Avaliação do uso de catalisador exaurido de craqueamento catalítico fluido (FCC) para redução do teor de amônia em efluentes hídricos

Abstract

The contribution of contaminants is one of the causes that contribute most to the degradation of the quality of the surface water bodies, either due to lack of basic sanitation, the launching of industrial wastewater and agricultural activities. ammonia nitrogen (ammonia) is one of the pollutants that cause concern for its abundance and presence in almost all types of water use. Otherwise, the petroleum industry generates in its production process considerable annual quantities of a residue called the catalytic exhaust of fluid catalytic cracking (FCC), which has in its composition zeolite, a mineral that has, among other properties, adsorptive capacity of cations. In this way, the present work sought to evaluate the possibility of using the exhausted FCC catalyst as an adsorbent in a possible step of polishing wastewater for the removal of ammonia nitrogen. The adsorption isotherm obtained in bench scale test using synthetic effluent sample showed unfavorable profile. The application of this residue as adsorbent material to remove ammoniacal nitrogen presented limited efficiency, obtaining as better adsorption capacity the value of 4.71 mg/g, significantly lower than best results already obtained according to the technical literature consulted. The previous washing of the catalyst did not represent an increase of efficiency to the adsorption process, but it reduced the impact of the drop of the pH value observed at the end of the experiments carried out without previous washing. Possible pre-existing contaminants in the catalyst composition were not detected in treated effluent at values that could represent legal disqualification, but the historical data showed heterogeneous values, suggesting the need to individually evaluate each lot to be studied. Thus, the use of exhaust catalyst in the removal of ammonia nitrogen in water effluents presents limitations in efficiency, logistic (inventory) and operational (prior conditioning) aspects.