Effective removal of Th4+, Pb2+, Cd2+, malachite green, methyl violet and methylene blue from their aqueous solution by amylopectin dialdehyde-Schiff base

Journal Pre-proof Effective removal of Th4+ , Pb2+ , Cd2+ , malachite green, methyl violet and methylene blue from their aqueous solution by amylopectin dialdehyde-Schiff base Dinabandhu Sasmal (Conceptualization) (Methodology) (Software) (Writing - original draft), Shankha Banerjee (Investigation), Sanjib Senapati (Visualization) (Investigation), Tridib Tripathy (Supervision) (Conceptualization) (Methodology) (Writing - review and editing)

PII:

S2213-3437(20)30089-0

DOI:

https://doi.org/10.1016/j.jece.2020.103741

Reference:

JECE 103741

To appear in:

Journal of Environmental Chemical Engineering

Received Date:

24 November 2019

Revised Date:

23 January 2020

Accepted Date:

2 February 2020

Please cite this article as: Sasmal D, Banerjee S, Senapati S, Tripathy T, Effective removal of Th4+ , Pb2+ , Cd2+ , malachite green, methyl violet and methylene blue from their aqueous solution by amylopectin dialdehyde-Schiff base, Journal of Environmental Chemical Engineering (2020), doi: https://doi.org/10.1016/j.jece.2020.103741

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Effective removal of Th4+, Pb2+, Cd2+, malachite green, methyl violet and methylene blue from their aqueous solution by amylopectin dialdehydeSchiff base Dinabandhu Sasmal1, Shankha Banerjee2, Sanjib Senapati2, TridibTripathy 1* 1

Postgraduate Division of Chemistry, Midnapore College (Autonomous), Midnapore,

Paschim Medinipur, 721101, West Bengal, India. Department of Biotechnology, BJM School of Bioscience, Indian Institute of

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Technology Madras, Chennai 600036, India.

Corresponding author E-mail: [email protected], [email protected] Tel/Fax: +913222275847 *

Highlights

Synthesis of three Schiff bases using selectively oxidised amylopectin and three

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Graphical Abstract

primary amines

Adsorption studies of the toxic metal ions and dyes with the Schiff bases

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Selectivity of adsorption study

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complexation studies theoretically by Density Functional Theory (DFT)

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Studies of adsorption, dynamics, kinetics and isotherms

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ABSTRACT In the present study, amylopectin was oxidized to amylopectin dialdehyde by selective cleavage of C2-C3 bond of anhydroglucose units in the amylopectin chain by sodium metaperiodate to generate two aldehyde groups and modified to Schiff bases by the reactions with ethanolamine, hydrazine and semicarbazide. The well characterized Schiff bases were used as adsorbents for Th4+, Pb2+, Cd2+ ions and three cationic dyes namely malachite green, methyl violet and methylene blue. Among the three Schiff bases, amylopectin dialdehyde-

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ethanolamine (APDA-EA) showed stronger and selective adsorbent towards Th4+ ions and malachite green dye. The adsorption data was found to follow pseudo second order kinetics and Langmuir adsorption isotherm. The maximum adsorption capacity of APDA-EA towards

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Th4+ ions was 94.68 mg/g and towards malachite green dye it was 89.84 mg/g. The greater selectivity of APDA-EA towards Th4+ ion was explained theoretically by Density Functional

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Theory calculations.

Density Functional Theory. 1.

INTRODUCTION

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KEYWORDS: Amylopectin based Schiff base; Metal ions removal; Dyes green removal;

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Water pollution caused by toxic heavy metal ions, coloured waste effluents containing synthetic dyes and other organic pollutants is a world-wide environmental problem due to

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their toxic and hazardous effects on the environment and the living organisms [1]. Heavy

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metal ions and synthetic dyes are non-biodegradable and can be accumulated in living tissues causing adverse effect on human health. Therefore, the presence of such pollutants particularly in the aquatic environment must be controlled. Th4+ ions enter into the environment, particularly in the water through effluents and waste water from the mining industries and nuclear power plants. Besides those, Th4+ ions come to the environment from the laboratory activities [2]. Thorium (Th4+) ion is radiotoxic

and one of the industrial pollutants. Thorium is a α-emitter when it enters to the tissues of human beings or animals through air or water causes lung cancer, pancreas cancer, bone cancer [3].

The hazardous metal ions like Pb2+ and Cd2+ ions are also entire to the

environment through human activities like metal plating, batteries manufacturing and refining. The intake of Pb2+ and Cd2+ contaminated water to living organisms causes several physiochemical and neurological disorder [4, 5]. Thus, water pollution caused by Th4+, Pb2+ and Cd2+ ions lead to the ecological disbalance and have a threat to the human health.

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Again, malachite green (MG), methyl violet (MV) and methylene blue (MB) the synthetic cationic hazardous dye which are used extensively in textile, agriculture, paper and agriculture industries. The waste effluents released by these industries containing MG, MV

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and MB dye again become a serious threat to the environment and to the living organisms. Incorporation of MG, MV and MB to the human body by any means results carcinogenesis,

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mutagenesis, respiratory problems and chromosomal disorders [6-8].

Hence, to overcome

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the adverse effects of MG and Th4+ ions on the environment and onto the living organisms it is very important to remove them from the contaminated water. There are several techniques that are used to reduce the heavy metal ions content in the polluted water include chemical

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precipitation, solvent extraction, membrane processing, photocatalysis, electrolytic techniques, ion exchange and adsorptions [9-11].

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Adsorption process is a highly preferable method for the removal of toxic heavy metal ions

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and dyes from the waste water because of its several advantages of high efficiency, economic feasibility and easy operation [12, 13]. Several adsorbents have been used so far to remove heavy metal ions and dyes including activated carbon [14], inorganic nano materials [15], metal hydroxide sludges [16], ion imprinted polymers [17] and ion exchange resins [18]. However, most of them have drawbacks, such as, low adsorption efficiency, high cost, less selective, non-biodegradable in nature and slow adsorption rate. To overcome these draw

backs scientists and technologists are interested to prepare natural polysaccharide-based adsorbents including graft copolymers [19] and hydrogels [20, 21] for the removal of toxic heavy metal ions and synthetic dyes from the polluted water. Amylopectin dialdehyde is prepared by the selective cleavage of C2- C3 bond of the anhydro glucose unit (AGU) of amylopectin backbone using sodium metaperiodate [22]. However, it is well known that imines (Schiff base) derived from aldehydes and primary amines can coordinate with metal ions and hence attracted much attention to use such materials as

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adsorbents for the heavy metal ions and organic dyes. Polysaccharide-amine-Schiff bases are widely used to remove heavy metal ions [23-25] and toxic organic dyes [26, 27] from the aquatic environment successfully. However, to the best of our knowledge, the dual adsorbing

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properties of polysaccharide-amine-Schiff bases for Th4+ and MG removal have not reported earlier. Hence the present investigation is focussed on the dual adsorption characteristics, that

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using Amylopectin-amine-Schiff bases.

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is adsorption of radiotoxic Th4+ and a synthetic textile dye, MG from the water medium by

In this study, three Schiff bases are prepared by using amylopectin dialdehyde and three primary amines namely EA, HYD and SEM for adsorption of both Th4+ ions and MG

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dye from their water solution. 2. EXPERIMENTAL

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2.1. Materials

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Amylopectin (AP), Sodium metaperiodate (NaIO4), Ethanolamine (EA), Hydrazine (HYD) and Semicarbazide (SEMI) were obtained from Aldrich Chemical Company, USA. Ammonium hydroxide, Thorium nitrate, Cadmium chloride and Lead chloride were purchased from Himedia Laboratory, Mumbai, India. Methanol and isopropanol were procured from Avra Synthesis Pvt. Ltd. Hyderabad, India. Malachite green, Methyl violet

(MV), Methylene blue (MB) and Dinitrophenyl hydrazine (DNPH) were supplied by E. Merck Ltd. Mumbai, India. Triple distilled water was used in all the experiments. 2.2. Preparation of Amylopectin Dialdehyde (APDA) by Sodium Meta-periodate Oxidation APDA was prepared in water medium by the oxidation of sodium meta per iodate according to the previously reported procedure [28]. A typical synthetic procedure was as follows; 4 ml 0.6 (M) periodic acid was mixed with 10 ml of 3 % AP solution at pH 4, in a 100 ml beaker. The reaction mixture was then stirred by a magnetic stirrer at a constant

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temperature of 50OC. The reaction was carried out in absence of light for about 72 hours. After the prescribed time period (72 h) the reaction mixture was cooled and the product was precipitated using isopropanol as the solvent. The product was dissolved in distilled water

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and reprecipitated in isopropanol and then dried in a vacuum oven. A synthetic scheme is

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2.3. Synthesis of Schiff Bases of APDA

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given in Fig. 1.

Three primary amines namely ethanol amine (EA), hydrazine (HYD) and semicarbazide (SEMI) were used for the Schiff Base preparation with APDA. A typical procedure was

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follows; At first, 6 g of APDA was dissolved in 90 ml methanol-water mixture (1:1 by volume) in a 100 ml beaker. Then solution was divided into three parts and poured in three

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conical flasks (50 ml) separately. Ethanolamine (4 ml), hydrazine (3 g) and semicarbazide (3

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g) were added separately in each of the three solutions. After that, 0.5 g of ammonium acetate was added to each solution separately to keep the pH constant at 5.5 The solutions were then refluxed separately at 500C temperature for 6 hours. The solution become coloured after 2 hours, indicating Schiff bases formation. After the prescribed time period, the solutions were allowed to cool and the three Schiff bases were precipitated by the addition of isopropanol as the solvent. All the three Schiff bases were dissolved in water and reprecipitated by

isopropanol after filtration repeatedly to remove the impurities, the purified products were used for further study. The formation of Schiff bases are schematically represented in Fig. 1. 2.4. Characterization of APDA, APDA-EA, APDA-HYD and APDA-SEMI. 2.4.1. FTIR Spectroscopy Perkin Elmer (L1600300 spectrum two Lita, Lleantrisant, UK) spectrophotometer was used for the FTIR spectral study of the APDA, APDA-EA, APDA-HYD and APDA-SEMI. The IR spectra were taken in KBr pellets and are shown in Fig. S 1.

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2.4.2. 1H NMR Spectroscopy HNMR spectroscopy of the APDA, APDA-EA, APDA-HYD and APDA-SEMI were

performed with a 300MHZ NMR instrument (JEOL, Tokyo, Japan) in D2O solvent at

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250C.The1H NMR spectra of APDA, APDA-EA, APDA-HYD and APDA-SEMI are shown in Fig. S 2 respectively.

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2.4.3. Field Emission Scanning Electron Micrographs Studies

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FESEM images of APDA, APDA-EA, APDA-HYD and APDA-SEMI are given in Fig. 2. A Cam Scan Series 2 (Cambridge Scanning Company, UK) was used for FESEM study. 2.4.4. X-ray Diffraction (XRD) Analysis

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XRD plots of APDA, APDA-EA, APDA-HYD and APDA-SEMI were carried out in X-ray Diffractometer (Rigaku, Japan). CuKα radiation was (λ=1.54 A0) used to take the

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diffraction pattern. The diffraction angle for X-ray analysis was varied from 0o to 80o. The

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XRD plots of all the compounds are given in Fig. S 3. 2.5. Determination of Aldehyde Content in APDA The aldehyde content in APDA was measured spectro photometrically (UV-VIS) by the

2,4-dinitrophenylhydrazone formation according to the previous procedure [28, 29]. A typical procedure was as follows; 3 ml 0.4% APDA was added to 10 ml the 2,4-dinitrophenyl hydrazine solution. The solution was stirred in a magnetic stirrer and allowed to continue the

reaction upto 1 hour. After the prescribed time period the reaction mixture was centrifuged and supernatant was collected for the determination of concentration of unreacted DNPH by UV-VIS spectrophotometer at λ= 361nm. The aldehyde content in APDA was calculated by using following equation 1[28]. Aldehyde concentration (mmol/g) =

Reacted DNPH (mmol/g)/198.14 Conc(%)×10−4

(1)

198.14 g/ mol is the molecular weight of DNPH. 2.6. Determination of point of zero charge (PZC) of the APDA-EA

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The point of zero charge (PZC) is a key parameter of the adsorbents for a adsorption process to investigate the surface charge of the adsorbents. To determine the PZC of the APDA-EA following procedure was followed. Briefly, 0.01 g of APDA-EA was mixed with an aliquot

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of 30 ml 0.1 mole/L NaCl solution at different pHs (2-9). 0.1 mole/L HCl and 0.1 mole/L

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NaOH solution were prepared to adjust the pH of the solution. The resulting mixture solutions were stirred at 300 rpm by a magnetic stirrer for 24 h. After that the final pH of the

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solutions were recorded by a digital pH meter (Systronics model 335, India). The PZC were determined from the plot of difference of pH (ΔpH=pHf - pHi) versus pHi. The point at which

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the ΔpH is equal to zero represents the point of zero charge of the adsorbent APDA-EA. The (ΔpH) versus pHi plot is given in the Fig. 3.

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2.7. Metal ions and Dye Removal Characteristics of APDA-EA, APDA-HYD and AP-SEMI Metal ions and dyes removal characteristics of three synthesized Schiff bases were

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evaluated in three metal ions (namely Th4+, Pb2+ and Cd2+) and in three dyes (namely MG, MV and MB) from their water solutions by batch adsorption mode respectively. A typical procedure was as follows; 20 ml of 0.04 g of each Schiff base (APDA-EA, APDA-HYD and APDA-SEMI) solution in water was mixed with 25 ml of 100 mg/L metal ions’ solution separately in a series of 100 ml Erlenmeyer flask. Again, 20 ml of each dye solution (100 mg/L) was mixed with 15 ml of each Schiff base (0.2 g) separately in 100 ml beakers. All the

solution mixtures were stirred in a magnetic stirrer at pH 5.0, temperature 500C for metal ions (300C for dyes solutions) over a time period of 2 hours with 200 rpm of stirring speed. After the prescribed time period the solutions were centrifuged and the supernatant of each solution mixture was collected. The residual metal ion concentration in all the supernatant was measured in Atomic Absorption Spectrophotometer (Varian spectra Japan). The residual dye in each supernatant was measured by UV-VIS spectrophotometer (Schimadzu 1800, Japan) at λmax 613 nm for MG, 576 nm for MB and 677 nm for MV. The metal ions and dyes removal

Metal ion or dye removal capacity q =

C0 −Ce m

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capacities by the Schiff bases were calculated by using the equation 2 [28]. ×V

(2)

Where, C0 and Ce refer to the initial and equilibrium concentrations of the metal ions

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dyes solutions (mol/L), V is the volume of each metal ions and dyes solutions (L) and ‘m’ is the mass of each Schiff base in g.

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2.8. Metal ion adsorption

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2.8.1. Effect of pH

The solution pH is an important parameter to effect the adsorption process. The pH of

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the solution was varied from 2 to 8 to study the pH effect of the metal ion adsorption onto the surface of APDA-EA at a constant temperature 500C for 45 min. The results are shown in

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Fig. 4.

2.9. Comparison of the Metal Ion Removal Capacities

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In order to know the metal ion removal efficiency of the three Schiff bases, a comparative study of each Schiff base was made onto the three metal ion solutions separately. In a typical procedure, 10 ml of each synthesized Schiff base (0.2 g) was added to 20 ml of 100 mg/L of each metal ion solution at a fixed pH (5.5). Then, each solution mixture containing the Schiff base and the metal ion was stirred for 1 hour with a stirring speed 150 r.p.m at a constant temperature 500C using a magnetic stirrer. After the prescribed time

period the solutions were centrifuged and the centrifugates were used for the determination of residual metal ion concentration in AAS. The relative recognition power of the Schiff bases for the metal ion was evaluated by using the following equations [17]. Static distribution coefficient

KD = qe/ce

(3)

Selectivity coefficient

α = KD1/KD2

(4)

Relative selectivity coefficient

β = α1/ α2.

(5)

The comparison of the metal ions’ removal by the Schiff bases are represented in Fig. S 4 and

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the selectivity coefficients are given in Table 1. 2.10. Competitive Metal Ion Adsorption by APDA-EA in Binary Mixture

The relative recognition power of APDA-EA towards the metal ions used, binary

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solutions of metal ions namely Th4+/ Cd2+, Th4+/Pb2+ and Pb2+/Cd2+ were used for the adsorption. In a typical process, 5 ml of APDA-EA (0.1 g) was added to a binary solution

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mixture made by 10 ml of 100 mg/L each metal ion solution separately. The solution

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mixtures were stirred separately for 1 hour at pH 5.5 and at temperature 500 C in a magnetic stirrer with a stirring speed 150 rpm. After 1hour time period, the solution mixtures were centrifuged separately and the supernatant from each mixture was used for the study of the

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residual metal ion concentration using AAS.

The separation factor (αXY ) for a single metal ion with respect to other two metal ions system

QX CY

(6)

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αXY =

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was expressed by the following equations [30].

CX QY

Where 4+

αTh Pb2+ = 2+

αCd Th4+ =

QTh4+ CPb2+ CTh4+ QPb2+

QCd2+ CTh4+ CCd2+ QTh4+

[For Th4+ and Pb2+ metal ions]

(7)

[For Cd2+ and Th4+ metal ions]

(8)

2+

αCd Pb2+ =

QCd2+ CPb2+

[For Cd2+ and Pb2+ metal ions]

CCd2+ QPb2+

(9)

If the separation factor αXY is greater than one, the adsorption of X is favoured over Y and when it is less than one the adsorption of Y favoured over X. The values of separation factors are summarized in Table 1. The results are shown in Fig. S 4.

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2.11. Metal Complexation Studies by APDA-EA 2.11.1 Measurement of Conductance

Conductance measurements of the three metal ions’ solution by using APDA-EA

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were carried out in order to study the affinity power of APDA-EA towards all the three metal ions. In a typical experiment, solution of three metal ions namely Th4+, Cd2+ and Pb2+ were

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made by dissolving 1 g of each metal salt in 40 ml distilled water separately. A stock solution of APDA-EA was made by dissolving 3.5 g of APDA-EA in 200 ml of distilled water. Now

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each metal solution was titrated conductometrically by adding APDA-EA solution at a fixed pH 5.5 in a dropwise fashion using conductometer (Systronics, model 304, Ahmedabad,

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India) with a platinum electrode. The results are shown in Fig. 5. 2.11.2. Theoretical study of APDA-EA-Th4+complex through DFT calculation.

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Theoretical study of the APDA-EA-Th4+ complex was performed by using Gaussian

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09 programme package. The complex structures were drawn by using Gauss view 5.0 software. O=HC-CH2-CH2-CH2-CH2-CH=O was taken as model dialdehyde of APDA for electronic structure calculation of APDA, APDA-EA, APDA-HYD and APDA-SEMI. HOCH2-CH2-N=HC-CH2-CH2-CH2-CH2-CH=N-CH2-CH2-OH, CH2-CH=N-NH2

and

H2N-N=HC-CH2-CH2-CH2-

H2N-CO-NH-N=HC-CH2-CH2-CH2-CH2-CH=N-NH-CO-NH2

considered as a model structures of the Schiff bases APDA-EA, APDA-HYD and APDA-

SEMI for free optimization. The model structure of the Schiff base APDA-EA was used for electronic structure calculation of the complex APDA-EA-Th4+. The free optimization of APDA, APDA-EA, APDA-HYD and APDA-SEMI was performed using basis set def2TZVP and B3LYP as functional. Stuattgart RSC 1997 ECP basis set and B3LYP functional were used to optimize the APDA-EA-Th4+ complex. HOMO and LUMO orbital along with their energies of model APDA, APDA-EA, APDA-HYD, APDA-SEMI, APDA-EA-Th4+ respectively is shown in Fig. 6. The probable structure of the APDA-EA-Th4+ complex is

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given in Fig. S 5. The energies of the HOMO and LUMO orbital are given in Table 2. 2.12. Dye Adsorption Studies 2.12.1. Effect of pH

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The pH variation plays an important role to the dye adsorption process onto the adsorbent’s surface. The dye removal capacity of the APDA-EA was investigated over a pH

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range 2 to 8 at a constant temperature 300C for 45 min. The results are shown in Fig. 4.

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2.13. Comparison of the Dye Removal Capacities

Comparison of the dye removal capacities of the three synthesized Schiff bases in the three dye solutions were carried out in the similar way as that of metal ion removal capacities

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as well as in our previous procedure [31] at pH 5.5. Static distribution coefficient (KD), Selectivity coefficient (α) and relative selectivity coefficient (β) of the Schiff bases were

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calculated by using the equations 3, 4 and 5 [17]. The results of the comparative studies are

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shown in Fig. S 4 and the selectivity coefficient values are summarized in Table 1. 2.14. Competitive dye Adsorption Studies by APDA-EA in Binary Solution MG/MB, MG/MV and MB/MV binary dye mixtures were used for the adsorption

with APDA-EA in order to determine the relative recognition power of APDA-EA towards the three dyes. A typical process was as follows; first, the binary dye solutions were prepared by mixing 10 ml of 100 mg/L of each dye solution. Then 5 ml of APDA-EA (0.1 g) solution

was added to each binary dye solution separately. The mixture solutions were stirred in a magnetic stirrer at pH 5.5 with a stirring speed of 200 rpm for 1 hour. After 1 hour 2 ml of each dye solution from the bulk was taken out. After centrifugation the supernatants were subjected to measure the residual dye concentration in a UV-VIS spectrophotometer at different λmax values as stated earlier. The separation factor for a single dye with respect to other two dyes was calculated by using equation 6 [30], where αMG MB =

QMG CMB

αMV MG =

QMV CMG

αMV MB =

QMV CMB

[For MG and MB]

(10)

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CMB QMG

CMG QMV

(11)

[For MV and MB]

(12)

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CMB QMV

[For MV and MG]

The values of separation factors are given in the Table 1 and the results are shown in Fig. S 4.

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2.15. Adsorption Studies of APDA-EA in Mixture of a Dye (MG) and Metal Ion (Th4+)

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Since APDA-EA showed strong adsorption towards both the Th4+ and MG over the other two Schiff bases it was used as an adsorbent in a mixture of Th4+ and MG solution. 2.15.1. Isothermal Sorption Analysis

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Isothermal sorption analysis was performed for single component as well as multicomponent systems (binary system) to evaluate the synchronous adsorption efficiency

qx,z qy,z

(13)

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Rq =

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(Rq) of the adsorbent by using the following equation [32-34].

Where qx,z and qy,z refer to the uptake capacity of adsorbent for the adsorbate ‘z’ in

binary and mono-component systems respectively with same initial concentration (where x and y refer to the binary and mono component systems respectively ). If Rq >1, the uptake capacity of the adsorbent for ‘z’ component is enhanced by the co adsorbate; Rq =1 indicates that the synchronous adsorption capacity for component ‘z’ remains unaffected in presence of

co-adsorbate; Rq <1 refers that the presence of co-adsorbate suppresses the synchronous adsorption capacity for ‘z’ component in binary solution [35]. For single component system 20 mg of APDA-EA and 20 ml of each Th4+ or MG solution with known initial concentration ranging from 20 mg/L to 100 mg/L was stirred for 4 hours at pH 5.5. Binary sorption experiment of Th4+/MG system was carried out by mixing 20 mg of APDA-EA with 20 ml of Th4+/MG binary solution at pH 5.5 under stirring for 4 hours. The initial concentrations of Th4+ and MG were varied 20 mg/L to 100 mg/L for both. After

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adsorption for the both single and multi-component systems the remaining metal ion and dye concentrations were determined by using AAS and UV-VIS spectroscopy respectively.

2.15.2. Desorption and Reusability of APDA-EA for the Adsorption of Th4+ Ion and MG dye

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For simultaneous removal of multiple adsorbents (Th4+ ion and MG dye), 4 mg of APDA-EA was mixed with 20 ml Th4+- MG binary solution having concentration 10 mg/L of

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each adsorbate (Th4+ ion and MG dye). The reaction mixture was stirred for four hours at

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50OC temperature to make the APDA-EA saturated with adsorbents (Th4+ ion and MG dye). Then the mixture solution was treated with HCl solution having pH = 3 for Th4+ ion and ethylene glycol for MG dye as eluants. After that the regenerated adsorbent (APDA-EA) was

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separated from the mixture solution and washed with double distilled water for the successive use as the adsorbent. The supernatant of the reaction mixture was collected to estimate the

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concentration of Th4+ ion and MG dye. This adsorption-desorption procedure was repeated

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for five times.

3. RESULTS AND DISCUSSION 3.1. Synthesis

Oxidation by periodate ion is very specific oxidation to cleave the C-C bond of glycols to form paired carbonyl groups. In the present case, the oxidation of AP by NaIO4 leads to cleavage of C2-C3 bonds specifically in the anhydroglucose units of the AP chain

resulting formation of two aldehyde groups that give Schiff bases upon the reaction with hydroxyl amine, semicarbazide and ethanolamine separately, forming AP-HC=NZ bonds. The synthetic schemes are shown in Fig. 1. 3.2. Characterization 3.2.1. FTIR Spectroscopy The FTIR spectra of APDA, APDA-EA, APDA-HYD and APDA-SEMI are shown in Fig. S 1, from which it is observed that new bands (compared to spectrum of AP) at 1704 cm(The FTIR spectrum of AP was given in our previous communication [36] and 2997 cm-1

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appeared in the APDA which correspond to the aldehyde (-CHO) functional groups and aldehydic protons respectively confirming the cleavage of C2-C3 bond and formation of a pair

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of aldehyde groups [37].

The FTIR spectra of APDA Schiff bases were completely different to that of APDA.

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For APDA-EA band at 1660 cm-1 was for ‘C=N’ groups [38]. and 1345 cm-1 was for ‘C-N’

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groups, for APDA-HYD the band at 1613 cm-1 was for ‘C=N’ group ,1360 cm-1 for C-N groups and 1133 cm-1 was for ‘N-N’ bond whereas the N-H stretching vibration overlapped with -OH stretching vibration at 3400 cm-1. For APDA-SEMI the band near 1683 cm-1

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indicate the stretching vibration of the carbonyl groups (C=O) of amide functionalities. The peak corresponding to ‘C=N’ appeared at 1440 cm-1 and for C-N appeared at 1120 cm-1. The

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‘N-H’ stretching vibrations were overlapped with -OH stretching vibrations at 3200 cm-1.

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3.2.2. 1H NMR Spectroscopy 1

H NMR spectra of all the synthesised compounds are shown in Fig. S 2. In Fig. S

2(a) a new peak (compared to AP, the 1H NMR spectra of AP was given in our previous communication [36]) appeared at δ8.7 mg/L due to aldehyde protons confirming oxidation of AP to APDA. In all the spectrum a large number of peaks appeared at δ4.5-4.7 mg/L which was for DOH. In Fig. S 2(b) which was for APDA-EA, a peak at δ7.2 corresponded to the protons

of -CH=NZ units, that appeared at δ7.3 mg/L for APDA-HYD [Fig. S 2(c)] and at δ7.0 mg/L for APDA-SEMI [Fig. S 2(d)]. Other peaks were less significant that were for saturated ‘CH’ protons present in polysaccharides back bone. Thus, presence a band at δ7.0-7.3 region in the Schiff bases support the formation of -CH=NZ units. 3.2.3. FESEM Studies From the SEM images (Fig. 2) it was observed that the surface of dialdehyde and Schiff bases looked crystalline with drastic change in surface morphologies.

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3.2.4. XRD Studies The XRD patterns showed the high degree of crystallinity for the APDA, APDA-EA, APDA-HYD and APDA-SEMI (Fig. S 3). The degree of crystallinity of APDA was

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maximum that indicated a well packed structure. The crystal packing was disrupted during Schiff base formation with the amines used. The major disruption of crystal structure was

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happened in case of APDA-SEMI (Fig. S 3) resulting in the lower crystallinity.

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3.3. Aldehyde Content

Detection of carbonyl group qualitatively and measurement of aldehyde content in APDA were done by using 2,4-dinitrophenyl hydrazine (DNPH). When DNPH solution was

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added to APDA solution orange yellow precipitation was formed. Using the equation 1 the aldehyde content in APDA was found to be 67 %. Following the same procedure and

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equation the aldehyde content of all Schiff bases was calculated and it was found that the

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aldehyde contents were reduced to 18 % for APDA-EA, 26 % for APDA-HYD and 33 % for APDA-SEMI indicated the -CHO groups of APDA were involved in Schiff’s base formation.

3.4. pHPZC of the APDA-EA

Fig. 3 shows the PZC of the adsorbent APDA-EA. The PZC of the APDA-EA is 4.5. At pH < pHPZC the imine (-CH=N-Z) and -OH functional groups remain in protonated form which results the positive surface of the APDA-EA. Again, pH greater than pHPZC suggests that at higher pH the adsorbent surface becomes negatively charged due to deprotonation of imine (-CH=NH-Z) and -OH functional groups. 3.5. pH Variation Fig. 4 (a) showed that with increase in solution pH, the metal ions removal capacity of

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APDA-EA was increased for all the three-metal ions upto pH 5.5. This observation can be explained by considering the number of active sites present in APDA-EA, which was increased with increasing pH, due to deprotonation of -OH groups. But at pH 5.5 maximum -

-p

OH groups remained deprotonated. Hence highest adsorptions for all three metal ions are occurred at pH 5.5. Further increase of pH does not cause any change of adsorption. More

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over maximum metal ion removal was occurred for Th4+ than the other two metal ions. The

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possible chemical reactions for Th4+ ion with APDA-EA is given bellow. Z-N=CH-(CH2)4-CH=N-Z + Th(NO3)4

[(Z-N=CH-(CH2)4-CH=N-Z)Th]2++4NO3-

3.6. Removal of Metal Ions by the Schiff bases and their Selectivity in Adsorption

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All the three metal ions were adsorbed strongly [Fig. S 4 (a)] by APDA-EA over the other two namely APDA-HYD and APDA-SEMI. The values of KD, α and β (Table-1)

ur

showed the recognition power of APDA-EA towards the Th4+ ion was highest over the other

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two Schiff bases. The increasing order of Th4+ ion removal capacity followed the order APDA-EA> APDA-HYD> APDA-SEMI. The higher selectivity of adsorption of APDA-EA 4+

towards Th4+ was also confirmed from the value αTh Pb2+ >1 [Fig. S 4(c), Table 1]. The 2+

2+

Cd separation factors αCd Th4+ and αPb2+ were less than one indicated that the adsorption tendency

of Pb2+ and Cd2+ was less than that of the Th4+ towards the surface of APDA-EA.The higher affinity of adsorption of APDA-EA towards Th4+ was also supported by conductometric

titration plot (Fig. 5). A gradual decrease of conductance (ms) of all the metal ions solutions occurred with gradual addition of APDA-EA, indicating the adsorption of the metal ions (complexation) with APDA-EA. Fig. 5 also showed that the decrease of conductance of Th4+ was higher than that of the other two metal ions, Pb2+ and Cd2+. Between Pb2+ and Cd2+ ion the conductance value of Pb2+ solution decreased sharply than the Cd2+ ion indicating Pb2+ ion adsorbed more than the Cd2+ ions. Hence the decreasing order of metal ions uptake by APDA-EA followed the order Th4+>Pb2+>Cd2+. Thus, all the experimental results supported

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the stronger affinity of APDA-EA towards Th4+ ions compared to the other two ions Pb2+ and Cd2+. The reason comes from the following way. Among the metal ions used Th4+ was comparatively harder than that of the other two because of the greater positive charge density.

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Between Pb2+ and Cd2+, Pb2+ was harder than Cd2+. The relative hardness order is Th4+>Pb2+>Cd2+. Again, in APDA-EA the metal chelating site was the -OH groups, in

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APDA-HYD the chelating site was -NH2 groups and in APDA-SEMI the chelating site was -

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CO-NH2 groups apart from the ‘N’ centre of -CH=NZ units. The relative hardness of ‘O’ centre was higher than that of the ‘N’ centre hence ‘O’ in APDA-EA preferred to bind Th4+ more preferentially than the other two.

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3.7. Theoretical Study of Th4+ Complexation with Model APDA-EA using DFT Fig. 6 showed the optimization structures, HOMO and LUMO orbital along with their

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energies of model APDA, APDA-EA, APDA-HYD, APDA-SEMI, APDA-EA complexed

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with Th4+ respectively. The characteristic bond lengths of the complex are in Table 2. The characteristic bonds lengths suggested that the interactions between ligand APDA-EA and Th4+ metal ions are mainly ionic in nature. The possible interactions are shown in Fig. S 5 (scheme II). 3.8. Dye Adsorption Studies 3.8.1. pH Variation

The pH variation effect was carried out by varying the solution pH from 2 to 8 of the dyes’ solutions (MG, MB and MV) for adsorption onto the APDA-EA surface. Fig. 4(b) showed that the dye removal capacities of APDA-EA gradually increased with increasing the pH of the solution and reached to a maximum value at pH 5.5. After reaching to the maximum point the dye removal capacity remained unchanged with further increase in pH. The hydroxyl groups of APDA-EA became deprotonated with increasing pH of the solution and at pH 5.5 the most of the hydroxyl groups are remained free to adsorb the cationic dyes

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from their aqueous medium resulting strong the maximum dye adsorption capacity. As the most of the active sites of APDA-EA were involved in the adsorption process, further increase of pH of the solution did not cause any change of dye removal capacities. From the

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Fig. 4(b) also showed that the dye removal capacity of APDA-EA for MG was maximum

bellow.

[(Z-N=CH-(CH2)4-CH=N-Z)MG]

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Z-N=CH-(CH2)4-CH=N-Z + MG

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than the other two dyes. The possible chemical reactions for MG with APDA-EA is given

3.9. Competitive Dye Adsorption

The competitive dye removal capacities of APDA-EA, APDA-HYD and APDA-

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SEMI towards MB, MV and MG are shown Fig. S 4(b), that showed that APDA-EA has strong adsorption capacity than the other two Schiff bases in all the three cases and their

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relative dye adsorption capacities follow the order APDA-EA>APDA-HYD>APDA-SEMI.

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Again, among the three dyes MG was strongly adsorbed by APDA-EA followed by MB and MV, supported by the values of KD, α and β values (Table 1). Among the three dyes MG has MV MV the separation factor αMG MB >1 but the same for the other two αMG and αMB were less than one,

(Fig. S 4(d), Table 1) indicated MG got adsorbed onto the surface of APDA-EA preferentially than the other two. The relative adsorption ability of the three dyes followed the order MG>MB>MV. The reason comes from the following way by considering two

factors one is bulkness another is π-π interaction between the dye and the adsorbent. The bulkness order of the dyes followed the order MB
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Since APDA-EA showed best performance towards adsorption of Th4+ ion and MG dye, further investigation such as effect of solution pH on the adsorption, adsorption kinetics and adsorption isotherms were carried out only for the adsorption of Th4+ and MG by the APDA-

-p

EA separately.

3.10. Adsorption Kinetics of the Th4+ Ion and MG Dye Adsorption onto the APDA-EA Surface

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The pseudo first order, pseudo second order [39] and Banghum [40] kinetic equations

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were used to rationalize the adsorption mechanism of the adsorption phenomenon of the synthesised Schiff base APDA-EA as an adsorbent with the Th4+ metal ion and MG dye. log(qe - qt ) - log qe = -

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Pseudo first order equation Pseudo second order equation

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Banghum kinetic equation

t

qt

=

1



t

t

(14) (15)

k2 q2e qe

lnqt = lnK T +

kt 2.303

1 m

lnt

(16)

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Where qe and qt are the amounts of Th4+ metal ion and MG dye adsorbed at equilibrium and at time ‘t’ (mg / g) respectively. k1 refers to the pseudo first order rate constant (min-1) and k2 refers to the pseudo second order rate constant (g/mg.min). k1 was determined from the linear curve fitting plot of log (qe-qt) versus t. k2 and qe were determined from the intercept and slope of linearized plot of t/ qt versus t. KT is the rate constant of adsorption process for

Banghum equation. The intensity of adsorption process (m) was calculated from the slope of linearized plot of lnqt and lnt. Fig. 7(a), 7(c) and Fig. 7(b), 7(d) represented the curve fitting plots of pseudo-first-order and pseudo-second-order kinetics model of APDA-EA for the adsorption of Th4+ ion and MG dye respectively. The pseudo first order rate constant [k1 (min-1)], pseudo second order rate constant [k2 (g/mg.min)] and the correlation coefficient values (R2) are given in Table 3. The correlation values (R2 ˃ 0.99) corresponding to pseudo second order kinetic model showed

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good liner relationship over the pseudo first order kinetic model of APDA-EA for the adsorption of both the Th4+ metal ion and MG dye. This observation support that the adsorption mechanism of APDA-EA followed pseudo second order kinetic model more

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accurately than first order kinetic model. This kinetic study was also suggested that the adsorption of Th4+ ion and MG dye onto the surface of APDA-EA was a chemisorption

re

process. Fig. 7(e), 7(f) represents the curve fitting plots of Banghum kinetic model for Th4+

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and MG adsorption respectively. The rate constant (KT) and correlation coefficients (R2) are given in Table 4. The values of KT and R2 suggest that the diffusion pathway of the Th4+ metal ion and MG dye molecules onto the surface of Schiff base APDA-EA is due to

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chemisorption process [41].

3.11. Adsorption Isotherms For the study of adsorption property of Th4+ metal ion and MG dye onto the surface of

APDA-EA mainly three adsorption isotherms namely Freundlich isotherm, Langmuir isotherm and Temkin isotherm [41] were used in the present investigation. The Freundlich isotherm is

qe =

x m

1/n

= k. ce

(17)

Where qe referred the equilibrium concentration of Th4+ metal ion and MG dye onto the surface of APDA-EA (mg/g), x referred to the amount of Th4+ metal ion and MG dye adsorbed onto the surface of ‘m’ gram of the synthesised Schiff base APDA-EA at equilibrium. Ce indicates the equilibrium concentration of the Th4+ metal ion and MG dye in aqueous solution (mg/L), k referred to the Freundlich constant (l/g) and 1/n was the heterogenicity factor. The linearized form of the equation is given below, 1

lnqe = ln k + ln ce

(18)

n

curve fitting plot respectively. qe

=

1 KL

+

aL c KL e

Or, qmax =

x m

(19)

=

KL ce

-p

Ce

The Langmuir equation is

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The linearized plot qe versus Ce gave the k and n values from the intercept and slope of the

1+qL ce

(20)

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Where; x referred to the amount of Th4+ metal ion and MG dye adsorbed (mg) onto the APDA-EA surface, m referred to the amount adsorbent (g) used for adsorption. KL (l/g)

Ce

versusCe . Intercept and slope gave the KL and

aL KL

values. The qmax was the maximum

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qe

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and aL (l/mg) were the Langmuir constants, which were obtained from the linearized plot of

Th4+metal ion and MG dye adsorption capacity by the adsorbent APDA-EA. qmax and KL/aL

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have the numerically same value.

The linearized form of Temkin isotherm model is (21)

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qe = B1 lnT + B1 lnCe

Where; B1 (J/mole) and KT (L/mol) referred to the Temkin adsorption isotherm

constant and equilibrium binding constant respectively. The curve fitting plots of the Freundlich adsorption isotherm of APDA-EA for Th4+ metal ion and MG dye are given in Fig. 8(a) and 8(b) respectively.

Fig. 8(c) and 8(d) depicted the linearized plots of Langmuir isotherm of the Schiff base APDA-EA for the adsorption of Th4+ metal ion and MG dye. The correlation coefficients (R2), Freundlich constants [k (l/g)], Langmuir constants [KL (l/g)] and n values are summarised in the Table 4. The R2 value for Langmuir isotherm closed to unity i.e. the adsorption of Th4+ and MG was well fitted with Langmuir isotherm over Freundlich isotherm. The values of n (Table 4) showed greater than unity which showed the adsorption process of the synthesised Schiff base APDA-EA was a chemisorption process . One of the basic

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characteristics [41] of Langmuir adsorption isotherm model is the constant separation factor (RL). Hence R L =

1

(22)

1+aL c0

-p

Where; co (mg/L) indicated the initial Th4+ metal ion and MG dye concentration in solution. The Langmuir adsorption isotherm model was also supported by the RL values of adsorption

re

for Th4+ and MG dye adsorption onto the surface of APDA-EA [RL for Th4+ was 0.002, for

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MG dye was (0.042)]. The monolayer saturation capacity (qmax) values (for Th4+ 94.68 mg/g and for MG dye were 89.84 mg/g) are given in Table 4. The maximum monolayer saturation

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capacities (qmax) for thorium and MG were found to be higher than the reported adsorbents [42-50] which are given in Table 5(a) and Table 5(b).

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Fig. 8(e) and 8(f) showed the curve fitting plots of Temkin isotherm model for the adsorption of Th4+ metal ion and MG dye onto the surface of APDA-EA respectively. Temkin adsorption

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constants and Temkin equilibrium binding constants are summarised in Table 4. The R2 values [Th4+ (0.9755), MG dye (0.9848)] suggested that the Temkin isotherm model was also well fitted with the adsorption mechanism of APDA-EA for MG dye than Th4+ metal ion. 3.12. Adsorption Thermodynamics The following equations [41] were used to estimate the thermodynamical parameters like Gibb’s Free energy change (ΔG0 kJ/mol), change of heat of adsorption (ΔH0, kJmol-1)

and the entropy change (ΔS0, kJ.mol-1) of the adsorption process of APDA-EA with Th4+ metal ion and MG dye. ΔG0 = −RT ln K eq

(23)

ΔG0 = ΔH0 − ΔS0

(24)

ln K eq = (−

ΔH0 1 R

) + T

ΔS0

(25)

R

Where; T, R and Keq indicated to the experimental temperature, universal gas constant (8.314 Cs Ce

) respectively. Cs and the Ce

ro of

Jmol-1K-1) and Keq referred to the equilibrium constant (K eq =

(mg/L) are the equilibrium concentrations of adsorbed Th4+ metal ions and MG dye onto the surface of APDA-EA. ΔH0 and is ΔS0 are calculated form the slope and intercept of the plot 1

1

T

T

-p

of ln Keq vs respectively. The plots of ln Keq vs of the adsorption processes for Th4+ and

re

MG onto the surface of APDA-EA are shown in Fig. 9. The values of ΔG0, ΔH0 and ΔS0 are summarised in Table 6. The ΔG0 values for the both adsorption process for Th4+ and MG onto

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the surface of APDA-EA are negative. The negative values of Gibb’s free energy (ΔG0) referred to the spontaneous nature of adsorption process for both cases. The both adsorption

na

process for Th4+ and MG onto the surface of APDA-EA have negative enthalpy i.e. enthalpically (ΔH0) favourable. As the values of ΔS0 were negative, both adsorption process

ur

for Th4+ metal ion and MG dye onto the surface of Schiff base (APDA-EA) were entropically

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unfavourable also.

3.13. Adsorption Studies of APDA-EA in Mixture of a Dye (MG) and Metal Ion (Th4+) Since both the Th4+ ions and MG dye adsorbed strongly by APDA-EA over the other

two Schiff bases, it was used as a potent adsorbent in a mixture of Th4+ and MG solution. 3.13.1. Synchronous Adsorption in Metal-Dye Multi Components System

The effect of initial concentration (dye or metal ion) on the adsorption of metal ion or dye onto the surface of APDA-EA were studied in binary systems. Fig. S 6(a) showed the effect of initial MG dye concentration on Th4+ ion adsorption in Th4+/MG binary solution and the effect of initial Th4+ ion concentration on MG dye adsorption onto the surface of APDAEA in Th4+-MG binary solution is shown in Fig. S 6(b). Fig. S 6(b) clearly showed that the sorption capacity of Th4+ ion was decreased with increasing MG dye concentration with Rq values less than 1. This decrement may be due to increase in positively charged MG dye

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molecules. Furthermore, the π-π interactions between APDA-EA and MG predominates over ionic interaction between APDA-EA and Th4+ ion. Fig. S 6(b) showed that the MG dye adsorption onto the APDA-EA was barely impacted by the co-adsorbent Th4+ ion in Th4+-MG

-p

binary solution having Rq value closer to unity. The Rq value suggested that the MG dye adsorption onto the APDA-EA surface discards competitive sorption between two positively

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charged adsorbents (Th4+ ion and MG dye), which revealed that the adsorption of MG dye

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was more favourable in binary solution. This was due to greater π-π interaction between APDA-EA and MG dye which favoured the leading approach of MG dye onto the surface of APDA-EA than the Th4+ ions.

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3.13.2. Desorption and Reusability

Desorption and reuse were very important for the adsorption strategy for practical

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purpose. Desorption experiment was carried out using HCl solution for Th4+ ions and

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ethylene glycol for MG dye as eluants. Fig. S 7 showed the desorption cycles of APDA-EA for Th4+ ions and MG dye respectively. Cycle ‘0’ referred the adsorption of APDA-EA in absence of eluants. Fig. S 7 showed that the removal capacities for both Th4+ ion and MG dye were decreased with increase in regeneration cycles and also showed that after first cycle the removal capacities of APDA-EA were 70 % and 74.35 % for Th4+ ion and MG dye respectively. But after fifth cycle the uptake capacities of the APDA-EA were 30.58 % and

42.30 % for Th4+ ion and MG dye respectively. These results reflected the potentiality of APDA-EA for reusability. 4. Conclusion Amylopectin-primary amine-Schiff bases were prepared successfully by first selective oxidation of amylopectin by sodium metaperiodate in aqueous medium followed by Schiff base formation with ethanol amine, hydrazine and semicarbazide. The well characterized three Schiff bases were used to remove three toxic metal ions namely Th4+, Pb2+ and Cd2+ and

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three commercially available cationic dyes namely MG, MB, MV from their aqueous solutions. Among the three Schiff bases APDA-EA was more efficient for both metal ion and dye removal. Th4+ and MG were selectively adsorbed more by APDA-EA than the other two.

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The adsorption of Th4+ and MG by APDA-EA followed pseudo-second-order kinetic rate equation and Langmuir adsorption isotherm with qmax 94.68 mg/g for Th4+ and for MG it was

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dye enriched waste water or effluents.

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89.84 mg/g. The developed adsorbent can be used to treat the radiotoxic Th4+ and toxic MG

Conflicts of interest

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Authors are declared that they have no conflict of interest.

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Dinabandhu Sasmal: Conceptualization, Methodology, Software, Writing- Original draft preparation. Shankha Banerjee.: Data acuration, Investigation. Sanjib Senapati: Visualization, Investigation. TridibTripathy: Supervision, Conceptualization, Methodology, Reviewing and Editing.

Declaration of interests

The

West

Bengal

Department

of

Biotechnology

[contact

grant

number

60(Sanc.)/BT/P/Budget/RD-63/2017] is earnestly acknowledged, for carrying out the present research work.

Acknowledgements The

West

Bengal

Department

of

Biotechnology

[contact

grant

number

60(Sanc.)/BT/P/Budget/RD-63/2017] is earnestly acknowledged, for carrying out the present research work.

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[38] N. Srisawang, S. Nobsathian, S. Wirasate, C. Chitichotpanya, pH-induced Crosslinking

na

of Rice Starch via Schiff Base Formation. Macromol. Res. 27 (2019) 1193-1199. [39] C. Jiang, X. Wang, G. Wang, C. Hao, X. Li, T. Li, Adsorption performance of a

ur

polysaccharide composite hydrogel based on crosslinked glucan/chitosan for heavy metal

Jo

ions, Compos. Part. B-Eng. 169 (2019) 45-54. [40] R. Bhattacharyya, S. K. Ray, Kinetic and equilibrium modeling for adsorption of textile dyes

in

aqueous

solutions

cellulose/poly(acrylamide‐ co‐ hydroxyethyl

by

methacrylate)

network hydrogel, Polym. Eng. Sci. 53 (2013) 2439-2453.

carboxymethyl semi‐ interpenetrating

[41] D. Gautam, S Kumari, B. Ram, G. S. Chauhan, K. Chauhan, A new hemicellulose-based adsorbent for malachite green, Journal of environmental chemical engineering, 6 (2018) 3889-3897. [42] D.L. Guerra, R.R. Viana, C. Airoldi, Adsorption of thorium cation on modified clays MTTZ derivative, J. Hazard. Mater. 168(2009) 1504–1511. [43] C. Kütahyal, M. Eral, Sorption studies of uranium and thorium on activated carbon prepared from olive stones: kinetic and thermodynamic aspects, J. Nucl. Mater. 396

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(2010) 251–256. [44] V. Luca, J.V. Hanna, A versatile Zr(IV)-organophosphonate coordination polymer platform for the selective adsorption of lanthanides and actinides, Hydrometallurgy 154

-p

(2015) 118–128

[45] L. Dolatyari, M. R. Yaftian, S. Rostamnia, Adsorption characteristics of Eu (III) and Th

re

(IV) ions onto modified mesoporous silica SBA-15 materials. J. Taiwan Inst. Chem. Eng.

lP

60 (2016) 174-184.

[46] F. Khalili, G. Al-Banna, Adsorption of uranium (VI) and thorium (IV) by insolubilized humic acid from Ajloun soil-Jordan, J. Environ. Radioact. 146(2015) 16–26.

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[47] S. Banerjee, G. C. Sharma, R. K. Gautam, M. C. Chattopadhyaya, S. N. Upadhyay, Y. C. Sharma, Removal of Malachite Green, a hazardous dye from aqueous solutions using

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Avena sativa (oat) hull as a potential adsorbent. J. mol. Liq. 213 (2016) 162-172.

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[48] H. Shayesteh, A. Rahbar-Kelishami, R. Norouzbeigi, Adsorption of malachite green and crystal violet cationic dyes from aqueous solution using pumice stone as a low-cost adsorbent: kinetic, equilibrium, and thermodynamic studies, Desalination and Water Treatment, 57(2016) 12822-12831.

[49] A. K. Kushwaha, N. Gupta, M. C. Chattopadhyaya, Removal of cationic methylene blue and malachite green dyes from aqueous solution by waste materials of Daucus carota, Journal of Saudi Chemical Society, 18 (2014), 200-207. [50] R. K. Gautam, V. Rawat, S. Banerjee, M. A. Sanroman, S. Soni, S. K. Singh, M. C. Chattopadhyaya, Synthesis of bimetallic Fe–Zn nanoparticles and its application towards adsorptive removal of carcinogenic dye malachite green and Congo red in water, Journal

Jo

ur

na

lP

re

-p

ro of

of Molecular Liquids, 212(2015), 227-236.

Caption to the Figures HO

HO O

O

IO4-

O HO

O

Oxidation OH O

O

Amylopectin backbone

O

Oxidised amylopectin HO

HO

O H2N

O

Z

O

H+ (dry), Reflux

Z

ro of

O

O

O

N

O O

N

Z

Oxidised amylopectin

O

Amylopectin based shiffbase

lP

re

Fig. 1

-p

Z = -CH2CH2OH (Ethanol amine), -NH2 (Hydrazine), -NHCONH2 (Semicarbazide)

Fig. 1: Schematic diagram of the oxidation of amylopectin by sodium metaperiodate and

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formation of Schiff bases.

Fig. 2: FESEM images of (a) APDA (b) APDA-EA (c) APDA-HYD and (d) APDA-SEMI.

2.0 1.5 1.0

pHf-pHi

0.5 0.0 -0.5

-1.5 -2.0 1

2

3

4

5

6

7

8

9

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ur

na

lP

re

Fig. 3: Point of zero charge plots of APDA-EA.

10

-p

pHi

ro of

-1.0

80

Metal ion removal capcity (mg/g)

72

(a)

Th

(b)

4+ 2+

Cd 2+ Pb

64 56 48 40 32 24 16 3

4

5

6

7

8

ro of

2

re

Fig. 4

-p

pH

Fig. 4: (a) Effect of solution pH of the adsorption of metal ions (Th4+, Cd2+ and Pb2+) by

lP

APDA-EA and (b) effect of solution pH of the adsorption of dyes (MG, MB and MV) by

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na

APDA-EA.

14 Th(IV) Cd(II) Pb(II)

12

Conductance (mS)

10 8 6

2 0

2

4

6

8

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Fig. 5

10

-p

Volume of APDA-EA (mL)

ro of

4

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Fig. 5: Conductometric titration plots of metal ions by the Schiff base APDA-EA.

Fig. 6: Optimized geometry, HOMO and LUMO picture along with their related energies obtained theoretically by DFT calculation using Gaussian 09 and Gauss View 5.0 programme of (a) APDA, (b) APDA-EA, (c) APDA-HYD, (d) APDA-SEMI (e) APDA-EA-Th4+ complex.

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Fig. 7: (a) Pseudo-first-order plot of Th4+ metal ion (b) Pseudo-first-order plot of MG dye (c) Pseudo-second-order plots of Th4+ metal ions (d) Pseudo-second-order plots of MG (e)

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by APDA-EA at different initial dye concentrations.

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Banghum kinetic plot of Th4+ metal ions and (f) Banghum kinetic plot of MG dye adsorptions

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Fig. 8: Adsorption isotherms for the adsorption of Th4+ metal ion adsorption onto the surface of APDA-EA at 500C (a) Freundlich isotherm (c) Langmuir isotherm (e) Temkin isotherm.

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Adsorption isotherms for the adsorption of MG dye onto the surface of APDA-EA at 500C (b) Freundlich isotherm (d) Langmuir isotherm (f) Temkin isotherm.

4+ APDA-EA-Th APDA-EA-MG

2.15 2.10 2.05 2.00

lnKeq

1.95 1.90 1.85 1.80 1.75

1.65 1.60

ro of

1.70

0.00312 0.00318 0.00324 0.00330 0.00336 0.00342 0.00348

re

-p

-1 1/T (K )

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Fig. 9

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Fig. 9: Plots of ln Kc vs 1/T (min-1) for the adsorption of Th4+ metal ion and MG dye onto the

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surface of APDA-EA.

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Caption to the Tables

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Table 1: Selectivity coefficients of APDA-EA, APDA-HYD and APDA-SEMI for the adsorption of metal ions [Th4+, Pb2+ and Cd2+] and dyes

Dye

APDA-EA

APDA-HYD

α

β1

Th4+

32.4

...

...

Pb2+

8.4

3.85

Cd2+

6.2

5.22

MG

28.3

...

KD

α

KD

α

...

12.3

...

8.4

...

2

2.81

6.4

1.92

6.1

1.37

1.91

2.29

4.5

2.73

3.7

2.27

...

...

11.3

...

...

...

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MV

APDA-SEMI

β2

na l

KD

MB

Pr

e-

[MG, MB and MV] adsorption process along with the separation factors of APDA-EA for Th4+ metal ion and MG dye.

10.4

2.72

2.22

2.24

9.2

1.22

8.4

1.21

9.2

3.07

2.29

1.75

8.4

1.34

5.8

1.75

4+

2+

2+

αTh Pb2+

αCd Th4+

αCd Pb2+

αMG MB

αMV MG

αMV MB

3.2

0.81

0.98

2.7

0.77

0.83

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Table 2: HOMO & LUMO energies of APDA, APDA-EA, APDA-HYD, APDA-SEMI and APDA-EA-Th4+ complex along with characteristic

Pr

Bond lengths (Å) 2.2332 2.7330 2.2033

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APDA-EA-Th4+ complex N(18)-Th(20) N(08)-Th(20) O(07)-Th(20) O(17)-Th(20)

Energies of HOMO (eV) - 11.34 -10.44 -09.32 -09.78 -03.44

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APDA APDA-EA APDA-HYD APDA-SEMI APDA-EA-Th4+ complex

e-

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bond lengths of the complexes obtained theoretically by DFT calculation using Gaussian 09 and Gauss View 5.0 programme.

Energies of HOMO (eV) 3.87 4.48 4.84 4.21 -2.22

Banghum model

K1 (Min-1)

R2

K2 (g/mg.min)

R2

KT

100

0.8300

4.6×10-2

0.9999

1.71×10-2

0.9357

24.22

75

0.4454

2.6×10-2

0.9987

1.58×10-2

...

...

50

0.2217

1.4×10-2

0.9986

8.2×10-2

...

...

25

0.5876

1.2×10-2

0.9989

11.2×10-2

...

...

100

0.7275

1.31×10-2

0.9993

2.78×10-2

0.9688

15.74

75

0.5864

2.33×10-2

0.9996

1.61×10-2

...

...

50

0.5024

1.89×10-2

0.9988

2.20×10-2

...

...

25

0.7822

2.83×10-2

0.9991

6.7×10-2

...

...

Pr

R2

na l

MG

Pseudo-second-order

(mg/L)

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Th4+

Pseudo-first-order

e-

Adsorbate

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f

Table 3: Pseudo-first-order, Pseudo-second-order and Banghum constants for the adsorption of metal ions and dyes for APDA-EA.

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Langmuir isotherm

e-

Adsorbate

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Table 4: Freundlich isotherm, Langmuir isotherm and Temkin isotherm constants for Th4+ and MG adsorption by APDA-EA.

Freundlich isotherm

Temkin isotherm

KL(l/mg)

RL

aL

R2

K

n

R2

B1 (J/mol)

KT(L/gm)

R2

Th4+

94.68

558.6

0.002

5.921

0.9997

31.3

4.11

0.9724

26.22

5.92

0.9755

MG

89.84

20.39

0.042

0.226

0.9933

26.4

3.63

0.9742

-25.01

0.37

0.9848

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Pr

Qm(mg/g)

oo

f

Table 4: (a) Comparison of the adsorption capacities of Th4+ ions on different sorbents. (b) Comparison of the adsorption capacities of MG on

pr

different sorbents.

e-

(a) Different adsorbents

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(b)

Pr

Modified clays Activated carbon Organophosphonate polymer Modified mesoporous silica Humic acid APDA-EA

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Different adsorbents Avena sativa (oat) hull Pumice stone Daucus carota - stem Daucus carota - leaf Bimetallic Fe-Zn nanoparticle APDA-EA

qm (mg/g) 30 21 28 81 05 95

Reference [42] [43] [44] [45] [46] This work

qm (mg/g) 83.0 22.6 43.4 52.6 21.7 89.9

Reference [47] [48] [49] [49] [50] This work

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ΔGO(kJ/mol)

Th4+

0.8087

-4.9

MG

0.9342

-5.0

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ΔHO(kJ/mol)

Pr

R2

e-

pr

Table 6: Thermodynamic parameters for the adsorption of Th4+ and MG onto the APDA-EA.

ΔSO(kJ/mol)

-6.5

-4.7×10-3

-4.9

-2.0×10-3