Atmospheric oxygen-rich direct leaching behavior of zinc sulphide concentrate

The leaching behavior of main metallic sulphides in zinc concentrate under atmospheric oxygen-rich direct leaching conditions was studied through mineralogical analysis. The results show that the sulphides dissolve obviously except pyrite. Based on the relationship between elemental sulfur and the residual sulphides in the leaching residue, the dissolution of sphalerite, chalcopyrite, covellite and galena is assumed to follow the indirect oxidation reactions, where the acidic dissolution takes place firstly and then the released H2S transfers from the mineral surface into bulk solution and is further oxidized into elemental sulfur. The interface chemical reaction is further supposed as the controlling step in the leaching of these sulphides. The direct electrochemical oxidation reactions are assumed to contribute to the dissolution of pyrrhotite, which is controlled by the diffusion through elemental sulfur layer.

Kinetics of zinc sulfide concentrate direct leaching in pilot plant scale and development of semi-empirical model

The direct leaching kinetics of an iron-poor zinc sulfide concentrate in the tubular reactor was examined.All tests werecarried out in the pilot plant.To allow the execution of hydrostatic pressure condition,the slurry with ferrous sulfate and sulfuric acidsolution was filled into a vertical tube(9m in height)and air was blown from the bottom of the reactor.The effects of initial acidconcentration,temperature,particle size,initial zinc sulfate concentration,pulp density and the concentration of Fe on the leachingkinetics were investigated.Results of the kinetic analysis indicate that direct leaching of zinc sulfide concentrate follows shrinkingcore model(SCM).This process was controlled by a chemical reaction with the apparent activation energy of49.7kJ/mol.Furthermore,a semi-empirical equation is obtained,showing that the order of the iron,sulfuric acid and zinc sulfate concentrationsand particle radius are0.982,0.189,-0.097and-0.992,respectively.Analysis of the unreacted and reacted sulfide particles bySEM-EDS shows that insensitive agitation in the reactor causes detachment of the sulfur layer from the particles surface in lowerthan60%Zn conversion and lixiviant in the face with sphalerite particles.

Direct microwave leaching conditions of rare earth elements in fluorescent wastes

The luminescent phosphor powder in the fluorescent lamp constitutes 2%of the lamp’s weight.It can be mentioned that fluorescent wastes are a crucial raw material to produce rare earth oxides.In the present study,microwave leaching process was conducted to dissolve rare earth elements yttrium(Y),europium(Eu),and remaining rare earth elements(REEs)present in the phosphor powder of the fluorescent lamp.and the yields were compared.In the microwave leaching process,the effects of the temperature(80-160℃),acid type(hydrochloric acid(HCl),nitric acid(HNO_(3)),sulphuric acid(H_(2)SO_(4))),acid concentration(0.5-6 mol/L),solid to liquid ratio(0.1:10-0.5:10)and reaction time(5-90 min)parameters on leaching efficiencies of varying rare earth elements and calcium were investigated.The highest yield was obtained in the direct microwave leaching of fluorescent waste with the experimental conditions of 6 mol/L HCl,160℃,0.1:10 solid-to-liquid ratio(S:L),and 90 min.Activation energy calculations were made,and kinetic models of the reactions were obtained,and it is observed that Y and Eu dissolution is diffusion-controlled,on the other hand,lanthanum(La),cerium(Ce),and terbium(Tb)were examined to be chemical reaction controlled.Moreover,calcium(Ca)and gadolinium(Gd)seem coherent with the mixed model.Concurrently,mathematical models of all experimental studies are created with the response surface Box-Behnken method and the correlation coefficients of all the models are over 90%.

铁成分对硫化锌精矿的半导体性质及化学反应性的影响

硫化锌精矿(以下简称精矿)除含有主要元素锌与硫外,还含有其它元素,尤其是含有相当多的铁。在湿法处理精矿时,其铁成分的行为取决于铁的矿物存在形式。精矿中的铁可以铁闪锌矿[(Zn,Fe)S)、黄铁矿、黄铜矿的形式存在。铁闪锌矿的铁含量可在很大的范围内变化,其物理化学性质也随铁含量而变化,因此对精矿的湿法直接处理产生很大的影响。本文研究出一种可靠的、确定精矿矿物组成的化学分析方法,着重于测定铁在精矿各矿物中的分布,及铁闪锌矿铁含量的变化规律。在此基础上,实验研究了精矿中的铁(尤其是铁闪锌矿中的铁)对精矿的半导体性质的影响规律,应用半导体电化学原理讨论了精矿铁含量对精矿的直接浸出(常压、硫酸介质)的影响机理。

A method for recovery of iron,titanium,and vanadium from vanadium-bearing titanomagnetite

An innovative method for recovering valuable elements from vanadium-bearing titanomagnetite is proposed. This method involves two procedures： low-temperature roasting of vanadium-bearing titanomagnetite and water leaching of roasting slag. During the roasting process, the reduction of iron oxides to metallic iron, the sodium oxidation of vanadium oxides to water-soluble sodium vanadate, and the smelting separation of metallic iron and slag were accomplished simultaneously. Optimal roasting conditions for iron/slag separation were achieved with a mixture thickness of 42.5 mm, a roasting temperature of 1200°C, a residence time of 2 h, a molar ratio of C/O of 1.7, and a sodium carbonate addition of 70 wt%, as well as with the use of anthracite as a reductant. Under the optimal conditions, 93.67% iron from the raw ore was recovered in the form of iron nugget with 95.44% iron grade. After a water leaching process, 85.61% of the vanadium from the roasting slag was leached, confirming the sodium oxidation of most of the vanadium oxides to water-soluble sodium vanadate during the roasting process. The total recoveries of iron, vanadium, and titanium were 93.67%, 72.68%, and 99.72%, respectively.