Subcritical Water as a Solvent for Extraction of Nickel and Aluminum Ions from Reforming Spent Catalysts

Abstract

Spent catalysts are categorized as hazardous waste because they still contain heavy metal elements. It indicates that spent catalysts need to be treated before they discharge to the environment. In this study, spent catalysts treatment was done using subcritical water extraction method. The extraction process was conducted by varying temperature and extraction times. Temperature was varied at 100-250°C, whereas time extraction was varied at 15-45 minutes. Operating pressure and particle size were kept at 70 bars and-60+70 mesh, respectively. The content of aluminum (III) (Al3+) ions and nickel (II) (Ni2+) ions were analyzed using UV-vis spectrophotometer. The experimental results showed that the highest content of both metal ions was achieved at 250°C and 45 minutes. The content of extracted Al3+ ions and extracted Ni2+ ions at those conditions was 623.39 and 35.03 ppm, respectively.