Removal of dyes from an artificial textile dye effluent by two

agricultural waste residues, corncob and barley husk

T. Robinson, B. Chandran, P. Nigam*

School of Biomedical Sciences, University of Ulster, Coleraine, Londonberry BT52 1SA, Northern Ireland, UK

Received 19 August 2001; accepted 21 November 2001

Abstract

The use of a previously untried biosorbent, barley husk, for dye removal is compared to corncob. The effectiveness of adsorption as a

means of dye removal has made it an ideal alternative to other more costly treatments. This paper deals with two low-cost, renewable

biosorbents, which are agroindustrial by-products, for textile dye removal. Experiments at total dye concentrations of 10, 20, 30, 40, 50,

100, 150, and 200 mg l� 1 were carried out with an artificial effluent consisting of an equal mixture of five textile dyes. The effects of

initial dye concentration, biosorbent particle size, dose of biosorbent, effective adsorbance, and dye removal kinetics were examined. One

gram (per 100 ml) of � 600 mm corncob was found to be effective in removing a high percentage of dyes at a rapid rate (92% in 48 h).

One gram of 1� 4 mm barley husk was found to be the most effective weight and particle size combination for the removal of dyes (92%

in 48 h). The results illustrate how barley husk and corncob are effective biosorbents concerning the removal of textile dyes from effluent.

D 2002 Elsevier Science Ltd. All rights reserved.

Keywords: Adsorption; Barley husk; Corncob; Textile dyes

1. Introduction

The release of dyes into wastewaters by various indus-

tries poses serious environmental problems due to various

dyes’ persistent and recalcitrant nature. Textile industries are

responsible for the discharge of large quantities of dyes into

natural waterways due to inefficiencies in dyeing techni-

ques. Up to 50% of dyes may be lost directly into waterways

when using reactive dyes (McMullan et al., 2001).

The presence of dyes in waterways is easily detectable

even when released in small concentrations (Nigam et al.,

2000). This is not only unsightly, but the colouration of the

water by the dyes may have an inhibitory effect on pho-

tosynthesis affecting aquatic ecosystems. Dyes may also be

problematic if they are broken down anaerobically in the

sediment, as toxic amines are often produced due to incom-

plete degradation by bacteria (Weber and Wolfe, 1987).

Hence, colour removal from textile wastewater is of major

environmental concern (Juang et al., 1996).

Conventional physical and chemical treatments for dye

removal (Robinson et al., 2001) have been shown to be

either expensive, e.g., activated carbon and membrane

filtration (also incapable of treating large volumes), or

produce a concentrated sludge, e.g., Fentons Reagent.

In water reuse technology, various techniques have been

employed in the past for the removal of dyes from waste-

water (Perineau et al., 1982; Singh et al., 1984; McKay et al.,

1985; Gupta and Bhattacharya, 1985; Khattri and Singh,

2000; Low et al., 2000; Liversidge et al., 1997; Mittal and

Gupta, 1996; Choy et al., 1999) Removal of dyes by

adsorption has been shown to be an effective way of treating

dye-containing effluent (Robinson et al., 2001; Kamel et al.,

1991; Keith et al., 1999; McKay, 1981).

Although the most widely used physical method for dye

removal is activated carbon (Nasser and El-Geundi, 1991),

due to its high degree of effectiveness, it has high running

costs (requires regeneration after sorption) and so there is a

need for an equally effective but cheaper sorbent (McKay,

1981). The use of agricultural residues for dye removal

using corncob has been investigated by El-Geundi (1991),

but no work has been carried out using barley husks. Barley

husks are renewable agricultural residues and are widely

available in many countries.

0160-4120/02/$ – see front matter D 2002 Elsevier Science Ltd. All rights reserved.

PII: S0160 -4120 (01 )00131 -3

* Corresponding author. Tel.: +44-28-7032-4053; fax: +44-28-7032-

4906.

E-mail address: p.nigam@ulst.ac.uk (P. Nigam).

www.elsevier.com/locate/envint

Environment International 28 (2002) 29–33

The main aim of the present study was to develop a

cheap and suitable method for the removal of dyes from an

artificial effluent. As corncob and barley husk meet the

above criteria, they have been studied for their effectiveness

in the removal of dyes from an artificial effluent containing

five dyes. The effect of the performance of various oper-

ating parameters on adsorption such as adsorbent dose,

concentration of dyes, and particle sizes were monitored.

Kinetic parameters were also studied for the removal of dyes

by these substrates.

2. Materials and methods

The reactive dyes used in this study were Cibacron

Yellow C-2R, Cibacron Red C-2G, Cibacron Blue C-R,

Remazol Black B, and Remazol Red RB. The dyes were a

gift from Fruit of the Loom, Buncrana, Rep. of Ireland. The

corncobs were purchased from a local supermarket and the

barley husks were a gift from Bushmills Distillery, London-

derry, Northern Ireland. The substrates were dried to a

constant weight.

The artificial effluent was prepared by dissolving the five

dyes, in equal amounts, in distilled deionized water to

produce a stock solution of 1000 mg l � 1. From this,

100 ml volumes containing initial concentrations (Co) of

10, 20, 30, 40, 50, 100, 150, 200 mg l� 1 were made.

The substrates were tested for their adsorbance capacities

at two different sizes: 1� 4 mm, which was obtained by

coarsely milling dried strips of corncob (barley husk were

already of that approximate size); and � 600 mm particle

sizes which were obtained using a 600-mm sieve. Different

doses (dry weight) of each substrate were added to 100 ml

of the artificial effluent at the varying concentrations.

Decolourisation was recorded using a spectrophotometer.

One milliliter samples were taken at regular intervals,

centrifuged in a microcentrifuge at 13,000 rpm, and decol-

ourisation calculated from lmax readings (600 nm). Experi-

ments were carried out statically at room temperature,

20 ± 2 �C, and carried out in duplicate.

3. Results and discussion

3.1. Effect of contact time and concentration

Adsorption of dyes from an artificial effluent onto barley

husk was measured at given contact times for four different

initial dye concentrations at an adsorbent dose of 5 g

(1� 4 mm of particle size per 100 ml). The effect of initial

dye concentration on the rate of adsorption is shown in

Fig. 1. The percentage of dye adsorbed increased as the

initial dye concentration increased with 82% of dye being

removed with a Co of 50 mg l� 1, 85% at 100 mg l � 1, 89%

at 150 mg l � 1, and 91% at 200 mg l � 1 after 24 h. This

showed that the equilibrium capacity of the barley husks

increased as the initial concentration increased. The per-

centage of dye removal was low for lower dye concentra-

tions of 10 to 40 mg l � 1 (results not shown), when

compared to that for the higher concentration range (as in

Fig. 1) for the same 24 h.

Fig. 2 shows that the percentage dye removal by corncob

decreased from 81%, 71%, 62%, and 42% when the initial

concentrations were 50, 100, 150, and 200 mg l� 1, respect-

ively. However, the time taken to reach equilibrium was

equal for all the initial dye concentrations, which was 48 h.

This finding is supported by work carried out by Poots et al.

(1976), who reported that the initial concentration of dyes

had only a small influence on the time of contact necessary

to reach equilibrium in the sorption study of Telon Blue by

peat (Keith et al., 1999).

3.2. Effect of dose of sorbent

Although 5 g of barley husk was able to remove a very

high percentage (85% at a Co of 100 mg l� 1) of dyes from

Fig. 1. Percentage of artificial effluent adsorbed by 5 g of barley husk

(1� 4 mm) at concentrations of 50 mg l� 1 –^– , 100 mg l� 1 –&– ,

150 mg l� 1 –~– , 200 mg l� 1 – � – .

Fig. 2. Percentage of artificial effluent adsorbed by 5 g of corncob

(1� 4 mm) at concentrations of 50 mg l� 1 –^– , 100 mg l� 1 –&– ,

150 mg l� 1 –~– , 200 mg l� 1 – � – .

T. Robinson et al. / Environment International 28 (2002) 29–3330

the effluent, it is evident from Fig. 3 that it is definitely not the

most efficient per gram of substrate. By reducing the sorbent

dose to 2 g there is a slight increase in effective dye removal,

and this is increased further to 92% by reducing the dose to

1 g/100 ml� 1. Therefore, 1 g of barley husk was selected as

the sorbent dose, as it bound more dyes per gram of substrate

throughout the duration of the experiment. This dose also had

the highest percentage of dye removal, 92% at a Co of 100mg

l � 1 in comparison to 85% removal by 5 g of barley husk

(Fig. 1). It also had the adsorptive capacity to remove more

dyes at a faster rate in the initial stages. The selection of 1 g

barley husk is significant if the process is to be scaled up,

having a dramatic effect on cost and sheer bulk.

The q values obtained by 5 g of 1� 4 mm corncob

compare well with barley husks at similar adsorbent dose.

For 2 and 1 g doses, the q values are much lower than that

displayed by the barley husk. It is evident from Fig. 4 that

corncobs (1� 4 mm) are not as effective at removing dyes

per gram of substrates as barley husk. In the initial period of

the experiment, 2 g of corncob was more efficient at

removing the dyes but 1 g of corncob had higher q values

from t36 onwards. The difference in the q values of 1 and 2 g

is small until t36 and if scale-up factors such as cost and bulk

are taken into account, the use of a smaller sorbent dose may

be a more economically viable option.

3.3. Effect of particle size

Fig. 5 shows the effect that milling had on the removal of

dyes from an artificial effluent. By reducing the particle size

Fig. 4. Effect of various weights of corncob on removal of artificial effluent (Co 100 mg l� 1). 1� 4 mm; 1 g –~– , 2 g –&– , 5 g –^– .

Fig. 3. Effect of various weights of barley husk on removal of artificial effluent (Co 100 mg l� 1). 1� 4 mm; 1 g –~– , 2 g –&– , 5 g –^– .

T. Robinson et al. / Environment International 28 (2002) 29–33 31

to � 600 mm, and increasing the surface area available for

the binding, it is apparent that more dye molecules are

bound per gram of substrate in the first 5 h. As time

increases and more dye molecules are quickly bound to

the barley husks, the � 600 mm particles quickly become

saturated. There is a period of 14 h, between t10 and t24,

when very little adsorption takes place, with a small increase

in binding towards t50. Increasing the surface area has the

effect of allowing a more efficient removal of dyes in

the first 5 h, but is subsequently quickly saturated. For the

unmilled barley husks, dye binding is reasonably efficient in

the first 5 h. The unmilled barley does not, however, become

quickly saturated, and continues to effectively bind to dye

molecules until t35. Unmilled barley husks allow a steady,

constant removal, ultimately removing more dyes from

solution per gram of substrate.

Fig. 6 illustrates the effect of milling corncob. The

� 600 mm particle size dramatically increased the effective-

ness of corncob for dye removal. The higher surface area not

only allowed an initial period of highly effective dye

removal, but unlike the barley husks, continued to effec-

tively bind with dye molecules at a much more efficient rate.

The smaller particle size allowed a much steeper rate of

effective removal in the first 5 h, in comparison to the

unmilled corncob, before continuing at a steady rate until

t50. Unlike � 600 mm barley husk, corncob does not become

quickly saturated and had the capacity to continue to

steadily bind to dye molecules throughout the duration.

3.4. Kinetics of dye removal

Fig. 7 illustrates how the rate of dye removal increased

with an increase in initial concentration and is shown by

plotting Co vs. the change in concentration (dc), over

change in time (dt). It is evident that the particle size of

� 600 mm, for both substrates, had the higher rate of

removal for the initial concentrations tested. This is sup-

ported by Figs. 5 and 6, which show the rapid rate of dye

removal in the first 5 h by the � 600-mm particle sizes. The

accelerated rate of removal can be attributed to extra binding

sites made available through milling. The 1� 4 mm particle

size for both substrates showed a much slower rate of

removal, as the dye molecules were gradually bound over

a period of time to the larger particle sizes. Although the

� 600-mm particle sizes facilitated rapid binding for barley

husk, they quickly became saturated (e.g., Co 100 mg l� 1)

and further removal occurred at a much slower rate.

4. Conclusions

This study has shown the effectiveness of two widely

available agroindustrial by-products for the removal of dyes

from an artificial effluent. The experimental results show

that 1 g of corncob (� 600 mm) was the most appropriate

weight and particle size for dye removal from the artificial

effluent. This particle size and weight allowed the highest

percentage dye removal (92% in comparison to 62% by

1� 4 mm particle size) at a rapid rate. The 1 g (� 600 mm)

corncob also allowed a higher efficiency in dye adsorption

as more dye per gram of substrate was bound. One gram

(1� 4 mm) of barley husk was selected as the best com-

bination due to its high percentage of dye removal from the

effluent. There was no reduction in the total percentage of

dyes removed by not milling (both particle sizes removed

92% of the dyes). Although the rate of dye binding was not

as rapid as that by � 600 mm particle size, it was nonethe-

less reasonably fast, ultimately producing a higher percent-

age of dye removal at the end of the given retention period.

One gram of barley husk (1� 4 mm) showed an overall

higher efficiency of dye removal through out the experiment

and continued removing dyes at a steady and rapid rate.

The milling of corncob was necessary in order to achieve

better performance for dye removal. For barley husk how-

ever, no milling was required to achieve a high degree of

effective adsorption, and would also reduce the cost of useFig. 5. Effect of particle size on artificial effluent (Co 100 mg l� 1) removal

by barley husk. 1� 4 mm particle size –^– , � 600 mm –&– .

Fig. 6. Effect of particle size on artificial effluent (Co 100 mg l� 1) removal

by corncob. 1� 4 mm particle size –^– , � 600 mm –&– .

T. Robinson et al. / Environment International 28 (2002) 29–3332

on an industrial scale. Future work with barley husk could

incorporate solid-state fermentation technology using white-

rot fungi to simultaneously degrade the dye-adsorbed sub-

strates and enrich the protein content of the fermented mass.

Acknowledgments

T.R. is thankful to the Department of Education,

Northern Ireland (DENI) for a research studentship to

carryout this work towards his PhD award.

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Fig. 7. Rate of artificial effluent removal by 1 g of barley husk (1� 4 mm ~; � 600 mm ^) and 1 g of corncob (1� 4 mm � ; � 600 mm &).

T. Robinson et al. / Environment International 28 (2002) 29–33 33