Emulsion Liquid Membrane and APT Production

The concept of emulsion liquid membrane is proposed by N.N.Li in 1968, and it has attracted researchers from many countries for APT production. Because it simulates the activity of migration of biofilms on the migration mechanism, it enables materials highly enriched against the concentration difference. It is the combination of extraction and back-extraction process carried out in a system at the same time, the reaction takes place on the surface area of the extremely thin film interface, and there is carrier on the membrane, so its kinetic advantages are much more than the reaction takes places in solution, also the mass transfer rate, efficiency and selectivity than the extraction process.

Currently the main technology key of emulsion liquid membrane is the stability and membrane rupture technology. The requirements are different for the stability of the film in the film extraction and rupture stage, the former one requires high film stability while the latter one requires low stability. Currently it’s difficult to control the film stability and longevity. Membrane rupture technology is related to reuse and recycling of organic phase, which directly affect the economic effects of liquid film method, and different formulations of liquid membrane result in different effects of rupture, therefore the rupture technology also needs to be tested. For the study of surfactant and carriers, it’s also directly affect the technical and economic effects of liquid film. In addition, in the industrial wastewater treatment, since the dissolution of membrane components may cause secondary pollution, these problems can be solved in the research and development of the film.

Detinning Process of APT Production- Precipitation Method

Precipitation method in APT production is a common method of separation science. As the tin exists as precipitate forms in the weakly acidic, neutral, weakly alkaline environment, people take a variety of precipitation methods, such as hydrolysis precipitation, tin sulfide precipitation to remove tin of the tungsten solution.

Hydrolysis precipitation method
This is a classic method remove tin. Its basic principle is tin in solution can be hydrolyzed into tin hydroxide precipitate at a pH of about 2 to 11 (depending on the concentration of tin in the solution) to separate tungsten. The main reaction is:
SnO3 2-+3H2O= Sn(OH)4↓+20H-.

Specific operating conditions: add dilute acid(typically sulfuric acid) to sodium tungstate solution (pH is about 14), adjust pH of the solution to 9 to 10, stirring for 10 ~ 15 min, at room temperature (in the case of boiling , the advantage is not very obvious), to stand for aging. The longer the standing time, the higher the tin hydrolysis precipitation rate. It’s believed in the literature that it needs to stand for 96 h.

Hydrolysis detinning rate rises with the tin mass concentration of solution increased. However, when hydrolysing detinning, and the solution is often turbid, the precipitation is difficult to cake filter. Easy to form a tin-containing hydrolysis solution lower gum, gum nucleosome its low concentration, dispersion and strong, easy reunion. It is also above the longer the standing time, the higher the rate of hydrolysis precipitation in addition to tin reasons. Production, the use of tin content in the concentrate within the range of 0.03% to 0.2%, tin in solution concentration of 0.0012 ~ 0.033g / L, therefore, in addition to use of hydrolytic precipitation when tin is difficult to obtain the desired results. Moreover, the operation of acid sodium tungstate were to spend a lot of acid, and the introduction of a large number of impurities anion, seriously affecting the subsequent ion exchange process, difficult to apply to the current tungsten metallurgy most advanced "tungsten concentrate decompose an ion exchange an evaporative crystallization "technology.

Detinning Process of APT Production- Ion Exchange Method

Ion exchange is an exchange of ions between two electrolytes or between an electrolyte solution and a complex. In most cases the term is used to denote the processes of purification, separation, and decontamination of aqueous and other ion-containing solutions with solid polymeric or mineralic 'ion exchangers'.

Typical ion exchangers are ion exchange resins (functionalized porous or gel polymer), zeolites, montmorillonite, clay, and soil humus. Ion exchangers are either cation exchangers that exchange positively charged ions (cations) or anion exchangers that exchange negatively charged ions (anions). There are also amphoteric exchangers that are able to exchange both cations and anions simultaneously. However, the simultaneous exchange of cations and anions can be more efficiently performed in mixed beds that contain a mixture of anion and cation exchange resins, or passing the treated solution through several different ion exchange materials.

In the ion exchange method, the affinity of tin acid radical to resin is far less than the affinity of tungstate to resin in the solution, remove rate of tin in adsorption stage is about 90%, but also to remove 80% to 90% tin when rinsing, so the total remove rate of tin is 98% to 99%.

Although the ion exchange capacity in addition to tin acid radical is strong, there are still a small amount of tin acid radical adsorbed by resin, and during the desorption, some goes into the ammonium tungstate solution with tungsten. If the ammonium tungstate solution crystallize directly without treatment, tin will hydrolyze and separate out and enters the APT product, it is easy to make tin content exceeded in the products. Therefore, it has been studied all this time that how to remove the depth of tin acid radicals by ion exchange methods in an attempt to tap the potential in addition to tin of ion-exchange method.

Preparing AMT from APT

A process for preparing ammonium metatungstate (AMT) using ammonium paratungstate/APT as raw material comprising: leaching wet ammonium paratungstate/APT with nitrite acid to obtain a dilute solution of ammonium metatungstate; concentrating the dilute solution of ammonium metatungstate /AMT to be a concentrated solution of ammonium metatungstate/AMT; and spray-drying the concentrated solution of ammonium metatungstate/AMT to obtain powder of ammonium metatungstate/AMT.

You could visit our site :www.tungsten-powder.com to know about AMT more.

about ammonium paratungstate (APT)

Ammonium paratungstate, (APT) is a white crystalline salt of ammonium and tungsten.

APT is produced by separating tungsten from its ore. Once the ammonium paratungstate is prepared, it is heated to its decomposition temperature, 600 °C. Left over is WO₃, tungsten oxide. At that point, the oxide is heated in an atmosphere of hydrogen, reducing the tungsten to powder, leaving behind water vapor. From there, the tungsten metal powder can be fused into any number of things, from wire to bars to other shapes.

The WO3 content of APT manufactured and supplied by Chinatungsten Online is over 88.5%.

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What does APT stand for?

What does APT stand for?

In tungsten industry, APT is stand for ammonium paratungstate, whose chemical formula is 5(NH4)2O.12WO3.xH2O. APT is produced separating tungsten from its ore. APT is heated to its decomposition temperature, 600 °C. Left over is WO3, called tungsten trioxide. Tungsten oxide is heated in an atmosphere of hydrogen, reducing the tungsten to elemental powder--tungsten powder. The tungsten powder can be fused into any number of things, from wire to rods to other shapes.

Visiting www.tungsten-powder.com you could get more information.