Due to denitration agents take 30%~50% the whole investment of denitration equipment in the system, besides the main component V₂O₅ is of highly toxic which will cause environmental pollution and poison to human body. So, it will create great economic and environmental benefits by comprehensive recycling waste catalyst. A method for recycling tungsten, vanadium and titanium from waste SCR catalyst is put forward in this paper, steps are as follows:



1. SCR waste catalyst pretreatment, high temperature and pressure leaching out
1) Crushing and grinding the waste catalysts, then send them to NaOH solution which the concentration is 200~700g/L, and then leaching out at high temperature (130~220℃), high pressure (0.3~ I.2MPa) for I~6 hours, get filtrate and residue;
Remarks: residue can be used as the material of Rutile Titanium Dioxide;
2) Add hydrochloric acid to adjust the pH value to 0.5~I.5, and heated to 90~100℃ to make Na₄TiO₄ reacted to H₄TiO₄, then filter for getting filtrate and residue;
Remarks: ①. Filtrate and washed wastewater are joined into reuse process of wastewater;
②. The residue after washing is calcined at the temperature of 800~900℃ for 2-4 hours to get Rutile Titanium Dioxide.
2. Adjust pH by adding hydrochloric acid to remove impurities
Add hydrochloric acid into leaching solution which is got from step 1 to adjust pH value to 10~11, then add MgCl2 for removing impurity; concentrate and again add hydrochloric acid to adjust pH value to 9~10, and then precipitate WO₄^2- and VO^3- ions, separate to obtain filtrate and filter residue, the filter join into reuse process of wastewater.