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The Effect Of Ultrasound Pre- Treatment On Froth Flotation Performance. WMF Wan Ishak*, N. A. Rowson, School of Chemical Engineering, Birmingham University, UK. OBJECTIVE.
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The Effect Of Ultrasound Pre-Treatment On Froth Flotation Performance.WMF Wan Ishak*, N. A. Rowson, School of Chemical Engineering, Birmingham University, UK
OBJECTIVE • Compare the effect of the ultrasonic pre treatment on the removal of heavy metals (Iron, Zinc and Copper) from Acid Mine Drainage (AMD) by Denver Cell Flotation.
Materials and methods • The metal solutions used in this experiment was prepared from pure metal compounds. • Zinc sulphate hepthahydrate, ZnSO4.7H2O • Copper (II) sulphate, CuSO4.5H2O • Iron (III) sulphate penthahydrate Fe2(SO4)3.5H2O
Materials and methods • Two litre of every sample put into a container and was adjusted to pH 9 by using sodium hydroxide solutions. • A Denver cell was used as flotation units. • Ultrasonic bath as ultrasound source
Materials and methods • Three different experiments were conducted, one with the pre-treatment of ultrasound prior to flotation • Second without the pre-treatment • Third with ultrasonic and flotation operating simultaneously.
Initial experiments conducted with synthetic solutions • Real Acid Mine used after optimum condition were satisfied
Denver Cell and sample optimum conditions • Floatation Machine Denver cell • Impeller speed 1000rpm • Sample 50 ppm of 2 litre synthetic metals • Frother 0.15ml/l of A845 • Temperature Ambient • pH 9 with NaOH • Flotation time 8 minutes • Ultrasound time 10 minutes • Conditioning time 3 minutes
For single solution metal removal of these metals by using simultaneous ultrasonic and Denver cell treatment, gave an improvement in iron removal but not for zinc. • Copper removals with this method only benefited at the end of flotation process. • Experiments were carried out to look at the metal removal in synthetic mixture solution of copper, zinc and iron to estimate the optimum condition for rAMD from the Wheal Jane Mine site.
With the comparison of the three methods: • It is clear that simultaneous ultrasonic can not improve the efficiency removal. • Ultrasonic pre-treatment still is the best method to apply for synthetic AMD. • Although the pre-treatment method takes a longer time compared to other two methods, the quality of the treated water is more important to consider when choosing a suitable methods.
An aerial photograph of the Wheal Jane pollution incident in 1992. (Image from Wheal Jane Project website)
CONCLUSION • Ultrasound pre-treatment enhances the metal removal when coupled with the flotation system. • The early stage of the treatment (first 2 minutes of flotation time) is very important part of ultrasonic effect. • Up to 3% of removal difference compared to the Denver cell alone was achieved by using ultrasonic treatment. • The correct pH for the metal to precipitate and optimum dosage of suitable frother however are other major contributors to the success of this technique.
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