Efficient and highly selective adsorption of cationic dyes and removal of ciprofloxacin antibiotic by surface modified nickel sulfide nanomaterials: Kinetics, isotherm and adsorption mechanism

Journal Pre-proof Efficient and highly selective adsorption of cationic dyes and removal of ciprofloxacin antibiotic by surface modified nickel sulfide nanomaterials: Kinetics, isotherm and adsorption mechanism Sunita Kumari, Afaq Ahmad Khan, Arif Chowdhury, Arvind K. Bhakta, Zineb Mekhalif, Sahid Hussain

PII:

S0927-7757(19)31259-2

DOI:

https://doi.org/10.1016/j.colsurfa.2019.124264

Reference:

COLSUA 124264

To appear in:

Colloids and Surfaces A: Physicochemical and Engineering Aspects

Received Date:

30 September 2019

Revised Date:

20 November 2019

Accepted Date:

21 November 2019

Please cite this article as: Kumari S, Khan AA, Chowdhury A, Bhakta AK, Mekhalif Z, Hussain S, Efficient and highly selective adsorption of cationic dyes and removal of ciprofloxacin antibiotic by surface modified nickel sulfide nanomaterials: Kinetics, isotherm and adsorption mechanism, Colloids and Surfaces A: Physicochemical and Engineering Aspects (2019), doi: https://doi.org/10.1016/j.colsurfa.2019.124264

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Efficient and highly selective adsorption of cationic dyes and removal of ciprofloxacin antibiotic by surface modified nickel sulfide nanomaterials: Kinetics, isotherm and adsorption mechanism

Sunita Kumari,a Afaq Ahmad Khan,a Arif Chowdhury,a Arvind K. Bhakta,b Zineb Mekhalifb and Sahid Hussain*,a

Department of Chemistry, Indian Institute of Technology Patna, Bihta-801106, Bihar, India.

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a

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Laboratory of Chemistry and Electrochemistry of Surfaces, NISM, University of Namur, 61 Rue de Bruxelles, 5000 Namur, Belgium

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* Corresponding author

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Sahid Hussain, E-mail: [email protected]; Fax: +91-612-227-7383; Tel: +91-612-302-8022

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Graphical Abstract

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Highlights Developed surface functionalized nickel sulfide nanomaterial as an adsorbent.



Adsorption of ciprofloxacin antibiotic and selective adsorption of cationic dyes.



High adsorption capacity for methylene blue, crystal violet and ciprofloxacin.



The adsorption mechanism is predominantly electrostatic.



The adsorbent is eco-friendly and reusable.

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

Abstract

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In the present work, the nickel sulfide nanomaterial with the negative surface charge was synthesized by a simple and eco-friendly route using nickel acetate, thioacetamide and L-

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glutathione reduced (GSH). The new surface-modified nanomaterial was systematically characterized using various techniques such as XRD, FE-SEM, TEM, EDX, XPS, TGA, Zeta-

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potential, and FT-IR, and then applied for the removal of dyes and antibiotics. The nanomaterial exhibited selective adsorption towards cationic dyes: methylene blue (MB) and crystal violet

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(CV) with a high adsorption capacity of 1006.52 mg g-1 and 1946.61 mg g-1, respectively. The adsorption capacity for the removal of ciprofloxacin antibiotic (CIP) was 971.83 mg g-1 which is extremely high. The selectivity of MB in binary mixtures was investigated using two anionic

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dyes: methyl orange (MO) and orange G (OG). The separation efficiency (α) for MB in MB/MO and MB/OG mixtures was 97.75 % and 99.16 %, respectively. The adsorption process for all the adsorbates followed pseudo-second-order kinetics and the Freundlich isotherm model. The mechanism of interaction was analyzed through pH effect, zeta-potential measurement, FT-IR and XPS analysis, implying that the electrostatic interaction is mainly involved in the adsorption.

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In addition, the parameters like the effect of initial dye concentration and temperature on the adsorption process were studied. The adsorbent is reusable up to 4 times with 97 % efficiency. Thus, the prepared GSH-capped nanomaterial is an effective adsorbent for the removal of antibiotics and the selective removal of cationic dyes with high adsorption capacity.

Keywords: Nickel sulfide; Adsorption; Dyes; Ciprofloxacin; Isotherms; Kinetics. 2

1. Introduction In today’s scenario, the treatment of major water pollutants like dyes, heavy metals, and drugs have been a key environmental concern among the scientific community as the quality of drinking water resources across the world is declining severely [1,2]. There are various industries such as textile, ink, plastics, cosmetics, paint, and varnishes which release dyes to water resources. Toxic, carcinogenic and mutagenic nature of dyes has lethal effects on the ecosystem

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[1,3]. Methylene blue (MB) and Crystal Violet (CV) are cationic dyes and have wide applications in biology, chemistry, and industries like printing and dyeing cotton [4,5]. Exposure

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to MB can cause tissue necrosis, jaundice, vomiting and cyanosis in human beings [6]. The CV is a proved carcinogen and is toxic to human beings causing eye irritation, respiratory problems,

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diarrhea, and headache[5]. The effluents from the pharmaceutical industry also have detrimental effects on the environment [7]. Ciprofloxacin (CIP) is an antibiotic, belongs to the class of

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fluoroquinolones which are widely used as antibacterial agents in humans and animals. Potential migration of CIP into the environment can lead to antibiotic resistance (ABR) via gene transfer

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within bacteria. The evolved antibiotic resistance genes in bacteria pose an enormous harmful impact on public health and challenges for environmental scientists [8,9]. Several natural and synthetic adsorbents such as activated carbon [10], cashew nut shell [11], graphene oxide [12],

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Co4S3 [13], ZnS nanotubes [14], CNTs/Zn:ZnO@Ni2P-NCs [15], Mn-doped CuO ‐ NPs ‐ AC [16] and Ni-Co-S/SDS nanocomposites [17] etc., have been used for the removal of organic pollutants from wastewater. However, the total removal of organic dye pollutants is not always preferred because some of the valuable dyes need to be recycled for their reuse [18,19]. Dye effluents are mainly a complex mixture of different dyes that lead to difficulty in separation and

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its reuse. Hence, the selective adsorption of a specific type of adsorbates and separation has been a very interesting and challenging task in water treatment. Recently, various adsorbents with selective adsorption properties have been reported such as hexagonal boron nitride [20], Ag7 (DMSA)4 [21], MOP-1 [22], Zn-MOF [23] and silica nanoparticle [24], etc. Nevertheless, they face limitations like low adsorption capacity and low separation efficiency. Therefore, endeavors to make new adsorbents with better adsorption capacity, regeneration ability and high selectivity towards dye removal are underway. 3

Nanomaterials have received momentous attention due to their different physico-chemical properties like the surface area to volume ratio, chemical reactivity, optical and electronic behavior from that of bulk materials [25–27]. The composition, size, and shape of a nanomaterial greatly depend on the synthetic methods [28,29]. The adsorption properties of a nanomaterial can be altered by the stoichiometric ratio of reactants, reaction temperature, capping agents/surfactants and pH of the reaction [13,30–33]. Nowadays, nickel sulfide materials are

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well-known and have attracted a lot of attention due to diverse applications in fields like supercapacitors [34], lithium-ion batteries [35], photocatalysts [30], dye-sensitized solar cells

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[36] and adsorption [37]. The composition of nickel sulfide is highly dependent on reaction temperature, time, reagent amount and pH which leads to the formation of different phases like

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α–NiS, β-NiS, NiS2, Ni3S4, Ni3S2, Ni7S6, and Ni9S8 [38–40]. Nickel sulfide materials have also been applied in water treatment owing to their good affinity towards dyes [37,41] but the

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selective adsorption property towards dyes and antibiotics are very less explored. Selective adsorption of adsorbates on nanomaterials can occur in different ways such as through electrostatic interaction, hydrogen bonding, surface/pore diffusion, coordination effect and

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hydrophobic interaction [42–45]. Moreover, the modification of surface charge can be done with the aid of functional groups on the surface to get the selective adsorption of a particular type of

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dyes. The L-glutathione (GSH) is a tripeptide composed of glutamic acid, cysteine and glycine units and contains a reactive thiol (-SH) group [46]. It is environmentally benign in nature and has different functional groups i.e., amine (-NH2) and two carboxylate (-COO-) groups. Hence, GSH can be used to provide the negative surface charge on the nickel sulfide surface for the selective adsorption of cationic adsorbates.

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Herein, we have elucidated the synthesis of nickel sulfide nanomaterials (NMs) using

nickel acetate tetrahydrate as the metal precursor, thioacetamide as the sulfur source and Lglutathione as the capping agent using facile precipitation method at 90 °C. The designed protocol for the nickel sulfide nanomaterials is very simple and did not required any typical setup, high temperature and inert atmosphere (Ar or N2). The synthetic strategy led to the negatively charged surface of the nickel sulfide, which enabled the electrostatic interaction between the adsorbent and positively charged adsorbates. The as-synthesized nanomaterial 4

exhibited high selectivity and high adsorption capacity towards cationic dyes: MB and CV, and the antibiotic CIP. The selective adsorption towards cationic adsorbates by surface modified nickel sulfide nanomaterial with L-glutathione (GSH) has been investigated for the first time. The adsorption isotherm and kinetics were performed to understand the interaction of adsorbate with the adsorbent. Further, the effect of pH, zeta potential measurement, FTIR study and XPS were also done to establish the mechanism of adsorption. The recyclability of the adsorbent was

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tested in order to accomplish sustainable applications.

2. Experimental section

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2.1. Materials

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All the chemicals are of analytical grade or higher purity and were used without further purification. All the aqueous solutions were made using ultra-pure water. Nickel (II) acetate

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tetrahydrate [C4H6NiO4.4H2O], rhodamine B, orange G, thioacetamide [C2H5NS] and ethanol were purchased from Sigma-Aldrich. Methylene blue and methyl orange were bought from Alfa aesar. Crystal violet and Glutathione reduced forms were purchased from CDH and TCI

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Chemicals, respectively. Ciprofloxacin hydrochloride was purchased from HIMEDIA. 2.2. Synthesis of nickel sulfide Nanomaterials

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Firstly, a 20 mL aqueous mixture of nickel (II) acetate tetrahydrate (2 mmol) and varied amounts of glutathione (in the range of 0.1 to 0.5 mmol) were magnetically stirred in a round bottom flask at the room temperature for 30 minutes. The obtained brown colored aqueous mixture was placed in a silicone oil bath maintained at 90 °C. Afterward, 4 mmol thioacetamide solution

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(TAA) was added dropwise to the above mixture and then stirred for 4 hours. This resulted in a black colored precipitate that was centrifuged and washed several times using a mixture of ethanol and distilled water followed by drying under vacuum. The synthesized samples with 0.1, 0.2, 0.3, 0.4, and 0.5 mmol of GSH were labeled as NS-0, NS-1, NS-2, NS-3, NS-4, and NS-5, respectively. Details of the synthesis of different samples are mentioned in Table S1†. 2.3. Characterizations

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Field emission scanning electron microscopy (FESEM) was done using the GeminiSEM 500 operating at 20 kV at a working distance of 3.3 mm. This instrument was equipped with energydispersive X-ray spectroscopy (EDX). Transmission electron microscopy (TEM) analysis was carried out using a JEOL TEM 200 instrument operating at 200 kV accelerating voltage. X-ray powder diffraction (P-XRD) study was carried out using a Rigaku X-ray diff ractometer at an operating voltage of 10 kV with Cu K α radiation ( λ = 1.54 18 Å ) in the 2 θ range of 10°−80°. The X-ray photoelectron spectroscopy (XPS) spectra were recorded using the Thermo Scientific

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K-Alpha spectrometer through monochromatized Al Kα radiation (1486.6 eV) and a hemispherical analyzer. The composition analysis of all the XPS spectra was done using Avantage software. Thermogravimetric analysis (TGA) was conducted using SDT Q600

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instrument at 10 °C/min heating rate under N2 atmosphere. Brunauer-Emmett-Teller (BET) surface area, pore size, and pore volume analyses were carried out using a Quantachrome

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autosorb iQ2 analyzer. UV-vis spectra were recorded using a UV-vis spectrophotometer (Shimadzu UV2500) in the wavelength range of 200-800 nm. Fourier- transform infrared

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spectroscopy (FTIR) studies were obtained in KBr pellets mode using a Perkin Elmer spectrum

2.4. Adsorption test

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400 FT-IR spectrophotometer.

The adsorption experiments were carried out using cationic dyes i.e., MB, CV, rhodamine B

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(RhB), and anionic dyes, i.e., methyl orange (MO) and orange G (OG) as model organic dye pollutants of the water at neutral pH. After the adsorption, the supernatant was analyzed by taking its UV- Vis absorption spectra (diluted to 5 mg L-1) of the adsorbate solutions at maximum wavelength of absorption. The maximum wavelength of absorption for MB, CV, RhB, MO, OG, and CIP are 664 nm, 579 nm, 553 nm, 464 nm, 479 nm, and 275 nm, respectively

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(Table S2†). The desired pH value of the adsorption medium was achieved by the use of 0.1 M HCl and 0.1 M NaOH solutions through a check using pH meter.

2.4.1. Preparation of solutions for adsorption isotherm study The determination of the maximum adsorption capacity of the adsorbents was done by dispersing 5 mg of adsorbent to 14 mL of different concentrations of dyes and 15 mL of CIP with 6

continuous stirring for 24 hours. The pH of the 1000 mg L-1 stock solution of ciprofloxacin hydrochloride was 4.5 and this solution is diluted to different concentrations using distilled water for adsorption experiments. 2.4.2. Preparation of solutions for the study of adsorption kinetics The kinetic experiments were performed by adding 5 mg of adsorbent to 20 mL of dyes (20 mg L-1) and 15 mL of 50 mg L-1 for CIP. For comparing the adsorption efficiency of different dyes,

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the adsorption test was done by stirring 20 ppm dye using 5 mg of NS-4 for 150 minutes. 2.4.3 Preparation of solution for adsorption analysis in the mixture of dyes

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Further, in order to analyze the selective removal of dyes, the adsorption tests were carried out using MB/MO mixture and MB/OG mixture (20 mL mixture containing 20 mg L-1 each dye). In

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addition, separation studies were also done with a 15 mL solution containing 10 mg L-1 each of

tested with 5 mg of the adsorbent.

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2.4.4 Calculation of adsorption parameters

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RhB and MO. A 15 mL ternary solution (10 mg L-1 each dye) of MB, RhB, and MO were also

The amount of adsorbate, adsorbed on the nickel sulfide NMs is expressed as adsorption capacity. The adsorption efficiency and adsorption capacity (qe) are calculated using the

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following equations, respectively:

Adsorption efficiency (%) =

C 0 − Ce

q e (mg g −1 ) =

C0 C0 −Ce M

× 100

(1)

× V

(2)

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Where, C0 and Ce are the initial and equilibrium concentration of adsorbate, respectively, M is the mass of dried adsorbent in grams and V is the volume of solution in liters. The separation efficiency (α) for the mixture of dyes can be evaluated using the following equations: α(%) =

C(anionic dye)t C(anionic dye)t +C(cationic dye)t

× 100

(3)

Where C(anionic dye)t and C(cationic dye)t are the concentrations of anionic and cationic dyes remain in the solution after the adsorption.[47,48] 7

2.5. Statistical error analysis of the isotherm and kinetic models data In order to find the best fit models for isotherm and kinetics experimental data, three statistical models were considered: the sum of square error (SSE), chi-square test (χ2) and coefficient of determination (R2). A better agreement between calculated and experimental data is determined from a considerably low value of SSE and χ2 and highest R2. The SSE and χ2 are evaluated using equations 4 and 5, respectively [49]. n

(q e,exp − q e,cal )

2

(4)

χ2 = ∑ni=1

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i=1

2

(qe,exp −qe,cal ) qe,cal

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SSE = ∑

(5)

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Where, qe,cal and qe,exp are the amount of adsorbed adsorbate obtained from calculated values

3. Results and discussion

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3.1. Structural and chemical properties

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from the model equation and experiment values at equilibrium, respectively.

The characteristic XRD patterns of NS-0 and NS-4 are shown in Fig. 1a. The X-ray diffractions peaks of NS-0 are observed at 2θ value 30.4, 34.8, 46.2, 53.9 and 73.4 that can be indexed to

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(100), (101), (102), (110) and (202) planes of the hexagonal phase of NiS (JCPDS No. 75-0613), respectively. The broad peaks are observed in NS-1, NS-2, NS-3, NS-4, and NS-5 suggesting the small size and poorly crystalline nature of the sample as shown in Fig. 1b. It can be manifested that the use of glutathione for the synthesis of nickel sulfide adsorbents caused a decrease in the

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crystallinity of the nickel sulfide NMs.

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(b)

(a) Intensity (a.u.)

NS-4

Intensity (a.u.)

(100) (102) (110) (101)

NS-0 (202)

NS-5 NS-3

NS-2

JCPDS No. 75-0613 20

30

40

50

2 (degree)

60

70

10

80

20

30

40

50

60

70

80

2 (degree)

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NS-1

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Fig. 1. Powder X-ray diffraction patterns of (a) NS-0 and NS-4 and (b) NS-1, NS-2, NS-3, and NS-5.

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XPS measurements were carried out for determining the chemical composition and chemical state of the elements present in the sample. The survey scan and high-resolution spectra

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of C 1s, Ni 2p, S 2p, O1s, and N 1s are shown in Fig. 2. The anchoring of GSH on the surface of nickel sulfide NMs (NS-4) was confirmed from the core level spectrum of C1s. The fittings of

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the C1s spectrum showed three components. The peak observed at 284.70 eV can be assigned to C−C and C−H. The peak observed at 285.62 eV corresponds to C−N and C−S and the other peak at 288.08 eV indicates the O−C=O group. The oxygen spectrum showed two components at

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531.89 and 532.69 eV which correspond to the C=O and O−C=O group of GSH, respectively (Fig. 2e) [50]. The best fits of the Ni 2p spectrum showed two spin-orbit doublets that are Ni 2p3/2 and Ni 2p1/2 (Fig. 2c). It also showed two shake-up satellites (sat) at 860.84 eV and 878.64 eV. The component 2p3/2 shows characteristics peaks for Ni2+ and Ni3+ at binding energies 853.62 eV and 856.18 eV. The component Ni 2p1/2 also showed two peaks at 870.87 eV and

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873.99 eV for Ni2+ and Ni3+, respectively [51,52]. The spin-orbit splitting value of 17.25 for Ni2+ suggesting the formation of metal sulfide. The deconvolution of the S 2p spectrum consists of two peaks which are attributed to 2p3/2 and 2p1/2 present at binding energies 162.40 and 163.7 eV, respectively which are typically for metal sulfides (Fig. 2d). It also exhibits one shake-up satellite peak [53,54]. The fitting of N 1s spectra NS-4 exhibited two components that can be assigned to NH and +NH3 at binding energy values of 399.98 eV and 401.94 eV (Fig. 2f).

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Ni 2p1/2 Ni 2p3/2 O KLL

O 1s

(b)

S 2p

750

600

450

300

O-C=O

294

150

292

(c)

(d)

S 2p

865

860

855

850

845

174

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870

Binding Energy (eV)

(e)

O-C=O

540

537

534

531

2p 3/2

528

(f)

168

165

162

159

-NH (399.98 eV)

N 1s

+ NH3 (401.94 eV)

408

525

171

Binding Energy (eV)

Intensity (a.u.)

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C=O

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Intensity (a.u.)

O 1s

280

sat

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sat

sat

875

282

-p

3+ Ni

2p1/2

880

284

2p1/2

Intensity (a.u.)

Intensity (a.u.)

2p3/2 Ni2+

2+ Ni

286

Binding Energy (eV)

Ni 2p

3+ Ni

288

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Binding Energy (eV)

290

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900

C-C

Intensity (a.u.)

C 1s N 1s

1050

C1s C-N, C-S

Ni LMM

Intensity (a.u.)

(a)

405

402

399

396

393

Binding Energy (eV)

Binding Energy (eV)

Fig. 2. XPS spectra of NS-4 (a) survey spectrum and fitting of core-level spectra of (b) C 1s (c) Ni 2p, (d) S 2p, (e) O 1s and (f) N 1s.

3.2. Morphology 10

(c) (c)

(b) (b)

(a)

(e)

(d)

(f)

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(d)

(e)

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(f)

(g )

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(h)

(h)

(i)

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(g)

(i)

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81 nm

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Fig. 3. FE-SEM micrographs of (a) NS-0, (b) NS-1, (c) NS-2, (d) NS-3, (e) NS-4 and (f) NS-5 and; TEM micrographs of (g) NS-4 (inset: TEM micrograph at higher magnification) and (h) NS-4 showing width of a flake and; (i) SAED pattern of NS-4. The FE-SEM images for all the samples are shown in Fig. 3a-e. The SEM micrographs showed aggregated particles with uniform distribution. The mean particles size of adsorbents NS-0, NS1, NS-2, NS-3, NS-4, and NS-5 are found as 125 nm, 130 nm, 120 nm, 97 nm, 86 nm and 83 nm from the FE-SEM micrographs, respectively. TEM analysis was performed for a better 11

understanding of the morphology of NS-4, (Fig. 3g-h). The obtained micrograph displayed flakelike morphology with a width of about 81 nm. Moreover, the broad diffuse rings shown in the selected area electron diffraction (SAED) of NS-4 are in agreement with the broadening of XRD peaks suggesting the amorphous nature of NS-4 (Fig. 3i). EDX spectra show that the NS-4 is composed of Ni, S, C, N and O elements (Fig. S1†). The atomic percentages of different elements for different samples are represented in Table S3†. The homogenous distribution of

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elements is confirmed by EDX mapping (Fig. 4)

Ni

S

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NS-4

C

O

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N

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Fig. 4. EDX mapping analysis of NS-4 (scale bar corresponds to 5 µm).

3.3 Surface area and thermal stability

The surface area plays a key role in adsorption as it leads to more number of active sites to the

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adsorbent. Therefore, the specific surface area and porosity were investigated using N 2 adsorption-desorption isotherms and Barrett-Joyner-Halenda (BJH) pore size distribution (Fig. 5). The specific surface area and pore volume for NS-0 were 11.906 m2/g and 0.019 cm3/g, respectively with a pore diameter of 2.63 nm. However, the NS-4 possesses a specific surface area of 22.458 m2/g and a pore volume of 0.036 cm3/g with a pore width of 2.7 nm. Both the adsorbents exhibited type IV isotherms with the H3 hysteresis loop. The higher surface area of NS-4 than that of NS-0 is in accordance with its increased adsorption capacity.

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12 10

Volume @ STP (cc/g)

14

dV(r) (ccÅg-1)

Volume @ STP (cc/g)

0.0008 0.0006 0.0004 0.0002 0.0000

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-0.0002 0

5

10

15

20

25

30

Pore Width (nm)

6 4 2 0 0.0

0.2

0.4

0.6

0.8

35

0.0014

30 25

0.0012

20

0.0010 0.0008 0.0006 0.0004 0.0002 0.0000 -0.0002 0

5

15

10

15

20

25

30

Pore Width (nm)

10 5 0 0.0

1.0

NS-4

0.0016

0.2

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(b)

NS-0

0.0010

0.4

0.6

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16

dV(r) (ccÅg-1)

(a)

0.8

1.0

Relative Pressure (P/P0)

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Relative pressure (P/P0)

Fig. 5. N2 adsorption-desorption isotherm of (a) NS-0 and (b) NS-4. Inset: Corresponding BJH

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desorption, pore volume vs. pore width curve.

Thermogravimetric analysis of the adsorbents was done to check the thermal stability as shown

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in Fig. 6. The initial weight loss in the range of 100-200 °C is due to adsorbed water. The second weight loss in the range of 220–350°C for adsorbents except NS-0 can be assigned as decomposition of surface-bonded L-glutathione. The decomposition above 500 °C for NS-0

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might be due to the sublimation of metal sulfides. But for other adsorbents sublimation of metal sulfides occurs above 700 °C. Hence, the stability of glutathione-capped nickel sulfide is greater than the uncapped one.

100

Weight (%)

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90

NS-0 NS-1 NS-2 NS-3 NS-4 NS-5

80 70 60 50 40 30

100

200

300

400

500

600

700

800

Temperature (C)

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Fig. 6. TGA of the all the synthesized adsorbents. 3.4 Adsorption tests of dyes and antibiotic on NS-4 3.4.1 Adsorption Isotherm At first, the adsorption isotherm of all the synthesized adsorbents towards MB dye was performed in order to find the best adsorbent. The adsorption behavior of all the synthesized samples towards MB dye is shown in Fig. 7. The best adsorption capacity was shown by the NS-

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4 adsorbent. Therefore, further adsorption studies were done using NS-4. The Langmuir and Freundlich isotherm models with non-linear expression were considered to analyze the

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interaction between the adsorbate molecules and NS-4 using equation 6 and equation 7,

𝑞𝑒 =

𝑞𝑚 𝐾𝐿 𝐶𝑒 1+𝐶𝑒 𝐾𝐿 1/n

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𝑞𝑒 = 𝐾𝐹 𝐶e

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respectively [55,56]:

(6) (7)

Herein, Ce (mg L−1) is the concentration of adsorbate after equilibrium adsorption, qm (mg g-1) is

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the maximum adsorption capacity, qe (mg g-1) is the equilibrium adsorption capacity and KL (L mg-1) is Langmuir equilibrium constant which describes the affinity of adsorbate towards

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adsorbent. KF and 1/n (0<1/n<1) are the Freundlich constant corresponding adsorption capacity and the linearity index, respectively. The Langmuir adsorption isotherm is applicable for monolayer coverage of the homogenous surface. The active sites are independent and can bind to a specific number of adsorbates. The Freundlich isotherm is based on the assumption of multilayer adsorption on the heterogeneous surface. It involves non-ideal and reversible

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adsorption on adsorption sites with an exponential distribution of energy [57,58].

14

1200 1000 NS-0 NS-1 NS-2 NS-3 NS-4 NS-5

-1

qe (mg g )

800 600 400 200 0

200 400 600 800 1000 1200 1400 1600

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0

-1

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Ce (mg L )

Fig. 7. Equilibrium adsorption isotherms of MB with the various synthesized adsorbent.

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The results of the fitting of the Langmuir and Freundlich adsorption model for MB, CV, and CIP are represented in Fig. 8. The coefficient of determination (R2) of the Freundlich model is higher than the Langmuir isotherm model for both dyes and the antibiotic as shown in Table 1. In

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addition, the sum of square error (SSE) and chi-square (χ2) for Freundlich models were also comparatively lower than that of Langmuir models. Based on the statistical parameters, the

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Freundlich adsorption isotherm model is the better-fitted model for adsorption of MB, CV, and CIP suggesting multilayer adsorption of dyes. The higher value of KF and the value of n greater than 1 suggested favorable adsorption. The maximum adsorption capacities (qm) for MB, CV,

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and CIP onto NS-4 through the Langmuir adsorption model were found to be 1006.52 mg g-1, 1946.61 mg g-1, and 971.83mg g-1, respectively which is higher than previously reported

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adsorbents in literature (Table 2).

15

1200

(a)

(b)

MB

1800

1000

1500

Experimental Langmuir Freundlich

600

Experimental Freundlich Langmuir

1200

-1

-1

qe (mg g )

800

qe (mg g )

CV

400 200

900 600 300

0

0 0

250

500

750

1000 1250 1500 1750

0

-p

400 Experimental Langmuir Freundlich

100 25

50

75

100

125 -1

Ce (mg L )

150

175

200

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0

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-1

qe (mg g )

500

200

400

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600

300

300

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(c)

CIP

200

Ce (mg L )

Ce (mg L )

700

100

-1

-1

Jo

NS-4

ur na

Fig. 8. Langmuir and Freundlich adsorption isotherms of (a) MB, (b) CV and (c) CIP on

16

Table 1 Langmuir and Freundlich isotherm parameters for the adsorption of MB, CV and CIP on NS-4 Constants KL (Lmg-1) qm (mg g-1) R L2

CV

CIP

0.0646

0.0164

0.0101

1946.61

971.83

0.8960

0.9739

1006.52

SSE

26315.73

χ2 Freundlich

of

0.9651

533147.60

28.3699

KF ( L mg-1) 1/n

289.24 0.1829

RF2

313.13

re

0.9770

7096.8770

ro

Langmuir

MB

-p

Isotherm models

3645.06 39.5604 37.56

0.2880

0.5457

0.9867

0.9777

3965.57

65610.70

3109.40

χ2

4.3365

54.3470

8.4804

lP

SSE

S.No.

Adsorbent

Adsorbates

Adsorption capacity (mg/g)

References

PCN-222

MB

906

[59]

Jo

1.

ur na

Table 2 Comparision of adsorption capacity of reported adsorbents for the adsorption of MB, CV, and CIP.

2.

h-BN

MB

472.4

[20]

3.

Zn-MOF

MB

326

[23]

4.

MOP-1

MB

719.4

[22]

5.

Porous silica nanoparticle (PCN-500)

MB

290

[24]

6.

MCM-41

CV

138.72

[57]

7.

NMRH

CV

44.87

[60]

17

8.

Magnetic nanocomposite hollow Co3S4

CV CIP

113.31 471.7

9.

[5]

10.

Fe3O4/C

CIP

74.68

[61]

11. 12.

MgO nanoparticles Nickel Sulfide Nanomaterial

CIP

3.46

[62]

MB CV CIP

1006.52 1946.61 971.83

[9]

This work

of

3.4.2. Adsorption Kinetics Other than the concentration, the adsorption process also depends on contact time. It depicts the

ro

rate of uptake of dye molecules and the efficiency of adsorption. So, the effect of contact time on adsorption capacity was studied (Fig. 9). The two well-known models, pseudo-first-order and

-p

pseudo-second-order kinetics were analyzed using equation 8 and equation 9, respectively in order to investigate the mechanism of adsorption. Here, qe and qt are the amounts of adsorbate

re

adsorbed at equilibrium and at different time intervals, respectively. k1 and k2 are the pseudofirst-order and pseudo-second-order constants, respectively [63,64]. The parameters obtained

lP

through fitting plots are shown in Table 3. There is a good agreement between the experimental qe,exp and the calculated qe,cal obtained from the pseudo-second-order model. The coefficient of determination (R2) values for the adsorption of MB, CV and CIP are higher for the pseudo-

ur na

second-order kinetic model. The χ2 and SSE values for the linear fitting plots of pseudo-secondorder kinetics of all the adsorbates were lower than the pseudo-first-order kinetics (Fig. 10). All these results suggested that the adsorption process in the present case followed the pseudosecond-order model.

Jo

ln(𝑞𝑒 − 𝑞𝑡 ) = ln 𝑞𝑒 − 𝑘1 𝑡 𝑡

𝑞𝑡

=

1 𝑘2 𝑞𝑒2

+

𝑡 𝑞𝑒

18

(8) (9)

(a)

(b)

MB

80

120

qt (mg g )

60

90

-1

qt (mg g-1)

CV

150

40

20

60 30 0

0 0

50

100

150

200

250

0

10

t (min)

of

-1

-p

60

qt (mg g )

40

t (min)

(c)

CIP

30

ro

80

20

40

re

20

0

10

20

t (min)

30

lP

0

40

50

ur na

Fig. 9. Effect of contact time on adsorption capacity of NS-4 towards (a) MB, (b) CV and (c) CIP. Inset: MB solution at different intervals of adsorption.

(a)

5

MB

4 3

MB

2.5 2.0 1.5

1

t/qt

ln (qe-qt)

Jo

2

(b) 3.0

0

1.0

-1

0.5

-2

0.0

-3 0

50

100

150

200

0

t (min)

50

100

t (min)

19

150

200

250

(c)

(d)

CV

4

0.3

0.2

2

t/qt

ln (qe-qt)

3

CV

0.1

1

0

0.0

0

5

10

15

20

25

0

30

10

20

t (min)

CIP

0.5

3.2

0.4

CIP

re t/qt

1.6

0.3 0.2

0.8

lP

ln (qe-qt)

2.4

ro

(f) 0.6

4.0

-p

(e)

40

of

t (min)

30

0.1

0.0

0.0

0

5

10

15

20

25

35

40

45

0

10

20

30

40

50

t (min)

ur na

t (min)

30

Jo

Fig. 10. Fitting plots of (a) pseudo-first-order kinetics and (b) pseudo-second-order kinetics of MB; (c) pseudo-first-order kinetics and (d) pseudo-second-order kinetics of CV and (e) pseudofirst-order kinetics and (f) pseudo-second-order kinetics of CIP for the adsorption on NS-4.

Table 3 Kinetic parameters for the adsorption of MB, CV and CIP on NS-4.

20

Parameters

MB

CV

CIP

Experimental

qe,exp (mg g-1 )

76.17

147.40

78.92

qe,cal (mg g-1 )

72.90

38.74

27.28

k1 (min-1)

2.94×10-2

12.87×10-2

8.50×10-2

R2

0.9392

0.8087

0.9169

SSE

2.8722

3.2740

0.8067

χ2

1.8848

6.4162

0.6879

qe,cal (mg g-1 )

80.64

148.15

81.50

k2 (g mg-1 min-1)

9.43×10-4

1.92×10-2

6.86×10-3

R2

0.9952

0.9999

0.9996

SSE

0.0291

χ2

0.0169

order

Pseudo-second

0.00001

0.0001

0.0024

0.0005

(a)

(b)

20 ppm 30 ppm 40 ppm

120

120 100

lP

100

80

25 C 40 C 50 C

-1

qt (mg g )

80

-1

qt (mg g )

re

-p

order

ro

Pseudo-first-

of

Model

60

20 0 0

ur na

40

25

50

75

60 40 20 0 0

100 125 150 175 200 225

25

50

75

100 125 150 175 200 225

t (min)

t (min)

Fig. 11. (a) Effect of MB concentration and (b) effect of temperature on adsorption of MB onto

Jo

NS-4

The effect of initial dye concentration is represented in Fig. 11a. At a constant amount of adsorbent, the amount of dye adsorbed on NS-4 increases with an increase in the initial dye concentration. The adsorption process reaches equilibrium quickly at a lower concentration. The involved driving force is the mass gradient which increases with an increase in initial dye concentration. At lower concentrations, the ratios of dye molecules to the adsorption sites are 21

low. Hence, there is a possibility of only monolayer coverage but at higher concentration multilayer adsorption is more likely to happen. Temperature is an important factor in controlling the rate of adsorption. At an initial concentration of 40 ppm, the variation of adsorption capacity with temperature is depicted in Fig. 11b. The initial adsorption capacity rises sharply with the increase in temperature and the equilibrium is attained faster at a higher temperature. The initial steep rise in adsorption is attributed to an increase in the diffusion rate of dye molecules.

of ro

100

Intensity (a.u.)

80

-p

60 40 20 0 1

2

3

4

10

20

NS-4 fresh

NS-4 reused 30

40

50

60

70

80

2 (degree)

lP

Number of adsorption cycles

re

Adsorption efficiency (%)

3.4.3 Reusability and regeneration

Fig. 12. (a) Recyclability of the NS-4 after adsorption of MB and (b) XRD patterns of fresh and

ur na

reused NS-4.

The adsorbents need to be regenerated and recycled after the adsorption process in order to accomplish sustainable applications. For this study, 100 mg L-1 of MB is treated with 20 mg adsorbent. After the completion of the adsorption process, desorption was carried out with the mixture containing 10% acetic acid in ethanol. Because desorption of MB from adsorbent using

Jo

only ethanol was not satisfactory. Hence, glacial acetic acid is used to increase the polarity of the solvent to destroy the electrostatic interaction between adsorbate and adsorbent. It was further washed with the distilled water several times and then dried in the oven. The adsorption and desorption cycle was repeated for four times in a similar way. The adsorption efficiency for the first cycle of the adsorption process reached 99.7% and slightly decreased to 97 % in the fourth cycle (Fig. 12a). The data shows the good regeneration ability and reusability of the adsorbent

22

making it competent for water treatment. The XRD patterns of reused adsorbent were the same as for fresh adsorbent revealed the adsorbent was stable after reuse (Fig. 12b). 3.4.4 Effect of pH and Zeta Potential

(a)

(b)

60

5

MB

NS-4

40 30 20

Zero point charge -5 -10

of

-1

qe (mg g )

50

-15 -20

10 -25 1

2

3

4

5

6

7

8

9

2

3

ro

Zeta Potential (mV)

0

4

5

6

7

8

9

10

11

pH

-p

pH

re

Fig. 13. (a) Effect of pH on adsorption capacity of MB on NS-4 and (b) zeta potential value for NS-4 at different pH.

lP

The surface charge of the adsorbent as well as the charge of dye in an aqueous medium is greatly influenced by the pH of the adsorption medium; therefore, the effect of pH on adsorption of MB by NS-4 was studied. For this, the series of adsorption tests were carried out at different pH

ur na

values ranging from 2 to 10 using 5 mg adsorbent dose and 20 mL of 20 mg L-1 methylene blue solution. The results are shown in Fig. 13a. The adsorption capacity increases sharply over the range of pH 2 to 5. Afterward, the change in adsorption capacity was not significant. Furthermore, the role of surface charge towards adsorption was examined by the zeta potentials

Jo

value of NS-4 at different pH (Fig. 13b). The zero point charge (pH-ZPC) for NS-4 is 2.5. Therefore, the surface of the adsorbent is positively charged below pH 2.5, and above 2.5 the surface is negatively charged. The negative surface charge in the range of pH 5 to 8 makes it suitable for the adsorption of cationic adsorbates in a wide range of pH. 3.4.5 Selective adsorption and mechanism The feasibility of selective adsorption and separation of dyes using NS-4 were studied. The commercially available cationic dyes MB, CV, RhB; and anionic dyes MO, OG were taken for 23

further experiments. Since cationic MB (molecule size: 1.38 nm x 0.64 nm 0.21 nm) and anionic MO (molecule size: 1.54nm x 0.48 nm x 0.28 nm) have nearly similar size, [20] therefore, the surface charge of adsorbent may be the prime controlling factor in separation of dyes from its mixture.

(a)

(b)

MB+MO

1.2

1.6

RhB+MO

RhB

MB

0.4

MO 0.4

0.0

0.0 500

600

700

800

300

500

RhB

MB+RhB+MO

1.2

(d)

Absorbance

lP

MO

0.4

ur na

Absorbance

MB

0.8

MB+OG

300

400

500

600

700

0.8 OG

0.6 0.4 0.2

150 min

0.0

700

MB

1.0

1.2

600

Wavelength (nm)

re

Wavelength (nm)

1.6

400

180 min

-p

400

(c)

0.8

of

MO

ro

Absorbance

Absorbance

1.2 0.8

150 min 0.0 800

400

500

600

Wavelength (nm)

Jo

Wavelength (nm)

24

700

800

100

Cationic dye Anionic dye Antibiotic

80

(f) Absorbance

Asorption efficiency (%)

(e)

60 40

0.6

CIP

0.4

0.2

20 0

0.0 200

MB CV RhB MO OG CIP

25 min 250

300

350

400

of

Wavelength (nm)

ro

Fig. 14. UV- vis spectra of mixture of (a) MB and MO (20 mg L-1 each, 20 mL), (b) RhB and MO(10 mg L-1 each, 15 mL), (c) MB, RhB and MO (10 mg L-1 each, 10 mL), (d) MB and OG

-p

(20 mg L-1 each, 20 mL),(e) Adsorption efficiency of NS-4 for different dyes and CIP, and (f) CIP (50 mg L-1, 10 mL). Inset: the photos of before adsorption and after adsorption of dye

re

The UV-Vis spectra of adsorption of pure MB, CV, RhB, MO, and OG on NS-4 are shown in Fig. S2a-e†. The adsorption efficiency of different dyes using 20 mg L-1 dye (20 mL)

lP

with 5mg of adsorbent is shown in Fig. 14e. The adsorption efficiency of cationic dyes is much higher than the anionic dyes (0.03% for MO and 0.005% for OG). The inset of Fig. 14a shows that the color of the mixture of MB and MO changes from green to yellow after adsorption

ur na

which is clearly demonstrating effective adsorption of MB whereas MO is left in solution with negligible adsorption. The concentration of MB decreased from 20 mg L-1 to 0.34 mg L-1 and the concentration of MO has slightly decreased from 20 mg L-1 to 14.75 mg L-1 after 150 minutes. Thus, the separation efficiency is obtained to be 97.75 %. UV-vis spectra of the adsorption process (Fig. 14b) of the mixtures RhB/MO and MB/OG depict the gradual decrease in intensity

Jo

of absorption of RhB and MB while the adsorption intensity of MO and OG remains the same. The separation efficiency for MB and RhB in MB/OG and RhB/MO mixtures was 99.16 % and 74.73 %, respectively. Fig. 14c for the adsorption of a ternary mixture of dyes analysis revealed a better representation of adsorption where only cationic dyes MB and RhB are simultaneously adsorbed by NS-4 from the aqueous mixture of MB, RhB and MO. A lucid observation can be made from the adsorption of a mixture of dyes experiments that only cationic dyes are adsorbed by NS-4. The interaction involved is primarily electrostatic attraction. The negative zeta potential 25

values indicate the negative surface charge of the adsorbent. It is explicit from the zeta potential values that the electrostatic interaction occurs between positively charged dye molecules and the negatively charged dye whereas negatively charged methyl orange experience repulsion from the adsorbent (Scheme 1). The antibiotic ciprofloxacin exists as cationic species in acidic pH [65,66]. Therefore the adsorption experiments were carried out in acidic pH, in order to facilitate electrostatic attraction between positively charged CIP and negatively charged adsorbent for a high adsorption capacity. In addition, the hydrogen bonding and hydrophobic interaction might

ur na

lP

re

-p

ro

of

also be the contributing factors in the adsorption of CIP [67].

Scheme 1. A plausible mechanism for the selective adsorption of cationic dyes and the

Jo

adsorption ciprofloxacin antibiotic using GSH-capped nickel sulfide nanomaterial. In the mixture of MB and MO, the concentration of MB decreased from 20 mg L-1 to

0.34 mg L-1 and the concentration of MO has slightly decreased from 20 mg L-1 to 14.75 mg L-1 after 150 minutes. Thus, the separation efficiency is obtained to be 97.75%. A comparative study of equilibrium adsorption capacity for MO dye reveals that its adsorption capacity in the mixture (MB/MO) is higher than in its single solution (MO only) as evident from Fig. 14a and Fig. S2d†. This could be related to the negative zeta potential of NS-4 which leads to repulsion between the

26

negatively charged dye MO and the negatively charged surface of NS-4. Thus, there is no decrease in the adsorption peak of MO in a single solution. But in the mixture of MB and MO dyes, the capacity of MO is increased to a small extent. This may be due to the reduction in repulsion between MO dye and adsorbent because after adsorption of positively charged MB onto NS-4 through electrostatic interaction, the resultant zeta potential value may decrease leading to slight adsorption of MO.

ro

of

3.4.6. FTIR and XPS study of adsorbed dye

3426 1254 887 1397 1341

-p

Intensity (a.u.)

1600

885 1246 1330 3391

re

1595 1640

4000

3500

3000

2500

2000

lP

Pure MB NS- 4 (After) NS- 4 (Before)

3325

1500

Wavenumber (cm-1)

1000

500

ur na

Fig. 15. FTIR spectra pure MB, NS-4 after adsorption and before adsorption of MB. The interaction of MB with NS-4 was investigated through FTIR studies. The comparison of FTIR spectra of pure MB dye, NS-4 before and after adsorption is shown in Figure 15. A peak shift of MB was observed for stretching frequency of –OH group from 3426 to 3391 cm-1. This may because of hydrogen bonding between MB with NS-4. The peak originated

Jo

from MB adsorption had shifted from 1600 to 1595 cm-1 that indicates the hydrophobic interaction between aromatic C=C of MB. C=S+ stretching vibrations shifted from 1358 to 1351 cm-1 with a reduction in intensity and stretching vibration of C-N shifted from 1341 cm-1 to 1330 cm-1 indicates the presence of electrostatic interaction between MB and NS-4.

27

-NH, C=N (399.78 eV)

Intensity (a.u.)

(a)

Before After Pure MB

N 1s

(b)

Intensity (a.u.)

N 1s

After adsorption +NH , C=N+ 3 (401.40 eV)

410 408 406 404 402 400 398 396 394 392

406

404

402

400

398

396

394

of

Binding Energy (eV)

Binding Energy (eV)

ro

Fig. 16. XPS spectra showing (a) fitting of core-level spectra N1s of NS-4 after adsorption of MB and (b) comparison of XPS spectra of N1s of NS-4 before and after adsorption, and pure

-p

MB.

adsorption of MB. Atomic % Ni NS-4 (before 7.56

21.16

ur na

adsorption)

S

NS-4

(after 6.08

C

N

O

35.92

6.14

29.21

47.20

7.04

21.30

lP

Adsorbent

re

Table 4 Distribution of atomic percentage obtained from XPS analysis of NS-4 before and after

18.56

adsorption)

The XPS analysis of NS-4 after adsorption was also investigated to understand the

Jo

mechanism of interaction of MB. The Ni 2p spectra of NS-4 before and after adsorption do not show any significant differences, suggesting that the metal-coordination is playing a trivial role in the adsorption of MB (Fig. S3†). The fitted N 1s spectra of NS-4 adsorbent after adsorption of MB are shown in Fig. 16a. The peak at 399.98 eV of pure adsorbent is slightly shifted to the lower binding energy of 399.78 eV. The other component at 401.94 eV has also lightly broadened and shifted to 401.40 eV (∆ 0.54), which is attributed to the presence of imine nitrogen of MB with a positive charge held through the electrostatic interaction [68]. A 28

comparison of N 1s spectra of pure MB, NS-4 before and after adsorption showed a clear shift in binding energy (Fig. 16b). It can be inferred from the XPS spectra that the interaction of methylene blue happened through the nitrogen carrying a positive charge. The increase in the atomic percentage of carbon, nitrogen and sulfur elements in NS-4 due to adsorption of MB is evident from Table 4. 3.4. 7. Analysis of water samples

Before adsorption After adsorption

Before adsorption After adsorption

(b)

Sample 1

1.0

0.4

Sample 2

ro

0.6

0.8 0.6 0.4

-p

0.8

Absorbance

Absorbance

1.0

of

1.2

1.2

(a)

0.2

0.2

0.0

0.0

400

500

600

700

Wavelength (nm)

800

300

re

300

400

500

600

700

800

Wavelength (nm)

lP

Fig. 17. Adsorption of cationic adsorbates on NS-4 in different water samples. Simultaneous adsorption of MB, CV, and CIP on NS-4 was analyzed in different water

ur na

samples which will be useful for understanding the specificity of adsorbent in real applications. The sample1 was prepared in distilled water using two cationic dyes (20 mg L-1 each of MB and CV) and the antibiotic (20 mg L-1 of CIP) along with the inorganics (10 mg L-1 each of NaCl, KCl, Na2CO3, Na2SO4, (NH4)2PO4, CH3COONa, KNO3) at pH 7.0. Sample 2 was prepared in tap water using two cationic dyes (20 mg L-1 each of MB and CV) and the antibiotic (20 mg L-1 of

Jo

CIP) at pH 7.0. Both the samples were tested for the adsorption on NS-4. The UV-vis spectra showed the removal efficiency of 93.7% and 98.9 % for sample 1 and sample 2, respectively (Fig. 17). These results predicted the suitability of NS-4 in the simultaneous adsorption of cationic adsorbates from real wastewater. However the separation of cationic adsorbates from the mixtures of different cationic adsorbates is difficult.

29

4. Conclusions In this study, we have developed a novel surface modified nickel sulfide nanomaterial with flakes like morphology that was synthesized using a simple, cost-effective and eco-friendly method. The adsorption analysis showed a very high adsorption capacity i.e. 1006.52 mg g-1, 1946.61 mg g-1 and 971.83 mg g-1 towards cationic adsorbates MB, CV and CIP, respectively. The selectivity test in binary mixture of dyes revealed selective removal of cationic dye with high separation efficiency of 97.75 % and 99.16% for MB in MB/MO and MB/OG mixtures,

of

respectively. The adsorption isotherm models for cationic adsorbates MB, CV, and CIP were well described by the Freundlich isotherm model signifying the heterogeneous surface sites and

ro

multilayer coverage of the adsorbates on the surface of the adsorbent. The adsorption followed the pseudo-second-order kinetic model for all the cationic adsorbates. The adsorption mechanism

-p

was predominantly electrostatic which was confirmed through the pH effect, zeta-potential measurement, FT-IR and XPS analysis. The adsorbent was easily regenerated upto four times

re

using 10 % acetic acid-ethanol mixture without significant loss of efficiency. The synthetic strategy provides a potential adsorbent for the removal of cationic adsorbates and effective

Dr. S. Hussain, S. Kumari and A. A. Khan conceived and designed the research work. S. Kumari and A. A. Khan have done the synthesis of the adsorbent. S. Kumari has done the experimental work and compiled the results. All the authors have contributed to the interpretation of the data and drafted the manuscript.

Jo

   

ur na

Author contributions

lP

separation of dyes, envisaging a potential application in wastewater treatment.

Declaration of interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

30

Conflict of interest The authors declare that there is no conflict of interest.

Acknowledgment The authors S. Kumari and A. A. Khan thank UGC for the research fellowship. The author A. Chowdhury is thankful to the Indian Institute of Technology Patna for a research fellowship and

of

author A. K. Bhakta is thankful to the University of Namur for a CERUNA doctoral fellowship.

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We highly appreciate the research support from the Indian Institute of Technology Patna.

Jo

ur na

lP

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-p

Appendix A. Supplementary Material

31

References [1]

E. Sharifpour, H.Z. Khafri, M. Ghaedi, A. Asfaram, R. Jannesar, Isotherms and kinetic study of ultrasound-assisted adsorption of malachite green and Pb2+ ions from aqueous samples by copper sulfide nanorods loaded on activated carbon: Experimental design optimization,

Ultrason.

-Sonochemistry.

40

(2018)

373–382.

doi:10.1016/j.ultsonch.2017.07.030. [2]

E.A. Dil, M. Ghaedi, G.R. Ghezelbash, A. Asfaram, A.M. Ghaedi, F. Mehrabi, Modeling

of

and optimization of Hg2+ ion biosorption by live yeast: Yarrowia lipolytica 70562 from aqueous solutions under artificial neural network-genetic algorithm and response surface

ro

methodology: Kinetic and equilibrium study, RSC Adv. 6 (2016) 54149–54161.

[3]

-p

doi:10.1039/c6ra11292g.

H. Sun, L. Cao, L. Lu, Magnetite / Reduced Graphene Oxide Nanocomposites : One Step

re

Solvothermal Synthesis and Use as a Novel Platform for Removal of Dye Pollutants, Nano Res. 4 (2011) 550–562. doi:10.1007/s12274-011-0111-3. A. Asfaram, M. Ghaedi, A. Goudarzi, M. Rajabi, Response surface methodology approach

lP

[4]

for optimization of simultaneous dye and metal ion ultrasound-assisted adsorption onto Mn doped Fe3O4-NPs loaded on AC: Kinetic and isothermal studies, Dalt. Trans. 44

[5]

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(2015) 14707–14723. doi:10.1039/c5dt01504a. K.P. Singh, S. Gupta, A.K. Singh, S. Sinha, Optimizing adsorption of crystal violet dye from water by magnetic nanocomposite using response surface modeling approach, J. Hazard. Mater. 186 (2011) 1462–1473. doi:10.1016/j.jhazmat.2010.12.032. H. Mazaheri, M. Ghaedi, M.H. Ahmadi Azqhandi, A. Asfaram, Application of

Jo

[6]

machine/statistical learning, artificial intelligence and statistical experimental design for the modeling and optimization of methylene blue and Cd(II) removal from a binary aqueous solution by natural walnut carbon, Phys. Chem. Chem. Phys. 19 (2017) 11299– 11317. doi:10.1039/c6cp08437k.

[7]

X. Li, Z. Zhang, A. Fakhri, V.K. Gupta, S. Agarwal, Adsorption and photocatalysis assisted optimization for drug removal by chitosan-glyoxal/Polyvinylpyrrolidone/MoS2 32

nanocomposites,

Int.

J.

Biol.

Macromol.

136

(2019)

469–475.

doi:10.1016/j.ijbiomac.2019.06.003. [8]

M.C. Danner, A. Robertson, V. Behrends, J. Reiss, Antibiotic pollution in surface fresh waters:

Occurrence

and

effects,

Sci.

Total

Environ.

664

(2019)

793–804.

doi:10.1016/j.scitotenv.2019.01.406. [9]

C. Liang, X. Zhang, P. Feng, H. Chai, Y. Huang, ZIF-67 derived hollow cobalt sulfide as superior adsorbent for effective adsorption removal of ciprofloxacin antibiotics, Chem.

of

Eng. J. 344 (2018) 95–104. doi:10.1016/j.cej.2018.03.064.

ro

[10] A. Chowdhury, A.A. Khan, S. Kumari, S. Hussain, Superadsorbent Ni − Co − S/SDS Nanocomposites for Ultrahigh Removal of Cationic, Anionic Organic Dyes and Toxic

-p

Metal Ions: Kinetics, Isotherm and Adsorption Mechanism, ACS Sustain. Chem. Eng. 7 (2019) 4165–4176. doi:10.1021/acssuschemeng.8b05775.

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[11] P. Senthil Kumar, S. Ramalingam, C. Senthamarai, M. Niranjanaa, P. Vijayalakshmi, S. Sivanesan, Adsorption of dye from aqueous solution by cashew nut shell: Studies on

lP

equilibrium isotherm, kinetics and thermodynamics of interactions, Desalination. 261 (2010) 52–60. doi:10.1016/j.desal.2010.05.032. [12] H. Wang, Y. Wei, Magnetic graphene oxide modified by chloride imidazole ionic liquid

ur na

for the high-efficiency adsorption of anionic dyes, RSC Adv. 7 (2017) 9079–9089. doi:10.1039/c6ra27530c.

[13] A.A. Khan, S. Kumari, A. Chowdhury, S. Hussain, Phase Tuned Originated Dual Properties of Cobalt Sulfide Nanostructures as Photocatalyst and Adsorbent for Removal Dye

Jo

of

Pollutants,

ACS

Appl.

Nano

Mater.

1

(2018)

3474–3485.

doi:10.1021/acsanm.8b00656.

[14] M. Guo, M. Song, S. Li, Y. Zhilei, X. Song, Y. Bu, Facile and economical synthesis of ZnS nanotubes and their superior adsorption performance for organic dyes, CrystEngComm. 19 (2017) 2380–2393. doi:10.1039/c7ce00360a. [15] E. Alipanahpour Dil, M. Ghaedi, A. Asfaram, F. Mehrabi, F. Sadeghfar, Efficient 33

adsorption of Azure B onto CNTs/Zn:ZnO@Ni2P-NCs from aqueous solution in the presence of ultrasound wave based on multivariate optimization, J. Ind. Eng. Chem. 74 (2019) 55–62. doi:10.1016/j.jiec.2018.12.050. [16] E. Sharifpour, E. Alipanahpour Dil, A. Asfaram, M. Ghaedi, A. Goudarzi, Optimizing adsorptive removal of malachite green and methyl orange dyes from simulated wastewater by Mn-doped CuO-Nanoparticles loaded on activated carbon using CCD-RSM:

Organomet. Chem. 33 (2019) e4768. doi:10.1002/aoc.4768.

of

Mechanism, regeneration, isotherm, kinetic, and thermodynamic studies, Appl.

[17] B.H. Hameed, A.T.M. Din, A.L. Ahmad, Adsorption of methylene blue onto bamboo-

ro

based activated carbon: Kinetics and equilibrium studies, J. Hazard. Mater. 141 (2007)

-p

819–825. doi:10.1016/j.jhazmat.2006.07.049.

[18] J. Liu, M. Zeng, R. Yu, Surfactant-free synthesis of octahedral ZnO/ZnFe2O4

re

heterostructure with ultrahigh and selective adsorption capacity of malachite green, Sci. Rep. 6 (2016) 25074. doi:10.1038/srep25074.

lP

[19] N. Cheng, Q. Hu, Y. Guo, Y. Wang, L. Yu, Efficient and Selective Removal of Dyes Using Imidazolium-Based Supramolecular Gels, ACS Appl. Mater. Interfaces. 7 (2015) 10258–10265. doi:10.1021/acsami.5b00814.

ur na

[20] A. Mahdizadeh, S. Farhadi, A. Zabardasti, Microwave-assisted rapid synthesis of graphene-analogue hexagonal boron nitride (h-BN) nanosheets and their application for the ultrafast and selective adsorption of cationic dyes from aqueous solutions, RSC Adv. 7 (2017) 53984–53995. doi:10.1039/c7ra11248c.

Jo

[21] M.S. Bootharaju, T. Pradeep, Facile and rapid synthesis of a dithiol-protected Ag7 quantum cluster for selective adsorption of cationic dyes, Langmuir. 29 (2013) 8125– 8132. doi:10.1021/la401180r.

[22] B. Wang, Q. Zhang, G. Xiong, F. Ding, Y. He, B. Ren, L. You, X. Fan, C. Hardacre, Y. Sun, Bakelite-type anionic microporous organic polymers with high capacity for selective adsorption of cationic dyes from water, 366 (2019) 404–414.

34

[23] Q.S. Jie Zhang, Fan Li, Rapid and selective adsorption of cationic dyes by a unique metalorganic framework with decorated pore surface, Appl. Surf. Sci. 440 (2018) 1219–1226. doi:10.1016/j.apsusc.2018.01.258. [24] S.I. Raj, A. Jaiswal, I. Uddin, Tunable porous silica nanoparticles as a universal dye adsorbent, RSC Adv. 9 (2019) 11212–11219. doi:10.1039/C8RA10428J. [25] S.M. Pourmortazavi, M. Rahimi-Nasrabadi, M. Aghazadeh, M.R. Ganjali, M.S. Karimi, P. Norouzi, Synthesis, characterization and photocatalytic activity of neodymium carbonate

of

and neodymium oxide nanoparticles, J. Mol. Struct. 1150 (2017) 411–418.

ro

doi:10.1016/j.molstruc.2017.09.008.

[26] S.M. Pourmortazavi, H. Sahebi, H. Zandavar, S. Mirsadeghi, Fabrication of Fe3O4

-p

nanoparticles coated by extracted shrimp peels chitosan as sustainable adsorbents for removal of chromium contaminates from wastewater: The design of experiment, Compos.

[27] M.F.

Koudehi,

S.M.

re

Part B Eng. 175 (2019) 107130. doi:10.1016/j.compositesb.2019.107130. Pourmortazavi,

Polyvinyl

Alcohol/Polypyrrole/Molecularly

lP

Imprinted Polymer Nanocomposite as Highly Selective Chemiresistor Sensor for 2,4-DNT Vapor Recognition, Electroanalysis. 30 (2018) 2302–2310. doi:10.1002/elan.201700751. [28] S.M. Pourmortazavi, M. Rahimi-Nasrabadi, M.S. Karimi, S. Mirsadeghi, Evaluation of

by

ur na

photocatalytic and supercapacitor potential of nickel tungstate nanoparticles synthesized electrochemical

method,

New

J.

Chem.

42

(2018)

19934–19944.

doi:10.1039/c8nj05297b.

[29] R. Heydari, M.F. Koudehi, S.M. Pourmortazavi, Antibacterial Activity of Fe3O4/Cu

Jo

Nanocomposite: Green Synthesis Using Carum carvi L. Seeds Aqueous Extract, ChemistrySelect. 4 (2019) 531–535. doi:10.1002/slct.201803431.

[30] A. Molla, M. Sahu, S. Hussain, Synthesis of Tunable Band Gap Semiconductor Nickel Sulphide Nanoparticles: Rapid and Round the Clock Degradation of Organic Dyes, Sci. Rep. 6 (2016) 26034. doi:10.1038/srep26034. [31] J. Feng, J. Zhu, W. Lv, J. Li, W. Yan, Effect of hydroxyl group of carboxylic acids on the 35

adsorption of Acid Red G and Methylene Blue on TiO2, Chem. Eng. J. 269 (2015) 316– 322. doi:10.1016/j.cej.2015.01.109. [32] B. Saha, S. Das, J. Saikia, G. Das, Preferential and Enhanced Adsorption of Different Dyes on Iron Oxide Nanoparticles : A Comparative Study, J. Phys. Chem. C. 115 (2011) 8024–8033. doi:10.1021/jp109258f. [33] A. Chowdhury, S. Kumari, A.A. Khan, S. Hussain, Selective removal of anionic dyes with exceptionally high adsorption capacity and removal of dichromate (Cr2O72-) anion using

of

Ni-Co-S/CTAB nanocomposites and its adsorption mechanism, J. Hazard. Mater. (2019)

ro

121602. doi:10.1016/J.JHAZMAT.2019.121602.

[34] B.T. Zhu, Z. Wang, S. Ding, J.S. Chen, X.W. Lou, Hierarchical nickel sulfide hollow

-p

spheres for high performance supercapacitors, RSC Adv. 1 (2011) 397–400. doi:10.1039/c1ra00240f.

re

[35] N. Mahmood, C. Zhang, Y. Hou, Nickel sulfide/nitrogen-doped graphene composites: Phase-controlled synthesis and high performance anode materials for lithium ion batteries,

lP

Small. 9 (2013) 1321–1328. doi:10.1002/smll.201203032. [36] W.S. Chi, J.W. Han, S. Yang, D.K. Roh, H. Lee, J.H. Kim, Employing electrostatic selfassembly of tailored nickel sulfide nanoparticles for quasi-solid-state dye-sensitized solar

ur na

cells with Pt-free counter electrodes, Chem. Commun. 48 (2012) 9501–9503. doi:10.1039/c2cc34559e.

[37] M. Ghaedi, M. Pakniat, Z. Mahmoudi, S. Hajati, R. Sahraei, A. Daneshfar, Synthesis of nickel sulfide nanoparticles loaded on activated carbon as a novel adsorbent for the

Jo

competitive removal of Methylene blue and Safranin-O, Spectrochim. Acta - Part A Mol. Biomol. Spectrosc. 123 (2014) 402–409. doi:10.1016/j.saa.2013.12.083.

[38] A. Roffey, N. Hollingsworth, H.U. Islam, M. Mercy, G. Sankar, C.R.A. Catlow, G. Hogarth, N.H. De Leeuw, Phase control during the synthesis of nickel sulfide nanoparticles from dithiocarbamate precursors, Nanoscale. 8 (2016) 11067–11075. doi:10.1039/c6nr00053c.

36

[39] X. Zuo, S. Yan, B. Yang, G. Li, H. Zhang, H. Tang, ScienceDirect Template-free synthesis of nickel sulfides hollow spheres and their application in dye-sensitized solar cells, Sol. Energy. 132 (2016) 503–510. doi:10.1016/j.solener.2016.03.034. [40] P. Luo, H. Zhang, L. Liu, Y. Zhang, J. Deng, C. Xu, N. Hu, Y. Wang, Targeted synthesis of unique nickel sulfide (NiS, NiS2) microarchitectures and the applications for the enhanced water splitting system, ACS Appl. Mater. Interfaces. 9 (2017) 2500–2508. doi:10.1021/acsami.6b13984.

of

[41] M. Yang, Q. Bai, Flower-like hierarchical Ni-Zn MOF microspheres: Efficient adsorbents for dye removal, Colloids Surfaces A Physicochem. Eng. Asp. 582 (2019) 123795.

ro

doi:10.1016/j.colsurfa.2019.123795.

-p

[42] D. Maiti, S. Mukhopadhyay, P.S. Devi, Evaluation of Mechanism on Selective , Rapid and Superior Adsorption of Congo Red by Reusable Mesoporous α -Fe2O3 Nanorods,

re

ACS Sustain. Chem. Eng. 5 (2017) 2–9. doi:10.1021/acssuschemeng.7b01684. [43] G. Xiong, B. Wang, L. You, B. Ren, Y. He, F. Ding, Hypervalent silicon-based, anionic

lP

porous organic polymers with solid microsphere or hollow nanotube morphologies and exceptional capacity for selective adsorption of cationic dyes †, J. Mater. Chem. A. 7 (2019) 393–404. doi:10.1039/C8TA07109H.

ur na

[44] N. Peng, D. Hu, J. Zeng, Y. Li, L. Liang, C. Chang, Superabsorbent Cellulose-Clay Nanocomposite Hydrogels for Highly Efficient Removal of Dye in Water, ACS Sustain. Chem. Eng. 4 (2016) 7217–7224. doi:10.1021/acssuschemeng.6b02178. [45] P. Tian, X.Y. Han, G.L. Ning, H.X. Fang, J.W. Ye, W.T. Gong, Y. Lin, Synthesis of

Jo

porous hierarchical MgO and its superb adsorption properties, ACS Appl. Mater. Interfaces. 5 (2013) 12411–12418. doi:10.1021/am403352y.

[46] B. Baruwati, V. Polshettiwar, R.S. Varma, Glutathione promoted expeditious green synthesis of silver nanoparticles in water using microwaves, Green Chem. 11 (2009) 926– 930. doi:10.1039/b902184a. [47] H. Molavi, A. Shojaei, A. Pourghaderi, Rapid and tunable selective adsorption of dyes 37

using thermally oxidized nanodiamond, J. Colloid Interface Sci. 524 (2018) 52–64. doi:10.1016/j.jcis.2018.03.088. [48] Q. Yang, S. Ren, Q. Zhao, R. Lu, C. Hang, Z. Chen, Selective separation of methyl orange from water using magnetic ZIF-67 composites, Chem. Eng. J. 333 (2018) 49–57. doi:10.1016/j.cej.2017.09.099. [49] A.O. Dada, F.A. Adekola, E.O. Odebunmi, Kinetics, mechanism, isotherm and thermodynamic studies of liquid-phase adsorption of Pb2+ onto wood activated carbon

of

supported zerovalent iron (WAC-ZVI) nanocomposite, Cogent Chem. 3 (2017) 1–20.

ro

doi:10.1080/23312009.2017.1351653.

[50] A. Calborean, F. Martin, D. Marconi, R. Turcu, I.E. Kacso, L. Buimaga-Iarinca, F. Graur,

-p

I. Turcu, Adsorption mechanisms of L-Glutathione on Au and controlled nano-patterning through Dip Pen Nanolithography, Mater. Sci. Eng. C. 57 (2015) 171–180.

re

doi:10.1016/j.msec.2015.07.042.

[51] W. He, C. Wang, H. Li, X. Deng, X. Xu, Z. Tianyou, Ultrathin and Porous Ni3S2/CoNi2S4

lP

3D-Network Structure for Superhigh Energy Density Asymmetric Supercapacitors, Adv. Energy Mater. 7 (2017) 1700983. doi:10.1002/aenm.201700983. [52] W. Du, Z. Wang, Z. Zhu, S. Hu, X. Zhu, Y. Shi, H. Pang, X. Qian, Facile synthesis and

ur na

superior electrochemical performances of CoNi2S4/graphene nanocomposite suitable for supercapacitor

electrodes,

J.

Mater.

Chem.

A.

2

(2014)

9613–9619.

doi:10.1039/c4ta00414k.

[53] N. Kurra, C. Xia, M.N. Hedhili, H.N. Alshareef, Ternary chalcogenide micro-

Jo

pseudocapacitors for on-chip energy storage, Chem. Commun. 51 (2015) 10494–10497. doi:10.1039/c5cc03220b.

[54] L. Cheng, Y. Hu, L. Ling, D. Qiao, S. Cui, Z. Jiao, One-step controlled synthesis of hierarchical hollow Ni3S2/NiS@Ni3S4 core/shell submicrospheres for high-performance supercapacitors,

Electrochim.

Acta.

doi:10.1016/j.electacta.2018.07.013.

38

283

(2018)

664–675.

[55] C. Zhang, P. Li, W. Huang, B. Cao, Selective adsorption and separation of organic dyes in aqueous solutions by hydrolyzed PIM-1 microfibers, Chem. Eng. Res. Des. 109 (2016) 76–85. doi:10.1016/j.cherd.2016.01.006. [56] Z. Aksu, A.I. Tatli, Ö. Tunç, A comparative adsorption/biosorption study of Acid Blue 161: Effect of temperature on equilibrium and kinetic parameters, Chem. Eng. J. 142 (2008) 23–39. doi:10.1016/j.cej.2007.11.005. [57] P. Monash, G. Pugazhenthi, Adsorption of crystal violet dye from aqueous solution using

of

mesoporous materials synthesized at room temperature, Adsorption. 15 (2009) 390–405.

ro

doi:10.1007/s10450-009-9156-y.

[58] C. Lei, X. Zhu, B. Zhu, C. Jiang, Y. Le, J. Yu, Superb adsorption capacity of hierarchical

-p

calcined Ni/Mg/Al layered double hydroxides for Congo red and Cr(VI) ions, J. Hazard. Mater. 321 (2017) 801–811. doi:10.1016/j.jhazmat.2016.09.070.

re

[59] H. Li, X. Cao, C. Zhang, Q. Yu, Z. Zhao, X. Niu, X. Sun, Y. Liu, L. Ma, Z. Li, Enhanced adsorptive removal of anionic and cationic dyes from single or mixed dye solutions using

lP

MOF PCN-222, RSC Adv. 7 (2017) 16273–16281. doi:10.1039/C7RA01647F. [60] S. Chakraborty, S. Chowdhury, P. Das Saha, C. Violet, Adsorption of Crystal Violet from aqueous solution onto NaOH-modified rice husk., Carbohydr. Polym. 86 (2011) 1533–

ur na

1541. doi:10.1016/j.carbpol.2011.06.058.

[61] S. Shi, Y. Fan, Y. Huang, Facile low temperature Facile low temperature hydrothermal synthesis of magnetic mesoporous carbon nanocomposite for adsorption removal of ciprofloxacin

antibiotics,

Ind.

Eng.

Chem.

Res.

52

(2013)

2604–2612.

Jo

doi:10.1021/ie303036e.

[62] N. Khoshnamvand, S. Ahmadi, F.K. Mostafapour, Kinetic and isotherm studies on ciprofloxacin an adsorption using magnesium oxide nanopartices, J. Appl. Pharm. Sci. 7 (2017) 79–83. doi:10.7324/JAPS.2017.71112. [63] J. Liu, L.M. Wong, Gurudayal, L.H. Wong, S.Y. Chiam, S.F. Yau Li, Y. Ren, Immobilization of dye pollutants on iron hydroxide coated substrates: Kinetics, efficiency 39

and the adsorption mechanism, J. Mater. Chem. A. 4 (2016) 13280–13288. doi:10.1039/c6ta03088b. [64] A.K. Bhakta, S. Kumari, S. Hussain, P. Martis, R.J. Mascarenhas, J. Delhalle, Z. Mekhalif, Synthesis and characterization of maghemite nanocrystals decorated multi-wall carbon nanotubes for methylene blue dye removal, J. Mater. Sci. 54 (2019) 200–216. doi:10.1007/s10853-018-2818-y. [65] S. Rakshit, D. Sarkar, E.J. Elzinga, P. Punamiya, R. Datta, Mechanisms of ciprofloxacin

of

removal by nano-sized magnetite, J. Hazard. Mater. 247 (2013) 221–226.

ro

[66] E.I. El-shafey, H. Al-lawati, A.S. Al-sumri, Ciprofloxacin adsorption from aqueous solution onto chemically prepared carbon from date palm leaflets, J. Environ. Sci. 24

-p

(2012) 1579–1586. doi:10.1016/S1001-0742(11)60949-2.

[67] E. Cao, W. Duan, A. Wang, Y. Zheng, Oriented growth of poly(m-phenylenediamine) on

re

Calotropis gigantea fiber for rapid adsorption of ciprofloxacin, Chemosphere. 171 (2017) 223–230. doi:10.1016/j.chemosphere.2016.12.087.

lP

[68] A. Mohtasebi, T. Chowdhury, L.H.H. Hsu, M.C. Biesinger, P. Kruse, Interfacial Charge Transfer between Phenyl-Capped Aniline Tetramer Films and Iron Oxide Surfaces, J.

Jo

ur na

Phys. Chem. C. 120 (2016) 29248–29263. doi:10.1021/acs.jpcc.6b09950.

40