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FLOTATION
IN
ENVIROMENTAL
APPLICATIONS
Utku Anl BataBerk engl
Emre Ylmaz
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What is flotation??
Flotation is an enrichment process, used for
separation of valuable minerals from the gang
minerals in the fine size range.
Since 1925
It has gained additional importance as a result
of its use in environmental applications.
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APPLICATIONS
1)Recycling of Glasses
2)Recovery of Plastics
3)Wastepaper Recycling (deinking)4)Flotation of Fly Ash
5)Electroflotation
6) Dissolved Air (Pressure) Flotation (DAF):
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LIFE CYCLE OF GLASSES
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To Final Product
From raw material
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PLASTICS
Modern industrial and home use of plastics has created anenvironmental need to recycle waste plastics of a numberof different types. Most of the commonly used plastics,
such as polyvinyl chloride, polycarbonates,polyacetal, andpolypropylene ether are naturally hydrophobic and arereadily floated without addition of a flotation collector.
Thus, process selectivity is a difficult task. However, plasticsvary in their hydrophobicities and their critical surface
tensions have been explored using surface-active reagents.Thus, their floatabilities can be modulated by use ofsuitable depressants, which include sodium ligninsulfonate, tannic acid, and Aerosol OT (Shibata et al., 1996).
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Froth flotation is a new technology that caneffectively separate two or more types of plasticthat have similar or identical densities. It is
applied as a finishing step to conventionalseparation methods already used for plastics ofdifferent densities.
The froth flotation process uses the surface wetting
characteristics of the plastic materials as the basisfor separation.
The plastics are immersed in a chemical solutionthat alters the surface-wetting characteristics of
the different plastics. Small gas bubbles areattached to the surface of one plastic, causing itto float, while the other plastic sinks.
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Selective flotation separation of the PET/PVC mixture isimpossible without changing the surface properties ofone of these polymers. Both polymers exhibit almost
the same degree of hydrophobicity. In this researchTanic acid was employed as a wetting agent forselective depression of PET during flotation.
The selection of reagent and its dosage was based on thecontact angle measurement () of PVC and PET atdifferent conditions. Using a full factorial designprocedure, the effects of depressant dosage (i.e., Tanic
acid), temperature, and pH were optimized. The resultsindicate that at the optimum conditions, separation ofPET and PVC by grade and recovery of more than 99%can be achieved.
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The effect of ink types and printing processes on flotation
deinking
efficiency of wastepaper recycling
Xiansheng Nie, J. D. Miller, Y. D. Yeboah
Newsprint oil-based (offset-cold-web/offset-heat) inks, and water-based inkare liquid, and laser-print and photocopy toners are solid powders. Exceptfor water-based ink, which is soluble in water, the other inks (includingdried water-based ink) are originally hydrophobic so that separation of inkcan be achieved by froth flotation from the cellulose fiber.
During the printing processes, newsprint oil-based offset-cold and offset-heatinks, and water-based ink have no significant change in their chemicalproperties, specifically their hydrophobic characteristics, which makesthem easily separated from cellulose fibers by flotation.
On the other hand, during the printing process, the photocopy and laser-printtoner particles undergo polymerization and oxidation with subsequentformation of peroxide bonds due to exposure to heat, light, and oxygen(air). The polymerization causes a strong chemical and physical bondingwith cellulose fibers and creates larger particle sizes. The oxidation createsa greater polarity at the toner particle surface. Both factors account forthe poor efficiency in the flotation deinking.
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1.Waste paper 2.Pulper. 3.Koullandrc Tank
4.FolyoTutucu, 5.Flotasyon hcresi6.Filtre
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Table 4. Contact angle for different materials
Sample
(captive bubble)
Contact angle
Blank Newspaper 0.07
Oil-Based Black Ink 81.27
Fresh Photocopy Ink 93.07
Discarded Photocopy Ink 68.57
Fresh Laser Ink
91.57
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Fly ash flotation
Municipal solid waste (MSW) fly ash has recently
attracted much attention because of its large quantity
and enrichment of heavy metals with low boiling point
and trace organic contaminants such as dioxins.
Column flotation has been widely used in the solids
separation encountered in primary mineral and chemical
industries, such as coal cleaning (Leja, 1982). The
separation process is schematically shown
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Schematic diagram of the flotation
column: 1, column; 2, gas distributor (porous plate);
3, air compressor; 4, flow controller; 5, flow meter.
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As Received Flyash
Scanning Electron Microscope
(SEM) at 1000X
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Cenospheres removed during benefication. Hollow spheres with
A1/Si ratios varied from 1:1 to 1:2. Scanning Electron
Microscope (SEM) photograph at 100X
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Large silicate pleurosphere Scanning Electron
Microsope (SEM) at 200X
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ELECTROFLOTATION
Electroflotation is a method by which dispersed
solids are removed from aqueous mixtures by
the production of hydrogen and oxygen gas
through electrolysis of water. As the gascomes up from solution, particles adhere to
the outside of the bubbles and are buoyed to
the surface where they are removed by askimmer
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Electrocoagulation: It involves the electrochemicalproduction of so-called destabilizing agents that
neutralize the charge of pollutants and enable easy
removal.
Electroflocculation: Electrochemical production of
agents that promote particle bridging or
coalescence.
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Applications of Electroflotation
Waste water treatment (oil,metals)
Removal of fluoride from drinking water Purification of purines
Emulsified oil in industrial wastes
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Wastewater treatment process using electroflotation
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Removal of fluoride from drinking water
Electrocoagulation and electroflotationcombination
Total hydraulic retention time 30 min
Fluoride concentration was reduced from initial4.0-6.0mg/L to lower than 1.0mg/L.
Optimal influent pH range is 6.0-7.0
SO(4)(2-) had negative effect; Ca(2+) had positive
effect; while Cl(-) had little effect on the fluorideremoval
Fluoride was reduced from initial 4.0 to 0.87mg/L.
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Purification of purines
Electroflotation consists in transferring the purine fromone metal plate to another while injecting a low-voltage electrical current between the plaques. Usingthis method and, as a consequence of the electric
current, two phenomena are observed:- The iron (Fe2+) from the plates dissolves, coagulatingthe organic material of the purine and making itflocculent.
- Hydrogen bubbles are created making the organicmateria float on the water and creating an upper layereasily extractable.
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Emulsified oil in industrial wastes
d f h l i ill
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Current and future technologies will
have to deal with some areas such as:
Process water treatment and recycling
Removal/Recovery of ions
*Heavy metal ions must remove the systemespecially Hg+, Pb2+, Cr6+
**Recovery of precious metals such as Au, Ag,
and Platinum Group Metals (PGM)
Cyanide & Arsenic emission control
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Oil spills separations
Acid mine waters containing considerable
amounts of harmful base metals such asnickel, copper, zinc, lead in addition to ferrous
iron and sulfate
Control and removal of residual chemicalreagents such as frothers, flotation collectors
and modifiers
Separation of various wasted plastics
Table Examples of some commercially available
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Table - Examples of some commercially available
flotation devices for wastewater treatment
Table Differences Between Flotation in Mineral
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Table - Differences Between Flotation in Mineral
Processing and in Wastewater Treatment
Dissolved Air (Pressure) Flotation
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Dissolved Air (Pressure) Flotation
(DAF)
DAF was recognized as a method of separating particles inthe early 20th Century since then has found manyapplications including:
Clarification of refinery wastewater, wastewaterreclamation,
Separation of solids and other in drinking watertreatment plants;
Sludge thickening and separation of biological flocs;
Removal/separation of ions;
Treatment of ultra-fine minerals Removal of organic solids, dissolved oils and VOCs
(dissolved toxic organic chemicals);
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Typical DAFUnit
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Parts of DAF unit
Contact cell or coagulation chamber
Flotation cell
Surface skimmer
Bottoms skimmer or auger.
Effluent discharge baffle and chamber.
Air saturation (whitewater) system
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Air Solubility in Water-PressureCfh air/gpm: Air Solubility
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Comparison of Saturator Efficiencies
for Different Types of DAF Recycle Pumpsscfh air/gpm: Air Solution Rate
C i f P bli h d DAF D i
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Comparison of Published DAF Design
Parameters
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THE END
Thanks for Listening Us
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References
J. Rubio, M.L. Souza, R.W. Smith, Overview of flotation as a wastewater
treatment technique, 2001
Charles C. Ross, Brandon, M. Smith, G.E. Valentine, RETHINKING
DISSOLVED AIR FLOTATION (DAF) DESIGN FOR INDUSTRIAL
PRETREATMENT, WEF and Purdue University Industrial Wastes Technical
Conference, 2000
F. N. B. Nahui, M. R. Nascimento, E. B. Cavalcanti, E. O. Vilar,
Electroflotation of Emulsified Oil in Industrial Wastes Evaluated with a full
Factorial Design
Zuo Q., Chen X., Li W., Chen G., Combined Electrocoagulation and
Electroflotation for Removal of Fluoride from Drinking Water