Optimization and separation mechanism of Ni(II) removal from synthetic wastewater using response surface method

In this study, the optimization of Ni(II) removal and water recovery in the ion flotation were evaluated using the response surface method. The Ni(II) removal and water recovery were modeled and described as a function of the main variables including pH, collector concentration, and frother concentration. Seventeen experiments were performed as a central composite design by 2³ full factorial design. The results showed that the pH and collector concentration have a significant effect on the Ni(II) removal and water recovery during the process in which they are increased with increasing the pH and collector concentration. The separation mechanism changed with changes in the pH solution, in which foam fractionation performed at pH levels of 1.3, 3, 5.5, and 8 and ion flotation at a pH of 9.7. The Ni(II) removal in the foam fractionation process increased from 11.5 to 85.5% with increasing pH from 1.3 to 5.5 and then decreased to 76.92% at a pH of 8. Subsequently, the Ni(II) removal increased to 100% at a pH of 9.7 in which the ion flotation process was performed. The results indicate that the ion flotation efficiency was more than foam fractionation efficiency for Ni(II) removal from the solution.