ORIGINAL PAPER

Evaluation of sorption behavior of polymethylene-bis(2-hydroxybenzaldehyde) for Cu(II), Ni(II), Fe(III),Co(II) and Cd(II) ions

Ambreen Shah • M. Y. Khuhawar • Asif A. Shah

Received: 5 September 2011 / Accepted: 29 February 2012 / Published online: 27 March 2012

� Iran Polymer and Petrochemical Institute 2012

Abstract Poly[5,50-methylene-bis(2-hydroxybenzaldehyde)

1,2-phenylenediimine] resin was prepared and character-

ized by employing elemental, thermal analysis, FTIR, and

UV–visible spectroscopy. The metal uptake behavior of

synthesized polymer towards Cu(II), Co(II), Ni(II), Fe(III)

and Cd(II) ions was investigated and optimized with

respect to pH, shaking speed, and equilibration time. The

sorption data of all these metal ions followed Langmuir,

Freundlich, and Dubinin–Radushkevich isotherms. The

Freundlich parameters were computed 1/n = 0.31 ± 0.02,

0.3091 ± 0.02, 0.3201 ± 0.05, 0.368 ± 0.04, and 0.23 ±

0.01, A = 3.4 ± 0.03, 4.31 ± 0.02, 4.683 ± 0.01, 5.43 ±

0.03, and 2.8 ± 0.05 mmol g-1 for Cu(II), Co(II), Ni(II),

Fe(III), and Cd(II) ions, respectively. The variation of

sorption with temperature gives thermodynamic quantity

(DH) in the range of 36.72–53.21 kJ/mol. Using kinetic

equations (Morris–Weber and Lagergren equations), values

of intraparticle transport and the first-order rate constant

was computed for all the five metals ions. The sorption

procedure is utilized to preconcentrate these ions prior to

their determination by atomic absorption spectrometer. It

was found that the adsorption capacity values for metal-ion

intake followed the following order: Cd(II) [ Co(II) [Fe(III) [ Ni(II) [ Cu(II).

Keywords Resin � Cu(II), Co(II), Ni(II), Fe(III)

and Cd(II) ions � Sorption � Isotherms � Kinetics �Thermodynamics

Introduction

The presence of heavy-metal ions in the environment

create serious problem due to harmful effect on human

health, when extends to a certain limit.

Copper is an essential trace nutrient for all high plants,

animals, and human within certain limit. It is used exten-

sively in many products, such as copper piping and copper

wires. The copper is highly resistant to corrosion due to

non-water-proof roofing material to discourage the growth

of moss. In the recent years, adsorption of copper (II) and

other metals has been investigated [1, 2].

Very small amounts of nickel and cobalt have been

shown to be vital for life, which 0.1 ppb as the essential

concentration of cobalt in fresh water and 5 ppm of nickel

should not exceed their safe limits in drinking water [3, 4],

but nickel and its compounds at high concentration have

chronic toxicity to life. Kocaoba [5] examined the

adsorption of Ni(II) and Co(II) ions complexation to acidic

ion-exchanger resins.

Iron is a major factor in oxygen transport and an

essential mineral component of hemoglobin, myoglobin,

and several other enzymes. It is widely used in iron

medicines for the prevention and treatment of iron deficiency

(anemia). Blain et al. [6] reported the determination and

preconcentration of iron (II) and iron (III) from sea water at

nanomolar levels.

Cadmium is considered as a non-essential and highly

toxic element [7, 8]. Cadmium may occur in substantial

concentration in environment due to discharge of waste

A. Shah (&) � M. Y. Khuhawar

M.A. Kazi Institute of Chemistry, University of Sindh,

Jamshoro, Pakistan

e-mail: anashba_shah@yahoo.com

A. A. Shah

Mehran University Institute of Science, Technology and

Development, Jamshoro, Pakistan

Iran Polymer andPetrochemical Institute

123

Iran Polym J (2012) 21:325–334

DOI 10.1007/s13726-012-0033-2

water, especially of plating process [9]. A major source of

respirable cadmium is cigarette tobacco. One cigarette

contains 1–2 lg of cadmium. As much as 50 % of

cadmium fumes in cigarette smoke may be absorbed in

human body [10]. FAO–WHO jointly recommended a

maximum tolerable daily in take of cadmium 1–1.2 lg per

body mass from all sources.

Several methods have been used for preconcentration,

but solvent extraction and co-precipitation have been

replaced by the use of modified and non-modified sorbents,

having good selectivity of metals [11–14]. A number of

physically or chemically modified synthetic materials have

been synthesized including silica gel modified with

cupferron [15], N-propyl salicylic acid [16], o-aminophenol

[17], thiosalicylic acid [18], pyrocatachol [19], pyrocate-

chol violet [20], poly(ethylene terephthalate) resin [21],

and 1-hydrazinophthalazine functionalized with polysty-

rene co-divinyl benzene (XAD-4) [22].

Yang et al. [23] have observed good adsorption capacity

on thiacalix [4]amido-based polymers for various soft-

metal cations Ag?, Hg2?, Cu2?, Co2?, Ni2?, Cd2?, and

Zn2?, but low adsorption towards hard metal cations Na?

and K?. Hu et al. [24] prepared a thiacalix [4] arene-loaded

resin and investigated adsorption kinetics, thermodynam-

ics, and isotherm of the resin towards Cu(II), Pb(II) and

Cd(II) ions by batch adsorption experiments. The synthe-

sized cross-linked polymer sorbents have a network

structure and contain carboxylic acid, carbonyl, and ester

groups, all of which are capable of interacting towards

metal ions.

Chelating resins are designed for selective sorption

determination of metal ions from environment. The resin

contains as a rule one or more accessible donor atoms

which can form co-ordination bonds with metal ion [25].

Various polymeric sorbents (glycopeptides derivatives)

show the equilibrium and kinetics of adsorption process

which could be improved by using their smaller adsorbent

particles. Experimental equilibrium data were also

observed and compared with Sips, Langmuir, Freundlich,

and linear adsorption isotherms [26].

Ortho-hydroxyl compounds are having the capacity to

build efficient metal-cheating agents through phenolic

oxygen and tertiary nitrogen and have been studied as

Schiff base polymers. Samal et al. [27, 28] have reported

chelating resins with their uptake capacity for Cu(II) and

Ni(II), with two diphenolic Schiff bases derived from

4,40-diaminodiphenylmethane and o-hydroxy acetophenone

and from 1,2-diamines and hydroxybenzaldehyde. Both

were polymerized with formaldehyde or furfuraldehyde.

Present work describes the Schiff base polymer of bis

(2-hydroxybenzaldehyde)1,2-phenylenediimine condensed

with formaldehyde as an adsorbent for metal ions, e.g.,

Cu(II), Co(II), Ni(II), Fe(III) and Cd(II) with precon-

centration, followed by desorption and determination by

atomic absorption spectrophotometer. The work also

examined the kinetics of sorption, sorption isotherms, and

thermodynamics of sorption for these metal ions by the

resin. Data provided for both synthetic and real samples

represent the results of this study in detail.

Experimental

Materials

All chemicals used were of analytical or equivalent grade.

2-Hydroxy benzaldehyde, 1,2-phenylenediamine, formal-

dehyde and other organic solvents were purchased from

Merck (Germany). Stock standard solutions of Cu(II),

Co(II), Ni(II), Fe(III), and Cd(II) were prepared by dis-

solving the appropriate amounts of their salts in de-ionized

water. Buffer solutions of 1–2, 3–6, and 7–9 were prepared

by mixing appropriate ratios of 0.1 M HCl and KCl, 0.5 M

acetic acid and sodium acetate, 0.5 M ammonia and NH4Cl

solutions, respectively.

Instruments

Determinations of all five metal ions were carried out using

the Varian SpectrAA 20 atomic absorption spectropho-

tometer (Japan). FTIR spectrum was recorded on Nicolet

Avatar 330 FTIR with attenuated total reflectance (ATR)

accessory (USA). Spectrophotometer studies were carried

out in tetrahydrofuran (THF) using double beam Hitachi

220 spectrophotometer (Hitachi (Pvt) Tokyo, Japan).

Thermogravimetry (TG) was recorded on Pyris Diamond

TG/DTA (Perkin Elmer, Japan) from room temperature to

600 �C with a heating rate of 15 �C/min and nitrogen flow

rate of 50 mL/min. An amount of 10 mg of the sample was

placed in platinum crucible and recorded against a-alumina

as reference.

Preparation of resin

The Schiff base polymer of 2-hydroxybenzaldehyde with

1,2-phenylenediamine was prepared by the reported pro-

cedure [28]: 1 g of Schiff base bis(2-hydroxybenzalde-

hyde)1,2-phenylenediimine (BHBPh) was suspended in

25 mL distilled water and dissolved with addition of

minimum about 10–12 drops of 2 M NaOH. The mixture

was warmed to 50–60 �C for 5 min, and formaldehyde

(37 %, v/v) was added to a final molar ratio of 1:2 with

respect to Schiff base. Then the content was refluxed on an

oil bath for 2 h at 120–130 �C. The precipitated resin was

filtered, washed with distilled water and petroleum ether,

and lastly dried at 70 �C. The melting point of resin was

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higher than 300 �C. The structure diagram of polymeth-

ylene-bis(2-hydroxybenzaldehyde)1,2-phenylenediimine is

shown in Fig. 1. Elemental analysis of (C21H16N2O2)n,

calculated: C, 76.83 %; H, 4.87 %; N, 8.53 %. Found: C,

76.66 %; H, 4.89 %; N, 8.51 %.

Sorption procedure

Batch sorption of metal ions

Batch technique was used at 25 ± 1 �C. An amount of

100 mg resin was treated with 10 mL aqueous solution of

0.05 M Cu(II), Co(II), Ni(II), Fe(III) and Cd(II) metal ion

solutions. The pH of solution was adjusted using suitable

buffers. Suspensions of resins were agitated for 10 min

over a hot plate with magnetic stirrer. The insoluble resins

were filtered off and washed thoroughly with demineral-

ized water. The filtrate washing was collected and analyzed

by flame atomic spectrophotometer, using air acetylene

flame. The metal ion solution before addition of the resin

was also analyzed by FAAS. Lamp current was 3 mA with

slit width of 0.5 mm for Cu(II), Ni(II), and Fe(III) ions.

Lamp current was 5 mA with slit width of 0.7 mm for

Co(II) and Cd(II) ions.

Dynamic sorption of metal ions

The synthesized resin (PMBHBPh) (500 mg) was slurried

in water, and poured into a Pyrex glass column of 25 cm

with a diameter of 5 cm. A little plug of quartz wool was

placed at both ends of the column so as to avoid the loss of

resin (adsorbents). The column was connected through

peristaltic pump. The metal ion solution was passed

through peristaltic pump to the column filled with resins.

The eluent was analyzed for metal uptake or sorption

percentage and the distribution coefficient (Kd). The sep-

aration factor (a) was calculated from the data obtained by

atomic absorption spectrometry.

The following equations were used to calculate the

metal uptake or sorption percentage, the distribution

coefficient (Kd) and separation factor (a):

Sorption %ð Þ ¼ Ci � Cf=Ci � 100 ð1Þ

where Ci and Cf are the initial and final concentrations of

metal ions in solution (mg/L), respectively.

Kd ¼mmol metal ion in resin

mmol metal ion in the solution

� volume of solution mLð Þweight of resin gð Þ ð2Þ

a ¼ Kd Cu, Cdð Þ =Kd metal ion studiedð Þ ð3Þ

Sample preparation

Following procedures were applied for the determination

of Cu(II), Ni(II), Co(II), Fe(III), and Cd(II) from real and

synthetic samples, respectively.

Analysis of copper wires

Copper wires (1.0174 g) were dissolved in a mixture of

1 M HCl (5 mL) and 1 M nitric acid (2 mL) and heated to

near dryness. The residue was dissolved in double-distilled/

demineralized water and its volume was adjusted to

100 mL. This 1.0 mL of solution was further diluted to

100 mL with double-distilled water.

Analysis of iron and cobalt from various pharmaceutical

drugs

The different samples of pharmaceutical drug were placed

in a beaker of 100 mL of capacity. The tablets were

ground, added 20 mL of de-ionized water and 1 mL of

conc. HNO3. The sample was heated to reduce the volume

on hot plate up to half. After cooling, the samples were

filtered and diluted up to 10 mL with distilled water.

Analysis of cadmium from different brands of dry tobacco

(cigarettes)

Dry tobacco sample (5–8 g) was added to 10 mL of aqua

regia (HCl:HNO3, 3:1) and heated gently. The clear solu-

tion was heated near to dryness. The residue was dissolved

in 50 mL water. Then 1.0 mL of solution was further

diluted to 25 mL, with double-distilled water.

Fig. 1 Structure of poly[5,50-methylene-bis(2-hydroxybenzaldehyde)

1,2-phenylenediimine]

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Sorption procedure for samples

Each sample solution (10 mL) was added in a flask with

0.1 g resin (PMBHBPh) at optimized pH. All the sample

solutions were shaken in separate flasks at optimized

shaking speed and shaking time. After shaking, the sample

solutions were filtered and washed. The eluent and washing

of each metal were analyzed for their concentration by

atomic absorption spectrometry. The total amount of each

metal ion of different samples was calculated with the

addition of both results of eluent and washing by atomic

absorption spectrometry.

Results and discussions

First of all polymeric resin (PMBHBPh) was characterized

by spectroscopic techniques and then metal uptake (%

sorption) on the resin was investigated by batch method,

and different conditions were optimized.

Characterization of resin (PMBHBPh)

The freshly prepared resin (10 mg) was suspended over

5 mL of water at room temperature 30 �C, the solubility of

resin was checked in water after 24 h, by measuring the

absorbance of aqueous phase spectrophotometrically. The

resin was insoluble in water as well as in common organic

solvents (methanol, ethanol, and chloroform), which could

be attributed to the increase in molecular weight of the

resin. The resin was soluble in high polar solvents like

THF, DMF, and DMSO.

The spectrum of the resin (PMBHBPh) indicated C=N

stretching vibration at 1,649.89 cm-1, the phenolic O–H at

1,267 cm-1 and C=C absorption at 1,612 and 1,574 cm-1

(Fig. 2). Most of the peaks in the finger print region are

sharp and well resolved. The aliphatic C–H stretch for

methylene generated on formaldehyde condensation

appeared at 2,906.5 cm-1 as a weak band.

The measurements of UV/VIS spectrum were carried out

in THF. The polymeric resin (PMBHBPh) indicates three

absorption bands at 255 nm (1 % e = 459 L g-1 cm-1),

298 nm (1 % e = 268.2 L g-1 cm-1), and 348 nm (1 %

e = 208.8 L g-1 cm-1) (Fig. 3). The first and second

adsorption appeared due to p–p* transition in benzoid rings

contributed by aldehyde and diamine. The third band could

be responsible for p–p* transition within conjugated benzoid

ring with C=N p-electron system [28].

The TGA plot of polymeric resin showed a two-step

mass loss up to 600 �C in Fig. 4. The loss of 18 % of resin

in mass up to 160 �C in the first step may be due to the

elimination of sorbed water and CO2. This suggests the

presence of approximately one water molecule, the second

loss started after 160 �C with maximum weight loss of

64 % up to 550 �C which indicated the high thermal sta-

bility of modified resin.

Sorption studies using batch method

Effect of pH

First of all, the appropriate sorptive medium to give max-

imum sorption was optimized. Different buffers with pH

2–10 were investigated to observe the effect of pH on

adsorption of metal ions. The results are shown in Fig. 5.

The sorption increases with increase in pH of the solution

Fig. 2 FTIR spectrum of poly[5,50-methylene-bis(2-hydroxybenzal-

dehyde)1,2-phenylenediimine]

Fig. 3 UV spectrum of poly[5,50-methylene-bis(2-hydroxybenzalde-

hyde)1,2-phenylenediimine]

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and attains a maximum value at pH 4 for Fe(III), pH 6.2 for

Cu(II), pH 6.8 for Cd(II) and pH 8 for Co(II) and Ni(II)

metal ions. Increasing pH beyond the range resulted in

precipitation of metal ion as hydroxides. The metal uptake

behavior of resin (PMBHBPh) enhanced the basicity of

C=N at higher pH. The retention capacity of resin for

Cu(II) was found 1.92 mmol g-1 at pH 6.2 along with

standard deviation (SD: ±0.05) (n = 3), which is higher

than some of similar amino group; functionalized resin

1-hydrazinophthalazine [22], 1.24 mmol g-1, chelamine

resin [29], 1.0 mmol g-1, 8-hydroxy quinoline on fractogel

[30], 0.29 mmol g-1, and diamine on silica gel [31],

0.47 mmol g-1. The sorbent capacity of resin for Ni(II),

Fe(III), Co(II) and Cd(II) was obtained 1.84, 165, 1.32 and

1.21 mmol g-1 at optimum pH with (SD: ±0.03) (n = 3).

This resin has better relative capacity than resins o-amino

phenol [17], trion [32] and dithizone [33] pH 5 and 6, and

XAD resin immobilized with pyrocatechol [19] at pH 4–5.

Quantity of resin

The amounts of synthesized resin (PMBHBPh) for

adsorption of metal ions varied from 100 to 500 mg for

Cu(II) (1.52 9 10-4), Co(II) (1.69 9 10-4), Ni(II) (1.70 9

10-4), Fe(III) (1.79 9 10-4) and Cd(II) (1.34 9 10-4)

ions concentrations using 10 mL volume were also inves-

tigated. The sorption percentage was found to increase with

an increase in mass of sorbent. Thus, 100 mg of sorbent

was used for further study.

Optimum shaking speed

Shaking speed is one of the important parameters for the

sorption of metal ions and was studied in the range of

10–120 rpm. It was found that sorption percentage

increased with increase in shaking speed and attained a

maximum sorption at 80 rpm for Cu and Ni(II), 90 rpm for

Fe(III) and Cd(II), and 75 rpm for Co(II). However, sorp-

tion percentage decreased on greater speed at optimized pH

(Fig. 6), which may be due to a shift in the adsorption

equilibrium.

Optimum shaking time

The sorption of metal ions also as a function of shaking

time was studied. The sorption of Cu(II) and Ni(II) metal

chelates were rapid within 10 min, but Fe(III), Co(II) and

Cd(II) required 12–15 min and were considered as opti-

mum on modified resin (PMBHBPh). Beyond optimum

shaking time, the sorption percentage slightly decreased

but became constant at equilibrium (Fig. 7), and it was

selected for further studies.

Fig. 4 TG thermograph of poly[5,50-methylene-bis(2-hydroxybenz-

aldehyde)1,2-phenylenediimine]

Fig. 5 Effect of pH on resin (PMBHBPh) for sorption percentages of

Cu(II), Co(II), Ni(II), Fe(III) and Cd(II) using batch method

Fig. 6 Effect of optimum shaking speed on resin (PMBHBPh) for

sorption percentages of Cu(II), Co(II), Ni(II), Fe(III) and Cd(II) using

batch method

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Kinetics of sorption

The kinetics of resin–metal interaction at optimum pH was

calculated by the variation of sorption with time from

kinetic equations, i.e., Morris–Weber and Lagergren. The

Morris–Weber equation is given as follows:

qt¼Rdt tð Þ1=2 ð4Þ

where sorbed concentration, qt (mol g-1), at time ‘‘t’’ is

plotted against (t)1/2 (Fig. 8), and gave 7 min for Cu(II),

Ni(II) and Fe(III), and 8 min for Co(II) and Cd(II) with

coefficient of correlation 0.979, 0.967, 0.998, 0.992, and

0.994 for these metal ions, but deviated as the agitation time

was increased from the slope of the curve in the initial stage.

The value of Rdt, the rate constant of intraparticle transport, is

estimated to be 3.75 ± 0.15, 2.73 ± 0.21, 2.25 ± 0.21,

3.05 ± 0.28 and 4.25 ± 0.25 lmol g-1 min-1/2 for Cu(II),

Ni(II), Fe(III), Co(II) and Cd(II) ions, respectively.

The Lagergren equation is as follows:

log qe � qtð Þ ¼ log qe � kt=2:303 ð5Þ

A graph is plotted by log(qe - qt) versus t, where qe is

the sorbed concentration of metal ion onto resin

(PMBHBPh) (mol g-1) at equilibrium (Fig. 9) in the

early stage up to 10 min. The plot appeared to be linear

for metal ions and their slope gave the value for overall rate

constant k = 0.09 ± 0.01, 0.174 ± 0.02, 0.19 ± 0.07,

0.23 ± 0.02, and 0.26 ± 0.005 min-1. According to the

graph, the slope is very steep beyond 7–8 min and gives a

value of k = 1.63, 1.77, 1.94, 2.06, and 2.11 min-1 for

Cu(II), Ni(II), Fe(III), Co(II), and Cd(II) ions, respectively.

Sorption isotherms

The sorption of Cu(II), Ni(II), Fe(III), Co(II) and Cd(II)

metal ions were determined by varying concentrations

between 6.7 9 10-7 and 4.2 9 10-4 mol L-1 using

100 mg sorbent (resin)/10 mL sorbate for 10 min (opti-

mized shaking time) as well as 90 rpm (optimized shaking

speed), at 30 ± 1 �C. The uptake of metal ion increased with

increases in the concentration, and gave 95 % sorption for

Cu(II), Fe(III) and Ni(II), while 90 % sorption for Co(II) and

Cd(II). Above the concentration limit, the sorption behavior

was reduced. The effect of metal ions on resin was examined

with the variety of concentrations of solutions for removal of

metal ions. The efficiency of these metal ions on polymeric

resin (PMBHBPh) was determined with the help of follow-

ing different isothermic equations (Eqs. 6, 7 and 8):

Freundlich equation:

log Cads ¼ log A þ 1=nð Þ log Ce ð6Þ

Fig. 7 Effect of optimum shaking time on resin (PMBHBPh) for

sorption percentages of Cu(II), Co(II), Ni(II), Fe(III) and Cd(II) using

batch method

Fig. 8 Morris–Weber plot for kinetics of sorption of Cu(II), Co(II),

Ni(II), Fe(III) and Cd(II) ions on polymeric resin (PMBHBPh) at 303 K

Fig. 9 Lagergren plot for kinetics of sorption of Cu(II), Co(II),

Ni(II), Fe(III) and Cd(II) ions on polymeric resin (PMBHBPh) at

303 K

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Langmuir equation:

Ce=Cadsð Þ ¼ 1=Qbð Þ þ Ce=Qð Þ ð7Þ

Dubinin–Radushkevich equation:

ln Cads¼ ln Xm � be2 ð8Þ

where e is calculated by RT ln [1 ? (1/Ce)] equation, Ce is

the amount of metal ions in the liquid phase at equilibrium,

and Cads is the amount of metal ions adsorbed/mass of

adsorbent. The Freundlich (A) and (n), Langmuir (Q) and

(b), and Dubinin–Radushkevich (Xm) and (b) are constants

listed in Table 1 which concluded that sorption percentage

decreases at low temperature.

The mathematical results of Langmuir isotherm were

determined by means of a dimensionless constant as

separation factor (RL), which was calculated from the

equation RL = [1 ? (1 ? bCi)], where Ci represents the

initial concentration of metal ions. RL is a part of Langmuir

isotherm [34] as positive (0 \ RL [ 1), irreversible

(RL = 0) and linear (RL = 1) which represent unfavorable

separation factor. The values of separation factor (RL) for

sorption of Fe(III), Ni(II), Cu(II), Co(II) and Cd(II) metal

ions were determined as 0.07, 0.21, 0.38, 0.63, and 0.82,

respectively, which represent very favorable separation

factor (RL) on resin (PMBHBPh). The result of energy (E)

was calculated from slope of D–R plot using Eq. 9 as

follows:

E ¼ 1ffiffiffiffiffiffiffiffiffi

�2bp ð9Þ

The energy for Fe(III), Ni(II), Cu(II), Co(II), and Cd(II)

ions were found to be 13.48, 13.13, 12.96, 11.7, and

9.01 kJ mol-1, respectively, which is within the range of

9–16 kJ mol-1, estimated for ion exchange or chemisorption

[35]. Thus all metal ions were well sorbed onto polymeric

resin (PMBHBPh), but Fe(III), Ni(II) and Cu(II) were sorbed

slightly better than Co(II) and Cd(II) ions.

Thermodynamic of sorption

All results of temperature on equilibrium constant (Kc) for

the sorption of Cu(II), Ni(II), Fe(III), Co(II) and Cd(II) ions

onto resin were studied in the range of 283–323 K at

optimum conditions. At first log Kc was plotted against 1/T

(T in K). Kc was calculated by equation, Kc = Fe/(1 - Fe)

where Fe is the fraction sorbed at equilibrium. The results

of all thermodynamic parameters like DH, DG and DS were

obtained from the following relationships:

log Kc ¼ �DH RT

2:303þ DS R

2:303ð10Þ

DG ¼ �RT ln Kc ð11Þ

The results of DH, DG, and DS were obtained from the

plot of slope and intercept of enthalpy of activation energy

for Fe(III), Ni(II), Co(II), Cu(II), and Cd(II) ions, and listed

in Table 2. The parameters DH and DG indicated negative

values which showed spontaneous nature of the sorption

for metal ions with exothermic reaction.

Table 1 Sorption parameters of Cu(II), Co(II), Ni(II), Fe(III) and Cd(II) ions (6.7 9 10-7 to 4.2 9 10-4 M) onto synthesized resin

(PMBHBPh) (100 mg) at 30 �C

Metal Freundlich Langmuir D–R

A (mmol/L) 1/n r Q b (I/mol) r Xm (mmol/g) E (kJ/mol) r(mmol/g)

Fe(III) 5.43 0.37 1 0.04 2.9 9 102 0.98 0.81 13.5 0.95

Ni(II) 4.68 0.32 0.99 0.04 1.8 9 103 0.99 0.76 13.1 0.93

Co(II) 4.31 0.31 0.97 0.04 3.7 9 103 0.99 0.62 13 0.99

Cu(II) 3.41 0.3 0.94 0.06 7.1 9 104 0.97 0.35 11.7 0.97

Cd(II) 2.82 0.23 0.98 0.09 4.3 9 104 0.98 0.21 9.01 0.98

Table 2 Thermodynamic parameters of Cu(II), Co(II), Ni(II), Fe(III) and Cd(II) metal ions on polymeric resin (PMBHBPh) at 303 K

Metal DH (kJ mol-1) DG (kJ mol-1) DS (kJ mol-1) RSD

Fe(III) -50.27 ± 0.17 -1.95 ± 0.07 -0.104 ± 0.072 0.996

Ni(I) -48.21 ± 0.23 -2.19 ± 0.05 -0.118 ± 0.009 0.938

Co(II) -43.28 ± 0.37 -2.75 ± 0.05 -0.1346 ± 0.021 0.991

Cu(II) -53.21 ± 0.1 -1.6 ± 0.02 -0.156 ± 0.043 0.998

Cd(II) -36.72. ± 0.21 -4.2 ± 0.03 -0.172 ± 0.001 0.929

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Sorption studies using column technique

(dynamic sorption)

After the successful attempt of batch method, effect of pH,

contact time, shaking time, and shaking speed were opti-

mized. For dynamic sorption studies, further parameters

were optimized as follows.

Effect of flow rate

The effect of flow rate of Cu(II), Ni(II), Co(II), Fe(III) and

Cd(II) metal ion sorption on resin (PMBHBPh) was studied

in the range of 1–6 mL/min at the pH selected for maxi-

mum sorption (Fig. 10). It was observed that a decrease in

sorption at flow rates more than 2, 2.3, 2.7 mL/min for

Cu(II), Ni(II) and Co(II) ions was observed. While Cd(II)

and Fe(III) gave maximum sorption at flow rates of 1.2 and

1.6 mL/min and showed a decrease in sorption percentage

at higher flow rates. Therefore these flow rates were

selected for adsorption of Cu(II), Ni(II), Co(II), Fe(III), and

Cd(II) metal ions on the resin.

Stability of sorbent

The stability of resin was confirmed by means of several

loadings of resin as well as desorption processes. The

stability of resin was checked by its re-use for adsorption

12 times at optimized conditions, and retained standard

deviation (RSD) within 1–2 % (n = 12) for the sorption of

metal ions, which demonstrated that the resin (PMBHBPh)

was feasible for sorption.

Desorption

Desorption of metal ions was determined by shaking 0.5 g

of resin with metal solutions, at optimized circumstances.

The insoluble resin was filtered and washed with various

concentrations (0.1–2 M) and volumes (1–10 mL) of

mineral acids. Each washing was collected and analyzed by

flame AAS. It was observed that maximum Cu(II), Ni(II),

Co(II), and Cd(II) were optimized at 5–6 mL (2 M) HCl

with 92–94 % recovery of metal ions. Although the highest

desorption of Fe(III) metal required 5 mL of 1 M HCl with

recovery of Fe(III) metal ions of about 89 %.

Interference study

The sorption of these metal ions may be affected by the

presence of different cations and anions which may form

complexation or precipitation. Some cations and anions

were used to observe their interferences with Cu(II), Ni(II),

Co(II), and Cd(II) metal ions under the equilibrium con-

ditions. The synthesized resin (PMBHBPh) was treated

with 50 lg/mL of different cations or anions, like Na?, K?,

Mg2?, Ca2?, Zn2?, Mn2?, Pb2?, Cr3?, Br-, Cl-, HSO4-,

SO22-, HCO3

-, CrO42-, at optimized pH of the metal

solution for 24 h. The presence of cations/anions did not

affect the uptake capacity of Cu(II), Ni(II) and Co(II) metal

ions significantly but sorption percentage of metal ions

Fe(III) and Cd(II) were affected by cations Mg2?, Pb2?,

and Cr3? in the range of 43–51 %. In case of anions (Cl-

and Br- ions), sorption percentage of Fe and Cd metal ions

was decreased in the range of 32–44 %. Therefore, the

cations and anions only affected the Fe(III) and Cd(II)

metal ions due to the stronger affinity on surface of resin

towards other metal ions.

Analytical application

The proposed method was applied for the determination of

these five metal ions on polymeric resin (PMBHBPh). The

collection of metal ions was taken from different types of

sample, such as copper wires used for the determination of

Cu(II) ions. Ten pharmaceutical drugs were used for Co(II)

and Fe(III) ions, and nine Ni(II) and Cd(II) were taken

from different brands of tobacco samples. These metals

were eluent and determined from resin. The results are

given in Table 3, which showed applicability of method on

resin for preconcentration and desorption of metal ions by

optimized acid leaching procedure.

Fig. 10 Effect of flow rate on resin (PMBHBPh) for sorption

percentages of Cu(II), Co(II), Ni(II), Fe(III) and Cd(II) using batch

method

Table 3 Atomic absorption analysis of Cu(II) from different grades

of copper wires using resin (PMBHBPh)

S. no. Sample

(copper wires)

Amount %

found with (AAS)

RSD

(%)

1 Million supreme Karachi 92.6 2.1

2 Royal Lahore 88.0 3.5

3 Millan Lahore 90.4 1.8

332 Iran Polym J (2012) 21:325–334

Iran Polymer andPetrochemical Institute

123

Conclusion

Polymeric resins have great quality of adsorbent to remove

metal ions by the process of adsorption, every metal has its

special properties. Present work represents the synthesis of

poly[5,50-methylene-bis(2-hydroxybenzaldehyde)1,2-phen-

ylenediimine] (PMBHBPh), according to a reported

method [28], characterized by various spectroscopic tech-

niques and helpful for the preconcentration as well as

removal of metal ions from their dilute solutions. This resin

was used to determine the adsorption from real samples

such as copper wires for the determination of Cu(II) ions,

ten pharmaceutical drugs for the determination of Co(II)

and Fe(III) ions, and nine samples of different brands of

tobacco for determination of Ni(II) and Cd(II) by optimi-

zation acid leaching procedure. Under optimum conditions,

an approximate quantitative sorption was achieved for

these metal ions on resin (PMBHBPh). These metals could

be desorbed very well with 5–6 mL HCl (2 M). The further

studies showed that the rate of equilibrium was faster with

higher sorption percentage on this resin. The Langmuir,

Freundlich and Dubinin–Radushkevich sorption isotherms,

and thermodynamic parameters were also measured for

these metals. The stability of resin was determined in

practical terms which showed the least matrix interference

with other common ions.

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