adsorption of phenol

8/11/2019 Adsorption of Phenol

1/6

IJET: ISSN 1812-7711, Volume 8 Issue 4 2011

841

International J. Eng. Tech 8(4):841-846, December 2011A publication of G-Science Implementation & Publication website: www.gscience.net or www.gurpukur.com

ADSORPTION OF PHENOL FROM AQUEOUS SYSTEM USING RICE STRAW

MOFIZUR RAHMAN1, MD. RAIHAN CHOWDHURY2, SURIA JAHAN3, MD. RAKIB UDDIN4and AHMAD ISMAIL MUSTAFA

5

ABSTRACTAn examination of adsorption of phenol and phenolic compound on Rice Straw is followed by a criticalassessment of low-cost adsorbents. Experiments have been conducted to examine the adsorption of phenol

and phenolic compounds from industrial effluent by using agricultural wastes on Rice Straw and werecarried out for the analysis of adsorption equilibrium capacities using a batch equilibrium technique. Batch

adsorption isotherm studies were carried out under varying experimental conditions of contact time,

operational temperature, adsorbent dose, initial phenol concentration, particle size and pH of phenolsolution. Adsorption equilibrium of Rice Straw was reached within 3 hour for phenol concentration500g/L. Kinetics of adsorption obeyed a first-order rate equation. The suitability of the Freundlich and

Langmuir adsorption models to the equilibrium data were investigated for phenol-sorbent system. Theresults showed that the equilibrium data for all the phenol-sorbent systems fitted the Freundlich model and

Langmuir modal within the concentration range studied. 83.2% removal of phenol were achieved at given

adsorption conditions from aqueous system which could be regenerated by desorption with the help of 1 MNaOH and recovered 95.30% of adsorbed phenol. This study has proven that Rice Straw is a usefulagricultural waste product for the removal of phenol and phenolic compounds from aqueous system. This

study was mainly conducted at the laboratory of Applied Chemistry & Chemical Engineering, University ofDhaka and partial work was done at laboratory of Analytical Research Division, Bangladesh Council ofScientific and Research, during the period of December 2009 to July 2010.

Keywords: Aqueous system, Rice straw, Phenol, Freundlich and Langmuir adsorption model.

INTRODUCTION

Phenol is one of the most abundant organic pollutants in industrial wastewater. It is released to the

environment from industries such as petroleum refining, textile industries, coal tar, steel, tanning,

pesticides, pharmaceuticals, etc. Phenol has attracted public attention due to its presence in groundwater,

rivers and drinking waters. Even in small quantities, phenol causes toxicity and foul odor to the water.

Most countries specify maximum allowable concentration of phenol in effluent to be less than 1 ppm.

Continuous ingestion of phenol for a prolonged period of time causes mouth sore, diarrhoea, excretion of

dark urine and impaired vision at concentration levels 10/240 ppm. Lethal blood concentration for phenol

is around 1.3 g/L. phenols are toxic to several biochemical functions and to fish life. It acts as a substrate

inhibitor in the bio-transformation. World Health Organization (WHO) prescribed a concentration 1 ppb

as the guideline concentration in drinking water(WHO, 1984). Several treatment methods such as chemical

oxidation, biological treatment, wet oxidation, ozonolysis, precipitation, ion exchange, adsorption, electrodialysis and adsorption have been proposed for removing phenol from industrial effluents. However, these

methods have limitations on selective separation and high cost of investment and operation of equipment.

By using agricultural waste, the adsorption of pollutants from aqueous solutions can be more economical

with regard to other similar physico-chemical processes. So, adsorption is an economically feasible

alternative method for removing trace phenol from wastewater. Adsorption is an effective purification and

separation technique used in effluent treatments. Use of agricultural wastes, has many advantages such as

low capital and operating costs, selective removal of phenol and phenolic compounds, adsorbent

regeneration and phenol and phenolic compounds recovery potentiality, rapid kinetics of adsorption and

desorption and no sludge generation (Frcd Gurnham, 1970). The binding mechanisms of phenol by

adsorption could be explained by the physical and chemical interactions between cell wall ligands and

1Department of Applied Chemistry and Chemical Engineering, University of Dhaka, Email: [email protected], 2Department

of Biochemistry & Molecular Biology, University of Dhaka, Email: [email protected],3Department of Pharmacy,

Jahangirnagar University. Email: [email protected], 4Department of Pharmaceutical Chemistry, University ofDhaka, Email: [email protected] and

5Department of Applied Chemistry and Chemical Engineering, University of

Dhaka, Bangladesh. Email: [email protected].


2/6


842

adsorbents by physical adsorption and diffusion of phenol from the bulk solution to active sites of

adsorbents predominantly occurs by passive transport mechanisms and various functional groups such ascarboxyl, hydroxyl, amino and phosphate existing on the cell wall of adsorbents which can bind the

phenol and phenolic compounds (Walter Lorch, 1986). Cost is an important parameter for comparing the

adsorbent materials. Rice straw has been used for wastewater treatment and the potential of their ultimate

usage may be determined by their adsorption capacity, regeneration characteristics and physical propertiesof subsequent products. It was, therefore, thought worthwhile to make a venture in order to develop a very

simple but highly efficient and effective technique for the removal of Phenol from industrial effluents

using Rice Straw. Adsorption techniques are widely used to remove certain classes of pollutants from

wastewater. Phenolic compounds represent one of the problematic groups in wastewater management.Although commercial activated carbon is a preferred adsorbent for phenol removal, its widespread use is

restricted due to the high cost. Economy of our country is yet dependent on agriculture, and rice is the

main crop our country. So considering the socioeconomic condition of our countryour main objective of

this study is to introduce low-cost agricultural waste like as rice straw which could be an effective agent

for industrial effluent treatment to remove phenol and phenolic compounds from the industrial waste.

MATERIALS AND METHODS

Preparation of adsorbent:Straw is an agricultural by-product, the dry stalks of cereal plants, after the grain

and chaff have been removed. Straw makes up about half of the yield of cereal crops such as rice. The rice

has long, slender leaves 50-100 cm long and 2-2.5 cm broad. The small wind-pollinated flowers are

produced in a branched arching to pendulous inflorescence 30-50 cm long. The edible seed is a grain

(caryopsis) 5-12 mm long and 2-3 mm thick. The Rice Straws were carefully collected without any

contamination from local area. After collecting, Rice Straws were treated to make them ready for use. TheRice Straw were dried initially in an oven at about 70C and then ground to fine mesh and the particles of40, 80, 120, 160, 200 mesh size were separated by sieving through standard test sieves.

Reagents and Materials: All the reagents and chemicals used were of Analytical Grade. Phenol, 4-

amino antipyrine was obtained from BDH Chemicals Ltd., Poole England. Potassium Ferricyanide was

obtained from Loba Chemie Pvt. Ltd. India. Stock solution of phenol (1000 ppm) was obtained by

dissolving 0.5 gm phenol in 500 ml double distilled water. Potassium Ferricyanide (8% W/V) Solution

was prepared by dissolving 8.0 gm of potassium ferricyanide in 100 ml double distilled water. And 4-

aminoantipyrine (2%-W/V) Solution was prepared by dissolving 2.0 gm 4- amino antipyrine in 100 mldouble distilled water (American Public Health Association, 1985). The phenol estimation was done by

using Shimadzu UV-VIS 1700 double beam spectrophotometer.

Estimation of phenol by modified method: The 4-aminoantipyrine method gave unsatisfactory result

(Rengaraj et al., 2002). So attempts were made to modify the 4-aminoantipyrine method. Preliminary

experiments showed that phenol does not give any appreciable color with 4-aminoantipyrine in presenceof potassium ferricyanide in acidic medium. But at pH 8.0 phenols gives a deep brownish red color whose

intensity gradually increases up to pH 10.0 and then sharply decreases. This color system was made the

basis for the development of the modified spectro photometric method for the determination of trace

amount of phenol at a pH 10.0 instead of pH 8.0. Absorbance measurements, carried out against reagentblanks, revealed that the absorption maxima are at 500 nm and that the time required for full color

development is 25 minutes. Experimental result revealed that 0.4 mL of 2.0% (w/v) 4-aminoantipyrine

solution is sufficient for the development of maximum color intensity of the system containing 5 ppm

phenol solution. Results of the effect of potassium ferricyanide indicates that 0.5 mL of 8.0% of (w/v)potassium ferricyanide solution is the optimum amount for the development of the maximum color

intensity of the system containing 5 ppm phenol solution. It was also observed that the color intensity

gradually decreases beyond this range. It was found that the modified method was more suitable.

Estimation of standard calibration curve:A standard curve is a graph relating a measured optical density

to concentration of the substance of interest in "known" samples. The standard calibration curve isdrawn by plotting absorbance (on the Y axis) vs. concentration (on the X axis). Result of standard


3/6


843

calibration curve is shown in table (1). Standard curve is determined by the system containing 5 ppm

phenol solution with 0.5 ml potassium ferricyanide solution, 0.4 ml 4amino antipyrine, 5 ml buffersolution (pH 10). The results are graphically represented in fig. (a).

Table 1. Phenol Vs Absorbance.

Phenol variation max, nm Absorbance

1 0.0998

2 0.18883 0.2801

4 500 0.36015 0.47456 0.61117 0.83018 0.90279 0.945410 0.9811

Fig. (a). Standard curve.

Removal of phenol from aqueous solution: The batch experiments were conducted using 2.5 gm of

adsorbent in 250 mL capacity stopper bottles with 100 mL phenol solution. The whole study was

carried out at pH 8.0; at higher pH the texture of the adsorbent is changed. The bottles were then shakenat uniform speed at room temperature using an electric shaker (Cooper, 1985). At predetermined time

intervals the contents were centrifuged and the remaining concentration of phenol in the supernatant

were analyzed spectro-photometrically against respective reagent blank. The bottles containing phenol

of different concentration and the specified pH were shaken for 3 hours to ensure complete saturation.

The amount of phenol adsorbed was determined from the difference between the amount of phenolinitially added and that left after adsorption. The concentration range of phenol adhering to Beer's law

under the conditions of investigation for the system was 0-10 ppm.

RESULTS AND DISCUSSION

Effect of different parameter

i. Effect of contact time variation:The adsorption of phenol on Rice Straw increases with increase ofcontact time up to one hour; afterwards slightly decreases during next hour and then no significant

change are found and attain equilibrium. The removal was very rapid within initial 15 minutes to 1hr.Initially the Rice Straws were dry so they intensively soaked water from solution which is irreversible


4/6


844

process and the phenol and Phenolic compounds got adsorbed on the surface of the Rice Straw which is

a reversible process. Within 3 hr through desorption-adsorption the system reached equilibrium. Thekinetics of phenol adsorption on Rice Straw follows the first-order rate expression (Namasivayam and

Sangeetha, 2004). These results also indicate that the sorption process can be considered very fast

because of the largest amount of phenol adsorbed to the sorbent within the first 60 min of adsorption.

ii. Effect of temperature variation:Temperature is an important parameter for any separation process.

Removal of phenol by Rice Straw was studied at four different temperatures: 30, 35, 45 and 500C. It

was found that adsorption of phenol on Rice Straw increases with increase of the temperature in therange of 30 to 50

0C. Although absorption of phenol is maximum at 50

0C, but all subsequent

experiments were carried out at room temperature. Because it is very difficult to keep constant high

temperature (500C) and shaking is also not possible properly. The intra particle diffusion rate of sorbate

ions into the pores will be intensified as temperature increases, as diffusion is an endothermic process

(Singh and Rawat, 1994). So the adsorption increases with temperature. Therefore, the adsorption

capacity would largely depend on the chemical interaction between the functional groups on the Rice

straw surfaces and the adsorbate and increase with temperature rising.

iii. PHEffect on adsorption:The adsorption of phenol from aqueous solution is dependent on the pH of

the solution, which affects the surface charge of the adsorbent, degree of ionization and speciation of

the adsorbate species. The adsorption of phenol by Rice Straw was studied at various pH values of 4, 7,

8, 9, 10. The adsorbed amount increases with increasing the pH up to pH 8 and start to decrease withincreasing the pH value. This can be attributed to the depending of phenol ionization on the pH value.

The ionic fraction of phenolate ion can be calculated from (Banat et al.,2000).

pH)(pKa10[1

1ions

Obviously,ions

increases as the pH value increased. Accordingly, phenol, which is a weak acid

(pKa=10), will be adsorbed to a lesser extent at higher pH values due to the repulsive force prevailing at

higher pH value (Banat et al., 2000). Also, in the higher pH range phenol forms salts, which readily

ionize leaving negative charge on the phenolic group. At the same time the presence of OH_ ions on the

adsorbent prevents the uptake of phenolate ions (Rengaraj et al.,2002);(Aksu and Yener, 2001). Similarbehavior has been reported by for the adsorption of phenol by activated carbon, and adsorption of

phenol onto bentonite by (William.Cooper, 1985). PHalso affects the surface properties of the sorbent,

i.e., surface charge of the cells used as sorbent. At very low pH values, the surface of the sorbent would

also be surrounded by the hydronium ions, which enhance the phenol interaction with binding site of

the sorbent by greater attractive forces, hence its uptake on polar adsorbent is reduced.

iv. Effect of initial concentration of phenol variation: The equilibrium sorption capacities of the

sorbents increased with increasing phenol concentration while the adsorption yields of phenol showed

the opposite trend. It is evident that initially the number of adsorption sites available is higher and the

driving force for the mass transfer is greater. Therefore the adsorbate reaches the adsorption site with

ease. With the increase of initial concentration, number of active sites becomes less and the adsorbent

becomes crowded inside the particles, thus impeding the movement of the adsorbate. This can beaccounted for the decrease in adsorption rate with increase in concentration. Thus, the initial

concentration provides an important driving force to overcome all mass transfer resistances of phenolbetween the aqueous and solid phases. This would results in higher phenol adsorption (Ahmaruzzaman

and Sharma, 2005). On a relative basis, however, the percentage adsorption of phenol decreases as the

initial phenol concentration increases.

v. Effect of adsorbent dose variation:The amount of adsorbent on the efficiency of adsorption was also

studied. Adsorbent dosage was varied from 0.5gm to 5gm for Rice Straw. The results show that for

removal of 500 mg/L of phenol in 100 ml of solution, a minimum dosage of 2.5 gm of Rice Straw isrequired for 64.1% removal of phenol. This study determines the optimum quantity of Rice Straws. It

was found that adsorption is completed within 5 hr and the percentage of adsorption increases with the


5/6


845

increasing amount of Rice Straw. The highest percentage of adsorption was obtained by using the 2.5

gm of Rice Straw. Therefore, optimum quantity was found to be 2.5 gm which is shown in the figure.The results also clearly indicate that the removal efficiency increases up to the optimum dosage beyond

which the removal efficiency is negligible.

vi. Effect of particle size variation:The effect of particle size variation on the efficiency of adsorption

was also studied. Adsorbent dosage was varied from 40 meshes to 200 meshes for Rice Straw. The

results show that for removal of 500 mg/l of phenol in 100 ml of solution, a minimum dosage of 2.5 gm

of 200 meshes Rice Straw is required for maximum percentage of removal of phenol. The adsorption ofphenol increases with the increasing of mesh size. High mesh size has larger surface area which is the

main reason for increasing of adsorption of phenol on adsorption.

vii. Adsorption isotherm:The batch adsorption experiments were carried out in 100 mL glass bottles

where 2.5 gm of Rice straw and 100 mL of phenol solutions were added. Initial phenol concentrationsolutions ranged from 0.5-5 ppm (pH 8). The bottles were subsequently capped and shaken in a rotary

shaker for 1h at 25C. At the end of the equilibrium period the bottles were taken off the shaker and the

samples were left standing for a while to allow the adsorbent particles to settle. Then the solution is

filtered through glass-fiber filter paper to remove any remaining adsorbent particles. Linear calibration

curves were used to determine the phenol concentrations. The curves were based on standards in the

concentration range from 0.5-10 ppm. A phenol adsorption isotherm was obtained using the batchequilibrium technique reported by (Ahmaruzzaman and Sharma, 2005). Several models have been

published in the literature to describe experimental data of which the most common are the Langmuir

isotherm (Tseng et al.,2003) and the Freundlich isotherm (Arinjay et al., 2003). The Langmuir isotherm is

used to describe single layer adsorption and can be written as Amaxk.cAmaxm

1111

The valueAmaxrepresents the maximum adsorption that can take place in grams of adsorbate per gram

of adsorbent, when c is large relative to the constant k. When m approaches Amax the coverage of the

surface is essentially complete. The Freundlich isotherm in its linearized form can be written as:

log q = log k + 1/n log C, Where, K is a Freundlich constant related to the adsorption capacity (mg/g)

and 1/n is the intensity of adsorption. The values of K and 1/ncan be determined from the intercept and

slope, respectively of linear plot of log q versus log C. The linearized Langmuir and Freundlich

adsorption isotherms of rice straw for phenol are shown in fig. (2) and fig. (3).

Fig. 2. Frendlich isotherm graph. Fig. 3. Langmuir isotherm graph.

Criteria of regeneration

Regeneration studies help elucidates the mechanism of adsorption. From the graph between the pH and

percentage of desorption, the maximum desorption efficiency was determined. 2.5 gm of spent

adsorbent after adsorption at pH 8 was shaken with 100mL of 1M NaOH, HCl, H2SO4, HNO3, KOH for

regeneration which was completed within 60 minute duration respectively. About 95.30%, 91.19%,90.09%, 88.92%, 84.63% of the adsorbed quantity of phenol from the initially present 5 ppm was


6/6


846

desorbed from the samples in a single step respectively. It was then washed with distilled water dried in

oven and was reused in subsequent operations. In this way after recovered samples can be reused in theoperation. It reduces the operation cost and thus may be very useful.

Application on real effluent treatmentTwo industrial effluent samples were collected in a glass bottle with Teflon-lined caps directly from the

outlet of a textile (Bijoy Textile Industries Ltd.) and dyeing Industry (Color Thread Company) located at

Shampur, Kadamtali I/A, Dhaka and 42, Malitola, Dhaka respectively. The sample was immediately

brought to the laboratory to be placed in cool place. Before analysis, the effluents were decanted off andfiltered to remove some waste particle contained in the effluent and kept for further usage. Effluents were

then treated as method discussed above. Rice Straw is effectively removed 74.15%, 75.05% of phenol and

phenolic compounds by treating with Rice Straw. The adsorbed amount of phenol and phenolic compoundwas recovered with 100 ml of 1 M NaOH and the percent recovery was found to be 96.76%, 97.13%.

CONCLUSION

Wastewater containing phenolic compounds presents a serious discharge problem due to their poor

biodegradability, high toxicity and ecological aspects. Phenolic compounds are frequent contaminantsof ground water because of their wide use in industrial sectors. Thus all surface water must be

considered as potentially dangerous and should be properly treated before ingestion. Activated carbons

are extensively used for wastewater treatment, its use is often limited due to its high cost and difficult

preparation methods whereas rice straw is widely abundant agricultural waste can be effectively used

for phenol removal from aquatic solution which can be regenerated and reused. Thus research workregarding effluent is very important in context of our country, it may be concluded from the

experimental results that rice straw is an excellent adsorbent for phenol from aqueous system.

REFERENCES

Ahmaruzzaman, M. and D. K. Sharma. 2005. Adsorption of phenols from wastewater, J. Colloid Interface Sci. 287:14.

Aksu, Z. and J. Yener. 2001. A comparative adsorption/boisorption study of Monochlorinated [Ph9]. 21-31 (Enl).

American Public Health Association, 1985. Standard methods for the examination of water and waste waters.

Sixteenth edition, pp. 556,558-560.

Arinjay, K., K. Shashi and K. Surendra. 2003. Adsorption of resorcinol and catechol on granular activated carbon:equilibrium and kinetics, Carbon 41:3015.

Banat , F. A., B. Al-Bashir, S. Al-Asheh and O. Hayajneh, 2000. Adsorption of phenol by bentonit. EnvironmentalPollution, 107: 391-398.

Cooper, W. 1985. Chemistry in water analysis vol. 2, p. 573.Frcd Gurnham, C. 1970. Industrial waste water Control, pp. 1, 2, 3, 8, 325, 326.

Namasivayam, C. and D. Sangeetha. 2004. Equilibrium and kinetic studies of adsorption of phosphate onto ZnCl2Interface Sci. 280 (2): 359-365.

Rengaraj, S., M. Seuny-Hyeon and R. Sivabalan. 2002. Agricultural solid waste for the removal of organics:

adsorption of phenol from water and wastewater by Palm seed. 22: 543-548.

Singh, B. K. and N. S. Rawat. 1994. Comparative sorption equilibrium studies of ionic phenols on fly ash and

impregnated fly ash (1994) 307315.

Tseng, R. L., F.C. Wu and R.S. Juang. 2003. Liquid phase adsorption of dyes and phenols using pine wood based

activated carbon, Carbon 41: 487.

Walter Lorch, 1986. Hand book of water purification, pp. 136-138.

WHO, 1984. Guidelines for drinking water Quality vol.1. Recommendation World Health Organization, Geneva.

William.Cooper, 1985. Chemistry in water analysis vol-2. pp. 573.

adsorption of phenol

Documents