Equilibrium, Kinetic and Thermodynamic Studies on ion of Copper and Zinc From Mixed Solution by Erythrina Variegata Oriental Is Leaf Powder

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EQUILIBRIUM, KINETIC AND THERMODYNAMIC STUDIES ON

BIOSORPTION OF COPPER AND ZINC FROM MIXED SOLUTION BY

Erythrina variegata orientalis LEAF POWDER

Document by: Bharadwaj

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ABSTRACT

The aim of the present investigation is to explore the feasibility of biosorption for the

removal of copper and zinc from aqueous Cu-Zn mixed solution using freely andabundantly available plant based material Indian coral ( Erythrina variegate orientalis)

leaf powder. The effects of agitation time, biosorbent size and dosage, initialconcentration of Cu-Zn in mixed solution, pH and temperature of the mixed solution on

biosorption are determined. Batch investigations indicate that biosorption of Cu-Zn

mixture is gradually increased with increase in pH from 1 to 6 (38.25 mg/g to 44.77mg/g). The biosorption of Cu-Zn mixture is increased from 86.3 to 91.9 % (86.27 to

45.93 mg/g) with increase in biosorbent dosage from 1 to 2 g/L. 91.9 % (45.93 mg/g) of

Cu-Zn mixture is removed from the mixed solution containing 100 mg/L of Cu and Zn

agitated with 2 g/L of 45µ m size adsorbent for an equilibrium agitation time of 30 min.

The experimental data are well described by Langmuir (R 2=0.99), Freundlich (R 2=0.98)

and Temkin (R 2

=0.98) isotherms. The sorption studies follow the second order rateexpression (R 2 = 0.99) and rate constant is 9.39 g/mg-min. The biosorption is found toincrease with decrease in temperature of the mixed solution. From the thermodynamic

parameters, sorption is found to be exothermic and reversible.

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Introduction

Land, water and air are the three precious gifts of nature to mankind. Mankind

has a gift to live, and that should be of a good quality free of squalor, disease and

deprivation. An important factor for quality of life is the environment in which manexists. Environmental health depends on air quality, water quality, nutrition levels,

surroundings, industrial susceptibility and climatic conditions. Enhanced industrial

activity during recent decades has led to the discharge of unprecedented volumes of

waste water, which is a serious cause of environmental degradation [1]. Heavy metalsdue to their high toxicity, pose a serious thereat to biota and the environment [2]. Heavy

metals, such as lead, copper, zinc, cadmium and nickel are among the most toxic

pollutants present in marine, ground and industrial waste waters. In addition to their

toxicity effects even at low concentrations, heavy metals can accumulate throughout thefood chain, which leads to serious ecological and health hazards as a result of their

solubility and mobility [3]. Although copper and zinc are essential trace elements, highlevels can cause harmful health effects.

Copper is also toxic to a variety of aquatic organisms, even at low concentrations

[4]. The excessive intake of copper results in its accumulation in the liver and producesgastrointestinal problems, kidney damage, anemia and continued inhalation of copper –

containing sprays is linked with an increasing lung cancer among exposed workers [5].

One metal ion which is often released into the environment through industrial activities atconcentrations of physiological and ecological concern is zinc. In the Dangerous

Substances Directive (76/464/EEC) of the European Union, zinc has been registered as

list 2 dangerous substances with environmental quality standards being set at 40 µ g/L

for estuaries and marine water and at 45-500 µ g/L for fresh water depending on water

hardness. Zinc is widely used in coating iron and other metals, in wood preservatives,

catalysts, photographic paper, and accelerators for rubber vulcanization, ceramics,textiles, fertilizers, pigments and batteries [6] and as a consequence it is often found in

the waste water arising from these processes.

The commonly used procedures for removing metal ions from waste water include chemical precipitation, ion exchange, membrane separation, reverse osmosisi,

evaporation and electro dialysis [7]. However, the application of these methods is often

limited due to their inefficiency, high capital investment/operational costs. Though ion-exchange resins and activated carbons are efficient in the removal of metals with high

uptake capacities, their utilization may be prohibitively costly for treating large volumes

of waste water [6].

Biosorption is a fast and reversible reaction of th heavy metals with biomass [8].

Biosorption can be defined as the ability of biological materials to accumulate heavymetals through metabolically mediated or physico chemical pathways of uptake [9]. The

2



term ‘biosorbent’ includes the usage of dead biomass (such as fiber, peat and wool) as

well as living plants and bacteria as sorbents. Biosorbent represent cheap filter materials

often with high affinity and capacity [10].

The application of biosorption for the removal of individual copper and zinc using the

adsorbents ulva fasciata sp. [3], marine algal biomass [4], cassava (manihot sculentacranz) tuber waste [19], sugarbeet pulp and flyash[20] etc was reported in literature. The

biosorption of copper was reported onto carbonate hydroxylapatite derived from eggshell

waste [23], palm kernel fibre [17] etc. The investigations were carried out for the removalof zinc using the adsorbents like crab carapace [6], coir [10], tectona grndis L.f.leaves

[9]. Based on literature review the biosorption of Cu and Zn from mixed solution by

erythrina variegate orientalis leaf powder was carried out in this investigation. The other

investigations and their results were tabulated in table 1.

Table 1

Results of literature cited

Adsorbent [Reference] Metal study Results

Papaya wood [1]

Ulva fasciata sp. [3]

Marine algal biomass [4]

Ulva fasciata sp.[5]

Crab carapace [6]

Phanerochatechrysosporium[7]

Barley straws [8]

Tectona grndis L.f.leaves

[9]

Coir[10]

Cu, Zn, Cd

Cu, Zn

Cu, Zn, Pb,

Cd, Ni

Cu

Zn

Cu (II),Zn(II),

Pb(II)

Cu2+, Pb2+

Zn

Zn

t = 60 min, Langmuir isotherm, second order,

Optimum pH= 5, Langmuir isotherm,

qmax=26.88 mg/g for Cu and 13.5 mg/g for Zn

Optimum pH= 5 for Cu and 5.5 for Zn, t= 60

min, Langmuir isotherm, qmax =1.14 mmol/g for

Cu and 0.81 mmol/g for Zn

t=20 min, Optimum pH=5, Langmuir isotherm,

second order, K=0.0072

Optimum pH= above 4, qmax = 172.5 mg/g,

t= 60 min, Langmuir isotherm, qmax = 98.85mg/g for Cu and 48.85 mg/g for Zn

Optimum pH=6, qmax = 4.64 (mg/g) for Cu, K f = 0.662mmol/g

t= 180 min, Optimum pH=5, Langmuir

isotherm, qmax = 16.42 mg/g, second order,

K=0.0165, exothermic.

Optimum pH= 5.6, Freundlich isotherm,

K f = 0.021 mmol/g

3



Palm kernel fibre [17]

Cassava (manihot

sculenta cranz) tuber

bark waste [19]

Sugarbeet pulp(SBP)[20]

Flyash (FA) [20]

Black carrot residues[21]

Caulerpa lentllifera[22]

Carbonate

hydroxylapatite

derived fromeggshellwaste[23]

Calymperes erosum [24]

PEI-modified biomass[25]

Indigenous isolateenterobacter sp.[26]

Exhausted coffee

grounds[27]

Sago waste [28]

Seaweeds [29]

Chitosan [30]

Cu

Cu, Zn, Cd

Cu, Zn

Cu, Zn

Cu (II), Mn

(II),Co(II), Ni(II)

Cu, Zn, Cd,Pb

Cu(II), Cd(II)

Zn (II)

Cu (II),Pb(II), Ni(II)

Cu, Pb, Cd

Cu, Zn, Cd

Cu, Pb

Zn (II)

Zn (II)

t= 60 min, Optimum pH= 5.01, second order,K= 0.1068

Langmuir isotherm , second order, K= 5.76 x

10-3 for Cu and 5.80x10-3 for Zn

Freundlich isotherm, qmax (mg/g) = 0.0024 for Cu and 0.0027 for Zn

Langmuir isotherm, qmax (mg/g) = 0.180 for Cu

and 0.170 for Zn

Optimum pH=5.25, Langmuir isotherm, qmax

(mg/g)= 8.745, first order, k= 7.0x103,endothermic

Optimum pH>6.0 for Cu and pH>6.5 for Zn

t=60 min, Langmuir isotherm, qmax = 142.86

mg/g,

Optimum pH=4, Langmuir isotherm, qmax =37.45 mg/g

t= 30 min, Langmuir isotherm

t= 24hr, Optimum pH= 3, Langmuir andFreundlich isotherms, second order, K= 0.0716

Optimum pH= 5, Langmuir isotherm

t= 24 hrs, Optimum pH= 4.5 to 5.5, Langmuir

isotherm, qmax= 12.42 mg/g second order, R 2 =0.99

Optimum pH= 5.5, Langmuir model, qmax=135.5 mg/g, second order, K= 0.0003 at 250

mg/L, endothermic

t= 6 min, Optimum pH=7,Langmuir andFreundlich isotherms, endothermic

4



Experimental

Biosorbent preparation

The Erythrina variegata orientalis is a fast growing, dense, medium-large deciduous tree

growing to 15-25 m height spread over 12-15 m with 80-100 year life. The Indian coraltrees are abundantly and freely available in rural India and can be discarded without

regeneration. The analyses of the leaves indicate the presence of scoulerine, saponin,

hydrocyanic acid. Erythrinine (an alkaloid) having properties identical to those of

hypaphorine (C14H18 N2O2), (+) coreximine, l-Reticuline, erybidine [11]. The maturedleaves were collected from Andhra University College campus, Visakhapatnam. The IR

spectrum and XRD of Erythrina variegate orientalis leaf powder was indicated the

presence of hydroxyl and carboxy moities as major functional groups. The BET surface

area of the adsorbent is 22.08 m

2

/g with a cumulative volume of 7.05 mL/g at STP andmonolayer of 5.07 cm3/g[12]. These leaves were thoroughly washed with water to

remove dust and water soluble impurities. The leaves were further washed with necessarydistilled water to free them of color and turbidity. The leaves were dried under sunlight

and powdered. The dry leaf powder was sieved to different fractions (i.e. 45 μm, 75 μm,

106 μm and 212 μm) using rotap sieve shaker. These size fractions were preserved in

glass bottles for use as a biosorbent.

Preparation of stock solution

3.898 gm of 99% CuSO4.5H2O and 4.443 gm of ZnSO4.7H2O were dissolved in 1L of

distilled water to prepare 1000 mg/L of copper and zinc mixed stock solution. Samples

of different concentrations were prepared from this stock solution by appropriatedilutions. 100 mg/L of mixed solution was prepared by diluting 100 mL (containing50

mL of Cu and 50 mL of Zn) of mixed stock solution with distilled water in 1000 mL

volumetric flask up to the mark. Similarly solutions with different concentrations of Cu-Zn mixture (25 mg/L, 50 mg/L, 125 mg/L and 150 mg/L) were prepared.

Procedure

50 mL of mixed solution containing 50 mg/L of Cu and 50 mg/ L of Zn was shaken in a

250 mL conical flask and treated with 2 g/L of 45 μm size biosorbent for 30 min on an

orbital shaker at 180 rpm and 303 K. The sample was settled and filtered through aWhatman filter paper. Then the filtrate was analyzed in an Atomic Absorption

Spectrophotometer (Perkin Elmer-AA Analyst-200 (air-acetylene oxidizing flame), wave

length for Cu was 324.8 nm and wave length for Zn 213.9 nm) for final concentration of Copper and Zinc separately and the sum is as the final concentration of Cu-Zn mixture.

The same procedure was repeated to study the other parameters such as agitation time

(t), biosorbent size (d p), biosorbent dosage (w), initial concentration of Cu – Zn mixture

in the mixed solution (Co), pH of the mixed solution and temperature (T) on biosorption

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of Cu – Zn. The range of the experimental parameters investigated in this biosorption

studies are compiled in table-2.

Table- 2

Experimental parameters investigated

Parameter Values

Agitation time, t, min

Biosorbent size, d p, μm

Biosorbent dosage, w, g/LInitial concentration of Cu-Zn mixture, Co, mg/L

pH of the mixed solution

Temperature, K

1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 60,

120 & 180

45, 75, 106 & 212

1, 2, 5 & 1025, 50, 75, 100, 125 & 150

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11& 12

283, 293, 303, 313 & 323

The percentage removal of copper and zinc is calculated as:

% removal = (C0-Ce) x 100/ C0 ……… (1)

where Co and Ce are the initial and final concentrations of the cu-zn in the mixed solution.The metal uptake is calculated as:

qe = {(Co- Ce) V} / w ………………… (2)

where qe is the metal uptake(mg/g), V is the volume of the mixed solution and w is the

dosage of the biosorbent.

Adsorption isotherms

Adsorption isotherm is important to develop an equation that accurately represents the

results and can be used in design of sorption systems [16]. Three adsorption models-

Freundlich, Langmuir, and Temkin were used to describe the equilibrium between

adsorbed metal ions of Cu- Zn mixture on Erythina variegate orientalis leaf powder at aconstant temperature.

According to the Freundlich equation [13], the amount of substance adsorbed per gram of adsorbent (qe) is related to the equilibrium concentration (Ce) as:

qe = K f Ce

n

…….. (3)or

log qe = n log Ce + log K f ........... (4)

where K f (mg/g) is the constant indicative of the relative adsorption capacity of the

adsorbent and ‘n’ is the constant indicative of the intensity of the adsorption.

6



The Langmuir model [14], is valid for monolayer adsorption onto a surface containing a

finite number of identical sites. It is probably the most popular isotherm model due to its

simplicity and its good agreement with experimental data. It could be described by thelinearised form:

(Ce/qe) = 1/(K a qmax) +Ce/qmax …….... (5)

where qmax the maximum amount adsorbed, K a is an equilibrium adsorption constant, Ce is

the concentration of the adsorbate at equilibrium and qe is the amount adsorbed atequilibrium in unit mass of the adsorbent. By plotting a graph between C e and (Ce/qe),

qmax and K a can be determined from the slope (1/qmax) and the intercept (1/K a qmax).

The Temkin isotherm equation [15] describes the behavior of many adsorption systemson heterogeneous surface and it is based on the following equation:

qe= RT ln (atCe)/bt ……… (6)

The linear form of temkin isotherm can be expressed by Eq. (7):

qe = A+B ln Ce ……… (7)

where R is the gas constant, T absolute temperature (K), A (= RT/b t ln a t) and B (= RT/

bt) isotherm constants respectively.

Kinetics of sorption

The order of adsorbate- adsorbent interactions has been described by using various

kinetic models. In the case of adsorption preceded by diffusion through a boundary, the

kinetics in most cases follows the pseudo- first-order rate equation of Lagergren[16] :

(dqt/dt) = k ad (qe - qt) ……… (8)

where qt and qe are the amount adsorbed at time t and at equilibrium, and k ad is the rate

constant of the pseudo-first-order adsorption process. The integrated rate law, after

applying the initial condition of qt=0 at t=0, is

log (qe - qt) = log qe – (k ad /2.303) t …(9)

Plot of log (qe-qt) versus t gives a straight line for first-order kinetics, which allowscomputation of the adsorption rate constant, k ad.

The pseudo-second-order kinetics [17] may be expressed as:

dqt/dt = k (qe-qt)2 ………… (10)

7



is applicable. For the boundary conditions t=0 to t=t and qt=0 to qt=qt, the integrated form

of the equation is

1/(qe-qt) = (1/qe) + kt ………… (11)

that can be written as

(t /qt) = (1/ kqe2) + (t/qe) …. (12)

If the pseudo-second order kinetics is applicable, the plot of t/qt versus t gives a linear

relationship, that allows computation of qe, k and kqe2 .

Thermodynamics of adsorption

According to Lechatelier principle, the amount adsorbed at a given concentration

decreases as temperature increases. During adsorption, physical changes like spontaneity

of adsorption and experimental results like rate constant of that particular adsorption process will be effected with the changes in three thermodynamic parameters. Enthalpy

change (∆H), entropy change (∆S) and change in Gibbs free energy (∆G) due to transfer of unit mole of solute from solution to the solid-liquid interface. These values can be

obtained by carrying out the adsorption experiments at different temperatures. The

biosorption data were obtained at temperatures (283 K, 293 K, 303 K, 313 K and 323 K).

The thermodynamic parameters for adsorption were evaluated from the well known

relation [18]:

log K = - ∆G/ (2.303RT) = - ∆H/ (2.303 RT) + (∆S/2.303 R)......... (13)

where K= qe/Ce.

Plot of log (qe/Ce) versus (1/T) yields a straight line with slope =- ∆H/ (2.303 R) and

intercept = ∆S/(2.303R).

RESULTS AND DISCUSSION

Effect of agitation time:

The equilibrium agitation time is determined by plotting the % removal of Cu-Zn against

agitation time in fig. 1 for biosorbent sizes of 45, 75, 106 and 212 μm using 0.1g (2 g/L)dosage for C0=100 mg/L. The % removal of Cu-Zn mixture is found to be very quick and

equilibrium is attained in 30 min. The percent removal for 45 μm, 75 μm, 102 μm and

212 μm sizes are 91.86%, 89.89%, 83.98% and 78.31% respectively. 20-30 min of equilibrium agitation time had been reported for the removal of Cu and Zn by cassava

tuber bark waste [19]. An equilibrium agitation time of 60min was reported for cu and zn

by the adsorbents papaya wood [1], sugar beet pulp and flyash [20], marine algal biomass

[4]. The equilibrium contact time of 30 min for Cu (II) adsorption by black carrot

8



(Daucus carota L.) residue was observed by Guzel [21]. Equilibrium agitation time of 60

min was reported for copper removal by palm kernel fiber [17].

Effect of adsorbent size and dosage:

The effect of biosorbent size on % removal of Cu-Zn mixture was shown in fig.2 with %removal as a function of d p for dosages of 1, 2, 5, 10 g/L. It is observed that the %

removal of metal decreases with increase in biosorbent size. With decrease in biosorbent

size, surface area of the biosorbent increases and more number of active sites on the biosorbent are exposed to the adsorbate, resulting in increased metal uptake (qe

=9.335mg/g).The maximum removal of 93.09% was observed with 45 μm particle size at

the dosage of 10g/L with a metal uptake capacity of 9.335mg/g. The percent removal was

decreased from 86.27% to 77.20% for the adsorbent sizes 45 to 212 μm at 1g/L biosorbent dosage. Percent removal of mixture was increased from 86.27% to 93.09%

with an increase in adsorbent dosage from 1 to 10 g/L (fig. 3). The change in % removal

is very small when biosorbent dosage (w) is increased from 2 to 10 g/L (i.e., 91.86% to

93.09%). Therefore optimum biosorbent dosage of 2 g/L is used to study the remaining parameters. The adsorbent size of 75µm was used for zinc by tectona grandis L. f leaves

biomass. They revealed that the metal uptake of zinc on tectona grandis L. f leaves

decreases from 4.3866 to 3.256 mg/g with the increased particle size from 75 µm to 212

µm. It is well known that decreasing the average particle size of the adsorbent increases

the surface area, which in turn increases the adsorption capacity [9].

Effect of pH of the mixed solution:

The effect of pH on biosorption of Cu-Zn mixture is shown in fig.4 for 2 g/L of 45 µm

biosorbent size varying pH from 1 to 10. The % biosorption of Cu-Zn mixture is

increased gradually from pH

= 1 to 6 (76.5% to 89.55%) and decreased gradually beyond pH value of 6 (86.25% to 80%). At less pH values % biosorption is low because the

metal ions will compete with H+ ions for appropriate sites on the adsorbent surface.However, with increasing pH (upto neutral value), this competition weakens and metal

ions replace H+ ions bound to the adsorbent or forming part of the surface functional

groups such as OH, COOH. As pH is increased from 6, OH - ions will be increased and

these will compete with metal ions. Formation of precipitation is also observed beyond pH 8.

Apiratikul, et al [22] observed a formation of precipitation of heavy metal at pH>6 for cuand pH>6.5 for zn. The pH of 5+0.2 is used for the adsorption of Cu and Zn by green

macroalga. A pH of 5 has been fixed for the adsorption of both Cu and Zn by cassava

tuber bark waste [19]. Saeed et al [1] investigated that, at pH=5 the optimum biosorptionwas reached with 97.3% removal of Cu and 66.6% removal of Zn. Pehlivan et al [20] had

identified the maximum overall uptake of copper by SBP as 30.9mg/g at pH=5.5 and by

flyash 7mg/g at pH=5. They also reported the maximum uptake of zinc by SBP as

35.6mg/g at pH=6 and by flyash 7.84mg/g at pH=4. Kumar et al [3] reported optimum pH=5 for Cu and Zn removal with 0.1 g/L and 26.88 mg/g and metal capacity

respectively. In all the above investigations maximum removal was reported in the pH

9



range of 5 to 6 for both Cu and Zn. In the present investigation, maximum removal of Cu

- Zn mixture (89.55%) was obtained at pH = 6 for 2 g/L of 45 μm size biosorbent in 100

mg/L of mixed solution.

Effect of initial concentration of Cu-Zn mixture:

Fig.5 represents the variation in biosorption of Cu-Zn mixture with initial concentration

of cu-zn mixed solution. Results from the plots indicate that the % removal of Cu-Zn

mixture is decreasing (from 92.23% to 85.99%) significantly with an increase in initialconcentration of Cu-Zn mixed solution Co from 25 mg/L to 150 mg/L. The metal uptake

capacity was increased from 11.53 mg/g to 64.49 mg/g as the concentration of mixture

was increased. The effect of initial copper ion concentration (50 to 250 mg/dm3) on

copper ion uptake onto palm kernel fiber was studied by Yuh- Shan Ho et al [17]. Theyreported that the amount of cu ions adsorbed at equilibrium increased with an increase in

initial Cu ion concentration. The removal of cu ions increased from 4.451 to 13.07 mg/g

when the initial copper ion concentration was increased from 50 to 250 mg/dm3 at pH

5.01. Lu et al [6] increased the initial zn

2+

concentration from 10 to 140 mg/L and theremoval efficiency was decreased rapidly from 99% to 65.25 % on small crab carapace

particles.

Freundlich, Langmuir and Temkin isotherms

Freundlich isotherm is drawn for the present data between log Ce and log qe in fig.6. The

resulting line has the correlation coefficient of 0.98. The following equation is obtained:

log qe = 0.790 log Ce + 0.858, R 2= 0.98 ……. (14)

The slope (n) of the above equation is 0.79 this value satisfies the condition of 0 < n< 1

indicating favorable adsorption.

Langmuir isotherm, drawn in fig.7, has good linearity correlation coefficient of 0.99

indicating strong binding of Cu-Zn mixed solution to the surface of erythrina variegata

orientalis leaf powder. The data are well correlated by the equation:

(Ce/qe) = 0.008 Ce + 0.146, R 2 = 0.99 ……… (15)

To study the suitability of Temkin isotherm, a graph is plotted between ln C e and qe in

fig.8. The resulted equation is:

qe = 22.44ln Ce - 6.44, R 2 = 0.98 …….. (16)

R 2= 0.98 indicates that the Temkin isotherm is suitable for the present study. Freundlich,

Langmuir and Temkin constants obtained in the present investigation are compiled in

table – 3.

10



Table-3

Freundlich, Langmuir and Temkin constants for Cu-Zn mixed solution

Langmuir isotherm Freundlich isotherm Temkin isotherm

qmax(mg/g) k a R 2 K f N R 2 at

(L/mg)

bt R 2

125 856.16 0.99 7.095 0.79 0.98 0.75 112.26 0.98

Kinetics of biosorption:

In order to determine the order and rate of the biosorption, 50 mL of mixed solution was

taken in each of fourteen 250 mL conical flasks. 2 g/L of 45 μm size biosorbent wasadded to each sample. The contents of conical flasks were shaken in an orbital shaker for different agitation times (1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 60, 120 and 180). Similar

procedure was adopted for the biosorbent dosages of 0.05 gm, 0.25 gms and 0.5 gms (1, 5

and 10 g/L) with 45 μm biosorbent size. The pseudo first order Lagergren plot of log (qe-

qt) versus agitation time (t) for biosorption of cu-zn mixture for biosorbent size of 45 μmand at different biosorbent dosages 1, 2, 5 and 10 g/L erythrina variegata orientalis leaf

powder was drawn in fig 9. The resulting equations and constants are shown in table-4.

Table -4

Lagergren equations and its coefficients

w, g/L d p, μm Equation k ad, min-1 R 2

1 45 log (qe-qt) = 0.042 t +1.36 0.096 0.99

2 45 log (qe-qt) = 0.028 t + 1.073 0.0644 0.95

5 45 log (qe-qt) = 0.0316 t+0.687 0.0727 0.95

10 45 log (qe-qt) = 0.0314 t+0.375 0.723 0.90

To identify the suitability of rate equation, the second order rate equation is applied for

the present data and the plots of (t/q t) versus‘t’ are drawn in fig. 10. The pseudo second

order model based on equation (11), considers the rate -limiting step as the formation of

chemisorptive bond involving sharing or exchange of electrons between the adsorbateand adsorbent. The second order rate equations obtained from the graph are shown in

table 5.

11



Table-5

Pseudo-second-order equations and its coefficients

w, g/L Equation k x 104, g/(mg-min) R 2

1

2

5

10

(t/qt) = 0.011 t + 0.010

(t/qt) = 0.022t + 0.022

(t/qt) = 0.055 t + 0.054

(t/qt) = 0.109 t + 0.111

82.9

9.39

0.61

0.07

0.99

0.99

0.99

0.99

So, second order rate equation better explains the interactions of Cu-Zn mixture than the

first order rate equation as the R values are higher in case of second order rate equations.

Thermodynamics of biosorption

The biosorption data are obtained for various initial concentrations of the mixed solution

adding 2 g/L of 45µ m size adsorbent. Fig. 11 indicates that increased temperature results

in lower % removal of cu-zn mixed solution. The Vant Hoff’s plot (log (q e/Ce) as a

function of (1/T)) is shown in fig 12. The change in enthalpy (∆ H), change in

entropy(∆ S) and change in Gibbs free energy (∆ G) for Cu-Zn mixture at various

concentrations are given in table-6.

Table -6

Thermodynamic parameters for various initial concentrations

Co, Initial

concentration of

mixture, mg/L

∆ H

kJmol-1

∆ S

kJmol-1 K -1∆ G kJmol-1

283 K 293 K 303 K 313 K 323 K

50

100150

-17.23

-14.36-9.956

-44.34

-37.70-25.12

12.56

10.687.11

13.00

11.067.37

13.45

11.437.62

13.89

11.817.87

14.33

12.198.12

The above results indicate that the heat of reaction (∆H) is negative. The negative valueof ∆H value indicates the biosorption is exothermic [32]. The negative value of ΔSconfirms the reversibility of the biosorption and the gradual increase in the ΔS value with

the concentration indicates that the process is tending towards irreversibility [18]. The

spontaneity of the biosorption is demonstrated further by the increase in free energy

change with temperature. The increase in ΔG value with an increase in temperatureindicates that the biosorption of Cu-Zn mixture is less favorable at high temperatures and

also shows physical nature of the biosorption. From the above values of ∆G, ∆H and ∆S

12



obtained with erythrina variegate orientalis leaf powder show that the adsorbent has the

potential to remove Cu-Zn from the mixed aqueous solutions.

CONCLUSIONS

(i) The optimum agitation time for the biosorption of Cu –Zn mixture is 30 min.

(ii) The % removal of Cu – Zn mixture in mixed solution increases with decrease in biosorbent size and increase in the biosorbent dosage.

(iii) The increase in the initial concentration of Cu - Zn mixture results in a decrease in %

removal of Cu - Zn mixture.

(iv) The % biosorption of cu-zn mixture is increased gradually from pH = 1 to 5.5 and

decreased gradually beyond pH value of 5.5.

(v) The biosorption data are well fitted to Freundlich, Langmuir and Temkin isotherms.

(vi) The kinetics of biosorption of Cu -Zn mixture by erythrina variegata orientalis leaf

powder is well described by second order kinetics than the first order kinetics.

(vii) The percentage removal of Cu -Zn mixture decreases with increase in temperature.

(viii) The negative value of ∆H value indicates the biosorption is exothermic. The

negative value of ΔS confirms the reversibility of the biosorption and the gradualincrease in the ΔS value with the concentration indicates that the process is tending

towards irreversibility. The increase in ΔG value with an increase in temperature

indicates that the biosorption of Cu-Zn mixture is less favorable at hightemperatures.

NOMENCLATURE

Ce Equilibrium concentration of Cu – Zn mixture, mg/L

Co Initial concentration of mixed solution comprising of

copper and zinc, mg/L

Cco Initial concentration of copper in the mixed solution, mg/L

Czo Initial concentration of zinc in the mixed solution, mg/L

d p Biosorbent size, µm

∆G Change in Gibbs free energy, kJ /mole

13



∆H Enthalpy change J/mole

k ad First order rate constant for Cu – Zn mixture, min-1

k Second order rate constant for the Cu – Zn mixture,

g/(mL-min)

K f Freundlich coefficient for Cu – Zn mixture, mg/g

K a Langmuir biosorption constant

K Thermodyanamic constant(qe/Ce)

n Freundlich coefficient for Cu – Zn mixture

qe Amount of Cu – Zn mixture adsorbed per unit mass of

biosorbent at equilibrium, mg/gm

qt Amount of Cu – Zn mixture adsorbed per unit mass of biosorbent at time t (min), mg/gm

qmax Langmuir monolayer capacity, mg/gm

R 2 Correlation Coeffitient

R Universal gas constant, 8.314 J / mole. K

∆S Entropy change, kJ /mole-K

T Absolute temperature, K

t Agitation time, min

V Volume of mixed solution, mL

w Biosorbent dosage, g/L

14



REFERENCES

1. Asma Saeed , M. Waheed Akther and Muhammed IqbalRemoval and recovery of heavy metals from aqueous solution using papaya wood as

a new biosorbent.

Separation and Purification Technology, 45 (2005) 25-31

2. Volesky. B.,

Detoixification of metal- bearing effluents: biosorption for the next century

Hydrometallurgy, 59 (2001) 203-216

3. Prasanna Kumar, Y., King, P. and Prasad, V.S.R.K.,

Comparison for adsorption modeling of Cu and Zn from aqueous solution by

Ulvafaciata spJournal of Hazardous Materials, B 1379 (2006) 1246-1251

4. Ping Xin Sheng, Yen-peng Ting, J. Paul Chen and Liang Hong

Sorption of lead, copper, cadmium, Zinc and nickel by marine algal biomass:

Characterization of biosorptive capacity and investigation of mechanisms

Journal of Colloid and Interface Science, 275 (2004) 131-141

5. Prasanna Kumar, Y., King, P. and Prasad, V.S.R.K.,

Removal of copper from aqueous solution using Ulva fasciata sp.- A marine green algaeJournal of Hazardous Materials, B 137(2006) 367-373

6. Shuguang Lu, Stuart W. Gibb and Emma CochraneEffective removal of zinc ions from aqueous solutions using crab carapace biosorbent

Journal of Hazardous Materials, 149(1) (2007) 208-217

7. Iqbal, M. and Edyvean, R. G. J.,

Biosorption of lead, copper and zinc ions on loofa sponge immobilized biomass of

Phanerochaete chrysosporium

Minerals Engineering, 17 (2004) 217–223

8. Erol Pehlivan, Türkan Altun and Serife

Utilization of barley straws as biosorbents for Cu2+ and Pb2+ ionsJournal of Hazardous Materials, 164 (2009) 982–986

9. Prasanna Kumar, Y., King, P. and Prasad, V.S. R. K.,Zinc biosorption on Techtona grandis leaves biomass: Equillibrium and kinetic studies

Chemical Engineering Journal, 124 (2006) 63-70

10. Kathrine Conrad and Hans Christian Bruun Hansen

15



Sorption of zinc and lead on coir

Bioresource Technology, 98 (2007) 89-97

11. Compendium of Medicinal Plants, CSIR Publications, New Delhi, (5)(1999)

12. Rohini Kumar, P., Venkateswara Rao, M., Chitti Babu, N., Ravi Kumar, P. V. andVenkateswarlu, P.,

Utilization of erythrina variegate orientalis leaf powder for the removal of cadmium

Indian Journal of Chemical Technology, 16(2009) 308-316

13. Langmuir, I.,

The constitution and fundamental properties of solids and liquids

J. Am. Chem. Soc., 38 (1916) 2221-2295

14. Freundlich, H.,

Fundamentals of interface and colloid science: particulate colloids

Colloid and Capillary Chemistry, Methuen, London, 1926

15. Runping Han, Zhu Lu, Weihua Zou, Wang Daotong, Jie Shi and Yang JiujunRemoval of copper (II) and lead (II) from aqueous solution by manganese oxide

coated sand: II. Equilibrium study and competitive adsorption

Journal of Hazardous Materials, B 137 (2006) 480-488

16. Lagergren, S.,

About the theory of so-called adsorption of soluble substances

Sven. K. Vetenskapsa. Handlingar, 24 (1898) 1-39

17. Yuh-Shan Ho and Augustine E. Ofomaja

Kinetic studies of copper ion adsorption on palm kernel fiber Journal of Hazardous Materials, B 137 (2006) 1796-1802

18. Arunima shrma and Krishna G. BhattacharyaAzardica indica (neem) leaf powder as a biosorbent for removal of Cd(II) from aqueous

medium


19. Horsfall Jr. M., Abia A. A. and Spiff. A.,

Kinetic studies on the adsorption of Cd, Cu and Zn from aqueous solutions by

cassava (Manihot Sculenta Cranz) tuber bark wasteBioresource Technology, 97 (2006) 283-291

20. Pehlivan, E., Cetin, S. and Yanik B. H.,Equillibrium studies for the sorption of zinc and copper from aqueous solutions using

sugar beet pulp and fly ash


16



21. Fuat guzel, Hakan yakut and Giray topal

Determination of kinetic and equilibrium parameters of the batch adsorption of

Mn(II), Co(II), Ni(II) and Cu(II) from aqueous solution by black carrot (Daucuscarota L.) residues.,

Journal of Hazardous Materials, 153 (2008) 1275-1287.

22. Ronbanchob Apiratikul, Taha F.Marhaba, Suraphong Wattanachira and Prasert Pavasant

Biosorption of binary mixtures of heavy metals by green macro alga, Caulerp Lentillifera

J. Sci. Tehnol., 26 (2004) 199-207

23. Wei Zheng, Xiao-ming Li, Qi Yang, Guang-mng Zeng, Xiang-xin Shen, Ying Zhang

and Jing-jin Liu

Adsorption of Cd(II) and Cu(II) from aqueous solution by carbonate hydroxylapatitederived from eggshell waste

Journal of Hazardous Materials, 147 (2007) 534-539

24. Adesola Babarinde, N. A., Oyesiku, O. O., Oyebamji Babalola and Janet O. OlatunjiIsothermal and thermodynamics studies of the Bioosorption of Zinc (II) ions by calymperes

erosumJournal of Applied Science Research, 4 (6) (2008) 716-721

25. Shubo Deng, yen- Peng Ting

Characterization of PEI- modified biomass and biosorption of Cu (II), Pb (II), Ni(II)Water resource 39 (2005) 2167-2177

26. Wei-bin Lu, Jun-Ji Shi, Ching-Hsiung Wang and Jo-Shu ChangBiosorption of Lead, Copper and Cadmium by an indigenous isolate Enterobacter

Sp.1 possessing high heavy-metal resistance

Journal of Hazardous Materials, B 134(2006) 80-86

27. Djati Utomo, H. and Hunter, K. A.,

Adsorption of heavy metals by exhausted coffee grounds as a potential treatment methodfor waste waters

Journal of Surf. Sci. Nanotech., 4 (2006) 504-506

28. Quek , S. Y., Wase, D. A. J. and Forster, C. F.,The use of sago waste for the sorption of lead and copper

J Water Science, ISSN 24 (3) (1998) 251-256

29. R. Senthilkumar, K. vijayaraghavan, M. thilakavathi, P.v.R. Iyer and M. Velan

Seaweeds for the remediation of waste waters contaminated with zinc (II) ions


30. G. Karthikeyan, K. Anbalagan and N. Muthulakshmi Andal

Adsorption dynamics and equilibrium studies on Zn (II) onto chitoson

J. chem. Sci. 116(2) 119-127

17



31. Benaissa, H. and Elouchdi, M. A.,

Removal of Copper ions from aqueous solutions by dried sunflower leavesChemical Engineering and Processing 46 (2007) 614-622

32. Anoop Krishnan and Anirudhan, T. S.,Kinetic and equilibrium modeling of Cobalt(II) adsorption onto bagasse pith based

sulphurised activated carbon

Chemical Engineering Journal, 137 (2008) 246-251

18



0 20 40 60 80 100 120 140 160 180 200

50

60

70

80

90

100

45

75

102

212

Fig. 1 Influence of agitation time on % removal of Cu-Zn mixture


%

r e m o v a l o f C u - Z n m i x t u

r e

w = 2 g/LV = 50 mLC

o= 100 mg/L

Cco= Czo= 50 mg/L

pH = 5.5

dp, µm

20 40 60 80 100 120 140 160 180 200 220 240

% r

e m o v a l o f C u - Z n m i x t u r e

75

80

85

90

95

1

2

5

10

Fig. 2 Variation of % removal of Cu-Zn mixture with biosorbent size

Biosorbent size, dp, µm

w, g/L

t = 30 minV = 50 mLC

o= 100 mg/L

Cco= Czo= 50 mg/L

pH = 5.5

19



0 2 4 6 8 10 12

86

88

90

92

94

96

Biosorbent dosage, w, g/L

%

r e m o v a l o f C u - Z n m i x t u r e

Fig. 3 Influence of biosorbent dosage on % removal of Cu-Zn mixture

t = 30 minV = 50 mLCo= 100 mg/L

Cco= Czo= 50 mg/L

dp = 45 µm

pH = 5.5

0 2 4 6 8 10 12

74

76

78

80

82

84

86

88

90

92

pH of mixed solution

%

r e m o v a l o f C u - Z n m i x t u r e

Fig.4 Effect of pH of mixed solution on % removal of Cu-Zn mixture

w = 2 g/Lt = 30 minV = 50 mLCo= 100 mg/L

Cco= Czo= 50 mg/L

dp = 45 µm

20



0 20 40 60 80 100 120 140 16085

86

87

88

89

90

91

92

93

Initial concentration of Cu-Zn mixture inmixed solution, Co, mg/L

% r

e m o v a l o f C u - Z n m

i x t u r e

Fig.5 % removal of Cu-Zn mixture as a function of initial concentration of Cu-Zn mixed solution

t = 30 minw = 2 g/Ld

p= 45 µm

V = 50 mL

pH = 5.5

0.2 0.4 0.6 0.8 1.0 1.2 1.4

1.0

1.2

1.4

1.6

1.8

2.0

log Ce

l o g q e

Fig.6 Freundlich isotherm for biosorption of Cu-Zn mixture

t = 30 minw = 2 g/Ldp= 45 µm

V = 50 mLpH = 5.5

l o g q e =

0. 7 9 0

l o g C e

+ 0. 8

5 1 ; R 2 =

0. 9 8 8

21



0 5 10 15 20 25

0.14

0.16

0.18

0.20

0.22

0.24

0.26

0.28

0.30

0.32

0.34

Ce, mg/L

Fig.7 Langmuir isotherm for biosorption of Cu-Zn mixture

( C e

/ q e

) , g / L

t = 30 minw = 2 g/Ldp= 45 µm

V = 50 mLpH = 5.5

C e / q e

= 0. 0 0

8 C e

+ 0. 1 4

6 ;

R 2 = 0. 9

9

22

ln Ce

0.5 1.0 1.5 2.0 2.5 3.0 3.5

q e

0

10

20

30

40

50

60

70

Fig.8 Temkin isotherm for biosorption of Cu-Zn mixture

q e = 2 2

. 4 4 l n

C e - 6

. 4 4 ;

R 2 =

0. 9 8

t = 30 minw = 2 g/L

dp= 45 µmV = 50 mLpH = 5.5



Fig.9 First order kinetics for biosorption of Cu-Zn mixture

t = 30 minC0=100 mg / L

dp= 45 µm

V = 50 mLpH = 5.5


0 5 10 15 20 25 30

-1.0

-0.5

0.0

0.5

1.0

1.5

1

2

5

10

l o g ( q

e - q t )

t = 30 minC0=100 mg/L

Cco=Czo=50 mg/L

dp= 45 µm

V = 50 mLpH = 5.5

w, g/L

Fig.10 Second order kinetics for biosorption of Cu-Zn mixture


0 5 10 15 20 25 30 35

t / q t

0

1

2

3

4

1

2

510

t = 30 minC0= 100 mg / L

dp= 45 µm

V = 50 mLpH = 5.5

w, g/L

R2

= 0.998

R 2 = 0.

9 9 7

R 2 =

0. 9 9 7

R

2 = 0

. 9 9 7

23



280 290 300 310 320 330

78

80

82

84

86

88

90

92

94

50

100

150

Temperature, K

% r

e m o v a l o f C u - Z n m i x

t u r e

Fig. 11 Effect of temperature on % removal of Cu-Zinc mixtur for different concentrations of mixed solution

t = 30 mindp = 45 µm

w = 2 g/LV = 50 mLpH = 5.5

C0, mg/L

0.0030 0.0031 0.0032 0.0033 0.0034 0.0035 0.0036

0.3

0.4

0.5

0.6

0.7

0.8

50

100150

(1/T) X 10-3

, K-1

l o g ( q

e / C

e )

Fig.12 Effect of temperature on biosorption of Cu-Zn mixture (Van't Hoff plot)

t = 30 minw = 2 g/L

dp= 45 µmV = 50 mLpH = 5.5

C0, mg/L

l o g ( q e

/ C e ) =

0. 9 0

0 ( 1 / T ) - 2. 3

1 6 ; R

2 = 0. 9

6

l o g ( q e

/ C e ) =

0. 7 5 0 (

1 / T ) - 1.

9 6 9 ;

R 2 = 0

. 9 4

l o g ( q e

/ C e ) = 0

. 5 2 0 ( 1 / T

) - 1. 3 1 2 ;

R 2 = 0

. 9 2

Documents

Equilibrium, Kinetic and Thermodynamic Studies on ion of Copper and Zinc From Mixed Solution by Erythrina Variegata Oriental Is Leaf Powder