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Activated Carbon ── Enemy of Pollutants - PowerPoint PPT Presentation


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Activated Carbon ── Enemy of Pollutants. Introduction. Activated carbon is the trade name for highly porous product It can be made from wood, peat, coconut shells and even PVC. Activated carbon has a wide range of uses, such as: 1 Adsorbent in gas- and liquid-phases

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Presentation Transcript
slide2

Introduction

  • Activated carbon is the trade name for highly porous product
  • It can be made from wood, peat, coconut shells and even PVC
slide3

Activated carbon has a wide range of uses, such as:

1 Adsorbent in gas- and liquid-phases

2.Purifier for gases and solutions

3.Decolourant

4.Treating waste water

5.Filter material

6.Separating mixtures

7.Catalysts

8.Medical uses

slide4

History

  • Activated carbon has been used for about 3000 years
  • The first written record is in 1550BC
  • In WWI, activated carbon is used to make gas mask
slide5

Production

  • Four main processes are required in the production of activated carbon
  • Selection of raw materials
  • Granulation
  • Carbonisation
  • Activation
slide6

Selection of raw materials

We should consider the following requirements

  • Required propertied of the final product
  • Cost
  • Availability
  • Consistency of quality
  • Purity
slide7

Granulation

  • Granulation in drum granulators consists of two processes,
  • Grinding the raw material and nixing it with ground and dry bonding agent. The bonding agent can be a temperature between 80 – 150oC or petroleum bitumen.
  • Granulating in drum granulator with an addition of water in a proportion of 30 – 50% of the dry weight of raw materials
slide8

Carbonisation

Carbonisation can ensure that the carbonaceous materials to have the following features that meet the requirements of activation

  • Low content of volatile matter
  • High content of elemental carbon
  • A definite porosity development
  • Sufficient strength of attrition
slide9

Activation

  • There are two kinds of activation method:
  • Gas activation
  • Chemical activation
slide10

Gas Activation:

  • It is a treatment of the carbonaceous materials with oxidising gases at elevated temperature between 700 – 1100oC in the presence of steam
  • The oxidising gases can be steam, carbon dioxide and oxygen
  • A porous structure is formed inside the carbonisates due to the partial gasification of the elemental carbon
slide12

Chemical Activation:

  • During the process, oxygen and hydrogen are removed by dehydrating agent such as phosphoric acid, zinc chloride and potassium sulphide
  • In chemical activation, carbonisation and activation proceed simultaneously below 650oC
  • In chemical activation, the recovery of the activating agent is a very important step because the efficiency determines the cost effective
slide14

Structure:

  • A crude form of graphite, the substance used for pencil leads.
  • It differs from graphite by having a random imperfect structure which is highly porous over a broad range of pore sizes from visible cracks a
  • Have a surface of greater than 1000m2/g
slide15

Structure:

The International Union of Pure and Applied Chemistry (IUPAC) classifies the porosities as follows:

  • Macropores
  • Mesopores
  • Micropores
slide16

Macropores

Mesopores

Micropores

Effective Radii (nm)

> 25

1 – 25

< 1

Volume of the Pores (cm3g-1)

0.2 – 0.8

0.1 – 0.5

0.2 – 0.6

Specific surface areas (m2g-1)

< 0.5

20 – 100

200 – 450

Function

Entrance of AC and act as transport arteries

Contribution to adsorption and transport arteries

Adsorption

Structure:

slide17

Adsorption:

  • Is the working process of the activated carbon
  • Is the term for the enrichment of gaseous or dissolved substances on the boundary surface of a solid.
  • Is a surface phemomenon and directly relate to surface area
slide18

Adsorption:

The adsorption process mainly depends on the following factors:

1)Physical properties of the activated carbon, such as pore size distribution and surface area;

2)The chemical nature of the carbon source, or the amount of oxygen and hydrogen associated with it;

3)Chemical composition and concentration of the compounds;

slide19

Adsorption:

4)The temperature and pH of the water; and

5)The flow rate or time exposure of water to activated carbon.

6)Moisture content, apparent density, hardness and etc.

slide20

What make molecules adsorb:

Adsorption is caused by London Dispersion Forces, a type of Van der Waals Force which exists between molecules.

London Dispersion Forces are extremely short ranged and sensitive to the distance between the carbon surface and the adsorbate molecule.

slide21

In general, the adsorbability of a compound increases with:

  • Increasing molecular weight
  • A higher number of functional groups such as double bonds or halogen compounds
  • Increasing polarisability of the molecule. This is related to electron clouds of the molecule
slide22

Application of activated carbon

> Adsorption for gas phase

> Adsorption on liquid phase

slide23

In Industries

  • Major application is the removal from exhaust gases of toxic components containing sulphur.
  • Sulphur is trapped on the activated carbon surface in three forms:
  • as physically adsorbed sulphur dioxide,
  • as a solution of sulphuric acid and
  • as sulphur compounds bound to the surface.
  • Sulphur dioxide can be removed from the active carbon either by applying a vacuum or by purging with a gas at the adsorption temperature. The adsorbed sulphuric acid can be removed by washing with water.
slide25

Food Industry

  • Activated carbon usually use for the decolorization of sugar syrups. The most intense color is due to substances of molecular mass 8000-15000 occurring in colloidal form.
  • Application of active carbon not only effectively removes its color, but also improves the properties of the product from the technological point of view.
slide26

In human

Activated carbon used for the removal from blood not only externally introduced poisons but also of toxins which appear in the blood due to the failure of the patient’s kidneys.

slide27

Regeneration of activated carbon

1.Thermal and gas methods

2.Extraction and chemical methods

3.Electric and Electrochemical methods

4.Vacuum regeneration

5.Biological regeneration

slide28

Thermal and gas methods

Only granular active carbons were subjected to regeneration since they are much more expensive.

slide29

Extraction and chemical methods

It is possible to avoid losses of the activated carbon during transportation are extraction with special solvents.

The disadvantage of such processes is the need to use large volumes of solvent for complete desorption.

slide30

Electric and Electrochemical methods

This methods reduces significantly the costs of regeneration. As with chemical and extraction methods, the electrochemical methods are very selective with respect to the adsorbates to be removed from the carbon surface.

slide31

Vacuum regeneration

Vacuum regeneration is often used either in conjunction with other methods. The advantage of the vacuum method is that the adsorbent does not react chemically during the regeneration, nor is diluted with regeneration agents.

slide32

Biological regeneration

Biological regeneration of waste waters consists of the symbiotic action of aerobic and anaerobic bacteria

slide33

The link of our project homepage:

http://fly.to/chemproject