Abstract

Adsorption behaviors of methylene blue (MB) from aqueous solution using sunflower stem pith (SSP) as adsorbent were investigated. The effects of adsorption conditions such as adsorption time, initial concentration of MB and dosage of SSP on the detoxification of MB were examined. The equilibrium adsorption data were analyzed using three well-known isotherms: Langmuir, Freundlich and Temkin. The results indicated that the Langmuir isotherm fitted well to the data as compared with another isotherm model. The maximum adsorption capacity calculated by the Langmuir isotherm model was 277 mg/g at 338 K. Kinetic analyses were conducted using pseudo first order, pseudo second order and the Elovich model. The regression results showed that the MB adsorption was described by the pseudo second order model. Different thermodynamic parameters such as Gibb's free energy (ΔGo), standard enthalpy change (ΔHo) and standard entropy change (ΔSo) were also evaluated. The results showed that the detoxification of MB using SSP as adsorbent was feasible, non-spontaneous and exothermic under experimental conditions.

INTRODUCTION

Dyes, as coloring agents, are mainly used in various industries, including pulp and papermaking, textile, printing and packaging industries. Millions of tons of dye wastewater are discharged into the environment each year. Degradation and detoxification of dye from water effluents are greatly concerned in wastewater treatment due to the non-biodegradable properties of dye. There have been some new materials for removal of MB such as polyaniline/γ-alumina nanocomposite (Javadian et al. 2014), starch/poly(alginic acid-cl-acrylamide) nanohydrogel (Sharma et al. 2017) and modified Hibiscus cannabinus fiber (Sharma et al. 2015). MB is one of the most common cationic dyes used in papermaking and textile industries. There are several methods for the removal of MB such as biological oxidation, chemical precipitation, ion exchange, photocatalysis, ozonation, adsorption and other methods (Feng et al. 2012). Adsorption is an economically feasible method for decolourisation and detoxification of the MB among the above methods. Selection of adsorbents is vital to the adsorption. Low cost, high adsorption capacity and short period are the keys to selection criteria for adsorbents. In this decade, biomass materials have become an important adsorbent, used in removal of MB from sewage such as sulfonated tea waste (Ahsan et al. 2018), tobacco stems (Reddy et al. 2017), Typha angustifolia (L.) dead leaves waste (Boumaza et al. 2018), tobacco rob residues (Wang et al. 2018) and other materials. The lower adsorption rate and capacity have limited its usage as an adsorbent. In our previous study, sunflower stem pith (SSP) was used in the detoxification of MB. The effects of various parameters such as dosage of SSP, adsorption time and initial concentration of MB were evaluated. Meanwhile, the isotherms and kinetics studies in the detoxification of MB were also investigated. To ascertain the adsorption mechanisms, the thermodynamic parameters (ΔGo, ΔHo and ΔSo) were also calculated.

MATERIALS AND METHODS

Materials and equipment

The sunflower stem pith was collected from farmland in Zhaoyuan County (China). The SSP was artificially separated from the bark and was continually washed with deionized water to remove impurities and then dried in sunlight until all the moisture was evaporated. Finally, the SSP was cut into 1 cm pieces to use as adsorbent. All of the other reagents were of analytical grade and used without further purification. Deionized water was used throughout all the experiments.

Characterization of adsorbent

The morphology and energy dispersive X-ray (EDX) spectra of SSP before and after MB adsorption was determined by scanning electron microscopy (SEM) (Sigma, Zeiss Co., Germany). The functional groups of SSP before and after MB adsorption were characterized by Fourier transform infrared spectroscopy (Bruker Co., Germany) using the KBr method. The Brunauer-Emmett-Teller (BET) specific surface area, pore volume, and pore size distribution of SSP were measured by an ASAP 2020 surface area and porosity analyzer (Micromeritics Instrument Co., USA).

MB adsorption

The effect of adsorption time on the adsorption capacity of SSP was obtained by contacting 100 mL of MB solution of initial concentration 500 mg/L at preselected times (10 min, 30 min, 60 min, 90 min, 120 min and 180 min), using an orbital shaker at ambient conditions. In the experiments on the effect of dosage SSP, the adsorption and initial concentration of MB were held at 120 min and 500 mg/L, respectively. The SSP at various dosages (0.2 g, 0.4 g, 0.6 g, 0.8 g, 1.0 g) was added into 250 mL Erlenmeyer flasks and then it was vibrated by orbital shaker at room temperature. The experiments for analyzing the effect of initial concentration of MB were a similar process to the above description. At the end of each experiment period, the suspensions were separated by speed filter paper for analyzing the MB concentration using a 722 spectrophotometer, by monitoring the absorbance changes at a maximum adsorption wavelength of 665 nm. The standard working curve (y = 0.1846x + 0.00739) was obtained with a correlation coefficient of 0.99997. The removal percentage was calculated according to Equation (1): 
formula
(1)
where C0 (mg/L) and Ce (mg/L) are the initial MB concentration and equilibrium concentration, respectively. The adsorption capacity of SSP was calculated according to Equation (2): 
formula
(2)
where qe is the adsorption capacity(mg/g), m is the mass of SSP (g) and V is the volume of solution (L), respectively.

MB desorption

A series of different chemical reagents including sulfuric acid (H2SO4), sodium hydroxide (NaOH), sodium chloride (NaCl) and ethanol (C2H5OH) were used as eluents. Batch process was employed for MB desorption. The SSP was loaded with 250 mL MB solution of 300 mg/L at a contact time of 120 min. The SSP adsorbed with MB was washed several times with deionized water to remove unadsorbed MB traces on the surface of the SSP. The desorption experiment was performed at 25 °C for 12 h by using the above listed eluents. Desorption efficiency was calculated by Equations (3) and (4) (Daneshvar et al. 2017): 
formula
(3)
where qe,desorption is the amout of MB desorbed per gram of MB saturated sorbent at equilibrium (mg/g), Cf is the MB concentration in the desorbing solution (mg/L). V is the eluent solution volume(L) and M is the MB saturated SSP weight (g), respectively. 
formula
(4)
where D% is the MB desorption efficiency(%), qe,desorption and qe,sorption are the MB desorption and sorption capacity (mg/g), respectively.

Adsorption isotherm

Adsorption isotherm experiments for MB on SSP at three different preselected temperatures (298 K, 318 K, and 338 K) were carried out, 1 g (over dry) SSP and 100 mL MB solution of varying concentrations (500–5,000 mg/L) were put into an Erlenmeyer flask and then on an orbital shaker for 1 h. Thereafter, the SSP adsorbed with MB was collected and filtered through a speed filter paper. The MB concentrations of the clear filtrate solutions were analyzed by the above methods. The equilibrium sorption capacity (qe) for MB was calculated using Equation (2). The Langmuir, Freundlich, and Temkin adsorption isotherm models were used to fit the above experimental data to find the best isotherm model that can describe the detoxification of MB using SSP as an adsorbent.

Kinetic studies

The effect of temperature on the adsorption kinetics was investigated. SSP (1.0 g over dry) was brought into contact with 100 mL of a 3,000 mg/L MB solution stirred on an orbital shaker at specified temperatures (298 K, 318 K, and 338 K). At preselected times (10, 20, 30, 40, 50, and 60 min), the SSP adsorbed with MB were collected and filtered through speed filter paper and the MB concentrations of the resulting clear filtrate solutions were analyzed. The pseudo first order, pseudo second order, and Elovich models were employed to fit the above experimental data.

RESULTS AND DISCUSSION

Effect of contact time

As illustrated in Figure 1(a), the removal percentage and the adsorption capacity increased gradually with contact time and then became stable. The removal percentage of MB was very fast and most of the MB was adsorbed during the first 10 min; the removal percentage of MB reached 95.65%. The adsorption equilibrium was attained in 1.5 h, and the maximum adsorption capacity of the SSP was 47.93 mg/g. The higher adsorption capacity was attributed to the high specific surface area and active chemical functional group of the SSP. The above properties of SSP were similar to other adsorbents which have been reported in the literature such as Sargassum hemiphyllum (Liang et al. 2017), swede rape straw (Feng et al. 2012) and Typha angustifolia (L.) dead leaves (Boumaza et al. 2018).

Figure 1

Effect of operating on MB removal percentage and adsorption capacity, (a) effect of contact time. Initial MB concentration = 500 mg/L, amount of MB solution = 100 mL, dosage of SSP = 1 g (over dry); (b) effect of SSP dosage. initial MB concentration = 500 mg/L, amount of MB solution = 100 mL, adsorption time = 120 min; (c) effect of initial concentration of MB. Dosage of SSP = 1 g, amount of MB solution = 100 mL, adsorption time = 120 min.

Figure 1

Effect of operating on MB removal percentage and adsorption capacity, (a) effect of contact time. Initial MB concentration = 500 mg/L, amount of MB solution = 100 mL, dosage of SSP = 1 g (over dry); (b) effect of SSP dosage. initial MB concentration = 500 mg/L, amount of MB solution = 100 mL, adsorption time = 120 min; (c) effect of initial concentration of MB. Dosage of SSP = 1 g, amount of MB solution = 100 mL, adsorption time = 120 min.

Effect of SSP dosage

As shown in Figure 1(b), the removal percentage of MB rapidly increased and then flattened with the increase in dosage of SSP. The maximum removal percentage was 98.92% at an SSP dosage of 1.0 g. The removal capacity of MB almost reduced linearly with the SSP dosage increasing from 0.2 to 1.0 g. The maximum and minimum removal capacity was 172.79 mg/g and 48.26 mg/g, respectively. This was mainly due to the adsorbent having more vacant active adsorption sites under higher SSP dosage conditions (Vaghetti et al. 2008).

Effect of initial concentration of MB

The effect of initial MB concentration on the removal percentage and adsorption capacity of MB ions from aqueous solution is shown in Figure 1(c). It was observed that the removal percentage of MB decreased linearly with an increase in the initial concentration from 500 to 5,000 mg/L. This phenomenon might be due to the adsorption sites of the SSP having been saturated gradually. The adsorption capacity of MB firstly increased linearly and then flattened off as the initial MB concentration increased. The maximum adsorption capacity was 154 mg/g at an initial MB concentration of 3,089 mg/L.

Adsorption kinetics

Adsorption kinetics provides worthy information about the adsorption mechanism of MB. As illustrated in Figure 2(a), the effect of temperature on the adsorption kinetic behaviors of SSP was investigated. The above data were fitted to three well-known kinetic models: pseudo first order, pseudo second order and the Elovich model. The kinetics parameters calculated according to the linear regression are tabulated in Table 1. It can be seen that the correlation coefficients (R2) for the second order kinetics model were greater than 0.999, much larger than the other kinetic models. Therefore, the pseudo second order has been successfully used to describe the adsorption of MB using SSP as adsorbent. Meanwhile, the calculated values (qe,cal) of adsorption capacity for MB were in good agreement with the experimental values (qe,exp). Similar results have been reported where better fitting to the pseudo second order model was found for MB adsorption on different biomass adsorbents such as Caesalpinia ferrea fruits (Carvalho et al. 2018), acid-washed black cumin seed powder (Siddiqui et al. 2018), Eucalyptus sheathiana bark (Afroze et al. 2016), tobacco stem ash (Ghosh & Reddy 2013) and other adsorbents.

Table 1

Kinetics parameters for MB adsorption onto the SSP

Temperature (K) qe exp (mg/g) Pseudo-first-order
 
Pseudo-second-order
 
Elovich
 
k1 (1/min) qe1 cal (mg/g) R2 k2 (g/mg·min) qe2 cal (mg/g) R2 α (mg/g·min) β (g/mg) R2 
298 151.057 0.0801 139.38 0.8481 0.00109 139.38 0.9956 294.515 0.04918 0.9811 
318 189.036 0.0658 180.91 0.7304 0.00121 180.91 0.9900 12129.474 0.06141 0.7549 
338 217.391 0.00652 202.15 0.8728 0.000822 202.15 0.9930 981.040 0.03867 0.9218 
Temperature (K) qe exp (mg/g) Pseudo-first-order
 
Pseudo-second-order
 
Elovich
 
k1 (1/min) qe1 cal (mg/g) R2 k2 (g/mg·min) qe2 cal (mg/g) R2 α (mg/g·min) β (g/mg) R2 
298 151.057 0.0801 139.38 0.8481 0.00109 139.38 0.9956 294.515 0.04918 0.9811 
318 189.036 0.0658 180.91 0.7304 0.00121 180.91 0.9900 12129.474 0.06141 0.7549 
338 217.391 0.00652 202.15 0.8728 0.000822 202.15 0.9930 981.040 0.03867 0.9218 
Figure 2

Kinetic data and equilibrium isotherms adsorption of MB onto SSP at different temperatures.

Figure 2

Kinetic data and equilibrium isotherms adsorption of MB onto SSP at different temperatures.

In addition, the adsorption capacity increased with the rise of adsorption temperature; this phenomenon was consistent with the thermodynamics study.

Adsorption isotherms

To confirm the adsorption mechanism, surface properties of SSP and affinity between SSP and MB, the experimental data (Figure 2(b)) obtained at various temperatures were fixed by the Langmuir, Freundlich and Temkin isotherms and the fitting results are summarized in Table 2. The correlation coefficient (R2) value of the Langmuir isotherm was highest when compared with the other isotherm models and the adsorption capacity value calculated by Langmuir isotherm model was considerably close to the experimental values. The above results revealed that the Langmuir isotherm can describe the adsorption for the MB. The MB was monolayer adsorbed on the surface of the SSP with a finite number of identical adsorption sites (Langmuir 1918). As shown in Table 2, the RL values were found to be between 0 and 1 for the adsorption temperature (298, 318 and 338 K) and indicated that SSP is the most favorable adsorbent for MB (Namasivayam & Kavitha 2002; Naushad et al. 2017). The MB adsorption capacity increased with the increase in the temperature, with the adsorption capacity reaching a maximum of 277 mg/g at 338 K. This illustrated the adsorption process using SSP as an adsorbent is an endothermic reaction.

Table 2

Isotherm parameters for MB adsorption onto SSP

Isotherm model Parameter R2 Equation Linear forms 
Langmuir 298 K qm = 154 mg/g 0.9940 qe = Ce/(0.00846Ce + 7.283)  
b = 0.000326 L/mg 
RL = 0.8543–0.3807 
318 K qm = 232 mg/g 0.9987 qe = Ce/(0.0026Ce + 8.569) 
b = 0.000503 L/mg 
RL = 0.7917–0.2849 
338 K qm = 277 mg/g 0.9955 qe = Ce/(0.00172Ce + 9.087) 
b = 0.000891 L/mg 
RL = 0.6821–0.1836 
Freundlich 298 K K = 2.42 mg/g 0.9575 lnqe = 0.501lnCe + 0.882  
n = 1.996 
318 K K = 0.85 mg/g 0.9844 lnqe = 0.667lnCe − 0.161 
n = 1.515 
338 K K = 0.47 mg/g 0.9913 lnqe = 0.758lnCe − 0.751 
n = 1.319 
Temkin 298 K A = −256.995 0.9835 qe = −256.995 + 49.337Ce  
B = 49.337 
318 K A = −460.157 0.9947 qe = −460.15 + 80.664Ce 
B = 80.664 
338 K A = −603.579 0.9857 qe = −603.579 + 102.539Ce 
B = 102.539 
Isotherm model Parameter R2 Equation Linear forms 
Langmuir 298 K qm = 154 mg/g 0.9940 qe = Ce/(0.00846Ce + 7.283)  
b = 0.000326 L/mg 
RL = 0.8543–0.3807 
318 K qm = 232 mg/g 0.9987 qe = Ce/(0.0026Ce + 8.569) 
b = 0.000503 L/mg 
RL = 0.7917–0.2849 
338 K qm = 277 mg/g 0.9955 qe = Ce/(0.00172Ce + 9.087) 
b = 0.000891 L/mg 
RL = 0.6821–0.1836 
Freundlich 298 K K = 2.42 mg/g 0.9575 lnqe = 0.501lnCe + 0.882  
n = 1.996 
318 K K = 0.85 mg/g 0.9844 lnqe = 0.667lnCe − 0.161 
n = 1.515 
338 K K = 0.47 mg/g 0.9913 lnqe = 0.758lnCe − 0.751 
n = 1.319 
Temkin 298 K A = −256.995 0.9835 qe = −256.995 + 49.337Ce  
B = 49.337 
318 K A = −460.157 0.9947 qe = −460.15 + 80.664Ce 
B = 80.664 
338 K A = −603.579 0.9857 qe = −603.579 + 102.539Ce 
B = 102.539 
Table 3

Adsorption capacity of different adsorbents for MB

Adsorbents Adsorption capacity (mg/g) Reference 
Activated lignin‒chitosan extruded blends 36.25 (293 K) Albadarin et al. (2017)  
Fe3O4@AMCA-MIL-53(Al) nanocomposite 318.36 (298 K) Alqadami et al. (2018)  
Carbon nanotubes 46.2 (298 K) Yao et al. (2010)  
Cellulose nanofibrils 122.2 (293 K) Chan et al. (2015)  
Nanoporous activated carbon prepared from karanj 154.8 (303 K) Islam et al. (2017)  
Sunflower stem pith 154 (298 K) Present work 
Adsorbents Adsorption capacity (mg/g) Reference 
Activated lignin‒chitosan extruded blends 36.25 (293 K) Albadarin et al. (2017)  
Fe3O4@AMCA-MIL-53(Al) nanocomposite 318.36 (298 K) Alqadami et al. (2018)  
Carbon nanotubes 46.2 (298 K) Yao et al. (2010)  
Cellulose nanofibrils 122.2 (293 K) Chan et al. (2015)  
Nanoporous activated carbon prepared from karanj 154.8 (303 K) Islam et al. (2017)  
Sunflower stem pith 154 (298 K) Present work 

The capacity of MB adsorption onto SSP was compared with that of the other adsorbents reported in the literature and is shown in Table 3. The adsorption capacity of SSP is not inferior to the other materials. These data clearly demonstrated that the SSP is an effective and feasible adsorbent for purifying MB-contaminated wastewater. Compared with other complex adsorbents, the SSP has several advantages such as low cost, easy availability of raw materials, and biodegradability. According to the above analysis, we have found that the SSP was the most potential efficient adsorbent for the detoxification of MB.

Adsorption thermodynamics

The thermodynamics parameters (ΔGo, ΔHo and ΔSo) were calculated by following equation (Naushad 2014): 
formula
(5)
 
formula
(6)
 
formula
(7)
where , R(8.314 J/mol·K) is the gas constant and T is the adsorption temperature. Equations (5) and (6) are derived for Equation (7). According to Equation (5), the enthalpy (ΔHo) and entropy (ΔSo) can be determined from the slopes and the intercepts of a graph ‘lnKa versus 1/T’ (data not provided) and the Gibb's free energy (ΔGo) was calculated by Equation (6). All the calculated thermodynamics parameters are illustrated in Table 4.
Table 4

Thermodynamic parameters for MB uptake by the SSP

Temperature (KThermodynamic parameters
 
ΔG0 (KJ/mol) ΔS0 (KJ/mol·K) ΔH0 (KJ/mol) R2 
298 7,654.46 6.39 9533.06 0.9900 
308 7,570.79 
318 7,431.79 
328 7,434.87 
338 7,411.01 
Temperature (KThermodynamic parameters
 
ΔG0 (KJ/mol) ΔS0 (KJ/mol·K) ΔH0 (KJ/mol) R2 
298 7,654.46 6.39 9533.06 0.9900 
308 7,570.79 
318 7,431.79 
328 7,434.87 
338 7,411.01 

When analyzing, the thermodynamics parameters can be extracted from the following information: (i) ΔG0 > 0, the adsorption of MB occurs non-spontaneously; (ii) ΔSo > 0, the randomness at the solid/solution interface increases during the adsorption of MB onto SSP; (iii) ΔHo > 0, the adsorption of MB is endothermic (Al-Othman et al. 2012; Naushad et al. 2016).

Regeneration studies

Desorption efficiency of various eluents for MB is illustrated in Figure 3. Among the eluents, the maximum MB desorption efficiency (63.26%) was obtained with 0.25 mol/L sulfuric acid. Further increase in sulfuric acid concentration leads to a decrease in desorption efficiency. The decreased desorption efficiency may be explained by deterioration of adsorption sites on the SSP surface at higher sulfuric acid concentration due to hydrolyzation of cellulose in the SSP (Malekbala et al. 2015).

Figure 3

Effect of different concentrations of various eluents on MB desorption efficiency.

Figure 3

Effect of different concentrations of various eluents on MB desorption efficiency.

Adsorption mechanism

Figure 4 illustrates the Fourier transform infrared (FTIR) spectra of bare SSP and SSP with MB adsorbed. The broad adsorption peak around 1,337 cm−1 is indicative of the existence of an amide bond (Figure 3(b)), and the S element is present in the SSP adsorbed with MB according to the EDX spectra analysis (Figure 5(d)). The above results give evidence that the MB was anchored on the surface of SSP. As shown in Figure 4(a), the characteristic peak at 2,924 cm−1 was assigned to stretching vibration of C-H. The peaks at 1,626 cm−1 and 1,043 cm−1 were attributed to C = O and C-O stretching vibration, respectively. However, the FTIR spectrum of SSP adsorbed with MB (Figure 4(b)) has changed. It was noted that the characteristic peak at 1,626 cm−1 shifted to 1,616 cm−1. The above results indicated that the C = O bonds played a quite important role in the detoxification of MB. These results corresponded with the experimental results that were reported in the literature (Madrakian et al. 2011; Cheng et al. 2017). MB is an anionic dye and the SSP carries a net negative charge. Hence, the SSP can adsorb the MB mainly due to the electrostatic attraction between them. On the other hand, the SSP is a porous material with high specific area. The BET surface area and pore volume of adsorbent-ultrasonic spray were 2.24 m²/g and 0.0047 cm³/g, respectively. The surface of the SSP had a pseudo-hexagonal cellular structure with a relatively smooth surface (Figure 5(a) and 5(a),1). The portion pores were filled with MB and the surface roughness increased after adsorption (Figure 5(b) and 5(b),1). The surface area and pore volume of SSP adsorbed with MB increased and the average pore diameter of the SSP changed from 18.15 nm to 7.19 nm after adsorbing MB (Table 5). This may be due to the pore canal of SSP filling with MB and the micro-pore content of SSP increasing. The nitrogen adsorption-desorption isotherms of SSP and SSP adsorbed with MB are shown in Figure 6. The data exhibit a typical type-I adsorption-desorption isotherm curve (Langmuir isotherm) with a hysteresis loop according to IUPAC classifications. The Van der Waals forces between the phenolic ring of SSP and aromatic heterocyclic ring of MB may also have contributed to the detoxification of MB (Manna et al. 2017).

Table 5

Surface properties of the SSP before and after adsorption for MB

Materials Surface area (SBET)/(m2/g) Pore size (BJH)/nm Pore volume/(cm3/g) 
SSP 2.24 18.15 0.0047 
SSP adsorbed with MB 3.94 7.19 0.0081 
Materials Surface area (SBET)/(m2/g) Pore size (BJH)/nm Pore volume/(cm3/g) 
SSP 2.24 18.15 0.0047 
SSP adsorbed with MB 3.94 7.19 0.0081 
Figure 4

ATR-FTIR spectra of (a) SSP, (b) SSP with MB adsorbed.

Figure 4

ATR-FTIR spectra of (a) SSP, (b) SSP with MB adsorbed.

Figure 5

SEM images of (a) SSP (500×), (a1) SSP (1,000×), (c) SSP adsorbed with MB (500×), (c1) SSP adsorbed with MB (2,000×) N and EDX spectra of SSP (b), SSP adsorbed with MB (d).

Figure 5

SEM images of (a) SSP (500×), (a1) SSP (1,000×), (c) SSP adsorbed with MB (500×), (c1) SSP adsorbed with MB (2,000×) N and EDX spectra of SSP (b), SSP adsorbed with MB (d).

Figure 6

Nitrogen adsorption/desorption isotherms for SSP and SSP adsorbed with MB.

Figure 6

Nitrogen adsorption/desorption isotherms for SSP and SSP adsorbed with MB.

CONCLUSIONS

The SSP, which was used without any chemical treatment, is an outstanding adsorbent for detoxification of MB. The adsorption of MB using SSP as an adsorbent strongly depends on the experimental parameters and the maximum adsorption capacity is 277 mg/g at 338 K. The MB adsorption equilibrium data better fitted the Langmuir isotherm model in the examined temperature range. The pseudo second order kinetic model can be used to describe the adsorption process of MB onto SSP. Thermodynamic analyses indicated that the adsorption of MB was endothermic and non-spontaneous. These results indicate that SSP is a potential adsorbent for uptake of MB from sewage. Future research will be focused on the modification of the SSP to improve the adsorption capacity for MB.

ACKNOWLEDGEMENTS

This work is supported by the Foundation of Key Laboratory of Pulp and Paper Science and Technology of Ministry of Education/Shandong Province of China (No. KF201826), the National Natural Science Foundation of China (No. 21507009), NEPU Scientific Research Foundation (No. rc201726), Natural Science and Foundation of Heilongjiang Province (No. B2016002).

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