Effective parameters on generation of nanobubbles by cavitation method for froth flotation applications
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Department of Mining and Metallurgical Engineering, Amirkabir University of Technology (Tehran Polytechnics), Tehran, Iran.
School of Mining Engineering, University of Tehran, Tehran, Iran
Bahram Rezai   

Department of Mining and Metallurgical Engineering, Amirkabir University of Technology (Tehran Polytechnics), Tehran, Iran., Floor 7, Department of Mining and metallurgical engineering, Amirkabir University of Technology (Teh, 15875-4413 Tehran, Iran
Publication date: 2017-04-22
Physicochem. Probl. Miner. Process. 2017;53(2):920–942
The significant recovery increase in flotation of fine particles using nanobubbles has been one of the major topics in flotation science in recent years. Fine bubbles have an important effect on gas hold-up, which is necessary in froth flotation of minerals based on the process industries. At a given gas hold-up, using finer bubbles can reduce frother consumption. An exclusive nanobubble generation system has been developed in Iran Mineral Processing Research Center (IMPRC) to evaluate the effect of nanobubbles on the froth flotation performance. This device, which enhanced venturi tubes, works according to cavitation phenomena. The venturi tube is the most widely used hydrodynamic cavitation device, in which liquid flow increases in the conical convergent zone of the tube due to the thin diameter. The liquid in the cylindrical throat is higher in a flow velocity and lower in a pressure than the liquid in the entrance cylinder, which results in cavitation. In this research work, various factors such as the frother type and dosage, pH, compressed air flow, pressure in cavitation nozzle, gas types, temperature and venturi tube internal diameter were studied. For this purpose, a five-level central composite experimental design was used to check the influence of four important parameters on the median size and volume of nanobubbles. Online measurement of the bubbles size was implemented by a laser particle size analyzer (LPSA), according to standard BS ISO 13320-09. Due to the above parameters and obtained responses, the analysis of variance (ANOVA) was conducted with a suitable model to optimize the conditions, with the aim of minimizing the size of air bubbles. The optimal conditions were: frother (MIBC) dosage of 75.8 mg/dm3, air flow rate of 0.28 dm3/min, pressure of 324 kPa and pH of 9.5. The median bubble size d50 was equal to 203 nm. To validate the results, a test under optimum conditions was performed and the obtained results indicated that there was a good fit at the confidence interval of 95% and reflected the repeatability of the process.