Fabrication of novel iminodiacetic acid-functionalized carboxymethyl cellulose microbeads for efficient removal of cationic crystal violet dye from aqueous solutions

Journal Pre-proof Fabrication of novel iminodiacetic acid-functionalized carboxymethyl cellulose microbeads for efficient removal of cationic crystal violet dye from aqueous solutions

Ahmed M. Omer, Gehad S. Elgarhy, Gehan M. El-Subruiti, Randa E. Khalifa, Abdelazeem S. Eltaweil PII:

S0141-8130(19)38799-9

DOI:

https://doi.org/10.1016/j.ijbiomac.2020.01.182

Reference:

BIOMAC 14486

To appear in:

International Journal of Biological Macromolecules

Received date:

29 October 2019

Revised date:

4 January 2020

Accepted date:

19 January 2020

Please cite this article as: A.M. Omer, G.S. Elgarhy, G.M. El-Subruiti, et al., Fabrication of novel iminodiacetic acid-functionalized carboxymethyl cellulose microbeads for efficient removal of cationic crystal violet dye from aqueous solutions, International Journal of Biological Macromolecules(2018), https://doi.org/10.1016/j.ijbiomac.2020.01.182

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© 2018 Published by Elsevier.

Journal Pre-proof

Fabrication of novel iminodiacetic acid-functionalized carboxymethyl cellulose microbeads for efficient removal of cationic crystal violet dye from aqueous solutions Ahmed M. Omera,*, Gehad S. Elgarhyb, Gehan M. El-Subruitib, Randa E. Khalifaa, Abdelazeem S. Eltaweilb,* a

Polymer Materials Research Department, Advanced Technology and New Materials Research

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Institute (ATNMRI), City of Scientific Research and Technological Applications (SRTA-City), New Borg El-Arab City, P. O. Box: 21934, Alexandria, Egypt

Chemistry Department, Faculty of Science, Alexandria University, Alexandria, Egypt

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b

addresses:

[email protected]

(Ahmed

M.

Omer),

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E–mail

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*Corresponding authors:

[email protected] (Abdelazeem S. Eltaweil); Tel: +2034593414- Fax:

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+2034593414.

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Abstract

Novel anionic adsorbent microbeads were fabricated based on surface functionalization of

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p-benzoquinone-carboxymethyl cellulose (CMC-PBQ) activated microbeads with iminodiacetic

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acid (IDA). The developed IDA@CMC-PBQ microbeads were characterized by FT-IR, TGA, SEM, XPS and zeta potential analysis tools. Ion exchange capacity measurements proved the successful generation of extra carboxylic groups on the surface of IDA@CMC-PBQ microbeads with a maximum value reached 3.984 meq/g compared to 1.32 meq/g for neat CMC microbeads. The fabricated microbeads were tested for the removal of cationic crystal violet (CV) dye from aqueous solutions under various adsorption conditions. The results clarified that the removal percent of CV dye was augmented and reached a maximum value of 91.56% with increasing IDA concentration up to 0.15 M. Moreover, the experimental data were well-fitted both

Journal Pre-proof Langmuir and Freundlich isotherms with a maximum adsorption capacity of 107.52 mg/g. while the adsorption process was obeyed the pseudo-second order kinetic model. The developed adsorbent displayed respectable reusability after five sequential cycles and exhibited higher adsorption ability towards cationic CV dye compared to cationic methylene blue (MB) and anionic methyl orange (MO) dyes. Therefore, IDA@CMC-PBQ adsorbent could be effectually used as a convenient and reusable adsorbent for removing cationic dyes from their aqueous

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solutions.

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Keywords: Carboxymethyl cellulose; Functionalized microbeads; Dye removal; Isotherms;

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Kinetics; Reusability.

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1. Introduction

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Recently, water pollution by many manufacturing processes has become a significant cause

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of concern for scientists and a social priority. Release of hazardous pollutants into water is considered principal reason for water contamination [1]. Massive quantities of dyes are being

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applied in many industrial fields like pigments, papers, printing, textiles, cosmetics and food

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processing [2, 3]. These dyes have harmful effects on human health owing to their chemical stability and non-biodegradability [4, 5]. Crystal violet (CV) is a water-soluble cationic dye with a complicated structure, and also known as basic violet 3, methyl violet 10B and gentian violet. CV dye has been widely used in various medical fields as an external skin disinfectant in humans, active ingredient in Gram’s stain and a bacteriostatic agent [6]. In addition, it has been applied in textiles, printing ink and paints as a purple dye. However, CV dye causes severe health problems such as eye irritation, permanent injury to the cornea, nausea, breathing difficulty and hypertension [7, 8].

Journal Pre-proof Three different technologies have been adopted for wastewater treatment including physicochemical, chemical and biological processes. Physicochemical processes such as coagulative precipitation, flotation, membrane separation, electrolysis, flocculation and adsorption have been reported as treatment techniques for wastewater from numerous contaminants [9-11]. Besides, chemical technology includes processes such as ferric-carbon micro-electrolysis technology, ozonation, photocatalytic oxidation and catalytic degradation [12-15]. On the other

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hand, biochemical technology involves sequencing batch reactors, up-flow anaerobic sludge bed

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and membrane bioreactor processes [16, 17].

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One of the most effective and economically preferable techniques for wastewater treatment

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is adsorption [18]. Furthermore, the growth of eco-friendly and efficient adsorbents with the

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supreme ability for adsorption has become a great demand for researchers. Adsorbents based on natural polymers such as polysaccharides have been appeared recently [19-22]. Chitosan [23, 24],

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pullulan [25], starch and its derivatives [26], alginate [27-29] and chitin [30] are the most

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deliberated polysaccharides [31]. Carboxymethyl cellulose (CMC) is an anionic [32] macromolecular polysaccharide with numerous carboxylic and hydroxyl groups [33]. CMC has

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been effectively applied in medical, pharmaceutical and water treatment fields [32, 34, 35]. Hence, the presence of anionic groups does not only improve the solubility of CMC but also enhances its efficiency for cationic contaminants removal through the ionic interaction process [36]. Recently, several modifications have been utilized for improving the mechanical stability and adsorption properties of CMC such as grafting, crosslinking

and composite formation [36, 37]. CMC

hydrogels have been considered one of the preferable forms for CMC-based adsorbents owing to their chemical stability, easy separation and sizable area available for adsorption [38].

Journal Pre-proof The main goal of this work was to fabricate novel and efficient functionalized CMC microbeads for CV dye removal. The surface of CMC microbeads was firstly activated using pbenzoquinone (PBQ) which acts as an activator as well as a coupling agent, and then followed with surface functionalization with iminodiacetic acid (IDA) in order to generate further anionic carboxylic groups. The as-fabricated IDA@CMC-PBQ microbeads were well-characterized, and their aptitude for the adsorptive removal of CV dye was investigated using a batch adsorption

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process under different conditions. Moreover, isotherms and kinetics of the removal process were

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studied. The ability of IDA@CMC-PBQ adsorbent to reuse for several cycles was also evaluated.

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2. Experimental

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2.1. Materials

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Carboxymethyl cellulose sodium salt (CMC; Mw 90000, DS 0.7), p-benzoquinone (PBQ)

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(99 %), FeCl3.6H2O and iminodiacetic acid (98%) were purchased from Aladdin Industrial Corporation (Shanghai, China). The cationic dye, crystal violet (CV; C.I. 42555; dye content

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90%) was obtained from Merck and its characteristics are presented in Table 1. Anionic

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methylene blue tri-hydrate dye (MB) was supplied from (NICE CHEM-ICALS Pvt. Ltd., COCHIN). Ctionic methyl orange dye (MO) was purchased from Aladdin Industrial Corporation (Shanghai, China). All chemicals and solvents were used as received without further purifications. 2.2. Preparation of CMC microbeads In a typical experiment, CMC (3%: w/v) was dissolved in a hot distilled water and stirred continuously until complete solubilization. Then, CMC solution was dropped at room temperature into FeCl3 solution (3% w/v) via a plastic syringe (3 cm3) for congealing. After 30 min, the

Journal Pre-proof resultant CMC microbeads were collected tenderly and repeatedly washed with distilled water. The formed wet microbeads were divided into two portions; the first portion was dried at 30 ºC for 24 h, while the second portion was subjected for further modifications. 2.3. Preparation of IDA@CMC-PBQ microbeads In order to activate the hydroxyl groups on CMC microbeads surfaces, the previously

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prepared CMC wet microbeads were steeped in PBQ solution (0.04M) at 30 ºC and pH 10 for 60 min with a continuous gentle stirring. The resultant PBQ-activated CMC (CMC-PBQ) microbeads

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were quietly rinsed and washed several times with distilled water to eliminate the unreacted PBQ

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molecules. After that, the CMC-PBQ microbeads were soaked in IDA solution with final

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concentrations ranged from 0.025 to 0.2 M for 30 min at 30 ºC. The formed IDA@CMC-PBQ

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functionalized microbeads were removed from the IDA solution and washed numerous times until neutrality to eliminate the residual IDA molecules and finally dried at room temperature.

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2.4. Instrumental characterization

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The functional groups of the prepared microbeads were examined using Fourier Transform

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Infrared Spectroscopy (FT-IR, Model 8400 S, Shimadzu, Japan). Moreover, the thermal properties were inspected by the thermogravimetric analyzer (TGA, Model 50/50H, Shimadzu, Japan). Scanning electron microscopy (SEM, Model Jsm 6360 LA, Joel, Japan) was used for studying the morphological surface disparities before and after modification of CMC microbeads. Besides, X-ray photoelectron spectroscopy (XPS, Kratos Analytical, Manchester, UK) was applied to signify the adsorbent surface elements. Surface charges variation of CMC and IDA@CMC-PBQ functionalized microbeads were investigated using Zetasizer Nano ZS (Malvern Instruments, Malvern, UK). 2.5. Determination of IEC

Journal Pre-proof IEC measurements were performed to estimate the number of carboxylic groups exists on the surface of the microbeads (Eq.1). Depending on the previously reported acid-base titration procedure [39], for each IDA concentration, a known amount of IDA@CMC-PBQ microbeads was soaked at room temperature in 20 mL of NaCl solution (2 M) for 12 h under a gentle shaking for allowing the exchange of Na+ ions with H+ ions of COOH groups on the surface of microbeads. After that, the mixture was filtered, and the solution was followed with titration

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against NaOH (0.1 M) solution concerning control (i.e. without sample addition) using

)=

𝑉𝑁𝑎𝑂𝐻 × 𝐶𝑁𝑎𝑂𝐻 𝑊𝑆

(1)

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𝑔

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𝑚𝑒𝑞

𝐼𝐸𝐶 (

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phenolphthalein as an indicator. The IEC value was estimated using the following equation:

Where, V and C are the consumed volume and concentration of NaOH solution, respectively,

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2.6. Batch adsorption studies

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and WS is the weight of the tested sample.

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The removal of CV dye by IDA@CMC-PBQ microbeads was carried out using a batch

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adsorption technique. Known amounts of IDA@CMC-PBQ microbeads (0.025-0.2 g) were soaked in CV dye (50 mL). The medium pH was adjusted over the range 2 -10 by HCl (0.1 M) and NaOH (0.1 M) solutions. The removal process was investigated at different CV dye concentrations (25200 mg/L) and variable temperatures ranged from 25 to 45 ºC under different agitation speeds (25–200 rpm). For each adsorption experiment, samples were collected after time intervals (5, 15, 30, 60, 90, 120, 180 and 240 min), while the remained CV dye concentration was assayed at 590 nm via a UV-Vis spectrophotometer. The following equations estimated the removal (%) and the adsorption capacity (q):

Journal Pre-proof 𝑅𝑒𝑚𝑜𝑣𝑎𝑙(%) =

𝐶0 − 𝐶𝑡 𝐶0

× 100

𝑞 (𝑚𝑔⁄𝑔) = (𝐶0 − 𝐶𝑡 ) ×

(2)

𝑉

(3)

𝑚

Where q represents the adsorption capacity (mg/g), Co and Ct are the CV concentration (mg/L) at time zero and t. V represents the used volume of CV (L), and m is the mass of microbeads (g).

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Fig.1 represents laboratory images of freshly prepared CMC and IDA@CMC-PBQ

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microbeads, and images before and after the adsorption process. Besides, the ability of the developed microbeads to adsorb other cationic dyes such as methylene blue (MB) as well as

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anionic methyl orange (MO) dye was also tested. In brief, 0.05 g of IDA (0.15 M)@CMC-PBQ

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microbeads was immersed into 50 mg/L of tested dye solution with a fixed pH value (pH 8) for

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120min. The adsorption process was conducted at 25 °C under constant shaking rate (100rpm). The residual dye concentrations after completion of the adsorption process were assayed at 664nm

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2.7. Reusability study

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for MB dye and 464nm for MO dye using UV–vis spectrophotometer.

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Reusability of the developed IDA@CMC-PBQ adsorbent for CV dye adsorption was evaluated using several adsorption-desorption cycles. For microbeads regeneration, the dyeadsorbed microbeads were rinsed after completing the CV dye adsorption process and soaked under continuous shaking (50 rpm) for 2 h at 25 ºC in HCl (0.5 M) /ethanol (98%) solution as a desorption medium. The aptitude of the functionalized microbeads to be reused was studied for 5 repeated cycles. 2.8. Statistical analysis

Journal Pre-proof All adsorption and IEC experiments were conducted in triplicate (n=3), while the gained data were presented as a mean value corrected by the standard deviation (± SD). 3. Results and discussion 3.1. Surface modification The surface of the CMC microbeads was functionalized through activation of the present

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OH- groups under alkaline conditions by PBQ molecules which acts as coupling and activator

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agent. The reason for the activation process is to produce active sites on the CMC microbeads

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surface. Then, the activated CMC-PBQ microbead could be easily functionalized with the IDA

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molecules through covalent binding of imine groups (N-H) of IDA with the activated hydoxyl groups of CMC microbeads [40]. Fig. 2 represents the proposed activation and functionalization

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pathways for the fabrication of IDA@CMC-PBQ microbeads.

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3.2. IEC and zeta potential measurements

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The generated carboxylic groups on the surface of IDA@CMC-PBQ microbeads were

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estimated using IEC determination with different IDA concentarions (0.025-0.2 M) as shown in Fig.3. The results revealed that IEC values were augmented and reached a maximum value of 3.984 meq/g with rising IDA content up to 0.15 M compared to 1.321 meq/g for neat CMC microbeads. Increasing IEC value could be attributed to the new carboxylic groups generated on the functionalized microbeads surface with increasing IDA concentration. However, there is no noticeable increase in IEC value with a further increase of IDA concentrations beyond 0.15 M due to the limited number of the activated OH groups on the surface of CMC-PBQ microbeads.

Journal Pre-proof Besides, Fig. 3 presented also the zeta potential values of CMC and IDA@CMC-PBQ microbeads. The results elucidated that all samples are negatively charged with a stable dispersion, and zeta potential values of IDA@CMC-PBQ microbeads are much higher than its value in the case of neat CMC microbeads. In addition, the magnitude of the negative charges increased significantly with increasing IDA content as a result of increasing the negatively charged carboxylate anions on the functionalized microbeads surface. The gained results are in a good

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agreement with the obtained IEC results.

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3.3. FT-IR anlysis

FT-IR spectra of CMC (a), CMC-PBQ (b) and IDA@CMC-PBQ (c) microbeads were

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investigated in Fig. 4a. Broad bands in the range 3700-3300 cm-1 are assigned for the stretching

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vibration of –O-H groups. Another characteristic band for CMC appeared at 2921 cm-1 is attributed to the C-H groups. Furthermore, bands at 1637 cm-1 and 1450 cm-1 are attributed to the

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stretching asymmetric and symmetric vibration of the carboxylate groups. A distinctive band at

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1078 cm-1 appeared owing to the present ether group (C-O-C). Besides, a noticeable increase in

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the intensity of the band between 3300-3700 cm-1 as a result of the combination between CMCPBQ and the N-H groups incorporated with IDA modification, as well as the band at 1637 cm-1 became more intense by IDA modification due to the newly produced carboxylic groups. 3.4. TGA To investigate the thermal stability of the fabricated microbeads, TGA was performed as presented in Fig 4b. It is apparent that the degradation process of the polymer requires three primary stages to occur; at the beginning from 27 to 111 oC about 11.10 % of the material weight has been lost due to vaporization of water molecules associated with the polymer. Then, from 111

Journal Pre-proof to 202 oC the weight loss of 6.48 % was observed, which could be attributed to the abstraction of carbon dioxide from the polymer chain. A third stage occurs in the temperature range from 202 to 600 oC at which the polymer degradation reaches its top value (50.84 % weight loss) due to the decomposition of CMC lattice structure. Identical TGA curves were observed for both CMC and IDA@CMC-PBQ. Moreover, the calculated T50% (Table 2) reflects that the thermal stability of

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IDA@CMC-PBQ microbeads does not significantly change upon modification.

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3.5. SEM analysis

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The external surface morphology of microbeads has been examined using SEM as displayed in Fig.5. From the SEM images, it is evident that the morphology of CMC is considerably

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different compared to CMC-PBQ and IDA@CMC-PBQ microbeads. The CMC microbeads have

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severe wrinkles and rough surface, which is attributed to the partial collapse of CMC polymer during drying. However, after PBQ surface functionalization, the softened structure was obtained,

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while a dead smooth surface was observed. This behaviour may be due to the polarization

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3.6. XPS analysis

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variance between CMC and IDA.

XPS analysis was conducted to prove the presence of the microbeads elements and to assure the reaction between CV dye and microbeads. As presented in Fig. 6, the broad scan XPS spectrum (Fig.6) corroborates that the adsorbent contains C1s, O1s, and N1s before and after adsorption of CV dye. However, N1s spectrum shifted from 399.65 eV to lower binding energy at 398.98 eV after dye adsorption convenient to the amine group of IDA with an additional band at 401.27 eV convenient to the ionized state of the nitrogen in CV dye [41]. Moreover, the N1s peak

Journal Pre-proof intensity became higher in the post-adsorption spectrum due to the presence of nitrogencontaining dye. 3.7. Factors affecting CV dye adsorption The generated carboxylic groups on the adsorbent surface are expected to improve the process of adsorption. From the perspective of surface chemistry in an aqueous phase, two

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proposed mechanisms for the adsorption of cationic CV dye could be occurred, and both of them

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require the adsorbent to be negatively charged. The first is the electrostatic interactions between the positive and negative charges at the optimum pH. Where, most of carboxylic groups of

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IDA@CMC-PBQ microbeads are ionized to carboxylate anions (-COO−) and the adsorbent

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surface became more negative. This in turn leads to boosting the attraction forces between the

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positively charged CV dye molecules and the anionic surface of adsorbent. The second mechanism concerned with the hydrogen bonding interaction between the reactive free OH

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groups on the adsorbent surface and the imines groups of CV dye molecules. Several factors

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affecting the adsorption process were explored.

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3.7.1. Effect of IDA concentration The consequence of IDA concentration (0.025-0.2 M) was examined to evaluate its impact on the adsorption capability of IDA@CMC-PBQ adsorbent using 0.05 g of microbeads dose and 50 mg/L of CV dye at constant contact time (120 min), pH 8, shaking rate (100 rpm) and temperature (25 °C). Fig. 7a clarified that the adsorption process was improved with increasing the IDA concentration from 0.025 up to 0.15 M. Where, maximum removal (%) and maximum adsorption capacity values were recorded 91.5% and 45.78 mg/g and recorded by 0.15 M IDA@CMC-PBQ microbeads compared with 48.5% and 28.82 mg/g for native CMC

Journal Pre-proof microbeads. These observations could be explained by increasing number of the negatively charged COO- groups on the functionalized microbeads surface, which in turn increases the removal (%) and the adsorption capacity values. Nevertheless, a further increase in IDA content up to 0.2 M has no noticeable effect on the adsorption process, where all the activated OHgroups of CMC surface were functionalized with 0.15 M IDA and recorded the highest IEC value as stated previously. Therefore, the adsorption process was not affected with further

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increasing IDA concentration beyond 0.15 M. As a result, IDA@CMC-PBQ microbeads (0.15 M

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IDA) were chosen for the subsequent adsorption experiments.

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3.7.2. Effect of pH

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Indeed, pH of the adsorption medium is a paramount factor which controls the charges on

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the adsorbent surface and subsequently affects its removal efficiency. Fig. 7b shows the variation of the adsorption capacity of IDA@CMC-PBQ microbeads with pH values. The results

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illustrated that pH has a high impact on the CV adsorption, where the removal of CV increased

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gradually from 58.6 to 91.5% with rising pH value from 2 to 8. These observations could be

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clarified by deprotonating of the surface carboxylic groups of DA@CMC-PBQ microbeads at higher pH values and hence, increasing the attraction forces between the positively charged CV dye and the negatively charged COO- groups. Thus, the removal (%) and the adsorption capacity increase accordingly. In contrast, at the lower pH values, presence of excess H+ ions hinder the adsorption process, since they compete with the cationic CV molecules for the present adsorption active sites resulting in lower adsorption values. 3.7.3. Effect of adsorbent dose

Journal Pre-proof IDA@CMC-PBQ microbeads dose was varied from 0.025 to 0.2 g, while all the other parameters were fixed. It can be seen from Fig. 7c, that the removal (%) was enhanced considerably and recorded maximum value of 99.9% with increasing microbeads dose up to 0.1 g, while further increase in the microbeads amount up to 0.2 g has no observable effect since a complete dye removal was achieved by 0.1 g. These results could be related the presence of extra adsorption free sites with the larger adsorbent amount. On the other hand, values of the

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adsorption capacity decreased gradually from 72.15 mg/g to 12.49 mg/g with increasing the

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adsorbent dose up to 0.2 g owing to the converse proportion between the adsorption capacity and

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the amount of microbeads as stated in equation 3. Increasing the adsorbent amount increases the

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number of residual adsorption sites [42], and as a result, leads directly to decreasing the adsorbed quantity of CV dye per unit mass of adsorbent. Besides, further increasing adsorbent dose creates

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aggregations of the adsorbent microbeads, which decrease the exposed surface area, and the

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adsorption capacity decreases consequently.

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3.7.4. Effect of medium temperature

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Fig. 7d represents the consequence of temperature (25-45 oC) on the removal of CV by IDA@CMC-PBQ microbeads. The results demonstrated that the removal (%) was slightly enhanced from 91.5 to 95.6% with a maximum adsorption capacity 47.8 mg/g with rising temperature from 25 to 30 °C, owing to the dispersion as well as the diffusion rates of CV dye through the outer layer of the adsorbent microbeads. the dispersion as well as the diffusion rates of CV dye through the outer layer of the adsorbent microbeads. On the contrary, the adsorption process was conversely affected with further increasing temperature beyond 30 °C. Where, the removal (%) was gradually decreased and recorded 63.3% with elevating temperature up to 45

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C, while the maximum adsorption capacity decreased to 31.6 mg/g. This decline is associated

with the decreasing of the attraction forces between the adsorbent and adsorbate. 3.7.5. Effect of agitation rate Indeed, the agitation speed plays a focal role in the adsorption process, since it controls the extent of adsorbent/adsorbate contact. Agitation rate was studied over the range 25 - 200 rpm.

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The results presented in Fig. 7e clarified that the percent removal increased from 75.2 to 91.5 %

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as the rate increases from 25 to 100 rpm. Factually, higher agitation rate gives a magnificent

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chance to the adsorption particles to be greatly distributed and receive a significant number of dye molecules, at which enormous numbers of activated sites become ready to have more CV

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dye. However, the desorption process was befallen with a further increase in the speed up to 200

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rpm owing to the distortion of the stable film at higher agitation speeds.

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3.7.6. Effect of contact time and adsorption kinetics

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Impact of the initial adsorption time on the removal process of CV dye was studied as presented in Fig. 8a. It is evident that a supreme enhancement in the removal rate was achieved

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with increasing the contact time from 5 to 120 min. The removal (%) value was increased from 10.23% to 91.5% and the adsorption capacity was augmented from 5.11 to 45.7 mg/g. These results could be elucidated by the improvement in the diffusion rate of CV dye molecules through the film fluid around the adsorbent with increasing the adsorption time, since more unoccupied adsorption sites are available to adsorb the cationic CV molecules. Nevertheless, further increase of contact time up 120 to 240 min has no noticeable effect on the adsorption process owing to saturation of all adsorption sites with CV dye molecules. As a result, 120 min was designated as an optimal contact time for further adsorption studies.

Journal Pre-proof The adsorption procedure could be expressed using several models of kinetics comprising pseudo-first order, pseudo-second order and intraparticle diffusion models to illustrate the reaction pathways. i.

The pseudo-first order model could be explained as follows [43] : (4)

𝑙𝑛(𝑞𝑒 − 𝑞) = 𝑙𝑛 𝑞𝑒 − 𝑘1 𝑡

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Where, qe and q refer to the adsorbed quantity of CV dye at equilibrium and at time t (mg/g),

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respectively and k1 refers to rate constant at equilibrium (min-1). Plotting ln (qe – q) versus t

The pseudo-second order model could be investigated according to the following equation

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ii.

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provides the actual qe and k1 values from the intercept as well as the slope as presented in Fig. 8b.

𝑡

1 2 2 𝑞𝑒

+

1 𝑞𝑒

(5)

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=𝑘 𝑞

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[44]:

Where, k2 refers to the pseudo-second order rate constant (g/mol.min), and by plotting t/q against t

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the real values of qe and k2 can be determined from the slope and intercept, respectively. The

ℎ = 𝑘2 𝑞𝑒2

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initial uptake rate (h) can be described as the following: (6)

The kinetic rate constant as well as the adsorption capacity at equilibrium could be obtained from the linear plot of t/qt vs t as represented in Fig.8c. Also, the rate constant and correlation coefficient values were illustrated in Table 3. The best fit kinetic model is designated according to the linear reversion determination coefficient (R2) values. It is apparent from the kinetics results that the more applicable model in the adsorption process of CV dye was the pseudo second-order kinetic model. Besides, values of R2 are near to unity and exceeding those given from the pseudo-

Journal Pre-proof first order model. Further, the obtained qe,cal values from the pseudo-second order model are agreed reasonably with the achieved values from the experiments (i.e. qe,exp). Furthermore, h values were increased from 0.59 to 2.86 mg/g.min with increasing the CV dye concentration from 25 to 200 mg/L (Table 3). This performance can be explained by increasing the possibility of collisions between adsorbate and adsorbent with increasing CV dye concentration, and as a result,

Intraparticle diffusion model can be described as follows [47]: (7)

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𝑞𝑡 = 𝑘𝑝 𝑡 0.5 + 𝐶

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more dye molecules could be attached on the surface of the microbeads [45, 46].

Where, qt represents the quantity of adsorbed CV dye at time t, kp (mg g-1 min-0.5) signifies the

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of the equation with plotting qt against t0.5.

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constant of the intraparticle diffusion rate and C refers to the constant obtained from the intercept

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There are three different stages organized the adsorption of CV dye molecules, as shown in Fig. 8d; the first is the rapid exterior surface adsorption, while the second stage is the gradual

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adsorption. The third stage involves the equilibrium step as a result of the lower dye

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concentration in the liquid phase in addition to the lack in the available active sites. Table 3 recorded the intraparticle diffusion parameters, kp and C in addition to the regression determination coefficient, R2. It was perceived that R2 values were high; suggesting that the intraparticle diffusion model can follows the adsorption process. All the plots did not pass through the origin despite a linear relationship owing to the present difference in the mass transfer rate between the initial and last adsorption stages. Besides, the non-zero intercepts of these plots clarified that the intraparticle diffusion was not the individual rate-controlling step in the adsorption process of CV dye by the developed adsorbent microbeads [48].

Journal Pre-proof 3.7.7. Effect of CV dye concentration and adsorption isotherms Batch adsorption experiments were conducted to evaluate the impact of CV dye concentration on the adsorption process, using 25, 50, 100, 150 and 200 mg/ L of CV with fixing all other conditions. Fig. 9a demonstrated that the adsorption capacity was meaningfully increased from 24.9 to 105.7 mg/g with increasing dye concentration from 25 to 200 mg/ L. At

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lower CV concentrations, the vacant adsorption spots do not reach the saturation stage. In contrast, these spots are progressively filled with raising CV dye concentration in the adsorption

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medium. Also, increasing the adsorption capacity with higher CV concentrations could be

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attributed to the resultant driving forces, which in turn able to overcome the barrier between the

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dye solution and the adsorbent phases. Besides, complete dye removal (100%) was obtained with

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the lowest CV concentration (i.e. 25 mg/ L,) since the microbeads adsorbent dose exceeded that of the CV cations. Conversely, the removal (%) values decreased gradually with increasing the

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initial CV concentration up to 200 mg/L owing to the limited number of the entire adsorption

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sites. These results are agreed with other reported studies [49].

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Adsorption isotherms are considered the most advantageous techniques to illustrate the reaction between the adsorbent and adsorbate. Although the equilibrium data could be analyzed using various models, the most common models are Langmuir and Freundlich relationships [50]. To investigate the adsorption isotherms, 0.05 g of IDA@CMC-PBQ microbeads was soaked in 50 mL of CV dye (25-200 mg/L). Langmuir states that the active adsorbent surface has the affinity to adsorb one molecule forming a monolayer of adsorbate [51] and can be demonstrated from the following equation:

Journal Pre-proof 𝐶𝑒⁄ 𝐶𝑒 1 𝑞𝑒 = ⁄𝐵𝑞𝑚𝑎𝑥 + ⁄𝑞𝑚𝑎𝑥

(8)

Where, Ce represents the CV dye concentration at equilibrium (mg/L), qe refers to the adsorbed amount of CV dye at equilibrium (mg/g), qmax denotes the ultimate adsorption capacity (mg/g), and b represents the constant of Langmuir isotherm.

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Langmuir parameters were investigated from the linear plot of Ce/qe against Ce (Fig. 9b), and their values were shown in Table 4. The results indicated that the adsorption process resembles a

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saturated monolayer of CV dye over the surface of adsorbent microbeads with a fixed energy,

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while there is no transmission of CV molecules in the plane of the adsorbent surface [52].

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Additionally, the higher adsorption capacity value (i.e. 107.5 mg/g) indicated the strong attraction

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forces between cationic CV dye and anionic IDA@CMC-PBQ adsorbent sites. Based on the determination coefficient value (R2 = 0.97), the equilibrium adsorption data agreed-well with the

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Langmuir isotherm, which proves that the monolayer coverage of CV dye exists on the outer

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surface of IDA@CMC-PBQ microbeads. Moreover, the adsorption process befalls consistently at the reactive part of the adsorbent surface [53]. Besides, a homogeneous adsorption process

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occurred rather than the heterogeneous adsorption [54] and played a substantial role in the adsorption of CV dye molecules over surface or pores of the IDA@CMC-PBQ microbeads. The

Freundlich isotherm is a reasonable model to characterize the surface

heterogeneousness [2] using the following equation:

𝑙𝑛𝑞𝑒 =

1 𝑙𝑛𝐶𝑒 + 𝑙𝑛𝐾𝑓 𝑛

(9)

Where, Kf refers to the Freundlich constant, while n is the indicator of heterogeneousness [55].

Journal Pre-proof These parameters are calculated from plotting ln qe against ln Ce as presented in Fig. 9c and denoted in Table 4. The little value of 1/n specifies the intense attraction between CV molecules and the surface of the microbeads [56] and shows a normal Freundlich isotherm. Besides, R2 values were exceedingly close to 1 (i.e. 0.99), while the Langmuir model offered better correlation (i.e. 0.97). The observed results suggested that the heterogeneous surface, conditions in addition to the monolayer adsorption, can occur under the selected batch adsorption conditions. Moreover, the

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Langmuir coefficient recorded a sufficient value of 0.157 and demonstrated that CV dye +

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IDA@CMC-PBQ ⇌ [IDA@CMC-PBQ-CV complex] is shifted mostly towards the right leading

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to adsorb the CV dye over the adsorbent surface [57]. Therefore, the fabricated IDA@CMC-PBQ

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microbeads have respectable applicability for the adsorption of cationic CV dye molecules from

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the industrial wastewater.

3.7.8. Evaluation of adsorbent reusability

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Capability of the adsorbent to be regenerated and reused for several times is a substantial

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economic factor, since it controls the cost of production. Herein, the dye-adsorbed microbeads

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were regenerated, since the surface of IDA@CMC-PBQ microbeads became hydrogenated. As a result, the instant attraction between the adsorbent surface and cationic CV dye molecules is destroyed. Fig. 10a demonstrated that the as-fabricated IDA@CMC-PBQ adsorbent microbeads possess a high adsorption power, where the dye removal (%) still exceeded 65% after five consecutive cycles. The gained results prove the aptitude of the developed functionalized microbeads as an efficient and reusable adsorbent for the CV dye removal. 3.7.9. Adsorption performance with other dyes

Journal Pre-proof The as-fabricated adsorbent was evaluated its capability for the adsorptive removal of other tested dyes namely; cationic methylene blue (MB) and anionic methyl orange (MO) dyes as investigated in Fig. 10 b. The results clarified that the developed adsorbent has a great potency for the removal of cationic CV and MB dyes compared to anionic MO dye. Where, maximum removal (%) were 91.5 and 84.4% and recorded after 120 min with maximum adsorption capacity reached 45.7 and 41.9 mg/g for CV and MB dyes, respectively, while MO dye recorded

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only 13.2 % as a maximum removal percent with a maximum adsorption capacity value reached

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8.8 mg/g. These results could be ascribed to the difference in the charge type between the

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adsorbent and adsorbate. The negatively charged adsorption sites on the surface of IDA@CMC-

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PBQ can easily interact with the positively charged CV and MB dye molecules via electrostatic attractions. Thus, the developed functionalized adsorbent could be applied efficiently for

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4. Conclusion

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removing of cationic dyes from their aqueous solutions.

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In summary, a new adsorbent based on surface functionalization of CMC microbeads with IDA molecules was fabricated for the adsorptive removal of cationic crystal violet (CV) dye. The

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developed microbeads were well-characterized using varies characterization tools. Various parameters affecting the adsorption process, including contact time, IDA conc., adsorbent dose, pH, temperature and shaking rate were optimized. The results clarified that the functionalized adsorbent microbeads exhibited much higher adsorption ability compared with the native CMC microbeads. Data obtained from the isotherms study were well-fitted both Langmuir and Freundlich models and followed the pseudo-second order kinetic model. Further, the reusability study indicated that IDA@CMC-PBQ adsorbent microbeads still kept decent adsorption

Journal Pre-proof properties after five consecutive cycles. Therefore, the functionalized microbeads could be used as an efficient and reusable adsorbent for cationic dyes removal from their aqueous solutions. Acknowledgement This work has been partially supported by chemicals and analysis from the Science and Technology Development Fund - Basic & Applied Research Grants (STDF-BARG)- No. 25984;

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Ministry of Scientific Research; Egypt. References

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for removal heavy metal ions, J. Appl. Polym. Sci. 119 (2011) 1204-1210. [39] M.S. MohyEldin, M.A. Elmageed, A. Omer, T. Tamer, M. Yossuf, R. Khalifa, Development of Novel Phosphorylated Cellulose Acetate Polyelectrolyte Membranes for Direct Methanol Fuel Cell Application, Int. J. Electrochem. Sci 11 (2016) 2. [40] M.S. MohyEldin, A.M. Omer, T.M. Tamer, M.A. Elmageed, M.E. Youssef, R.E. Khalifa, Novel Aminated Cellulose Acetate Membranes for Direct Methanol Fuel Cells (DMFCs), Int. J. Electrochem. Sci 12 (2017) 4301-4318. [41] M. Khader, M. Al-Marri, S. Ali, G. Qi, E. Giannelis, Adsorption of CO2 on polyethyleneimine 10k—mesoporous silica sorbent: XPS and TGA studies, Am. J. Anal. Chem. 6 (2015) 274.

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Figures captions Fig. 1. Digital laboratory images of CMC and IDA@CMC-PBQ adsorbent microbeads and images before and after the CV dye adsorption. Fig. 2. The proposed mechanism of activation and functionalization steps for the preparation of IDA@CMC-PBQ microbeads. Fig. 3. IEC and zeta potential values of CMC and IDA@CMC-PBQ functionalized microbeads.

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Fig. 4. (a) FT-IR spectra and (b) TGA curves of CMC, CMC-PBQ and IDA@CMC-PBQ

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microbeads.

microbeads at different magnifications.

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Fig. 5. SEM images of (a, b) CMC microbeads, (c, d) CMC-PBQ and (e, f) IDA@CMC-PBQ

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Fig. 6. XPS of IDA@CMC-PBQ microbeads (a) wide scan spectrum and (b, c) N1s before and

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after adsorption of CV dye.

Fig. 7. Effect of (a) IDA concentration, (b) pH medium, (c) adsorbent dose, (d) temperature and

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(e) agitation rate on the adsorption process. Fig. 8. (a) Effect of initial contact time on the adsorption process, (b) Pseudo-first order, (c)

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Pseudo-second order kinetic models and (d) intraparticle diffusion model for the adsorption

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of CV dye by IDA@CMC-PBQ microbeads. Fig. 9. (a) Effect of initial CV dye concentration on the adsorption process, (b) Langmuir and (c) Freundlich isotherm models for the adsorption of CV dye by IDA@CMC-PBQ microbeads. Fig. 10. (a) Reusability of IDA@CMC-PBQ adsorbent microbeads and (b) adsorption performance of IDA@CMC-PBQ microbeads for removing of CV, MB and MO dyes

Journal Pre-proof Table1 The characteristics of cationic CV dye. Chemical formula

Chemical structure

M.wt. (g/mol)

407.99

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na

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C25H30N3Cl

λmax (nm)

590

Journal Pre-proof Table 2 TGA data of T50% (oC) for CMC, CMC-PBQ and IDA@CMC-PBQ microbeads. CMC

CMC-PBQ

IDA@CMC-PBQ

T50% (oC)

342

331

328

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Sample

Journal Pre-proof Table 3 The pseudo-first order, pseudo-second order and intraparticle diffusion models parameters for the adsorption of the CV dye onto IDA@CMC-PBQ microbeads.

R2

(mg/L)

pseudo-second order R2

k1

qe,cal

(min-1)

(mg/g)

k2

h

qe,cal

qe,exp

(g/mg min)

(mg/g min)

(mg/g)

(mg/g)

0.599

0.96

0.029

9.205

0.97

0.00057

50

0.98

0.018

10.11

0.99

0.00044

100

0.95

0.016

11.39

0.97

0.00021

150

0.97

0.017

12.07

0.97

0.00016

200

0.94

0.018

12.54

0.96

0.00016

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Intraparticle diffusion R2

kP

c

(mg.g1 min-1/2)

(mg. g-1)

32.36

24.98

0.87

1.85

1.08

1.347

55.25

45.78

0.90

3.53

0.85

1.849

94.34

71.67

0.95

5.31

3.16

2.336

120.48

90.87

0.93

7.54

7.07

2.859

133.33

105.76

0.94

6.77

3.96

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25

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q

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CV dye

pseudo-first order

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Kinetic model

Journal Pre-proof Table 4 Parameters and correlation coefficients of Langmuir and Freundlich models for the adsorption of CV dye by IDA@CMC-PBQ microbeads. Langmuir

Freundlich

B(L/mg)

qmax (mg/g)

R2

KF (mg/g)

1/n

0.97

0.157

107.52

0.99

0.723

0.266

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na

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R2

Journal Pre-proof

Author Statement Regarding the manuscript "Ref: IJBIOMAC_2019_8549, Title: Fabrication of novel iminodiacetic acid-functionalized carboxymethyl cellulose microbeads for efficient removal of cationic

crystal

violet

dye

from

aqueous

solutions

Journal: International Journal of Biological Macromolecules. -All authors read the manuscript and approved the contents. -This manuscript has not been published or presented elsewhere in part or in entirety and is not

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under consideration by another journal. We have read and understood your journal’s Guide for

-There are no conflicts of interest to declare.

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Authors, and we believe that neither the manuscript nor the study violates any of these.

-Authors contribution: Ahmed M. Omer proposed the research concept and manuscript writing.

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Gehad S. Elgarhy conducted the experiments. Gehan M. El-Subruiti participated in manuscript

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preparation and revision, Randa E. Khalifa participated in the data interpretation and manuscript

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editing. Abdelazeem S. Eltaweil participated in manuscript writing and revision.

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Sincerely,

Jo

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Ahmed. M. Omer Assoc. Professor Polymeric Materials Research Department, Advanced Technologies, and New Materials Research Institute (ATNMRI), City of Scientific Research and Technological Applications (SRTA-City), New Borg El-Arab City, P.O. Box, 21934, Alexandria, Egypt. E–mail: [email protected]

Journal Pre-proof

Graphical Abstract

Highlights Functionalized microbeads based on carboxymethyl cellulose were developed



Batch adsorption experiments were conducted for CV dye removal



Results were verified by classical kinetics and isotherm studies



The fabricated microbeads showed efficient adsorption with good reusability

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

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10