Removal of Chromium on Polyalthia longifolia Leaves Biomass

International Journal of Phytoremediation, 13:410–420, 2011Copyright C© Taylor & Francis Group, LLCISSN: 1522-6514 print / 1549-7879 onlineDOI: 10.1080/15226511003753995

REMOVAL OF CHROMIUM ON POLYALTHIA LONGIFOLIALEAVES BIOMASS

Jamil Anwar,1 Umer Shafique,1 Waheed-uz-Zaman,1

Zaib un Nisa,1 Munawar Ali Munawar,1 Nadia Jamil,2

Muhammad Salman,1 Amara Dar,1 Rabia Rehman,1

Jawwad Saif,1 Humaira Gul,1 and Tanzeel Iqbal11Institute of Chemistry, University of the Punjab, Quaid e Azam Campus, Lahore,Pakistan2Earth and Environmental Sciences, University of the Punjab, Quaid e AzamCampus, Lahore, Pakistan

Adsorption is an environmental friendly process for removal and/or recovery of heavy metalsfrom wastewater. In recent years, it has been substantiated as a popular technique to treatindustrial waste effluents, with significant advantages. In this work, batchwise removal ofchromium (III) ions from water by Polyalthia longifolia leaves was studied as a function ofadsorbent dose, pH, contact time, and agitation speed. Surface characteristics of the leaveswere evaluated by recording IR spectra. The Langmuir, Freundlich, and Temkin adsorptionisotherms were employed to explain the sorption process. It was found that one gram of leavescan remove 1.87 mg of trivalent chromium when working at pH 3.0. It has been concludedthat Polyalthia longifolia leaves can be used as cost-effective and benign adsorbents forremoval of Cr(III) ions from wastewater.

KEY WORDS: adsorption isotherms, biosorption, chromium, Polyalthia longifolia, watertreatment, wastewater

1. INTRODUCTION

The production of heavy metals has increased rapidly since the industrial revolution(Ayres, 1992). Heavy metals can enter an aqueous ecosystem either from industrial ac-tivities like electroplating, battery manufacturing, and metallurgical processes or throughacid rain breaking down soil and releasing heavy metals into streams, lakes, and rivers(Gundogdua et al., 2009). Because of their non-biodegradability and high toxicity, heavymetals pose a serious threat to the environment (Anwar et al., 2009). Industrial sourcesof chromium are electroplating, leather tanning, mining, steel, and pigment manufacturing(Afkhami and Conway, 2002). Chromium was included in the list of 13 hazardous metals(antimony, arsenic, beryllium, cadmium, chromium, copper, lead, mercury, nickel, sele-nium, silver, thallium, and zinc), made by United States Environmental Protection Agencyin 1978 (Ramos et al., 2002). In 2004, US-EPA recommended the maximum acceptableconcentration of chromium in drinking water as 0.1 mg/L.

Address correspondence to Umer Shafique, Institute of Chemistry, University of the Punjab, Quaid e AzamCampus, Lahore 54590, Pakistan. E-mail: [email protected]

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REMOVAL OF CHROMIUM ON POLYALTHIA LONGIFOLIA LEAVES BIOMASS 411

Conventional removal methods (reverse osmosis, chemical precipitation, solvent ex-traction, filtration, ion exchange, electrodialysis, electroflotation, chemical oxidation andreduction, and coagulation) for chromium and other heavy metals have several disad-vantages like incomplete metal removal, high operational cost, less sensitivity, expensivereagents and energy needs and generation of toxic waste (Aksu, 2002; Volesky, 2001). Onthe contrary, biosorption is a rapid, reversible, economical, and eco-friendly technologyused for removal of heavy metals (Ahuja et al., 1999; Kovacevic et al., 2000).

The present work explores the potential of use of untreated Polyalthia longifolia leavesas metal sorbent for chromium (III) from water. Polyalthia longifolia (family: annonaceae)is a lofty, evergreen tree found in the subcontinent, commonly planted as an ornamentalplant and for its effectiveness in alleviating noise pollution (Verma et al., 2008). Theweeping branches of this 25-foot tall tree gives it a narrow columnar shape. Glossy green,long, narrow leaves have attractive wavy edges. The study includes an evaluation of theeffects of various factors on sorption such as pH of the solution, time, initial mass of sorbentand agitation speed. The Langmuir, Freundlich, and Temkin adsorption models were usedto explicate the adsorption equilibrium.

2. MATERIALS AND METHODS

2.1. Biosorbent

The green leaves of Polyalthia longifolia (3 years old) were collected from Universityof the Punjab, New Campus, and Lahore, Pakistan. Leaves were washed with distilled waterthoroughly to remove dirt particles. Afterwards, they were oven dried and ground to 60-mesh (ASTM) particle size. The powdered leaves were used as biosorbent without anychemical treatment. Fourier transforms infrared spectroscopy (Perkin Elmer Spectrum RXI) was employed to characterize the surface of Polyalthia longifolia leaves.

2.2. Stock Solution and Standards of Chromium

Stock solution of 1000 mg/L concentration was prepared by dissolving appropriateamount of chromium chloride (AnalaR) in distilled water. Standard solutions of the requiredconcentrations were prepared by successive dilution of the stock solution.

2.3. Equipment and Apparatuses

To adjust pH, HCl (0.1 mol/L) and NaOH (0.1 mol/L) were added while pH wasmeasured with digital pH-meter (HANNA, 8417). Atomic absorption spectrophotometer(Perkin Elmer, AAnalyst 100) equipped with chromium hollow cathode lamp was used formetal estimation. The glassware used was washed with deionized water and oven driedbefore use. After adsorption, contents of the flasks were filtered and filtrates were subjectedto atomic absorption for determination of metal.

2.4. Biosorption Experiments

Biosorption experiments were performed in a top-loaded orbital shaker with achromium solution of 50 mg/L (50 mL). Effects of four features: adsorbent dose; pH;

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412 J. ANWAR ET AL.

contact time and agitation speed were studied on adsorption of Cr(III) by Polyalthia longi-folia leaves. To study the effect of one feature all other were kept constant and only thatparameter has been changed gradually. The effect of the biosorbent dose was studied byvarying the dose from 0.50 to 5.0 g. The effect of the pH was studied by varying the pHfrom 1 to 8, biosorption time, 5 to 50 min and agitation speed in the range 50 to 300 rpm.

2.5. Adsorption Isotherms

The Langmuir isotherm model (Langmuir, 1916) was used to find out maximumchromium (III) sorption by Polyalthia longifolia leaves. The Langmuir isotherm can beexpressed as:

Q = Q max .b.Ce

1 + b.Ce, (1)

where Q (mg/g) is metal uptake; Qmax (mg/g) marks monolayer sorption capacity ofPolyalthia longifolia leaves; b (L/mg) is related to energy of sorption; and Ce (mg/L) isconcentration of Cr (III) in solution at equilibrium.

The Freundlich isotherm model (Freundlich, 1906) is represented by the followingequation:

Q = KC1/n

F , (2)

where K (mg/g) is Freundlich constant related to adsorption capacity of adsorbent and n isFreundlich parameter related to adsorption intensity.

The Temkin isotherm model (Aharoni and Ungarish, 1977) is represented by thefollowing equation:

Q = RT

bT

ln(KT Ce), (3)

where R (8.314 J/K.mol) is gas constant; T (303 K) is temperature; and bT (kJ/mol) and KT

(mg/g) are Temkin constants.

2.6. Safety Measures

Waste adsorbent has been disposed properly since chromium (III) is not degrad-able naturally. The residuals (contaminated Polyalthia longifolia leaves) were placed in acontainer marked as ‘hazardous waste’ and sent to regional landfill.

3. RESULTS AND DISCUSSION

3.1. FTIR Characterization

The first step was the preliminary characterization of Polyalthia longifolia leaves toconfirm the presence of groups like –OH, –CO and –COOH that can be the possible activecenters for Cr uptake. The peaks were observed at 3340, 2919, 2851, 2359, 2340, 1732,1615, 1514, 1237, 1159, 1019, 577 and 516 cm−1. A band, fairly broader, at 3340 cm−1

was because of the presence of hydroxyl groups. Peaks at 2919 and 2851 cm−1 wereappeared because of C–H (Pasquali and Herrera, 1997). Peaks at 2359 and 2340 cm−1 were

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REMOVAL OF CHROMIUM ON POLYALTHIA LONGIFOLIA LEAVES BIOMASS 413

indicatives of triples (C C and C N). Peaks at 1732 and 1615 cm−1 were characteristicsof carbonyl groups of carboxylic acids. 1514 cm−1 was indicative of existence of esters.1237 and 1159 cm−1 pointed out the presence of C–O, C–H or C–C of carboxylic groups.Region below 1000 cm−1 cannot be used to represent any particular group as it correspondsto the complex interacting vibration.

3.2. Effect of Concentration of Adsorbent

The effect of adsorbent concentration on the chromium (III) removal was studiedby agitating 50 mg/L solution of chromium (50 mL) with 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5,4.0, 4.5, and 5.0 g sorbent dose, at constant temperature (30◦C) and speed (150 rpm). Theresults are shown in Figure 1. Removal of metal cations increased with the sorbent dose,which can be assigned to the increased surface area and more sorption sites. The maximumadsorption took place with 2 g leaves biomass. However, there was a decrease in percentageremoval with a further increase in the sorbent mass because of the split in the concentrationgradient between solute concentrations and on the sorbent surface. Also, at higher sorbentdoses, interaction between metal and sorbent particles become less dominant in comparisonto intra-sorbent interaction, causing assemblage of sorbent and decreasing surface area formetal uptake. Experiments have also pointed out that at higher sorbent concentration lesstime is consumed in getting equilibrium.

35

40

45

50

55

60

65

70

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

Adsorbent Dose (g / 50mL)

Per

cen

tag

e A

dso

rpti

on

Figure 1 Effect of adsorbent dose (0.5–5 g) on percentage adsorption of chromium (50 mg/L); volume, 50 mL;pH, 7; agitation speed, 150 rpm; temperature, 30◦C; and time, 25 min.

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3.3. Effect of Contact Time

As illustrated in Figure 2, the chromium (III) adsorption increased rapidly in startwith time. The information acquired for the biosorption of chromium (III) on Polyalthialongifolia leaves showed that a contact time of 15 min is enough to achieve equilibriumand the adsorption did not change significantly with a further increase in contact time.

3.4. Effect of pH

One of the most important parameters that affect biosorption of metal ions fromaqueous solutions is the pH of the system. FT-IR analysis has pointed out that Polyalthialongifolia leaves contain ionizable groups (carboxyl and hydroxyl groups) which make itliable to the influence of the pH. As shown in Figure 3, the uptake of chromium (III) wasfavored at acidic pH (< 4). The maximum removal occurred at pH 3.0; thereafter, there was asharp decline in percentage adsorption with rising pH. After pH 8.0, chromium precipitatedout from solution as Cr(OH)3 making the adsorption study impossible. The pH dependenceis related to the type and ionic state of functional groups present on the adsorbent and stateof chromium in solution (Mohanty et al., 2006; Malik et al., 2005). The adsorption resultedas attractive interactions between the positive chromium ions: Cr(OH)2+, Cr(OH)2

+ andCr3+ and carboxylic, hydroxo- and hydroxy–carboxylic groups of Polyalthia longifolialeaves. At pH 3.0 or less, Cr3+ is a dominating specie but as the pH rises, concentration

50

52

54

56

58

60

62

64

66

68

0 5 10 15 20 25 30 35 40 45 50

Time of Contact (min)

Per

cen

tag

e A

dso

rpti

on

Figure 2 Effect of time (5–50 min) on percentage adsorption of chromium (50 mg/L); volume, 50 mL; pH, 7;agitation speed, 150 rpm; temperature, 30◦C; and adsorbent dose, 2 g.

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REMOVAL OF CHROMIUM ON POLYALTHIA LONGIFOLIA LEAVES BIOMASS 415

50

55

60

65

70

75

80

85

90

95

0 1 2 3 4 5 6 7 8

pH

Per

cen

tag

e A

dso

rpti

on

Figure 3 Effect of pH (1–8) on percentage adsorption of chromium (50 mg/L); volume, 50 mL; agitation speed,150 rpm; temperature, 30◦C; adsorbent dose, 2 g; and time, 15 min.

of Cr3+ gradually decreases while that of Cr(OH)2+ and Cr(OH)2+ increases (Bernardoa

et al., 2009). Thus, Cr3+ is mainly accountable for adsorption at pH 3.0, where nearly 90%of chromium was adsorbed. At pH 1 and 2, excess in concentration of protons resulted incompetition with Cr(III) for available sites, resulting in fewer adsorption. Besides, surfacewill be positive at lower pH and will not favor the adsorption of positively charged ions.Above pH 3.0, there was a decrease in adsorption probably because of decrease in thenumber of Cr3+ ions as it hydrolyzed Cr3+ to Cr(OH)2+ and Cr(OH)2

+. The presence ofthese chromic species with less charge resulted in a decrease in the protons released evenwhen the uptake increases. The pH dependency of adsorption suggests that Cr(III) ions areadsorbed according to the ion-exchange mechanism (Rengaraj et al., 2003; Yu, 2003) asgiven in the following equations:

3(RCOOH) + Cr3+ ↔ Cr(RCOO)3 + 3H+ (1)

3(ROH) + Cr3+ ↔ Cr(RO)3 + 3H+ (2)

3.5. Effect of Agitation Speed

Figure 4 explains the influence of shaking speed on adsorption of Cr(III). Generally,an increase in shaking speed increased the adsorption. Slow speed, instead of spreadingthe sorbent in the solution, assembled it and many uptake sites were buried. Therefore, at a

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416 J. ANWAR ET AL.

85

86

87

88

89

90

91

25 50 75 100 125 150 175 200 225 250 275 300

Agitation Speed (rpm)

Per

cen

tag

e A

dso

rpti

on

Figure 4 Effect of agitation speed (50–300 rpm) on percentage adsorption of chromium (50 mg/L); volume, 50mL; pH, 3.0; temperature, 30◦C; adsorbent dose, 2 g; and time, 15 min.

low speed, removal occurred by top layers while underneath layers do not take part in theprocess as there was no contact with metal (Anwar et al., 2009). Best results were obtainedat a speed of 100 rpm, later, the kinetic energy of Cr3+ as well as of the adsorbent particlesincreased to a level that they collide with each other rapidly resulting in detachment ofloosely bound ions. Besides, they did not get proper time to interact with one another. Sameobservation was reported in another work as well (Bai and Abraham, 2003; Anwar et al.,2009).

3.6. Adsorption isotherms

Adsorption isotherms were studied with the initial Cr(III) concentration varied from30 to 80 mg/L. Table 1 is showing results of Langmuir, Freundlich, and Temkin isothermanalyses, calculated for adsorption of chromium (III) at pH 3.0, temperature 30◦C andcontact time of 15 min. Langmuir, Freundlich, and Temkin isotherms are shown in Fig. 5,6, and 7, in that order. Linear plots were gained for all the three models pointing out thatadsorption of Cr(III) by Polyalthia longifolia leaves can be efficiently explained by theseisotherms. Correlation coefficients of 0.99, 0.98, and 0.98 were attained for Langmuir,Freundlich, and Temkin modes, respectively. Slopes and intercepts of lines were used tocalculate the related parameters.

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REMOVAL OF CHROMIUM ON POLYALTHIA LONGIFOLIA LEAVES BIOMASS 417

Table 1 Langmuir, Freundlich, and Temkin isotherm constant for adsorption of Cr(III) on Polyalthia longifolialeaves

Langmuir isotherm parameters

Slope Intercept R2 Qmax (mg/g) b (dm3/mg)

7.59 0.53 0.99 1.87 0.07

Freundlich isotherm parameters

Slope Intercept R2 K (mg/g) n

0.51 0.04 0.98 0.23 1.93

Temkin isotherm parameters

Slope Intercept R2 KT (mg/g) bT (kJ/mol)

2.12 0.66 0.98 1.36 1.19

Langmuir isotherm is probably the most widely applied model for adsorption. Itconsiders the adsorption energy of each molecule is the same, independent of the surface ofmaterial and there are no interactions between the molecules (Correa and Becerril 2009).As provided in Table 1, maximum adsorption capacity, Qmax, corresponding to completemonolayer coverage is 1.87 mg of Cr(III) per gram of Polyalthia longifolia leaves. Theadsorption coefficient, b, is related to apparent energy of sorption for which the value is0.070. When the adsorption capacity was compared with those of some other adsorbents,

0.6

0.8

1.0

1.2

1.4

1.6

1.8

0.0000 0.0500 0.1000 0.1500 0.2000

1/Ce

1/Q

Figure 5 Langmuir adsorption isotherm for Cr(III) on Polyalthia longifolia leaves, volume, 50 mL; pH, 3.0;temperature, 30◦C; adsorbent dose, 2 g; time, 15 min; and agitation speed, 100 rpm.

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418 J. ANWAR ET AL.

Table 2 Comparison of adsorption capacity of Polyalthia longifolia leaves with previous adsorbent

Adsorbent Qmax (mg/g) Reference

Waste Tea 1.55 Orhan and Buyukgungor 1993Wall astonite 0.52 Sharma 2003Bagasse 0.03 Rao et al. 2002Saw dust 3.61 Baral et al. 2006Brown coal 0.1–0.3 Godea and Pehlivan 2005Polyalthia longifolia leaves 1.87 Present study

Polyalthia longifolia leaves have shown sufficient potential for removal of Cr(III) (Table2). Although, value was not high in comparison to conventional ion exchange resins, it issuitable for effluents containing relatively less chromium (III) ions.

Freundlich isotherm for Cr(III) on Polyalthia longifolia leaves is shown in Fig. 6. Fre-undlich model accounts for adsorption intensity of the adsorbate on adsorbent. Adsorptionintensity of metal cations on biosorbent is provided by the factor ‘n’. For Cr(III), the value is1.93, as mentioned in Table 1. Value of n in the range 1–10 stands for favorable adsorption.KF (final adsorption capacity), as calculated from Freundlich isotherm is 0.23 mg/g.

Temkin isotherm can be used to evaluate potential of adsorbent. It is presented in Fig.7. Features given in Table 1 depict that bT, heat of sorption, is 1.19 kJ/mol for adsorptionof chromium (III) on Polyalthia longifolia leaves. A value less than 8 points out weakinteraction between metal and sorbent (Anwar et al., 2009). Process, as suggested by bT,can be expressed as physiosorption. KT is another Temkin parameter, somewhat similar toQmax of Langmuir isotherm. The value is 1.36 mg/g.

-0.3

-0.2

-0.2

-0.1

-0.1

0.0

0.1

0.1

0.2

0.0000 0.5000 1.0000 1.5000 2.0000

Log Ce

Lo

g Q

Figure 6 Freundlich adsorption isotherm for Cr(III) on Polyalthia longifolia leaves, volume, 50 mL; pH, 3.0;temperature, 30◦C; adsorbent dose, 2 g; time, 15 min; and agitation speed, 100 rpm.

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1.5

1.7

1.9

2.1

2.3

2.5

2.7

2.9

3.1

3.3

3.5

0.5000 0.7000 0.9000 1.1000 1.3000 1.5000

ln Ce

Q

Figure 7 Temkin adsorption isotherm for Cr(III) on Polyalthia longifolia leaves, volume, 50 mL; pH, 3.0;temperature, 30◦C; adsorbent dose, 2 g; time, 15 min; and agitation speed, 100 rpm.

4. CONCLUSION

Polyalthia longifolia leaves were used to remove Cr(III) from wastewater. Adsorptionequilibrium was gained within a short period of time (15 min). Adsorption was favored atpH 3.0 while ideal shaking speed was 100 rpm for 50 mL solution. Langmuir, Freundlich,and Temkin models were used to explain the sorption phenomenon effectively. It was foundthat one gram of leaves can remove 1.87 mg of trivalent chromium (III) when working atpH 3.0. Heat of sorption, as evaluated by Temkin isotherm was 1.19 kJ/mol. Isothermspointed out that adsorption of Cr(III) on Polyalthia longifolia leaves is favorable whenworking under optimum conditions. The present study can be used to infer that instead ofchemicals, non-hazardous materials like Polyalthia longifolia leaves can be used as heavymetal removers from wastewaters and industrial effluents to overcome water pollution.

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