An experimental study on size distribution and zeta potential of bulk cavitation nanobubbles

Nanobubble flotation technology is an important research topic in the field of fine mineral particle separation. The basic characteristics of nanobubbles, including their size, concentration, surface zeta potential, and stability have a significant impact on the nanobubble flotation performance. In this paper, bulk nanobubbles generated based on the principle of hydrodynamic cavitation were investigated to determine the effects of different parameters (e.g., surfactant (frother) dosage, air flow, air pressure, liquid flow rate, and solution pH value) on their size distribution and zeta potential, as measured using a nanoparticle analyzer. The results demonstrated that the nanobubble size decreased with increasing pH value, surfactant concentration, and cavitation-tube liquid flow rate but increased with increasing air pressure and increasing air flow rate. The magnitude of the negative surface charge of the nanobubbles was positively correlated with the pH value, and a certain relationship was observed between the zeta potential of the nanobubbles and their size. The structural parameters of the cavitation tube also strongly affected the characteristics of the nanobubbles. The results of this study offer certain guidance for optimizing the nanobubble flotation technology.