m9 Sewage Effluent Plasticplating

7/29/2019 m9 Sewage Effluent Plasticplating

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SEWAGE TREATMENT BY

ELECTROLYTIC PROCESS


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The wastewater from domestic sourcesotherwise called sewage could be treated by

various methods based on

aerobic biological treatment processes,

anaerobic biological treatment processes and

electro-chemical treatment processes.


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ELECTROCOAGULATION AS A

WASTEWATER TREATMENT


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The most widely practiced method in India is

based on aerobic biological treatment of

sewage. In this article, the electro-chemicalprocess of sewage treatment has been briefly

discussed.

Electrolytic process is a technique involvingthe passage of electricity through wastewater

or effluent to be treated. The electric current

destabilizes the dissolved colloid particles andalters the charge on suspended particles

permitting their coagulation, flotation and

separation.


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Coagulation and flocculation are traditional

methods for the treatment of polluted water.

Electrocoagulation presents a robust novel

and innovative alternative in which a sacrificial

metal anode doses water electrochemically.

This has the major advantage of providing

active cations required for coagulation,

without increasing the salinity of the water.


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Electrocoagulation is a complex process with a

multitude of mechanisms operating

synergistically to remove pollutants from the

water


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A wide variety of opinions exist in the

literature for key mechanisms and reactor

configurations.

A lack of a systematic approach has resulted in

a myriad of designs for electrocoagulation

reactors without due consideration of the

complexity of the system.


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A systematic, holistic approach is required to

understand electrocoagulation and its

controlling parameters.

This will enable a priori prediction of the

treatment of various pollutant types.


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A current is passed through a metal electrode,

oxidising the metal (M) to its cation (M n+ )

Simultaneously, water is reduced to hydrogen

gas and the hydroxyl ion (OH-) .


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Electrocoagulation thus introduces metal

cations in situ, electrochemically, using

sacrificial anodes (usually aluminium or

iron).


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The cation hydrolyzes in water forming a

hydroxide with the dominant species

determined by solution pH.


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The Third Annual Australian Environmental

Engineering Research Event. 23-26 November

Castlemaine, Victoria 1999


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Highly charged cations destabilize any

colloidal particles by the formation of

polyvalent polyhydroxide complexes. These

complexes have high adsorption properties,forming aggregates with pollutants.


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Evolution of hydrogen gas aids in mixing and

hence flocculation. Once the floc is generated,

the electrolytic gas creates a flotation effect

removing the pollutants to the floc - foamlayer at the liquid surface.


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There are a variety of ways in which species can

interact in solution:

1. Migration to an oppositely charged

electrode (electrophoresis) and aggregation

due to charge neutralisation.

2. The cation or hydroxyl ion (OH-) forms a

precipitate with the pollutant.


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3. The metallic cation interacts with OH- to

form a hydroxide, which has high adsorption

properties thus bonding to the pollutant

(bridge coagulation).


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4. The hydroxides form larger lattice-like

structures and sweeps through the water

(sweep coagulation).

5. Oxidation of pollutants to less toxic species.


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6. Removal by electroflotation and adhesion

to bubbles.


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The inherent complexity of the process makes

it difficult to model and control. Adequate

scaleup parameters, a systematic approach to

the optimization and a priori prediction for the

performance ofthe electrocoagulation reactor

are yet to be established. The literature

reveals that previously each new system hasbeen considered separately on an individual

basis.


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There has been little or no attempt to provide

a holistic approach to electrocoagulation. In

order to understand the mechanisms behind

electrocoagulation, and thus control thesystem better, a holistic approach is required.


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Brief Description of Electrolytic

Process:

The wastewater is allowed to pass through the

bar screen chamber to remove the coarse

particles (such as plastic, wood pieces, leaves,

paper, etc) before entering in to theequalisation tank.

The equalisation tank helps in maintaining a

uniform flow to the Electro Cell. The size anddesign of the equalisation tank depends upon

the flow rate and type of the effluent.


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In general the size of the Equalisation tank

varies between 20 35% of the total flow. Theelectrolysed brine from the brine electrolyser

is also continuously injected at about 1% of

waste water flow to the equalisation tank.

The brine electrolyser gets mixed with the

effluent where it oxidizes the organics and

also works as an electrolyte in the Electrocell

for further degradation of organic

components.


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The suspended solids settle down at the

bottom of the equalisation tank and are

pumped out with the help of a sewage pump,

time-to-time.


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The pre-oxidized sewage from the equalization

tank is pumped to the Electro Cell where

electro-coagulation process helps in de-

stabilizing the colloidal and suspendedparticles.


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In the electrolytic process the coagulant is

generated by electrolytic oxidation of anode.

The charged ionic species are removed by

allowing it to react with an ion of oppositecharge.


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It is the use of sacrificial electrodes either of

aluminium or iron which releases positive ions

(Al 3+ or Fe 3+) to coagulate the suspended

particles by forming polyvalent poly-hydroxidecomplexes.

When an electric current is passed through a

metal electrode, dissolution of metal takesplace with simultaneous formation of hydroxyl

ions and hydrogen gas.


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Diagram: EQUALISATION TANK

Excess supernatant liquid from Slurry tank

For instance, if aluminum electrodes are used, aluminum

dissolves into the solution

reacting with the hydroxyl ions to form aluminum hydroxide.

The hydroxide coagulates the suspended solids purifying the

water.

The solids could be removed from the top of the treated tank

by flotation method and treated effluent be allowed to move

by gravity to the sand filter. The sludge could also be allowed

to settle and pumped for sand filtration.


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Electrolysis Process

Ions being acted upon

The treated wastewater from the Electro Cell

is allowed to flow by gravity to the activated

carbon filter. This gives the final treatment

and the treatedwastewater is pumped to the

treated water tank.


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Electrolysis sewage treatment

system The principle of theory supplies the electronic

energy through electrode cells to soil, wastewater

including electrolyte (seawater, NaCl),then it treats

the sewage, wastewater as the oxidation response byHOCl, O3 in the electrode response of oxidation,

reduction, solution which is made by exchange of

direct election between interface of cell and solution

and it's originated material


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After electrolysis treatment of NaCl,It purifies

and sterilizes as causes oxidation action to soil

and wastewater by the strong steriliting power

which is originated in surface of cells.

It treats as floats the suspended solid of

colloid side and the suspended solid material

of water by rising minute hydrogen gas whichis originated in processing of electrolysis

treatment


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Applied Area

Factory wastewater of organic chemical

Factory wastewater of inorganic chemical

Dyeing factory wastewater

Plating factory wastewater

Stock rising wastewater

Petrochemical wastewater

Sewage soil treatment


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INTRODUCTION

There are many industries, such as pulp and papermills, pharmaceutical, and electroplating industries,

which discharge wastewaters with certain pollutants

which would cause a serious impact to the

environment (Chiang et al., 1997). Many pollutants have certain substituints such as

halogen, sulfo-, azo- or nitro-groups. Particularly the

accumulation of such groups and specific

substitution patterns confer xenobiotic character to a

synthetic compound (Campbell, 1977; Knackmuss,

1996). As a consequence, many of these chemicals

tend to persist in the environment.


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Persistent chemicals present the problem of accumulation in

organisms near the top of food chains to a much higher level

generally than in the environment (Alexander, 1977;

Campbell, 1977; Melo and Azevedo, 1997; Tortora et al.,

2000). Consequently, the treatment of the industrial wastewaters

has always been conducted to minimize the threat to the

environment. Biological processes are the treatment systems

used most and they can usually remove readily biodegradableorganics (Chiang et al., 1997).


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However, if the main part of the organic compounds

present in a wastewater is persistent,

microorganisms are not able to degrade it and the

biological processes are not suitable. Depending on their quantity and their

ecotoxicological behavior, the recalcitrant organics

have to be removed by additional treatment (Gulyas,

1997; Chiang et al., 1997; Israilides et al., 1997;Panizza et al., 2000; Moraes et al., 2000; Janssen and

Koene, 2002).


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Electrochemical treatment is a powerful tool

for the purification of this kind of wastewater.

This technology has attracted a great deal of

attention because of the versatility, whichmakes the treatment of liquids, gases and

solids possible. Other characteristics include

energy efficiency, amenability to automationand environmental compatibility.


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In fact, the main reagent is the electron, which is a

"clean reagent" (Rajeshwar et al., 1994). The

electrochemical methods have been successfully

used for the treatment of wastewater fromslaughterhouse (Marconato et al., 1998), textile

wastewater (Naumczyk et al., 1996; Shen et al.,

2001; Xiong et al., 2001), tannery wastewater

(Vlyssides and Israilides, 1997; Szpyrkowics et al.,2001), domestic wastewater (Vlyssides et al., 2002),

and biorefractory organics (Saracco et al., 2001).


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After the electrochemical treatment of

wastewater containing persistent compound,

the biodegradation and toxicity can be

improved (Vlyssides and Israilides, 1997;Chiang et al., 1997; Israilides et al., 1997;

Angelis et al., 1998).


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The present study investigated the degradation of a simulated

wastewater containing the compound n-phenyl n

isopropyl p phenylenediamine (commercial name is

Flexzone 3P), using Ti/TiRuO2 electrodes.

The Ti/TiRuO2 electrodes are dimensionally stable anodes

(DSA) and they are suitable for electro oxidation of organic

compounds.

They show high corrosion resistance and physical/chemistrystability under high positive potentials (Pelegrino et al., 2002).

However, other kinds of electrodes have also been utilized for

electro oxidation of organic compounds such as the synthetic

boron-doped diamond (BDD) electrodes (Panizza et al., 2001). DSA electrodes have been chosen for these experiments due

their good features for treating wastewaters containing

organic compounds (Rgis and Bidoia, 2001a; Chung and Park,

2000).


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The commercial compound Flexzone 3P is an aromatic amine

used by a chemical industry of rubber antioxidant and

antiozonant (Rgis and Bidoia, 2001a) located in Rio Claro, So

Paulo State, Brazil.

The compound Flexzone 3P has been chosen because it is one

of the most important chemical compounds present in the

effluent from that Brazilian industry.

Many aromatic amines have been reported to be powerful

carcinogens and mutagens, and/or hemotoxicants (Chung et

al., 1997; Benigni and Passerini, 2002).

Consequently the treatment of the industrial wastewaters

containing these kinds of chemicals is very important to

minimize the threat to the environment.


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We studied the electrochemical treatment in order

to reduce the toxicity of the simulated wastewater

containing Flexzone 3P.

In particular, conductivity and pH were monitoredwith electrolysis duration. After electrolysis duration,

samples of wastewater were submitted to UV-visible

spectrophotometry analysis, gas chromatography,

toxicity assay and biodegradation test using therespirometric Bartha flask.


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ELECTROPLATING PLASTIC


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Electroplating is the deposition of metal ions

from solution onto an electrically chargedsurface.

The surface must therefore be conductive.

Plastic is not conductive, so directelectroplating of plastic is not practicable.

Instead, the process is performed in steps,

covering the plastic in an adhesive conductor,

like metallic paint, before performing genuine

electroplating.


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METHODS TO PLATE PLASTIC

There are two methods to plate plastic:

One is to roughen the surface to allow metal

to adhere. Then electroplate over that layer to

build up layers of metal. This process is called

electroless, auto-catalytic or chemical plating.

The second method is to apply conductive

paint to the plastic, then electroplate it.


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To begin the roughening method, first clean

the plastic part of all oil, grease and other

foreign matter.

This process can be made complicated if you

want to be thorough, with a long series of

applications of acids and bases. Rinse with

water several times after each step to clearaway the prior cleaning agent before the next

is applied.


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Drop the part in a chrome-sulfur bath. The

acid will pit, or etch, the surface, so that metal

can adhere. An alternative method of etching

is to sandblast the surface.


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Drop the part in a palladium chloride bath.

This will leave an initial layer of metal which

will allow electroplating the standard way.

Specifically, the part will then be electroplatedwith copper as yet another preparation layer,

then gold, chrome, nickel or whatever the

final metal layer is to be.


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Paint Approach

Purchase conductive paint. Inexpensive

conductive paint can be purchased from

Acheson Colloids or Cybershield.

Clean the surface, as above.

Apply the paint.

Electroplate with an initial copper layer, as

above. The rest of the electroplating is the

same as in the pitting approach.


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m9 Sewage Effluent Plasticplating