Dual use of colorimetric sensor and selective copper removal from aqueous media with novel p(HEMA-co-TACYC) hydrogels: Cyclen derivative as both monomer and crosslinker

Journal Pre-proof Dual use of colorimetric sensor and selective copper removal from aqueous media with novel p(HEMA-co-TACYC) hydrogels: Cyclen derivative as both monomer and crosslinker Hava Ozay, Zeynep Gungor, Betul Yilmaz, Pinar Ilgin, Ozgur Ozay

PII:

S0304-3894(19)31802-3

DOI:

https://doi.org/10.1016/j.jhazmat.2019.121848

Reference:

HAZMAT 121848

To appear in:

Journal of Hazardous Materials

Received Date:

23 September 2019

Revised Date:

6 December 2019

Accepted Date:

7 December 2019

Please cite this article as: Ozay H, Gungor Z, Yilmaz B, Ilgin P, Ozay O, Dual use of colorimetric sensor and selective copper removal from aqueous media with novel p(HEMA-co-TACYC) hydrogels: Cyclen derivative as both monomer and crosslinker, Journal of Hazardous Materials (2019), doi: https://doi.org/10.1016/j.jhazmat.2019.121848

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier.

Dual use of colorimetric sensor and selective copper removal from aqueous media with novel p(HEMA-co-TACYC) hydrogels: Cyclen derivative as both monomer and crosslinker

Hava Ozaya*, Zeynep Gungorb, Betul Yilmazc, Pinar Ilgind, Ozgur Ozaya,e

Laboratory of Inorganic Materials, Department of Chemistry, Faculty of Science and Arts,

ro of

a

Canakkale Onsekiz Mart University, Canakkale, Turkey

Graduate School of Natural and Applied Sciences, Department of Chemistry, Canakkale

-p

b

Onsekiz Mart University, Canakkale, Turkey

Graduate School of Natural and Applied Sciences, Department of Bioengineering and

re

c

d

lP

Materials Engineering, Canakkale Onsekiz Mart University, Canakkale, Turkey Department of Chemistry and Chemical Processing Technologies, Lapseki Vocational

na

School, Canakkale Onsekiz Mart University, Canakkale/Lapseki, Turkey e

Canakkale, Turkey

Jo

ur

Department of Bioengineering, Faculty of Engineering, Canakkale Onsekiz Mart University,

*Corresponding

author. Tel: +90 (286) 218 0018/2735, Fax: +90 (286) 218 05 26

E-mail: [email protected] Address: Laboratory of Inorganic Materials, Department of Chemistry, Faculty of Science and Arts, Canakkale Onsekiz Mart University, Canakkale, Turkey

HIGHLIGTHS

na

lP

re

-p

ro of

Graphical abstract

ur

 Cyclen based compound was synthesized as both monomer and cross-linker agent.  The novel hydrogels was synthesized as both a sensor and an absorbent material for

Jo

Cu2+.

 Selective copper removal from aqueous media with novel p(HEMA-co-TACYC) hydrogels.  p(HEMA-co-TACYC) hydrogels are reusable adsorbent materials for Cu2+ ions.

ABSTRACT Within the scope of this study, p(2-hydroxyethyl methacrylate-co- tetraacrylic cyclen) (p(HEMA-co-TACYC)) hydrogels were synthesized for the first time in the literature using a tetraacrylic cyclen (TACYC) as both functional monomer and crosslinker. The hydrogels designed especially for Cu2+ ions showed colorimetric sensor behavior selective for Cu2+ ions in all aqueous media (deionized, tap, river and sea water) and in metal ion mixtures. The p(HEMA-co-TACYC) hydrogels forming a stable complex with Cu2+ ions simultaneously

ro of

showed properties of being a good adsorbent material. The hydrogels have reuse capacity as both sensor and adsorbent material. Changing the amount of TACYC in the hydrogel structure changes the maximum adsorption capacity for Cu2+ ions. The Langmuir and

-p

Freundlich adsorption constants for Cu2+ ion adsorption of the hydrogels, acting as selective

lP

re

adsorbent in all aqueous media and metal ion mixtures, were determined.

ur

1. Introduction

na

Keywords: Hydrogel, cyclen, sensor, copper removal, selective adsorption.

Inorganic pollutants, including heavy metal ions, have rapidly polluted nature in the

Jo

last century. The most important sources of heavy metal pollution are industrial regions, mines and waste disposal sites. Heavy metals occurring in waste accumulate in water resources like groundwater, lakes, rivers and seas (Ayaz et al., 2019; Bilardi et al., 2019; Shen et al., 2019; Wang et al., 2015). Nonbiodegradable heavy metal ions accumulating in nature have toxic effects on living organisms. The final point for the toxic effects due to heavy metal ions is humans. Copper is a heavy metal ion causing a variety of diseases in humans

(Arunbabu et al., 2011; Awual, 2019; Guo et al., 2019). In addition to industrial activities, copper accumulates directly in living organisms through pesticide residues. Additionally, copper is a significant cofactor at low concentrations for many enzymes in living organisms. However, excessive copper intake disrupts the organism causing the occurrence of renal and liver disorders, Menkes syndrome, Alzheimer and Wilson diseases (Joseph et al., 2019; Jung et al., 2019). Due to all these negative effects, the United States Environmental Protection Agency (US EPA) and World Health Organization (WHO) stated the amounts of copper

ro of

permitted in water were 1.3 mg/L and 2.0 mg/L, respectively. A variety of studies have been performed in the literature in recent times about rapid identification and removal of a variety of heavy metals (Bezzina et al., 2019; Liao and Huang, 2019; Liu et al., 2019; Qing et al.,

-p

2014). There are many methods for removal of heavy metals from water resources such as chemical precipitation, membrane separation, evaporation, ion-exchange, evaporation, and

re

adsorption. Among these methods, the most commonly chosen for heavy metal pollution in

lP

the literature is removal by the adsorption method. The greatest advantage of the adsorption method in which a variety of biomass resources, resins, composite material and hydrogels are used as adsorbent material is the low cost, repeated usability and high efficiency compared to

na

other methods (Joseph et al., 2019; Li et al., 2019; Ozay et al., 2009; Wen et al., 2019; Zhao et

ur

al., 2019; Zhou et al., 2019).

One of the most commonly used adsorbent materials for heavy metal adsorption from

Jo

solution media is hydrogels (Ozay et al., 2010). Hydrogels, called smart materials with crosslinker and network structure, can swell to thousands of times their dry mass in aqueous media. Due to functional groups like –OH, -NH2, -COOH, and -SO3H contained in the threedimensional structure, they can adsorb pollutant species in aqueous media through both electrostatic interactions and secondary interactions (El-hoshoudy et al., 2019; Glowinska et al., 2019; Yang and Zeng, 2013). Hydrogels with hydrophilic properties are unrivaled for

applications in aqueous media. In the literature, interest has increased in adsorbent hydrogels in recent times due to many features such as the use of a variety of monomers to synthesize the copolymeric structure and ability to synthesize as composite materials (Dai et al., 2019; Samaddar et al., 2019; Tamesue et al., 2019). Hydrogels can form an insoluble structure by crosslinking commercial polymers and monomers containing two vinyl groups in the structure like N,N′-methylenebis(acrylamide), poly(ethylene glycol) diacrylate, and poly(ethylene glycol) dimethacrylate (Ilgin et al., 2019a; Krakovský et al., 2019; Liu et al., 2018; Ozay et

ro of

al., 2016). The crosslinker used to crosslink these flat polymer chains does not contain any other functional group in their structure. In recent times in the literature, studies related to synthesis of new functional monomers and crosslinkers, and use of these functional

-p

monomers in polymerization reactions are continuously increasing (Cuggino et al., 2013; Ilgin et al., 2019b; Ozay et al., 2016; Thombare et al., 2018). In the literature, though cyclen and

re

cyclam derivatives were used to carry out aerogel synthesis by Bereczki et al., there is no

lP

study found about the use of cyclen compound as monomer and crosslinker in hydrogel structures (Bereczki et al., 2016).

na

Polycycloalkanes are well-known important compounds due to their functions in biological systems and easy binding capability for transition metals. Preparation of these

ur

compounds and selective N-alkylation is one of the most studied and popular topics for research groups over many years (Hubin et al., 2019; Tsebrikova et al., 2018; Yina et al., One

of

the

most

important

polyasacycloalkanes

is

cyclen

(1,4,7,10-

Jo

2012).

Tetraazacyclododecane). Cyclen plays an important role in preparation of pharmaceutical molecules used for diagnosis, treatment and development of magnetic resonance imaging (MRI) agents (Abozeid et al., 2018; Pujales-Paradela et al., 2019; Müntener et al., 2019). Some metal complexes of cyclen were determined to form stable complexes with certain nucleic acids at physiologic pH and many studies have been performed about the interaction

with DNA of these complexes based on these features. Additionally, the catalytic properties of cyclen for some reactions forming a model for copper (I) and (II) complexes in biologic systems has attracted attention to these compounds (He at al., 2019; Rahman et al., 2019; Wang et al., 2017). In addition to all these properties, in recent years some studies have reported the use of N-substituent cyclen compounds for selective determination of Cu (II) ions (Chen et al., 2015; Wang et al., 2012). This study was carried out with the aim of researching the possibility to use cyclen in a

ro of

hydrogel structure. For this, the TACYC compound containing four acryloyl groups was synthesized for use in hydrogel production. Using the Cu2+ ion selective TACYC monomer and HEMA, p(HEMA-co-TACYC) hydrogels were synthesized with different ratios of

-p

monomers and characterized. It was shown that the obtained hydrogels can be used as a colorimetric sensor for Cu2+ ions in a variety of aqueous media. In addition to sensor

re

applications, the hydrogel was used as a selective adsorbent material for Cu2+ ions in aqueous

ur

2.1. Materials

na

2. Materials and Methods

lP

media.

Jo

The 1,4,7,10-tetraazacyclododecane (cyclen), propylene oxide, acryloyl chloride, and triethylamine used for monomer synthesis were obtained from Sigma-Aldrich and Merck companies. The monomer (2-hydroxyethyl methacrylate (HEMA)), initiator (ammonium persulfate (APS)) and accelerator (N,N,N',N'-tetramethylethylenediamine (TEMED)) used for hydrogel synthesis were obtained from Sigma-Aldrich. THF, ethanol and all other chemical materials used in experiments were of analytic purity and used without further purification. The sulfate salts of copper(II), cobalt(II), nickel(II) and iron(II) ions (Sigma-Aldrich) with

perchlorate salts (Sigma-Aldrich) of other metal ions were used during adsorption studies and perchlorate salts were used during sensor studies as metal ion sources. All solutions prepared in aqueous media for both sensor and adsorption studies used deionized water. Tap water (Çanakkale/Turkey),

river

water

(Sarıçay/Çanakkale/Turkey),

and

sea

water

(Assos/Çanakkale/Turkey) were used from the sources without any further processing. The FT-IR and NMR spectra used for characterization of the synthesized monomer were recorded with Perkin Elmer FT-IR spectrophotometer and JEOL NMR (400 MHz)

ro of

devices. A JEOL SEM-7100-EDX device was used to image the hydrogel surfaces. All analyses related to the study were completed in Çanakkale Onsekiz Mart University Science

-p

and Technology Application and Research Center (COBİLTUM). 2.2. Synthesis of TACYC

re

Synthesis of TACYC was completed in two sequential steps. With this aim, firstly the

lP

synthesis of 1,4,7,10-tetrakis(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane was carried out from the reaction of cyclen with propylene oxide in ethyl alcohol medium according to the literature (Chin et al., 1994). In the second step, a solution of acryloyl chloride (0.67 g; 7.44

na

mmol) in dry THF (25 mL) was added dropwise to a solution of 1,4,7,10-tetrakis(2hydroxypropyl)-1,4,7,10-tetraazacyclododecane (0.50 g; 1.24 mmol) and triethylamine (1.51

ur

g; 14.88 mmol) in dry THF (25 mL) (at 0 °C in argon atmosphere). With the start of this

Jo

addition, white salt formation was observed simultaneously in the reaction medium. After the end of this addition, the reaction mixture was mixed overnight at room temperature in argon atmosphere. Later, salts were separated by filtration from the reaction mixture. Finally, the solvent of the reaction mixture was evaporated under reduced pressure. The oily orange residue obtained was purified by column chromatography applied using CH2Cl2:EtOH as eluent on aluminum oxide. The yellow-colored oily TACYC was obtained (0.598 g; 78%).

FTIR-ATR (νmax, cm-1): 2955-2852 (C-H), 1714 (C=O), 1182 (C-O-C). 1H NMR (400 MHz, CDCl3, 25 °C): δ 6.22-6.28 (d), 6.06-6.12 (m), 5.46-5.57 (d), 3.96 (m), 2.75 (d), 2.36 (s), 1.34 (d).

13

C NMR (100 MHz, CDCl3, 25 °C): δ 166.01 (C=O), 154.37, 131.51, 129.09, 68.47,

55.02, 45.89, 19.26. LCMS (ESI+) m/z: 622.1500 (M+ 2H+). 2.3. Copper ion selectivity of TACYC The interaction of the synthesized and characterized TACYC for use in the

ro of

polymerization reaction with some metal ions was visually and spectroscopically investigated. With this aim, the stock solution of TACYC in ethyl alcohol was added to 2.5 mL deionized water ethanol mixture. After addition, the final concentration of TACYC was 5 x 10-4 M. The stock solution of metal ions was added to the solution of TACYC and the final metal ion

-p

concentration in the solution was 5 x 10-3 M. After addition of metal ions, the colorless

re

solution turned blue in the vial containing Cu2+ ions. After visual investigation, the UV-VIS spectra of all solutions were recorded. To examine the competitive effect of other metal ions

lP

on the colorimetric sensor property of TACYC for Cu2+ ion, a series of solutions each containing Cu2+ and an equal concentration of another metal ion were used.

na

2.4. Synthesis and swelling characterization of p(HEMA-co-TACYC) hydrogels

ur

p(HEMA-co-TACYC) hydrogels were prepared with a variety of copolymer ratios using the redox polymerization method with amounts given in Table 1 according to the

Jo

literature (Ilgin et al., 2019; Ozay et al., 2016). Accordingly, TACYC dissolved in 0.25 mL ethanol was added to HEMA (0.15 mmol) and the monomer mixture was stirred until a homogeneous mixture was obtained. Then 50 µL TEMED and APS dissolved in 0.2 mL deionized water were added to the monomer mixture. The reaction mixture was placed in 5 mm diameter plastic straws and left for 2 hours for the reaction to complete. At the end of this duration, the hydrogels removed from the straws were cut into disks of nearly 3 mm length.

The hydrogels were washed in deionized water for 24 hours to remove unreacted species and then dried at 40 °C in a vacuum oven. Gelation ratios of the dried and weighed hydrogels were calculated with the gravimetric method. For use as controls in sensor studies, p(HEMA) and p(AMPS) hydrogels were synthesized with the redox polymerization method as mentioned above using 0.05% and 1% MBA, respectively.

ro of

The water holding capacity of p(HEMA-co-TACYC) hydrogels was determined with the gravimetric method. Dry hydrogel with known mass was left in 50 mL deionized water and the increase in mass was measured at specific times. With these values, the water holding

-p

capacity was determined using the equation in Eq. 1.

(Eq.1)

re

Where M0 and Mt are the mass of the hydrogel before and after the swelling process at

lP

time t.

na

2.5. Colorimetric detection and selectivity studies with hydrogels

ur

Firstly, p(HEMA-co-TACYC) hydrogels were tested for selective behavior against metal ions by being left for 2 hours in a variety of metal ion solutions. For this purpose, one

Jo

sample of about 25 mg mass of the 5 types of hydrogels synthesized was left in Cu 2+, Co2+, Ni2+, Hg2+, Zn2+, Mn2+, Ba2+, Ca2+, Cd2+, Pb2+, Mg2+, Fe2+, and Fe3+ solutions with 100 mg/L (100 mL) concentration. Additionally, 25 mg of Hydrogel2 was left in a solution (100 mg/L; 100 mL) containing every ion (Cu2+, Co2+, Ni2+, Hg2+, Zn2+, Mn2+, Ba2+, Ca2+, Cd2+, Pb2+, Mg2+, Fe2+, and Fe3+) to determine whether the hydrogel was selective in metal ion mixtures. Later, 25 mg Hydrogel2 was used in the concentration interval of 5-100 mg/L (100 mL) to

determine the color change features of the p(HEMA-co-TACYC) hydrogels based on solution concentration. To examine the competitive effect of other metal ions on the colorimetric sensor property of p(HEMA-co-TACYC) hydrogels for Cu2+ ion, hydrogels were kept in a solutions each containing an equal concentration of Cu2+ and another metal ion. Then, about 2 mm thickness films were cut from the hydrogels washed with deionized water. The UV-Vis spectra of the obtained films were recorded.

ro of

2.6. Copper removal from aqueous media with p(HEMA-co-TACYC) hydrogels Nearly 100 mg p(HEMA-co-TACYC) hydrogel to be used as adsorbent material for Cu2+ ions was used for the adsorption studies in 100 mL (100 mg/L) solution volumes. For this, firstly solutions containing Cu2+, Co2+, Ni2+, Hg2+, Zn2+, Mn2+, Ba2+, Ca2+, Cd2+, Pb2+,

-p

Mg2+, and Fe2+ ions were prepared using deionized water, tap water, river water and sea

re

water. The maximum adsorption capacity for each metal ion was determined by leaving Hydrogel1 in the prepared solutions for 12 hours. Later to determine the effect of solution

lP

concentration on adsorption, solutions containing 1-500 mg/L Cu2+ ion were used. After ensuring adsorption at room temperature for 12 hours for Hydrogel1, the maximum Cu2+ ion

na

holding capacity of hydrogels was determined. The effect of duration and water sources on adsorption amount was determined using deionized water, tap water, river water and sea water

ur

with 100 mg/L (100 mL) Cu2+ solution using 100 mg Hydrogel1. To investigate the effect of pH on Cu2+ adsorption, 100 mg/L Cu2+ solutions (100 mL) in the range of pH = 2-5 were used

Jo

as adsorption solution and 100 mg Hydrogel1 as adsorbent. The pH of the Cu2+ solutions was adjusted using 0.1 M HCl and 0.1 M NaOH. After adsorption, to show the reusability of hydrogels, Hydrogel1 with maximum capacity adsorption was left in 1 M HCl solution to ensure desorption of Cu2+ ions. Later the desorbed hydrogels were washed with 0.1 M 25 mL NaOH and deionized water (until medium pH=7) respectively before reuse.

All adsorption studies were completed 3 times, with means calculated. For metal ion measurements, inductively coupled plasma optical atomic emission spectroscopy (ICP-OES) was used. 3. Results 3.1. Characterization and complex formation of TACYC The TACYC monomer was synthesized in two steps as given in Fig. 1 (reaction yield 13

C-

ro of

78%). For the structural characterization of the synthesized TACYC, FT-IR, 1H-NMR,

NMR and LC-MS methods were used. In the FT-IR spectrum of TACYC, stretching vibrations related to aliphatic C-H, C=O and C-O-C groups were observed at 2955-2852,

-p

1714 and 1182 cm-1, respectively (Fig. S1). The 1H-NMR spectrum for TACYC is given in Fig. S2. As seen on the figure, the signals for acrylic protons were observed in the range of

re

6.28-5.46 ppm. -CH3 protons in the structure resonated as a doublet peak at 1.34 ppm, while

lP

the signal for -CH- protons is seen as multiple peaks observed at 3.96 ppm. Additionally, the N-CH2- protons from propyl fragments found in the structure resonate at 2.75 ppm and are split in two by the neighboring CH proton. The N-CH2 protons from the cyclen ring give a

na

single signal at 2.36 ppm due to symmetric status in the structure. The 7 different carbon signals observed on 13C-NMR (Fig. S3) and the molecular ion peak observed on the LC-MS

ur

spectrum at 622.1500 (Fig. S4) support the structure of TACYC.

Jo

After synthesis and structural characterization of TACYC, the interaction with

transition metal ions was tested visually and spectroscopically. With this aim, Cu2+, Co2+ and Ni2+ ion solutions were added to 5 x 10-5 M solution of TACYC in water, which will possibly form colored complex compounds with cyclen derivatives. As seen in the digital camera images given in Fig. 2(a), a change in color of the solution was only observed visually in the presence of Cu2+ ions. The initially colorless solution of TACYC turned blue as a result of

complex formation with Cu2+ ions in the medium. This observed colorimetric situation was supported spectroscopically. On the UV-Vis spectra given in Fig. 2(b), a notable change in the TACYC spectrum was only observed in the presence of Cu2+ ions. The source of the blue color with peak observed at nearly λmax= 630 nm in the spectrum is the d-d transitions belonging to the Cu2+ ions (Carreira-Barral et al., 2017; Chen et al., 2015; Wang et al., 2017). The intense peak observed in the spectrum at λmax= 315 nm belongs to metal-to-ligand charge transfer band (Ozay et al., 2011). As seen on the spectrum, TACYC displays selective

ro of

behavior for the Cu2+ ions. This behavior is a result of cyclen derivatives forming a more stable complex with Cu2+ and complies with studies reporting tendency and selective behavior of cyclen derivative compounds for Cu2+ ions (Chen et al., 2015; Koike et al., 1996; Pérez-

-p

Toro et al., 2015; Ozay et al., 2011; Sasakura et al., 2011; Wang et al., 2012). To investigate the competitive effect of other metal ions on the sensor property, the intensities of absorbance

re

peak (max=630 nm) of TACYC solutions containing Cu2+ and another metal ion were plotted

lP

in Fig.2 (c). As can be seen from the figure, other metal ions have no significant effect on the

na

selective sensor property of TACYC against Cu2+ ions.

3.2. Colorimetric detection of Cu2+ ions with p(HEMA-co-TACYC) hydrogels

ur

The SEM images of p(HEMA-co-TACYC) hydrogel networks synthesized from

Jo

TACYC as monomer, selective for Cu2+ ions, are seen in Fig. 3(a). Similarly, the SEM image of p (HEMA-co-TACYC)-Cu2+ complex given in Fig. 3(b) shows that there was no change in surface morphology of the hydrogel after adsorption. Accordingly, it can be said that hydrogels have a homogeneous structure without pores before and after adsorption. When the hydrogel interacts with water, water molecules and other molecules dissolved in water are taken into the network structure via the diffusion route. Active sites found within the network

structure form a complex with Cu2+ ions, just as in the monomer form, and cause a color change in the hydrogel (Fig. 3(c)). Thus, the presence of Cu2+ ions in aqueous media can be observed with UV-vis spectrophotometer as in Fig. 3(d). Here, the absorption band in the presence of Cu2+ ions shows that hydrogels can also be used for production of any copper sensor. However, the color change in the hydrogel structure due to the effect of Cu2+ ions in any solution is more pronounced than with the soluble molecular or polymeric sensors. The technological infrastructure of detecting color change due to ion-sensor interaction is

ro of

available today. With a simple application, especially for smartphones, the amount of ions in the solution can be determined quickly depending on the color tone, similar to that shown in Fig. 3(d) (Liu et al., 2019; Anand and Sahoo, 2019). The effect of other metal ions on the

-p

signal of p(HEMA-co-TACYC) hydrogel consisting of blue color transformation against Cu2+ ions was investigated. Fig. 3(e) shows the absorption density (max= 600 nm) of hydrogels

re

kept in solutions containing Cu2+ and another metal ion. As seen from the figure, the blue

lP

color of p(HEMA-co-TACYC) hydrogel for Cu2+ ion is not affected by other metals. In addition, when we kept the p(HEMA-co-TACYC) hydrogel in a mixture of all metal ions (red

na

spectrum in Fig. 3 (d)) we found that there was a negligible effect on the signal. Recently, utilization of molecular ion sensor systems for the detection of heavy metals

ur

is one of the most popular methods used. Compounds with colorimetric sensor properties act on the principle of changing color in the presence of heavy metal ions. These sensors are

Jo

chosen due to rapid response to heavy metal ions, low cost, high selectivity and not requiring any device for use (Jeevica and Shankaran, 2016; Martinez et al., 2017; Ozay and Ozay, 2013; Sedghi et al., 2015; Ye et al., 2012). In the literature, there are many studies about colorimetric determination of many metal ions. Most of these are homogeneously dissolved in the solution medium. As a result, it is impossible to separate these types of sensors from the aqueous medium or to reuse them again. This situation has led to the selection of insoluble

and hydrophilic material with colorimetric sensor properties. As shown in Fig. 4, after the sensor synthesized in hydrogel form is used to determine metal ions in aqueous media with a color change, it can be removed from the media by simple filtration. Hydrogel2 synthesized within the scope of this study was used for colorimetric determination of Cu2+ ions in aqueous media. Fig. 4(a) shows the dry and swollen Hydrogel2 and p(HEMA) hydrogel (crosslinked with MBA) synthesized as control. Here, Hydrogel2 has yellow color due to the yellow color of the TACYC monomer. Fig. 4(b) shows the digital camera images of Hydrogel2, p(HEMA)

ro of

and p(AMPS) hydrogels after being left in solutions (100 mg/L; 100 mL Cu2+) for 2 hours. Accordingly, the p(HEMA) hydrogel crosslinked with MBA shows no colorimetric sensor properties for Cu2+ ions. If the color of p(AMPS), containing ionic –SO3H groups in its

-p

structure and easily entering electrostatic interactions with Cu2+ ions, is compared with the color of Hydrogel2, Hydrogel2 shows colorimetric sensor properties in the presence of Cu 2+

re

ions. It is expected that a sensor used in aqueous media will not enter interactions with other metal ions in the medium. As seen on Fig. 4(c), the change in the color of Hydrogel2 was not

lP

observed in the presence of other ions (Co2+ , Ni2+, Hg2+, Zn2+, Mn2+, Ba2+, Ca2+, Cd2+, Pb2+, Mg2+, Fe3+, and Fe2+) (100 mg/L, 100 mL), only for Cu2+ ions. As a result, the p(HEMA-co-

na

TACYC) hydrogels acted as selective colorimetric sensor for Cu2+ ions. Again, Fig. 4(d) shows the colors of complexes formed by Hydrogel2 with a variety of Cu2+ ion concentrations

ur

(5-100 mg/L, 100 mL). Accordingly, the different blue color tones of p(HEMA-co-TACYC)

Jo

hydrogels may be appropriate for the visual determination of Cu2+ solution concentrations. 3.3. Cu2+ removal from aqueous media with hydrogels Metal ions occurring as a result of industrial activities generally pollute groundwater,

sea water and rivers. As a result, it is important that material to be used for water treatment purposes can adsorb metal ions in a variety of aqueous media. The hydrogels which can be used as naked-eye sensors for Cu2+ ions may also be used as selective adsorbents. With this

aim, Hydrogel1 (containing 0.50 mmol TACYC) was synthesized for use in Cu2+ ion adsorption. Hydrogel1 was used as adsorbent material in solutions (100 mg/L, 100 mL) containing Cu2+, Co2+, Ni2+, Hg2+, Zn2+, Mn2+, Ba2+, Ca2+, Cd2+, Pb2+, Mg2+, and Fe2+ ion mixtures in a variety of water types (deionized, tap, river and sea water). As seen on Fig. 5(a), hydrogels with selective behavior for Cu2+ ions in all media adsorbed 13.11 mg/g, 12.14 mg/g, 11.83 mg/g and 9.47 mg/g Cu2+ ions in deionized, tap, river and sea water, respectively. The hydrogels, which adsorbed less than 1.12 mg/g Co2+, Ni2+, Hg2+, Zn2+, Mn2+, Ba2+, Ca2+,

ro of

Cd2+, Pb2+, Mg2+, and Fe2+ ions in addition to Cu2+ ions, can also be used as selective adsorbent material in all media. According to the obtained results, it can be said that other metal ions enter the hydrogel network structures or are adsorbed at very low amounts in the

-p

hydrogels by secondary interactions. After the adsorption process from the metal ion mixture, only Cu2+ ions were observed in metal ion elemental mapping results for Hydrogel1. This

re

result shows that other metal ions (Co2+, Ni2+, Hg2+, Zn2+, Mn2+, Ba2+, Ca2+, Cd2+, Pb2+, Mg2+,

lP

and Fe2+) adsorbed in hydrogel structure by weak interactions are desorbed by immersion of the hydrogel in deionized water. The elemental mapping result given in Fig. 5(b) supports the fact that TACYC cross-linked hydrogels are highly selective for Cu2+ ions. Again, 100 mg/L

na

(100 mL) ion concentrations were used for adsorption from solutions prepared with single ions in deionized, tap, river and sea water. The time-linked ion amounts adsorbed by

ur

Hydrogel1 are given in Fig. 6. According to Fig. 6, equilibrium adsorption concentration was

Jo

reached in nearly 300 minutes. The adsorption results show Hydrogel1 adsorbed 15.85 mg/g, 14.41 mg/g, 13.25 mg/g and 10.90 mg/g Cu2+ ion amounts from deionized, tap, river and sea water media, respectively. According to these results, the maximum adsorption capacity for p(HEMA-co-TACYC) hydrogels was reduced by other ions dissolved in river and sea water; however, their selectivity for Cu2+ ions was not affected. In the literature, the cross-linked p(RhBHSA – BVD) polymeric structure synthesized by Hu et al. for Cu 2+ions was used for

both qualitative and quantitative ion determination. p(RhBHSA–BVD) which has selective adsorption properties against Cu2+ ions in various aqueous media has an adsorption capacity of approximately 19 mg/g. p(HEMA-co-TACYC) can be described as a well-selected absorbent material with an adsorption capacity of 15.85 mg/g for Cu2+ ions (Hu et al., 2018). While the maximum adsorption capacity of a three-dimensional porous organic framework for Cu2+ was reported as 135.60 mg/g by Li et al. (Li et al., 2019), the maximum adsorption capacity of rice husk-derived double network hydrogel for Cu2+ is 196.68 mg/g (Ma et al.,

ro of

2019). Likewise, maximum adsorption capacities of H-Ge-g-poly (AcA-co-BuMc)/MMT nanocomposite biosorbent (Nematidil and Sadeghi, 2019), SESD-PAA (Zhang et al., 2017) and chitin/Fe3O4 hydrogels (Liao and Huang, 2019) for Cu2+ were reported as 192.4mg/g,

-p

75.4 mg/g and 10.65 mg/g, respectively. The most important disadvantage of these adsorbents is that they are not selective against Cu2+ ions. However, p (HEMA-co-TACYC) hydrogels

re

have excellent selectivity to Cu2+ ions. In addition to selectivity, another advantage of the

lP

p(HEMA-co-TACYC) hydrogel is that it is possible to increase the adsorption capacity by changing the TACYC ratio in the structure.

na

The relationship between the adsorbed Cu2+ amount and equilibrium concentration at fixed temperature using Hydrogel1 was researched using adsorption isotherms. Accordingly,

ur

nearly 100 mg of hydrogel was added to 100 mL Cu2+ solution with 6 different concentrations in the range of 1-100 mg/L. The graph showing the correlation between initial ion

Jo

concentration and equilibrium adsorption amounts is given in Fig. 7(a). According to Fig. 7(a), the increase in initial Cu2+ concentration increased the adsorption amount of the hydrogel, and equilibrated when the Cu2+ concentration was 50 mg/L. Here the amount of TACYC in the copolymeric hydrogel structure is important for the equilibrium concentration of adsorption. Adsorption stops when the active sites in the TACYC compound selective for Cu2+ ions in the hydrogel structure are filled. Additionally, as there are insufficient Cu2+ ions

for maximum complex formation with TACYC compounds in solutions with concentration from 1-25 mg/L, adsorption finishes before all of the active sites in the TACYC compound can be filled by Cu2+ ions. The Langmuir and Freundlich equations are the two of the most frequently chosen isotherm types due to defining relatively simple and reasonably accurate adsorption isotherms. The basic assumption of the Langmuir model represents single-layer adsorption occurring on a homogeneous surface. It is assumed there is no interaction or competition

ro of

between molecules adsorbed in an adsorption region. After a region is filled, no further adsorption processes occur in that region. The Freundlich isotherm is generally appropriate for nonideal adsorption on heterogeneous surfaces. It is assumed adsorption is continuous

-p

with an increase in the concentration of the adsorbate amount.

re

The equilibrium relationships between adsorbent and adsorbate are obtained with linear form for the Langmuir and Freundlich adsorption isotherms in Equations 2 and 3 (Ozay et al.,

na

lP

2009).

(Eq. 2) (Eq. 3)

Accordingly, the Langmuir and Freundlich adsorption isotherms and data obtained

ur

from the equations are given in Fig. 7(b) and Fig. 7(c). The Ce/qe value on Fig. 7(b) is

Jo

graphed according to variation in Ce value and calculation of the slope of the line (1/qm) and intersection point (1/KLqm) are used to give the qm and KL constants, respectively. The maximum adsorption capacity of the adsorbent is represented by q m (mg/g) and KL represented the Langmuir binding constant (L/mg). On Fig. 7(c), the lnqe value is graphed against the change in lnCe value and the slope of the line (1/n) and intersection (lnK F) give the n and KF constants, respectively. KF represents adsorption capacity (mg/g) and n

represents adsorption ability. If the value of n >1, it represents compatible adsorption conditions (Ozay et al., 2009; Tu et al., 2017). The constant values calculated from the graphs are given in Table 2. The fit of the Langmuir and Freundlich isotherms is determined by the correlation coefficient (R2). The correlation coefficient (R2 = 0.978) for the Langmuir equation shows better fit to the experimental data for adsorption compared to the Freundlich isotherm, confirming there is homogeneous distribution of active regions in a single layer on the hydrogel surface. Additionally, the calculated n value determines appropriate adsorption.

ro of

The pH value of the solution is very important for the adsorption of the pollutant species from aqueous solutions. The pH of the Cu2+ ions solution was changed in the range of 2-5 to examine the change in the adsorption of Cu2+with Hydrogel1 with pH. The obtained

-p

results were given in Fig. 8. According to Fig. 8, 11.21 mg/g adsorption value was obtained at pH = 2, while the highest adsorption value was obtained at pH = 4 and pH = 5. The cause of

re

decrease in the amount of Cu2+ adsorbed at pH=2 is probably the decrease in the complex

cyclen ring at low pH values.

lP

formation with Cu2+ ions as a result of some protonation of the nitrogen donor atoms of the

The reuse of material designed for environmental uses is important in terms of cost. In

na

terms of repeat usability, polymers, especially hydrogels insoluble in water, are very advantageous materials. As seen on Fig. 9(a), the p(HEMA-co-TACYC) hydrogels used as

ur

both sensor and adsorbent material by forming a complex with Cu2+ ions were first treated

Jo

with acid to ensure desorption of Cu2+ ions and then prepared for reuse in alkaline media. Hydrogels taken from the alkaline medium were washed in deionized water until the medium reached neutral pH and then used for new applications. The values obtained for Hydrogel1 used 5 times for Cu2+ adsorption in aqueous media are given in Fig. 9(b). Accordingly, even at the end of the 5th use of Hydrogel1, maximum adsorption capacity of 14.22 mg/g was found. The nearly 11% reduction in adsorption capacity of the hydrogel is considered to be

due to negligible hydrolysis of HEMA in the hydrogel structure in a basic medium and degradation of some of the chains.

4. Conclusions In recent times, design of materials with specific properties for environmental applications has gained importance. Multifunctional materials that only interact with environmental pollutants, and that can be used to determine their presence and to remove

ro of

them from the medium with adsorption are very limited in the literature. It is only possible to produce these types of smart materials with engineering studies in the synthesis stage. The pioneering concept in our study is the conceptualization of transferring the copper ion binding

-p

ability of 1,4,7,10-tetraazacyclododecane compound into the hydrogel network structure. With this transfer, the aim was to produce an insoluble material that can be used multiple

re

times without immobilization in the network structure. Thus, the obtained TACYC compound

lP

acted as both functional monomer and crosslinker. The hydrogels acting selectively for copper ions created in our study will be pioneers for production of specially-designed hydrogels and polymeric materials in the literature. Again, within the scope of this study, a new type of

na

material acting in all aqueous media present on the Earth’s surface and both determining copper ions and adsorbing them was produced. Changing the TACYC amount in the

ur

p(HEMA-co-TACYC) hydrogel structure may increase the maximum Cu2+ ion amounts that

Jo

can be adsorbed. Additionally, the hydrogel structures synthesized in macro dimensions can be reduced to nano dimensions and used for more rapid determination and adsorption. Our group continues work on this topic.

Author Contribution Hava Ozay: Synthesis and characterization studies, experimental studies, writing original draft Zeynep Gungor: Synthesis and characterization studies, experimental studies Betul Yilmaz: Synthesis and characterization studies, experimental studies Pinar İlgin: Experimental studies, adsorption isotherms, writing original draft

ro of

Ozgur Ozay: Synthesis and characterization studies, experimental studies, writing original draft

REFERENCES

Abozeid, S. M., Snyder, E. M., Lopez, A. P., Steuerwald, C. M., Sylvester, E., Ibrahim K.

-p

M., Zaky, R. R., Abou-El-Nadar, H. M., Morrow, J. R., 2018. Nickel(II) Complexes as

re

Paramagnetic Shift and paraCEST Agents. Eur. J. Inorg. Chem. 18, 1902–1908. https://doi.org/10.1002/ejic.201800021.

lP

Anand, T., Sahoo, S. K., 2019. Cost-effective approach to detect Cu(II) and Hg(II) by integrating a smartphone with the colorimetric response from a NBD-benzimidazole based

na

dyad. Phys.Chem.Chem.Phys. 21, 11839–11845. https://doi.org/10.1039/c9cp00002j.

sensing

ur

Arunbabu, D., Sannigrahi, A., Jana, T., 2011. Photonic crystal hydrogel material for the of

toxic

mercury ions

(Hg2+)

in

water.

Soft

Matter

7,

2592−2599.

Jo

https://doi.org/10.1039/C0SM01136C. Awual, M. R., 2019. Mesoporous composite material for efficient lead(II) detection and removal

from

aqueous

media.

https://doi.org/10.1016/j.jece.2019.103124.

J.

Environ.

Chem.

Eng.

7,

103124.

Ayaz, M., Muhammad, A., Younas, M., Khan, A. L., Rezakazemi, M., 2019. Enhanced Water Flux by Fabrication of Polysulfone/Alumina Nanocomposite Membrane for Copper(II) Removal. Macromol. Res. 27, 565−571. https://doi.org/10.1007/s13233-019-7086-4. Bereczki, H. F., Daroczi, L., Fabian, I., Lazar, I., 2016. Sol-gel synthesis, characterization and catalytic activity of silica aerogels functionalized with copper(II) complexes of cyclen and cyclam.

Microporous

Mesoporous

Mater.

234,

392−400.

ro of

https://doi.org/10.1016/j.micromeso.2016.07.026. Bezzina, J. P., Ruder, L. R., Dawson, R., Ogden, M. D., 2019. Ion exchange removal of Cu(II), Fe(II), Pb(II) and Zn(II) from acid extracted sewage sludge e Resin screening in weak

-p

acid media. Water Res. 158, 257−267. https://doi.org/10.1016/j.watres.2019.04.042.

Bilardi, S., Calabro, P. S., Moraci, N., 2019. The removal efficiency and long-term hydraulic

re

behavior of zero valent iron/lapillus mixtures for the simultaneous removal of Cu2+, Ni2+ and

lP

Zn2+. Sci. Total Environ. 675, 490−500. https://doi.org/10.1016/j.scitotenv.2019.04.260. Carreira-Barral, I., Mato-Iglesias, M., Blas, A., Platas-Iglesias, C., Tasker, P. A., Esteban-

na

Gómez, D., 2017. Ditopic receptors containing urea groups for solvent extraction of Cu(II) salts. Dalton Trans. 46, 3192–3206. https://doi.org/10.1039/C7DT00093F.

ur

Chen, J., Li, Y., Zhong, W., Hou, Q., Wang, H., Sun, X., Yi, P., 2015. Novel fluorescent

Jo

polymeric nanoparticles for highly selective recognition of copper ion and sulfide anion in water. Sens. Actuators, B 206, 230–238. https://doi.org/10.1016/j.snb.2014.09.034. Chin, K. O. A., Morrow, J. R., Lake, C. H., Churchill, M. R., 1994. Synthesis and solution properties of lanthanum(III), europium(III), and lutetium(III) THP complexes and an x-ray diffraction study of a crystal containing four stereoisomers of a europium(III) THP complex (THP= 1,4,7,10-tetrakis(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane). Methyl groups

impart rigidity to S,S,S,S-THP macrocyclic complexes. Inorg. Chem. 33, 656−664. https://doi.org/10.1021/ic00082a008. Cuggino, J. C., Charles, G., Gatti, G., Strumia, M. C., Igarzabal, C. I. A., 2013. New hydrogel obtained from a novel dendritic monomer as a promising candidate for biomedical applications.

J.

Biomed.

Mater.

Res.

Part

A

101,

3372−3381.

https://doi.org/10.1002/jbm.a.34640.

ro of

Dai, H., Zhang, Y., Ma, L., Zhang, H., Huang, H., 2019. Synthesis and response of pineapple peel carboxymethyl cellulose-g-poly(acrylic acid-co-acrylamide)/graphene oxide hydrogels. Carbohydr. Polym. 215, 366−376. https://doi.org/10.1016/j.carbpol.2019.03.090.

-p

El-hoshoudy, A. N., Mohammedy, M. M., Ramzi , M., Desouky, S. M., Attia, A.M., 2019. Experimental, modeling and simulation investigations of a novel surfmer-co-poly acrylates

re

crosslinked hydrogels for water shut-off and improved oil recovery. J. Mol. Liq. 277,

lP

142−156. https://doi.org/10.1016/j.molliq.2018.12.073.

Głowińska, A., Trochimczuk, A. W., Jakubiak-Marcinkowska,

A., 2019. Novel

na

acrylate/organophosphorus-based hydrogels for agricultural applications. New outlook and innovative concept for the use of 2-(methacryloyloxy)ethyl phosphate as a multi-purpose

ur

monomer. Eur. Polym. J. 110. 202−210. https://doi.org/10.1016/j.eurpolymj.2018.11.020.

Jo

Guo, Y., Jia, Z., Shi, Q., Liu, Z., Wang, X., Li, L., 2019. Zr (IV)-based coordination porous materials for adsorption of Copper(II) from water. Microporous Mesoporous Mater., 285, 215−222. https://doi.org/10.1016/j.micromeso.2019.05.020. He, X., Chen, P., Zhang, J., Luo, T. Y., Wang, H. J., Liu, Y. H., Yu, X. Q., 2019. Cationic polymer-derived carbon dots for enhanced gene delivery and cell imaging. Biomater. Sci. 7, 1940–1948. https://doi.org/10.1039/C8BM01578C.

Hu, C. C., Gao, Q., Liu, S., Chang, L. L., Xia, K. S., Han, B., Zhou, C. G., 2018. Crosslinked poly(ionic liquid) anchored with organic probe as a new promising platform for organic solvent-free recognition, quantification, and selective removal of heavy metal ion. Chem. Eng J. 346, 458–465. https://doi.org/10.1016/j.cej.2018.03.185. Hubin, T. J., Walker, A. N., Davilla, D. J., Freeman T. N. C., Epley, B. M., Hasley, T. R., Amoyaw, P. N. A., Jain, S., Archibald, S. J., Prior, T. J., Krause, J. A., Oliver, A. G., Tekwani, B. L., Khan M. O. F., 2019. Tetraazamacrocyclic derivatives and their metal as

antileishmanial

leads.

Polyhedron,

163,

42–53.

ro of

complexes

https://doi.org/10.1016/j.poly.2019.02.027

-p

Ilgin, P., Ozay, O., Ozay, H., 2019a. A novel hydrogel containing thioether group as selective support material for preparation of gold nanoparticles: Synthesis and catalytic applications.

re

Appl. Catal., B 241, 415−423. https://doi.org/10.1016/j.apcatb.2018.09.066.

lP

Ilgin, P., Ozay, H., Ozay, O., 2019b. Selective adsorption of cationic dyes from colored noxious effluent using a novel N-tert-butylmaleamic acid based hydrogels. React. Funct.

na

Polym. 142, 189−198. https://doi.org/10.1016/j.reactfunctpolym.2019.06.018. Jeevica, A., Shankaran, D. R., 2016. Functionalized silver nanoparticles probe for visual sensing

of

mercury.

Mater.

Res.

Bull.

83,

48−55.

ur

colorimetric

Jo

https://doi.org/10.1016/j.materresbull.2016.05.029. Joseph, L., Jun, B. M., Flora, J. R. V., Park, C. M., 2019. Removal of heavy metals from water sources in the developing world using low-cost materials: A review. Chemosphere 229, 142−159. https://doi.org/10.1016/j.chemosphere.2019.04.198. Jung, K. W., Lee, S. Y., Choi, J. W., Lee, Y. J., 2019. A facile one-pot hydrothermal synthesis of hydroxyapatite/biochar nanocomposites: Adsorption behavior and mechanisms for the

removal

of

copper(II)

from

aqueous

media.

Chem.

Eng.

J.

369,

529−541.

https://doi.org/10.1016/j.cej.2019.03.102. Koike, T., Watanabe, T., Aoki, S., Kimura, E., Shiro, M., 1996. Novel Biomimetic Zinc(II)Fluorophore,

Dansylamidoethyl-Pendant

Tetraazacyclododecane

(Cyclen).

J.

Macrocyclic Am.

Chem.

Tetraamine Soc.

118,

1,4,7,1012696-12703.

https://doi.org/10.1021/ja962527a.

ro of

Krakovský, I., Kouřilová, H., Hrubovský, M., Labuta, J., Hanyková, L., 2019. Thermoresponsive double network hydrogels composed of poly(N-isopropylacrylamide) and polyacrylamide.

Eur.

Polym.

J.

415−424.

-p

https://doi.org/10.1016/j.eurpolymj.2019.04.032.

116.

Li, Q., Song, H., Han, R., Wang, G., Li, A., 2019. Efficient removal of Cu(II) and citrate

re

complexes by combined permanent magnetic resin and its mechanistic insights. Chem. Eng. J.

lP

366, 1−10. https://doi.org/10.1016/j.cej.2019.02.070.

Li, W.-T., Zhuang, Y.-T., Wang, J.-Y., Yang, T., Yu, Y.-L., Chen, M.-L., Wang, J.-H., 2019.

and

Copper

na

A Three-Dimensional Porous Organic Framework for Highly Selective Capture of Mercury Ions.

ACS

Appl.

Polym.

Mater.

10,

2797-2806.

ur

https://doi.org/10.1021/acsapm.9b00804. Liao, J., Huang, H., 2019. Magnetic chitin hydrogels prepared from Hericium erinaceus

Jo

residues with tunable characteristics: A novel biosorbent for Cu2+ removal. Carbohydr. Polym. 220, 191−201. https://doi.org/10.1016/j.carbpol.2019.05.074. Liu, H., Yu, D., Zhou, K., Wang, S., Luo, S., Li, L., Wang, W., Song, Q., 2018. Novel pHsensitive photopolymer hydrogel and its holographic sensing response for solution

characterization.

Opt.

Laser

Technol.

101,

257−267.

https://doi.org/10.1016/j.optlastec.2017.11.025. Liu, M., Wen, Y., Song, X., Zhu, J. L., Li, J., 2019. A smart thermoresponsive adsorption system for efficient copper ion removal based on alginate-g-poly(N-isopropylacrylamide) graft

copolymer.

Carbohydr.

219,

Polym.

280−289.

https://doi.org/10.1016/j.carbpol.2019.05.018.

ro of

Liu, Y., Gao, Q., Li, C., Liu, S., Xia, K., Han, B., Zhou, C., 2019. Fabrication of Organic Probe Decorated Water-Soluble Polymer Chains on Natural Fibers for Selective Detection and Efficient Removal of Hg2+ Ions in Pure Aqueous Media. ACS Appl. Polym. Mater. 1,

-p

2680−2691. https://doi.org/10.1021/acsapm.9b00631.

Ma, J., Li, T., Liu, Y., Cai, T., Wei, Y., Dong, W., Chen, H., 2019. Rice husk derived double

multicomponent

systems.

Bioresour.

Technol.

290,

121793.

lP

and

re

network hydrogel as efficient adsorbent for Pb(II), Cu(II) and Cd(II) removal in individual

https://doi.org/10.1016/j.biortech.2019.121793.

na

Martinez M. V., Rivarola, C. R., Miras, M. C., Barbero, C. A., 2017. A colorimetric iron sensor based on the partition of phenanthroline complexes into polymeric hydrogels.

ur

Combinatorial synthesis and high throughput screening of the hydrogel matrix. Sens.

Jo

Actuators, B 241, 19−32. https://doi.org/10.1016/j.snb.2016.10.013 Müntener, T., Thommen, F., Joss, D., Kottelat, J., Prescimone, A., Haussinger, D., 2019. Synthesis of chiral nine and twelve-membered cyclic polyamines from natural building blocks. Chem. Commun. 55, 4715−4718. https://doi.org/10.1039/C9CC00720B.

Nematidil, N., Sadeghi, M., 2019. Fabrication and characterization of a novel biosorbent and its evaluation as adsorbent for heavy metal ions. Polym. Bull. 76, 5103–5127. https://doi.org/10.1007/s00289-018-2646-x. Ozay, H., Baran, Y., Miyamae H., 2011. The stabilities and formation kinetics of some macrocycles with copper(II): crystal structures of some pendant arm macrocycles. J. Coord. Chem. 64, 1469–1480. https://doi.org/10.1080/00958972.2011.574128.

ro of

Ozay H., Ozay O., 2013. Rhodamine based reusable and colorimetric naked-eye hydrogel sensors for Fe3+ ion. Chem. Eng. J. 232, 364−371. https://doi.org/10.1016/j.cej.2013.07.111. Ozay, H., Sahin, O., Koc, O. K., Ozay H., 2016. The preparation and applications of novel

-p

phosphazene crosslinked thermo and pH responsive hydrogels. J. Ind. Eng. Chem. 43, 28−35.

re

https://doi.org/10.1016/j.jiec.2016.07.043.

Ozay, O., Ekici, S., Baran, Y., Aktas, N., Sahiner, N., 2009. Removal of toxic metal ions with

lP

magnetic hydrogels. Water Res. 43, 4403−4411. https://doi.org/10.1016/j.watres.2009.06.058. Ozay, O., Ekici, S., Baran, Y., Kubilay, S., Aktas, N., Sahiner, N., 2010. Utilization of

na

magnetic hydrogels in the separation of toxic metal ions from aqueous environments.

ur

Desalination 260, 57−64. https://doi.org/10.1016/j.desal.2010.04.067. Pérez-Toro, I., Domínguez-Martín, A., Choquesillo-Lazarte, D., Vílchez-Rodríguez, E.,

Jo

González-Pérez, J. M., Castiñeiras, A., Niclós-Gutiérrez, J., 2015. Lights and shadows in the challenge of binding acyclovir, a synthetic purine-like nucleoside with antiviral activity, at an apical–distal coordination site in copper(II)-polyamine chelates. J. Inorg. Biochem. 148, 84– 92. https://doi.org/10.1016/j.jinorgbio.2015.03.006. Pujales-Paradela, R., Savić, T., Pérez-Lourido, P., Esteban-Gómez, D., Angelovski, G., Botta, M., Platas-Iglesias, C., 2019. Lanthanide Complexes with 1H paraCEST and 19F Response for

Magnetic

Resonance

Imaging

Applications.

Inorg.

Chem.

58,

7571−7583.

https://doi.org/10.1021/acs.inorgchem.9b00869. Qing, Z., Mao, Z., Qing, T., He, X., Zou, Z., He, D., Shi, H., Huang, J., Liu, J., Wang, K., 2014. Visual and Portable Strategy for Copper(II) Detection Based on a Striplike Poly(Thymine)-Caged and Microwell-Printed Hydrogel. Anal. Chem. 86, 11263−11268. https://doi.org/10.1021/ac502843t.

ro of

Rahman, A. B., Imafuku, H., Miyazawa, Y., Kafle, A., Sakai, H., Saga, Y., Aoki, S., 2019. Catalytic Hydrolysis of Phosphate Monoester by Supramolecular Phosphatases Formed from a Monoalkylated Dizinc(II) Complex, Cyclic Diimide Units, and Copper(II) in Two-Phase System.

Inorg.

Chem.

https://doi.org/10.1021/acs.inorgchem.8b03586.

58,

5603−5616.

-p

Solvent

re

Samaddar, P., Kumar, S., Kim, K. H., 2019. Polymer Hydrogels and Their Applications

lP

Toward Sorptive Removal of Potential Aqueous Pollutants. Polym. Rev. 59, 418−464. https://doi.org/10.1080/15583724.2018.1548477.

na

Sasakura, K., Hanaoka ,K., Shibuya, N., Mikami, Y., Kimura, Y., Komatsu, T., Ueno, T., Terai, T., Kimura, H., Nagano, T., 2011. Development of a highly selective fluorescence for

hydrogen

sulfide.

J.

Am.

Chem.

Soc.

133,

18003–18005.

ur

probe

Jo

https://doi.org/10.1021/ja207851s. Sedghi, R., Heidari, B., Behbahani, M., 2015. Synthesis, characterization and application of poly(acrylamide-co-methylenbisacrylamide) nanocomposite as a colorimetric chemosensor for visual detection of trace levels of Hg and Pb ions. J. Hazard. Mater. 285, 109−116. https://doi.org/10.1016/j.jhazmat.2014.11.049.

Shen, Y., Wang, Q., Wang, Y., He, Y. F., Song, P., Wang, R. M., 2019. Itaconic copolymer modified loess for high efficiently removing copper ions from wastewater. J. Dispersion Sci. Technol. 40, 794−801. https://doi.org/10.1080/01932691.2018.1480387. Tamesue, S., Endo, T., Ueno, Y., Tsurumak, F., 2019. Sewing Hydrogels: Adhesion of Hydrogels Utilizing in Situ Polymerization of Linear Polymers inside Gel Networks. Macromolecules 52, 5690−5697. https://doi.org/10.1021/acs.macromol.9b01084.

ro of

Thombare, N., Mishra, S., Siddiqui, M. Z., Jha, U., Singh, D., 2018. Design and development of guar gum based novel, superabsorbent and moisture retaining hydrogels for agricultural applications. Carbohydr. Polym. 185, 169−178. https://doi.org/10.1016/j.carbpol.2018.01.018.

-p

Tsebrikova, G. S., Polyakova, I. N., Solov’ev, V. P., Ivanova, I. S., Kalashnikova, I. P., Kodina, G. E., Baulin, V. E., Tsivadze, A. Y., 2018. Complexation of the new

re

tetrakis[methyl(diphenylphosphorylated)] cyclen derivative with transition metals: First

lP

examples of octacoordinate zinc(II) and cobalt(II) complexes with cyclen molecules. Inorg. Chim. Acta 478, 250–259. https://doi.org/10.1016/j.ica.2018.04.007.

na

Tu, H., Yu, Y., Chen, J., Shi, X., Zhou, J., Deng, H., Du, Y., 2017. Highly cost-effective and high-strength hydrogels as dye adsorbents from natural polymers: chitosan and cellulose.

ur

Polym. Chem. 8, 2913−2921. https://doi.org/ 10.1039/C7PY00223H. Wang, D. E., Wang, Y., Tian, C., Zhang, L., Han, X., Tu, Q., Yuan, M., Chen, S., Wang, J.,

Jo

2015. Polydiacetylene liposome-encapsulated alginate hydrogel beads for Pb2+ detection with enhanced

sensitivity.

J.

https://doi.org/10.1039/C5TA04480D.

Mater.

Chem.

A.

3,

21690−21698.

Wang, M. Q., Li, K., Hou, J. T., Wu, M. Y., Huang, Z., Yu, X. Q., 2012. BINOL-Based Fluorescent Sensor for Recognition of Cu(II) and Sulfide Anion in Water. J. Org. Chem. 77, 8350−8354. https://doi.org/10.1021/jo301196m. Wang, L., Ye, Y., Lykourinou, V., Yang, J., Angerhofer, A., Zhao, Y., Ming, L. J., 2017. Catalytic Cooperativity, Nuclearity, and O2/H2O2 Specificity of Multi-Copper(II) Complexes of Cyclen-Tethered Cyclotriphosphazene Ligands in Aqueous Media. Eur. J. Inorg. Chem.

ro of

4899–4908. https://doi.org/10.1002/ejic.201700811. Wen, T., Zhao, Y., Zhang, T., Xiong, B., Hu, H., Zhang, Q., Song, S., 2019. Effect of anions species on copper removal from wastewater by using mechanically activated calcium

-p

carbonate. Chemosphere 230, 127−135. https://doi.org/10.1016/j.chemosphere.2019.04.213. Yang, K., Zeng, M., 2013. Multiresponsive hydrogel based on polyacrylamide functionalized

re

with thymine derivatives. New J. Chem. 37, 920−926. https://doi.org/10.1039/C3NJ41013G.

lP

Ye, B. F., Zhao, Y. J., Cheng, Y., Li, T. T., Xie, Z. Y., Zhao, X. W., Gu, Z. Z., 2012. Colorimetric photonic hydrogel aptasensor for screening of heavy metal ions. Nanoscale 4,

na

5998−6003. https://doi.org/10.1039/C2NR31601C. Yin, Y. X., Wen, J. H., Geng Z. R., Li, Y. Z., Wang, Z. L., 2012. Two heptadentate Co(III)

ur

and Mn(III) complexes with partially deprotonated cyclen derivative bearing four

Jo

hydroxypropyl pendants: structure, DNA binding and DNA cleavage. Appl. Organometal. Chem. 26, 671–680. https://doi.org/10.1002/aoc.2905. Zhang, M., Song, L., Jiang, H., Li, S., Shao, Y., Yang, J., Li, J., 2017. Biomass based hydrogel as an adsorbent for the fast removal of heavy metal ions from aqueous solutions. J. Mater. Chem. A 5,3434–3446. https://doi.org/10.1039/C6TA10513K.

Zhao, L., Chen, J., Xiong, L., Bai, Y., Yilihamu, A., Ma, Q., Yang, S., Wu, D., Yang, S. T., 2019. Carboxylation as an effective approach to improve the adsorption performance of graphene

materials

for

Cu2+

removal.

Sci.

Total

Environ.

682,

591−600.

https://doi.org/10.1016/j.scitotenv.2019.05.190. Zhou, G., Wang, Y., Zhou, R., Wang, C., Jin, Y., Qiu, J., Hua, C., Cao, Y., 2019. Synthesis of amino-functionalized bentonite/CoFe2O4@MnO2 magnetic recoverable nanoparticles for aqueous

Cd2+

removal.

Sci.

Total

Environ.

-p re lP na ur Jo

505−513.

ro of

https://doi.org/10.1016/j.scitotenv.2019.05.218.

682,

Figure Captions

Fig. 1. Synthesis reaction of the TACYC monomer. Fig. 2. (a) Solution color of TACYC exposed to various types of metal ions (b) Absorption spectra of TACYC in the presence of metal ions, (c) Metal ion competition on sensor properties of TACYC for Cu2+ (1: Cu2+, 2: Co2+, 3: Ni2+, 4: Zn2+, 5: Hg2+, 6: Fe2+, 7: Fe3+, 8: Cd2+, 9: Pb2+, 10: Mn2+, 11: Ca2+, 12: Ba2+, 13: Mg2+).

ro of

Fig. 3. SEM image of p(HEMA-co-TACYC) Networks (a) before adsorption, (b) after adsorption (c) proposed sensing mechanism for hydrogel−Cu2+ complex, (d) UV–Vis spectra of metal ion adsorbed p(HEMA-co-TACYC) hydrogel, (e) the metal ion competition on

2+

-p

sensor properties of p(HEMA-co-TACYC) hydrogel [1: p(HEMA-co-TACYC)-Cu2+, 2-14: n+

re

p(HEMA-co-TACYC)-Cu +M (2: Co2+, 3: Ni2+, 4: Zn2+, 5: Hg2+, 6: Fe2+, 7: Cd2+, 8: Fe3+, 9: Pb2+, 10: Mn2+, 11: Ca2+, 12: Ba2+, 13: Mg2+ , 14: all metal ions)].

lP

Fig. 4. Digital camera images of sensor applications for hydrogels, (a) p(HEMA-co-TACYC) hydrogel and p(HEMA) (control), (b) copper ion selectivity of p(HEMA-co-TACYC)

na

hydrogels and color changes of p(HEMA)-Cu2+, p(AMPS)-Cu2+, (c) in the presence of different metal ions for p(HEMA-co-TACYC) (Metal ion concentrations: 100 ppm, 100 mL),

ur

(d) in presence of different concentration of Cu2+ (100 mL). Fig. 5. Metal ion selectivity of Hydrogel1 in various water samples (100 mg/L (100 mL), total

Jo

other metals=Mn2+, Ba2+, Ca2+, Cd2+, Pb2+) (b) Cu2+ elemental mapping in Hydrogel1 after the adsorption of Cu2+ from metal ion mixture. Fig. 6. The adsorption isotherms of Hydrogel1 for various water samples (100 mg/L (100 mL) Cu2+).

Fig. 7. (a) The effect of initial concentration of Cu2+ on adsorption of Hydrogel1. (b) Langmuir and (c) Freundlich plots for the adsorption of Cu2+ (100 mg Hydrogel1).

Fig. 8. The effect of pH of Cu2+ on adsorption with Hydrogel1 (100 mg/L (100 mL) Cu2+).

Fig. 9. (a) The reuse conditions of Hydrogel1 and (b) five consecutive adsorption desorption

Jo

ur

na

lP

re

-p

ro of

cycles of Hydrogel1 for Cu2+ ions (100 mg/L (100 mL) Cu2+).

ro of

-p

re

lP

na

ur

Jo

ro of

-p

re

lP

na

ur

Jo

ro of

-p

re

lP

na

ur

Jo

ro of

-p

re

lP

na

ur

Jo

ro of

-p

re

lP

na

ur

Jo

ro of

-p

re

lP

na

ur

Jo

ro of

-p

re

lP

na

ur

Jo

ro of

-p

re

lP

na

ur

Jo

HEMA (mmol)

TACYC (mmol)

Hydrogel1

15

0.500

Hydrogel2

15

Hydrogel3

H2O

Swelling %

TEMED (µL)

Gelation (%)

0.2

57.28

50

90.9

0.120

0.2

62.11

50

87.4

15

0.060

0.2

63.55

50

86.1

Hydrogel4

15

0.030

0.2

64.06

50

83.8

Hydrogel5

15

0.015

0.2

66.62

50

81.3

(mL)

ro of

Hydrogel Code

-p

Table 1: The synthesis compositions of p(HEMA-co-TACYC) hydrogels.

re

Table 2: Adsorption isotherm parameters of Cu2+ with p(HEMA-co-TACYC) hydrogels. Langmuir isotherm constants Metal ion 0.175

17.241

Jo

ur

na

Cu2+

qmax (mg/g)

R2

lP

KL (L/mg)

0.978

Freundlich isotherm constants Kf

n

R2

2.394

1.866

0.678