Spent fluidized cracking catalyst (FCC) - A potential adsorbent for heavy metals

Spent fluidized cracking catalyst (FCC) can be utilized as an adsorbent for heavy metals from wastewater. The material is available in huge amount from refineries as a solid waste. This waste is sent to the landfill, once discarded. The potential of spent FCC to immobilize heavy metals from wastewater is explored during this study. The phenomenon considered is adsorption and ion-exchange. FCC is a zeolite material with alumina matrix and clay filler. The catalyst is contaminated by deposition of very small amount of heavy metals such as nickel and vanadium. Thus, it is rejected from the process as a waste, though most of its adsorption capacity remains; can be utilized for heavy metals uptake from wastewater. In this study, the heavy metal tested is copper. Batch experiments are performed to measure the capacity with pH in acidic range. The maximum capacity is found to be ~ 4.7 mg/g and occurs at pH near 6. The capacity increases with pH till above value and then decreases. Ion-exchange seems playing major role in heavy metals uptake; although other adsorption mechanisms such as pore filling, complex formation, and precipitate adsorption cannot be totally ruled out. The study provides an insight about the utilization of spent FCC material in wastewater treatment.