由氧化锌烟灰氨法制取高纯锌

开发了用NH3-NH4Cl水溶液浸出炼铅炉渣烟化炉氧化锌烟灰制取高纯锌的新工艺.Zn的浸出率＞96%,浸出液加H2O2后净化除Sb和As,然后采用加锌粉两段逆流除Cu,Cd,Pb,电积过程中电能消耗2 500～2 700 kW@h/t.电锌含Zn＞99.999%,杂质元素Cu,Cd,Co,Ni,Fe,As,Sb均小于0.0001%,Pb＜0.000 3%.     

A study on zinc electrodeposition onto zinc cathode

Abstract

The electrodeposition of zinc onto a zinc cathode was studied through the comparison between theoretical and experimental polarisation curves. The former was constructed using the Butler–Volmer equation with electrochemical parameters, such as Tafel slope values, exchange current densities, equilibrium potential values, etc. The latter was obtained from data derived in a chloride based electrolyte of 0·6 mol dm^?3 Zn²⁺ ions with boric acid (25 g dm^?3), pH = 5. The electrochemical parameters such as exchange current density, limiting current density, equilibrium potential, Tafel slopes, can be obtained with good agreement with the values from the literature.     

Influence of concentration of zinc ions on electrocrystallization process of zinc

Cyclic voltammetry, chronoamperometry and scanning electron microscopy were employed to study the influence of Zn^2 ion concentration in electrolyte solutions on zinc electroplating process. The results show that, at high overpotentials, the nucleation of zinc is instantaneous, and nuclear density increases with the overpotentials increasing. While at low overpotentials, the zinc may be preferentially electrodeposited on surface inhomogeneities such as emergence points of edge, screw dislocations, atomic disorder, kink sites, or monoatomic steps, and no distinguished nucleation current can be observed. The major dissolution peak in cyclic voltammogram drifts positively due to the change of the rate-determining step of zinc electroplating processes from diffusion to the electrochemical reaction with the increase of Zn^2 ion concentration.     

Selective extraction of zinc from sulfate leach solution of zinc ore

1　INTRODUCTIONSolventextractionwasregardedasahighlyeffi cienttechniqueofseparationandpurification .Ithasbeenwidelyappliedinmetalextractionandrecoveryduringhydrometallurgicalprocessandenvironmentalprotection[14 ] .Solventextractionhasbeencommer ciallyusedintheextractionofuranium ,rarenoblemetals ,copper ,cobaltandnickel,whichwastypical lypresentedbythetechniqueofleach solventextrac tion electrowinning .Presently ,thecopperproductionfromsolventextractionhasbeenaccountedformorethan 2 0 %oft…     

Electrodeposition of zinc and composite zinc–yttria stabilized zirconia coatings

Pure zinc and composite coatings of zinc and nano-sized yttria stabilized zirconia (YSZ) particles were prepared by cathodic electrodeposition from zinc sulphate-based electrolytes containing gelatin. The effects of gelatin on the morphology, crystallographic orientation of the zinc coatings and deposition mechanism of the composite Zn–YSZ coatings were studied. The coatings obtained were studied by scanning electron microscopy (SEM) with energy dispersion spectroscopy (EDS), X-ray diffraction and potentiodynamic polarization measurements. It was shown that the addition of gelatin to the electrolyte significantly changed the microstructure and crystallographic orientation of the zinc deposits and improved the coating microhardness. In the case of the composite coating co-deposition process, the YSZ particles were found to preferentially rest on the edges or macrosteps of the deposited zinc crystals. The incorporation of YSZ particles into the composite coating was enhanced by reducing the solution pH and through the addition of gelatin. The mechanical and electrochemical properties of conventional zinc coatings were observed to be significantly improved by the incorporation of YSZ particles.     

The effect of additives on zinc deposited from zinc sulfate solutions

Zinc is industrially electrowon from acid zinc sulfate solutions at ambient temperatures. Some refining agents are usually added to improve the deposit qualities. Gelatin is a traditional additive, but other additives are also used. In the investigation described here, the basic parameters of deposition (e.g., current density, acid concentration, and zinc concentration) were optimized. Gelatin and a tetraalkylammonium salt (TAS) were used separately and in combination as grain refiners of the cathodic deposits. Current efficiency determination experiments were performed to investigate the role of these additives. Scanning electron micrographs of the cathodic deposits were obtained to examine the surface qualities of deposits at certain conditions. Results showed that gelatin is generally a better refiner, although TAS may be used in concentrations of 0.074 mg/l to 1 mg/l. A mixture of the two additives resulted in a decrease of current efficiency.     

XPS study of zinc hydroxide as a potential corrosion product of zinc: Rapid X-ray induced conversion into zinc oxide

A detailed investigation of a potential corrosion product of zinc – zinc hydroxide – using X-ray photoelectron spectroscopy (XPS) was performed to shed light on remarkable inconsistencies in the literature reported reference data, being the key element for the evaluation of the unknown experimental spectra. Our study gives an explanation, showing that zinc hydroxide possesses a highly unstable nature resulting in rapid degradation and leading to the formation of zinc oxide during standard XPS measurements. Furthermore, a probable mechanism of the observed phenomenon, X-ray induced material degradation, is proposed and discussed.     

Electrodeposited zinc alloy coatings

This review examines the range of zinc alloy electrodeposited coatings that are available as finishes for continuous steel strip and also possible replacements for electroplated cadmium. Each system is described in terms of available electrolytes, physical properties and corrosion resistance. It is apparent that zinc-nickel, zinc-iron and zinc-cobalt are the most widely utilized, although zinc-manganese, which appears to have excellent corrosion resistance, is in all probability unavailable commercially. Zinc-tin is also discussed, being recognized as another possible replacement for cadmium.