flotation & environment

8/6/2019 Flotation & Environment

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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
http://www.imp.mtu.edu/images/head-s.gif


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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
http://www.imp.mtu.edu/images/cenosph1s.gif


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Large silicate pleurosphere Scanning Electron

Microsope (SEM) at 200X
http://www.imp.mtu.edu/images/fa_hol-s.gif


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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

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