chosen Pd(II) complexes Reaction PdCl + HCN Pd( CN) + Cl + H Formation constants β 6 =6 reference PdCl + OH [ PdCl3OH ] + Cl β =6.3 [ PdCl3OH ] + OH [ PdClOH ] + Cl [ PdClOH ] + OH [ PdClOH 3] + Cl β =0.9 β 3 = [ PdClOH 3] + OH [ PdOH ] + Cl β =6.9 To determine the distribution of various complexes, ph dependent stability diagram was calculated. The obtained results are shown in Figure. S..00 [Pd(II)] / mmol kg PdCl - [PdCl 3 OH] - [PdCl OH ] - [PdClOH 3 ] - [PdOH ] Figure. S Distribution of complexes as a function of ph. Chloride ions concentration ph 0. mol kg -. Spectrophotometric determination of Pd(II) molar absorption coefficient.

3 To determine the concentration changes of Pd(II) chloride complexes with time, the spectophotometric method was used in this study. As the reference material for spectrophotometric measurements, the solvents (0. mol kg - HCl) was used. The concentration change can be derived from the recorded absorbance. The UV-Vis spectra of Pd(II) chloride complex ions recorded for different concentrations are shown in Figure S A. It is seen that three absorption peaks are visible for the wavelengths of 33, 79 and 7 nm. The intensity of these peaks is proportional to the concentration of Pd(II) chloride complex ions, the relation is described by Lambert-Beer law. where A absorbance, arbitrary unit ε absorption coefficient, cm mol kg l- optical path length, cm (in our experiment l=cm) A = ε l [PdCl ] () However, to calculate the concentration of Pd(II) complex ions in the solution from the measured absorbance the molar absorption coefficient ε is required. They were found to be 08.±5. cm mol kg, 83.±59. cm mol kg and 338.7±76.8 cm mol kg for the wave lengths 7nm, 79nm and 3nm, respectively. The coefficients were determined at the temperature 98K, in which all analysis were made. Similar work was done with the Pd(II)-Cl-H O complexes complexes obtained by dissolution of Pd(II) in HClO. For seven known concentrations of Pd(II) (see Figure S C) the absorbance at wavelengths 09 and 3nm was determined. Next, the molar absorption coefficients were derived directly from the obtained linear relationship Abs v.s. Pd(II) for the given wavelengths (Figure S D). They were found to be 80±5 cm mol kg, 0.±6. cm mol kg for the wave lengths 09nm, and 3nm, respectively. The coefficients were determined at the temperature 93K, in which all analysis were made. In case of Pd(II) stripping from AC after adsorption, mol kg - of HCl or mol kg - of HClO was used. In case of HClO application, significant changes in UV-VIS spectrum is observed. This is related with the formation of Pd(II)-Cl-H O complexes 3. Recorded UV-Vis spectra for this system are shown in supplementary materials Figure S C Consequently, at first, we determined the molar adsorption coefficient for palladium(ii) chloride complex ions. For five known concentrations of Pd(II) the absorbance at wavelengths 3

4 33, 79 and 7 nm was determined. Next, the molar absorption coefficients were derived directly from the obtained linear relationship Abs v.s. PdCl for the given wavelengths (supplementary materials Figure S B). It should be noted that absorption coefficient in fact depends on temperature. However, all spectrophotometric measurements were performed at temperature of 98K. The applied spectrophotometer is equipped with thermostated measurement cell. Thanks to that it was possible to cool down each sample rapidly just before the measurement, and after that to return the sample to the reactor. 5.0 A) B) Absorbance / A.U C) D).8m.5 639m m m m 0.95m 0.78m.5 T=0 o C 8 l=mm.0 6 Aabsorbance / A.U , nm 3, nm λ / nm λ / nm 7, nm 9.396x0 -,.698x0 -, 9.396x0-5, 9.396x0-6,.698x0-6, Absorbance / A.U. Absorbance / A.U R =0.999 R =0.999 R = ,nm ε=08. cm 79,nm ε=83. 3,nm ε=338.7 T=98 K 0. HCl [Pd(II)] / mol kg nm ε=80 ±5 3nm ε=0. ±6. T=93 K HClO R = [Pd(II)] / mol kg - R =0.998 Figure S A) spectra of palladium(ii) chloride complex ions for five different initial concentration, B) graphical determination of palladium(ii) chloride complex ions molar absorption coefficient at temperature T=98 K, [Cl - ]=0., ph=, C) spectra of palladium(ii) aqua - chloride complexes ions for seven different initial concentrations,

5 D) graphical determination of palladium(ii) chloride complex ions molar absorption coefficient at temperature T=93 K, [Cl - ]=0, ph=0 They were found to be 08.±5. cm mol kg, 83.±59. cm mol kg and 338.7±76.8 cm mol kg for the wave lengths 7nm, 79nm and 3nm, respectively. The coefficients were determined at the temperature 98K, in which all analysis were made. Similar work was done with the Pd(II)-Cl-H O complexes complexes obtained by dissolution of Pd(II) in HClO. For seven known concentrations of Pd(II) (see Figure S C) the absorbance at wavelengths 09 and 3nm was determined. Next, the molar absorption coefficients were derived directly from the obtained linear relationship Abs v.s. Pd(II) for the given wavelengths (Figure S D). They were found to be 80±5 cm mol kg, 0.±6. cm mol kg for the wave lengths 09nm, and 3nm, respectively. The coefficients were determined at the temperature 93K, in which all analysis were made. Langmuir isotherm determination: The Langmuir isotherm can be written as follows: cr Θ = K + c where: K L constant coefficient c r equilibrium concentration of the absorbed substance Θ surface coverage In the typical case, the eq. () is used in the following form: C K C = + C C x x L r L r 0 r 0 0 r () (3) where: x 0 - maximum amount of Pd(II) adsorbed in the case of full coverage by the monolayer. 5

6 .5 T=9 K T=33 K.0 C r /(C 0 -C r ) C r / mol Figure S3 Langmuir isotherm determined for two different temperatures Thermodynamics of adsorption. oreover, assuming, that the adsorption process can be written in the form of a chemical reaction: * K soln PdCl [ PdCl ] [ ] ads () the concentration ratio K [ PdCl ] = (5) * ads [ PdCl ] soln K * can be calculated from our experimental data. In this equation: [ PdCl ] soln is concentration of palladium(ii) chloride complex ions in the solution, after achieving an equilibrium state in the system. [ ] ads PdCl is given by eq. (6). The corresponding amount of Pd(II) adsorbed onto activated carbon can be calculated from the mass balance: [ PdCl ] = [ PdCl ] [PdC l ] (6) ads 0 soln where indexes 0 and soln correspond to the initial and the equilibrium concentrations. The capital letter K * denotes the apparent equilibrium constant. It is observed that an increase of Pd(II) chloride complex ions initial concentration results in a decrease of K*. The influence of initial concentration of Pd(II) chloride complex ions on 6

7 the apparent equilibrium constant is shown in Figure S. However, it can also be seen, that for the concentration above x0-3 mol kg - the apparent equilibrium constant calculated from eq. (5) does not change. Therefore, the K * values for the initial concentration above x0 - should correspond to the equilibrium state between adsorbed species and the solution. Consequently, initial concentration of [PdCl - ] given in main text in Table 3 corresponds to this concentration ratio for which K * is constant. The question is, if the suggested equilibrium () corresponds to the species assumed to take part in the adsorption process. Consequently, the final product of this reaction must be identified T=33 K T=9 K [C] 0 =.67, g/l K * =[PdCl - ]ads / * [PdCl -] solu [PdCl - ] 0 / mol kg- equilibrium ratio Figure S The influence of Pd(II) initial concentration, on the apparent equilibrium constant. References. Hancock, R. D.; Evers, A., Formation constant of tetrakis(cyano)palladate(-). Inorg. Chem. 976, 5, Cruywagen, J. J.; Kriek, R. J., Complexation of palladium(ii) with chloride and hydroxide. Journal of Coordination Chemistry 007, 60, Podborska, A.; Wojnicki,., Spectroscopic and theoretical analysis of Pd + Cl H O system. J. ol. Struct. 07, 8, 7-.. Wojnicki,.; Rudnik, E.; Szablowska,.; Partyka, J., Spectrophotometric analysis of acidic copper(ii) sulfate(vi) solutions. Przem. Chem. 05, 0,

Kinetic modeling of the adsorption process of Pd(II) complex ions onto activated carbon

Reac Kinet Mech Cat (2018) 12:53 68 https://doi.org/10.1007/s111-018-112-2 Kinetic modeling of the adsorption process of Pd(II) complex ions onto activated carbon Marek Wojnicki 1 Krzysztof Fitzner 1 Received: