Ion Exchange to recover molybdenum from spent SCR and remove arsenic

In the modern industrial society, the nitrogen oxides emitted by the factory will have great impact on the environment, including human lung disease, rain acidification. Selective catalytic reduction(SCR) can turn nitrogen oxides into harmless nitrogen, it is also currently the industry’s most commonly used denitrification method. In which SCR contains tungsten, molybdenum and vanadium and other heavy metals such as arsenic. The ashes in the blast furnace contain arsenic that will adsorb on SCR when passing through the SCR catalyst. This study will find the best pH value and metal concentration and bed volume amount, and finally add magnesium chloride to make the final product which is molybdate without arsenic. Therefore, this study demonstrates the combination of the processes to recover molybdenum from spent SCR catalysts. Those processes are alkali roasting, leaching and ion exchange. The leaching rate of molybdenum, vanadium, and arsenic is 98%, 99% and 95%, respectively. IRA900Cl resin was chosen because of its affinity to molybdenum. The affinity of IRA900Cl resin under the different metal ions in the leaching solution: Mo >>V> P> As >>Si, Al. After the resin absorption, the recovery of molybdenum over 99.99%.Ammonium salt was chosen to make molybdenum desorbed from resin; the recovery of Molybdenum is close to 100% under series ionic exchange column. Arsenic removal was used magnesium salt to precipitate arsenic. Excess magnesium salt was followed by cationic resin to reach 100% Mg recovery rate without losing any Mo.