To highlight the deactivation mechanisms encountered by minerals impurities from biodiesel, the effects caused by Na, P or (Na + P) additions were studied over a model Cu-FER catalyst. Na, P or (Na + P) were added by wet impregnation in water in a wide concentration range up to 2 wt-%. The catalytic behaviors were evaluated by NH3/NO oxidation and standard/fast NH3-SCR reactions. In addition, a combination of several characterization techniques (ICP AES, N-2 adsorption/desorption, XRD, NH3-TPD, NO adsorption monitored by FTIR and H-2-TPR) was applied to provide useful information regarding the deactivation mechanism caused by the minerals addition. Sodium and phosphorus interacted differently with the Cu-FER catalyst. Na addition induced a loss of Bronsted acid sites and a back-exchange of Cu2+ with Na,+ with formation of external CuO species, thus favoring the oxidation of NO and NH3. After phosphorus addition, the exchanged Cu2+ species remained moderately affected, but direct interactions with copper were evidenced which were primarily responsible for catalyst deactivation toward the oxidation reactions. After equimolar addition of phosphorus and sodium, both Na and P effects were observed. For the NH3-SCR process, the ammonia adsorption ability, which depends on both acidity and copper units, appeared the main key parameter driving the catalytic activity at low temperature (T <= 250 degrees C). Phosphorus appeared to be the major responsible for catalyst deactivation after (Na + P) co-poisoning.