Integrating bi-pH operation to enhance Ni2+removal and recovery in fluidized-bed non-seeded granulation process

Anthropogenic activities and industrial processes generate large amounts of nickel in effluent, posing a threat to public and ecological health. Several processes have been developed to remove nickel and adhere to environ-mental limits. The fluidized-bed non-seeded granulation process has proven effective in removing and recovering metals including nickel. In this study, nickel was precipitated using phosphate while investigating bi-pH oper-ation. The study compared single-pH and bi-pH and found that bi-pH was better. The effects of molar ratio ([Ni2+]:[PO43-]), initial nickel concentration, copper ion concentrations, and other co-existing chemical com-pounds were then investigated under bi-pH operation. The optimal conditions were observed at bi-pH 7.5 and 9.0, molar ratio of 1:1.3, and 300 mg/L initial nickel concentration. The results showed that bi-pH improved the granulation process by generating heterogeneous granulation through observed bi-layers. The effects of molar ratio and initial nickel concentrations were attributed to changes in the predominant saturation condition, dictating primary and secondary nucleation. Co-existing compounds had no significant effect on total nickel removal but reduced granulation efficiency due to nickel complexation, ionic competition, and precipitate dissolution.

Automated summary

Anthropogenic activities and industrial processes release large amounts of nickel into the environment, leading to potential risks to public and ecological health. A method called fluidized-bed non-seeded granulation process has been found effective in removing and recovering metals, including nickel. This study focused on precipitating nickel using phosphate and investigated the effects of bi-pH operation, molar ratio, initial nickel concentration, and co-existing chemical compounds. The results showed that bi-pH operation improved the granulation process by generating heterogeneous granulation, while co-existing compounds reduced granulation efficiency due to nickel complexation, ionic competition, and precipitate dissolution.