The Effect of Certain Surfactants on the Cementation of Cobalt From Zinc Sulphate Solutions By Suspended Zinc Particles in the Presence of Copper or Antimony

Abstract

The effect of surfactants nonylphenolpolyethylene glycol with molecular weight 900 (D1), dinaphthylmethane-4,4'-disulphonic acid (D2) and polyethylene glycol with molecular weight 400 (D3) on both cobalt-zinc dust cementation kinetics and the structure of obtained deposits was investigated in the presence of copper or antimony. The reaction of cobalt cementation was found not to follow first-order kinetics due to the hydrogen evolution which takes place along with cementation reaction.Two rate regions were observed. Surfactants D1 and D3 inhibit but D2 has no effect on cobalt cementation rate. Copper increases but antimony decreases cobalt deposition. On the other hand, the presence of antimony substantially increases the inhibition effect of D1 and D3 on cobalt cementation. A higher temperature improves cobalt cementation.

D1 and D3 inhibit antimony cementation.The effect of D1 is substantially higher and contributes to a large decrease of antimony deposition by zinc dust.

The influence of copper and antimony on the structure of obtained deposits is strikingly different. The presence of copper causes the deposition of coarser products containing massive formations of lamellar crystallites. The addition of antimony contributes to the formation of compact uniform layers of deposits with a low porosity on the surface of zinc particles. Surfactants D1 and D3 decrease the crystallite size and deposit porosity and their effect is substantially larger in the presence of antimony. The lowest porosity is found in the presence of both D1 and antimony.

According to the obtained results, the concentration of antimony during the cobalt cementation by zinc dust from the solutions containing surfactants D1 and D3 must be lower than that of copper.

On a étudié l'effet d'agents de surface sur la cinétique de cémentation de la poussière de cobaltzinc et sur la structure des dépôts obtenus, en présence de cuivre ou d'antimoine. Les agents étudiés incluent le glycol nonylphénolpolyéthylénique, avec un poids moléculaire de 900 (D1), l'acide dinaphthylméthane-4,4'-disulfonique (D2) et le polyéthylène-glycol, avec un poids moléculaire de 400 (D3). On a trouvé que la réaction de cémentation du cobalt ne suivait pas une cinétique de premier ordre à cause du dégagement d'hydrogène qui se produit en même temps que la réaction de cémentation. On a observé deux régions avec différents taux. Les agents de surface D1 et D3 inhibent le taux de cémentation du cobalt, mais le D2 n'a aucun effet sur celui-ci. Le cuivre augmente la formation de cobalt mais l'antimoine la réduit. D'un autre côté, la présence d'antimoine augmente substantiellement l'effet d'inhibition du D1 et du D3 sur la cémentation du cobalt. Une température plus élevée améliore la cémentation du cobalt.

Le D1 et le D3 inhibent la cémentation de l'antimoine. L'effet du D1 est substantiellement plus élevé, contribuant à une grande diminution de la formation d'antimoine par la poussière de zinc.

L'influence du cuivre et de l'antimoine sur la structure des dépôts obtenus est remarquablement différente. La présence de cuivre entraîne la formation de produits plus grossiers contenant des structures massives de cristallites lamellaires. L'addition d'antimoine contribue à la formation de couches uniformes compactes de dépôts ayant une faible porosité à la surface des particules de zinc. Les agents de surface D1 et D3 diminuent la taille de cristallite et la porosité du dépôt et leur effet est substantiellement plus important en présence d'antimoine. La porosité la plus faible se trouve en présence simultanée du D1 et de l'antimoine.

D'après les résultats obtenus, la concentration de l'antimoine, lors de la cémentation du cobalt par la poussière de zinc à partir de solutions contenant les agents de surface D1 et D3, doit être plus faible que celle de cuivre.     

Kinetics and deposit morphology of copper cementation onto zinc,iron and aluminium

The kinetics of copper cementation onto iron, zinc and aluminium powders at 60 °C and pH=1 have been examined along with the morphology of the deposited copper. The three reductants cemented copper very differently:

• (a)Aluminium gave substantially slower cementation that either iron or zinc and also dissolved significantly less. This passivity of aluminium is due to the oxide layer on its surface;
• (b)The highest cementation rate was obtained using zinc; however, intensive hydrogen evolution on the deposited copper leads to high consumption of zinc;
• (c)Iron was the best substrate for cementation, it deposited copper at ∼70% the rate of zinc but did not react significantly with the acid leading to only one quarter the consumption of zinc;
• (d)The morphology of copper deposits strongly depends on the cementation agent: a coherent layer of fine-grained crystallites less than 1 μm size was obtained on iron, a dendritic deposit with high porosity was obtained on zinc and globular crystallites 1–4 μm in size were obtained on aluminium.

     

EFFECT OF CERTAIN SURFACTANTS ON Co CEMENTATION USING Zn DUST IN THE PRESENCE OF BOTH Cu AND Sb

Abstract

The effect of surfactants nonylphenolpolyethylene glycol (D1), dinaphthylmethane-4,4′- disulphonic acid (D2) and polyethylene glycol with a molecular weight 400 (D3) added separately or as a mixture (D1+D2+D3) on Co-Zn dust cementation kinetics and morphology of obtained deposits was investigated in the presence of both Cu and Sb. The rate constant obtained in the presence of Cu and Sb was 3 to 5 times lower than that found in the presence of Cu and up to 3 times higher than that in the presence of Sb. This indicates a high inhibition effect of Sb on Co cementation. D1, D3 and D1+D2+D3 inhibit Co and Sb cementation. The highest effect was obtained in presence of D1. A decrease in the Sb concentration from 200 to 35 mg dm-3 at a constant Cu concentration increased Co cementation rate by up to 3 times despite the presence of D1+D2+D3. An increase of Sb concentration substantially decreased the crystallite size and deposit porosity.

On a investigué l’effet des agents surfactants nonylphénolpolyéthylène de glycol (D1), acide bisulfonique binaphthylméthane-4,4′ (D2) et glycol polyéthylénique avec poids moléculaire de 400 (D3), ajoutés séparément ou en un mélange (D1+D2+D3), sur la cinétique de cémentation de la poussière de Co-Zn et sur la morphologie des dépôts obtenus, tant en présence de Cu que de Sb. La constante cinétique obtenue en présence de Cu et de Sb était 3 à 5 fois plus basse que celle trouvée en présence de Cu et jusqu’à 3 fois plus élevée que celle en présence de Sb. Ceci indique un effet important d’inhibition du Sb sur la cémentation du Co. D1, D3 et D1+D2+D3 inhibent la cémentation du Co et du Sb. On a obtenu l’effet le plus important en présence de D1. Une diminution de la concentration de Sb de 200 à 35 mg dm-3 à une concentration constante de Cu augmentait le taux de cémentation du Co jusqu’à 3 fois en dépit de la présence de D1+D2+D3. Une augmentation de la concentration de Sb diminuait substantiellement la taille de cristallite et la porosité du dépôt.     

The effect of cyanide and lead ions on the cementation rate,stoichiometry and morphology of silver in cementation from cyanide solutions with zinc powder

The cementation of silver on zinc powder from solutions with a wide concentration range of cyanide has been investigated in the absence and presence of lead ions through stirred reactor batch tests and scanning electron microscopy studies on the cementation product. The concentration of cyanide ions affected the morphology of the product, the nature of cementation reaction and the cementation kinetics. Three cyanide-dependent concentration regimes have been identified: a low cyanide concentration regime in which silver cementation followed an ion-exchange type reaction taking place at the zinc/aqueous solution interface, and the silver deposited around the zinc particle in a uniform growth; a high cyanide concentration regime, as in plant practices, in which the cementation of silver followed an overall chemical reaction involving the evolution of hydrogen and a one-to-one molar silver-to-zinc stoichiometry (In this regime, both the anodic oxidation and the cathodic reduction reactions occurred at distinct interfaces and the silver deposited in a dense-branching morphology.), and an intermediate cyanide concentration regime which is a transition between the two previous regimes. In the low and intermediate regimes, lead and cyanide ions did not affect the morphology of the cemented silver, but increased the silver cementation kinetics owing to Zn(OH)₂ instability. Within the high cyanide concentration regime, lead ions did not appreciably change the cementation kinetics. They modified the pattern of the silver deposit from a dense-branching to a dendritic morphology.     

Kinetics and deposit morphology of gold cemented on magnesium, aluminum, zinc, iron and copper from ammonium thiosulfate-ammonia solutions

The kinetics of gold cementation by magnesium aluminum, zinc, iron and copper at equal conditions as well as the morphology of cementation products and the dissolution of cementing agents were investigated. Both the effect of cementing agents on gold cementation rate and the dissolution of metals decrease in order Cu > Zn > Mg > Fe > Al. High dissolution of magnesium, zinc, iron and copper per mol deposited gold was found. Zinc is the most efficient cementing agent. Magnesium and iron can be used in gold cementation practice but the extremely slow cementation rate prevents the practical application of aluminum.Significant differences in the morphology of gold deposits on magnesium, aluminum, zinc, iron and copper were found: thick deposit layers with small or large cracks were observed on magnesium or zinc; porous layers of fern leaf-shaped dendrites on copper; compact smooth deposit of fine crystallites on iron and small very rare formations of fine dendrites on aluminum.     

EFFECT OF CERTAIN SURFACTANTS ON THE LEACHING AND PRECIPITATION PROCESSES IN ZINC FERRITE RESIDUE TREATMENT

The effect of a surfactant mixture of nonylphenolpolyethylene glycol (D1), dinaphthylmethane-4,4′-disulphonic acid (D2), and polyethylene glycol with molecular weight 400 (D3) on the dissolution of zinc and metal impurities present in zinc ferrite residue in dilute sulfuric acid (160 g L^?1 H₂SO₄) as well as on both jarosite and goethite precipitation was studied at 90°C. The following influences of the surfactant mixture (D1 + D2 + D3), determined by comparing the results obtained in the presence and absence of surfactants, were found. Adsorption of surfactants on zinc ferrite residue surface decreases the dissolution of zinc and metal impurities (Fe, Cu, Cd, As, Sb, and Co). Their extraction efficiencies at the end of the super hot leaching process carried out with surfactants are 4.85–6.29% lower than without them. The formation of a sulfur “sponge” layer on the surface of liquor during the dissolution of ZnS present in zinc ferrite residue is hindered by the surfactants due to their effect as wetting agents and sulfur dispersants. The presence of surfactants reduces the amount of zinc and metal impurities (Fe, Cu, Cd, and As) remaining in the solution after jarosite or goethite precipitation by 5.33–5.86% or 8.03–9.93%, respectively. The volume of jarosite and goethite precipitates increases in the presence of surfactants due to their effect as wetting and flocculation agents. On the other hand, D1 and D3 act as complexing agents. The abovementioned effects of surfactants improve the sorption capacity of both jarosite and goethite, thus ensuring better purification of zinc sulphate solutions, but hindering zinc leaching.     

硫酸锌溶液净化除钴的理论分析和工艺进展

简要评述了硫酸锌溶液净化除钴的工业过程及其进展。理论分析及相应计算表明，锌粉置换钴受扩散控制，此过程的动力学困难是由于在钴上的氢超电压低，而与钴的阴极极化高无关。详细讨论了活化剂对钴置换热力学及氢析出动力学的作用，以及主要工艺参数对净化结果的影响。根据动力学分析、实验室试验及某些工业实践可作出结论：在较低的温度下也可以有效地实现钴置换过程。最后简略介绍了采用ＮａＢＨ４还原除钴的新方法。     

Influence of malonic acid and triethyl-benzylammonium chloride on Zn electrowinning in zinc electrolyte

The influence of malonic acid and other additives has been investigated during the electrowinning of zinc from acid sulphate solutions containing manganese ions. It was found that adding malonic acid “MA” increased the current efficiency and decreased the anodic and cathodic potentials and the cell voltage in the standard electrolyte. Adding malonic acid to the industrial electrolyte containing antimony impurity also led to an increase in the current efficiency. Triethyl-benzylammonium chloride “TEBACl” was the best additive to improve current efficiency with the presence of 5 mg/L Ni²⁺ impurity and it also counteracted the deleterious effect of Sb³⁺ better than the other additives such as polyethylene glycol, sodium lauryl sulphate, perfluoro-heptanoic acid and malonic acid—these were not as good as glue and chloride ion together. Adding 2 mg/L of “TEBACl” to sulphuric acid solution with the presence of nickel ions increased the cathodic potential of hydrogen evolution on the zinc deposit, much more than that of 100 mg/L “MA”.     

The Removal of Cobalt from Zinc Electrolyte by Cementation: A Critical Review

The removal of cobalt from zinc electrolyte has been a focus of electrometallurgical research for over 20 years. This survey reviews the literature on cobalt cementation as well as zinc electrowinning and hydrogen evolution in the interest of characterizing the factors which are important in cobalt cementation by zinc dust and developing an improved purification process. The effect of speciation, the solubility of zinc hydroxide and zinc sulfate, temperature, pH, and the concentrations of reacting species, impurities, and catalytic agents are all investigated.     

Effect of Mn ions on the electrodeposition of zinc from acidic sulphate solutions

The effect of Mn²⁺ ions on current efficiency (CE), deposit morphology and polarization behaviour during electrodeposition of zinc from acidic sulphate solutions was investigated. In the conditions studied, Mn²⁺ ions had no significant effect on CE over the concentration range of 1–10 g dm^− 3. However, a decrease in CE of more than 35% was obtained at 50 g dm^− 3. The cathodic polarization curves and the corresponding kinetics analysis demonstrated that this decrease in CE at higher concentrations of Mn²⁺ ions was due to the strong depolarizing effect of MnO₄⁻ ions and other oxidized products of manganese. Moreover, the kinetics analysis of anodic polarization suggested that the presence of Mn²⁺ ions catalyzed the oxygen evolution reaction. The addition of Mn²⁺ ions was also observed to change the surface morphology and deposit quality of the electrodeposited zinc, affecting the crystallographic orientation by significantly inhibiting the growth of (002) and (100) planes.     

Mechanism of cobalt removal from zinc sulfate solutions in the presence of cadmium

The effect of cadmium and copper, temperature and reaction time on the removal of cobalt from zinc sulfate solutions using zinc dust was experimentally studied. The results show that the rate and extent of cobalt removal are enhanced when cementation takes place in the presence of less than 400 mg/L of cadmium. Cementation residues were analyzed using electron probe micro-analysis (EPMA) to investigate the distribution of phases in the cementation products and the mechanism of cobalt removal. It was found that formation of Zn–Co and Zn–Cd alloys on the zinc dust particles can enhance cobalt removal whereas the presence of Zn–Cu and Cu–Cd alloys can inhibit cobalt removal.     

Copper removal by chelating adsorption in solution purification of hydrometallurgical zinc production

Use of the chelating adsorbent CuWRAM® in the copper removal step of hydrometallurgical zinc process has been studied. This adsorbent contains 2-(aminomethyl)pyridine groups anchored on a polyamine-silica composite and it binds copper and other transition metals by a chelating adsorption mechanism. Equilibrium binding capacity of metal sulfates and sulfuric acid from synthetic and authentic ZnSO₄ process solution was determined at 25-90 °C using batch adsorption measurements. The copper removal efficiency was tested using a laboratory-scale fixed-bed column.Results of the equilibrium measurements show that the selectivity of CuWRAM® is sufficient for feasible separation of copper in the presence of 250-fold zinc excess. Increasing the operation temperature from 25 °C to 60 °C affects only slightly the binding capacity of copper and at the same time decreases the capacity of zinc. In column separation, increasing temperature substantially improves copper removal efficiency from the ZnSO₄ process solution. The improvement is mainly due to enhanced intra-particle mass transport. The positive effect is further amplified by marked decrease in viscosity of the feed solution. The optimum temperature for copper removal appears to be around 60 °C. According to the results of this study, copper can be separated from the authentic ZnSO₄ solution by the chelating adsorbent, while nickel, cobalt and cadmium must be separated by means of conventional methods like cementation with zinc dust. A process scheme is proposed for the solution purification step in the zinc process.     

The behavior of thiourea and flotation reagents in zinc electrowinning circuits

The effect of thiourea and flotation reagents on the electrowinning of zinc from industrial electrolytes was studied, and all the compounds were found to reduce the zinc deposition current efficiency and to change the properties of the zinc deposits. The effectiveness of activated carbon, two-stage cementation, and hot acid leaching on the destruction/removal of the organic compounds also was addressed. Activated carbon pretreatment of thiourea-containing electrolytes restored the current efficiency for 1-hour zinc deposits to values comparable to those obtained for thiourea-free electrolytes. The activated carbon pretreatment, however, altered the deposit morphology and orientation, but produced a cyclic voltammogram similar to that of the thiourea-free solution. Two-stage cementation did not counteract the harmful effects of thiourea. Hot acid leaching destroyed the thiourea but generated large concentrations of ferrous ion that reduced the current efficiency. The ferrous concentrations, however, were readily controlled by KMnO₄ or MnO₂ oxidation. None of the treatment options (activated carbon, two-stage cementation, or hot acid leaching) was effective in controlling the flotation reagents, and their moderately harmful effect on zinc electrowinning persisted. Even low concentrations of these reagents polarized zinc deposition, and this resulted in a “glue-type” zinc deposit.     

The behavior of thiourea and flotation reagents in zinc electrowinning circuits

The effect of thiourea and flotation reagents on the electrowinning of zinc from industrial electrolytes was studied, and all the compounds were found to reduce the zinc deposition current efficiency and to change the properties of the zinc deposits. The effectiveness of activated carbon, two-stage cementation, and hot acid leaching on the destruction/removal of the organic compounds also was addressed. Activated carbon pretreatment of thiourea-containing electrolytes restored the current efficiency for 1-hour zinc deposits to values comparable to those obtained for thiourea-free electrolytes. The activated carbon pretreatment, however, altered the deposit morphology and orientation, but produced a cyclic voltammogram similar to that of the thiourea-free solution. Two-stage cementation did not counteract the harmful effects of thiourea. Hot acid leaching destroyed the thiourea but generated large concentrations of ferrous ion that reduced the current efficiency. The ferrous concentrations, however, were readily controlled by KMnO₄ or MnO₂ oxidation. None of the treatment options (activated carbon, two-stage cementation, or hot acid leaching) was effective in controlling the flotation reagents, and their moderately harmful effect on zinc electrowinning persisted. Even low concentrations of these reagents polarized zinc deposition, and this resulted in a “glue-type” zinc deposit.     

The cementation of uncomplexed silver ions on to zinc and on to ferrous alloys

The kinetics of the cementation of uncomplexed silver ions from low concentration solutions on to zinc and on to ferrous materials have been studied using a rotating disc reactor system. The silver/zinc reaction is mass transfer controlled whereas the deposition on to ferrous precipitants is under mixed control. The effects of changes in temperature, disc rotation speed and solution pH were investigated and the observed behaviour explained in terms of changes in the deposit morphology.     

A Novel Characterization Technique to Determine Pore Susceptibility of Alloying Elements in Aluminum Alloys

An investigation into the effect of ternary alloying element additions such as copper, magnesium, manganese, zinc, and nickel on pore formation in cast Al-12.6-wt pct Si eutectic alloy by employing a novel pore characterization technique is reported here. In this approach, the low-pressure testing method was combined with the metal foam manufacturing technique of intentionally adding TiH₂, which enhances hydrogen pore formation and offers a method to distinguish the effect of individual alloying elements on hydrogen porosity formation.     

Reaction mechanism of cobalt cementation from high cobalt zinc sulphate solution by zinc dust

Abstract

The experiments in this paper were performed to research the mechanism of cobalt cementation from high cobalt zinc sulphate solution by zinc dust. The reduction potential of zinc during cementation was determined to investigate the morphology of products. Residues after the cementation process from zinc sulphate solution were analyzed by SEM and EPMA to investigate the morphology of products. Different temperature will cause different structure of particles. The reaction mechanism of cobalt removal by zinc dust is thought to be as follows: first, the Co2+ forms Co–Zn alloy with zinc particles, and the reaction reaches equilibrium quickly; second, the Co–Zn alloy continues reacting to Co with Co2+, which is the control process of the whole reaction.     

The influence of nickel ions on the long period electrowinning of zinc from sulfate electrolytes

The effects of nickel ions on cathodic current efficiency, electrical power consumption, cell voltage and the surface morphology of deposits during the long period electrowinning of zinc from acid sulfate electrolytes are investigated in this paper. The polarization behavior of the cathode is also examined. The presence of nickel ions in the electrolytes increases the electrical power consumption, decreases the current efficiency, affects the cell voltage and produces the worse surface morphologies. The results of the experiments also show that the zinc electrodeposition process and the cathodic polarization behavior are greatly changed in the presence of nickel ions in the electrolytes.     

Influence of cetyltrimethylammonium bromide and sodium lauryl sulfate on production of zinc powders by alkaline electrowinning

The effects of cetyltrimethylammonium bromide (CTABr) and sodium lauryl sulfate (SLS) on the current efficiency, cell voltage, voltammetric behavior, and deposit character during production of zinc powder by alkaline electrowinning were investigated. Surface morphologies, crystallographic orientations, and grain size distributions of zinc powders were examined by Scanning Electron Microscopy, X-ray Diffraction, and Malvern Laser Particle Size Analyzer, respectively. Maximum current efficiencies of 97.5 and 98.3% were obtained at 1 mg/L CTABr and 10 mg/L SLS, respectively. Voltammetric studies indicated that the surfactants polarized the cathode, which was reflected in powder character. The surfactants dramatically changed the surface morphology and decreased the grain size. Zinc powders with an average grain size of 34.7 μm were obtained in the presence of 10 mg L^?1 CTABr. At 0–10 mg L^?1 CTABr/SLS, zinc powders exhibited an orientation dominated by (101) (002) (100). 1 mg L^?1 SLS hadapositive effect on counteracting the influence of Sb.     

Effects of zinc coatings on the stress corrosion cracking and hydrogen embrittlement of low-alloy steel

The effects of electroplated and hot-dip zinc coatings on the fracture of low-alloy steel AISI 4140 bars tempered to hardnesses in the range Rc 33 to 49 were studied. Either electroplated or hot-dip zinc coatings decrease resistance to stress corrosion cracking,i.e., they reduceK _sc, the threshold stress intensity for stress corrosion cracking in 3.5 wt pct NaCl solution. AboveK _scelectroplated-zinc coatings do not appear to affect the crack-growth rate, although the incubation period prior to the onset of crack growth is reduced. Hot-dip zinc coatings increase stress corrosion crack growth rates slightly because of the additive effect of internal dissolved hydrogen. Hot-dip zinc coatings reduce the critical stress intensity for fracture in the absence of a corrosive environment because of embrittlement by internal hydrogen which is released from traps during hot-dip coating and confined by the inter metallic coatings which form on the steel surface in the hot dip bath. A simple fracture mechanics analysis indicates that either increasing diameter or the presence of a zinc coating lowers the critical hardness at which the stress corrosion cracking of structural bolts can occur.