There circumstances the removal of dyes for the treatment

There are almost 9000 types of dyes being
used in textile, tannery, paper and pulp, cosmetic, plastics,
coffee pulping, pharmaceuticals, food processing, electroplating and
distilleries spew industries to color the products. Among this textiles
industry is very much important and it stands first in the usage of dyes 1. A
large portion of the colors utilized for shading in industries are taken out in
effluent streams, in this way creating a lot of waste water. Which in turn is
very harmful for the aquatic eco system as well as human beings 2. The
textile dyeing and finishing industry has created a huge pollution problem as
it is one of the most chemically intensive industries on earth, and the No. 1
polluter of clean water (after agriculture). More than 3600 individual textile
dyes are being manufactured by the Industry today. The industry is using more
than 8000 chemicals in various processes of textile manufacture including
dyeing and printing 3.

So under such circumstances the removal of
dyes for the treatment of wastewater is very much needful, in an economical
way. There are lot of different processes for this separation. However, all of
these process is not economical and all the processes cannot handle a large
amount of dye wastewater.  The
advantages and disadvantages of some methods of dye removal from wastewaters
are given in Table 1.4

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table 1. Advantages and
disadvantages of the methods used for dye removal from industrial effluents (Robinson et al., 2001)

Physical/chemical
methods

Advantages

Disadvantages

Fentons
reagent

Effective
decolorisation

Sludge
generation

Ozonation

No change
in effluent volume

Short half-life
(20 min)

Photochemical

No sludge
generation

Formation
of byproducts

NaOCl

Initiate
azo-bond cleavage

Release of
aromatic amines

Cucurbituril

Good
sorption capacity for dyes

High cost

Electrochemical

Non-hazardous
end products

High cost
of electricity

Activated
carbon

Highly
effective for various dyes

Very
expensive

Peat

Good
adsorbent

Surface
area is low

Silica gel

Effective
for basic dyes

Side
reactions in effluent

Membrane
filtration

Removes
all dyes

Concentrated
sludge production

Ion
exchange

No
adsorbent loss

Not
effective for all dyes

 

Adsorption is an economical process and
the separation efficiency of adsorption is quite higher. So in this process
adsorption is being used for removal of dye.

Here malachite green has been used. First
of all, it is cheap and it is easily available in market. Besides this
malachite green is widely used in aquaculture as a pesticide and in food,
health, textile and other industries for one or the other purposes. Due to its
toxic nature It controls fungal attacks, protozoan infections and some other
diseases caused by helminths on a wide variety of fish and other aquatic
organisms. It
has been reported to cause carcinogenesis, mutagenesis, chromosomal fractures,
teratogenicity and respiratory toxicity 5. So it is very harmful in nature. So
it is very needy to know an economic, safe and easy removal process of MG.

Fly ash is being used here as adsorbate.
Fly ash is generally waste material from coal plants. Fly ash cannot be disposed
anywhere due to its toxic action towards soil, ground and surface water. It is
also very cheap and easily available. So using fly ash as adsorbate is useful
here.

 

Hydro cyclone is being used here in this
process. It has several advantages rather than others.   A further advantage of hydro cyclones
is their high operational reliability as they are simple in construction
without any moving parts. In addition, in case of changing operational
conditions, for example with unsteady volume flow, a good separation efficiency
can be achieved 6.

A small modification has been done in this
hydro cyclone. The modification is the spiral ribs attached in the cylindrical
section of the hydro cyclone. This modification will enhance the swirling of
the feed and increase the centrifugal force, which in turn enhance the
efficiency.