Tokom više od sto godina elektrolitiþka rafinacija predstavlja osnovni proces za
dobijanje bakra þije fiziþko-hemijske osobine zadovoljavaju stroge zahteve za primenu
u elektronici, elektrotehnici, energetici, mikroelektronici. Koncentrisanje primesa kao
što su nikl, arsen, gvožÿe, antimon, dovodi do promene hemijskog sastava elektrolita
kao jednog od osnovnih parametara u procesu dobijanja katodnog bakra. Istovremeno,
usled naglog rasta potražnje kao i smanjenja sadržaja bakra u rudama, sekundarni
materijali se sve više koriste za dobijanje anodnog bakra komercijalnog kvaliteta.
U tekstu disertacije dat je širok prikaz rezultata dobijenih ispitivanjem moguünosti
korišüenja bakarnih anoda nestandardnog hemijskog sastava (poveüani sadržaj Ni, Pb,
Sn i Sb) za elektrolitiþku preradu otpadnih sumporno kiselih rastvora. Ovi rastvori su
nastali u standardnom procesu elektrolitiþke rafinacije bakra i pored visoke
koncentracije bakarnih jona, sadrže i visoke koncentracije jona nikla i arsena.
...Ispitivanja su bila fokusirana na pasivaciono ponašanje anoda, promenu sastava radnog
rastvora, dobijanje anodnog mulja i katodnog taloga. Elementi za pripremu anoda
odabrani su na osnovu podataka iz literature o hemijskom sastavu anoda dobijenih iz
sekundarnih sirovina i njihovom ponašanju tokom elektrolitiþke rafinacije bakra.
Sadržaj Ni u anodama imao je konstantne vrednosti od 5; 7,5 ili 10 % dok se sadržaj Pb,
Sn i Sb kretao u opsegu 0,1-1 % po elementu, a za pripremu anoda korišüene su razliþite
kombinacije ovih elemenata.
Elektrohemijska merenja koja su izvedena na opremi laboratorijskog tipa, primenom
metode anodne linearne promene potencijala (ALPP), korišüena su za preliminarna
ispitivanja rastvorljivosti anoda u kiselom rastvoru. Na svim voltamogramima
dobijenim snimanjem razliþitih uzoraka anodnog materijala registrovani su pikovi
pasivacije ali se vrednosti potencijala i gustine struje pasivacije razlikuju. Poreÿenjem
rezultata za serije anoda sa istim sadržajem nikla (5; 7,5 ili 10% Ni), utvrÿeno je da
anode sa veüim sadržajem neþistoüa (Pb+Sn+Sb %) u pasivnu oblast ulaze pri nižim
vrednostima gustine struje rastvaranja. Gustine struje rastvaranja bakarnih anoda
nestandardnog hemijskog sastava, koje se kreüu i do 360 mA/cm2
, veüe su od gustine
struje rastvaranja anodnog bakra komercijalnog kvaliteta (220 mA/cm2
). Rezultati su
potvrdili da je bakarne anode sa poveüanim sadržajem Ni, Pb, Sn i Sb moguüe rafinisati
u galvanostatskim uslovima pri vrednostima gustine struje rastvaranja koje odgovaraju
komercijalnom procesu elektrolitiþke rafinacije bakra.
Ispitivanja elektrolitiþke prerade otpadnog sumporno kiselog rastvora sa poveüanim
sadržajem Cu, Ni i As, pri gustini struje þija je vrednost u granicama komercijalnih
vrednosti, izvedena su na opremi uveüanog laboratorijskog tipa. Dobijeni rezultati
predstavljaju realnu osnovu za nastavak istraživanja u industrijskim uslovima.
Rafinacija bakarnih anoda raÿena je u uslovima konstantnog galvanostatskog pulsa (25
mA/cm2
), na dve razliþite temperature radnog rastvora (T1=63±2 oC i T2=73±2 oC) u
trajanju od 72 h, masa svake anode bila je oko 7 kg. Na osnovu promene napona na
üeliji, koja je merena i beležena na svakih 10 s u trajanju od 72 h, utvrÿeno je da su se
sve anode rastvarale tokom procesa. Promena napona na üeliji odvijala se u nekoliko
karakteristiþnih faza. Rezultati su pokazali da se ni jedna anoda nije trajno pasivirala.
Kod odreÿenog broja anoda došlo je do pojave pasivacije u trajanju od nekoliko minuta
do maksimalno 40 min, ali nakon ovog vremena anode su se reaktivirale i nastavile da
rastvaraju. Pojava stabilne i oscilatorne faze registrovana je kod svih anoda. Analizom
podataka za pojavu pasivacije anode, utvrÿeno je da se pasivacija þešþe javlja kod anoda
sa nižim vrednostima sadržaja Ni. Kod anoda sa 5 % Ni pojava pika pasivacije
zabeležena je kod 75 % ispitanih anoda, a kod anoda sa 10 % Ni pik pasivacije je
registrovan kod 12,5 % od ukupnog broja anoda.
Analizom rezultata za koncentracije jona Cu i Ni u rastvoru utvrÿeno je da se sadržaj Cu
smanjuje, a sadržaj Ni raste. Koncentracija Cu jona maksimalno je smanjena na oko 3 %
a koncentracija jona Ni poveüana za 150 % u odnosnu na polazne vrednosti.
Smanjenjem koncentracije bakarnih jona pokazano je da uporedo sa procesom
elektrolitiþke rafinacije anoda dolazi i do elektroekstrakcije bakra iz radnog rastvora što
se potvrÿuje i podacima za masu katodnog taloga koja je za sve rafinisane anode veüa
od mase bakra rastvorenog iz anode. Kod veüeg broja anoda, masa katodnog taloga je
veüa i od teorijske vrednosti mase Cu koja se može istaložiti pri radnoj gustini struje.
Temperatura rastvora nema direktan uticaj na promenu sastava elektrolita. Rezultati
ispitivanja promene koncentracije jona arsena u rastvoru pokazuju da se koncentracija
tokom procesa smanjuje. Smanjenje od približno 95% postignuto je rafinacijom anode
sa 7,5% Ni i približno 2,5 % Pb+Sn+Sb. Koncentracija jona kalaja na kraju svakog
eksperimenta bila je veüa od polazne vrednosti. Tokom prva 24 h, promena
koncentracije bila je najveüa, a u nastavku procesa, vrednosti promene koncentracije
varirale su od anode do anode. Promena koncentracije antimona u prva 24 h imala je
trend porasta u odnosu na polaznu vrednost. Koncentracija antimona se menjala do
kraja eksperimenta ali nije utvrÿena nikakva pravilna zavisnost.
Analizom hemijskog sastava anodnog mulja, pored prisustva Pb i Sn, potvrÿeno je i
prisustvo Sb, As, Ni i Cu. Na osnovu podataka o masi anodnog mulja i masi rastvorenih
anoda, utvrÿeno je da se rastvaranjem anoda sa veüim ukupnim sadržajem Pb, Sn i Sb
na nižoj temperaturi, dobija veüi procenat anodnog mulja. Maksimalna vrednost od
12,67% dobijena je rafinacijom anode sa 7,5 % Ni i 2,07% Pb+Sn+Sb, a minimalna
vrednost od 0,58 % dobijena je rafinacijom anode sa 10 % Ni i 0,305 % Pb+Sn+Sb.
Fiziþki izgled i masa katodnog taloga potvrdili su da se tokom tretmana sumpornokiselih
rastvora odvijaju dva procesa i to: elektolitiþka rafinacija bakarnih anoda i
elektroekstrakcija bakra iz radnog rastvora. Smanjenjem koncentracije bakarnih jona i
poveüanjem koncentracije niklovih jona u radnom rastvoru stvoreni su uslovi za
izdvajanje nikla odgovarajuüim metodama.
Dobijeni rezultati su pokazali da se elektrolitiþkom rafinacijom bakarnih anoda sa
poveüanim sadržajem Ni, Pb, Sn i Sb smanjuje koncentracija bakarnih i arsenovih jona
a poveüava koncentracija niklovih jona u tretiranom rastvoru. Deo neþistoüa prevodi se
u anodni mulj, a bakar iz anode i rastvora taloži na katodnoj osnovi. Ispitanim
procesom, za tretman otpadnog rastvora iz komercijalnog procesa elektrolize bakra
korišüene su bakarne anode dobijene iz sekundarnih materijala na bazi bakra, þime je
potvrÿena i ekološka opravdanost procesa.
For more than a century, electrolytic refining is the main process for obtaining copper
whose physical and chemical properties meet strict requirements for application in
electronics, electrical engineering, energy, microelectronics. The accumulation of
impurities such as nickel, arsenic, iron, antimony, leads to changes in the chemical
composition of the electrolyte as one of the basic parameters in the process of copper
cathodes obtaining. At the same time, due to a sudden increase in demand and reduction
of copper content in the ores, secondary materials are increasingly being used to
commercial copper anode production.
The text of this dissertation gives a broad overview of the results obtained by examining
the possibility of using the copper anodes of non-standard chemical composition (high
contents of Ni, Pb, Sn and Sb) for electrolytic treatment of the waste sulfur-acid
solutions. These solutions are obtained during the commercial electrolytic copper
refining process. As well as... the high concentration of Cu ions, these solutions contain
high concentrations of Ni and As ions. The tests were focused on the anode passivation
behavior, changes in the chemical composition of the solution, obtaining cathode
deposit and anode slime. Components for the anodes preparing were selected on the
basis of literature data for the chemical composition of the anodes obtained from the
raw materials and the behavior of impurities in the copper refining process. Nickel
content in the anodes had a constant value of 5, 7.5 or 10 mass %, whereas the content
of Pb, Sn and Sb was ranged from 0.1 to 1 mass% per item. Different combinations of
these values were used for anodes preparation.
Electrochemical measurements that were performed on laboratory type equipment,
applying the method of anodic linear sweep voltammetry (ALSV), were used for
preliminary investigations of anodes dissolution in acidic solution. The passivation
peaks are registered on all voltammograms obtained by recording the various anode
samples. But, the values of the potential and current density were different. Comparing
the results for series of anodes with the same nickel content (5, 7.5 or 10 mass % Ni), it
was found that anodes with a higher content of impurities (Pb+Sn+Sb mass %) in the
passive area inputs at lower current density. Current density for dissolution the copper
anodes of non-standard chemical composition, which range up to 360 mA/cm2
, is the
higher than the current density for dissolution the commercial copper anodes (220
mA/cm2
). The results confirmed that the copper anodes with high content of Ni, Pb, Sn
and Sb could be refine in galvanostatic conditions at current density which value is
characteristic of commercial process. Investigations of the electrolytic treatment of the
waste sulfur acid solution with high content of Cu, Ni and As, at current density whose
value is within commercial value, were carried out on the large scale equipment. The
results represent a reasonable basis for continued research in industrial conditions.
Refining of copper anodes was performed with constant galvanostatic pulse (25
mA/cm2
), at two different temperatures of the working solution (T1 = 63 ± 2 °C and T2
= 73 ± 2 °C) during the 72 h, the weight of each anode was about 7 kg. Based on the
change of cell voltage value, which is measured and recorded by every 10 s for 72 h, it
was found that all the anodes are dissolved during the process. Changing the cell
voltage was carried out in several characteristic phases. The results showed that none of
the anodes is not permanent passivation. In a number of the anodes, the passivation is
appeared for a few minutes to a maximum of 40 minutes, but the anodes were
reactivated after this time and continue to dissolve. The appearance of a stable and
oscillatory phase was registered during the rafination of all anodes. By analysis the
occurrence of anode passivation, it was found that the passivation is more common in
the anodes with the lower values of Ni content. At the anodes with 5 mass % Ni, the
peak of passivation phenomenon was observed in 75 % of the all anodes, and in the
anodes of the 10 mass % Ni, passivation phenomenon was registered in 12.5 % of the
total number of anodes.
The analysis of the concentration of Cu and Ni ions in solution showed that the Cu ions
concentration decreases and the Ni concentration increases. Maximum concentration of
Cu ions is reduced to about 3 % and the concentration of Ni ions maximized to 150 %
of the respective baseline values. The decreasing of copper ions concentration was
confirmed that along with the process of electrolytic refining of anodes occurs the
electroextraction of copper from working solution. That is confirmed by the data for the
cathode deposits mass, which for all anodes and both temperatures is the higher than
mass of copper that dissolve from the anodes. For a number of anodes, cathode mass of
deposit is greater than the theoretical values of the Cu mass that can precipitate at
working current density. The different temperatures of the solution have no influence on
the composition of the electrolyte. The investigation of the changes the arsenic ions
concentrations have shown that the concentration was decreased compared to baseline
value. The biggest concentration changing (about 95 %) was registered during the
refining of anode with 7.5 % Ni and 2.5 mass % Pb+Sn+Sb. The concentration of tin
ions at the end of each experiment was greater than the baseline. During the first 24 h
concentration changing was the highest, and in the continuation of the process the
concentration changing varied from anode to anode. Changing the concentration of
antimony in the first 24 h had an upward trend compared to the baseline value. The
concentration of antimony is changed up to the end of the tests but there were no proper
dependency.
The analysis of the anode slime chemical composition were confirmed that the next
elements are present in the slime: Pb, Sn, Sb, As, Ni and Cu. Based on the data of the
anode slime mass and the weight of dissolved anodes, it was found that the percentage
of anode slime is higher for the anodes with a higher content of Pb+Sn+Sb, at lower
temperature. The maximum value of 12.67 % is obtained by refining the anode with 7.5
mass % Ni and 2.07 mass % Pb+Sn+Sb, and the minimum value of 0.58 % is obtained
by refining the anode with 10 mass % Ni and 0.305 mass % Pb+Sn+Sb .
The physical appearance and weight of cathode deposits have confirmed that during the
treatment of sulfur-acid, two processes are conducted: electrorefining of copper anodes
and copper electroextraction from the working solution. Reducing the concentration of
copper ions and increasing the concentration of nickel ions in solution were created the
conditions for the extraction of nickel using appropriate methods.
The results showed that the electrolytic refining of copper anodes with increased Ni, Pb,
Sn and Sb reduces the concentration of copper and arsenic ions and increases the
concentration of nickel ions in the treated solution. Part of impurities translates into the
anode slime, and the copper from anodes and from solution deposited on the cathodes.
The tested process, treatment of waste solutions from the commercial copper
electrolysis using the copper anodes obtained from the secondary copper-based
materials, thereby providing and environmental justification.
