Selektive Adsorption von Nickel(II)- und Cobalt(II)-Ionen aus sauren Prozesslösungen
Publication date
2024
Document type
PhD thesis (dissertation)
Author
Kriese, Friederike Karolin
Advisor
Niemeyer, Bernd
Referee
Granting institution
Helmut-Schmidt-Universität / Universität der Bundeswehr Hamburg
Exam date
2024-03-25
Organisational unit
Part of the university bibliography
✅
Files openHSU_15321.pdf (4.08 MB)
Dissertation Friederike Karolin Kriese
DDC Class
600 Technik
Keyword
Adsorption
Nickel
Cobalt
Abstract
The demand for raw materials such as nickel, cobalt and lithium has risen due to the grow¬ing demand for batteries. In order to meet this high demand, the use of efficient recycling processes is becoming important. Adsorption as a basic process engineering operation is an efficient separation process, since e.g. a high selectivity can be set.
In this work, a functionalized silica-based adsorbent for the selective separation of nickel(II) cations in the presence of cobalt(II) cations was identified and characterized with the aim of using it in battery recycling or in the electroplating of components with gold. On the one hand, it was challenging to find selectively binding ligands, as the two target substances have similar physical-chemical properties. On the other hand, acidic pH values and in¬creased temperatures are unfavorable process conditions for adsorptive bonding.
In the course of the screening process for the adsorbent, it was identified that despite the initial acidic pH value, the pH value was shifted to the basic environment during adsorption by some of the functionalized adsorbents, so that separation took place by metal hydroxide precipi¬tation instead of adsorption. This was not considered in previous studies in the literature. The control of the pH value in the equilibrium state in discontinuous adsorption experiments was therefore established as the first screening criterion.
The adsorbent HSU331, finally favored for the application, enabled the separation of nickel(II) and cobalt(II) by chelate complexation under the given process conditions. The complex nickel(II)/HSU331 always produced higher equilibrium constants in direct compari¬son to cobalt(II)/HSU331. Thus, the energetic effect was exploited as a selectivity mech¬anism. Consequently, high integral selectivities for nickel(II) up to S_(Nickel(II)/L,L) = 0.98 could be quantified. A requirement for the occurrence of selectivity was that the total initial ad¬sorptive amount corresponded approximately to the amount of substance of the binding sites present. The selectivity with respect to nickel(II) (up to S_(Nickel(II)/L,L) = 0.97) remained comparable when the model system nickel(II)/cobalt(II) was extended by lithium(I) or a gold electrolyte solution. Kinetical investigations showed that the equilibrium loadings were reached after 5 to 10 min, so that short residence times can be set for a later con¬tinuous operation of the adsorption. Desorption tests confirmed the difference in equilibrium state between nickel(II)/HSU331 and cobalt(II)/HSU331. Cobalt(II) was already completely desorbed by a diluted nitric acid solution with pH = 1.0, whereas nickel(II) was only desorbed at pH = 0.5.
In this work, a functionalized silica-based adsorbent for the selective separation of nickel(II) cations in the presence of cobalt(II) cations was identified and characterized with the aim of using it in battery recycling or in the electroplating of components with gold. On the one hand, it was challenging to find selectively binding ligands, as the two target substances have similar physical-chemical properties. On the other hand, acidic pH values and in¬creased temperatures are unfavorable process conditions for adsorptive bonding.
In the course of the screening process for the adsorbent, it was identified that despite the initial acidic pH value, the pH value was shifted to the basic environment during adsorption by some of the functionalized adsorbents, so that separation took place by metal hydroxide precipi¬tation instead of adsorption. This was not considered in previous studies in the literature. The control of the pH value in the equilibrium state in discontinuous adsorption experiments was therefore established as the first screening criterion.
The adsorbent HSU331, finally favored for the application, enabled the separation of nickel(II) and cobalt(II) by chelate complexation under the given process conditions. The complex nickel(II)/HSU331 always produced higher equilibrium constants in direct compari¬son to cobalt(II)/HSU331. Thus, the energetic effect was exploited as a selectivity mech¬anism. Consequently, high integral selectivities for nickel(II) up to S_(Nickel(II)/L,L) = 0.98 could be quantified. A requirement for the occurrence of selectivity was that the total initial ad¬sorptive amount corresponded approximately to the amount of substance of the binding sites present. The selectivity with respect to nickel(II) (up to S_(Nickel(II)/L,L) = 0.97) remained comparable when the model system nickel(II)/cobalt(II) was extended by lithium(I) or a gold electrolyte solution. Kinetical investigations showed that the equilibrium loadings were reached after 5 to 10 min, so that short residence times can be set for a later con¬tinuous operation of the adsorption. Desorption tests confirmed the difference in equilibrium state between nickel(II)/HSU331 and cobalt(II)/HSU331. Cobalt(II) was already completely desorbed by a diluted nitric acid solution with pH = 1.0, whereas nickel(II) was only desorbed at pH = 0.5.
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