Removal of Heavy Metals Cd2+, Pb2+, and Ni2+ From Aqueous

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Removal of Heavy Metals Cd2+, Pb2+, and Ni2+ From Aqueous Solutions Using Synthesized Azide Cancrinite, Na8[AlSiO4]6(N3)2.4(H2O)4.6 Ashok V. Borhade,* Tushar A. Kshirsagar, Arun G. Dholi, and Jyoti A. Agashe Research Centre, Department of Chemistry, HPT Arts and RYK Science College, Nasik 422005, India ABSTRACT: Aluminosilicate azide cancrinite, Na8[AlSiO4]6(N3)2.4(H2O)4.6, has been prepared for the first time from zeolite-A, followed by hydrothermal processing at low temperature. After crystallization, the sample was characterized by appropriate physicochemical techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (IR), thermal gravimetric analysis (TGA), and Brunauer− Emmett−Teller (BET) surface area. In the present study, attention was focused on investigating the removal performance of heavy metal ions (Cd2+, Pb2+, and Ni2+) in aqueous solution on pure aluminosilicate azide cancrinite. The kinetics of the process and sorption capacity of the adsorbent was determined in relation to the effect of various factors affecting on the adsorption process. The parameters in this study included contact time, metal ion concentration, temperature, and adsorbent dosage. The removal mechanism of metal ions followed adsorption and ion exchange process. Adsorption data has been interpreted in terms of Langmuir and Freundlich equations. The selectivity of the studied metal ions was determined as Pb2+ > Cd2+ > Ni2+. Thermodynamic parameters, i.e., equilibrium constant (Kc), free energy (ΔG°), entropy (ΔS°), and enthalpy (ΔH°) for adsorption, were computed from the experimental data.

1. INTRODUCTION Many toxic heavy metals are frequently discharged into the environment in the form of industrial wastewater, causing serious soil as well as water pollution.1 The wastewater discharged directly into natural water bodies is highly harmful to the aquatic ecosystems. The heavy metals like lead, cadmium, and nickel are common metals that cause serious diseases in living beings.2−5 Cadmium is one of the toxic metals causing serious diseases like itai itai or ouch ouch from which many of the people in Japan were known to suffer as a result of fragility of bones. High concentration of cadmium can lead to the kidney problems,1 bone marrow disorders, and anemia. In potable water the normal level of Cd is from 0.4 to 60 ppb. Lead inhibits several of the key enzymes involved in the overall process of the synthesis, whereby the metabolic intermediates accumulates. High level of Pb in blood (>0.8 ppm) shows symptoms of anemia due to deficiency of hemoglobin. Elevated lead levels (>0.5 to 0.8 ppm) in the blood cause kidney malfunction and brain damage. Another heavy metal nickel and its compounds have been listed by the National Toxicology Programme (NTP) as being reasonably anticipated to be carcinogens. A variety of cancerous and noncancerous respiratory problems such as chronic bronchitis and emphysema have been associated with those exposed to nickel compounds such as welders and foundry workers. Evidently it is most important to remove these toxic metals from wastewater prior to their discharge into natural water bodies as they are nonbiodegradable and persistent. Several techniques6,7 such as biosorption, osmosis, membrane osmosis, gravimetric precipitation, and catalytic reduction © XXXX American Chemical Society

complex formation are used to remove lead, cadmium, nickel, and zinc. Different low cost adsorbents like pea fly ash,8−10 lime,11 activated carbon,12,13 bagasse pith,14 bagasse fly ash,15 soya cake,16 slag from blast furnace,17 aluminum phosphates,18 perlite,19 modified kaolinite clay,20 brown marine macro algae,21 biofilms and associated minerals,22 modified lignite fly ash,23 iodate sodalite,24 etc. are used by number of workers for the removal of heavy metals. Use of zeolites synthesized from fly ash for applications in the removal of metal species from wastewater has been a subject of study for quite some time, and various investigations have been made to find the appropriate, efficient, and economical zeolite type.25,26 Among the various zeolites27−30 which possesses adsorbent properties, cancrinite appears to be one of the most promising to perform purification of water by removing heavy metals. Cancrinite group (CAN) minerals are framework of aluminosilicate and are characterized by an ordered distribution of Si and Al atoms in the tetrahedral sites.31,32 The cancrinite contains small ε-cage made of six membered rings and wide channels containing 12 membered rings in an ABAB type stacking sequence33−36 in the space group P63. The cancrinite cage is composed of two parallel 6-ring windows perpendicular to the c-axis, bound by 6-ring and 4-ring windows (Figure 1). The 4-ring windows are shared by neighboring cages, while the 6-ring windows interlock to form the one-dimensional 12-ring channels. Extra-framework cations, such as Na+, K+, or Cs+ and Received: July 30, 2014 Accepted: January 12, 2015

A

DOI: 10.1021/je500698x J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

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phase-purity of the product was analyzed by X-ray powder diffraction pattern using Philips PW-1710 instrument operating at 25 kV and 25 mA using Cu Kα radiation with wavelength λ = 0.154 nm. Surface morphology and elemental analysis were studied by scanning electron microscopy JEOL-JEM-6360 A model equipment JEOL-JEC-560 autocation coater, and BET surface area was determined by Autosorb-1 NOVA-1200. Thermogravimetric analysis was performed on PerkinElmerTG. 2.4. Batch Sorption Studies. Aluminosilicate azide cancrinite as an adsorbent (0.5 g) was left in contact with 50 mL of heavy metal ion solution in the range of (20 to 120) mg· L−1. The pH of solutions was maintained between 5 and 6 by using dilute hydrochloric acid. The working solutions of Pb(NO3)2, Cd(NO3)2, and Ni(NO3)2 were prepared from their respective stock solutions. All sorption studies with the model solution were carried out in high density Teflon containers with volume capacity of 100 mL. Initial equilibrium concentrations were determined with classical titration method and some of the concentrations were determined by atomic absorption spectroscopy. The results obtained by titration method match well with the atomic absorption spectroscopy and we preferred the classical method throughout this study. In order to obtain the sorption capacity, the amount of metal ions adsorbed per unit mass by azide cancrinite as an adsorbent (6qe in milligrams of metal ions per gram of adsorbent) was calculated by using eq 1,

Figure 1. Typical cage of cancrinite.

water molecules are located both in the cancrinite cage and 12ring channels. A literature survey27,37−39 shows that, several researchers have studied the removal capacity and selectivity sequence of the heavy metal ions adsorption by natural zeolites and their synthetic counterpart. It is found that no attempt is made on synthesis of aluminosilicate azide cancrinite and its use for removal of heavy metal ions. The main objective of this study was to investigate the conversion of zeolite-A into cancrinite under optimized synthesis conditions. In our study, it is aimed to remove some heavy metal ions such as Cd2+, Pb2+, and Ni2+ from aqueous solutions by adsoprtion on synthesized aluminosilicate azide cancrinite and to investigate the kinetics and equilibrium parameters involved during this adsorption. The parameters in this study included initial concentration, contact time, temperature, and adsorbent dosage. Moreover, an attempt has been made to investigate thermodynamic quantities such as equilibrium constant (Kc), free energy (ΔG°), entropy (ΔS°), and enthalpy (ΔH°).

qe =

Co − Ce V m

(1)

where Co is the initial metal ion concentration (mg·L−1); Ce is the equilibrium metal ion concentration (mg·L−1); V is the volume of the solution (L); and m is the amount of the adsorbent (g)

2. EXPERIMENTAL SECTION 2.1. Chemicals and Materials. A commercial grade zeolite-A (69836) was supplied from Fluka company (Italy). Sodium hydroxide, NaOH with 97 wt % purity, sodium azide, NaN3 purity of 99 wt %, and nickel nitrate Ni(NO3)2 98 wt % were all purchased from Molychem (India). Lead nitrate, Pb(NO3)2 (99 wt %), and cadmium nitrate, Cd(NO3)2 (99 wt %), were obtained from Merck (India). All chemicals and materials used in this study were commercially available and used without further purification. Distilled water was used throughout the experiments for preparation of solutions. 2.2. Azide Cancrinite Synthesis. Aluminosilicate azide cancrinite was synthesized hydrothermally by using zeolite-A as a starting material. Sodium hydroxide (80 mmol), sodium azide (108 mmol), and zeolite-A (0.9132 mmol) were dissolved in distilled water (20 mL) and stirred for 15 min. The homogeneous reaction mixture obtained was transferred into a Teflon lined stainless steel autoclave and sealed. The autoclave was kept in the oven at 373.15 K, for 1 week. The gel formed reacts hydrothermally in Teflon lined steel autoclave. The product obtained was recovered by filtration, washed with distilled water a number of times, and dried at 373.15 K. 2.3. Cancrinite Characterization. White polycrystalline product of aluminosilicate azide cancrinite, Na8[AlSiO4]6(N3)2.4(H2O)4.6, was characterized by appropriate physicochemical techniques including FT-IR, XRD, SEM, TGA, and BET surface area analysis. IR absorption study (KBr pellets) was performed on a Shimadzu, 8400-S FT-IR spectrophotometer in the range of (4000 to 400) cm−1. The

3. THEORY Aiming at evaluating the adsorption kinetics, it is essential to consider the theory of adsorption for heavy metal ions by azide cancrinite. In the present investigation, Langmuir40 and Freundlich41 adsorption models were used to determine the adsorption equilibrium between the solid adsorbent and the aqueous heavy metal ions. The adsorption isotherms of metal ions on cancrinite experiments were conducted using various dosage of cancrinite ((0.1−0.5) g) in 50 mL of solutions containing metal ions in 100 mL Teflon bottles with all other optimum parameters. The bottles were shaken time to time in the oven. Solutions containing metals were filtered through Whatman filter paper (no. 41). The concentration of metal ions was determined by classical titration method with EDTA as a complexing agent. The adsorption percentage was calculated using following formula, %removal =

Co − Ce × 100 Co

(2)

where C o and C e (mg·L −1 ) are the initial and final concentrations of metal ion in its aqueous solution, respectively. 3.1. Adsorption Isotherms. Langmuir40 is the simplest type of theoretical isotherm which describes quantitatively the formation of monolayer of adsorbate on the outer surface of the adsorbent, and after that no further adsorption takes place. B



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Thereby the Langmuir represents the equilibrium distribution of metal ions between the solid and liquid phases. Langmuir isotherm applies to adsorption on completely homogeneous surfaces with negligible interaction between adsorbed molecules that shows the form Qe =

Q obCe 1 + bCe

(3)

where Qe (mg.g−1) is the amount of adsorbed metal ions, Ce (mg·L−1) is the concentration of metal ions at equilibrium, Qo (mg.g−1) is the maximum adsorption amount of metal ions, and b (mg·L−1) is the equilibrium adsorption constant which is related to the affinity of the binding sites. The linear form of the equation is

1 1 1 = + Qe Qo bQ oCe

(4) Figure 3. X-ray powder diffraction profile and major hkl planes for Na8[AlSiO4]6(N3)2.4 (H2O)4.6 cancrinite, Bragg’s angle θ, intensity I.

When 1/Qe is plotted against 1/Ce, a straight line having a slope of 1/bQo with an intercept at 1/Qo is obtained. For the adsorption of organic and inorganic compounds in solutions, Freundlich41 isotherm is also very useful, which is given by eq 5 Q e = K f (Ce)1/ n

(5)

−1

Kf (mg·g ) is Freundlich constant related to maximum adsorption capacity; it is a temperature dependent constant, and n is a constant related to surface homogeneity. The linearized forms of Langmuir and Freundlich eqs 6 and 7

Ce C 1 = + e Qe Q ob Qo log Q e = log K f +

(6)

1 log Ce n

Figure 4. SEM picture for Na8[AlSiO4]6(N3)2.4 (H2O)4.6 cancrinite.

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When log Qe is plotted against log Ce, a straight line having a slope of 1/n with intercept at log Kf is obtained.

4. RESULTS AND DISCUSSION 4.1. Characterization of Azide Cancrinite. 4.1.1. FT-IR Spectroscopy. Fourier transform infrared spectroscopy (FTIR) was usually employed as an additional probe to evidence the presence of the −OH group as well as an additional other

Figure 5. Thermogravimetric analysis (TGA) graph for Na8[AlSiO4]6(N3)2.4 (H2O)4.6 cancrinite, temperature T, percent weight loss Wt.

organic and inorganic species. The fabricated aluminosilicate azide cancrinite was characterized by FT-IR in the range (4000−400) cm−1. The FT-IR spectrum of as-synthesized azide cancrinite is shown in Figure 2. The sharp band at 1650 cm−1 and broad band at 3536 cm−1 are due to O−H vibrations42−45 of adsorbed water on the cancrinite surface. Apart from these vibrations, the absorption band at 2065 cm−1 confirms incorporation of azide anion in cancrinite cages. Formation of framework of aluminosilicate azide cancrinite was confirmed by asymmetric stretching ∼995 cm−1, symmetric stretching ∼570, 622, and 682, and bending mode at 428 cm−1.

Figure 2. IR spectrum of Na8[AlSiO4]6(N3)2.4(H2O)4.6 cancrinite, percent transmittance %T, wavenumber υ. C



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Figure 6. BET Surface area analysis and BJH pore volume graph for Na8[AlSiO4]6(N3)2.4 (H2O)4.6 cancrinite, relative pressure P/Po, volume V.

Figure 7. Effect of contact time on the extent of adsorptions at different temperatures for (a) Pb2+, (b) Cd2+, and (c) Ni2+ by using azide cancrinite, contact time t, percent adsorption %A.

Figure 8. Effect of initial concentration of heavy metal ions on the extent of adsorptions at different temperatures for (a) Pb2+, (b) Cd2+, and (c) Ni2+, (contact time =180 min and adsorbent dose =0.5 g). Initial concentration C, percent adsorption %A.

4.1.2. Structure Refinement. The crystal structure of synthesized aluminosilicate azide cancrinite was refined using D



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Table 1. Metal Ion Characteristic Parameters, Metal Ion M2+, Ionic Radius Ir, Hydrated Radius Hr, Electronegativity X, Hydration Enthalpy Hhyd M2+ 2+

Ni Cd2+ Pb2+

Ir/pm

Hr/pm

X/Pauling

Hhyd/kJ·mol−1

69 109 133

438 426 401

1.91 1.69 2.33

−2096 −1806 −1480

the Rietveld refinement. The X-ray diffraction powder pattern for cancrinite is shown in Figure 3. In aluminosilicate azide cancrinite refinement was performed on considering basic aluminosilicate cancrinite as a starting model in a space group P63. Framework atoms aluminum and silicon were placed at (1/4, 0, 1/2) and (1/4, 1/2, 0) sites, respectively, framework oxygen atom (O1 to O5) at different sites. Sodium atoms were refined at two different positions with occupancy factor 0.5, one of the nitrogen at (0,0, ≈ 0.61) position and another nitrogen on (0,0, ≈ 0.75) position. The structure refinement showed that the unit cell parameter (a) in aluminosilicate azide cancrinite is 1.25899 nm. 4.1.3. Crystal Morphology. Morphological analysis of aluminosilicate azide cancrinite performed by SEM is shown in Figure 4. The observed crystal morphology supports the hexagonal structure. Some of the crystals show longer needle like shapes, but the average size of most of the crystals ranges from (0.010 to 0.025) nm. 4.1.4. Thermogravimetric Analysis. The weight temperature behavior of the azide cancrinite was studied in detail by thermogravimetric method (Figure 5). In the case of azide cancrinite TGA shows loss in weight about 5 % due to enclathrated water molecules and about 2.5 % loss in weight in the region (873.15 to 973.15) K due to decomposition of azide anions. The composition of azide cancrinite was determined quantitatively on the basis of weight loss of water molecule and nitrogen. 4.1.5. Surface Area of Adsorbent. Figure 6 shows N2 adsoprtion-desorption isotherm for azide cancrinite. It reveals that the product obtained, azide cancrinite, has typical IV N2 adsorption desorption isotherms with H1 hysteresis which indicates that the sample serves the cylindrical mesopores. Practically it is observed that the surface area of cancrinite is more as compared to zeolitic material like sodalite.27,46 Based on the isotherms, the specific area obtained from BET method is 16 m2·g−1 and BJH pore volume is 0.0185 g−1.

Figure 9. Langmuir isotherm plots for adsorption of heavy metals onto azide cancrinite at (298.15, 323.15, and 348.15) K temperatures for (a) Pb2+, (b) Cd2+, and (c) Ni2+.

4.2. Effect of Contact Time. For determination of time dependence of sorption, 0.5 g of azide cancrinite was mixed with 0.01 N metal ion solutions in Teflon container and shaken periodically in the oven. After filtration the equilibrium concentrations were determined by titrating the solution with EDTA. For cadmium and lead Eriochrome black-T indicator was used, whereas murexide indicator for nickel. Using constant adsorbent concentrations (0.5 g/50 mL), removal (%) of heavy

Table 2. Adsorption Capacities of Pb2+, Cd2+, and Ni2+ on Various Low-Cost Adsorbents, Metal Ion M2+, Temperaturea T, Maximum Adsorption Amount Q0, Slope m, Intercept y, Langmuir Constant b, Correlation Factorb R2, Adsorption Intensity n, and Freundlich Isotherm Constant Kf Langmuir T/K

m

y

b

Q0/ mg·g−1

R2

m

y

n

Kf/ mg·g−1

R2

Pb2+

298.15 323.15 348.15 298.15 323.15 348.15 298.15 323.15 348.15

1.891 0.353 0.260 2.904 0.061 0.261 2.740 0.512 0.325

0.026 0.022 0.019 0.027 0.025 0.022 0.033 0.029 0.026

0.014 0.062 0.073 0.009 0.412 0.084 0.012 0.057 0.08

38.46 45.46 52.63 37.04 40.00 45.46 30.30 34.48 38.46

0.996 0.996 0.978 0.987 0.990 0.988 0.922 0.991 0.981

0.809 0.764 0.459 0.716 0.500 0.42 0.878 0.633 0.467

0.582 0.369 0.152 0.458 0.286 0.124 0.504 0.371 0.181

1.236 1.309 2.179 1.397 2.000 2.381 1.139 1.58 2.141

3.82 2.34 1.42 2.87 1.93 1.33 3.19 2.35 1.52

0.988 0.987 0.995 0.979 0.981 0.993 0.990 0.973 0.948

Cd2+

Ni2+

a

Freundlich

M2+

Standard uncertainty u is u(T) = 0.5 K. bStandard uncertainty u is u(R2) = 0.044. E



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after 150 min at its equilibrium from the adsorbent surface. However, the removal of Ni2+ increased with contact time and reached a maximum at 150 min with the removal efficiency 60 %. 4.3. Effect of Temperature. The adsorption of Pb2+, Cd2+, and Ni2+ ions onto azide cancrinite at different temperatures increases sharply during the 30 min and keeps increasing slowly until the equilibrium is reached as shown in Figure 7a−c. This increase in adsorption capacity of azide cancrinite with temperature confirms an endothermic nature of process. Careful inspection of Figure 7a−c shows that removal efficiency of Pb2+, Cd2+, and Ni2+ is around 95 % at 348.15 K. Ion dipole forces between metal cations and water molecules (from metal ion solution) weaken at higher temperature and metal ion exchange increases. As a result, the overall effect is an increase in adsorption of heavy metal on cancrinite. 4.4. Effect of Initial Concentration of Heavy Metal Ions. Figure 8a−c shows the removal of Pb2+, Cd2+, and Ni2+ on azide cancrinite, as a function of initial metal ion concentration ((20−120) mg·L−1) while keeping the other parameters constant. From the results, we can conclude that uptake of metal ion by azide cancrinite increases significantly and gradually with metal ion concentration gradient and temperature. The ionic radius of metal ions is inversely related to the charge density and electrostatic attraction which limits the interaction of the metal ions with the adsorption sites. Thus, metals with higher electronegativity sorb more readily on the surface of the adsorbent. The obtained selectivity series is in agreement with the metal ions electronegativity, namely Pb2+(2.33) > Ni2+(1.91) > Cd2+(1.69), as shown in Table 1. Hydration of metal ion also plays a very significant role in the adsorption process.47 Absolute value of the enthalpy of hydration increases with increase in ionic size. Enthalpy of hydration indicates that, the Pb2+ aq. ion will have more accessibility to the adsorbent surface,48 followed by Cd2+ aq. and Ni2+ aq. Table 2 reveals that the extent of adsorption process is in the order Pb2+ > Cd2+ > Ni2+. 4.5. Adsorption Isotherms. Removal experiments for lead, cadmium, and nickel metal ions by cancrinite were carried out successfully. The Langmuir (K f) and Freundlich (Qo) parameters and statistical fits of the adsorption data to eqs 6 and 7 are given in Table 2 (R2 > 0.9). When two isotherm models are compared, values of coefficient of determination showed that Freundlich has better performance than Langmuir for representing the equilibrium data (Table 2). Figures 9a−c and 10a−c display linear plots of 1/Qe versus 1/Ce and log Qe versus log Ce for lead, cadmium, and nickel at various temperatures. The results obtained show that, maximum adsorption capacity, Qo (mg·g−1), for lead is 52.63, cadmium 45.46, and for nickel it is 38.46, indicating conducive results for azide cancrinite to be tagged a prospective low cost

Figure 10. Freundlich isotherms plot for adsorption of heavy metals onto azide cancrinite at (298.15, 323.15, and 348.15) K temperatures for (a) Pb2+, (b) Cd2+, and (c) Ni2+.

Table 3. Adsorption Capacities of Pb2+, Cd2+, and Ni2+ on Various Low-Cost Adsorbents adsorbent

Pb2+/mg·g−1

Cd2+/mg·g−1

Ni2+/mg·g−1

modified kaolinite clay brown marine macro algae biofilms and associated minerals iodate sodalite modified lignite fly ash azide cancrinite

40.00

13.23

18

50.40

39.50

19

40.00

10.40

20

50.00

43.48 21.23

52.63

45.46

38.45

ref

22 21 present study

metal ions by azide cancrinite shows increase in adsorption efficiency with contact time as shown in Figure 7a−c. Figure 7a−c shows removal of Pb2+, and Cd2+, increases gradually with contact time. Almost 95 % of the Pb2+ and Cd2+ was removed

Table 4. Thermodynamic Parameters of the Present Study Temperature Ta (298.15, 323.15, and 348.15) K, Heavy Metal Ion M2+, Gibbs Free Energy ΔG°, Distribution Coefficient Kc, Enthalpy Change ΔH, and Entropy Change ΔS ΔG/kJ·mol−1 M

298.15 K

323.15 K

348.15 K

298.15 K

323.15 K

348.15 K

ΔH°/kJ·K−1·mol−1

ΔS°/J·K−1· mol−1

2+

−0.984668 −0.334472 −0.614438

−5.45946 −2.81701 −3.64949

−8.53805 −6.17714 −6.69214

1.488 0.874 0.787

7.638 2.855 3.893

19.129 8.459 10.104

101.901 79.078 81.988

351.16 266.91 279.74

Pb Cd2+ Ni2+ a

Kc

2+

Standard uncertainty u is u(T) = 0.5 K. F



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solutions have been studied. The positive values of ΔH° and ΔS° indicate that the sorption of Pb2+, Cd2+, and Ni2+ ions on prepared cancrinite is an endothermic process. The results obtained show that aluminosilicate azide cancrinite can be used effectively for removal of metal cations from aqueous solutions.

adsorbent (Table 2). The potential use of adsorbent of large void pore zeolite and other materials are explored by large number of scientists, but cancrinite also shows good adsorption capacity as compared to other adsorbent materials such as modified kaolinite clay,20 brown marine macro algae,21 biofilms and associated minerals,22 modified lignite fly ash,23 and iodate sodalite24 as their results are compared in Table 3. The Freundlich isotherm parameter also gives enough evidence for the feasibility of adsorption on cancrinite. The n > 1 value indicates the spontaneity of adsorption49,50 of all three metals on cancrinite and reveals that adsorption was a favorable process. 4.6. Thermodynamic Study. In order to determine the thermodynamic feasibility and the thermal effects of the sorption, the Gibbs free energy (ΔG°), the entropy change (ΔS°), and enthalpy change (ΔH°) were calculated. These parameters were calculated from variations of thermodynamic distribution coefficient, Kc, with change in temperature. The distribution coefficient is given by eq 8 C Kc = a Ce

■

*Phone. (+91)9421831839. E-mail: ashokborhade2007@ yahoo.co.in. Funding

Authors are thankful to CSIR, New Delhi, for financial support (Project Scheme No.: 01/(2745)/13/EMR-II), HPT Arts and RYK Science College, Nashik, for providing necessary facilities. TAK is thankful to CSIR, New Delhi for SRF fellowship. Notes

The authors declare no competing financial interest.

■ ■

ACKNOWLEDGMENTS Authors are thankful to SAIF, IIT Powai, and Dr. S.V. Mahajan, Head, Physics Department for providing XRD Analysis.

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where Kc is the distribution coefficient of adsorption, Ca is the remaining concentration of metal ions, and Ce is the equilibrium concentration of metal ions. To calculate the different thermodynamic parameters, vant Hoff equation was used which is given as follows: ΔG° = −RT ln(Kc) −1

where R is universal gas constant (8.314 J·mol ·K ) and T is temperature (K) ln(Kc) = −

ΔH ° ΔS° + (RT ) R

ΔG° = ΔH ° − T ΔS°

REFERENCES

(1) Lin, S. H.; Juang, R. S. Heavy metal removal from water by sorption using surfactant-modified montmorillonite. J. Hazard. Mater. 2002, 92, 315−326. (2) Barakat, M. A. New trends in removing heavy metals from industrial wastewater. Arab. J. Chem. 2011, 4, 361−377. (3) Babel, S.; Skurniawan, T. A. Low-cost adsorbents for heavy metals uptake from contaminated water: a review. J. Hazard. Mater. 2003, 97, 219−243. (4) Inglezakis, V. J.; Loizidou, M. D.; Grigoropoulou, H. P. Ion exchange of Pb2+, Cu2+, Fe3+ and Cr3+ on natural clinoptilolite: selectivity determination and influence of acidity on metal uptake. J. Colloid Interface Sci. 2003, 261, 49−54. (5) Moore, J. Ramamoorty, S. Appl. Monitor. Assess; Springer-Verlag, New York, 1984. (6) Ahmaruzzaman, M. Adsorption of phenolic compounds on lowcost adsorbents: A review. Adv. Colloid Interface Sci. 2008, 43, 48−67. (7) Apak, R.; Tutem, E.; Hugul, M.; Hizal. Heavy metal cation retention by unconventional sorbent (red mud and fly ashes). J. Water Resour. 1998, 32, 430−440. (8) Banerjee, K.; Cheremisinoff, P. N.; Cheng, S. L. Adsorption kinetics of o-xylene by fly-ash. Water Resour. 1997, 31, 249−261. (9) Panday, K. K.; Prasad, G.; Singh, V. N. Copper(II) removal from aqueous solutions by fly ash. Water Resour. 1985, 19, 869. (10) Ferraiolo, G.; Zilli, M.; Converti, A. Fly ash disposal and utilization. J. Chem. Technol. Biotechnol. 1990, 47, 281−306. (11) Baltpurvins, K. A.; Burns, R. C.; Lawrance, G. A.; Stuart, A. D. Effect of electrolyte composition on zinc hydroxide precipitation by lime. Water Resour. 1997, 31, 973. (12) Rangel-Mendez, J. R.; Streat, M. Adsorption of cadmium by activated carbon cloth: Influence of surface oxidation and solution pH. Water Resour. 2002, 36, 1244−1252. (13) Hasar, H. Adsorption of nickel (II) from aqueous solution onto activated carbon prepared from almond husk. J. Haz. Mater. 2003, 97, 49−57. (14) Aly, H. M.; Daifullah, A. A. M. Potential use of bagasse pith for the treatment of wastewater containing metals. Adsorp. Sci. Technol. 1998, 16, 33−38. (15) Vinod, K.; Gupta, C. K.; Jain; Imran, Ali; Sharma, M.; Saini, V. K. Removal of cadmium and nickel from wastewater using bagasse fly asha sugar industry waste. Water Resour. 2003, 37, 4038−4044. (16) Daneshvar, N.; Salari, D.; Aber, S. Chromium adsorption and Cr (VI) reduction to trivalent chromium in aqueous solutions by soya cake. J. Hazard. Mater. 2002, 94, 49−61.

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Corresponding Author

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The values of ΔH° and ΔS° are obtained from the slope and the intercept of each plot (ln Kc versus 1/T) for cancrinite, which are evaluated by a curve fitting program. The results obtained for thermodynamic quantities for sorption of heavy metal ions Pb2+, Cd2+, and Ni2+ on cancrinite are summarized in Table 4. The positive values of ΔH° for all heavy metal ions studied suggest the endothermic nature of the adsorption onto azide cancrinite.56,57 However, the negative value of ΔG° decreased with an increase in temperature, indicating that the spontaneous nature51−55 of adsorption is inversely proportional to temperature. The structural change at active sites and in ion exchanged cancrinite is evidenced by entropy change (ΔS°) at elevated temperature during the adsorption process.58 The positive value of ΔS° shows enhanced randomness at solid/ liquid interface during the adsorption process.

5. CONCLUSION Aluminosilicate azide cancrinite was successfully synthesized by low temperature hydrothermal method and is used as an adsorbent for removal of Pb2+, Cd2+, and Ni2+ from aqueous solutions. It is evident that this conversion of zeolite-A into a beneficial product, azide cancrinite, could prove to be effective in removing heavy metals. The Langmuir and Freundlich models fit well to the experimentally obtained data for the adsorption of Pb2+, Cd2+, and Ni2+. For the adsorption process, effect of various parameters like temperature, contact time, and initial concentration of heavy metal ions from their aqueous G



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(42) Farmer, V. C.; Mineralogical Society London, 1974, Monograph 4. (43) Flanigen, E. M.; Khatami, H.; Szymanski, H. A. Infrared structural studies of zeolite frameworks. Adv. Chem. Ser. Molecular Sieve Zeolites 1971, 16, 201−229. (44) Henderson, C. M. B.; Taylor, D. Infrared spectra of anhydrous members of the sodalite family. Spectrochim. Acta 1977, 33, 283−290. (45) Moenke, H. Mineralspektren; Akademie-Verlag: Berlin, 1962. (46) Niwa, M.; Katada, N.; Okumura Characterization and Design of zeolite catalysts; Springer: New York, 2010; Vol. 141. (47) Peric, J.; Trigo, M.; Medvidović, N. Removal of zinc, copper and lead by natural zeolite-a comparison of adsorption isotherms. J. Water Resour. 2004, 38, 1893−1899. (48) Keane, M. Role of alkali metal co-cation in the ion exchange of Y zeolites II. Copper ion-exchange equilibria. J. Microporous Mater. 1995, 3, 385−394. (49) Tan, I. A. W.; Hameed, B. H.; Ahmad, A. L. Equilibrium and kinetic studies on basic dye adsorption by oil palm fibre activated carbon. Chem. Eng. J. 2007, 127, 111−119. (50) Giles, C. H.; Smith, D. A general treatment and classification of the solute adsorption isotherm Theoretical. J. Colloid Interface Sci. 1974, 47, 755−765. (51) Kumar, P. S.; Gayathri, R. Adsorption of Pb2+ ions from aqueous solutions onto bael tree leaf powder: Isotherms, kinetics and thermodynamics study. J. Eng. Sci. Technol. 2009, 4, 381−399. (52) Sharma, P.; Baskar, R. C.; Chung, W. J. Removal of methylene blue from aqueous waste using rice husk and rice husk ash. Desalination 2010, 259, 249−257. (53) Surchi, K. M. S. Agricultural Wastes as Low Cost Adsorbents for Pb Removal: Kinetics, Equilibrium and Thermodynamics. Int. J. Chem. 2011, 3, 103−112. (54) Payne, K. B.; Abdel-Fattah, T. M. Adsorption of Divalent Lead Ions by Zeolites and Activated Carbon: Effects of pH, Temperature, and Ionic Strength. J. Environ. Sci. Health. 2004, A 39, 2275−2291. (55) Suchithra, P. S.; Anirudhan, T. S. Equilibrium, kinetic and thermodynamic modeling for the adsorption of heavy metals onto chemically modified hydrotalcite. Ind. J. Chem. Technol. 2010, 17, 247−259. (56) Yousef, R. I.; El-Eswed, B.; Al-Muhtaseb, A. H. Adsorption characteristics of natural zeolites as solid adsorbents for phenol removal from aqueous solutions: Kinetics, mechanism, and thermodynamics studies. Chem. Eng. J. 2011, 171, 1143−1149. (57) Han, R.; Zhang, J.; Han, P.; Wang, Y.; Zhao, Z.; Tang, M. Study of equilibrium, kinetic and thermodynamic parameters about methylene blue adsorption onto natural zeolite. Chem. Eng. J. 2009, 145, 496−504. (58) Bao, W.; Zou, H.; Gan, S.; Xu, X.; Ji, G.; Zheng, K. Adsorption of heavy metal ions from aqueous solutions by zeolite based on oil shale ash: Kinetic and equilibrium studies. Chem. Res. Chin. Univ. 2013, 29, 126−131.

(17) Dimitrova, S. V.; Mehandgiev, D. R. Lead removal from aqueous solution by granulated blast furnace slag. Water Resour. 1998, 32, 3289−3292. (18) Danis, T. G.; Albanis, T. A.; Petrakis, D. E.; Pomonis, P. J. Removal of heavy metal mesoporous alumina aluminum phosphates. Water Resour. 1998, 32, 295−302. (19) Mathialagan, T.; Viraraghavan, T. Adsorption of cadmium from aqueous solutions by perlite. J. Hazard. Mater. 2002, 94, 291−303. (20) Amer, M. W.; Khalili, F. I.; Awwad, A. M. Adsorption of lead, zinc and cadmium ions on polyphosphate-modified kaolinite clay. J. Environ. Chem. Ecotox. 2010, 2, 1−8. (21) Freitas, O.; Martins, R.; Delerue-Matos, C.; Boaventura, R. Removal of Cd(II), Zn(II) and Pb(II) from aqueous solutions by brown marine macro algae: Kinetic modeling. J. Hazard. Mater. 2007, 153, 493−501. (22) Lee, M.; Yi, G.; Joon, A. B. Conversion of coal fly ash into zeolite and heavy metal removal characteristics of the products. Korean J. Chem. Eng. 2000, 17, 325−331. (23) Malarvizhi, T. S.; Santhi, T.; Manonmani, S. A Comparative Study of Modified Lignite Fly Ash for the Adsorption of Nickel from Aqueous Solution by Column and Batch Mode Study. Res. J. Chem. Sci. 2013, 3, 44−53. (24) Borhade, A. V.; Dholi, A. G.; Wakchaure, S. G.; Tope, D. R. Chemical modification of coal fly ash into iodate sodalite and its use for the removal of Cd2+, Pb2+, and Zn2+ from their aqueous solutions. Desalin. Water Treat. 2012, 50, 157−169. (25) Javed, M. A.; Bhatti, H. N.; Hanif, M. A.; Nadeem, R. Kinetic and equilibrium modeling of Pb (II) and Co (II) sorption onto rose waste biomass. Sep. Sci. Technol. 2007, 42, 3641−3656. (26) Mead, P.; Weller, M. Synthesis, structure, and characterization of halite sodalite: M8[AlSiO4]6(XO3)x(OH)2x; M= Na, Li, or K; X= Cl, Br, or I. Zeolite 1995, 15, 561−568. (27) Basaldella, E. I.; Vazguez, P. G.; Incolano, F.; Caputo, O. Chromium removal from water using LTA zeolites: Effect of pH. J. Colloid Interface Sci. 2007, 313, 574−578. (28) Jha, V. K.; Nagae, M.; Matsuda, M.; Miyake, M. Zeolite formation from coal fly ash and heavy metal ion removal characteristics of thus-obtained Zeolite X in multi-metal systems. J. Environ. Manage. 2009, 90, 2507−2514. (29) Erden, E.; Karapinan, N.; Donat, R. The removal of heavy metal cations by natural zeolites. J. Colloid Interface Sci. 2004, 380, 309−314. (30) Ouki, S. K.; Kavannagh, M. Performance of natural zeolites for the treatment of mixed metal-contaminated effluents. Waste Manage. Res. 1997, 15, 383−394. (31) Meier, W. M.; Oslen, C D.; Baerlocher, H. Atlas of Zeolite Structure Types; Elsevier: London, 1996. (32) Breck, D.; Kieger, R. E. Zeolite molecular sieves; Kieger: Malabar, FL, 1984 (33) Jarchow, O. H. Die Strukturverfeinerung des Zwei-dimensional Fehlgeordneten Natrium-metaphosphates Na2H2P4O12. Acta Crysallogr. 1964, 17, 1253−1262. (34) Pauling, L. The structure of some sodium and calcium aluminosilicates. Proc. Natl. Acad. Sci. U.S.A. 1930, 16, 453−459. (35) Jarchow, O. Atomanordnung und Strukturverfeinerung von cancrinite. Kristallogr 1965, 122, 407−442. (36) Goßner, B.; Mußgnug, F. Ü ber Davyn und seine Beziehungen zu Hauyn und Cancrinit. Z. Kristallogr. 1930, 73, 53−67. (37) Nah, I. W.; Hwang, K. Y.; Jeon, C.; Choi, H. B. Removal of Pb ion from water by magnetically modified zeolite. Miner. Eng. 2006, 19, 1452−1455. (38) Bose, P.; Bose, M. A.; Kumar, S. Critical evaluation of treatment strategies involving adsorption and chelation for wastewater containing copper, zinc and cyanide. Adv. Environ. Res. 2002, 7, 179−195. (39) Barakat, M. A. Adsorption of heavy metals from aqueous solutions on synthetic zeolite. Res. J. Environ. Sci. 2008, 2, 13−22. (40) Langmuir, I. The adsorption of gases on plane surfaces of glass, mica and platinum. J. Am. Chem. Soc. 1918, 40, 1361−1403. (41) Freundlich, H.; Heller, W. On Adsorption in Solution. J. Am. Chem. Soc. 1939, 61, 2228−2232. H


Removal of Heavy Metals Cd2+, Pb2+, and Ni2+ From Aqueous

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