This is an innovative a method and electrochemical cell designed to recover yttrium oxide from phosphor. The process begins with leaching a phosphor sample using a specific acid in a controlled quantity under predefined conditions to produce a leach liquor. This leach liquor is then diluted with deionized water (DI water) to form an electrolyte solution containing a yttrium compound. Next, the electrolyte solution is utilized in an electrochemical cell for electrodeposition, depositing yttrium hydroxide onto a cathodic stainless-steel substrate. The yttrium hydroxide forms through a reaction between the yttrium compound and the cathodic substrate. Subsequently, the yttrium hydroxide undergoes calcination at a predetermined temperature and for a specified duration to yield yttrium oxide.
Figure 1. SEM/EDS micrographs of waste phosphor powder along with the qualitative analysis of yttrium europium oxide
Rare earth elements (REE) can be extracted from recycled waste fluorescent lamp (WFL) phosphors. Traditionally, REEs are sourced through mining natural deposits or ion-adsorption ores, which are complex methods high infrastructure requirements. Due to the substantial rise in demand and their large applications, these conventional extraction methods may fall short.
- This innovative technology does not require treatment at higher temperature and does not use expensive molten salts.
- This method uses a combination of both hydrometallurgical and electrometallurgical approaches. It uses hydrochloric acid for the effluent of red phosphor in solution and employs leach liquor as electrolytic solution for the recovery of yttrium using cathodic electrodeposition.
- It is economically feasible for the large-scale production of pure Y2O3 from WFL phosphor.
- The recovered Y2O3 has purity > 90%, which can be reused for several applications.
The electrochemical cell includes a cathode substrate made of stainless steel, with specified dimensions: a length ranging from 50 mm to 1.0 m, a width ranging from 25 mm to 0.5 m, and a thickness ranging from 0.01 mm to 1.0 mm. Surrounding the cathode substrate are at least two parallel counter electrodes, each consisting of a graphite electrode with a length between 60 mm and 1 m, and a width between 3 mm and 30 mm. The cell also contains an electrolyte solution containing yttrium chloride.
The components of the invention have been validated in lab environment. Purity of the yttrium oxide recovered through this method was shown to lie in a range of 85% to 95%.
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The invention has environmental benefits as it recycles WFL phosphors to give REEs, which can be used in various places. The recycled WFL is also prevented from going to landfill and causing soil pollution.
WFL Phosphor is recycled to recover REE’s which have application in many domains. The REE’s recovered from the defined method can be used in various industries such as electronics, defense and aerospace, metallurgical, pharmaceutical, chemical and so on.
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