Amido-amine derivative of alginic acid (AmAA) for enhanced adsorption of Pb(II) from aqueous solution

Journal Pre-proof Amido-amine derivative of alginic acid (AmAA) for enhanced adsorption of Pb(II) from aqueous solution

Upma Vaid, Sunil Mittal, J. Nagendra Babu, Ravishankar Kumar PII:

S0141-8130(19)37037-0

DOI:

https://doi.org/10.1016/j.ijbiomac.2020.01.040

Reference:

BIOMAC 14344

To appear in:

International Journal of Biological Macromolecules

Received date:

2 September 2019

Revised date:

12 December 2019

Accepted date:

5 January 2020

Please cite this article as: U. Vaid, S. Mittal, J.N. Babu, et al., Amido-amine derivative of alginic acid (AmAA) for enhanced adsorption of Pb(II) from aqueous solution, International Journal of Biological Macromolecules(2020), https://doi.org/10.1016/ j.ijbiomac.2020.01.040

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

© 2020 Published by Elsevier.

Journal Pre-proof Amido-amine Derivative of Alginic Acid (AmAA) for Enhanced Adsorption of Pb(II) from Aqueous Solution 1,3

1

2

Upma Vaid , Sunil Mittal *, J. Nagendra Babu , Ravishankar Kumar

Authors

1

1,3

:

Upma Vaid , E-mail: [email protected] Phone: +919023062696 1

Sunil Mittal *, Associate Professor – Corresponding Author E-mail: [email protected] Phone: +919815620186 2

J. Nagendra Babu , Assistant Professor

of

E-mail: [email protected] Phone: +919915598259 1

Phone: +919988676790 1

:

Department of Environmental Science and Technology,

re

Affiliations

-p

E-mail: [email protected]

ro

Ravishankar Kumar

School of Environment and Earth Sciences, 2

lP

Central University of Punjab, Bathinda, Punjab, India (151001). Department of Chemistry,

na

School of Basic & Applied Sciences,

Jo ur

Central University of Punjab, Bathinda, Punjab, India (151001).

3

Current Affiliation: Assistant Professor, Chandigarh University, Mohali, Punjab, India (140413)

1

Journal Pre-proof ABSTRACT The present work reports the alternate synthesis of amido-amine derivative of alginic acid (AmAA) with high degree of functionalization. The AmAA have been characterized for percentage functionalization, functional group change, surface morphology and thermal decomposition behavior. The results indicate that the amido-amine derivatisation of alginic acid (AA) with >95% functionalization, significantly improves its Pb(II) adsorption efficiency (395.72 mg/g to 535.87 mg/g) over the AA. The equilibrium and kinetic studies showed that Langmuir and Freundlich adsorption isotherm models fitted well to the experimental data, and these followed pseudo-second order kinetic 13

C CP-MAS

NMR (Cross-

of

model. The FTIR (Fourier transform infrared spectroscopy) and

ro

polarization magic angle spinning carbon-13 solid state nuclear magnetic resonance spectroscopy) analysis revealed that Pb(II) binds to the carboxyl group in case of AA and to the carbonyl & amine

-p

group in case of AmAA, which leads to increase in its adsorption efficiency. The study concludes that

re

the functionalization of amido-amine on AA improves its adsorptive efficiency for Pb(II) from aqueous

lP

medium.

Key Words: Alginic acid; Amido amine derivative of alginic acid; Nitrogen functionalization; Lead

Jo ur

na

adsorption; Ion exchange; Chelation

2

Journal Pre-proof 1. Introduction The discharge of As, Hg, Cd, Cr, Pb, U, etc. through untreated industrial effluents into the water bodies create serious environmental concerns [1-4]. Most of these elements are toxic in nature and can cause severe health effects, when consumed above maximum contaminant concentration level as defined by different agencies like European Union Directive, World Health Organization, US Environmental Protection agency, etc. [5,6]. Lead (Pb) is one of the most toxic contaminant of water bodies. The origin is both geogenic as well as anthropogenic. The prime industrial sources of Pb(II) discharge into water are the process industries like printing, pigments, photographic materials,

of

battery, fuel and explosive manufacturing, etc. [7,8]. The Pb was earlier used in petroleum products

ro

as anti-knocking agent in many parts of the world. The Pb in aerosols settles down to soil particles and ultimately leach down to groundwater. It has been accredited as one of the most hazardous and

-p

non-biodegradable heavy metal by the United States Environmental Protection Agency (USEPA) and

re

United States Agency for Toxic Substances and Disease Registry (USATSDR) [9,10]. It is a cumulative poison, and its intake above the permissible limits produces toxicological, carcinogenic

lP

and neurological effects like high blood pressure, muscle and joint pain, fertility problem in both men and women, damage of kidney and nervous system, cancer, etc. [11-14]. Apart from humans, it is

na

also reported to affect animals and plants adversely [15,16]. Hence, it is necessary to remove the Pb(II) from the water before its use for living beings. The various physico-chemical processes like ion-

Jo ur

exchange, flocculation, coagulation, chemical oxidation, chemical precipitation, membrane filtration, and reverse osmosis are being used for the removal of Pb(II) and other toxic heavy metals from water [17,18]. However, these processes are expensive due to high operational and maintenance costs. In comparison to these, adsorption is an efficient and low-cost process due to its ease of operation and maintenance [17,19,20]. In the past few years, attempts have been made to develop economical and efficient adsorbents for the removal of Pb(II) from aqueous solution by using various low-cost bio-waste and other waste materials [7,12,18,21-30]. However, from the various studies it has been analyzed that to qualify as an ideal adsorbent for sorptive removal of heavy metal ions, adsorbent should not only have large surface area, high adsorptive efficiency, suitable pore size, mechanical stability and high selectively, but also should be available in abundance, cost effective and environmental friendly [31].

3

Journal Pre-proof Attempts to develop an ideal adsorbent have led to exploration of derivatives of bio-macromolecules such as alginate, [19,32-41], chitin [42,43], chitosan [20,26,31,39,44], cellulose [39,45,46] etc. Among these, alginate is second most abundant biopolymer in nature and can be easily extracted from the intracellular matrix of brown algal species [47]. Alginates have the high complexing ability with various heavy metals due to the presence of free hydroxyl (-OH) and carboxyl (-COOH) groups which act as coordination and reaction sites [37,48-51]. The other asset of using AA is that it can be functionalized on the carboxylic arm of the polymer with nitrogen and sulphur groups [50]. These functionalized polymers have been reported to exhibit excellent affinity, high selectivity, and high reactivity towards

of

heavy metal ions [19,52]. This may be due to the improvement of the original surface properties of the

ro

polymer due to chemical modification [53]. Recent studies of Fernando et al. [54], has shown an increase in Pb(II) chelation ability on partial oxidation and carboxylation of AA. Similarly, the grafting

re

the biopolymer for Cd(II), Cu(II) and Pb(II) [52].

-p

of urea and biuret on alginate backbone has also been reported to increase the sorption efficiency of

To the best of our knowledge, there are only limited studies available on functionalized AA derivative

lP

synthesis and its application in metal adsorption. Hence, the current research work, reports the alternate process for synthesis of amido-amine derivative of AA (AmAA) with high degree of

na

functionalization, its characterization and comparative Pb(II) adsorption behaviour. Earlier, the amidated derivative of alginic acid in particular, AmAA has been synthesized by Taubner et al. [55],

Jo ur

using a two-step process involving initial methyl esterification followed by amination with 1,2ethylenediamine. The two step process yielded 73.24% degree of amidation of alginic acid. However, the present work is single step process with a high degree of amidation (>95%). The synthesized derivatives AmAA have been characterized for percentage functionalization, functional group change, surface morphology and thermal decomposition behaviour. The AA and AmAA have been further studied for their adsorptive removal of Pb(II) from aqueous solution, and a comparison between the two have been made. In the last, a discussion has been made about the mechanism involved in the process. 2. Materials and methods All the chemicals used in experimental work were of analytical grade. The stock solution of Pb(II) was prepared by dissolving Pb(NO3)2 in distilled water. Further, the solutions of desired concentration were

4

Journal Pre-proof obtained by diluting the stock solution with distilled water. The pH of the solutions was adjusted using 0.5 M H2SO4 or 1 M NaOH using pH meter. 2.1. Synthesis of AmAA AA was prepared by acidifying sodium alginate using the method of Halim, and Deyab [49] with certain modifications, and the carboxyl content was determined [37]. To AA (2.2 g) in the round bottom flask was added ethylenediamine (6.0 g) and N-N'-dicyclohexyl carbodiimide (DCC) as coupling reagent (2.8 g) in 10 mL dimethylformamide (dried) as a medium for the reaction. During this reaction, by-products may be formed due to the cross-linking process or

of

cyclization reaction. To prevent by-product formation, 1.6 g of N-hydroxysuccinimide (NHS) was

ro

added to the reaction mixture, which protonates the DCC in the intermediate stage [56]. The reaction mixture was kept under continuous stirring for 24 hrs at room temperature. The reaction was

-p

terminated by adding an excess of chloroform. The product (AmAA) was filtered, washed thoroughly

re

with chloroform, and left for air drying. Finally, the AmAA was washed twice with ethanol to remove reagents/their end-products and again air-dried overnight. The degree of amine substitution on AA

lP

was determined by acid-base back titration method given by Abulateefeh et al. [57].

na

2.2. Characterization of AA and AmAA

The elemental analysis (CHNO) of AA and AmAA was done using elemental analyzer (Flash 2000

Jo ur

Thermo Elemental Analyzer) to determine the percentage of C, H, N and O. Morphology and elemental composition of AA and AmAA was determined by Field Emission Scanning Electron n

Microscope (ZEISS Merlin Compact) and Energy Dispersive X-ray Analyzer (Oxford X MAX ). Further, the FTIR spectra of AA and AmAA [before and after Pb(II) adsorption] were recorded in the -1

range 4000-600 cm using Fourier transform infrared spectrometer (BRUKER TENSOR 27) to study the changes during derivatization and to reveal the important functional groups responsible for the binding of metal ions. The

13

C CP MAS SS−NMR (Cross-polarization magic angle spinning carbon-13

solid state nuclear magnetic resonance spectroscopy) analysis was carried using Bruker, Avance II (500MHz). Thermo-gravimetric analysis (TGA) and Differential thermal analysis (DTA) of AmAA and its Pb(II) adsorbed counterpart was performed in a temperature range of 30-500ºC in an alumina pan at heating rates of 10°C/min under nitrogen atmosphere (flowing at 40 mL/min) using Shimadzu DTG60H thermo-gravimetric analyzer.

5

Journal Pre-proof 2.3. Evaluation of Pb(II) Adsorption potential of AA and AmAA The batch adsorption experiments were performed to study the effect of various parameters such as pH, adsorbent doses, contact time, and initial ion concentration on Pb(II) adsorption efficiency of AA and AmAA. The pH was optimized by shaking 100 mL of 500 mg/L Pb(II) solution maintained at pH o

varying from 2.0-5.0 with 0.5 g/L AA or AmAA for 2 hrs at 25+1 C on 200 rpm. After equilibrium period (2 hrs), the solution was filtered (Whatman No. 1 filter paper) and the aqueous phase concentration of metal ion was determined using stripping voltameter (Metrohm, 797 VA COMPUTRACE). The effect of variation in adsorbent dose on metal ion adsorption was studied by shaking varying adsorbent dose

of

(0.25, 0.5, 1.0, 2.0 g/L) with 100 mL of 500 mg/L Pb(II) solution having pH 5. Effect of contact time

ro

and adsorption kinetics of Pb(II) adsorption by AA and AmAA was studied by shaking 0.25 g/L of adsorbent with 100 mL of 500 mg/L Pb(II) solution maintained at pH 5 for different time intervals (2.5,

-p

5, 10, 15, 30, 60 and 120 minutes) at 200 rpm. Further, increase in time interval after 120 minutes did

re

not showed any significant increase in adsorption efficiency. Finally, the effect of initial metal ion concentration was studied by shaking 0.25 g/L of the adsorbent separately with 100 mL of Pb(II)

lP

solution of varying concentrations (100-800 mg/L) at pH 5.0 for 30 minutes. The percent Pb(II) removal (R%) was calculated by fitting the data collected from the above experiments in Eq. (1): ………………………… Eq. (1)

na

R%= [(C0-Ce)/C0]*100

Where, Co is the initial concentration of Pb(II) ions (mg/L) and Ce is the equilibrium concentration of

Jo ur

Pb(II) ion upon adsorption, mg/L

The Pb(II) adsorption capacity (qe) of AA and AmAA was determined by applying mass balance equation (Eq. 2).

qe= [(C0-Ce)/S]V

…………………………Eq. (2)

where, qe is the Pb(II) uptake by adsorbent after the equilibrium (mg/g); S is the mass of solid adsorbent (g) and V is the volume of liquid treated (L). Further, Langmuir and Freundlich sorption isotherm models were applied to the data obtained from the experiment to study the effect of initial ion concentration on Pb(II) adsorption efficiency. 3. Results and discussion 3.1 Synthesis and Characterization of AA and AmAA: The carboxyl content of synthesized AA was −

approximately 495.5 meq COOH per 100 g of sample as determined by acid base titrimetry, which indicates that almost 85+3% of sodium ions in sodium alginate were replaced with protons during

6

Journal Pre-proof conversion to AA. Similarly, the CHN analysis reveals best fit at 80% sodium ion removal (Table 1). The coupling reaction of AA with 1,2-ethylenediamine using DCC/NHS as coupling reagent in DMF, furnished the compound AmAA. Schematic representation for the synthesis of AmAA conjugate is given in Scheme 1. The AA and AmAA were characterized using elemental analyzer (C, H and N), FTIR,

13

C CP-MAS

NMR analysis. The Results of elemental analysis of AA and AmAA are presented in Table 1. The percent elemental composition of AA is almost similar to that of the result obtained by Rani et al. [51]. The nitrogen in case of AmAA was observed to be 11.49% which confirms the coupling of an amine

of

with AA. The result of CHN analysis reveals a 95% AmAA formation and 5% exist as the AA form.

ro

Based on the results of elemental analysis, the empirical formulae of AA and AmAA were derived as C6H7.8O6Na0.2.1.1H2O and C7.9H13.7N1.9O5.05.0.75H2O, respectively. The elemental analysis of AA and

-p

AmAA has indicated a good correlation between the experimental and calculated values. AmAA

re

showed 95% degree of amination in comparison with upto 73.24% (mol%) degree of amination obtained from a methylation followed by amination of methyl ester derivative of alginic acid [55].

and carboxylate ion at 1642.96 cm

−1

lP

The FTIR spectrum of AA showed characteristic absorption bands of carboxylic acid at 1747.13 cm

−1

−1

and 1419.98 cm [Fig. 1]. The FTIR spectra of AmAA showed a

-1

na

significant change in comparison to the spectra of AA. Two peaks were observed at 3544.64 cm

-1

-1

(broad) and 3325.30 cm (sharp) in case of AmAA. The sharp peak at 3325.30 cm corresponds to -

Jo ur

OH moiety of AA, however, the broad absorption band at 3544.64 cm

-1

indicates the presence of

amine and amide functional groups. Amide was confirmed by the disappearance of the absorption -1

-1

-1

peaks due to carboxylic acid (1747.13 cm ) and/or carboxylate ion (1642.96 cm and 1419.98 cm ) -1

-1

and the appearance of peaks at 1630.62 cm and 1573.53 cm accounted to –NH bending of amine and carboxyl of amide, respectively. Further, absorption peaks were observed at 1433.99 cm corresponding to –NH deformation, and at 1309.74 cm

-1

& 891.47 cm

-1

-1

corresponding to C-N

stretching. Thermo-gravimetric (TG) analysis of AA and AmAA was carried out to understand the thermal degradation behavior of the two polymers [Fig. 2(a)]. TG curves of AA have two distinct stages of thermal degradation in the range of 40-90°C, and 185-280°C. Thermal degradation of 8.2% and 7.8%, respectively between 40-90°C in case of AA [37] and AmAA is attributed to dehydration of polymers. Further, decomposition of AA and AmAA showed a weight loss of upto 37.42% and 35.03%

7

Journal Pre-proof respectively, in the temperature range 185-280°C, which is accounted to the decomposition of polymer [37]. Finally, upto 500°C, a total loss of almost 71.98% and 72.45% was observed respectively, for AA and AmAA. Thus, both the polymers AA and AmAA had little difference in their thermal degradation behavior, hence, indicating decarboxylation and charing as the major mechanism of decomposition of both the polymers. The DTA of AA was characterized by a heat loss during dehydration and heat gain during the pyrolysis/decomposition of AA with maxima at 60°C and 260°C, °

respectively [Fig. 2(b)]. Similar maxima were observed at 70°C and 250 C in case of AmAA, with the thermal decomposition of AmAA being sharper in comparison to that of AA. This could be accounted

13

C CP-MAS SS-NMR spectra of AA and AmAA were studied as given in Fig. 3(a) and 3(b),

respectively. The

13

ro

The

of

to the change in the functional moiety of AmAA as compared to AA.

C CP-MAS SS-NMR spectrum of AA showed the presence of peaks in the range δ

-p

64-85, 102-105 and 165-185 ppm [Fig. 3(a)] and can be characterized for the presence of two

re

monomeric units i.e. (1,4)-linked β-D-mannuronic acid (M) and α-L-guluronic acid (G). Alteration of these two monomeric units results in the combinations GG, MG and MM with slight variation in the

lP

environment of the polymer leading to the broadening of peaks [58]. Further, analysis of the broad peaks was carried out by deconvolution of the whole spectra using the Mesterec 8.0 software. Upon 13

C MAS spectra using Global Spectral Deconvolution (GSD), the spectral peaks

na

deconvolution of the

Jo ur

in the region δ 64-85 ppm were characterized by six deconvoluted peaks at δ 64.77, 67.06, 70.90, 73.00, 81.19 and 83.83 ppm.

The peaks at δ 64.77, 67.06 and 81.19 ppm corresponds to the C-2, C-3/C-5 and C-4 G functional moieties of α-L-guluronic acid monomer block [58]. These peaks shifted upfield in comparison to the β-D-mannuronic acid functional moieties which showed a corresponding peak at δ 70.90, 73.00 and 83.83 ppm for C-2/C-3, C-5 and C-4 [58]. Similarly, the C-1 of the α-L-guluronic acid and β-Dmannuronic acid were observed at δ 102.25 and 104.04 ppm, respectively. Further, the M/G ratio (1.366) in AA was determined by comparing the total area of α-L-guluronic acid with that of β-Dmannuronic acid in the range δ 64-85 ppm. Fig. 3(b) presents the

13

C CP-MAS spectrum of AmAA which shows the characteristic peaks in the

range δ 26.3 - 41.73 ppm which corresponds to the ethylene moieties of the condensed diamine. The G and M block C2-5 were observed in the range of δ 68 to 88 ppm and the C1 of G and M were not distinguishable and observed at δ 101.96 ppm. The characteristic amide condensation was

8

Journal Pre-proof ascertained by the presence of amide carbon peak at δ 159.83 ppm. These peaks were observed to be shifted downfield in comparison to AA which could be accounted to the amide condensation. These evidences corroborate with the condensation of amine with AA. 3.2. BATCH ADSORPTION STUDIES 3.2.1. Effect of pH and adsorbent dose As the pH of solution was increased from 2 to 5, the Pb(II) ion uptake by AA and AmAA increased from 64.16 to 358.36 mg/g and 264.94 to 462.88 mg/g, respectively [Fig. 4(a)]. The percent removal efficiency also showed an increase with increase in pH for both the adsorbents. This can be attributed

of

to the fact that at low pH, elevated levels of proton/hydronium ions compete with metal ions for the

ro

carboxylate sites in case of AA [59]. Moreover, due to the high concentration of proton/hydronium ions in the adsorption medium, carboxyl groups present on AA surface could not ionize and the active sites

-p

remained protonated. As a consequence, the protonated polymer repels the positively charged metal

re

ion resulting in its poor adsorption. As the pH was increased from 2 to 5, deprotonation of carboxyl groups on AA surface was facilitated, inducing a negative charge on the surface and resulting in an

lP

electrostatic attraction for the metal ions onto the adsorbent polymer [49,60]. Therefore, the

[61,62].

na

carboxylate ions capture the Pb(II) ions by forming chelate complexes through surface complexation

On the other hand, in case of AmAA, this trend is due to the fact that at low pH, there is competition +

Jo ur

among H ions and the metal ions to bind with the basic amino (NH2) of AmAA. At high proton +

concentration, most of the NH2 groups of AmAA are converted to the ammonium ions (NH 3 ), which induce a positive charge to the surface of the material. Due to this surface charge at lower pH, the ammonium derivative AmAA repels the metal ion, leading to lesser adsorption of metal ions. At higher pH, the amino group gets deprotonated and exists in the neutral form, hence, the metal ion uptake and percent removal increases with increase in pH [44]. Thus, on the basis of above results pH 5.0 was taken as optimum pH as the metal ion uptake and percentage removal were maximum for both the adsorbents. Effect of adsorbent dosage on Pb(II) adsorption efficiency of both AA and AmAA was investigated by changing the adsorbent dose from 0.25 g/L to 1.0 g/L for 500 mg/L Pb(II) solution at pH 5. As the adsorbent dose was increased from 0.25 g/L to 1.0 g/L, a decrease in Pb(II) uptake (qe) from 392.96 to 349.08 mg/g and 516.68 to 383.46 mg/g with AA and AmAA, respectively was observed [Fig. 4(b)].

9

Journal Pre-proof This decrease in qe with increase in the adsorbent dose can be accounted to the number of active sites on the adsorbent surface remaining unsaturated due to availability of lesser number of Pb(II) ions per unit mass of the adsorbent. On the other hand, with increase in adsorbent dose from 0.25 g/L to 1.0 g/L, the percent removal of Pb(II) ion increased from 19.65 to 69.82% with AA and from 25.83 to 76.69% with AmAA [Fig. 4(b)]. This increase in Pb(II) adsorption, can be attributed to the increased adsorbent surface area and the number of available adsorption sites with increase in adsorbent dose [13,63] . 3.2.2. Effect of contact time and kinetic studies

of

It was studied by varying the contact time from 0 to 120 minutes. On increasing the contact time from

ro

2.5 to 120 minutes, percent Pb(II) removal increased from 10.11 to 19.49% and 15.02 to 25.67% with AA and AmAA, respectively [Fig. 4(c)]. This is attributed to abundance of free sites near the surface

-p

of adsorbent during the initial stages. Hence, there was lesser hindrance for the approaching metal

re

ions [38].

Lagergren pseudo-first-order and pseudo-second-order adsorption kinetic models were fitted to the

lP

data obtained from the experiment carried out to study the effect of contact time variation and linear plots were obtained (Fig. 5). From these linear plots, both qe and rate constant were obtained. A

na

comparison between the two adsorption kinetic models is presented in Table 2 which indicates that for both the adsorbents (AA and AmAA), the value of correlation coefficient is high for pseudo-second

Jo ur

order kinetic model and value of qe drawn for the same model are in agreement with experimental qe. 3.3 Equilibrium Studies

The effect of Initial ion concentration on Pb(II) uptake by AA and AmAA was studied by increasing the concentration from 100 to 800 mg/L. Upon increasing the initial concentration of Pb(II) in aqueous solution from 100 to 800 mg /L, an increase in Pb(II) uptake was observed from 215.84 to 395.72 mg/g and 304.60 to 535.87 mg/g with AA and AmAA, respectively. On the other hand, with AA and AmAA as adsorbent, percentage Pb(II) removal decreased from 53.96 to 12.37%, 76.15 to 16.75%, respectively [Fig. 4(d)]. This can be attributed to the fact that at lower initial ion concentrations, sufficient numbers of adsorption sites are available for the approaching metal ions, however, at higher concentrations, the numbers of Pb(II) ions are relatively higher as compared to number of available adsorption sites [64].

10

Journal Pre-proof Langmuir and Freundlich adsorption isotherm models were applied to the equilibrium adsorption data and both models were well fitted to the data (Fig. 6). Further, values of qm, adsorption energy (b) and dimensionless factor (RL) were determined from the linear fit diagram of Langmuir adsorption isotherm models and are given in Table 3. As the values of RL lies between 0 and 1, indicates favourable adsorption [37] of Pb(II) onto AmAA. Values of Kf and 1/n determined from Freundlich adsorption isotherm models. Here, the value of 1/n is less than 1 in both the cases which indicate strong Pb (II) adsorption on adsorbents [65]. 3.4. Evaluating Mechanism involved in the process

of

SEM-EDX analysis of AA, AmAA and their Pb(II) adsorbed counter parts were carried out to confirm

ro

the changes in the surface morphology and elemental composition (in %) of the adsorbents after Pb(II) adsorption Fig. 7. The micrographs of AA [Fig. 7(a)] and AmAA [Fig. 7(b)] showed the porous

-p

characteristics but after adsorption, these pore spaces were filled with Pb(II) resulting into a compact

re

structure [Fig. 7(c) and Fig. 7(d)]. The weight % of different elements in AA, AmAA and their Pb(II) adsorbed counterparts as per EDX analysis is given in Table 4. Pb(II) adsorbed AA and AmAA

by AA and AmAA.

lP

showed the 38.29% and 40.33% Pb, respectively, which indicate a significant adsorption of Pb(II) ion

na

The FTIR spectra of Pb(II) adsorbed AA showed that there is no participation of the anion (nitrate ion) of metal salt in adsorption of metal ion to AA, because there is no characteristic peak of nitrate -1.

Jo ur

stretching in the range 1340-1400 cm −1

However, there are significant changes in the range 1600–

650 cm which indicate the direct participation of carboxyl group in metal-alginate complexation [Fig. -1

8(a)]. Upon adsorption of Pb(II), the peaks at 1419.98 and 1642.96 cm , due to the presence of COO

-

-1

group in the FTIR spectra of AA, were shifted to 1413.87 and 1587.44 cm , respectively. The shift is attributed to the change in bonding strength of metal and oxygen of carboxylate group. As a consequence, the distance of the C-O bond of the carboxylate group shows a change, this leads to a shift of symmetric peak to lower energies [66]. Similarly, a significant change in the amine functional group of AmAA upon adsorption of Pb(II), is clearly evidenced by comparing the spectra of AmAA with metal adsorbed AmAA [Fig. 8(b)]. The -1

amine characterized by absorption band at 3544.64 cm in case of AmAA was found to merge with OH moiety in case of Pb(II) adsorbed AmAA. The absorption band due to -NH deformation observed -1

at 1433.99 cm in case of AmAA, disappeared upon metal ions adsorption by AmAA, which indicates

11

Journal Pre-proof the significant role of amine in the complexation of metal ions on to the surface of AmAA. The amide -1

-1

peak at 1630.26 cm in AmAA shifted to 1625.89 cm in presence of Pb(II) ions. TG analysis of Pb(II) adsorbed AA and AmAA was studied to reveal the changes in thermal stability of adsorbent upon metal ion binding because the thermal decomposition behavior of a metal ion bound polymer depends on its own macromolecular characteristics and the type of coordination geometry with the metal ion [67, 68]. The thermal decomposition of the polymer Pb(II) complexed AA and AmAA were similar to the polymer decomposition itself with a marked difference observed in the percent weight loss. The percent weight loss was 48.29 and 51.87% for AA and AmAA, respectively [Fig. 9

of

(a)]. The results are in complete agreement with amount of Pb(II) adsorption by the polymer AA and AmAA. The DTA analysis of Pb(II) adsorbed polymers showed marked shift in maxima form 253 and

ro

°

248 to 259 and 254 C for AA and AmAA, respectively [Fig. 9 (b)]. This could be accounted to the

-p

better stability of the Pb(II) complexed polymer leading to onset of polymer decomposition shifting to

The CP-MAS

re

higher temperature. 13

C NMR spectroscopic studies of Pb(II) adsorbed AA and Pb(II) adsorbed AmAA were

lP

carried out and significant changes were observed [Fig. 10 (a)]. In case of Pb(II) adsorbed AA, the

na

carbonyl carbon of the carboxylate moiety shifted downfield by Δ δ 4.45 ppm, which indicated strong interaction between Pb(II) and carboxylate group in AA. The carboxylate of G and M interact with

Jo ur

Pb(II) without distinction resulting in similar shift in the spectral range leading to the observation of a single peak at δ 177.37 ppm. Apart from this, C-1 carbon of both G and M subunits showed an upfield shift from δ 102.26 to 101.68 ppm. This upfield shift could be accounted to the dense electronic cloud of Pb(II) ions, leading to increase in the electronic density over C-1 carbon. Apart from this, the deconvolution studies indicate slight broadening of peak leading to improper resolution during GSD operation. However, the line broadening in case of CH-OH lies in the range as does the AA. Due to the formation of amide, a new peak was observed at δ 159.85 ppm which was accounted to the amide carbonyl carbon. A significant shift was observed in this amide peak from δ 159.85 to 160.57 ppm, which is a characteristic for participation of amide in Pb(II) ion binding. However, the amide peak at δ 173.53 ppm disappeared or shifted downfield merged with the peak due to the carboxylate carbon of the other monomer to δ 176.32 ppm. Further, the peak due to the carbon of ethylenediamine moiety showed an upfield shift from δ 72.00 to 71.85 ppm [Fig. 10(b)]. Based on the

12

Journal Pre-proof FTIR and CP-MAS

13

C NMR studies the possible interaction of Pb(II) with carboxyl group in case of

AA and with amide group in case of AmAA are presented in Scheme 2. The proposed coordination of Pb(II) ions corroborate with the spectral evidences obtained. Conclusion The introduction of nitrogenous functional moieties onto AA via DCC/NHS coupling reaction leads to formation of AmAA. The functional and surface properties of the amido-amine derivatives are different from the parent bio-macromolecule. The results of batch adsorption experiments show that Pb(II) adsorption efficiency of AmAA is significantly higher than AA. The mechanistic study using FTIR and 13

C NMR analysis of Pb(II) adsorbed AA and AmAA, indicates the participation of amide

of

CP-MAS

ro

group for Pb(II) adsorption in AmAA in place of carboxyl group involvement in case of AA. Hence, it can be concluded that the functionalization of amido-amine on AA improves its adsorptive efficiency

-p

due to participation of carbonyl and amine group in Pb(II) adsorption from aqueous medium in place

re

of carboxyl group in AA. The Pb(II) adsorption on AA and AmAA follow Lagergren Pseudo-second order adsorption kinetics and is well represented by both Langmuir and Freundlich adsorption

lP

isotherms. Thus it is submitted that ion exchange mechanism could be over ridden by suitable

Jo ur

na

scaffold designing of bio-macromolecules.

13

Journal Pre-proof References [1]

A. Basu, D. Saha, R. Saha, T. Ghosh, B. Saha, A review on sources, toxicity and remediation technologies for removing arsenic from drinking water, Res. Chem. Intermed. 40 (2014) 447485. https://doi.org/10.1007/s11164-012-1000-4.

[2]

R. Saha, R. Nandi and B. Saha, Sources and toxicity of hexavalent chromium, J. Coord. Chem. 64 (2011) 1782–1806. https://doi.org/10.1080/00958972.2011.583646.

[3]

S. Mittal, U. Vaid, Gh N. Najar and J.N. Babu, Removal of hexavalent chromium from aqueous solution: a comparative study of cone biomass of “Picea smithiana” and activated

charcoal,

Desalin.

Water

Treat.

57

(2016)

11081-11095.

[4]

of

https://doi.org/10.1080/19443994.2015.1038594. U. Vaid, S. Mittal, J. Nagendra Babu, Removal of hexavalent chromium from aqueous solution

ro

using biomass derived fly ash from Waste-to-Energy power plant, Desalin. Water Treat. 52 (2014) 7845-7855. https://doi.org/10.1080/19443994.2013.833554. D. Ghosh, R. Saha, A. Ghosh, R. Nandi, B. Saha, A review on toxic cadmium biosorption from contaminated

wastewater,

Desalin.

-p

[5]

Water

Treat.

53

(2015)

413-420.

[6]

re

https://doi.org/10.1080/19443994.2013.846233.

A.E. Burakov, E.V.Galunin, I.V. Burakova, A.E. Kucherova, S. Agarwal, A.G. Tkachev, V.K.

lP

Gupta, Adsorption of heavy metals on conventional and nanostructured materials for wastewater treatment purposes: A review, Ecotox. Environ. Safe. 148 (2018) 702-712.

[7]

na

https://doi.org/10.1016/j.ecoenv.2017.11.034. J. Qu, T. Song, J. Liang, X. Bai, Y. Li, Y. Wei, S. Huang, L. Dong, Y. Jin, Adsorption of lead (II) from aqueous solution by modified Auricularia matrix waste: A fixed-bed column study,

[8]

Jo ur

Ecotox. Environ. Safe. 169 (2019) 722-729. https://doi.org/10.1016/j.ecoenv.2018.11.085. M.A. Younis, R. Nadeem, A. Rehman, M. Iqbal, M.R. Younis, Q. Manzoor, Adsorption of Ag(I), Cr(VI) and Pb(II) from aqueous media onto different adsorbent types, Asian J. Chem. 27 (2015) 3308-3314. https://doi.org/10.14233/ajchem.2015.18610. [9]

M. Basu, A.K. Guha, L. Ray, Adsorption of Lead on lentil husk in fixed bed column bioreactor, Bioresource Techno. 283 (2019) 86 - 95. https://doi.org/10.1016/j.biortech.2019.02.133.

[10] D.H.K. Reddy, K. Seshaiah, A.V.R. Reddy, M.M. Rao, M.C. Wang, Biosorption of Pb

2+

from

aqueous solutions by Moringa oleifera bark: equilibrium and kinetic studies, J. Hazard. Mater. 174 (2010) 831-838. https://doi.org/10.1016/j.jhazmat.2009.09.128. [11] Z. Chen, X. Pan, H. Chen, X. Guan, Z. Lin, Biomineralization of Pb(II) into Pb-hydroxyapatite induced by Bacillus cereus 12-2 isolated from Lead-Zinc mine tailings, J. Hazard. Mater. 301 (2016) 531-537. https://doi.org/10.1016/j.jhazmat.2015.09.023.

14

Journal Pre-proof [12] G. Ren, Y. Jin, C. Zhang, H. Gu, J. Qu, Characteristics of Bacillus sp.PZ-1 and its biosorption to

Pb(II),

Ecotox.

Environ.

Safe.

11

(2015)

141-148.

https://doi.org/10.1016/j.ecoenv.2015.03.033. [13] T.A. Saleh, V.K. Gupta, A.A. Al-Saadi, Adsorption of lead ions from aqueous solution using porous carbon derived from rubber tires: Experimental and computational study, J. Colloid Interf. Sci. 396 (2013) 264-269. https://doi.org/10.1016/j.jcis.2013.01.037. [14] O. Olanipekun, A. Oyefusi, G.M. Neelgund, A. Oki, Adsorption of lead over graphite oxide, Spectrochim. Acta A 118 (2014) 857-860. https://doi.org/10.1016/j.saa.2013.09.088. [15] M.A. Assi, M.N. Hezmee, A.W. Haron, M.Y. Sabri, M.A. Rajion, The detrimental effects of lead on

human

and

animal

health,

Vet.

World

(2016)

660-671.

of

https://doi.org/10.14202/vetworld.2016.660-671.

9

ro

[16] P. Sharma, R.S. Dubey, Lead toxicity in plants, Braz. J. Plant Physiol. 17 (2005) 35-52. https://dx.doi.org/10.1590/S1677-04202005000100004

class

of

functionalized

silica

gel,

Arab.

J.

Chem.

10

(2017)

S81-S89.

re

http://doi.org/10.1016/j.arabjc.2012.06.010.

-p

[17] A.K. Kushwaha, N. Gupta, M.C. Chattopadhyaya, Adsorption behavior of lead onto a new

[18] A.P. Lim, A.Z. Aris, Continuous fixed-bed column study and adsorption modeling: Removal of

lP

cadmium (II) and lead (II) ions in aqueous solution by dead calcareous skeletons, Biochem. Eng. J. 87 (2014) 50-61. https://doi.org/10.1016/j.bej.2014.03.019.

for

lead-ion

na

[19] Q. Gao, X. Wang, H. Wang, D. Liang, J. Zhang, J. Li, Sulfhydryl-modified sodium alginate film adsorption,

Mater.

Lett.

254

(2019)

149-153.

Jo ur

https://doi.org/10.1016/j.matlet.2019.07.055. [20] M. Li, Z. Zhang, R. Li, J.J. Wang, A. Ali, Removal of Pb(II) and Cd(II) ions from aqueous solution by thiosemicarbazide modified chitosan, Int. J. Biol. Macromol. 86 (2016) 876-884. https://doi.org/10.1016/j.ijbiomac.2016.02.027. [21] S. Abbaszadeh, S.R.W. Alwi, C. Webb, N. Ghasemi, I.I. Muhamad, Treatment of leadcontaminated water using activated carbon adsorbent from locally available papaya peel biowaste, J. Clean. Prod. 118 (2016) 210 - 222. https://doi.org/10.1016/j.jclepro.2016.01.054. [22] M. Basu, A.K. Guha, L. Ray, Adsorption of Lead on cucumber peel, J. Clean. Prod. 151 (2017) 603-615. https://doi.org/10.1016/j.jclepro.2017.03.028. [23] D. Bulgariu, L. Bulgariu, Sorption of Pb(II) onto a mixture of algae waste biomass and anion exchanger resin in a packed-bed column, Bioresource Techno. 129 (2013) 374-380. https://doi.org/10.1016/j.biortech.2012.10.142. [24] Y. Dong, H. Lin, Competitive adsorption of Pb(II) and Zn(II) from aqueous solution by modified beer

lees

in a fixed

bed column, Process

Saf. Environ.

111 (2017)

263-269.

https://doi.org/10.1016/j.psep.2017.06.016.

15

Journal Pre-proof [25] Ö. Etci, N. Bektaş, M.S. Öncel, Single and binary adsorption of lead and cadmium ions from aqueous solution using the clay mineral beidellite, Environ. Earth Sci. 61 (2010) 231-240. https://doi.org/10.1007/s12665-009-0338-4. [26] C.M. Futalan, C.C. Kan, M.L. Dalida, K.J. Hsien, C. Pascua, M.W. Wan, Comparative and competitive adsorption of copper, lead, and nickel using chitosan immobilized on bentonite, Carbohyd. Polym. 83 (2011) 528-536. https://doi.org/10.1016/j.carbpol.2010.08.013. [27] H. Merrikhpour, M. Jalali, Comparative and competitive adsorption of cadmium, copper, nickel, and lead ions by Iranian natural zeolite, Clean Technol. Envir. 15 (2013) 303-316. https://doi.org/10.1007/s10098-012-0522-1. [28] B. Singha, S.K. Das, Removal of Pb(II) ions from aqueous solution and industrial effluent using biosorbents,

Environ.

Sci.

Pollut.

19

(2012)

2212-2226.

ro

https://doi.org/10.1007/s11356-011-0725-8.

R.

of

natural

[29] N. Kataria, V.K. Garg, Optimization of Pb (II) and Cd (II) adsorption onto ZnO nanoflowers

-p

using central composites design: isotherms and kinetics modeling, J. Mol. Liq. 271 (2018) 228239. doi:10.1016/j.molliq.2018.08.135.

binary

system

study,

re

[30] T. Şahan, Application of RSM for Pb(II) and Cu(II) adsorption by bentonite enriched with SH groups and a J.

Water

Process

Eng.

31

(2019)

100867.

lP

https://doi.org/10.1016/j.jwpe.2019.100867.

[31] L. Zhang, Y. Zeng, Z. Cheng, Removal of heavy metal ions using chitosan and modified chitosan:

A

review,

J.

Mol.

Liq.

214

(2016)

175-191.

na

https://doi.org/10.1016/j.molliq.2015.12.013.

[32] C.S.C. Chiew, H.K. Yeoh, P. Pasbakhsh, P.E. Poh, B.T. Tey, E.S. Chan, Stability and

Jo ur

reusability of alginate-based adsorbents for repetitive lead (II) removal, Polym. Degrad. Stabil. 123 (2016) 146-154. https://doi.org/10.1016/j.polymdegradstab.2015.11.022. [33] X.-H. Do, B.-K. Lee, Removal of Pb capsule

regeneration,

J.

2+

using a biochar-alginate capsule in aqueous solution and Environ.

Manage.

131

(2013)

375-382.

https://doi.org/10.1016/j.jenvman.2013.09.045. [34] M. Esmat, A.A. Farghali, M.H. Khedr, I.M. E.-Sherbiny, Alginate-based nanocomposites for efficient removal of heavy metal ions, Int. J. Biol. Macromol. 102 (2017) 272-283. https://doi.org/10.1016/j.ijbiomac.2017.04.021. [35] C.B., Godiya, M. Liang, S.M. Sayed, D. Li, L. Xiaolin, Novel alginate/polyethyleneimine hydrogel adsorbent for cascaded removal and utilization of Cu

2+

and Pb

2+

ions, J. Environ.

Manage. 232 (2019) 829-841. https://doi.org/10.1016/j.jenvman.2018.11.131. [36] S. Ravulapalli, R. Kunta, Removal of lead (II) from wastewater using active carbon of Caryota urens seeds and its embedded calcium alginate beads as adsorbents, J. Env. Chem. Eng. 6 (2018) 4298-4309. https://doi.org/10.1016/j.jece.2018.06.033.

16

Journal Pre-proof [37] U. Vaid, S. Mittal, J.N. Babu, Influence of Anion Induced Proton Abstraction on Cu(II) Adsorption

by

Alginic

Acid,

React.

Funct.

Polym.

97

(2015)

48-55.

https://doi.org/10.1016/j.reactfunctpolym.2015.10.006. [38] T.J.S. Vani, N.S. Reddy, P.R. Reddy, K.S.V.K. Rao, J. Ramkumar, A.V.R. Reddy, Synthesis, characterization, and metal uptake capacity of a new polyaniline and poly(acrylic acid) grafted sodium

alginate/gelatin

adsorbent,

Desalin.

Water

Treat.

52

(2014)

526-535.

https://doi.org/10.1080/19443994.2013.846460. [39] K. Vijayalakshmi, B.M. Devi, S. Latha, T. Gomathi, P.N. Sudha, J. Venkatesan, S. Anil, Batch adsorption and desorption studies on the removal of lead(II) from aqueous solution using nanochitosan/sodium alginate/microcrystalline cellulose beads, Int. J. Biol. Macromol.

104

of

(2017) 1483-1494. https://doi.org/10.1016/j.ijbiomac.2017.04.120. [40] Z. Wang, Y. Huang, M. Wang, G. Wu, T. Geng, Y. Zhao, A. Wu, Macroporous calcium alginate 2+

removal from water media, J. Env. Chem. Eng. 4 (2016) 3185-

-p

3192. https://doi.org/10.1016/j.jece.2016.06.032.

ro

aerogel as sorbent for Pb

[41] S. Cataldo, A. Gianguzza, D. Milea, N. Muratore, A. Pettignano, Pb(II) adsorption by a novel

re

activated carbon - alginate composite material. A kinetic and equilibrium study, Int. J. Biol. Macromol. 92 (2016) 769-778. https://doi.org/10.1016/j.ijbiomac.2016.07.099.

lP

[42] I. Anastopoulos, A Bhatnagar, D.N. Bikiaris, G.Z. Kyzas, Chitin Adsorbents for Toxic Metals: A Review, Int. J. Mol. Sci. 18 (2017), 114. https://doi.org/10.3390/ijms18010114.

na

[43] W. Boulaiche, B. Hamdi, M. Trari, Removal of heavy metals by chitin: equilibrium, kinetic and thermodynamic studies, Appl. Water Sci. 9 (2019), 39. https://doi.org/10.1007/s13201-0190926-8.

Jo ur

[44] M.-W. Wan, C.-C. Kan, B.D. Rogel, M.L.P. Dalida, Adsorption of copper (II) and lead (II) ions from aqueous solution on chitosan-coated sand, Carbohyd. Polym. 80 (2010) 891-899. . https://doi.org/10.1016/j.carbpol.2009.12.048. [45] J. Lu, R.-N. Jin, C. Liu, Y.-F. Wang, X.-k. Ouyang, Magnetic carboxylated cellulose nanocrystals as adsorbent for the removal of Pb(II) from aqueous solution, Int. J. Biol. Macromol. 93 (2016) 547-556. http://doi.org/10.1016/j.ijbiomac.2016.09.004. [46] A.S. Singha, A. Guleria, Use of Low Cost Cellulosic Biopolymer Based Adsorbent for the Removal of Toxic Metal Ions from the Aqueous Solution, Sep. Sci. Technol. 49 (2014) 25572567. http://doi.org/10.1080/01496395.2014.929146. [47] K.Y. Lee, D.J. Mooney, Alginate: Properties and biomedical applications, Prog. Polym. Sci. 37 (2012) 106-126. https://doi.org/10.1016/j.progpolymsci.2011.06.003. [48] Y. Huang, Z. Wang, Preparation of composite aerogels based on sodium alginate, and its application in removal of Pb

2+

and Cu

2+

from water, Int. J. Biol. Macromol. 107 (2018) 741-747.

https://doi.org/10.1016/j.ijbiomac.2017.09.057.

17

Journal Pre-proof [49] E.S. A,-Halim, S.S. A.-Deyab, Removal of heavy metals from their aqueous solutions through adsorption

onto

natural

polymers,

Carbohyd.

Polym.

84

(2011)

454-458.

https://doi:10.1016/j.carbpol.2010.12.001. [50] J.S. Yang, Y.J. Xie, W. He, Research progress on chemical modification of alginate: A review, Carbohyd. Polym. 84 (2011) 33 - 39. https://doi.org/10.1016/j.carbpol.2010.11.048. [51] P. Rani, P. Pal, J.P. Panday, S. Mishra, G. Sen, Alginic Acid Derivatives: Synthesis, Characterization and Application in Wastewater Treatment, J. Polym. Environ. 27 (2019) 27692783. https://doi.org/10.1007/s10924-019-01553-5. [52] A. Benettayeb,

E. Guibal, A. Morsli,

R. Kessas, Chemical modification of alginate for

enhanced sorption of Cd(II), Cu(II) and Pb(II), Chem. Eng. J. 316 (2017) 704-714.

of

https://doi.org/10.1016/j.cej.2017.01.131.

ro

[53] L.V.A. Gurgel, L.F. Gil, Adsorption of Cu(II), Cd(II), and Pb(II) from aqueous single metal solutions by succinylated mercerized cellulose modified with triethylenetetramine, Carbohyd.

-p

Polym. 77 (2009) 142-149. https://doi.org/10.1016/j.carbpol.2008.12.014. [54] I.P.S. Fernando, K.K.A. Sanjeewa, S.-Y. Kim, J.-S. Lee, Y.-J. Jeon, Reduction of heavy metal 2+

re

(Pb ) biosorption in zebrafish model using alginic acid purified from Ecklonia cava and two of its synthetic derivatives, Int. J. Biol. Macromol. 106 (2018) 330-337. http://doi.org/

lP

10.1016/j.ijbiomac.2017.08.027.

[55] T. Taubner, M. Marounek, A. Synytsy, Preparation and characterization of amidated of

alginic

acid,

Int.

J.

Biol.

Macromol.

103

(2017)

202-207.

na

derivatives

http://doi.org/10.1016/j.ijbiomac.2017.05.070. [56] G.T. Hermanson, Bioconjugate Techniques (Third Edition), (2013). Academic Press, pp-267-268.

Jo ur

https://doi.org/10.1016/B978-0-12-382239-0.00004-2 [57] S.R. Abulateefeh, M.A. Khanfar, R.Z.A. Bakain, M.O. Taha, Synthesis and characterization of new derivatives of alginic acid and evaluation of their iron(III)-crosslinked beads as potential controlled

release

matrices,

Pharm.

Dev.

Technol.

19

(2013)

856-867.

https://doi.org/10.3109/10837450.2013.836222. [58] F. Llanes, F. Sauriol, F.G. Morin, A.S. Perlin, An examination of sodium alginate from Sargassum

by

NMR

spectroscopy,

Can.

J.

Chem.

75

(1997)

585-590.

https://doi.org/10.1139/v97-069. [59] N. Dizadji, N.A. Anaraki, N. Nouri, Adsorption of chromium and copper in aqueous solutions using

tea

residue,

Int.

J.

Environ.

Sci.

Te.

8

(2011)

631-638.

https://doi.org/10.1007/BF03326248. [60] A. Hashem, M.M. Elhmmali, Modification of sodium alginate for the removal of Cd(II) from aqueous

solutions,

Polym.-Plast.

Technol.

45

(2006)

707-712.

http://dx.doi.org/10.1080/03602550600609648.

18

Journal Pre-proof [61] A.Z.M. Badruddoza, Z.B.Z. Shawon, T.W.J. Daniel, K. Hidajat, M.S. Uddin, Fe 3O4/cyclodextrin polymer nanocomposites for selective heavy metals removal from industrial wastewater, Carbohyd. Polym. 91 (2013) 322 - 332. https://doi.org/10.1016/j.carbpol.2012.08.030. [62] M. Rafatullah, O. Sulaiman, R. Hashim, A. Ahmad, Adsorption of copper (II) onto different adsorbents,

J.

Disper.

Sci.

Technol.

31

(2010)

918-930.

https://doi.org/10.1080/01932690903224003. [63] A. Örnek, M. Özacar, İ.A. Şengil, Adsorption of lead onto formaldehyde or sulphuric acid treated acorn waste: Equilibrium and kinetic studies, Biochem. Eng. J. 37 (2007) 192-200. https://doi.org/10.1016/j.bej.2007.04.011. [64] M. Nadeem, A. Mahmood, S.A. Shahid, S.S. Shah, A.M. Khalid, G. McKay, Sorption of lead

of

from aqueous solution by chemically modified carbon adsorbents, J. Hazard. Mater. 138

ro

(2006) 604-613. https://doi.org/10.1016/j.jhazmat.2006.05.098.

[65] O. Hamdaoui, E. Naffrechoux, Modelling of adsorption isotherms of phenol and chlorophenols

-p

onto granular activated carbon: Part I. Two-parameter models and equations allowing determination of thermodynamic parameters, J. Hazard. Mater. 147 (2007) 381-394.

re

https://doi.org/10.1016/j.jhazmat.2007.01.021.

[66] S.K. Papageorgiou, E.P. Kouvelos, E.P. Favvas, A.A. Sapalidis, G.E. Romanos, F.K. Katsaros,

lP

Metal-carboxylate interactions in metal–alginate complexes studied with FTIR spectroscopy, Carbohyd. Res. 345 (2010) 469-473. https://doi.org/10.1016/j.carres.2009.12.010.

na

[67] P. Girija, M. Beena, Sorption of Trace Amounts of Pb(II) Ions on an Ion Imprinted Interpenetrating Polymer Network Based on Alginic Acid and Crosslinked Polyacrylamide, Sep. Sci. Technol. 49 (2014) 1053-1061. https://doi.org/10.1080/01496395.2013.866682.

Jo ur

[68] N. Sebastian, B. George, B. Mathew, Metal complexes of poly(acrylic acid): Synthesis, characterization and thermogravimetric studies, Polym. Deg. Stab. 60 (1998) 371-374. https://doi.org/10.1016/S0141-3910(97)00095-5.

19

Journal Pre-proof Fig. 1. FTIR spectra of AA and AmAA Fig. 2(a). Thermo-gravimetric (TG) decomposition behavior of AA and AmAA (b). Differential thermal analysis (DTA) of AA and AmAA 13

Fig. 3(a). Global Spectral Deconvolution of the CP-MAS C NMR spectra of AA (b). Global Spectral Deconvolution of the CP-MAS

13

C NMR spectra of AmAA

Fig. 4(a). Effect of pH on Pb(II) removal by AA and AmAA (Initial ion conc. = 500 mg/L, Adsorbent o

dose = 0.5 g/L, Contact time = 2 hrs, Temperature = 25+1 C, Shaking speed = 200 rpm).

Contact

time

=

2

hrs,

Shaking

speed

=

200

of

(b). Effect of adsorbent dose on Pb(II) removal and its uptake (Initial ion conc. = 500 mg/L, pH = 5, rpm,

Temperature

=

o

25+1 C).

g/L,

Temperature

o

=

25+1 C,

Shaking

speed

=

200

rpm).

-p

0.25

ro

(c). Effect of contact time on Pb(II) removal (Initial ion conc. = 500 mg/L, pH = 5, Adsorbent dose =

(d). Effect of Initial ion concentration on Pb(II) removal and its uptake (pH = 5, Adsorbent dose = 0.25 o

re

g/L, Temperature = 25+1 C, Contact time = 30 minutes, Shaking speed = 200 rpm,)

lP

Fig. 5(a). Lagergren pseudo-first order kinetic plots for adsorption of Pb(II) on AA and AmAA (b). Lagergren pseudo-second order kinetic plots for adsorption of Pb(II) on AA and AmAA

na

Fig. 6(a). Langmuir adsorption isotherm for adsorption of Pb(II) on AA and AmAA

Jo ur

(b). Freundlich adsorption isotherm

Fig. 7(a). Field emission scanning electron micrograph of (a) AA (b) AmAA (c) Pb(II) adsorbed AA and (d) Pb(II) adsorbed AmAA

Fig. 8(a). FTIR spectra of AA and Pb(II) adsorbed AA (b). FTIR spectra of AmAA and Pb(II) adsorbed AmAA Fig. 9 (a). Thermo-gravimetric (TG) decomposition behavior of Pb(II) adsorbed AA and AmAA (b). Differential thermal analysis (DTA) of Pb(II) adsorbed AA and AmAA Fig. 10(a). Global Spectral Deconvolution of the CP-MAS (b). Global Spectral Deconvolution of the CP-MAS

13

13

C NMR spectra of Pb(II) adsorbed AA

C NMR spectra of Pb(II) adsorbed AmAA

Scheme 1. Synthesis of AmAA Scheme 2. Proposed complexation of (a) Pb(II) adsorbed AA and (b) Pb(II) adsorbed AmAA

20

Journal Pre-proof

Table 1. Percent elemental composition of AA and AmAA by elemental (CHNO) analysis

Percent composition Element

AA

AmAA

Theoretical

Experimental

Theoretical

Experimental

Carbon

35.964

35.958

41.325

41.561

Hydrogen

4.995

5.017

6.626

6.674

Nitrogen

--

--

11.595

11.495

Oxygen

56.743

59.025

40.453

40.271

C7.9H13.7N1.9O5.05.

of

C6H7.8O6Na0.2.1.1

0.75H2O

na

lP

re

-p

ro

H2O

Jo ur

Formula

21

Journal Pre-proof Table 2. Comparison between Lagergren Pseudo-first order and Pseudo-second order Adsorption kinetic plot for AA and AmAA Pseudo-first order kinetic

Pseudo-second order kinetic

model

model

Experimental Adsorbent

qe (mg/g)

qe

K1,ads

(mg/g)

(min )

R

-1

2

qe (mg/g)

K2,ads (mg/g

R

2

−1

min )

389.78

180.30

0.0299

0.9240

400.53

0.0002

0.9995

AmAA

513.39

199.53

0.0350

0.9664

512.82

0.0001

0.9997

Jo ur

na

lP

re

-p

ro

of

AA

22

Journal Pre-proof

Adsorbent

Table 3. Langmuir and Freundlich isotherm constants for adsorption of Pb(II) on AA and AmAA

Langmuir adsorption isotherm qm (mg/g)

R

b

2

RL

(L/mg)

454.55

0.9886

0.0117

AmAA

555.56

0.9981

0.0269

R

0.10870.6499 0.02590.6092

2

1/n

Kf

0.9410

0.2549

77.8279

0.9889

0.1769

175.5809

Jo ur

na

lP

re

-p

ro

of

AA

Freundlich adsorption isotherm

23

Journal Pre-proof Table 4. Elemental composition of AA, AmAA before and after Pb(II) adsorption by EDX analysis

Element

Weight%

Weight%

Weight%

[in Pb(II)

[in AA]

adsorbed AA]

Weight%

[in Pb(II)

[in AmAA]

adsorbed AmAA]

44.52

36.77

45.61

33.54

O

54.65

21.29

36.30

25.94

Na

0.82

0.04

0.34

0.07

N

--

3.60

17.76

0.12

Pb

--

38.29

--

40.33

Jo ur

na

lP

re

-p

ro

of

C

24

Journal Pre-proof

Author statement Upma Vaid: Conceptualization, writing- original draft preparation, methodology Sunil Mittal: Conceptualization, Supervision, Resources, Review & Editing J. Nagendra Babu: Visualization, Investigation, Formal analysis

Jo ur

na

lP

re

-p

ro

of

Ravishankar Kumar: Writing and Editing

25

Journal Pre-proof

Highlights:  Amido–amine derivative of alginic acid (AmAA) was synthesized from condensation of alginic acid with ethylenediamine  The functionalized polymer AmAA was characterized by CHN analysis for 95% condensation.  The soft binding nitrogen moiety enhances Pb(II) adsorption due to participation of carbonyl and amine in case of AmAA as compared to ion-exchange carboxyl moiety in AA.

 The amide carbonyl and amine group was involved in metal chelation as indicated by 13C CP-

Jo ur

na

lP

re

-p

ro

of

MAS NMR analysis.

26

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10