Adsorption of copper on Raw, and Activated Hevea brasiliensis

Ashwin Dhanasekar, Michael Angelo MirandaSri Venkateswara College of Engineering, TN

INTRODUCTIONThe contamination of water by toxic

heavy metals through the discharge of industrial waste water is a world wide environmental problem.

Heavy metals such as lead, cadmium, copper, arsenic, nickel, chromium, zinc and mercury have been recognized as hazardous heavy metals.

Adsorption based process offer more Adsorption based process offer more reliable and more efficient removal of reliable and more efficient removal of complex inorganic and organic complex inorganic and organic materials than many other conventional materials than many other conventional treatment methods.treatment methods. The present endeavour has been The present endeavour has been contributed to the utilization of the contributed to the utilization of the relatively common, cheap and thrown relatively common, cheap and thrown away waste rubber wood sawdust as a away waste rubber wood sawdust as a raw material for the production of raw material for the production of activated carbon and using the same as activated carbon and using the same as an adsorbents for removal of metal ions an adsorbents for removal of metal ions from waste water. from waste water.

SCOPE AND OBJECTIVE OF THE PRESENT WORK

To identify the prospects of using low cost substance as raw materials for the production of adsorbents for removing heavy metals such as copper, cadmium, nickel, chromium, zinc, lead, cobalt etc from wastewater.

To produce activated carbon from rubber wood sawdust by chemical activation method using phosphoric acid as activating agent.

Characterization of adsorbents by means of Iodine number, Methylene Blue number, Methyl violet number, surface area, SEM photographs etc.

To carry out the batch adsorption process for To carry out the batch adsorption process for removing copper ions from synthetic removing copper ions from synthetic wastewater onto adsorbentswastewater onto adsorbents

To obtain the kinetic data and equilibrium data To obtain the kinetic data and equilibrium data in batch system by studying the effects of in batch system by studying the effects of different experimental parameters such as different experimental parameters such as agitation time, initial concentration of metal agitation time, initial concentration of metal ions, the dosage of activated carbon, particle ions, the dosage of activated carbon, particle size, temperature and pH on adsorption size, temperature and pH on adsorption capacitycapacity..

Adsorbent

Raw adsorbentActivated carbon

Acid ActivationBase Activation

PREPARATION OF ACTIVATED CARBON

TYPES OF ACTIVATIONPhysical ActivationChemical Activation

CHEMICAL ACTIVATION The activating agents are

Phosphoric acidSulphuric acidZinc ChloridePotassium hydroxide

CHARACTERIZATION OF ADSORBENTS

Adsorbent Iodine number(mg g-1)

Methylene blue

number (mg g-1)

Methyl violet

number(mg g-1)

Specific Surface

area(m2 g-1)

RHB 635.21 85 40 754.82

ACHB 756.12 170 105 971.28

RSDRSD

ACHBACHB

BATCH ADSORPTION STUDIES Adsorption Kinetics• Pseudo first order model• Pseudo second order modelAdsorption Isotherms• Langmuir isotherm• Freundlich isothermThermodynamic Parameters

EFFECT OF CONTACT TIME ON ADSORPTION CAPACITY

EFFECT OF INITIAL METAL ION CONCENTRATION ON ADSORPTION CAPACITY

0

1

2

3

4

0 100 200 300 400

Time (min)

Ad

so

rpti

on

Cap

acit

y (m

g/g

)

RHB

ACHB

0

1

2

3

4

5

6

7

0 20 40 60Initial Concentration (mg/L)

Ad

sorp

tion

Cap

acit

y (m

g/g)

RHB

ACHB

EFFECT OF ADSORBENT DOSAGE ON ADSORPTION CAPACITY

EFFECT OF TEMPERATURE ON ADSORPTION CAPACITY

0123456

0 0.5 1 1.5Adsorbent Dose (g/100 mL)

Ad

sorp

tion

Cap

acit

y (m

g/g) RHB

ACHB

0

1

2

3

4

5

290 300 310 320 330Temeprature (K)

Ad

sorp

tion

Cap

acit

y (

mg/

g) RHB

ACHBThe effect of temperature on the adsorption equilibrium were investigated under isothermal conditions in the temperature range of 20 – 50 oC.

0

1

2

3

4

5

0 5 10 15

pH

Ad

so

rpti

on

Ca

pa

cit

y

(mg

/g) RHB

ACHB

EFFECT OF PH ON ADSORPTION CAPACITY

ADSORPTION KINETICS

KINETIC MODELS Pseudo–First Order Equation ln(qe – qt) = ln qe – k1t

The values of qe and k1 are obtained by

plotting a graph of ln(qe– qt) Vs t.

Pseudo–Second Order Equation t / qt = 1 / ( k2 qe

2) + t / qe

The values of k2 and qe can be determined by plotting t / qt Vs t.

KINETIC CONSTANTS FOR THE ADSORPTION OF COPPER IONS

Adsor-bents

Pseudo first order model

Pseudo second order model

qe (expt.) (mg g−1)qe

(cal)(mg g−1)

K1

(min−1

)

R2 K2

( g mg−1

min−1)

qe

(cal) (mg g−1)

R2

RHB 1.54 0.0257

0.9519

0.07 2.3585

0.9985 2.3183

ACHB 1.3429

0.0191

0.8294

0.099 3.4095

0.9996 3.3991

ISOTHERM MODELS Langmuir model Ce/qe = 1/Xmb + Ce/Xm

Hence a plot of Ce/qe Vs Ce should be a straight line with a slope 1/Xm and intercept as 1/Xmb.

Freundlich model qe = Kf Ce (1/n)

or lnqe = lnKf + 1/n lnCe

A plot of lnqe Vs lnCe should be a straight line with a slope 1/n and intercept lnKf.

ADSORPTION ISOTHERMS

ISOTHERM CONSTANTS FOR THE ADSORPTION OF COPPER IONS

Adsorbents

Langmuir constants Freundlich constants

Xm(mg/

g)

b R2 n K

(mg/g)

R2

RHB 8.1103

0.0507

0.9768 1.4689

0.5465 0.9997

ACHB 8.3692

0.2153

0.9979 1.7816

1.6467 0.9748

The thermodynamic properties such as standard Gibbs free energy (∆Go), standard enthalpy change(∆Ho) and standard entropy change (∆So) were calculated using the following equation.

∆Go = -RT ln Kc

ln Kc = (CBe/CAe)

The standard enthalpy (∆H˚) and entropy (∆S˚) of adsorption were determined from the Van’t Hoff equation,

ln Kc = (∆S˚ /R) – (∆H˚ / RT)

T(K)

RHB ACHB

∆G˚(kJ mol-

1)

∆H˚(kJ mol-

1)

∆S˚(kJ mol-1

K-1)

∆G˚(kJ mol-

1)

∆H˚(kJ mol-

1)

∆S˚(kJ mol-1

K-1)

293

-0.3219

23.68 0.0814

-9.0212

-71.12 -0.2151

303 -0.8088

-4.3651

313 -1.5051

-3.9583

323 -2.8379

-2.1111

THERMODYNAMIC PARAMETERS FOR THE ADSORPTION OF COPPER ION

CONCLUSION

The Hevea brasiliensis saw dust which is an agricultural waste was found to be a very good adsorbent for the removal of copper from aqueous solution.

The surface morphology involved in all the adsorbents were determined by analyzing through SEM. Adsorption of Cu (II) on RHB and ACHB as been shown to depend significantly on the contact time, pH, initial concentration, dosage and temperature.

Among the kinetic models tested, the adsorption kinetics was best described by the pseudo second order equation.

The adsorption process is endothermic for RHB and exothermic for ACHB. Electrostatic attraction in addition to ion-exchange might be involved in the adsorption of copper ions onto MHB which showed better adsorption capacity when compared to ACHB, CAC and RHB.

The study revealed that this adsorbent is inexpensive, indigenous, easily available material and it can be used for the removal of copper in industrial effluents.

Finally, we can conclude that ACH can be used as a low cost alternate adsorbent for the removal of metal-containing effluents.

Guided by

• Dr Lima Rose Miranda • Ms M Helen Kalavathy

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