Polyethylenimine functionalized corn bract, an agricultural waste

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Polyethylenimine functionalized corn bract, an agricultural waste material, for efficient removal and recovery of Cr(VI) from aqueous solution Tiantian Luo, Xike Tian, Chao Yang, Wenjun Luo, Yulun Nie, and yanxin wang J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.7b02699 • Publication Date (Web): 28 Jul 2017 Downloaded from http://pubs.acs.org on July 30, 2017

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Journal of Agricultural and Food Chemistry

Polyethylenimine Functionalized Corn Bract, an Agricultural Waste Material, for Efficient Removal and Recovery of Cr(VI) from Aqueous solution

Tiantian Luo†, Xike Tian*, †, Chao Yang†, Wenjun Luo†, Yulun Nie†, Yanxin Wang††

†

Faculty of Materials Science and Chemistry, China University of Geosciences,

Wuhan 430074, PR. China. ††

School of Environmental Studies, China University of Geosciences, Wuhan 430074,

PR. China.

1

ACS Paragon Plus Environment


1

ABSTRACT

2

In this study, polyethylenimine functionalized corn bract (PEI-CB) was firstly used to

3

remove aqueous Cr(VI) via “waste control by waste” concept. The results indicated

4

that PEI-CB had an excellent performance for Cr(VI) removal and the maximum

5

removal capacity was 438 mg/g. The adsorption of Cr(VI) was fitted to Langmuir

6

model and kinetics of uptake could be described by a pseudo-second-order rate model

7

well. Amine was proven to be the active center for Cr(VI) adsorption and partially

8

reduction to Cr(III), while removal efficiency was enhanced at lower pH value and

9

higher temperature. Besides, nanosized Cr2O3 with a high purity was obtained by

10

simple calcination of Cr(VI) laden adsorbent. Hence, this study provided a novel

11

strategy for Cr(VI) wastewater remediation and pure Cr2O3 recovery. The prepared

12

PEI-CB was then a promising alternative of low cost for replacement of the current

13

expensive absorbent of removing Cr(VI) from wastewater from the view of

14

sustainability.

15 16

KEYWORDS: corn bract, modification, polyethylenimine, Cr(VI) removal, recovery

17 18 19

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1. INTRODUCTION

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Hexavalent chromium, Cr(VI), is hazardous at high levels due to its high

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biotoxicity and carcinogenicity.1 The maximum contaminant limits of total chromium

23

in drinking water was set at 100 µg/L and 50 µg/L by the United States Environmental

24

Protection Agency and the World Health Organization respectively.2, 3 Since improper

25

treatment will damage environment and people’s health seriously, low cost and highly

26

effective strategies for treating Cr (VI) containing wastes are in great demand all over

27

the world.4,

28

adsorption, chemical reduction precipitation, membrane separation and ion-exchange

29

et al.6-11 However, the reduction precipitation can consume chemical reagents and

30

produce toxic sludge resulting in the secondary pollution. The membrane separation

31

and ion-exchange process are costly and complex.12 Therefore, it is a strong need to

32

develop a cheap and environmentally friendly solid-adsorbent with high efficiency for

33

Cr(VI) removal.

5

At present, conventional methods for the Cr(VI) removal include

34

Besides, corn bract, as a typical agricultural waste13, open burning is a usual

35

disposal method and occurs more frequently in grain-producing regions with

36

increasing crop yields in China.14 However, the burning has been considered as an

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important source of carbonaceous species. It has been estimated that elemental carbon

38

(EC) emission from agricultural field burning was 26 times in 2009 than in 1980 in

39

China.15,

40

environmental pollution. Hence, it is also necessary to find a new way for corn bract

41

disposal environmentally friendly. Corn bract has a 2D framework and composed of

16

The emissions get more serious in recent years and cause regional

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lignocellulosic materials (54-58 %) that contain many functional groups,17 which is

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suitable to use as adsorbents. The use of corn bract as adsorbent can not only save

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money due to the reduced need for traditional agricultural waste disposal, but also

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promote recycling and reuse. But, the original corn bract has little or no capacity for

46

the removal of heavy metal cations because there is little or no adsorption sites on the

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surfaces. Therefore, it is necessary to develop effective methods to modify the surface

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of corn bract.

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species because the amine groups are easily protonated and thus could remove anionic

50

metal species via electrostatic interaction or hydrogen binding. Polyethyleneimine

51

modified halloysite showed good adsorption ability for Cr(VI) due to the presence of

52

a large number of primary and secondary amine groups per molecule.

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surface area, natural shape, abundant surface active site and tunable surface chemistry

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of corn bract enabled it to be modified by organic polymer and utilized as a promising

55

adsorbent. However, few studies have been conducted to use the modified corn bract

56

for the Cr(VI) adsorption.

18, 19

Amine functionalized clay is effective in removing anionic metal

4, 20

The high

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Moreover, Cr is an expensive element, in which Cr2O3 was widely used in lithium

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storage and corrosion protection.12 To recover Cr2O3 from the Cr-laden adsorbent has

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great economic incentives and good potential for technology development. Chemical,

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electrochemical and biological methods have been used to convert Cr(VI) to less toxic

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Cr(III) and even recover Cr element, which are generally energy and chemical

62

intensive.

63

was proposed in this study. Polyethyleneimine grafting was used to increase the

3, 21, 22 23

Hence, a novel strategy on the Cr(VI) removal and Cr2O3 recovery

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adsorption capacity of corn bract and calcination of Cr-laden modified corn bract

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adsorbent was used to recover Cr2O3 via the carbonization process. The results

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indicated that Cr(VI) was efficiently removed with a maximum capacity of 438 mg/g

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at 323 K and nanosized Cr2O3 with high purity was also obtained. The proposed

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strategy accords with the “waste control by waste” concept. The modified corn bract

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as an inexpensive and efficient solid-adsorbent provides a promising alternative for

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Cr(VI) wastewater remediation from the view of sustainability.

71 72

2. MATERIALS AND METHODS

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Chemicals and Materials. Original corn bract (CB) was collected from Henan

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province, central China and naturally air-dried before use. Epichlorohydrin (ECH),

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and sodium hydroxide (NaOH) was obtained from Sinopharm Chemical. Aluminium

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chloride (AlCl3) was purchased from KaiTong Chemical Reagent Ltd. (Tianjin,

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China). Arginine (Arg) and urea was purchased from Aladdin Chemical Company.

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Polyethylenimine (PEI, molecular weight 70,000) was purchased from Shanghai

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Macklin Biochemical Co., Ltd. Other chemicals were of analytical grade and used

80

without further purification.

81

Polyethylenimine Functionalization of Corn Bract. As shown in Fig. 1, corn bract

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was firstly treated by a 7 wt % NaOH and 12 wt % urea solution for 30 min at -12 °C

83

to

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macromolecules.24 Then, 5.0 g CB was put into 200 mL 5 wt% arginine solutions and

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react for 12 h at 313K in the presence of 0.25 g AlCl3. After washed with deionized

expose

hydroxyl

groups

by

reducing

the

crystallinity

5


of

cellulose


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water for several times and dried for 6 h at 50 °C, the obtained material was

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transferred into a mixture of 10 mL ECH and 20 mL 2.5 mol/L of NaOH under

88

stirring at 40 °C for 12 h. After washed with methyl alcohol for several times and kept

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in a hot air oven at 50 °C for 6 h, the obtained CB was put into 10 mL PEI (30 w/v%)

90

solution for 24 h at 100 °C, followed by drying in air at 50 °C for 6 h. PEI-CB was

91

then obtained and used for further experiments.

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Characterization. Scanning electron microscope (SEM) image was used to

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examine the morphology by a Hitachi SU8010 field emission scanning electron

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Microscope (FESEM, 15kV, Hitachi, Japan) and a transmission electron microscope

95

(TEM, CM 12, Philips, Netherlands). Fourier transform infrared (FT-IR) spectra were

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obtained on instrument (Thermo Nicolet AVATAR360, The United States) using the

97

standard

98

(MULTILAB2000, Thermo Electron Corporation, The United States) was used in the

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surface analysis of samples. Powder X-ray diffraction (XRD) patterns of materials

100

were obtained with a diffractometer (Rigaku D/max-βB) using Cu Kα radiation source

101

(λ=0.15432 nm). (Bruker AXS D8-Focus X, Germany) The Cr(VI) concentration was

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detected with the 1,5-diphenylcarbazide method, using an ultraviolet-visible

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(TU-1800PC, China) spectrophotometer at λ=540 nm.

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Batch Experiments. Adsorption experiments were carried out in a 150 mL conical

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flask containing about 20 mg PEI-CB and 100 mL Cr(VI) solution prepared with

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K2Cr2O7, which was shaken at 200 rpm in a thermostatic shaker. For the adsorption

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kinetic tests, about 20 mg of adsorbent was added into 100 ml of 100 mg/L Cr(VI)

KBr

disk

method.

X-ray

photoelectron

6


spectrometer

(XPS)

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under stirring at pH of 2.0, and stirring continued for a specified time (0-24 h). The

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pseudo-first-order and pseudo-second-order kinetic models were applied to fit

110

experimental data obtained from batch experiments. The isothermal adsorption

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experiments were conducted by varying the concentration of Cr(VI) from 20 to 200

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mg/L (pH = 2). The flasks were kept in an isothermal shaker for 24 h to reach

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equilibrium of the solution with the solid mixture. Langmuir and Freundlich isotherm

114

models were used to fit the equilibrium data of adsorption of Cr (VI) on the PEI-CB.

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The influence of solution pH (2, 3, 4, 5, 6 and 7) and temperature (293 K, 303 K, 313

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K and 323 K) on Cr(VI) adsorption was also investigated. Finally, the Cr laden

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absorbent was calcined at 500 °C for 2 h in a muffle furnace and the residue was

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collected and pure Cr2O3 was then recovered.

119 120

3. RESULTS AND DISCUSSION

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Characterization of PEI-CB. Fig. 2 depicted the FT-IR spectra of CB before and

122

after PEI modification. For CB in Fig. 2a, the broad band at 3424 cm-1 can be

123

assigned to O-H stretching vibration and the band at 2900 cm-1 was attributed to C-H

124

stretching of the methyl group.

125

corresponded to C=O and benzene stretching vibration of lignin due to the

126

decrystallization process by NaOH and urea respectively.

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1637 cm-1 and 1042 cm-1 are the characteristic peak of C=C bond and skeletal

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vibrations involving C-O stretching, respectively.28 After modification of CB by PEI

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(Fig. 2b), the spectrum of PEI-CB exhibits obvious changes. The new peaks at 2924

25, 26

The peaks at 1732 cm-1 and 1520 cm-1

7


27

Besides, the bands at


130

cm-1 and 2873 cm-1 are ascribed to the C-H stretching from the -CH2 group of PEI.26,

131

29

132

cm-1 further indicated the disappearance of -OH group and successful grafting PEI on

133

the surface of CB. As shown in Fig. 3, the surface morphology of corn bract also

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changed a lot after PEI modification. Compared with original CB in (Fig. 3a), the

135

surface of PEI-CB (Fig. 3b) became smoother and denser with a plastic like coat,

136

which indicated that PEI was successfully anchored on the surface of CB.

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Furthermore, compared with CB in Fig. 4a, the existence of N element (8.86 at % in

138

Fig. 4b) on the surface of PEI-CB by EDX analysis also proved the successful PEI

139

immobilization on CB.

140

Excellent Performance of PEI-CB for Cr(VI) Removal. Fig. 5A showed the effect

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of contact time on Cr(VI) adsorption over PEI-CB using initial concentration of 100

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mg/L at pH 2.0. The adsorption capacity of PEI-CB to Cr(VI) increased rapidly within

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6.6 h. Thereafter, it continued to increase at a slower rate and finally approached

144

adsorption equilibrium after 24 h. The pseudo-first-order and pseudo-second-order

145

kinetic models were fitted to the adsorption kinetic data. The parameters of kinetic

146

models were illustrated in Table 1. Compared with that of pseudo-first-order, the

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calculated value qe (cal) of the pseudo-second-order kinetic model was more close to

148

the experimental one qe (exp), and the plots show quite good linearity with R2 values

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of 0.986. Therefore, the adsorption kinetics followed pseudo-second-order model well,

150

suggesting a chemisorption process. It also means that the adsorption rate is

151

proportional to the square of the number of free sites, which corresponds to the term

While the decreased peak intensity at 3424 cm-1, 1732 cm-1, 1637 cm-1 and 1042

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(qe-qt)2 in the pseudo-second-order model.30 Moreover, Langmuir and Freundlich

153

models were applied to fit to experimental data, respectively. It can be clearly seen

154

from Fig. 5B and Table 2 that higher correlation coefficients are obtained with the

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Langmuir model. The model assumes a monolayer adsorption onto a homogeneous

156

surface where binding sites have equal affinity and energy.31 The results revealed that

157

the adsorption capacity was 438 mg/g at an ambient temperature of 323 K, which

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showed much higher capacity towards Cr(VI) than that of TiO2 (33.9 mg/g),32

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EDA-modified magnetic chitosan resin (51.8 mg/g),33 amino-functionalized MSC

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composite (171.5 mg/g), 34 PEI immobilized acrylate-based beads (140.6 mg/g) 35 and

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its capacity was also comparable to. aerobic granules functionalized with

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polyethylenimine (401.5 mg/g).36

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Fig. 6 showed the effect of initial solution pH (2-7) on the adsorption capacity of

164

PEI-CB for Cr(VI). Obviously, the Cr(VI) adsorption was significantly pH dependent.

165

The adsorption capacity decreased with the rising solution pH and lower pH favored

166

the Cr(VI) adsorption. The amino group of PEI will be protonated to form the

167

positively charged sites (such as -NH3+) and result in the electrostatic attraction with

168

the negatively charged Cr(VI).37, 38 Hence, pH 2.0 was selected as the optimum pH

169

value for the following adsorption experiments. The effect of temperature on Cr(VI)

170

adsorption was also investigated and the results were present in Fig. 7. The Cr (VI)

171

adsorption uptake was found to increase with increasing solution temperature from

172

293 to 323 K, which indicates the endothermic nature of the adsorption process. The

173

Gibbs free energy is the fundamental indicator for criterion of spontaneity and the

9



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adsorption can occur spontaneously at a given temperature if ∆G is negative.39 Hence,

175

as depicted in Table 3, higher temperature results in a much lower ∆G and an great

176

increase of entropy change, which were then beneficial to the increase rate of

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diffusion of Cr(VI) as the adsorbate across the external boundary layer and its

178

removal efficiency over PEI-CB. 40, 41

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Adsorption Mechanism. As depicted in Fig. 4c and 4d, Cr element appeared on

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PEI-CB after adsorption with a content of 19.94 at%. The energy dispersive X-ray

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mapping analysis further showed that Cr element was highly dispersed on the surface

182

of PEI-CB. Since the adsorption process followed the Langmuir model (monolayer

183

adsorption), Cr(VI) was anchored on the surface of PEI-CB via electrostatic attraction

184

and hydrogen binding (Fig. 8a) As reported, surface complex was formed between the

185

ligand in absorbent and the metal ions, hence, the immobilization of PEI can provide

186

more adsorption sites for Cr (VI) adsorption.42 Although it was difficult to clarify

187

their separate contribution to Cr (VI) removal, the hydrogen bonding interactions was

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between hydrogen atoms in amino groups and oxygen atoms in HCrO4-.43 The

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adsorption process was usually determined by the functional groups on the

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adsorbent’s surface. Hence, XPS technique was used to study the surface chemical

191

composition of PEI-CB before and after Cr(VI) adsorption. As shown in Fig. 9B, the

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two strong peaks at 397.9 eV and 398.6 eV were attributed to =N- and -NH2 groups of

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PEI in PEI-CB. After adsorption of Cr(VI), the peak intensity of =N- decreased

194

greatly and a new peak of protonated amine group (-NH3+) centered at 400.1 eV

195

appeared. It indicated that Cr(VI) was bonded onto the protonated amine groups of

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PEI. The high resolution XPS spectra of the Cr2p region can be curve-fitted with four

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components (Fig. 9A), in which the peaks at 578.4 eV and 587.4 eV can be assigned

198

to Cr(VI) while the binding energies at 575.6 eV and 585.6 eV are the characteristic

199

peaks of Cr(III)44. The existence of Cr(III) suggested that the adsorbed Cr(VI) was

200

partially reduced to less toxic Cr(III) due to the electrons transfer from the amine

201

group of PEI.20 As shown in Fig. 8b, the process of adsorption and reduction can be

202

explained as follows: First, the amine groups on the PEI-CB are protonated to adsorb

203

the Cr(VI). Then the reduction reactions may proceed. The electrons which required

204

for reduction of Cr(VI) came from electron-donor groups of the biomass.45 Finally

205

with the help of electrons, the Cr(VI) can be reduce to Cr(III). Similar results have

206

also been reported. The thermodynamic behavior of Cr(VI) adsorption onto PEI-CB

207

was also evaluated. As shown in Fig. 7B, plotting ln (qe/ce) against 100/T gave a

208

straight line. The slope and intercept equal to -∆H/R and ∆S/R. As shown in Table 3,

209

the four negative ∆G values showed that the adsorption process was spontaneous and

210

higher temperature favored the adsorption. At a higher temperature, the interaction

211

between the solvent and solid surface led to a greater number of adsorption sites,

212

enhancing the possibility of Cr(VI) adsorption onto PEI-CB. 40

213

Successful Cr2O3 Recovery. Cr laden absorbent was calcined at 500 °C for 2 h in a

214

muffle furnace and the residue was collected and characterized by XPS. The peaks at

215

binding energies of 576.4 eV and 586.4 eV were assigned to Cr(III). No signal for the

216

characteristic peaks of Cr(VI) was found, indicating the total reduction of Cr(VI) to

217

Cr(III). As shown in Fig. 10A, the obtained product exhibited a characteristic XRD

11



218

pattern of pure Cr2O3. It was reported that a reduction process occurred in

219

carbonization of metal contained carbon precursor. For example, formaldehyde can

220

serve as a reducing agent for AgNO3. Hence, the adsorbed Cr(VI) was converted into

221

Cr(III) and Cr2O3 was then recovered during the carbonization of Cr laden PEI-CB.

222

TEM image further suggested that the nanosized Cr2O3 was obtained with a diameter

223

below 100 nm.

224 225

AUTHOR INFORMATION

226

Corresponding Author

227

Tel/Fax: +86-27-67884574. E-mail: [email protected]

228

Funding

229

We are grateful to the Foundation for Innovative Research Groups of the National

230

Natural Science Foundation of China (No. 41521001) for the financial support. The

231

project was also supported by the National Natural Science Foundation of China (No.

232

51371162), and the “Fundamental Research Funds for the Central Universities”.

233

Notes

234

The authors declare no competing financial interest.

235 236

ACKNOWLEDGMENTS

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We are deeply indebted to a number of people without whose encouragement and

238

assistance this thesis would not have been completed.

239 240

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REFERENCES

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1. NAMIEŚNIK, J.; RABAJCZYK, A., Speciation Analysis of Chromium in Environmental Samples. Critical Reviews in Environ. Sci. Technol. 2012, 42, (4), 327-377. 2. Jiang, W.; Cai, Q.; Xu, W.; Yang, M.; Cai, Y.; Dionysiou, D. D.; O'Shea, K. E., Cr(VI) adsorption and reduction by humic acid coated on magnetite. Environ. Sci. Technol. 2014, 48, (14), 8078-85. 3. Bick, A. N., California's Office of Environmental Health Hazard Assessment (OEHHA) Proposes New, More Stringent, Drinking Water Standard for Hexavalent Chromium. 4. Chen, J. H.; Xing, H. T.; Guo, H. X.; Weng, W.; Hu, S. R.; Li, S. X.; Huang, Y. H.; Sun, X.; Su, Z. B., Investigation on the adsorption properties of Cr(VI) ions on a novel graphene oxide (GO) based composite adsorbent. J.Mater.Chem.A 2014, 2, (31), 12561-12570. 5. Zhu, K.; Gao, Y.; Tan, X.; Chen, C., Polyaniline Modified Mg/Al Layered Double Hydroxide Composites and Their Application in Efficient Removal of Cr(VI). Acs Sustain. Chem. Eng. 2016, 4, (8). 6. Anhuai Lu, †; Shaojun Zhong; Chen, J.; Shi, J.; Junli Tang, A.; Lu§, X., Removal of Cr(VI) and Cr(III) from Aqueous Solutions and Industrial Wastewaters by Natural Clino-pyrrhotite. Environ. Sci. Technol. 2006, 40, (9), 3064-9. 7. Kocurek, P.; Kolomazník, K.; Bařinová, M., Chromium removal from wastewater by reverse osmosis. Wse. Trans. Environ.Develop. 2014, 10, (1), 358-365. 8. D’Angelo, A.; Galia, A.; Scialdone, O., Cathodic abatement of Cr(VI) in water by microbial reverse-electrodialysis cells. J. Electroanal. Chem. 2015, 748, 40-46. 9. Dharnaik, A. S.; Ghosh, P. K., Hexavalent chromium [Cr(VI)] removal by the electrochemical ion-exchange process. Environ. Technol. 2014, 35, (18), 2272-2279. 10. Sun, M.; Zhang, G.; Qin, Y.; Cao, M.; Liu, Y.; Li, J.; Qu, J.; Liu, H., Redox Conversion of Chromium(VI) and Arsenic(III) with the Intermediates of Chromium(V) and Arsenic(IV) via AuPd/CNTs Electrocatalysis in Acid Aqueous Solution. Environ. Sci. Technol. 2015, 49, (15), 9289-97. 11. Goyal, R. K.; Jayakumar, N. S.; Hashim, M. A., A comparative study of experimental optimization and response surface optimization of Cr removal by emulsion ionic liquid membrane. J. Hazard. Mater. 2011, 195, (1), 383-90. 12. Sun, B.; Reddy, E. P.; Smirniotis, P. G., Visible light Cr(VI) reduction and organic chemical oxidation by TiO2 photocatalysis. Environ. Sci. Technol. 2005, 39, (16), 6251-9. 13. Xu, C.; Ma, F.; Zhang, X.; Chen, S., Biological pretreatment of corn stover by Irpex lacteus for enzymatic hydrolysis. J. Agric. Food Chem. 2010, 58, (20), 10893-8. 14. Hahnen, S.; Joeris, T.; Kreuzaler, F.; Peterhänsel, C., Quantification of photosynthetic gene expression in maize C(3) and C(4) tissues by real-time PCR. Photosynth. Res. 2003, 75, (2), 183-192.

13



282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325

15. Wang, X.; Chen, Y.; Tian, C.; Huang, G.; Yin, F.; Fan, Z.; Zheng, Z.; Li, J.; Gan, Z., Impact of agricultural waste burning in the Shandong Peninsula on carbonaceous aerosols in the Bohai Rim, China. Sci. Total Environ. 2014, 481, (1), 311–316. 16. Cheng, M. T.; Horng, C. L.; Su, Y. R.; Lin, L. K.; Lin, Y. C.; Chou, C. K., Particulate matter characteristics during agricultural waste burning in Taichung City, Taiwan. J. Hazard. Mater. 2009, 165, (1-3), 187. 17. Yang, M. X.; Zhou, R., Research on Degumming Experiment of Corn Bracts. Adv Mater Res 2012, 550-553, 1242-1247. 18. Zhou, Y.; Jin, Q.; Zhu, T.; Ma, T.; Hu, X., Removal of Chromium (VI) from Aqueous Solution by Cellulose Modified with D-Glucose. Sep. Sci. Technol. 2012, volume 47, (1), 157-165. 19. Gurgel, L. V.; Jc, P. D. M.; de Lena, J. C.; Gil, L. F., Adsorption of chromium (VI) ion from aqueous solution by succinylated mercerized cellulose functionalized with quaternary ammonium groups. Bioresour. Technol. 2009, 100, (13), 3214-20. 20. Tian, X.; Wang, W.; Tian, N.; Zhou, C.; Yang, C.; Komarneni, S., Cr(VI) reduction and immobilization by novel carbonaceous modified magnetic Fe3O4/halloysite nanohybrid. J. Hazard. Mater. 2016, 309, 151-156. 21. Zhang, H. K.; Lu, H.; Wang, J.; Zhou, J. T.; Sui, M., Cr(VI) Reduction and Cr(III) Immobilisation by Acinetobacter sp. HK-1 with the Assistance of a Novel Quinone/Graphene Oxide Composite. Environ. Sci. Technol. 2014, 48, (21), 12876-85. 22. Yang, Y.; Wang, G.; Deng, Q.; Ng, D. H.; Zhao, H., Microwave-assisted fabrication of nanoparticulate TiO(2) microspheres for synergistic photocatalytic removal of Cr(VI) and methyl orange. Acs App. Mater. Inter. 2014, 6, (4), 3008. 23. Cheng, Y.; Yan, F.; Huang, F.; Chu, W.; Pan, D.; Chen, Z.; Zheng, J.; Yu, M.; Lin, Z.; Wu, Z., Bioremediation of Cr(VI) and Immobilization as Cr(III) by Ochrobactrum anthropi. Environ. Sci. Technol. 2010, 44, (16), 6357-63. 24. Das, R.; Ghorai, S.; Pal, S., Flocculation characteristics of polyacrylamide grafted hydroxypropyl methyl cellulose: An efficient biodegradable flocculant. Chem. Eng. J. 2013, 229, (4), 144-152. 25. Tang, F.; Huang, X.; Zhang, Y.; Guo, J., Effect of dispersants on surface chemical properties of nano-zirconia suspensions. Ceram. Int. 2000, 26, (1), 93-97. 26. Anirudhan, T.; Rauf, T. A., Adsorption performance of amine functionalized cellulose grafted epichlorohydrin for the removal of nitrate from aqueous solutions. J. Ind. Eng. Chem. 2013, 19, (5), 1659-1667. 27. Ralph, J.; Akiyama, T.; Coleman, H. D.; Mansfield, S. D., Effects on Lignin Structure of Coumarate 3-Hydroxylase Downregulation in Poplar. J. Biological. Chem. 2012, 5, (13), 8843-53. 28. Jermakowicz-Bartkowiak, D., Preparation, characterisation and sorptive properties towards noble metals of the resins from poly(vinylbenzyl chloride) copolymers. Rea. Funct. Poly. 2005, 62, (1), 115-128. 29. Patil, S. K. R.; Heltzel, J.; Lund, C. R. F., Comparison of Structural Features of Humins Formed Catalytically from Glucose, Fructose, and 5-Hydroxymethylfurfuraldehyde. Energy & Fuels 2012, 26, (8), 5281-5293. 14


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30. Yu, F.; Wu, Y.; Li, X.; Ma, J., Kinetic and thermodynamic studies of toluene, ethylbenzene, and m-xylene adsorption from aqueous solutions onto KOH-activated multiwalled carbon nanotubes. J. Agri. Food Chem. 2012, 60, (50), 12245-53. 31. Redlich, O.; Peterson, D. L., A Useful Adsorption Isotherm. J. Phys. Chem. 2007, 63, (6), 1024-1024. 32. Environmental Science and TechnologyAsuha, S.; Zhou, X. G.; Zhao, S., Adsorption of methyl orange and Cr(VI) on mesoporous TiO2 prepared by hydrothermal method. J. Hazard. Mater. 2010, 181, (1-3), 204-210. 33. Hu, X. J.; Wang, J. S.; Liu, Y. G.; Li, X.; Zeng, G. M.; Bao, Z. L.; Zeng, X. X.; Chen, A. W.; Long, F., Adsorption of chromium (VI) by ethylenediamine-modified cross-linked magnetic chitosan resin: Isotherms, kinetics and thermodynamics. J. Hazard. Mater. 2011, 185, (1), 306-14. 34. Sun, X.; Yang, L.; Li, Q.; Zhao, J.; Li, X.; Wang, X.; Liu, H., Amino-functionalized magnetic cellulose nanocomposite as adsorbent for removal of Cr(VI): Synthesis and adsorption studies. Chem. Eng. J. 2014, 241, (4), 175-183. 35. Bayramoğlu, G.; Arica, M. Y., Adsorption of Cr(VI) onto PEI immobilized acrylate-based magnetic beads: Isotherms, kinetics and thermodynamics study. Chem. Eng. J. 2008, 139, (1), 20-28. 36. Sun, X. F.; Ma, Y.; Liu, X. W.; Wang, S. G.; Gao, B. Y.; Li, X. M., Sorption and detoxification of chromium(VI) by aerobic granules functionalized with polyethylenimine. Water Res. 2010, 44, (8), 2517-2524. 37. Li, Y.; Gao, B.; Tao, W.; Sun, D.; Xia, L.; Wang, B.; Lu, F., Hexavalent chromium removal from aqueous solution by adsorption on aluminum magnesium mixed hydroxide. Water Res. 2009, 43, (12), 3067-3075. 38. Zhao, G.; Li, J.; Ren, X.; Chen, C.; Wang, X., Few-layered graphene oxide nanosheets as superior sorbents for heavy metal ion pollution management. Environ. Sci. Technol. 2011, 45, (24), 10454-62. 39. Shi, W.; Zhai, Y. Y.; Qiang, G.; Luo, W. J.; Hua, X.; Zhou, C. G., Highly Efficient Removal of Acid Red 18 from Aqueous Solution by Magnetically Retrievable Chitosan/Carbon Nanotube: Batch Study, Isotherms, Kinetics, and Thermodynamics. J. Chem. Eng. Data 2013, 59, (1), 39–51. 40. Gao, Q.; Zhu, H.; Luo, W. J.; Wang, S.; Zhou, C. G., Preparation, characterization, and adsorption evaluation of chitosan-functionalized mesoporous composites. Micropor. Mesopor. Mat. 2014, 193, (3), 15-26. 41. Lequin, S.; Chassagne, D.; Karbowiak, T.; Gougeon, R.; Brachais, L.; Bellat, J. P., Adsorption equilibria of water vapor on cork. J. Agric. Food Chem. 2010, 58, (6), 3438-45. 42. Shukla, A.; Zhang, Y. H.; Dubey, P.; Margrave, J. L.; Shukla, S. S., The role of sawdust in the removal of unwanted materials from water. J. Hazard. Mater. 2002, 95, (1-2), 137. 43. Fu, X.; Yang, H.; Lu, G.; Tu, Y.; Wu, J., Improved performance of surface functionalized TiO2 /activated carbon for adsorption–photocatalytic reduction of Cr(VI) in aqueous solution. Mater. Sci. Semicond. Process. 2015, 39, 362-370.

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44. Ai, Z.; Cheng, Y.; Zhang, L.; Qiu, J., Efficient removal of Cr(VI) from aqueous solution with Fe@Fe2O3 core-shell nanowires. Environ. Sci. Technol. 2008, 42, (18), 6955-60. 45. Park, D.; Yun, Y. S.; Park, J. M., Studies on hexavalent chromium biosorption by chemically-treated biomass of Ecklonia sp. Chemosphere 2005, 60, (10), 1356-64.

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Figures captions 376

Fig. 1. Synthetic route of PEI-CB.

377

Fig. 2. FT-IR spectra of original CB (a) and PEI-CB (b).

378

Fig. 3. SEM images of original CB (a) and PEI-CB (b).

379

Fig. 4 EDS analysis of CB (a), PEI-CB (b), Cr-loaded PEI-CB (c) and Mapping of Cr

380

element (d).

381

Fig. 5. Effects of contact time on Cr(VI) adsorption of PEI-CB (a) and adsorption

382

isotherms study model: Langmuir and Freundlich (b).

383

Fig. 6. Effect of initial pH on Cr(VI) adsorption by PEI-CB.

384

Fig. 7. Effect of temperature on Cr(VI) adsorption by PEI-CB (a) and linear plot of

385

ln(qe/Ce) vs. 100/T for the adsorption of Cr(VI) on PEI-CB (b).

386

Fig. 8. Possible linkages of Cr(VI) on PEI-CB (a) and possible reduction process of

387

Cr(VI) to Cr(III) on PEI-CB (b)

388

Fig. 9. XPS photoelectron spectroscopy of Cr2p after adsorption (A), N1s before and

389

after Cr(VI) adsorption (B) and Cr2p after calcination at 500 °C (c)

390

Fig. 10. XRD patterns (a), TEM image (b) and photograph (c) of the calcined product

391

at 500 °C.

392 393

Table captions

394

Table 1. Kinetic parameters for adsorption of Cr(VI) onto PEI−CB.

395

Table 2. Adsorption isotherm constants for Cr(VI) adsorption onto PEI−CB.

396

Table 3. Thermodynamic parameters at four different temperatures (Cr(VI) ion

397

concentration 100 mg/L, pH 2.0, contact time 24 h) 17



398

Fig. 1. Synthetic route of PEI-CB.

Fig. 2. FT-IR spectra of original CB (a) and PEI-CB (b).

Fig. 3. SEM images of original CB (a) and PEI-CB (b). 18


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Fig. 4 EDS analysis of CB (a), PEI-CB (b), Cr-loaded PEI-CB (c) and Mapping of Cr element (d).

Fig. 5. Effects of contact time on Cr(VI) adsorption of PEI-CB (a) and adsorption isotherms study model: Langmuir and Freundlich (b).

Fig. 6. Effect of initial pH on Cr(VI) adsorption by PEI-CB. 19



Fig. 7. Effect of temperature on Cr(VI) adsorption by PEI-CB (a) and linear plot of ln(qe/Ce) vs. 100/T for the adsorption of Cr(VI) on PEI-CB (b).

Fig. 8. Possible linkages of Cr(VI) on PEI-CB (a) and possible reduction process of Cr(VI) to Cr(III) on PEI-CB (b).

Fig. 9. XPS photoelectron spectroscopy of Cr2p after adsorption (A), N1s before and after Cr(VI) adsorption (B) and Cr2p after calcination at 500 °C (c) 20


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Fig. 10. XRD patterns (a), TEM image (b) and photograph (c) of the calcined product at 500 °C.

Table 1. Kinetic parameters for adsorption of Cr(VI) onto PEI−CB.

Adsorbate qexp(mg/g) Cr(Ⅵ)

438.1406

Pseudo-first-order qeal(mg/g) k1 R2 399.01 0.01941 0.903

Pseudo-second-order qeal(mg/g) k2 R2 432.41 0.00061 0.986

Table 2. Adsorption Isotherm Constants for Cr(VI) Adsorption onto PEI−CB.

Langmuir isotherm constants

Freundlich isotherm constants

T (K)

qm (mg/g)

KL (L/g)

R2

KF (mg1-1/n·L1/n·g-1)

1/n

R2

323

517.01674

0.0646

0.985

101.89

0.31304

0.934

Table 3. Thermodynamic parameters at four different temperatures (Cr(VI) ion concentration 100 mg/L, pH 2.0, contact time 24 h)

Absorbent PEI−CB

∆S (J mol-1 K-1) 55.45

∆H (kJ mol-1)

T/K

∆G(kJ mol-1)

12.35

293 303 313 323

-3.897 -4.451 -5.006 -5.560

21



TABLE OF CONTENTS GRAPHICS

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Polyethylenimine functionalized corn bract, an agricultural waste

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