Chitosan Composite for Adsorption and

Article pubs.acs.org/IECR

Graphitic Carbon Nitride/Chitosan Composite for Adsorption and Electrochemical Determination of Mercury in Real Samples Mandana Amiri,* Haneie Salehniya, and Aziz Habibi-Yangjeh Department of Chemistry, University of Mohaghegh Ardabili, Daneshgah Street, 11365-9161 Ardabil, Iran

Ind. Eng. Chem. Res. 2016.55:8114-8122. Downloaded from pubs.acs.org by DUQUESNE UNIV on 09/27/18. For personal use only.

S Supporting Information *

ABSTRACT: In this research, graphitic carbon nitride (g-C3N4) was synthesized using pyrolysis of melamine and its phase, morphology, composition, and structure were characterized by using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, energy dispersive analysis of X-rays, and FT-IR spectroscopy. The modification of carbon paste electrode with g-C3N4/chitosan composite has been performed using the casting method. Experimental results demonstrated the superb adsorptive properties of g-C3N4/chitosan composite through Hg(II). Differential pulse voltammetry (DPV) was applied for quantitative determinations. The linear calibration curves is obtained in the ranges of 1.0 × 10−6to 8.0 × 10−5 mol L−1 and 1.0 × 10−7 to 5.0 × 10−6 mol L−1. The proposed protocol can offer a highly selective and sensitive method for the detection of Hg(II) with a detection limit of 1.0 × 10−8 mol L−1. Determination of Hg(II) was performed in the presence of Fe(II) and Cu(II). Finally, the modified electrode has been applied for sensitive determination of Hg(II) in real samples.

■

INTRODUCTION Graphitic carbon nitride (g-C3N4), as an analogue of graphene, has attracted many interests recently. It can be as the best candidate to complement carbon materials.1 Many reports described the structure of g-C3N4 as a poly(tri-s-triazine), but the accurate structure of g-C3N4 is not clear yet. The conjugated aromatic tri-s-triazine polymer-like graphene tends to form p-conjugated planar layers2,3 Due to its exceptional optical, thermal, electrical, mechanical, and chemical inert properties, g-C3N4 has drawn a huge attraction and is found in many applications, such as lithium-ion battery,4 water splitting,5−7 fuel cells,8 degradation of pollutants,9−11 conversion of carbon dioxide to fuels,12 NO decomposition,13 hydrogenation reactions,14 fluorescent sensor,15 and SPME fiber coating.1Recently, application of g-C3N4 in electrochemical sensors has been reported by a few researchers.16−19 Chemically modified carbon-paste electrodes found wide application in electroanalysis. These electrodes catalyze the redox processes by reducing overpotential and increasing current. Chemically modified carbon-paste electrodes have many advantages such as easy preparation, simple renewability, low background current, and wide potential window.20 They are low cost and compatible with different modifiers such as nanostructures,21 Schiff base complexes,22 zeolites,23 and biological compounds.24 As literature survey, there is no report on using g-C3N4 as modifier in cabon paste electrode. Preconcentrating chemically modified electrodes, in which their surfaces were designed for binding and reacting of target analytes, are an excellent candidate for chemical sensing.25 The electrostatic interaction or coordination binding is the most © 2016 American Chemical Society

probable mechanism of preconcentrating to collect the analyte.26,27 Mercury is a hazardous pollutant, a highly toxic heavy metal, for environment and human health. It can cause serious health problems in kidney, nervous system, and gastrointestinal tract.28,29 Many different analytical techniques such as atomic fluorescence spectroscopy,30 atomic absorption spectroscopy,31 inductively coupled plasma atomic emission spectrometry,32 and inductively coupled plasma mass spectrometry33 have been employed for selective and sensitive measurement of Hg(II). These techniques are expensive, complicated, time-consuming and need expert operators and sample preparation. On the other hand, electrochemical techniques that are sensitive, simpler and need less expensive equipment have been widely used for trace analysis of Hg(II) as promising and elegant techniques.28,34−37 Chitosan (CH) (poly D-glucosamine) shows excellent high water permeability, film-forming ability, and good adhesion. CH is a biodegradable polymer with a wide range of applications, for instance, in food additive, membrane technology, water treatment, biomedical devices, catalyst support, drug delivery, and analytical applications.38 It has been added to graphene, graphene oxide, and graphite oxide to improve the properties of nanocomposites39−41 to adsorbe dyes and heavy metals.42,43 There are several reports on application Received: Revised: Accepted: Published: 8114

May 3, 2016 June 16, 2016 July 1, 2016 July 18, 2016 DOI: 10.1021/acs.iecr.6b01699 Ind. Eng. Chem. Res. 2016, 55, 8114−8122

Article

Industrial & Engineering Chemistry Research Scheme 1. Postulated Condensation of Melamine

Figure 1. Schematic preparation of g-C3N4/CH suspension.

of CH films in electroanalysis as binder of carbon nanoparticles in determination of hydroquinone derivatives23 and immobilization of proteins in carbon structures.44 We applied g-C3N4 as modifier of carbon paste electrode surface for the first time. Melamine as the precursor for direct

synthesis of g-C3N4 by pyrolysis approach has been used. Characterization of g-C3N4 has been performed using different techniques. Here, CH is employed as a polycationic binder to create a film from g-C3N4 by improving the properties of modifier such as adhesion and stability. The electrochemical 8115

DOI: 10.1021/acs.iecr.6b01699 Ind. Eng. Chem. Res. 2016, 55, 8114−8122

Article

Industrial & Engineering Chemistry Research

effective for swelling and then exfoliating the bulk g-C3N4 into ultrathin nanosheets (see Figure 1). According to the literature, the dispersed ultrathin g-C3N4 nanosheets were negatively charged. Because of the highly negative surface charge, the solution of ultrathin g-C3N4 nanosheets is stable.46 So it may be concluded that positively charged CH can be settled between exfoliated sheets of g-C3N4. The g-C3N4/CH electrodes were prepared by casting 20 μL of the suspension onto a polished carbon paste electrode (3 mm diameter), and then the solvent was evaporated under air. CH is a polysaccharide biopolymer and exhibits outstanding film forming, good adhesion, and high water permeability. It can improve the adhesion of g-C3N4 at the surface of CPE. The electrode surface of CPE has been prepared before every experiment by casting of g-C3N4/CH suspension on it. The mechanical and electrochemical properties of electrode improved in the presence of CH because it behaves as a binder and separating nanosheets. The characterization of prepared modified electrode (MCPE) was performed using cyclic voltammetry techniques (CV) and electrochemical impedance spectroscopy (ESI).

sensing ability of the g-C3N4 through Hg(II) has been studied. Finally, differential pulse voltammetry has been applied for sensitive determination of Hg(II) in real samples.

■

EXPERIMENTAL SECTION Apparatus. A galvanostat/potentiostat μ-Autolab3 was employed for electrochemical impedance spectroscopic (ESI) experiments. A voltammetric analyzer (Metrohm Computrace, 797 VA) was employed for voltammetric experiments. A carbon paste electrode (3 mm diameter CPE), a Pt wire as the counter electrode, and a KCl saturated calomel reference electrode (SCE) have been applied in a conventional three electrode system. The buffer solutions as the supporting electrolyte were prepared using a pH meter (Metrohm). Diffuse reflectance spectroscopy (DRS) was obtained by spectrophotometer model Sinco S4100, Korea. A Philips Xpert X-ray diffractometer with Cu Kα radiation (λ = 0.154 06 nm) was used to obtain the X-ray diffraction (XRD) patterns, and the scanning rate was 0.04 deg/s (2θ range from 10° to 80°). The structural morphology of the electrodes was investigated using scanning electron microscopy (SEM) (Hitachi S-4800 ultrahigh resolution) coupled with energy dispersive X-ray spectroscopy (EDS) (S4800). The transmission electron microscopy (TEM) image was obtained by a Zeiss-EM10C instrument with an acceleration voltage of 80 kV. The Fourier transform infrared (FT-IR) spectra were recorded using a PerkinElmer Spectrum RX I apparatus. Reagents. Melamine, HgCl2, K4Fe(CN)6, K3Fe(CN)6 and K2HPO4, CH3COOK, CH3COOH, and H3PO4 were purchased from Merck and were of analytical-reagent grade. Phosphate buffer solution, pH 2.0 (0.1 M), as supporting electrolyte was prepared using KH2PO4 and H3PO4. Doubly distilled water has been used for preparation of all solutions. Synthesis of g-C3N4. The g-C3N4 powder was synthesized by heating melamine powder up to 520 °C for 4 h according to the literature method45 (Scheme 1) and characterized by different techniques. Preparation of Modified Electrode. After optimization of the ratio of graphite powder to binder, unmodified carbon paste electrode (CPE) was prepared by hand mixing the graphite powder and Nujol in a ratio 75:25 (w/w)46 in an agate mortar, using a pestle, and then homogenized by dissolving in dichloromethane. The mixture was stirred until all the solvent evaporated. The paste was kept at room temperature for 24 h before using. A portion of the resulting homogeneous paste was packed into the cave of the Teflon tube (∼2.5 mm i.d.). A copper wire was fixed to a graphite rod and inserted into the Teflon body, which served to establish electrical contact with the external circuit. The electrodes have been polished on a paper to obtain a shiny and smooth surface. An amount of 3 mg of medium molecular weight CH was dispersed in 10 mL of 3% acetic acid. An amount of 1 mL was taken from this stock solution followed by addition of 3 mg of the g-C3N4 and with further addition of ethanol/water mixture (2:1). The suspension was then stirred and dispersed with ultrasonic probe for 2 h. The amounts of g-C3N4 and CH have been optimized. The dispersion and stability decreased with increasing amount of g-C3N4 by more than the optimized amount, and the less than optimized one causes a decrease of the response. In the optimum amount of CH, suitable dispersion, longer stability of suspension, and good response have been achieved. In that case, the polar solvents will be

■

RESULTS AND DISCUSSION Characterization of g-C3N4. Phase structure of the resultant g-C3N4 was studied by XRD pattern, and the result along with its standard pattern is displayed in Figure 2A. The pristine g-C3N4 has two strong diffraction peaks at about 27.3°

Figure 2. (A) XRD pattern of g-C3N4 along with the standard pattern. (B) EDX spectrum of g-C3N4. 8116


Article


Figure 3. (A) SEM and (B) TEM images of g-C3N4.

and 13.1° corresponding to the characteristic interplanar stacking and the interlayer structural packing, respectively.8 Figure 2B shows the EDX spectrum for the g-C3N4 sample. As can be seen, the pristine g-C 3 N 4 displays the peaks corresponding to C and N elements. Surface morphology of the g-C3N4 was characterized by SEM and TEM techniques. The SEM image of the as-prepared sample shows relatively regular sheetlike morphologies (Figure 3A). Moreover, the sheetlike morphology of the sample was also confirmed using TEM technique, and the image is shown in Figure 3B. FT-IR spectrum has been recorded for synthesized g-C3N4 (see Figure 4). For pristine g-C3N4, the bands in the range of

Figure 5. Cyclic voltammograms of K4Fe(CN)6, 5 mM, containing 0.1 M KCl at the surface of unmodified (CPE, solid line) and modified carbon paste electrode with MCPE.

the other hand, at the surface of MCPE, the anodic peak at a lower positive potential near 0.35 V with peak current 284 μA is recorded. Such increasing of the anodic peak current coupled with decreasing of the overpotential at the surface of the modified electrode indicates that MCPE could enhance the kinetics of the electron transfer. Electrochemical impedance spectroscopy is applied to study the impedance of the surface of MCPE and CPE. Figure 6 presents the Nyquist plots of (a) CPE, (b) MCPE in 5.0 mM Fe(CN)64− (5 mM) /Fe(CN)63− (5 mM) containing 0.1 M KCl. The Nyquist plots include a semicircular part at high frequency zone which is related to the electron transfer kinetic limitations (Rct) of the electrochemical reaction, and a linear part at lower frequency zone corresponds to the diffusioncontrolled electrode process. It is obvious that the diameter of semicircle decreased at MCPE and the electron transfer at its surface is amplified significantly compared with CPE. Voltammetric Study of Hg(II) at the Surface of CPE and MCPE. To evaluate the electrochemical sensing ability of the g-C3N4 through Hg(II), after modification of carbon paste electrode, the voltammetric behavior of Hg(II) at the surface of MCPE has been investigated. Figure 7 indicates the electrochemical behavior of 1 × 10 −5 M Hg(II) at the surface of electrode (dashed line) and MCPE (solid line) using cyclic voltammetry (CV) in phosphate buffer, pH 2.0. The peak potentials for oxidation of Hg are approximately 0.28 V and

Figure 4. FT-IR spectrum of g-C3N4.

1230−1650 cm−1 are corresponding to the stretching vibrations of C−N and CN in heterocycles. Furthermore, the band at 806 cm−1 is related to the breathing mode of the heptazine arrangement. The broad absorption band at 3000−3300 cm−1 is due to the terminal NH2 or NH groups at the defect sites of g-C3N4 aromatic rings.8 Electrochemical Study of MCPE and CPE. Cyclic voltammograms of 5 mM solution of Fe(CN)64− containing 0.1 M KCl as supporting electrolyte at the surface of MCPE (solid line) and CPE (dashed line) have been shown in Figure 5. At the surface of CPE, Fe(CN)64− exhibits an oxidation peak potential at approximately 0.37 V and peak current 164 μA. On 8117


Article


with reducing peak potential has been observed. It can be correlated to a decreasing of the overpotential of the process at the surface of the MCPE, indicating that the MCPE acts as an effective promoter to enhance the rate of the electron transfer. It can be suggested that the presented modified electrode acts as preconcentrating chemically modified electrode with gC3N4 surface designed for reacting and binding of Hg(II). It holds great promise for chemical sensing of Hg(II) by coordination reaction for collecting of it. As it has been reported in a previous work, the interaction between heavy metal ions and the functional groups of the gC3N4 was explained by an innersphere surface complexation mechanism.47 Barman et al. have used fluorescent quenching of graphitic-carbon nitride quantum dots by Hg2+ for highly selective determination of mercury. They suggested that Hg2+ ions bind with the carbon nitride framework via covalent bonding, losing the structural integrity of the sheets. It has been claimed the larger radius of Hg2+ ion, higher tendency of Hg2+ ions toward nitrogen, and formation of a complex with graphitic-carbon nitride quantum dots which is energetically favorable cause unique selectivity for Hg2+ ions toward graphitic-carbon nitride quantum dots.48 According to the results of this work, we also can explain the selective tendency of g-C3N4 to Hg2+ with respect to obtained results. To prove the interaction between g-C3N4 and Hg2+, DRS and ATR spectroscopy has been employed. Comparison between DRS spectra of g-C3N4 and g-C3N4 with adsorbed Hg2+ indicates that a new broad peak appeared near 500 nm in the presence of Hg2+ (see Figure S1 in Supporting Information) which can be related to charge transfer from C3N4 to Hg2+.49 It can be evidence that shows interaction between Hg2+ and g-C3N4. ATR spectroscopy has been also applied to investigate the interaction. ATR spectra in Figure S2 for g-C3N4 and g-C3N4 with adsorbed Hg2+ have been shown. It can be seen that two new peaks appear in 633 and 478 cm−1 which are assigned to Hg−N bonds which can confirm the interaction between Hg2+ and g-C3N4.50 Effect of pH. Generally, pH plays an important role in electrochemical processes. Voltammetric investigations were performed in the pH range between 1.0 and 8.0 in solutions containing 1.0 × 10 −5 M Hg(II) at the surface of MCPE. In pH ranges from 6.0 to 8.0 and pH under 2.0 no anodic peak is observed (see Figure S3). It can be concluded the adsorption of Hg(II) on MCPE will be promoted or suppressed correspond-

Figure 6. Nyquist plots (Z″ versus Z′) for the EIS measurements of (a) CPE and (b) MCPE in 5 mM K4Fe(CN)6/K3Fe(CN)6 + 0.1 M KCl at the formal potential of 0.2 V and frequency range of 0.01− 1000.000 Hz.

Figure 7. Cyclic voltammograms of 1 × 10 −5 M Hg(II) in phosphate buffer of pH 2 at the surface of CPE (solid line) and MCPE (dashed line). Scan rate is 100 mV/s.

0.23 V with peak currents of 9.84 μA and 65.5 μA at the surface of CPE and MCPE, respectively. An enhancement in current

Figure 8. (A) Cyclic voltammograms of 1 × 10 −5 M Hg(II) in phosphate buffer of pH 2.0 at the surface of MCPE at various scan rates (bottom to top: 10, 20, 40, 60, 80, 100, 150, and 200 mV s−1). (B) Relationship between peak current and scan rate. 8118


Article


(R2 = 0.9972), and Ipa (μA) = 0.231C (μM) + 0.252 (R2 = 0.9946). The limit of detection of Hg(II) was found to be 1.0 × 10−8 mol·L−1. Table 1 compares some electrochemical methods which exist in literature for determination of Hg. The presented modified electrode exhibits the good analytical results, and also it is less expensive than most of the electrodes used previously. It has also an easy fabrication method compared to some of the complicated electrodes in Table 1. However, the gold electrodes provide sensitive and selective analyses; they are expensive and suffer from passivation (fouling of surface) problem. Thus, gold electrodes need rigorous cleaning procedures before each measurement. On the other hand, carbon paste electrode is a low-cost, user-friendly, and easily renewable electrode material. It could be valuable that the presented method does not need the stripping step compared to most of the former reported methods used for electrochemical determination of Hg. Determination of Hg(II) in the Presence of Fe(II) and Cu(II). Pesticides and fertilizers may simultaneously contain Hg(II), Cu(II), Pb(II), Cd(II), Fe(II), and Zn(II).55 They are transferred to water and soil and cause the permanent pollutants. It can be concluded that the most important interfering species56 are Cu(II) and Fe(II) in voltammetric determination of Hg (II). So a sensitive and accurate analytical procedure for determining Hg(II) in the presence of Cu(II) and Fe(II) at trace levels is needed. The proposed method can present a sensitive and selective method for determination of Hg(II) in the presence of Cu(II) and Fe(II). Figure 10 shows the differential pulse voltammograms of the Hg(II) in the presence of Cu(II) and Fe(II) in two ranges of calibrations (insets Figure 10A and Figure 10B). Interference Study. The selectivity and utility of the proposed method were investigated in the presence of coexisting ions. For this purpose, the interference of various ions was tested in optimized conditions by adding them to the solution containing 1.0 × 10−5 M Hg(II). The tolerable limit was defined as the foreign ion concentration that gave an error of less than ±5.0% in the determination of 1.0 × 10−5 M Hg(II). Experimental results showed no interference was observed for ions with a 500-fold excess of Co2+, Pb2+, Ca2+, Na+, and Mg2+, a 200-fold excess of Fe2+, a 100-fold excess of Ni2+, and a 10-fold excess of Cd2+, Cu2+. Repeatability and Reproducibility. To investigate the reproducibility of MCPE, differential pulse voltammograms of two concentration levels of Hg(II) (1.0 × 10−6 M and 5.0 × 10−5 M) in buffer solution, pH 2.0, have been recorded for 10 repeated measurements. The RSD for Hg(II) determination, based on the 10 replicates of measurments, were 0.76% and 2.3% for 1.0 × 10−6 M and 5.0 × 10−5 M, respectively. Real Samples. The reliability of the recommended procedure was examined by applying the proposed method to the determination of Hg(II) in two water samples. Determination of Hg(II) in water samples was examined with MCPE. The first water sample was found from local river water (Balekhlo Chai River, Ardabil, Iran). It is revealed that no Hg(II) was detected with MCPE. The second water sample was found from lake water (Shorabil Lake, Ardabil, Iran). The water samples were diluted 5 times. For determination of Hg(II) concentration in real samples the standard addition method was employed and the recoveries were obtained by spiking. The slopes of the standard addition curves were 0.2716 μA/μM and 0.2809 μA/μM (the range of standard concentrations that were

ing to the changes of pH values. At neutral and basic pHs, mercury hydroxide will be formed, so there is no Hg2+ at the surface to produce the signal. At pH 1.0, the surface of g-C3N4 may be protonated and the interaction decreases significantly. pH 2.0 phosphate buffer was chosen as the supporting electrolyte for further studies because the maximum Ip was recorded for pH 2.0. Effect of Potential Scan Rate. At various scan rates (0.01, 0.02, 0.04, 0.06, 0.08, 01, 015, 0.2 V s−1), cyclic voltammograms have been recorded in 1 × 10 −5 M Hg(II) in a buffered solution of pH 2.0 at the surface of the MCPE (see Figure 8A). The relation between peak currents and scan rates is approximately linear (see eq 1). The adsorption controlled mechanism can be suggested for Hg oxidation (see Figure 8B). Ipa (μA) = 4.73υ (V s−1) + 0.607;

R2 = 0.9916

(1)

These experimental results with spectroscopic results which are discussed perviously confirmed adsorption properties of gC3N4 through Hg(II). Calibration Curve. DPV was used for quantitative determination of the Hg(II) (Figure 9). A linear relation was shown between oxidation peak currents and the concentration of Hg(II) in the ranges of 1.0 × 10−6 to 8.0 × 10−5 and 1.0 × 10−7 to 5.0 × 10−6 mol·L−1 (insets of Figure 9A and Figure 9B). The linear equations are Ipa (μA) = 0.2661C (μM) − 0.0223

Figure 9. DPV of various concentrations of Hg(II) at the surface of MCPE: (A) (bottom to top) 1 × 10−6, 3 × 10−6, 5 × 10−6, 8 × 10−6, 1 × 10−5, 3 × 10−5, 5 × 10−5, 8 × 10−5 M; (B) (bottom to top) 5 × 10−8, 3 × 10−8, 1 × 10−8, 1 × 10−7, 3 × 10−7, 5 × 10−7, 8 × 10−7, 1 × 10−6, 3 × 10−6, 5 × 10−6 M; in 0.1 M phosphate buffer (pH 2.0), 50 mV pulse amplitude, 5 mV step potential, 0.05 s step time. 8119


Article

Industrial & Engineering Chemistry Research Table 1. Some Voltammetric Measurements That Exist in Literature for Determination of Hg(II)

a

electrode

method

LOD (μmol L−1)

linear range (μmol L−1)

ref

Au-NPs/CNTs AuNPs/CFMEa SbFEb AuNPs-SPCEs ssDNA/Au electrode BT-SBA/CPEc BIM/MCNF/Nafion/GCEd plant refuse/CPE utg-C3N4/GCE g-C3N4−CH/CPE

DPASV DPASV ASV SWASV DPV DPASV DPASV SV ASV DPV

0.0003 0.0004 0.002 0.004 0.100 0.400 0.0003 0.280 0.0001 0.010

0.0005−1.25 0.001−0.25 0.012−0.40 0.025−0.010 0.100−2.00 2.00−9.97 0.005−0.500 0.500−5.00 0.0005−0.08 1.00−80.0, 0.100−5.00

35 28 36 37 50 51 52 53 54 this work

Gold nanoparticles decorated carbon fiber mat electrode. bAntimony film electrode. cBT, 2-benzothiazolethiol; SBA, SBA-15 mesoporous silica. Bis(indolyl)methane/mesoporous carbon nanofiber/Nafion/glassy carbon electrode.

d

■

CONCLUSION We have demonstrated a highly sensitive and selective electrochemical sensor for the determination of Hg(II) based on interaction between Hg(II) and g-C3N4 nanosheets. DRS and ATIR spectroscopy has been applied to confirm the interaction. This research suggests also that designed and modified electrode might be a very promising basis for analytical sensing of Hg(II) in real samples.

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.iecr.6b01699. DRS spectra, ATR spectra, and cyclic voltammograms (PDF)

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Tel: +98-45-33514703. Fax: +98-45-33514701. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS The authors gratefully acknowledge the support of this work by University of Mohaghegh Ardabili Research Council, Ardabil, Iran.

■

Figure 10. DPV of various concentrations of Hg(II) at the surface of MCPE in the presence of Cu(II) 5 × 10−5 M and Fe(II) 5 × 10−4 M: (A) (bottom to top) 1 × 10−7, 3 × 10−7, 5 × 10−7, 8 × 10−7, 1 × 10−6, 3 × 10−6, 5 × 10−6 M; (B) (bottom to top) 1 × 10−6, 3 × 10−6, 5 × 10−6, 8 × 10−6, 1 × 10−5, 3 × 10−5, 5 × 10−5, 8 × 10−5 M; in phosphate buffer pH 2; scan rate 50 mV s−1; pulse amplitude 50 mV; step potential 5 mV; modulation time 25 mV.

spiked was 1.0 × 10−6 to 8.0× 10−5 M) with correlation coefficients 0.9951 and 0.9894, and the recoveries of 98.65% and 102.03% were found with the presented method for first and second water samples, respectively. It is demonstrated that the method is suitable for sensitive and selective determination of Hg(II) in real water samples. 8120

NOMENCLATURE AND ABBREVIATIONS A = surface area of the electrode C0* = concentration CV = cyclic voltammetry CPE = carbon paste electrode D0 = diffusion coefficient DPV = differential pulse voltammetry Ep = peak potential E0 = formal redox potential F = Faraday constant Ip = peak current LOD = limit of detection LOQ = limit of quantification n = number of electrons transferred in the reaction R = gas constant RSD = relative standard deviation SEM = scanning electron microscopy T = temperature DOI: 10.1021/acs.iecr.6b01699 Ind. Eng. Chem. Res. 2016, 55, 8114−8122

Article

Industrial & Engineering Chemistry Research υ = scan rate

■

(19) Ma, H.; Wang, Y.; Zhang, H.; Wu, D.; Guo, A.; Yan, T.; Wei, Q.; Du, B. A sensitive electrochemical immunosensor for the detection of squamous cell carcinoma antigen by using PtAu nanoparticles loaded on TiO2 colloidal spheres as labels. RSC Adv. 2015, 5 (74), 59853− 59860. (20) Amiri, M.; Rezapour, F.; Bezaatpour, A. Hydrophilic carbon nanoparticulates at the surface of carbon paste electrode improve determination of paracetamol, phenylephrine and dextromethorphan. J. Electroanal. Chem. 2014, 735, 10−18. (21) Amiri, M.; Alimoradi, M.; Nekoueian, K.; Bezaatpour, A. Cobalt Flower-like Nanostructure as Modifier for Electrocatalytic Determination of Chloropheniramine. Ind. Eng. Chem. Res. 2012, 51 (44), 14384−14389. (22) Amiri, M.; Pakdel, Z.; Bezaatpour, A.; Shahrokhian, S. Electrocatalytic determination of Sumatriptan on the surface of carbon-paste electrode modified with a composite of cobalt/Schiffbase complex and carbon nanotube. Bioelectrochemistry 2011, 81 (2), 81−85. (23) Amiri, M.; Sohrabnezhad, S.; Rahimi, A. Nickel (II) incorporated AlPO-5 modified carbon paste electrode for determination of thioridazine in human serum. Mater. Sci. Eng., C 2014, 37, 342−347. (24) Rittmannsberger, A.; Likussar, W.; Michelitsch, A. Development of an enzyme-modified carbon paste electrode for determining inhibitors of lipoxygenase. Biosens. Bioelectron. 2005, 21 (4), 655−660. (25) Wang, J. Analytical Electrochemistry; Wiley, 2006. (26) Amiri, M.; Shahrokhian, S.; Psillakis, E.; Marken, F. Electrostatic accumulation and determination of triclosan in ultrathin carbon nanoparticle composite film electrodes. Anal. Chim. Acta 2007, 593 (1), 117−122. (27) Gaichore, R. R.; Srivastava, A. K. Voltammetric determination of nifedipine using a β-cyclodextrin modified multi-walled carbon nanotube paste electrode. Sens. Actuators, B 2013, 188, 1328−1337. (28) Li, D.; Li, J.; Jia, X.; Wang, E. Gold nanoparticles decorated carbon fiber mat as a novel sensing platform for sensitive detection of Hg(II). Electrochem. Commun. 2014, 42, 30−33. (29) Zahir, F.; Rizvi, S. J.; Haq, S. K.; Khan, R. H. Effect of methyl mercury induced free radical stress on nucleic acids and protein: Implications on cognitive and motor functions. Indian J. Clin. Biochem. 2006, 21 (2), 149−152. (30) Zu, W.; Wang, Z. Ultra-trace determination of methylmercuy in seafood by atomic fluorescence spectrometry coupled with electrochemical cold vapor generation. J. Hazard. Mater. 2016, 304, 467−473. (31) Berzas Nevado, J. J.; Rodríguez Martín-Doimeadios, R. C.; Guzmán Bernardo, F. J.; Jiménez Moreno, M. Determination of monomethylmercury in low- and high-polluted sediments by microwave extraction and gas chromatography with atomic fluorescence detection. Anal. Chim. Acta 2008, 608 (1), 30−37. (32) Zhu, X.; Alexandratos, S. D. Determination of trace levels of mercury in aqueous solutions by inductively coupled plasma atomic emission spectrometry: Elimination of the ‘memory effect’. Microchem. J. 2007, 86 (1), 37−41. (33) López, I.; Cuello, S.; Cámara, C.; Madrid, Y. Approach for rapid extraction and speciation of mercury using a microtip ultrasonic probe followed by LC−ICP-MS. Talanta 2010, 82 (2), 594−599. (34) Afkhami, A.; Bagheri, H.; Khoshsafar, H.; Saber-Tehrani, M.; Tabatabaee, M.; Shirzadmehr, A. Simultaneous trace-levels determination of Hg(II) and Pb(II) ions in various samples using a modified carbon paste electrode based on multi-walled carbon nanotubes and a new synthesized Schiff base. Anal. Chim. Acta 2012, 746, 98−106. (35) Xu, H.; Zeng, L.; Xing, S.; Shi, G.; Xian, Y.; Jin, L. Microwaveradiated synthesis of gold nanoparticles/carbon nanotubes composites and its application to voltammetric detection of trace mercury(II). Electrochem. Commun. 2008, 10 (12), 1839−1843. (36) Dal Borgo, S.; Jovanovski, V.; Hocevar, S. B. Antimony film electrode for stripping voltammetric measurement of Hg(II) in the presence of Cu(II). Electrochim. Acta 2013, 88, 713−717. (37) Bernalte, E.; Marín Sánchez, C.; Pinilla Gil, E. Gold nanoparticles-modified screen-printed carbon electrodes for anodic

REFERENCES

(1) Xu, N.; Wang, Y.; Rong, M.; Ye, Z.; Deng, Z.; Chen, X. Facile preparation and applications of graphitic carbon nitride coating in solid-phase microextraction. J. Chromatogr A 2014, 1364, 53−58. (2) Wang, Y.; Wang, X.; Antonietti, M. Polymeric Graphitic Carbon Nitride as a Heterogeneous Organocatalyst: From Photochemistry to Multipurpose Catalysis to Sustainable Chemistry. Angew. Chem., Int. Ed. 2012, 51 (1), 68−89. (3) Hu, R.; Wang, X.; Dai, S.; Shao, D.; Hayat, T.; Alsaedi, A. Application of graphitic carbon nitride for the removal of Pb(II) and aniline from aqueous solutions. Chem. Eng. J. 2015, 260, 469−477. (4) Hou, Y.; Li, J.; Wen, Z.; Cui, S.; Yuan, C.; Chen, J. N-doped graphene/porous g-C3N4 nanosheets supported layered-MoS2 hybrid as robust anode materials for lithium-ion batteries. Nano Energy 2014, 8, 157−164. (5) Ahmad, H.; Kamarudin, S. K.; Minggu, L. J.; Kassim, M. Hydrogen from photo-catalytic water splitting process: A review. Renewable Sustainable Energy Rev. 2015, 43, 599−610. (6) Xu, J.; Li, Y.; Peng, S.; Lu, G.; Li, S. Eosin Y-sensitized graphitic carbon nitride fabricated by heating urea for visible light photocatalytic hydrogen evolution: the effect of the pyrolysis temperature of urea. Phys. Chem. Chem. Phys. 2013, 15 (20), 7657−7665. (7) Li, Y.; Xiang, Y.; Peng, S.; Wang, X.; Zhou, L. Modification of Zrdoped titania nanotube arrays by urea pyrolysis for enhanced visiblelight photoelectrochemical H2 generation. Electrochim. Acta 2013, 87, 794−800. (8) Zheng, Y.; Liu, J.; Liang, J.; Jaroniec, M.; Qiao, S. Z. Graphitic carbon nitride materials: controllable synthesis and applications in fuel cells and photocatalysis. Energy Environ. Sci. 2012, 5 (5), 6717−6731. (9) Dong, G.; Zhang, Y.; Pan, Q.; Qiu, J. A fantastic graphitic carbon nitride (g-C3N4) material: Electronic structure, photocatalytic and photoelectronic properties. J. Photochem. Photobiol., C 2014, 20, 33− 50. (10) Cao, S.; Low, J.; Yu, J.; Jaroniec, M. Polymeric Photocatalysts Based on Graphitic Carbon Nitride. Adv. Mater. 2015, 27 (13), 2150− 2176. (11) Zhu, J.; Xiao, P.; Li, H.; Carabineiro, S. A. C. Graphitic Carbon Nitride: Synthesis, Properties, and Applications in Catalysis. ACS Appl. Mater. Interfaces 2014, 6 (19), 16449−16465. (12) Ye, S.; Wang, R.; Wu, M.-Z.; Yuan, Y.-P. A review on g-C3N4 for photocatalytic water splitting and CO2 reduction. Appl. Surf. Sci. 2015, 358, 15−27. (13) Sano, T.; Tsutsui, S.; Koike, K.; Hirakawa, T.; Teramoto, Y.; Negishi, N.; Takeuchi, K. Activation of graphitic carbon nitride (gC3N4) by alkaline hydrothermal treatment for photocatalytic NO oxidation in gas phase. J. Mater. Chem. A 2013, 1 (21), 6489−6496. (14) Wang, Y.; Yao, J.; Li, H.; Su, D.; Antonietti, M. Highly Selective Hydrogenation of Phenol and Derivatives over a Pd@Carbon Nitride Catalyst in Aqueous Media. J. Am. Chem. Soc. 2011, 133 (8), 2362− 2365. (15) Rong, M.; Lin, L.; Song, X.; Wang, Y.; Zhong, Y.; Yan, J.; Feng, Y.; Zeng, X.; Chen, X. Fluorescence sensing of chromium (VI) and ascorbic acid using graphitic carbon nitride nanosheets as a fluorescent “switch”. Biosens. Bioelectron. 2015, 68, 210−217. (16) Medeiros, R. A.; Matos, R.; Benchikh, A.; Saidani, B.; Debiemme-Chouvy, C.; Deslouis, C.; Rocha-Filho, R. C.; FatibelloFilho, O. Amorphous carbon nitride as an alternative electrode material in electroanalysis: Simultaneous determination of dopamine and ascorbic acid. Anal. Chim. Acta 2013, 797, 30−39. (17) Liu, Y.; Wang, Q.; Lei, J.; Hao, Q.; Wang, W.; Ju, H. Anodic electrochemiluminescence of graphitic-phase C3N4 nanosheets for sensitive biosensing. Talanta 2014, 122, 130−134. (18) Zhang, H.; Huang, Q.; Huang, Y.; Li, F.; Zhang, W.; Wei, C.; Chen, J.; Dai, P.; Huang, L.; Huang, Z.; Kang, L.; Hu, S.; Hao, A. Graphitic carbon nitride nanosheets doped graphene oxide for electrochemical simultaneous determination of ascorbic acid, dopamine and uric acid. Electrochim. Acta 2014, 142, 125−131. 8121


Article


Application to the analysis of natural water sediments. Talanta 1987, 34 (12), 1001−1007.

stripping voltammetric determination of mercury in ambient water samples. Sens. Actuators, B 2012, 161 (1), 669−674. (38) Rassaei, L.; Sillanpäa,̈ M.; Marken, F. Modified carbon nanoparticle-chitosan film electrodes: Physisorption versus chemisorption. Electrochim. Acta 2008, 53 (19), 5732−5738. (39) Yang, X.; Tu, Y.; Li, L.; Shang, S.; Tao, X.-m. Well-Dispersed Chitosan/Graphene Oxide Nanocomposites. ACS Appl. Mater. Interfaces 2010, 2 (6), 1707−1713. (40) Cheng, Q.; Duan, J.; Zhang, Q.; Jiang, L. Learning from Nature: Constructing Integrated Graphene-Based Artificial Nacre. ACS Nano 2015, 9 (3), 2231−2234. (41) Wan, S.; Peng, J.; Li, Y.; Hu, H.; Jiang, L.; Cheng, Q. Use of Synergistic Interactions to Fabricate Strong, Tough, and Conductive Artificial Nacre Based on Graphene Oxide and Chitosan. ACS Nano 2015, 9 (10), 9830−9836. (42) Travlou, N. A.; Kyzas, G. Z.; Lazaridis, N. K.; Deliyanni, E. A. Graphite oxide/chitosan composite for reactive dye removal. Chem. Eng. J. 2013, 217, 256−265. (43) Li, X.; Zhou, H.; Wu, W.; Wei, S.; Xu, Y.; Kuang, Y. Studies of heavy metal ion adsorption on chitosan/sulfydryl-functionalized graphene oxide composites. J. Colloid Interface Sci. 2015, 448, 389−97. (44) Tsai, Y.-C.; Chen, S.-Y.; Liaw, H.-W. Immobilization of lactate dehydrogenase within multiwalled carbon nanotube-chitosan nanocomposite for application to lactate biosensors. Sens. Actuators, B 2007, 125 (2), 474−481. (45) Akhundi, A.; Habibi-Yangjeh, A. Novel magnetically separable gC3N4/AgBr/Fe3O4 nanocomposites as visible-light-driven photocatalysts with highly enhanced activities. Ceram. Int. 2015, 41 (4), 5634−5643. (46) Amiri, M.; Bezaatpour, A.; Pakdel, Z.; Nekoueian, K. Simultaneous voltammetric determination of uric acid and ascorbic acid using carbon paste/cobalt Schiff base composite electrode. J. Solid State Electrochem. 2012, 16 (6), 2187−2195. (47) Shen, C.; Chen, C.; Wen, T.; Zhao, Z.; Wang, X.; Xu, A. Superior adsorption capacity of g-C3N4 for heavy metal ions from aqueous solutions. J. Colloid Interface Sci. 2015, 456, 7−14. (48) Barman, S.; Sadhukhan, M. Facile bulk production of highly blue fluorescent graphitic carbon nitride quantum dots and their application as highly selective and sensitive sensors for the detection of mercuric and iodide ions in aqueous media. J. Mater. Chem. 2012, 22 (41), 21832. (49) Fukuzumi, S.; Kochi, J. K. Mercury(II) electrophiles as electron acceptors. Charge-transfer complexes with organometal and aromatic donors. J. Phys. Chem. 1981, 85 (6), 648−654. (50) Han, D.; Kim, Y.-R.; Oh, J.-W.; Kim, T. H.; Mahajan, R. K.; Kim, J. S.; Kim, H. A regenerative electrochemical sensor based on oligonucleotide for the selective determination of mercury(ii). Analyst 2009, 134 (9), 1857−1862. (51) Cesarino, I.; Marino, G.; Matos Jdo, R.; Cavalheiro, E. T. Evaluation of a carbon paste electrode modified with organofunctionalised SBA-15 nanostructured silica in the simultaneous determination of divalent lead, copper and mercury ions. Talanta 2008, 75 (1), 15−21. (52) Liao, Y.; Li, Q.; Wang, N.; Shao, S. Development of a new electrochemical sensor for determination of Hg(II) based on Bis(indolyl)methane/Mesoporous carbon nanofiber/Nafion/glassy carbon electrode. Sens. Actuators, B 2015, 215, 592−597. (53) Devnani, H.; Satsangee, S. Voltammetric trace determination of mercury using plant refuse modified carbon paste electrodes. Environ. Monit. Assess. 2013, 185 (11), 9333−9342. (54) Zhang, J.; Zhu, Z.; Di, J.; Long, Y.; Li, W.; Tu, Y. A Sensitive Sensor for trace Hg2+ Determination Based on Ultrathin g-C3N4 Modified Glassy Carbon Electrode. Electrochim. Acta 2015, 186, 192− 200. (55) Locatelli, C.; Melucci, D. Voltammetric determination of ultratrace total mercury and toxic metals in meals. Food Chem. 2012, 130, 460−466. (56) Hátle, M. Determination of mercury by differential-pulse anodic-stripping voltammetry with various working electrodes 8122


Chitosan Composite for Adsorption and

Recommend Documents