Kinetic study of Ni(II) removal using ion flotation: Effect of chemical interactions

In this kinetic study, the separation mechanism and chemical interactions of Ni(II) ion removal from synthetic wastewater were evaluated by ion flotation. The influence of effective factors such as pH, collector concentration, ionic strength, activity coefficient, foreign salts, and gas type were also evaluated on the kinetics of Ni(II) ion removal and water removal during the process. By increasing pH, the Ni(II) removal rate increased, in which foam fractionation occurred at pH levels of 3, 5.5, and 8 and ion flotation at a pH level of 9.7. The difference between foam fractionation and ion flotation is related to the flotation of a soluble or insoluble complex of the ion-collector. The kinetic study was also used to determine the separation mechanism. The order of Ni(Il) foam fractionation was two, while the order of Ni(II) ion flotation was one. The Ni(II) removal rate was faster than the water removal rate, which indicated that Ni(II) ion removal was carried out by true flotation. The effect of chemical interactions on the characterization of the sublate (insoluble complexes formed in the scum layer) were studied using scanning electron microscopy coupled with energy dispersive X-ray (SEM/EDX) spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The results showed that the chemical conditions have an important effect on the Ni(II) ion flotation efficiency.