Flotation Advances in Mineral and Wastewater Treatment

Dear Colleagues,

Flotation is a very efficient unit operation employed worldwide to separate valuable minerals from gangue materials (this is called froth flotation) and in the treatment of wastewaters as a solid (liquid) water separation, removing several pollutants. This issue covers the advances in these two areas.

Froth flotation is the most efficient and cost-effective mineral particle separation in ore processing. However, the recovery of coarse (higher than 100 µm), fine (less than 74 µm) and ultrafine (less than 13 µm) particles is very poor. In the coarser particles, flotation acts as an ancillary novel process in the so-called fluidized-bed flotation cells (FBFCs such as HydroFloat, NovaCell, and Reflux Flotation Cell). Mechanisms involved are longer retention time, less particle buoyancy constraints and less particle detachment from the bubble.

The problem of the poor recovery of small particles is mainly due to the low probabilities of bubble–particle collision and bubble–particle capture. The process efficiency appears to enhance with microbubbles (30–100 μm diameter) and/or nanobubbles (80–800 nm diameter). The nanobubbles (billions of them) rapidly attach to hydrophobic particles and serve as nuclei for the micro or microbubbles (700 μm–2 mm diameter) to adhere to, assisting in the flotation.

The main items covered in this Special Issue are:

1. The simultaneous generation and injection of micro- and nanobubbles at a high rate;
2. The mechanisms involved in the enhancement of the contact angles (hydrophobicity) and aggregation of the ultrafine particles, by the nanobubbles;
3. The role of fine bubbles as possible nuclei (“seeds”) for other bubbles, micro and macro (such as a multi-bubble consortium) to adhere onto mineral particles. Is this a new alternative to improve the flotation recovery of fine mineral particles?

Flotation is a process of treating wastewaters. Here, the issue comprises the advances in treating wastewaters or remediation of contaminated environments. The work envisages the potential of the use of nano- and microbubbles for the removal of a variety of pollutants, and for the reuse or recycling of treated wastewaters.

Alternatives for separating colloidal precipitates and nanoparticles, mineral flotation reagents (xanthates, fatty acids, amines, oils) and suspended solids in process waters, are discussed. These targets are usually present in filter waters, thickener overflows and hydrocyclones.

Prof. Dr. Jorge Rubio
Prof.Dr. Dongping Tao
Prof. Dr. Lev Filippov
Prof. Dr. Guihong Han
Guest Editors

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• flotation
• fine mineral processing
• nano- and microbubbles
• wastewater treatment
• water reuse