Removal of congo red from wastewater by adsorption onto waste red mud

Vol. 34. No. 2, pp. 401417,
1997
Copyright 0 1997 Elsevier Science Ltd
Printed in Great Britain. All rights reserved
0045.6535/97
$17.00+0.00

Chemosphere,

PII: SOO45-6535(96)00385-Z

REMOVAL

OF CONGO

RED FROM

WASTEWATER

BY ADSORPTION

ONTO WASTE RED MUD

C. NAMASIVAYAM*

and D. J. S. E. ARASI

Environmental
Chemistry Division
Department of Environmental
Sciences

Bharathiar University
Coimbatore - 641 046
Tamil Nadu - INDIA.
(Received in USA 23 June 1996; accepted 23 August 1996)

ABSTRACT

Waste
generated
for

during

the

red

the

adsorption

Adsorption

as dye concentration,

data
The

isotherms.
dye

was

quantitative
suggest

that

exchange.0

Key

words

first

mg/g.

the

Elsevier

: Waste

red

the

solution.

parameters

agitation

time

Author
E-mail:

to whom

and pH.

equilibrium

both

Langmuir

and

Freundlich

capacity

of
was

the
found

of pH and
of

Science

congo

red,

All

to

mud
be

desorption

adsorption
Ltd.

red

is
rights

adsorption

correspondence

should

sandflas250.bharathi.ernet.in

401

for

the

nearly
studies

mostly

ion

reserved

isotherms

pH effect.

*

such

The

Effect

mud,

is recycled

expression.

mechanism

1997

dose,

ore,
aqueous

using

Adsorption

2.0.

from

byproduct,

rate

obeyed

at pH

red

studied

adsorption

4.05

of bauxite

adsorbent

followed

adsorption

congo

were

industrial

an

processing
of

kinetics

Adsorption

mud,

be addressed.


402

INTRODUCTION

Colour

is

one

of

the

characteristics

of

an

effluent which is easily detected and readily traced back to

its source. Most dyes are stable to biological degradation.
Coloured waters are often objectionable on aesthetic grounds
for drinking and other agricultural purposes. Colour affects
the nature of the water by inhibiting sunlight penetration
thus

reducing

carcinogenic

photosynthetic

and mutagenic

action.

Some

(1). Hence there

dyes

are

is a need to

remove dyes from wastewaters before it mixing with receiving
waters.
The treatment of dyes in industrial wastewaters
poses several problems

photodegradation
treated

by

the

Activated

available.

adsorbent

is

carbon

and has

of

aerobic

an attractive

adsorbent

stable to

(2); hence, they cannot be

methods

of dyes provides

if

popular

and oxidation

conventional

Adsorption
removal

since dyes are generally

been

alternative

inexpensive
the

most

used

with

is

digestion.

readily

and

efficient
great

for

and

success.

However, high costs in the procurement of activated carbon
restricts

its

Namasivayam
adsorbents
These

(3)

in

has

developing

recently,

countries

reviewed

like

India.

non-conventional

used for the removal of dyes and heavy metals.

include

residual

use

slurry

agricultural
(4),

banana

solid
pith

wastes

such

(5), orange

as

biogas

peel

(6),


403
bagasse
as

and

paddy

straw

Fe(III)/Cr(III)

Namasivayam
of dairy
(11)

and coworkers

from

employed

solutions.

of using

containing

congo

fly

ash

and

coal(g).

et

al.

(12)

have

of nickel.

of this

a textile

such

of chlorophenol

study

was to evaluate

red mud for the treatment

red,

waste

red mud for the treatment

Zouboulis

for the removal

The objective
feasibility

and

solid

(10) and for the removal

aqueous

red mud

industrial

hydroxide(8)

wastewater

employed

(7) and

the

of wastewater

dye as a typical

case

(13).

EXPERIMENTAL
Materials
Waste
Aluminium
the

at

Factory

adsorbent.

water

for

red

Tamil

Nadu,

powder

was

was

obtained

from

M/S

India)

was

washed

particulate

fine

The

obtained

thoroughly

was

very

5 h.

Congo

studies.

mud

(Mettur,

It

to remove

60°C

red

used

used
CIBA

for

as

distilled

( < 53 /A) and

then
from

with

Mettur

dried

adsorption

- GEIGY

(Bombay,

India).
Methods
Batch
by agitating
250

mg

of

adsorption

50 mL of dye
adsorbent

temperature

(30

solution

separated

at

8,600

was
x

g.

?

in

The

2'C)

solution
glass
using

from

dye

experiments

the

at natural

bottles
a

at

shaker

adsorbent

removal

were

was

140

carried
pH

(7.3) with

rpm

machine.

out

at
The

room
dye

by centrifugation
estimated

spectro-


404

photometrically
wavelength

by monitoring

of maximum

spectrophotometer

For

removal,

the

(Model

U-3210,

studies

on

initial

of the

with

dye

pH.

(495.8

the

Hence

the

from absorbance

adjusting

final

pH

to

7.3.

adsorption

experiments

evaluating

follows:

time

After

supernatant
adsorbent

samples

dye

varied

from

no change

the

of the

of dye solutions
data

were

for

effect

dye

after

Langmuir

taken

from

and
batch

of agitation
dose

in

absorbance

removal

and adsorbent

desorption

adsorption

of 10 mg/L

greater

Several

was

upon

time,

on per cent

respectively.

Batch

solution

cent

The

isotherms

dye concentration

at the

a Hitachi

pH

was

conditions

values

adsorption

removal,

of

solution

per

Freundlich

initial

effect

in acidic

was determined

and

nm) using

7.3 to 11.0 there

But

changes

Tokyo).

pH of the dye

changed.

the

absorbance

absorption

2 to 11. In the pH range
absorbance

the

than
dye

was
such
were

different
separated
as before.

pH

and
the

samples

values

experiments

equilibrium
was

gently
were

agitated

were

time

remove

prepared.

with
for

from the adsorbent

50

100

mL

min.

50

i.e.
The

any

Then
of
The

out

mL

of

as
dye

for an agitation

discarded.

to

carried

with

250 mg of adsorbent

solution

washed

studies

100

min,

dye

loaded

unadsorbed

the spent
water

by centrifugation

dye.

adsorbent

adjusted

desorbed

the

dye

to
was

and estimated


405
RJZ!3ULTSANDDISCUSSION
Effect of contact time and concentration
Figure
initial
The

concentration

removal

contact
until

1

of

time

was

rapid

gradually

concentrations
36.5

10 to

$ to

40 mg/L.

continuous
surface

used.

agitation

of congo

in

the

decreased

The

time was

The equilibrium

25.7

% as dye
removal

indicating

time

and

red by red mud.

initial
with

stages

lapse

of

of
time

90 min
uptake

for all the dye
of dye decreased

concentrations

curves

monolayer

increased

from

were

single,

smooth

coverage

of

on

dye

and

outer

of adsorbent.

20

40

60

80

loo

Agdatlon

Fig.

of

equilibrium.
The equilibrium

from

effect

on adsorption

dye

and

shows

120
lime

140

160

180

200

(min)

1. Effect of agitation
time and dye concentration

on
removal:
Dye concentration:(O)10 mg/L,(D)
- 20
mg/L,(A)30
mg/L,(e)40
mg/L, Adsorbent
dose - 250
mg/50 mL; pH - 7.3.


406
Adsorption

dynamics
The

by red mud was

log10

where

qe

and

equilibrium
the

rate

(qe

-

Pig.

using

q are

the

at time

vs

qe

amounts
t (sin),

were

which

2. Lagergreen

adsorption

order

plots

rate

rate equation

of

dye

adsorbed

Linear

that

expression

(4),

for dye adsorption

at
is

of

loglo

different

dye

adsorption
(Fig.

(mg/g)

and kad

plots

for
the

red

(1)

respectively,

obtained

indicate

of congo

kadt
___
2.303

of adsorption.
t

the first

for

Lagergren

(qe - 9) = log10

constant
9)

constant

studied

and

concentrations,
follows

rate

process

2). Adsorption


407
rate constants
rate

(kad) are presented

constants

slurry

for

(4) waste

banana

Fe(III)/Cr(III)
0.106,

0.0406

congo

red

pith

hydroxide
and 0.34

in Table

(50 mg/L)

(5), orange

(8)

l/min,

were

1. Adsorption

on

biogas

peel

waste

(6) and waste

reported

to

be

0.028,

respectively.

Table - 1
Rate

constants

for adsorption

Concentration
of congo red
(mg/L)

Langmuir

10

3.34 x 1o-2

20

6.66 x 1o-2

30

7.55 x 1o-2

40

3.57 x 1o-2

isotherm
Langmuir

adsorption

on

a

isotherm

surface

identical

sites.

adsorption

on the surface

in

the

Adsorption
rate constant
k ad (I/min)

plane

represented

of

The

the

containing

model

assumes

valid
a

surface.

The

for

finite

uniform

and no transmigration

by the equation

‘e
-=-+

is

Langmuir

monolayer
number

of

energies

of

of adsorbate
isotherm

(6)

1

'e

(2)

is


408

where,
The

C e is the concentration

constant

related
'e

Q,

signifies

to the energy

shows

that

the

The

values

slope

and

intercept

Table

2. The applicability

and

of the

coverage

of

and b values

non-conventional

of Q,

congo

red

10

3. Langmuir

plot

isotherm

the

are shown

15

20

25

surface
of congo

in Table

30

hg/L)

for dye adsorption

is

of C,/q,

vs

Langmuir

and

isotherm
from

and are presented

adsorption

Ce

Fig.

on

plot

b

calculated

plot

of Langmuir

adsorbents

5

b were

at equilibrium.

capacity

Linear

follows

linear

for the

1:

(mg/L)

adsorption

adsorption

3).

The Q,

the

of adsorption.

(Fig.

monolayer

of dye

35

suggests
of
red
2.

red

the
in
the
mud.

by some


409

Table
Langmuir

- 2

constants
Q

Adsorbent

Ref.

L/w4

44.00

0.0505

9

Waste

Fe(III)/Cr(III)

Waste

Orange

peel

22.44

0.0680

7

Waste

banana

pith

20.29

0.0900

6

9.50

0.2116

5

Biogas

waste

hydroxide

b

w9g

slurry

Waste

red mud

4.05

0.0360

Paddy

straw

1.01

0.8700

The
isotherm

called

can

characteristics

essential
expressed

be

equilibrium

by

parameter,

a

of

dimensionless

RL, which

This
work
8

Langmuir

constant,

is defined

by,

l

SC

1 + bco

where

b is the

concentration
0 and

Langmuir

red mud

and

The RL values

(mg/L).

1, indicating

constant

favourable

found
for

initial

dye

to be between
congo

red

on

studied(6).

isotherm

Freundlich
adsorption

were

is the

adsorption

for all the concentrations

Freundlich

Co

of congo

equation

red on red mud

was

also

(5).

applied

for

the


410

X

log10

1

-

=

log10

kf

+

-

m
where
of

x is the

the

amount

adsorbent

of dye

used

(g),

is

Ce

in solution

(mg/L)

incorporating

all

affecting

as

follows
kf

adsorption
x/m

log10

capacity

vs

log10

Freundlich

'e

isotherm

greater

value,

values

factors

will

of k, and n are

be

shown

and

the

equilibrium

and kf and
the

constants

adsorption

process,

intensity.

Linear

that

(Fig.

4). In general,

the

plot

adsorption

adsorption

in Table

capacity.

3 along

with

non-conventional

adsorbents

05

reported

those

in literature.

Corr coetft=0.9904

o-4

1

03-

o-0

\ -

-3 2 I

-0 3.

0

02

I
0.4

I
06

08

10

12

kl;c,Ce

Fig.

4. Freundlich

plot

for dye adsorption

14

i6

of

also

higher

L

other

dye

n are

shows

the

(4)

ce

(mg), m is the weight

adsorbed

concentration

such

log10

n

the
The
of


411

Table

- 3

Freundlich

constants

Adsorbent

Paddy

straw

Waste

Fe(III)/Cr(III)

Waste

banana

Biogas

waste

7.69

7

2.01

1.93

8

pith

1.20

1.46

5

slurry

I.20

1.50

4

1.21

1.82

14

hydroxide

red mud

Effect

0.22

increased

than

from

9 (Fig.

the

initial

2 to
5).

initial

11 the

The

per

pH

cent

decrease
on the
base

is

important

removal

vs

of aqua

dissociation

of

per

cent

pH

the

after

initial

This
work

final

pH

with
complex

solution

was

removal

decreased

from

adsorption

the

per

increase

was

cent

shown

and

removal.

in Fig.

(13).

The

5c.

The

explained

subsequent

interface

is

(13); hence,

in pH may be

formation

higher

2 to 7. This

of red mud

is also

at solid/solution

dye

pH range

of alkalinity
to explain

in adsorption
basis

pH

final

pH in the

due to the contribution
final

1.46

of pH

When

98 to

Ref.

4.79

Wollestonite
Waste

n

k,

acid-


412

0

3

I

L

I

5

I

I

6

7

I

,&

8

9

,
10

II

Final pH
13

100
80

11

1:

,.

"P

O9++rk

10
Initial

12

14

16

pH

Fig. 5. A. Effect of initial pH on per cent removal of dye
B. Effect of initial pH on Final pH
C. Per cent removal vs Final pH
In acid medium, positive charge develops on the surface of
oxides of adsorbent and may be written as

H+
M-O
/

+

H-OH-->

"\ M - OHZ+
/

+ OH-

(5)


413
where
the

M stands

solution

surface
with

of

Cl-

for

Al

or

Si present

is acidified

positively

ions.

The

by

hydrochloric

charged
chloride

in the

interface
ions

are

red

mud.

Since

the

outer

acid,
will

be

associated

exchanged

with

dye

anions.

M -

OHa+

/ Cl-

+

"\ M - OH2+

Dye- -->

0/

/ Dye- + Cl-

O/

(6)
With

an

oxide/solution

charged

in

interface

of the adsorbent
negatively

increase

i.e.

charged

pH,

decreases.

positive

charge

At pHs

above

8 - 10, the adsorbent

and

will

ions of the solution

be

on

the pH-zpc

surface

associated

with

in the following

the

becomes

positively

manner:

(7)

Thus
surface

outer

consequently
observed
and

there
of

the

are

the

waste

Fe(III)/Cr(III)

exchangeable

adsorbent

adsorption

in the adsorption

no

at

decreases.

of congo

anions

higher
Similar

the

pHs

and

trend

was

red on wollastonite

hydroxide(8).

on

(14)


414
Desorption

studies

Desorption
mechanism
This

of adsorption

may make

desorption
medium

mechanism

and

increases

with

in

the

3I

process

4I

stated

5I

in the

studies

I

I

I

7

8

6. Effect

of pH on per cent

adsorbent.

The per cent

pH of the

again

aqueous

confirms

in the pH effect.

6

the

to the pH effect.

I

9

PH

Fig.

and

economical.

increase

desorption

elucidating

of dyes

is just opposite

of adsorption

01

help

recovery

the treatment

(Fig. 6). This

observation

studies

desorption

I

10

I

11

The
the


415

CONCLUSIONS

1.

Red

mud,

a waste

industry,

can

the removal

2.

The

be

The

from

effectively

of congo

adsorption

isotherms.

byproduct,

a bauxite

used

as

an

processing

adsorbent

for

red from wastewaters.

followed

both

Langmuir

Langmuir

adsorption

and

Freundlich

capacity

was

4.05

m9/9.
3.

Almost

quantitative

dye removal

occurred

at the initial

pH of 2.0.

4.

The

kinetic

technologist

5.

data

may

in designing

removal

from wastewaters

As

adsorbent

the

processing

be

useful
treatment

enriched

i.5 discarded
the

industry,

for

plants

with

as

treatment

environmental

congo

waste
method

for

colour

red.

in
is

bauxite
expected

to be economical.

ACKNOWLEDGEMENT

Authors
authorities
facilities.

for

are

thankful

providing

to

Central

Bharathiar

University

Instrumentation

Lab


416
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