2017年12月26日星期二

Ammonium Paratungstate Waste Recycle

In the production, sometimes for some reason lead to part of the APT products in the classics or physical performance on the failure, may also occur in the production process a small amount of ammonium paratungstate waste recycle, which are recyclable.

ammonium tungstate image

Recycle of unqualified ammonium paratungstate method is mainly after the dissolution of the filter, and recrystallization, for this reason, the APT is dissolved at a higher temperature directly with ammonia as a solvent, however, APT solubility in aqueous ammonia is limited, resulting in dilute solution concentration, it takes for a long time to dissolution. Therefore, the modern industry began to use of APT thermal decomposition into ammonium metatungstate for recycle.

Thermal decomposition of the working mechanism is to control the appropriate temperature, calcined APT can be converted to ammonium metatungstate (AMT).

According to the high temperature decomposition performance of APT·4H2O, when heated APT·4H2O in the air, First dehydrated at about 100 °C, and then decomposed at 190 °C to 250 °C to dissolve the amorphous ammonium formate. Some scholars have experimented with unqualified calcined tungstate calcination temperature at 280 °C is better, the product has the highest leaching rate in aqueous ammonia at 25% concentration, it can up to 99.6%. Therefore  the calcination treatment is carried out at an appropriate temperature in advance so that the unqualified APT can better soluble in the NH3 solution and can create better recycle conditions for the unqualified ammonium paratungstate.

After the calcination treatment of APT by pure water leaching, leaching pH control in 3-4, after leaching filtration, evaporation crystallization can be obtained ammonium metatungstate.

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Ammonium Paratungstate Preparation Method

Ammonium paratungstate (APT) preparation is an important part of smelting tungsten, whether it is using chemical precipitation method, ion exchange method or extraction method, it all have to go through the process of ammonium trioxide to produce qualified APT.

preparation of ammonium paratungstate image

APT is an important tungsten intermediate product, the higher the purity the greater the value, so APT preparation process is also the further purification of tungsten.

Commonly used method for preparing ammonium paratungstate is evaporation crystallization method, neutralization crystallization method and frozen crystallization method.

Evaporation crystallization method is heating evaporation solvent, so that the solution from unsaturated to saturated, continue to evaporate, the excess solute will be crystal precipitation, called evaporation crystallization method. This method of technology and equipment is simple, easy to large-scale, this method technology and equipment is simple, easy to large-scale, at the same time it has a purification effect, so it’s universal.

And the crystallization is at room temperature neutralizing (NH4)2WO4 solution with hydrochloric acid, dissolving out the ammonium paratungstate crystals.This method has small energy consumption, fast crystallization, and easy to recycle fine particles APT.

Frozen Crystallization In water-cooled vacuum drying, water and APT crystallize at the same time, but then remove the water and leave the dry APT. The advantage of this method is that it can produce ultrafine powder and obtain a homogeneous composite powder.

In addition to the above three common methods, the industry also uses other methods to produce high purity ammonium paratungstate, such as neutralization - evaporation crystallization, extraction, recrystallization, electrolysis. There are many methods and they all have their own merit and demerit. In conclusion, In addition, the main problems of the preparation of ammonium paratungstate crystals are the removal and control of the crystalline morphology to meet the needs of the final tungsten product as the standard.

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The Crystallization of Ammonium Paratungstate

Ammonium paratungstate (APT) is an important tungsten intermediate product, mainly with white crystals.

It have flakes, needles and strips three kind, used in the manufacture of tungsten trioxide or blue tungsten oxide, TP,  also used for manufacturing ammonium metatungstate and other tungsten compounds.

ammonium paratungstate image

Because the production of tungsten oxide, morphology and particle size of tungsten powder has genetic relationship with APT, so the production process is not only to the tungsten APT purification, but also to control the crystal morphology and particle size of paratungstate tungstate.

In the 1950s, in the book "Tungsten and Molybdenum Metallurgy" by A.H rickman, used the reaction 5(NH4)2O·12WO3·nH2O to describe the APT formula, used the evaporation crystallization process to get n = 5 flaky crystal, and used the acid neutralization process for n = 11 needle crystal. After that in China are all using this view, that of ammonium tungstate solution producing is a ammonia chemical process of paratungstate tungstate lost, the crystallization process of chemical reaction is:

12(NH4)2WO4===5(NH4)2O·12WO3·5H2O+2H2O +14NH3

(N = 5 temperature> 50 °C to obtain flaky crystals)

12(NH4)2WO4+4H2O===5(NH4)2O·12WO3·11H2O+14NH3

(N = 11, temperature <50 °C to obtain needle-like crystals)

APT crystal water content and crystal shape depends on the crystallization conditions, the current study that APT has three crystalline morphology.

 APT·10H2O is needle-like or strip-like orthorhombic structure, it is unstable in the industrial crystallization conditions, at least 50 °C below the crystal can be obtained in this crystal.

2. APT·12H2O is a triad flake crystal, which is a crystal in the state of metastable state in water. It is a metastable phase at the boiling point of (NH4) 2WO4 solution, and only when the concentration of WO3 in the solution is more than 30%, the concentration of NH3 more than 5% of the conditions can be generated, with the extension of storage time, it will happen recrystallization and turn into APT·4 H2O.

APT·4H2O is a monoclinic cubic structure, which is always stable under industrial crystallization,  means from WO3 concentration higher than 30%, NH3 concentration is greater than 5% to WO3 concentration less than 10%, in a solution of NH3 was 1%, slightly better in 90-100 °C temperature range as long as there is APT·4 H2O exists, the seed can produce APT·4 H2O crystallization.

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Ammonium Paratungstate Preparation -- Neutralization Method

Ammonium paratungstate (APT) preparation is an important part of smelting tungsten, whether it is chemical precipitation method, ion exchange method or extraction method,they all have to go through the process of ammonium trioxide to produce qualified APT. 

preparation of ammonium paratungstate image

 APT is an important tungsten intermediate products , the higher the purity the greater the value, so APT preparation process is also the further purification of tungsten.

Neutralization is one of the most commonly used manufacturing method of para-ammonium tungstate, and it's settlement with hydrochloric acid and (NH4) 2  wo4 solution, precipitation crystallization of ammonium paratungstate, and the energy consumption is small, crystallization speed is fast, easily to recovery the fine particle APT.

The neutralization method is carried out in a reaction tank with a liner rubber. Heating with hydrochloric acid and (NH42WO4 solution, ammonium paratungstate crystallization, the reaction is:

12(NH4)2WO4+14HCl+4H2O==5(NH4)2O·12WO3·11H2O+14NH3Cl

Putting (NH4) 2WO4 liquid into the reaction tank, and heat the temperature according to the requirements of the granularity of APT, general particle in about 75 °C, coarse particle above 90 °C, the fine particles under 50 °C.Under the intense agitation, slowly add concentration about 10% - 20% of hydrochloric acid, neutralization to pH 7-7.5, stop adding hydrochloric acid, thermal mixing 0.5 hours,make the pH stable, stand for 8-10 hours, 90% to 95% of tungsten in the solution generated APT precipitation. To get the needle after washing with deionized water containing 11 crystallization water of crystallization of ammonium paratungstate.

Compared with the evaporation method, the neutralization method has the advantages of low energy consumption, fast crystallization and easy access to fine particles APT, but sometimes the grain size of the crystal is very fine, which is not conducive to filtration and washing, but also easy to bring impurities.the acid reagent corrosion equipment, the reagent consumption is large, virtually increases the environmental cost.

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Ammonium Paratungstate Preparation -- Evaporation Crystallization

Evaporation crystallization method is the most commonly used method of preparation of ammonium paratungstate, this method of technology and equipment is simple, easy to large-scale, have a certain role in the purification at the same time,it has been favored by industrial production.

preparation of ammonium tropsanate image

When the ammonium tungstate solution heated, the ammonia concentration decreased, (NH4) 2WO4 solution concentration gradually increased, ammonium paratungstate crystallization, the reaction is:
12(NH4)2WO4==5(NH4)2O·12WO3·5H2O+14NH3↑+2H2O

In industrial production, the degree of evaporation crystallization is generally based on the amount of molybdenum allowed in the solution and the product. There are usually two ways of batch intermittent operation and continuous crystal operation.

The batch intermittent operation was carried out in a jacketed heated stirred tank, and a solution of (NH4) 2WO4 having a density of 1.16-1.28 g / cm3 was added to the reactor and stirred to boil the boiling ammonia.The reactor roof is generally installed with the vacuum system connected to the pipeline, discharged the ammonia to outside of the reactor in time to cooling and recovery. Solution pH value decreased to 7.0-7.7, separated out APT.

Field sampling measure mother liquid density is 1.06 1.02 g/cm3, namely stop heating and cooling for 0.5 hours,The material is discharged to a vacuum filter and filtered and washed. The resulting wet APT is dried at a temperature of 90 ° C to 120 ° C and then sieved to obtain an APT product.

The continuous crystallization operation is carried out in a continuous mold. Material liquid outer heater after heated to a certain temperature and then sent steam into the room, ammonia evaporation and gives some supersaturated solution in the steam, the supersaturated solution by the middle tube into the crystallization of chamber, with which contact with the crystal crystal, crystal send continuous filter to filter washing, part of the return to the original solution crystallization mother liquor mixed circulation, mixing part into the batch operations last reactor for secondary crystallization.

The discontinuous operation is simple and easy to recycle, but the distribution range of APT particle size is too large. On the contrary, the continuous crystallization method has the same composition and particle size. The process is continuous and the quality is stable, but the crystallization rate is not high, so it needs more time.

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Ammonium Paratungstate Preparation -- Freezing Crystallization Method

Ammonium paratungstate (APT) is an important part of tungsten smelting, whether it is using chemical precipitation method, ion exchange method or extraction method, they all have to through the process of ammonium trioxide to produce qualified APT. 

freezing crystallization method image

APT is an important tungsten intermediate products , the higher the puritythe greater the value, so APT preparation process is also the further purification of tungsten.

Freezing crystallization method is one of the most commonly used methods for the preparation of ammonium paratungstate, which is the use of liquid ammonia to freeze the APT, so called frozen crystals. 

The freeze crystallization method was carried out in a liquid nitrogen cooled vacuum drier, and the ammonium tungstate solution was poured into an enamel plate pre-filled with liquid nitrogen (the volume ratio of ammonium tungstate solution to liquid nitrogen was 1: 2), stirring it and then   crystallized water and APT at the same time, Along with enamel disc quickly moved to the vacuum dryer, removed the water and free ammonia distillation under vacuum conditions, leaving a dry white amorphous and loose with 11 crystal water of ammonium paratungstate.

Produced APT by freezing crystallization method, chemical purity and raw material liquid did not change, but the average particle size can be obtained in 0.6 to 1.3 microns of superfine powder of ammonium paratungstate, and composition of paricle size was balanced, and the distribution of various impurities or additives was uniform. So often use this method to making W - the composition such as Re, W - Cu composite powder evenly.

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2017年11月20日星期一

Ten Factors Affecting the Ammonium Paratungstate Crystallization(2)

Ammonium paratungstate (APT) is an important tungsten intermediate product, not only in the purity and process requirements, as well as crystal grain size and crystal distribution requirements.

Seemingly negligible some of the objective factors often play a key role in the final product often For these reasons the difference between the least, lost thousands of miles.

The production workshop of para-ammonium tungstate image

6. The impurities in the solution: As the solution P, As, Mo, Si and other impurities easily adsorbed on the crystal growth of the active point, hinder the crystal growth, but also makes the ammonium paratungstate grain thinning, make the quality of deterioration, and easy to enter the product during the evaporation crystallization process, affecting product quality, and even lead to product failure, so in the crystallization process, should take the control of crystallization rate, improve the concentration of NH4Cl in ammonium tungstate solution, stirring and washing agents and other methods, to achieve the goal of removing impurity.

7. pH value: The nucleation rate and crystal growth rate affected by the pH value, since raw crystal nucleus of pH control in 7.5-8.0 range, is beneficial to reduce the number of spontaneous nucleation and the formation rate, small amount of crystal nucleus can grow smoothly into larger particles; And made a narrow pH range is beneficial to uniform distribution of coarse grain of ammonium paratungstate, only the uniform distribution of particles can be evenly Karl fischer granularity, this performance is particularly obvious in neutralization.

8. Ammonium tungstate solution added: The end of the nucleation period after the addition of ammonium tungstate solution, can not change the particle size distribution conditions, to improve the crystallization of ammonium tungstate ammonium particle size and bulk density, but also to overcome the initial high tungsten concentration , the product size of the smaller defects in the higher equipment capacity, produce the good fluidity of the crude ammonium paraffin.

9. The end of crystallization of the liquor density: Evaporation of the end of the crystallization of the liquor density of ammonium paraquat have a certain impact. Under normal circumstances, the lower end of the crystallization of the liquor density, the higher the crystallization rate, the easier the formation of coarse particles, because the crystallization of a long time can lead to crystal nuclei have sufficient time to grow up; the other hand, the crystallization of the end of the liquor density are larger, the easier the formation of smaller particles. Therefore, on the premise of guarantee the quality of products, can reduce the liquid evaporation at the end of the corresponding density, increase the crystallization rate accordingly.

10. Vacuum degree: With the speed up of the evaporation rate and vacuum degree is reduced, and the increase of the crystal elutriation rate, resulting in a slight increase in the number of microcrystalline precipitation, and the particle size decreases.

In conclusion, the preparation of ammonium paratungstate (APT) is a systematic project with a lot of side details. Each factor has different effects on the preparation of ammonium paratungstate crystals. In most cases, in order to produce a certain physical properties of ammonium paratungstate products, it needs comprehensive control for the various factors.


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Ten Factors Affecting the Ammonium Paratungstate Crystallization(1)

Ammonium paratungstate (APT) is an important tungsten intermediate product, mainly white crystals, there are two kinds of flakes or needle-like, used in the manufacture of tungsten trioxide or blue tungsten oxide tungsten powder.

The quality of tungsten products depends largely on the chemical purity of APT, particle size and particle size distribution.

Crystallization of Ammonium Paratungstate image

APT quality standards from the domestic manufacturers, the process and chemical purity are almost the same, but the production of APT products vary widely, this is because APT is a system engineering, not only the purity and process requirements, as well as crystal grain size and crystal distribution requirements, seemingly insignificant on some of the objective factors often play a key role in the final product is often because of these reasons the difference between the least, lost thousands of miles.

There are lots of influence factors of ammonium tungstate, mainly include: the temperature of the solution, the degree of supersaturation, stirring speed, add seed, impurities, pH value, adding ammonium tungstate solution, crystallization time and crystallization liquor density, vacuum degree, etc.

1. The influence of temperature: The temperature is important factors influencing the particle size of ammonium paratungstate.When the solution too full degrees must be under low temperature, rate of crystal nucleus grow up slowly, and nucleation rate faster, so generally get fine grain;And crystallization under high temperature, due to the crystal nucleus to grow up quickly, and the crystal nucleus formation showed relatively slow, so generally get a coarse crystals.

2. The degree of supersaturation: Degree of supersaturation is the most important factors influencing the APT granularity.Because of the formation of crystal nucleus needs a minimum energy, the activation energy, in a certain temperature, the greater the degree of supersaturation, the smaller activation energy is, the faster speed of the formation of crystal nucleus. However, in the production, the production capacity is too small, the production capacity is too small; the degree of supersaturation is too large and the grain size is small, and the crystal quality is poor. In addition, due to the concentration of ammonium tungstate solution and other solution components Of the content are different, the supersaturation of the solution also has a direct impact, therefore, in order to determine the appropriate supersaturation is very important.

3. Evaporation rate and neutralization speed: Adopt evaporation crystallization or neutralize the legal APT, evaporation rate and had a great influence on the granularity of APT and speed, the greater the evaporation speed and neutralization, at the beginning of the crystal form of the greater the degree of supersaturation, the number of crystal nucleus formation, the resulting APT particle size is fine, apparent density is small.


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Ammonium Paratungstate Crystallization Mother Liquor Treatment--Conversion Method

From dressing industrial progress of history suggests that mineral processing reagents application significance is self-evident. 

Since its discovery in 1924 xanthate has the function of collecting sulfide ore, the development of the flotation industry started by leaps and bounds, the inundated mineral processing reagents has been invented and created with a steady stream.

Ammonium Paratungstate Crystallization Mother Liquor Treatment image

The crystallization crystallization method and the neutralization method produce the crystallization mother liquor in the preparation of APT. These mother liquor contain not only impurities but also some WO3.

In order to improve the total recovery of tungsten, the mother liquor is often recovered once again in the industry treatment, as to which method should be based on the previous process and the composition of the mother liquor to use, usually available alternative methods are conversion method, solution extraction and ion exchange method.

Conversion method is commonly used in the crystallization process of ammonium paratungstate crystallization mother liquor treatment, it is added to the crystallization of the mother liquor NaOH, turn tungsten into Na2WO4 solution, and then according to the mainstream process to determine the craft.

(NH4)2WO4+2NaOH==Na2WO4+2H2O+2NH3

The presence of tungsten in the mother liquor with polyacid and heteropoly acid can be converted to sodium tungstate, the solution after heating need to boil, volatilize the ammonia.

The main process for acid decomposition--ammonia crystallization process, the crystallization of the mother liquor by alkali conversion, should be concentrated to WO3 content of 150g / L, and then by the classical chemical method for precipitation, precipitation of artificial white tungsten, and then the artificial white tungsten and scheelite mixed into the mainstream craft for processing.

Mainstream program for classic precipitation purification craft or extraction craft, the crystal mother liquor after alkali into the crude sodium tungstate solution, can be added directly after purification in the recovery of tungsten.

Main process of ion exchange craft, and its crystallization mother liquor after transformation, no longer suitable for the original ion exchange craft, it needs to be deposited artificial scheelite classic precipitation or extraction.

In APT crystal mother liquor processing technology is more in our country at present, have their own characteristics, but cannot leave the essence of removing impurity and recycling. Reforming process is suitable for the classic craft, but with the improvement of tungsten smelting technology, classic technology has been gradually withdraw from the historical stage, so the process is more like a role of relay station.


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Wolframite and Scheelite Mixed Tungsten Ore Flotation (2)

Wolframite and scheelite mixed tungsten ore flotation is a worldwide difficult problem, because of the black and white tungsten composition structure is very different, conventional flotation method at room temperature and heating method is not ideal. Would there have a more effective way to realize whether black and white tungsten mixed flotation?

black and white mixed tungsten ore flotation image

Chairman MAO once said: “There is a way, it just hasn’t been found.” He also said: “Paths are made by men.” And actually it does. After many years of industry practice, our country's scholars found that the focus on black and white tungsten study is mixed flotation collector, the flotation is strong while the collector is strong, scholars use the collector as the breakthrough point, make many light avenues.

In 70s and 90s, Chinese scholars use 731 + 733 combination of black and white mixed tungsten ore flotation collector, 731 and 733 to mix ratio of 10:1, the collector has the advantage of source is easy to obtain, the disadvantage is that not good flotation wolframite, scheelite flotation recovery of 0.010 below also is not high, metal erosion is more serious, and the production of rough concentrate grade is low.

In the 90s, mining and metallurgy research institute of Beijing through a lot of experimental research, found a natural pH pulp black tungsten method under the condition of flotation, this term is known as the CF method. Reagent regime of the method is: use a small amount of sodium silicate do adjusting agent, lead nitrate as activator, with CF (the nitrobenzene hydroxylamine ammonium salt) as collector, a tiny amount of emulsified oil and oleic acid as foaming agent, flotation pulp pH value of 7-9 black and white tungsten mixed pulp.

To CF with lime and caustic soda method of small test comparison, the results showed that the index of CF method obviously is excellent, concentrate grade slightly higher, the recovery is 10% higher than the other two methods.

In recent years, Guangzhou non-ferrous metal research institute in the same points under the guidance of the principle of heterogeneous select the high efficient tungsten sequestration collector benzene armour hydroxyl oxime acid, it is an effective collector of fine wolframite. Use the benzene armour hydroxyl oxime acid and fatty acid such as collector, oxidized paraffin soap oxidized ore collector combination, in both strong selectivity of benzene armour hydroxyl oxime acid at the same time, also improve the collecting ability of the agent, this kind of combination is called the GY series reagents. The arrival of GY combination reagent, makes the fine grained recycling effectively, and from now on, black and white mixed tungsten ore flotation no longer have to struggle, it really reduced the cost, to achieve the efficiency of mining. Fujian one tungsten mines with GY series reagents recycle mixed black and white tungsten ore, eventually made the mines getting out of the woods, made up the deficits and get surpluses, became the pillar of the economy.


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Wolframite and Scheelite Mixed Tungsten Ore Flotation (1)

Wolframite and scheelite are different with the same name, there are all “w” but their body structure are not the same, so their beneficiation method is different, black tungsten gravity commonly used the separation method, scheelite commonly used flotation process.

Black and White Mixed Tungsten Ore Flotation image

After years of development, our country each has a solid industrial foundation of beneficiation technology in wolframite and scheelite tungsten ore flotation. From a single scheelite recovery of scheelite in bed or recovery of wolframite from single black tungsten deposit is relatively easy. But why there is a certain type of skarn deposits made mistake like, they try to make the black and white tungsten together under the same roof, so the deposit is called "black and white mixed tungsten deposit.

Mixed black and white tungsten ore flotation is a worldwide difficult problem, in this type of ore deposits, the black and white tungsten are in fine grained disseminated separately symbiosis in the strata, although there are all tungsten, they have always not buying it from one another, they go their own way. The difficulty of black and white mixed tungsten ore mixed is that the inclusion of black tungsten, In Jiangxi quartzite mines, black tungsten can be solved with gravity separation, magnetic separation, but when it comes to in the skarn deposits, it also learn pee-a-boo from scheelite, escapes from the gravity separation method. Of course the most embarrassing thing is that the suspect relationship, in the process of flotation of wolframite and scheelite natural flotability difference is bigger, often the flotability of scheelite is superior to the black tungsten, tungsten oxide ore collector line of collecting ability is stronger, collecting of wolframite ability is weaker; In addition, wolframite and scheelite the best flotation pH interval does not agree, the best flotation pH interval of scheelite is relatively narrow, between 7-9.

Wolframite the best flotation pH interval often swings between 5-10. And wolframite it brittle than flotation technology, only after a minor in the coarse grinding, into the coarse grain of spiral classifier wolframite precipitation will be priority major, with the sand return to the mill grinding again, until the grain will overflow into the sorting operation. It caused most of the classification system of wolframite granularity are belong to fine grain or even micro-fine particle, general flotation reagents are difficult to catch.

In the past, wolframite and scheelite separation method of mixed flotation concentrate with room temperature and heating method of two kinds: normal temperature method is in a large amount of sodium silicate for rough concentrate (60 ~ 90 k young) under normal temperature stirring, to curb the fluorite and calcite, quartz and other gangue minerals, and most of wolframite is restrained, white tungsten concentrate were obtained through the multiple selection, room temperature method is more difficult to obtain high grade tungsten concentrate containing WO365 % above, and the dosage of sodium silicate is more large consumption. Heating method only need to add a relatively small amounts of sodium silicate, and then heated to 90 ℃ or so, thermal agitation for an hour, this process makes the gangue minerals and wolframite surface adsorption of collector stripping, and strong inhibition by sodium silicate, and scheelite collector can still on the surface of the solid adsorption, thus containing WO365 % above the high grade can be obtained by flotation of scheelite concentrate, cleaner tailings need to recycle of black tungsten, the traditional process is: the black tungsten content is less, usually with magnetic separation enrichment,and shaking table selection for black tungsten concentrate, the black tungsten content is higher, can be directly with the table selected black tungsten concentration, The process of the disadvantage is the microgranular wolframite erosion, recycle like go through the motions, is better than nothing, only so many of the early black and white tungsten mixed mining waste is serious, the efficiency is low. There would have a more effective way to realize whether black and white tungsten mixed flotation?


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Combination Collector Mechanism--Chelating Effect

In the flotation system, two or more collectors are used in combination, and by combining the collector and producing synergistic effects, such tungsten ore flotation collector is known as combination collector in practice. It has been proved that many combination collector has better and more effective flotation results than the use of a single collector, and there are divergent views on the causes.

For the study of the mechanism of the combination collector, there are scholars think that the combination collector also has a significant chelating effect, it refers to the combination collector and mineral surface of the metal between the combination collector metal's special affinity caused by the real chemical reaction. The result of this reaction is the formation of insoluble, stable metal chelate. 



The scholars of South China University used the quantum chemistry ab initio algorithm to calculate the molecular model of benzohydroxamic acid and benzyloxamic acid. The benzohydroxamic acid-based mixed collector BH was used to study the tungsten ore in Shizhuyuan polymetallic ore Test and in the wolframite and scheelite tungsten mixed ore flotation research made a breakthrough. The experimental results show that the BH combination collector has a good catching effect on scheelite and wolframite. The main reason is the chelating effect of BH combination because the benzohydroxamic acid molecule is a planar molecule and benzene Methionine is a nonplanar molecule, both of which can coexist and that the methacryloxamic acid is more stable than benzohydroxamic acid. When the benzohydroxamic acid and benzyloxamic acid and mineral surface of the metal ions chelate, and metal ions easily formed O, O five ring chelate, rather than O, N quaternary ring chelate. Compared with acetohydroxamic acid (hydroxamic acid), benzohydroxamic acid (benzyloxamic acid) and mineral electrostatic effect becomes smaller, the ability to match the key to reduce the ability to accept the formation of electronic feedback bond, Hydroxamic acid (benzyloxamic acid) selectivity increased.


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2017年10月23日星期一

Tungsten Flotation Inhibitor—Modified Sodium Silicate

Inhibitor as well as known retarder, it can retardant or reduce the chemical reaction speed of the material, the function is the same as the negative catalyst. Tungsten flotation inhibitor can be divided into two types: Organic inhibitor and inorganic inhibitor. 

modified sodium silicate image

The most commonly used for modified sodium silicate inorganic inhibitors, metal ion+sodium silicate, ammonium salt, sodium silicate, sodium silicofluoride, pyrophosphate, etc. They each have their own strong points. Here introduces a kind of inorganic inhibitors tungsten flotation-modified sodium silicate.

Modified sodium silicate is  through the water glass for modification, acidification or the use of other agents in combination with the way to achieve the water glass can improve the inhibitory effect of calcium-containing gangue minerals purposes. Modified sodium silicate is the activator after decomposition of sodium silicate, it can produce a large number of single molecule silicate, the single molecule has a high activity, and it can adsorption on the purpose mineral by selective, forming strong hydrophilic layer, so as to achieve inhibitory effect.

Modified sodium silicate is divided into two categories, physical modification and chemical modification. Physical modified sodium silicate by magnetic field, ultrasonic, high-frequency or heat energy into the system, make the polysilicic acid molecules to homogenization, thus eliminating its aging phenomenon; Chemical modified sodium silicate is fused sodium silicate with other chemicals, some potions itself does not inhibit gangue mineral, but after adding water glass, inhibition effect was like the icing on the cake, has reached the unexpected enhancement.

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Tungsten Flotation Collector—Combination Collector

Commonly used tungsten flotation collector can be divided into anionic collector, cationic collector, amphoteric collector and nonpolar collector and complexing or chelating collector dosage form five categories, these collector is known as the fatty acid, phosphoric acid, chelation, amine, petroleum and so on.

Tungsten Flotation Collector—Combination Type of Collector image

Full of beautiful collectors are always dazzling, objectively speaking, every collector has different strengths and weakness, for example, the fatty acid collector has strong ability of flotation but the ability of selectivity is poor. The selectivity of chelating collector is good but it is expensive. The selectivity of phosphoric acid, sulfonic acid, amine are good but the flotation ability is a bit poor and there exists environmental pollution. In great abundance of choices, it says suitable is the best, but it is hard to choose the right thing in one in a million, after continuously experiment again and again, people found that is also can go with “mix and match” style based on lessons drawn from others’ mistakes, and the result is quite good.

Theoretically, in the flotation system of two or more than two collector can exist mutual effect, can produce synergies in the flotation process, play a better role, the “synergistic effect” mechanism of drug combination is more complex, it can be roughly summed up as a total adsorption mechanism, the aojiang mechanism, charge compensation mechanism, function complement mechanism, etc. Practice has proved that most selectivity of the sequestration collectors and amphoteric collectors are better than fatty acids, but collecting ability is weak, therefore use a variety of types of mixed collector to add, the synergistic effect can happen in tungsten flotation, not only can improve the flotation effect of drugs, but also can reduce the dosage of the drug. Of course “mix and match” is not “faulty”, after all, they are all chemicals.

Successful “mix and match” is never happen overnight, the group of “mix and match’ is selected by rigorous selection theory and experiment practices. Which are frequently used in current industrial mix combinations are: combination of oleic acid and kerosene, sodium oleic acid and oleic acid ammonium, petroleum sulfonic acid and sodium oleate combination, fatty acids combined with six fluorine butadiene, hydroxylamine acid and alkyl sulfonate, CKY combined with sodium oleate, benzene armour hydroxyl oxime acid and oleic acid combination and so on. There is no doubt that the application of combination types of collector for various mineral processing enterprise promoted economic and environmental benefits are indisputable facts.

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