Separation of iron sphalerite from pyrrhotite

Abstract: the flotation reagent, flotation theory, the sorting process describes the research on the present situation sphalerite and pyrrhotite separation techniques, and pointed out the following shortcomings which the sorting process, efficient marmatite The performance of collectors and activators is not high and the selectivity of pyrrhotite inhibitors is not enough. The theoretical research is not comprehensive enough, and the sorting process is single. Strengthening the theoretical study on the separation of iron sphalerite and pyrrhotite, the development of new agents, and the optimization of the separation process will become the development direction of the separation of iron sphalerite and pyrrhotite in the future.

Key words: iron sphalerite; pyrrhotite; flotation reagent; flotation theory, process

With the gradual reduction of zinc resources in the easy-selected sphalerite, the development and utilization of complex refractory zinc resources dominated by iron sphalerite has become particularly important. The floatability of iron sphalerite is very close to that of pyrrhotite and pyrite, and the magnetism is very close to that of pyrrhotite. Typically MARMATITE with pyrrhotite and symbiotic in the same ore body, such that the sorting greatly increased the difficulty, so that the zinc metal recovery is low or difficult to obtain a high quality zinc concentrate. Therefore, the successful solution to the problem of efficient separation of iron sphalerite and pyrrhotite is the key to the development of iron sphalerite.

1 Properties of iron sphalerite and pyrrhotite

The main reason why iron sphalerite and pyrrhotite are difficult to separate is that they have many similar physical and chemical properties.

Usually, iron is mixed into the sphalerite with the same type of isomorphism. When the iron content of the sphalerite is more than 6%, it is called iron sphalerite. Its chemical formula is (Zn, Fe)S, and the iron sphalerite contains the highest iron. Up to 26.2%. The iron content of iron sphalerite depends mainly on the genesis of the deposit and the formation process of the deposit. Since the zinc atom on the zinc blende crystal lattice is replaced by Fe3+, the valence and charge state are out of balance, resulting in two Zn2+ becoming Zn+, reducing the hole concentration and increasing the electron density, making the sphalerite and xanthate When the anion acts, it generates a certain repulsive force, which is not conducive to the adsorption of the collector, thus affecting its floatability. Therefore, the floatability of the iron sphalerite is lower than that of the sphalerite. On the other hand, since the iron sphalerite has a high iron content, it has a certain magnetic property, and the higher the iron content, the stronger the magnetic properties.

The amount of iron in pyrrhotite is usually different, usually expressed by Fe1-xS, and generally x is about 0 to 0.223. The floatability of pyrrhotite is closely related to its crystal structure, chemical composition and oxidative properties. When the crystal structure is a monoclinic lattice structure, it is ferromagnetic and has poor floatability; when it is a hexagonal lattice structure, the magnetic properties are weak and the floatability is good, but the floatability is lower than that of pyrite.

Status Study zinc ores of the magnetic iron pyrite flash 2

2.1 Research on mineral processing chemicals

2.1.1 Study on pH value of flotation medium

The pH value of the medium in the flocculation recovery operation of iron sphalerite is the key factor affecting the recovery rate. Generally, when the flotation of iron sphalerite is carried out by the traditional “high alkali sulfur suppression” process, the iron sphalerite is significantly inhibited and recycled. The rate is low.

When using impact Liurong Rong Marmatite MINERALS investigated Marmatite amount of lime floating rate, in the case of the activator without the copper sulfate used Marmatite butyl xanthate as collector, in an amount of 3.125×10-3mol/L, with the increase of lime dosage, the floating rate of iron sphalerite is decreasing. When the amount of lime is 1.25g/L, the pH value of the solution is 12.23, the single mineral floating rate of iron sphalerite. Only 6.82%. It can be seen that the pH value of the lime or slurry has a great influence on the floating rate of the single mineral of the iron sphalerite. The higher the pH value of the slurry, the lower the floating rate of the single mineral of the iron sphalerite.

Luo Xianping's people used an iron-bearing sphalerite zinc mine in Anhui as the research object. When sorting the iron sphalerite, lime was used as the pulp pH adjuster, and it was found that the high-alkali condition was unfavorable for zinc flotation. To obtain a better flotation index, the pH of the pulp must be controlled between 10 and 11.

When Xi Hui Fang et al exploring a low grade lead-zinc ores Qinghai refractory dressing process found a reasonable choice, marmatite and pyrrhotite flotation very close, high pH when the pulp is inhibited pyrrhotite At the same time, the iron sphalerite has also been strongly inhibited, resulting in a low zinc recovery rate, and the optimum pulp pH value for iron sphalerite flotation is 10.5.

It can be seen from the pH of the flotation medium that the recovery rate of the iron sphalerite flotation process decreases with the increase of the pH value of the medium, and the optimal pH value of the flotation medium should be controlled at 10-11.

2.1.2 Study on the activator of iron sphalerite

Single zinc deposits are rare, often associated with copper, lead, sulfur, etc., when flotation is sorted, they are often used in the preferential flotation process of zinc-suppressing lead (copper), zinc minerals are strongly suppressed, therefore, An activator is added during the flotation of the zinc mineral. In addition, the iron sphalerite exhibits poor planktonicity, is not easy to activate, and is sensitive to the medium, and it is very similar to the pyrrhotite. Therefore, the research on the high-efficiency activator of iron sphalerite is more urgent. Iron sphalerite activators include copper, lead, silver , cadmium ions, various new activators, etc. Among them, Cu2+ is the most widely used iron sphalerite activator.

Cu2+ is a mature research and application technology for iron sphalerite activator, and it is also the most widely used. When Cu2+ is used as the activator of iron sphalerite, it has the characteristics of strong activation ability, stable flotation process and simple drug addition operation. Nie Guanghua et al. carried out flotation experiments on an iron sphalerite, using copper sulfate as the activator of iron sphalerite. Among them, the amount of copper sulfate was 1000g/t, and zinc concentrate containing 48.41% zinc and 92.42% zinc recovery was obtained. mine. Li Zhifeng used the 500g/t copper sulfate as the zinc mineral activator in the process of zinc leaching to obtain the zinc concentrate containing 45.13% zinc and 90.77% zinc recovery rate in the zinc ore-bearing polymetallic ore of Liaoning Qingyuan. mine.

Leng Chongyan et al studied the effect of ammonium salt on the flotation behavior of iron sphalerite. Under certain conditions, the most common five ammonium salts were used to study the activation of iron sphalerite. The study indicated that the recovery rate of iron sphalerite was 48% when ammonium sulfate was used as the activator; the recovery rate of iron sphalerite was 92% when ammonia sulfite was used as the activator; and ammonium chloride was used as the activator. At the time, the recovery rate of iron sphalerite can reach 95%, but the amount of ammonium chloride is large. The order of activation effect of five ammonium salts on iron sphalerite is: ammonium chloride > ammonium sulfite > ammonium sulfate > ammonium thiosulfate > ammonium persulfate.

Xie Xian, Tong Xiong et al. used the iron sphalerite single mineral selected from the Yunnan lead-lead ore as the research object, and used butyl xanthate as the iron sphalerite collector to investigate lead nitrate, ammonium chloride and sulfuric acid. The difference in activation properties between copper and T-1 on iron sphalerite shows that each activator has a certain activation effect on iron sphalerite, among which copper sulfate and T-1 have the strongest activation ability. Copper sulphate has the best activation effect when the pH value of the medium is equal to 13, and the highest recovery rate of iron sphalerite is 61.30%. The new activator T-1 has the best when the pH of the medium is equal to 10 and its dosage is 700g/t. The activation effect, at this time, the recovery rate of the iron sphalerite was 64.10%.

At present, Cu2+ is still dominant as an iron sphalerite activator. Its activation ability is insufficient, and the current cost of pharmaceuticals has not changed. Research on a new type of iron sphalerite activator that is more efficient and more affordable is urgent.

2.1.3 Study on pyrrhotite inhibitors in the flotation process of iron sphalerite

The role of inhibitors in the flotation separation of iron sphalerite and pyrrhotite is very critical. Selective inhibition of pyrrhotite can greatly improve the grade of zinc concentrate and obtain better quality zinc concentrate. Therefore, the research on selective inhibitors of pyrrhotite is very important, and many scholars have carried out a lot of research.

When Fang Xihui et al. studied a low-grade refractory lead-zinc ore in Qinghai, lime was used as an inhibitor of pyrrhotite and pyrite in the process of flotation zinc, and a higher quality zinc concentrate was obtained. Li Zhifeng also used lime as an inhibitor of pyrrhotite in the ore dressing test of Qingyuan iron-sphale-zinc polymetallic ore in Liaoning, and successfully separated it from iron sphalerite.

Sun Wei and other studies have shown that when the organic inhibitor DMPS inhibits pyrrhotite, the adsorption of DMPS with hydrophilic groups on pyrrhotite indicates that it hinders the action of xanthate and pyrrhotite; Xu Jing et al. The organic inhibitor RC can also prevent the action of xanthate and pyrrhotite, thereby achieving flotation separation of iron sphalerite and pyrrhotite.

Chen Zhongjin et al. studied the single minerals of iron sphalerite and pyrrhotite. In neutral medium, the combination of calcium chloride and sodium humate was used as the pyrrhotite inhibitor, and the iron sphalerite was successfully realized. Separation from pyrrhotite mixed ore. Canadian Patent No. 2082831 describes that in the flotation of sulfide ore containing pyrrhotite or iron sphalerite, the use of calcium polysulfide and polyamine to adjust pulp can effectively inhibit pyrrhotite. Polyamine is a strong chelating agent. This amine can reduce the concentration of metal ions in the pulp. At the same time, polyamine can greatly reduce the adsorption of xanthate on the pyrrhotite surface and inhibit the pyrrhotite.

Lime is the most commonly used inhibitor of pyrrhotite and pyrite. When the dosage is small, the inhibition strength is insufficient, and the separation effect is poor. When the dosage is too large, the iron sphalerite is also inhibited, resulting in a low zinc recovery rate. It is still difficult to find highly selective pyrrhotite inhibitors among many inhibitors, so it is imperative to develop highly selective pyrrhotite inhibitors.

2.1.4 Study on iron sphalerite collector

The search for collectors with high selectivity to iron sphalerite is the key to the effective separation of iron sphalerite and pyrrhotite. Therefore, the study of iron sphalerite collectors is very important.

Wu Bozeng et al. used butyl xanthate as the iron sphalerite collector. When the pH of the medium is less than 6.0, the iron sphalerite has good floatability, and the recovery rate can reach 60%, followed by the pH value. The recovery rate of iron sphalerite is gradually reduced. When pH=9.18 and pH=11.0, the recovery rate of iron sphalerite is less than 50% no matter how the slurry potential is adjusted. The adsorption and oxidation of butyl xanthate on the surface of iron sphalerite forms a hydrophobic substance to enhance the floatation of minerals; under high alkali conditions, the oxidation of iron sphalerite itself severely blocks the surface of butyl xanthate on its surface. Adsorption and oxidation form a hydrophobic substance.

Yang Wei [18] studied the flotation mechanism with butylammonium black as a collector in iron sphalerite. The results show that the iron sphalerite is buoyant under weak acidic and neutral medium conditions. ammonium aerofloat chemical adsorption, generated in the surface of the iron surface bis aerofloat sphalerite, sphalerite added Cu2 + surface generates a positive dibutyldithiocarbamate copper iron phosphate, iron sphalerite be floatability Greatly improved.

Luo Xianping uses a combination of fatty acid-based collectors in the treatment of an iron sphalerite. The combined collector enhances the surface adsorption and fixation strength of zinc in the iron sphalerite crystal lattice, and enhances the zinc flash The surface of the mine is hydrophobic, which is beneficial to increase the recovery rate of zinc. Reported XITIESHAN concentrator sphalerite flotation is the use of iron-based diesel, supplemented by a combination of butyl xanthate collector, can solve the flash separation of zinc and iron pyrite, Better industrial indicators obtained. The zinc concentrate grade obtained by industrial tests increased by 3.72% and the zinc recovery rate increased by 10.85%. In the Xilin lead-zinc mine, the combination of diesel-based and butyl-xanthine was used to select the iron sphalerite. The zinc concentrate grade was increased by 2.3% and the zinc recovery rate was increased by 5.48%. Under normal circumstances, the use of a combination of collector flotation iron sphalerite is better, and the combination of non-polar collector and anionic collector is more effective.

Yang Jiuliu used a new collector ZC as a zinc mineral collector when sorting an iron sphalerite. Studies have shown that ZC has a strong collection capacity and good selectivity for iron sphalerite, and the combination of GF is used. The foaming agent can obtain a better enrichment and sorting index for the iron sphalerite.

The combination of butyl xanthate and other collectors as the additive of the iron sphalerite collector showed stronger harvesting performance, obtained higher sorting index, combined collector The use of iron sphalerite flotation brings greater development value.

2.2 Flotation theory research

The theory of flotation theory is to explain the mechanism of action in the flotation process in a deeper way, thus promoting the development of the separation technology of iron sphalerite and pyrrhotite.

2.2.1 Study on adsorption mechanism

The mineral processing agents and minerals are mainly adsorbed. The adsorption forms, adsorption capacity, adsorption strength and external factors affecting the adsorption of the agents and minerals have important guiding significance for the flotation of minerals.

Yu Runlan and others believe that when ethyl xanthate is used as the iron sphalerite collector, the surface of the iron sphalerite is positively charged under weakly acidic conditions, which is beneficial to the adsorption of ethyl xanthate anion (X-). The adsorption amount is large; under alkaline conditions, the surface of the mineral is negatively charged, which is not conducive to the adsorption of ethyl xanthate anion (X-). The adsorption amount is small. The higher the pH value, the stronger the surface electronegativity of the iron sphalerite. The smaller the adsorption amount of xanthate anion (X-). Therefore, the amount of adsorption of the xanthate on the surface of the iron sphalerite decreases as the pH increases. When the pH value is 7, ethylxanthate and iron sphalerite act on the surface to form a hydrophobic dixanthin, but under weakly acidic conditions, a small amount of EPX salt is formed, and under weak alkaline conditions, A small amount of MTC salt is formed.

Raofeng believes in the mechanism of Cu2+ activated iron sphalerite: 1Since the iron sphalerite is mostly an electronic semiconductor, there is a large amount of electron enrichment on the lattice surface, so it is difficult to stably adsorb xanthate. Part of Cu2+ is adsorbed on the surface of the mineral. These divalent copper ions can take electrons from the surface layer of the iron sphalerite crystal lattice, so that the electron concentration of the surface layer of the sphalerite is decreased, and the surface conductivity of the sphalerite is changed from electronic to empty. After the hole type, the yellow drug can be stably adsorbed. 2 When the flotation process is carried out in a weakly alkaline or neutral medium, the added Cu2+ is first hydrolyzed to copper hydroxide or a basic salt, and these hydrolyzed products can also activate the iron sphalerite. The hydrolyzed product is ionized in solution and produces a small amount of Cu2+, Cu(OH) ions, which are rapidly adsorbed by the surface of the iron sphalerite and form copper sulfide. Since the solubility product of Cu(OH)2 is larger than that of CuS, the process of ionizing copper hydroxide into CuS will continue to be carried out and deposited on the surface of iron sphalerite in the form of a copper sulfide film to achieve the activation effect.

Xu Jing and other studies have shown that the organic inhibitor RC has an inhibitory effect on pyrrhotite because RC and xanthate collectors with a large number of hydrophilic groups compete for adsorption on the surface of pyrrhotite, and RC is in magnetic yellow iron. The adsorption rate indicated by the mine is higher than that of the xanthate, which hinders the adsorption of xanthate on the surface of the pyrrhotite, that is, inhibits the floating of the pyrrhotite.

Through the study of the adsorption mechanism of the drug, it is possible to select the agent more accurately for the separation of the iron sphalerite and the pyrrhotite to obtain a better flotation separation index. Therefore, the study of adsorption mechanism can not only provide a theoretical basis for its flotation separation, but also improve the economic benefits of iron sphalerite selection.

2.2.2 Electrochemical theory research

The electrochemical theory of sulfide ore flotation mainly studies the electrochemical reaction of sulfide mineral in the flotation system and the sulfide mineral-solution interface. The electrochemical reaction is divided into three aspects: the electrochemical reaction of the collector on the mineral surface; the mineral surface. The effect of electrostatic potential on the action of the agent; the effect of the slurry potential on the flotation process. Both iron sphalerite and pyrrhotite belong to sulfide ore, and the electrochemical theoretical research on it is mainly the study of electrochemical reaction at the mineral-solution interface.

During the flotation process of iron sphalerite, the planktonicity is significantly affected by the pulp potential and the pulp pH value. When butyl xanthate is used as the iron sphalerite collector, Wu Bozeng et al. believe that the iron sphalerite is at pH<6.0. The recovery rate is >60%, and the floatability is good. Under the weak alkaline condition of pH>8.0, the recovery rate is drastically decreased, and the floatability is poor. When pH=6.0, the recovery rate of iron sphalerite in the potential range of 0.2-0.6V is >50%; when pH=9.18 and pH=11.0, the recovery rate of iron sphalerite is lower than that of the slurry potential. 50%, because under the stronger alkaline conditions, the S0 on the surface of the iron sphalerite is rapidly corroded into SO42- and it is not easy to adsorb the collector, that is, the oxidation of the iron sphalerite itself seriously blocks the butyl yellow. The adsorption and oxidation of the drug on its surface forms a hydrophobic substance.

In the process of flotation, iron sphalerite and pyrrhotite will produce hydrophobic substances on the surface of minerals due to their own oxidation. For example, element S0, etc., mineral oxidation is closely related to slurry potential and pH value, so it can adjust the slurry potential. And pH to control the electrochemical reaction of the mineral surface, Ma Pioneer believes that when the pulp potential is >0.3V or the pH value is >11.0, the S0 produced on the surface of the pyrrhotite will be reduced, and the floatability of the pyrrhotite will be reduced. Cheng Hao's research found that when the pH value of the pulp is between 6.86 and 10.1, the corrosion current of the iron sphalerite increases with the increase of the pH value, that is, the oxidation reaction rate of the surface corrosion of the iron sphalerite increases. When the Fe2+ detached iron sphalerite crystal lattice enters the solution, it is easy to oxidize and hydroxylate the iron sphalerite to form a “hydroxylated sulfur-rich intermediate state”. With the increase of pH value, this intermediate state-hydroxylated sulfur-rich layer The worse the stability, the faster the oxidative corrosion reaction rate. When the pH is >11.0, the corrosion current decreases again, which may be related to the oxidation of the mineral surface to directly form Fe(OH)3, SO42-, ZnO22-, which makes the floatation of the iron sphalerite worse.

Electrochemical theoretical studies reveal the relationship between the floatation of iron sphalerite and pyrrhotite during flotation and the pulp potential and pH. The two mines have their own optimal flotation potential and pH value. If potential-controlled flotation can be applied to the flotation separation process of iron sphalerite and pyrrhotite, the cost of flotation reagent will be greatly reduced, the sorting effect will be improved, and the flotation time will be reduced.

2.3 Process Research

The iron sphalerite is very similar to the pyrrhotite, and the separation is difficult. The research on the separation and separation process has never stopped. At present, the following processes are mainly included.

(1) A conventional single “sulphur suppression float zinc” process. Wang Rendong and others selected a high-alkali process of “sulphur-reducing zinc” to select a zinc concentrate with a zinc recovery rate of 85.66%. Nie Guanghua et al. also used this process to conduct a flotation test on an iron sphalerite to obtain a zinc concentrate containing 48.41% zinc.

(2) First magnetic post-floating process. Luo Xianping people take a low-grade lead-zinc ore in Inner Mongolia as the research object. The zinc in the mine mainly exists in the iron sphalerite and contains a large amount of pyrrhotite, which cannot be qualified under the sulfur-suppressing zinc process. Zinc concentrate, using the "weak magnetic separation separation of pyrrhotite - weak magnetic separation tailings floating zinc" process, obtained 44.11% zinc qualified zinc concentrate.

(3) Sulfur-dissolved zinc-medium ore separate treatment process. In the original process of Chehe Concentrator, the medium-mineral sequence return mode was adopted, but the pyrrhotite which was suppressed during the selection was returned to the foam product after the previous operation, which caused a vicious cycle, which was not only difficult to obtain qualified zinc concentrate. Mines, and also increase the zinc recovery rate when increasing the amount of inhibitor lime. In response to this situation, Guangzhou Nonferrous Metals Research Institute proposed a separate treatment process for medium and small mines, that is, the concentrate is first concentrated, de-druged, returned to re-grind and re-selected, which changes the surface properties of pyrrhotite and is beneficial to inhibit pyrrhotite. Solved the problem of the selection plant.

(4) Leaching process. The leaching process is often used to treat iron sphalerite concentrates that have a lower grade than the smelting requirements. Such iron sphalerite concentrates often contain large amounts of pyrrhotite. Wang Shuming et al. used a high-oxygen ammonia leaching process to treat a certain iron-sphalerite concentrate at a temperature of 25 ° C, an oxygen partial pressure of 600 kPa, and a leaching time of 8 h to obtain a zinc leaching rate of 97% and an iron leaching rate of less than 0.5%. Good indicator. Liu Wei et al. treated the iron sphalerite concentrate by acid leaching at 100 ° C, 4 atmospheres and leaching time of 3 h, and obtained a zinc leaching rate of 93%.

The above four process flows are commonly used in the separation of iron sphalerite and pyrrhotite ore, and have been widely used in many mines, and have achieved good economic benefits. However, due to the different iron content of iron sphalerite and pyrrhotite in different places, the ore properties are also different. Therefore, the selection of suitable process is of great significance for the separation of iron sphalerite.

3 Conclusion and outlook

In recent years, research on the separation of iron sphalerite and pyrrhotite has made some progress, and the application of these studies to production has achieved certain economic benefits, but the separation efficiency is low, the quality of zinc concentrate is poor, and iron sphalerite The problem of low recovery rates remains unresolved. The main manifestations are as follows: Firstly, the status of separation of iron sphalerite and pyrrhotite under high alkali conditions has not been improved, and the new high-efficiency sphalerite collector technology is not yet mature, and the high-efficiency iron sphalerite activator is not mature. The pyrrhotite inhibits the selectivity is not strong; secondly, the theoretical study on the separation of iron sphalerite and pyrrhotite is not comprehensive enough, the research depth is not enough; finally, the process flow is single. In order to improve the separation effect of iron sphalerite and pyrrhotite, strengthen theoretical research on iron sphalerite and pyrrhotite, develop new high-efficiency flotation reagent, and optimize the separation process is iron sphalerite and magnetic The development direction of pyrite separation research.

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