Ultrasonic Effects on Precipitation and Froth Flotation
Industrial waste waters are often heavily acidified due to the excessive use of sulphuric acid. Acidified wastewater containing heavy metals are commonly treated by chemical precipitation after coagulation and flocculation. Ultrasonic conditioning before the flotation resulted in a significant improved flocculation of the zinc hydroxide formed during precipitation. Furthermore, sonification also promoted the mechanical removal of the zinc hydroxide from the surfaces of the gypsum particles.
Froth Flotation and Ultrasonic Conditioning
Fine particles present special problems in ﬂotation. Recoveries often drop below a certain critical particle size. Early work by Gaudin and coworkers (1931) showed that the recoveries of sulﬁde minerals of copper. zinc and lead are maximum, > 95% in the particle size range of 10-100 µm, but below 10 µm the recoveries drop to the range 70-85%. Trahar and Warren (1976) have summarized the observed size ranges of maximum recovery for many commonly ﬂoated minerals under normal experimental conditions. The size ranges in many cases have been extended by altering the conditions and judicious manipulation of chemical and physical parameters.
Sonification is a successful pre-treatment for the removal of heavy metals such as iron, zinc and copper from acid mining drainages and other metal effluents.
Power ultrasound is widely used to remove impurities from minerals. Studies have shown that sonication promotes the zinc removal from hydroxide precipitates, as well as the separation of zinc hydroxide and gypsum precipitates by dissolved air flotation. Using carboxy-methyl cellulose (CMC) as a depressor for calcium oxide minerals in flotation, research has proven that sonication improves the mechanical removal of the zinc hydroxide from the surface of the gypsum particles.
Ultrasonic Effects on Flotation
Ishak and Rowson (2009) showed that ultrasonic pre-treatment enhances the removal of heavy metals (namely, iron, zinc, and copper) from acid mine drainage when coupled with a flotation system. In the study, a Denver flotation cell was used. They found that sonication in an early stage of the ultrasonic treatment, which is the first 2 minutes of flotation time, is most effective and gives best results for an enhanced flotation. With a combined treatment of power-ultrasound and the Denver flotation cell, up to 3% of removal difference was achieved in comparison to the Denver cell alone. The correct pH for the metal to precipitate and optimum dosage of suitable frother are other major contributors to the success of the ultrasonically enhanced flotation process.
High Performance Ultrasonicators
Hielscher Ultrasonics is your long-time experienced partner when it comes to high-performance ultrasonic processing. Covering the full range from compact lab ultrasonicators to ultrasonic bench-top processors up to fully industrial ultrasonic systems, Hielscher offer you the most suitable ultrasonic equipment for your application. For processes such as froth flotation, particle surface cleaning and dispersing, Hielscher’s high-performance ultrasonicators are reliable devices, which reliably run 24/7 under heavy loads and in demanding environments. Hielscher Ultrasonics’ industrial ultrasonic processors can deliver very high amplitudes. Amplitudes of up to 200µm can be easily run in continuous 24/7 operation. Precise control over the ultrasonic process parameters, easy parameter setting and adjustment via touch screen or browser remote control, automatic data recording on the built-in SD card and plug-in temperature and pressure sensors ensure user-friendliness, high-quality outputs and consistent product quality.
Our customers are satisfied by the outstanding robustness and reliability of Hielscher Ultrasonic’s systems. The installation in fields of heavy-duty application, demanding environments and 24/7 operation ensure efficient and economical processing. Ultrasonic process intensification reduces processing time and achieves better results, i.e. higher quality, higher yields, innovative products.
The table below gives you an indication of the approximate processing capacity of our ultrasonicators:
|Batch Volume||Flow Rate||Recommended Devices|
|0.1 to 20L||0.2 to 4L/min||UIP2000hdT|
|10 to 100L||2 to 10L/min||UIP4000hdT|
|n.a.||10 to 100L/min||UIP16000|
|n.a.||larger||cluster of UIP16000|
- Ishak, Wan M.F.; Rowson, N.A. (2009): The Effect of Ultrasound Pre-Treatment on Froth Flotation Performance. International Journal of Chemical, Molecular, Nuclear, Materials and Metallurgical Engineering Vol.3, No.6, 2009.