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.