Homogeneous crystallization of nickel as Ni3S4 in a fluidized bed reactor with supersaturation control

This study investigates the recovery of nickel sulfide (NiS) using fluidized bed homogeneous crystallization (FBHC), emphasizing the process from nucleation to crystallization. Sludge production in conventional chemical precipitation becomes a drawback in treating wastewater economically and efficiently. FBHC offers a promising alternative by minimizing sludge generation. The study examines various operational parameters, including hydraulic retention times (HRT), reflux ratio (R), initial nickel concentration, and static bed height (SBH), to optimize NiS recovery. Results show that FBHC achieves high total removal efficiency (TR) and crystallization ratio (CR), under the optimum condition of HRT =15 min, R = 8.3, initial nickel concentration =147 mg/L, and SBH = 35 cm. The agglomeration of Ni(OH)2 was found to be crucial for the crystal growth during the surface oxidation of Ni3S4. This technological approach to wastewater treatment offers highly efficient heavy metal removal from wastewater.