Adsorption capability of virgin and calcined wheat bran for molybdenum present in aqueous solution and elucidating the adsorption mechanism by adsorption isotherms, kinetics, and regeneration

Accepted Manuscript Title: Adsorption capability of virgin and calcined wheat bran for molybdenum present in aqueous solution and elucidating the adsorption mechanism by adsorption isotherms, kinetics, and regeneration Authors: Fumihiko Ogata, Takehiro Nakamura, Naohito Kawasaki PII: DOI: Reference:

S2213-3437(18)30357-9 https://doi.org/10.1016/j.jece.2018.06.047 JECE 2472

To appear in: Received date: Revised date: Accepted date:

14-4-2018 29-5-2018 22-6-2018

Please cite this article as: Ogata F, Nakamura T, Kawasaki N, Adsorption capability of virgin and calcined wheat bran for molybdenum present in aqueous solution and elucidating the adsorption mechanism by adsorption isotherms, kinetics, and regeneration, Journal of Environmental Chemical Engineering (2018), https://doi.org/10.1016/j.jece.2018.06.047 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Journal of Environmental Chemical Engineering

IP T

Adsorption capability of virgin and calcined wheat bran for molybdenum present in aqueous solution and elucidating the adsorption mechanism by adsorption isotherms, kinetics, and

SC R

regeneration

a

M

A

N

[email protected] and [email protected]

U

Fumihiko Ogataa, Takehiro Nakamuraa, and Naohito Kawasakia,b,*

Faculty of Pharmacy, Kindai University, 3-4-1 Kowakae, Higashi-Osaka, Osaka 577-8502,

Antiaging Center, Kindai University, 3-4-1 Kowakae, Higashi-Osaka, Osaka 577-8502, Japan

CC E

PT

b

ED

Japan

Corresponding author: Naohito Kawasaki, Ph. D.

A

Faculty of Pharmacy, Kindai University, 3-4-1 Kowakae, Higashi-Osaka, Osaka 577-8502, Japan TEL: +81-6-4307-4012, e-mail: [email protected]

1

Graphical abstract

Before

After

Before

After

IP T

WB

SC R

WB200

U

WB1000

N

SEM images and qualitative analysis of adsorbents surface before and after adsorption of Mo High

M

A

Low

ED

Abstract

PT

In this study, we prepared wheat bran (WB), a type of waste biomass, and studied the characteristics of virgin WB and WB calcined at 200, 400, 600, 800, and 1000 °C (denoted by

CC E

WB200, WB400, WB600, WB800, and WB1000). Subsequently, their adsorption isotherms, kinetics, and regeneration were evaluated. Specific surface area of calcined WB is larger

A

compared to that of virgin WB. Amount of molybdenum (Mo) adsorbed is in the following order: WB400 (0 mg/g) = WB600 (0 mg/g) < WB800 (2.9 mg/g) < WB200 (12.9 mg/g) < WB (24.7 mg/g) < WB1000 (29.8 mg/g). The data for adsorption isotherms was applied to both the Freundlich (0.911–0.989) and the Langmuir (0.985–0.992) models. The amount of Mo adsorbed 2

increased with increasing temperature and decreasing pH of the solution. We confirmed that the intensity of Mo on the adsorbent surface was greater after the adsorption treatment than before

IP T

the treatment. In addition, the amount of Mo adsorbed on virgin WB was greater than that adsorbed on WB treated with different concentrations of hydrochloric acid, which suggests that

SC R

the adsorption mechanism was related to the three-dimensional protein structure. Finally,

adsorbed Mo on WB could be easily desorbed by treatment with sodium hydroxide solution.

U

The recovery percentage of Mo using 1 and 100 mmol/L sodium hydroxide solution is 95.0 %

N

and 94.2 % respectively. These results indicate that WB has great potential for Mo adsorption

M

A

from aqueous solutions.

PT

ED

Key words: Wheat bran, Molybdenum, Adsorption, Biomass

CC E

1. Introduction

Molybdenum (Mo) is a trace element, which is abundant in nature and is required by the

A

human body for many important biological and physical processes [1-3]. It is extensively utilized in industries and is economically critical as a component of fertilizers, catalysts, metal alloys, and anti-corrosive agents [4-7]. Molybdenum is primarily produced from molybdenite, its high-grade sulphide ore, and wulfenite or powellite through oxidative roasting, purification

3

of calcine, and hydrogen-reduction of molybdenum oxide [8, 9]. Molybdenum is always associated with heavy metals such as copper, iron, and other trace elements. Therefore, an

IP T

increase in the production and use of Mo presents a potential hazard for the increase in its release and distribution in the natural (aquatic) environment [1]. Mo occurs principally in the

SC R

hexavalent oxidation state as molybdate oxoanions (MoO42-), formed from condensed species in acid media [10]. Pollution by molybdate oxoanions in groundwater causes contamination in

U

various sources of drinking water such as that obtained from wells. For example, previous

N

studies have reported that Mo was present in 32.7 % of surface-water samples obtained from 15

M

A

major river basins in the USA, at concentrations ranging from 2 to 1500 μg/L (mean 60 μg/L) [10,11]. Therefore, removal and recovery of Mo from aquatic bodies is of utmost importance

ED

from an environment protection point of view [8].

PT

The fast, efficient, and economical method of adsorption is one of the most popular

CC E

techniques for removing trace elements from aqueous solutions. Several adsorbents are known to remove Mo from water. Due to their wide availability as agricultural or industrial waste, and

A

ease of chemical modification, a promising strategy is to fabricate waste biomass materials as adsorbents for selective uptake of polluting metal ions [12]. Previous studies have reported the adsorption capability of waste biomass wheat bran (WB) for heavy metals (cadmium and lead ions) and evaluated the adsorption mechanism [13-

4

15]. In addition, 54 % of WB content is dietary fibers, which is composed of cellulose, hemicellulose, and pectin, which are very useful in the adsorption of heavy metals [16]. These

IP T

findings indicate that WB has a potential for the removal of harmful ions from aqueous solutions by adsorption. However, there is no report about the Mo adsorption capacity of WB in

SC R

aqueous solutions. Therefore, if the adsorption of Mo by WB could be explored, the value and applicability of WB would drastically increase.

U

The aim of this study was to explore the extent of adsorption of Mo using WB.

N

Untreated and calcined WB were prepared, and their properties were investigated. In addition,

M

A

we evaluated the adsorption kinetics and isotherms, the effect of pH and temperature on the

ED

adsorption process, and desorption of Mo from the WB.

CC E

2.1. Materials

PT

2. Materials and Methods

Wheat bran (WB) was purchased from Nisshin Seifun Group Inc. (Japan). Molybdenum

A

standard solution (Mo in a solution containing 0.4 mol/L HCl・0.2 mol/L HNO3), hydrochloric acid, and sodium hydroxide solution were purchased from Wako Pure Chemical Industries, Ltd (Japan). Calcined WB was prepared by treating virgin WB in a muffle furnace at temperatures of 200, 400, 600, 800, and 1000°C for 2 h (denoted by WB200, WB400, WB600, WB800, and

5

WB1000, respectively). Additionally, virgin WB was treated with hydrochloric acid at concentrations of 0.01, 0.1, 1.0, and 6.0 mol/L (denoted by WB0.01, WB0.1, WB1.0, and

IP T

WB6.0, respectively). Virgin WB (1 g) was added to 50 mL of the hydrochloric acid solutions (0.01, 0.1, 1.0, and 6.0 mol/L). The suspensions were shaken at 100 rpm for 24 h at 25°C. The

SC R

sample was then filtered through a Buchner funnel type glass filter 3G-3 (SANSHO, Japan), and the filtrate was washed with distilled water. Then, the WB obtained after treatment with

U

hydrochloric acid was dried and used for the experiment.

N

The characteristics of samples were determined by the following method. The

M

A

morphology of the samples was measured by scanning electron microscopy (SEM, SU1510, Hitachi, Ltd., Japan). The specific surface area measurement and thermogravimetric-differential

ED

thermal analysis (TG-DTA) were performed using a NOVA4200e specific surface analyzer

PT

(Yuasa Ionics, Japan) and TG8120 (Rigaku, Japan), respectively. In addition, the distribution of

CC E

Mo on the adsorbent surface was measured using an electron microanalyzer JXA-8530F (JEOL,

A

Japan), at an accelerating voltage of 15.0 kV and a beam diameter of 5 µm.

2.2. Amount of Mo adsorbed on virgin WB, calcined WB, and WB treated with hydrochloric acid The adsorbent (0.05 g) was added to 50 mL of the Mo solution (50 mg/L). The suspension was shaken at 100 rpm for 24 h at 25 °C. The sample was then filtered through a

6

0.45 µm membrane filter, and the filtrate was analyzed using an inductively coupled plasma optical emission spectrometry iCAP-7600 (ICP-OES, Thermo Fisher Scientific Inc., Japan). The amount of Mo adsorbed was calculated by using Eq. (1):

IP T

q = (C0 − Ce) V/W

(1)

SC R

where q is the amount of Mo adsorbed (mg/g), C0 is the initial concentration (mg/L), Ce is the equilibrium concentration (mg/L), V is the solvent volume (L), and W is the weight of the

N

U

adsorbent (g). The data were presented as the mean ± S.D. of 2-3 experiments.

M

A

2.3. Adsorption capability of WB, WB200, and WB1000 for Mo

For isotherm studies, 0.05 g adsorbent was added to 50 mL of the Mo solutions of

ED

different initial concentrations (10–50 mg/L). The suspensions were shaken at 100 rpm for 24 h

PT

at 5, 25, and 50°C. For kinetic studies, 0.05 g adsorbent was added to 50 mL of the Mo solution

CC E

(50 mg/L). The suspension was shaken at 100 rpm for 0.5, 1, 3, 6, 24, 48, and 65 h at 25°C. The effect of pH on the adsorption was experimented by following procedure, 0.05 g adsorbent was

A

added to 50 mL of the Mo solution (50 mg/L, pH 2–10). The pH of the solution was adjusted using hydrochloric acid and sodium hydroxide. The suspension was shaken at 100 rpm for 24 h at 25°C. The amount of Mo adsorbed was calculated by using Eq. (1). The data were presented as the mean ± S.D. of 2-3 experiments.

7

2.4. Adsorption and desorption capability of WB for Mo after treatment with sodium hydroxide

IP T

solution The adsorbent (1.8 g) was added to 300 mL of the Mo solution (300 mg/L). The

SC R

suspension was shaken at 100 rpm for 24 h at 25°C. Subsequently, the suspension was filtered

through a 0.45 µm membrane filter, and the filtrate was analyzed using ICP-OES. The amount

U

of Mo adsorbed was calculated by using Eq. (1). After adsorption, the adsorbent was collected,

N

dried, and then used for the desorption experiment. The collected adsorbent (0.05 g) was added

M

A

to 50 mL of sodium hydroxide solutions (1 and 100 mmol/L). The suspensions were shaken at 100 rpm for 24 h at 25°C, and were filtered through a 0.45 µm membrane filter. The

(2)

PT

d = CeV/W

ED

concentration of Mo in sample solution was calculated by Eq. (2):

CC E

where d is the amount desorbed (mg/g), Ce is the concentration after the desorption (mg/L), V is the solvent volume (L), and W is the weight of the adsorbent sample (g). The data

A

were presented as the mean ± S.D. of 2-3 experiments.

3. Results and Discussions 3.1. Properties of adsorbent

8

We previously reported the properties of WB (acidic functional groups, basic functional groups, and pH was 4.65 mmol/g, 0.24 mmol/g, and 6.94, respectively) [13-15]. WB is

IP T

composed of protein (19 g/100 g), lipid (7.4 g/100 g), carbohydrate (25 g/100 g), dietary fiber (37 g/100 g), sodium (2–7 mg/100 g), calcium (93 mg/100 g), iron (13 mg/100 g), magnesium

SC R

(489 mg/100 g), and zinc (10 mg/100 g). These data were obtained from the Nisshin Seifun

Group Inc. (Japan). The yield percentage of WB200, WB400, WB600, WB800, and WB1000

U

used in this study was 90.4, 38.3, 29.2, 27.1, and 22.6 %, respectively. The SEM images of

N

adsorbents are shown in Fig. 1. We confirmed the roughness on the WB surface. Subsequently,

M

A

the calcination treatment produced pores on the surface of WB samples, which indicates that the specific surface area of WB samples increased with increasing calcination temperatures. The

ED

specific surface area of WB, WB200, WB400, WB600, WB800, and WB1000 was 1.5, 1.9, 0,

PT

10.0, 260.9, and 197.1 m2/g, respectively. The results for the thermal analysis of the WB

CC E

samples are shown in Fig. 2. At approximately 100°C, an endothermic peak was observed on the DTA curve of the WB samples, which suggests that the adhesion water was lost

A

(dehydration reaction had occurred). Additionally, the organic compounds and the fatty acids were burned at approximately 300°C on the DTA curve of the WB. Therefore, there were very small differences among the TGA and DTA curves for WB400, WB600, WB800, and WB1000. Finally, we obtained a carbonaceous material, having different characteristics from waste

9

biomass WB.

IP T

3.2. Adsorption capability of WB samples for Mo Figure 3 shows the amount of Mo adsorbed on WB samples. The amount adsorbed is in

SC R

the order: WB400 (0 mg/g) = WB600 (0 mg/g) < WB800 (2.9 mg/g) < WB200 (12.9 mg/g) <

WB (24.7 mg/g) < WB1000 (29.8 mg/g). In this study, we measured the distribution of Mo on

U

adsorbent surface for elucidating the adsorption mechanism (Fig. 4). From the SEM images, the

N

morphology of the adsorbent surface did not change from before and after the adsorption

M

A

treatment, and subsequently the intensity of Mo on adsorbent surface increased after adsorption as compared to the intensity before adsorption. These results suggest that the adsorbent surface

ED

is an important factor for adsorbing Mo from an aqueous solution. Subsequently, we evaluated

PT

the relationship between the amount of Mo adsorbed and the specific surface area of the

CC E

adsorbent. However, no positive correlation was found between the two. The adsorption mechanism of Mo using WB samples was different at different calcination temperatures. The

A

adsorption capability of calcined WB (WB600, WB800, and WB1000), which is essentially a carbonaceous material after calcination treatment, was previously reported to be dependent upon its physical properties (such as the specific surface area and pore volumes) [17]. A similar trend was observed in this study. Previous studies have reported that the adsorption capacity of WB

10

for heavy metals (cations) depends upon the components in WB (the pectin and carboxyl groups) [13-15]. In addition, the dietary fiber in biomass is also related to the adsorption

IP T

capability of WB for Mo [8]. We previously reported that the adsorption capability of virgin biomass is related to the three-dimensional structure of proteins present in it [18]. Therefore, we

SC R

evaluated the adsorption capability of WB treated with hydrochloric acid for Mo (Fig. 5, the protein structures in WB are altered by hydrochloric acid treatment). The amount of Mo

U

adsorbed is in the following order: WB6.0 (16.1 mg/g) < WB 1.0 (19.9 mg/g) < WB 0.1 (21.7

N

mg/g) < WB0.01 (23.2 mg/g) < WB (24.7 mg/g). The amount of Mo adsorbed decreased with

M

A

decreasing pH, which indicates that the protein structure was altered by hydrochloric acid, and subsequently the adsorption sites for Mo were lost. A similar trend was reported in a previous

ED

study [18]. The data obtained in our study revealed that the protein in WB is also an important

PT

factor for adsorption of Mo from aqueous solutions. In addition, previous study reported that the

CC E

pHpzc value of acid-treated biomass (pine corn) using 0.1 mol/L hydrochloric acid was shifted to acidic region compared to raw pine [19]. Similar trend was occurred in this study, which

A

indicates that the pHpzc value of WB decreased with increasing the concentration of hydrochloric acid (WB > WB0.01 > WB0.1 > WB1.0 > WB6.0). The predominant charges of Mo are negative (The distribution of different Mo species found in solutions are MoO42-, HMoO4-, H2MoO4, Mo7O21(OH)33-, Mo7O21(OH)24-, Mo7O23(OH)5-, and Mo7O246-) [20].

11

Therefore, amount of Mo adsorbed using WB was higher than that of WB treated with hydrochloric acid (WB0.01, WB0.1 > WB1.0 > WB6.0). The pHpzc value was also related to the

IP T

adsorption capability of Mo.

SC R

3.3. Adsorption isotherms of WB, WB200, and WB1000 for Mo

Adsorption isotherms of WB, WB200, and WB1000 for Mo are shown in Fig. 6.

U

Amount of Mo adsorbed on WB, WB200, and WB1000 increased with increasing temperatures.

N

The amount of Mo adsorbed was in the following order: WB200 < WB < WB1000. Adsorption

M

A

isotherms describe how molecules or ions of an adsorbate interact with the sorbent surface sites and its degree of accumulation on the sorbent surface at a constant temperature [8]. The

ED

Freundlich model empirically describes the relationship between sorption density and dissolved

PT

concentration at equilibrium, where sorption density refers to the mass in milligram of a

CC E

chemical adsorbed to the solid surface of an adsorbent material, and concentration refers to the mass of that chemical per unit volume of solution in contact with the sorbent [21-23]. qe = KFCe1/n

A

(3)

where Ce is the equilibrium concentration of Mo (mg/L), qe is the amount of Mo required for forming a monolayer onto the sorbent surface (mg/g), and KF and 1/n are the Freundlich equilibrium constant and the coefficient of heterogeneity in the Freundlich sorption isotherm

12

equation, respectively [10]. The Langmuir model describes the sorption of a solute in a single layer on the surface of

IP T

a sorbent with a finite number of identical sites without surface diffusion [23]. qe = qmKLCe/(1+KLCe)

(4)

SC R

where Ce is the equilibrium concentration of Mo (mg/L), qe is the amount of Mo required to form a monolayer on the sorbent surface (mg/g), qm is the binding strength, and KL is the

U

Langmuir equilibrium constant.

N

The correlation coefficient indicates that both the Freundlich (0.911–0.989) and

M

A

Langmuir (0.985–0.992) isotherm equations are good fits for the data corresponding to Mo adsorption on WB (Table 1). The value of the maximum adsorption capacity of WB1000

ED

calculated from Langmuir isotherm model was found to be 84.0 mg/g. It is apparent that the

PT

uptake efficiency of WB1000 for Mo from aqueous solutions is the highest [1, 4]. The

CC E

experimental qe value was lower than qm, which suggest that the adsorbent surface was not fully covered by Mo in this experimental condition. Similar trends were reported by previous studies

A

[24,25]. This adsorption capacity is much higher than that of the other adsorbents investigated previously, such as maghemite (33.4 mg/g), nano-magnetic CuFe2O4 (30.6 mg/g), modified mesoporous zirconium silicate (22.8 mg/g), ZnCl2 activated coir pith carbon (14.4 mg/g), waste Fe(III)/Cr(III) hydroxide (12.3 mg/g), and iron-based adsorbents (10.4 mg/g) [1-3, 26-29]. In

13

addition, Mo was easily adsorbed on the WB when 1/n was in the range of 0.1–0.5 but not when 1/n > 2. These findings are also consistent with previous reports, according to which Mo

IP T

adsorption readily occurred when 1/n < 2 (0.71–1.14) [30]. Moreover, previous study reported that a favourable biosorbent should have a low Langmuir constant KL and a qm high value. In

SC R

this study, KL and a qm values were found to be 0.02–0.08 and 33.4– 80.6 mg/g, respectively.

This result indicates that the biomass adsorbent is an encouraging biosorbent for Mo removal

U

from aqueous solution [31]. Therefore, the adsorption of Mo on the WB is attributed to

3.4. Adsorption thermodynamics

M

A

N

monolayer adsorption in this study.

ED

Thermodynamic parameters, free energy change (ΔG), enthalpy change (ΔH), and

PT

entropy change (ΔS) were calculated using the following equations. ΔG = - RTlnK

CC E

(5)

lnK =ΔS/R -ΔH/RT

(6)

A

where R is the universal gas constant (8.314 J/mol K), T is the absolute temperature (K)

and K is adsorption equilibrium constant. Thus, ΔH and ΔS are determined from the slop and intercept. The obtained results are listed in Table 2. It is clear from thermodynamic parameters that ΔG becomes progressively more negative suggesting increasing spontaneity in adsorption

14

as the temperature was increasing from 278 K to 323 K. Moreover, ΔH indicates the endothermic nature of adsorption process. This is supported by the increase of amount adsorbed

IP T

with increasing temperature, as shown in Fig. 6. The positive value of ΔS shows the increased

SC R

randomness at the solid/solution interface during the adsorption of Mo on adsorbents [8,32,33].

3.5. Effect of contact time on the adsorption of Mo on WB, WB200, and WB1000

U

Figure 7 shows the effect of contact time on the adsorption of Mo on WB, WB200, and

N

WB1000. It shows that Mo was adsorbed rapidly within 6 h. After 24–65 h, the amount of Mo

M

A

adsorbed increased only slightly. Considering the application of adsorbents in the fields, it is recommended to shorten the contact time on the adsorption. Therefore, we decided that a 24 h

ED

was sufficient to adsorb the Mo from aqueous solution. To determine the time to reach

PT

adsorption equilibrium for Mo, a batch experiment was carried out by exposing adsorbent to Mo

CC E

solution for different contact times. In this study, the Lagergren’s first-order rate equation [34]

A

and pseudo-second-order rate equation [35] were employed. ln (qe – qt)/qe = - k1t

(7)

t/qt = 1/(k2qe2) + t/qe

(8)

where qe and qt are the amounts of Mo adsorbed at equilibrium and at time t (mg/g), respectively, k1 is the first-order rate constant (1/h), and k2 is the pseudo-second-order rate

15

constant (g/mg.h). The first-order and pseudo second-order model constants for the adsorption of Mo are

IP T

shown in Table 3. The correlation coefficients of both the first-order model (0.998-0.999) and pseudo-second-order model (0.981-0.988) are very high. Moreover, the value of qe,exp was closer

SC R

to that of qe,cal in the pseudo-second-order kinetic model than that in the first-order model

[23,32]. This indicates that adsorption of Mo involves two species, in case of the Mo and the

U

WBs (adsorbent) [25]. The values of the rate constant k2 are found to the different for WB,

N

WB200, and WB1000, showing the process to be concentration-dependent. These results

M

A

demonstrate that the pseudo-second-order kinetic model yields a better fit, which indicates that the adsorption of Mo is controlled by chemical sorption or chemisorption involving valence

ED

forces, through sharing or exchanging of electrons between adsorbate and adsorbent. Similar

CC E

PT

works were reported by many researchers [25].

3.6. Effect of pH on the adsorption of Mo on WB, WB200, and WB1000

A

In general, the process of adsorption for removal of metal ions from aqueous solutions

is highly dependent on the pH of the solution. Therefore, it is very important to elucidate the optimal pH condition for the adsorption of Mo and its species. Experiments were carried out at a pH range of 2.0–10.0 to verify its effect on Mo adsorption on WB, WB200, and WB1000 (Fig.

16

8). Amount of Mo adsorbed on WB decreased with increasing pH of the solution. The optimal pH for adsorption of Mo is approximately 1.5. Previous studies have reported that the distribution of different Mo species found in solutions are MoO42-, HMoO4-, H2MoO4,

IP T

Mo7O21(OH)33-, Mo7O21(OH)24-, Mo7O23(OH)5-, and Mo7O246- [20]. In addition, WB is

SC R

comprised of the dietary fiber, protein, lipid, saccharides, etc. Therefore, the hydroxyl groups (– OH) present on the surface of WB act as the major functional groups in adsorption. As the pH

U

becomes neutral, the amount of Mo adsorbed is almost zero, because at neutral pH, the

N

adsorption site (hydroxyl groups) are negatively charged, which increases electrostatic repulsion

M

A

between Mo species and WB surface [8]. Abovementioned, the pHpzc value of WB is one of the most important factors for adsorption of Mo. The pHpzc value of WB is 6.19, which suggesting

ED

that the characteristic of WB is in agreement with the adsorption behavior of Mo in Fig. 8.

PT

Moreover, a previous study has reported the adsorption mechanism of Mo using Crab Shells Gel

CC E

(including the hydroxyl groups). This report showed that the adsorption mechanism of Mo using Crab Shell Gel involves esterification of H2MoO4 with hydroxyl groups on Crab Shell Gel when

A

pH < 1.5 and electrostatic interaction between MoO42- with hydroxyl groups on Crab Shell Gel when pH > 1.5 [8]. Similar trends are suspected to occur in several different adsorbents [36, 37].

3.7. Desorption capability of WB for Mo in presence of sodium hydroxide

17

To keep the processing cost down and to open the possibility of recovering Mo from aqueous solution, it is desirable to regenerate the WB. In this study, sodium hydroxide was

IP T

selected as the regeneration agent because of its wide use for desorption of heavy metal or rare metal ions from adsorbent surface. Figure 9 shows the desorption percentage of Mo using

SC R

sodium hydroxide. Recovery percentage using 1 or 100 mmol/L sodium hydroxide solution was

95.0 % (32.5 mg/g adsorbed and 30.9 mg/g desorbed) and 94.2 % (32,5 mg/g adsorbed and 30.6

U

mg/g desorbed), respectively. It was found that the desorption efficiency was almost the same

N

when using either 1 or 100 mmol/L sodium hydroxide solution. It is clear that hydroxyl ions

M

A

could replace Mo oxoanions on the adsorbent sites on WB. Previous studies also report a similar

PT

4. Conclusions

ED

phenomenon [4, 25].

CC E

The wheat bran (WB) as waste biomass was selected as the adsorbent to evaluate the adsorption isotherms, kinetics, effect of contact time and temperature, and regeneration of Mo

A

adsorbed from aqueous solution. The amount of Mo adsorbed on WB increased with increasing temperature of the solution. The adsorption kinetics followed the pseudo-second-order model, and adsorption isotherms data fitted to both the Freundlich and the Langmuir models. Adsorption mechanism of Mo was related to the hydroxyl groups on the surface of the

18

adsorbent and the three-dimensional structure of protein molecules present in WB. Additionally, adsorbed Mo on WB was desorbed by sodium hydroxyl solution with a recovery percentage of

IP T

over 94 %. Therefore, WB has great potential for Mo adsorption/desorption. Thus, this study

SC R

found that WB as waste biomass is efficient for Mo adsorption from aqueous solution.

Acknowledgment

U

This work was supported by the MEXT-Supported Program for the Strategic Research

A

CC E

PT

ED

M

A

N

Foundation at Private Universities, 2014–2018.

19

References [1] Y.J. Tu, C.F. You, C.K. Chang, T.S. Chan, S.H. Li, XANES evidence of molybdenum

IP T

adsorption onto novel fabricated nano-magnetic CuFe2O4, Chem. Eng. J. 244 (2014) 343-349. [2] J.L. Johnson, H.P. Jones, K.V. Rajagopalan, In vitro reconstitution of demolybdosulfite

SC R

oxidase by a molybdenum cofactor from rat liver and other sources, J. Biol. Chem. 252 (1977) 4994–5003.

U

[3] A. Afkhami, R. Norooz-Asl, Removal, preconcentration and determination of Mo(VI) from

N

water and wastewater samples using maghemite nanoparticles, Colloids Surf. A: Physicochem.

M

A

Eng. Aspects 346 (2009) 52–57.

[4] Y.J. Tu, T.S. Chan, H.W. Tu, S.L. Wang, C.F. You, C.K. Chang, Rapid and efficient

ED

removal/recovery of molybdenum onto ZnFe2O4 nanoparticles, Chemosphere 148 (2016) 452-

PT

458.

CC E

[5] Y. Nakashima, Y. Inoue, T. Yamamoto, W. Kamichatani, S. Kagaya, A. Yamamoto, Determination of molybdate in environmental water by ion chromatography coupled with a

A

preconcentration method employing a selective chelating resin, Anal. Sci. 28 (2012) 1113-1116. [6] D. Kosson, F. Sanchez, P. Kariher, L.H. Turner, R. Delapp, P. Seignette, Characterization of coal combustion residues from electric utilities-leaching and characterization data, Technical report prepared for the U.S. EPA. 2009.

20

[7] J.P. Gustafsson, Modelling molybdate and tungstate adsorption to ferrihydrite, Chem. Geol. 200 (2003) 105-115.

IP T

[8] Y. Xiong, Y. Li, F. Ren, L. Wan, Z. Xing, Z. Lou, W. Shan, Optimization of Mo(VI) selective separation by Eriocheir sinesis Crab Shells Gel, Ind. Eng. Chem. Res. 53 (2014) 847-854.

SC R

[9] B.S. Kim, M.K. Jha, J. Jeong, J. Lee, Leaching of impurities for the up-gradation of

molybdenum oxide and cementation of copper by scrap iron, Int. J. Miner. Process 88 (2008) 7-

U

12.

N

[10] F.A. Bertoni, A.C. Medeot, J.C. González, L.F. Sala, S.E. Bellú, Application of green

M

A

seaweed biomass for MoVI sorption from contaminated waters. Kinetic, thermodynamic and continuous sorption studies, J. Colloid Inter. Sci. 446 (2015) 122-132.

ED

[11] P.L. Smedley, H.B. Nicolli, D.M.J. Macdonald, A.J. Barros, J.O. Tullio,

PT

Hydrogeochemistry of arsenic and other inorganic constituents in groundwaters from La Pampa.

CC E

Argentina, Appl. Geochem. 17 (2002) 259–284. [12] W. Shan, F. Ren, Q. Zhang, L. Wan, Z. Xing, Z. Lou, Y. Xiong, Enhanced adsorption

A

capacity and selectivity towards molybdenum in wastewater by a persimmon tannin waste based new adsorbent, J. Chem. Technol. Biotechnol. 90 (2015) 888-895. [13] F. Ogata, M. Kangawa, H. Tominaga, Y. Tanaka, A. Ueda, Y. Iwata, N. Kawasaki, Study of adsorption mechanism of heavy metals onto waste biomass (Wheat bran), J. Oleo. Sci. 62

21

(2013) 949-953. [14] F. Ogata, M. Kangawa, Y. Iwata, A. Ueda, Y. Tanaka, N. Kawasaki, A study on the

IP T

adsorption of heavy metals by using raw wheat bran bioadsorption in aqueous solution phase, Chem. Pharm. Bull. 62 (2014) 247-253.

SC R

[15] F. Ogata, H. Tominaga, M. Kangawa, N. Kawasaki, Adsorption of cadmium ions by wheat bran treated with pectinase, Chem. Phar. Bull. 59 (2011) 1400-1402.

U

[16] A.L. Debbaudt, M.L. Ferreira, M.E. Gschaidar, Theoretical and experimental study M2+

N

adsorption on biopolymers. III. Comparative kinetic pattern of Pb, Hg, and Cd, Carb. Polym. 56

M

A

(2004) 321-332.

[17] F. Ogata, H. Tominaga, H. Yabutani, N. Kawasaki, Removal of fluoride ions from water by

ED

adsorption onto carbonaceous materials produced from coffee grounds, J. Oleo Sci. 60 (2011)

PT

619-625.

CC E

[18] N. Kawasaki, H. Tominaga, F. Ogata, K. Kakehi, Removal of cadmium and copper by vegetable biomass treated with hydrochloric acid, Chem. Eng. J. 157 (2010) 249-253.

A

[19] S. Dawood, T.K. Sen, Removal of anionic dye congo red from aqueous solution by raw pine and acid-treated pine cone powder as adsorbent: Equilibrium, thermodynamic, kinetics, mechanism and process design, Water Res. 46 (2012) 1933-1946. [20] E. Guibal, C. Milot, J.M. Tobin, Metal-anion sorption by chitosan beads: equilibrium and

22

kinetic studies, Ind. Eng. Chem. Res. 37 (1998) 1454-1463. [21] T.A.T. Aboul-Kassim, B.R.T. Simoneit, Pollutantsolid phase interactions: mechanism,

IP T

chemistry and modeling, Berlin, New York, Springer, 2001. [22] S.F. Yang, C.F. Lin, Y.C. Lin Angela, P.K. Hong Andy, Sorption and biodegradation of

under aerobic conditions, Water Research 45 (2011) 3389–3397.

SC R

sulfonamide antibiotics by activated sludge: experimental assessment using batch data obtained

N

and iron minerals, Water Air Soil Pollut. 224 (2013) 1-16.

U

[23] C. Geng, X. Jian, Y. Su, Q. Hu, Assessing molybdenum adsorption onto an industrial soil

M

A

[24] A. Özer, D, Özer, Comparative study of the biosorption of Pb(II), Ni(II) and Cr(VI) ions onto S. cerevisiae: determination of biosorption heats, J. Hazard. Mater. B100 (2003) 219-229.

ED

[25] O.S. Lawal, A.R. Sanni, I.A. Ajayi, O.O. Rabiu, Equilibrium, thermodynamic and kinetic

PT

studies for the biosorption of aqueous lead(II) ions onto the seed husk of Calophyllum

CC E

inophyllum, J. Hazard. Mater. 177 (2010) 829-835. [26] H. Sepehrian, S.W. Husain, J. Fasihi, M.K. Mahani, Adsorption behavior of molybdenum

A

on modified mesoporous zirconium silicates, Sep. Sci. Technol. 45 (2010) 421–426. [27] C. Namasivayam, D. Sangeetha, Removal of molybdate from water by adsorption onto ZnCl2 activated coir pith carbon, Bioresour. Technol. 97 (2006) 1194–1200. [28] C. Namasivayam, K. Prathap, Uptake of molybdate by adsorption onto industrial solid

23

waste Fe(III)/Cr(III) hydroxide: kinetic and equilibrium studies, Environ. Technol. 27 (2006) 923–932.

IP T

[29] G. Dodbiba, T. Fujita, T. Kikuchi, J. Manjanna, S. Matsuo, H. Takahashi, K. Tohji, Synthesis of iron-based adsorbents and their application in the adsorption of molybdenum ions

SC R

in nitric acid solution, Chem. Eng. J. 166 (2011) 496–503.

[30] I. Abe, K. Hayashi, M. Kitagawa, Adsorption of non-ionic surfactants, Yukagaku 25 (1976)

U

145-150.

N

[31] D. Kratochvil, B. Volesky, Advances in the biosorption of heavy metals, Trends Biotechnol.

M

A

16 (1998) 291-300.

[32] Y.C. Chen, C. Lu, Kinetics, thermodynamics and regeneration of molybdenum adsorption

PT

(2014) 2521-2527.

ED

in aqueous solutions with NaOCl-oxidized multiwalled carbon nanotubes, J. Ind. Eng. Chem. 20

CC E

[33] A.A. Narvekar, J.B. Fernandes, S.G. Tilve, Adsorption behavior of methylene blue on glycerol based carbon materials, J. Environ. Chem. Eng. 6 (2018) 1714-1725.

A

[34] E. Tütem, R. Apak, Ç.F. Ünal, Adsorptive removal of chlorophenols from water by bituminous shale, Water Res. 32 (1998) 2315-2324. [35] Y.S. Ho, G. McKay, The kinetics of sorption of divalent metal ions onto sphagnum moss flat, Water Res. 34 (2000) 735-742.

24

[36] J.J. Lian, S.G. Xu, C.W. Yu, C.W. Han, Removal of Mo(VI) from aqueous solutions using sulfuric acid-modified cinder: kinetic and thermodynamic studies, Toxicol. Environ. Chem. 94

IP T

(2012) 500-511. [37] Z. Zhao, J. Liu, W. Xia, C. Cao, X. Chen, H. Li, Surface complexation modeling of soluble

A

CC E

PT

ED

M

A

N

U

SC R

molybdenum adsorption by Mn3O4, J. Chem. Technol. Biotechnol. 85 (2010) 121-126.

25

Figure captions

IP T

Fig. 1. SEM images of virgin and calcined wheat bran. Fig. 2. Thermal analysis of adsorbents under an air atmosphere.

SC R

Fig. 3. Amount of Mo adsorbed onto WBs.

Initial concentration: 50 mg/L, solvent volume: 50 mL, adsorbent: 0.05 g, temperature: 25℃,

U

contact time: 24 hr, agitation speed: 100 rpm

N

Fig. 4. SEM images and qualitative analysis of adsorbents surface before and after adsorption of

M

A

Mo

Fig. 5. Amount of Mo adsorbed onto WB treated with hydrochloric acid.

ED

Initial concentration: 50 mg/L, solvent volume: 50 mL, adsorbent: 0.05 g, temperature: 25℃,

PT

contact time: 24 hr, agitation speed: 100 rpm

CC E

Fig. 6. Adsorption isotherms of Mo onto WB, WB200, and WB1000. Initial concentration: 10–50 mg/L, solvent volume: 50 mL, adsorbent: 0.05 g, temperature: 5,

A

25, 50 ℃, contact time: 24 hr, agitation speed: 100 rpm Fig. 7. Effect of contact time on the adsorption of Mo. Initial concentration: 50 mg/L, solvent volume: 50 mL, adsorbent: 0.05 g, temperature: 25℃, contact time: 0.5–48 hr, agitation speed: 100 rpm

26

Fig. 8. Effect of pH on the adsorption of Mo. Initial concentration: 50 mg/L, solvent volume: 50 mL, solution pH: 2–10, adsorbent: 0.05 g,

IP T

temperature: 25℃, contact time: 24 hr, agitation speed: 100 rpm Fig. 9. Desorption percentage of Mo using sodium hydrocide.

SC R

Adsorption condition: Initial concentration of Mo: 300 mg/L, solvent volume: 300 mL, adsorbent: 1.8 g, temperature: 25℃, contact time: 24 hr, agitation speed: 100 rpm

U

Desorption condition: : Initial concentration of sodium hydroxide : 1 and 100 mmol/L, solvent

M

A

N

volume: 50 mL, temperature: 25℃, contact time: 24 hr, agitation speed: 100 rpm

WB200

WB400

WB800

WB1000

PT

ED

WB

A

CC E

WB600

Fig. 1. SEM images of virgin and calcined wheat bran.

27

IP T SC R U N A 100

40

120

20

100

80

M

WB

120

WB200

20

100

ED

0 200

400

600

800

WB600

120

CC E

100

20

-60 1000

0

40

120

20

100

80

600

800

WB800

-40

20

-60 1000

0

120

20

100

800

400

600

800

-60 1000

WB1000

40 20

0

0 60

-20 40

600

200

80

-20

0

-40

0

40

60

20

400

400

0

40

200

200

-20 40

80

60

0

0

0 60

-40

20

-60 1000

0

-20 40

0

200

400

600

800

-40

20

-60 1000

0

-40

0

200

400

600

800

-60 1000

Temperature (℃)

Fig. 2. Thermal analysis of adsorbents under an air atmosphere.

28

DTA(μV)

PT

0

-40

20

-20

40

20

40

0

60

-20

40

WB400

80

0

TGA(%)

120

80

60

A

40

IP T SC R U N M

A 25 20

A

CC E

PT

Amount adsorbed (mg/g)

30

ED

35

15 10 5

0 WB

WB200 WB400 WB600 WB800 WB1000

Sample

Fig. 3. Amount of Mo adsorbed onto WBs. Initial concentration: 50 mg/L, solvent volume: 50 mL, adsorbent: 0.05 g, temperature: 25℃, contact time: 24 hr, agitation speed: 100 rpm

29

IP T SC R U N A Before

After

PT

ED

WB

After

M

Before

CC E

WB200

A

WB1000

Fig. 4. SEM images and qualitative analysis of adsorbents surface before and after adsorption of Mo High

Low

30

IP T SC R U N M

A 20

PT

15

ED

25

10

5

CC E

Amount adsorbed (mg/g)

30

A

0

WB

WB0.01

WB0.1

WB1.0

WB6.0

Sample

Fig. 5. Amount of Mo adsorbed onto WB treated with hydrochloric acid. Initial concentration: 50 mg/L, solvent volume: 50 mL, adsorbent: 0.05 g, temperature: 25℃, contact time: 24 hr, agitation speed: 100 rpm

31

IP T SC R U N A M

40 30

WB ▲ 5℃ ■ 25℃ ● 50℃

ED 10

PT

0

0

20

40

40

40

WB1000 30

20

20

10

10

0

A

0

60

WB200

30

CC E

Amount adsorbed (mg/g)

20

0 20

40

60

0

20

40

60

Equilibrium concentration (mg/L)

Fig. 6. Adsorption isotherms of Mo onto WB, WB200, and WB1000. Initial concentration: 10–50 mg/L, solvent volume: 50 mL, adsorbent: 0.05 g, temperature: 5, 25, 50 ℃, contact time: 24 hr, agitation speed: 100 rpm

32

IP T SC R U N A M ED

WB1000

WB

WB200

A

CC E

PT

Amount adsorbed (mg/g)

45 40 35 30 25 20 15 10 5 0

0

20

40

60

Elapsed time (hr)

Fig. 7. Effect of contact time on the adsorption of Mo. Initial concentration: 50 mg/L, solvent volume: 50 mL, adsorbent: 0.05 g, temperature: 25℃, contact time: 0.5–48 hr, agitation speed: 100 rpm

33

IP T SC R U N M

A 30

25 20

◆ WB ▲ WB200 ■ WB1000

ED

35

A

CC E

PT

Amount adsorbed (mg/g)

40

15 10 5 0

0

2

4

6

8

10

Solution pH

Fig. 8. Effect of pH on the adsorption of Mo.

Initial concentration: 50 mg/L, solvent volume: 50 mL, solution pH: 2–10, adsorbent: 0.05 g, temperature: 25℃, contact time: 24 hr, agitation speed: 100 rpm

34

100

Desorption percentage (%)

90 80 70 60 50

IP T

40 30 20

0 100 1 Concentration of NaOH (mmol/L)

SC R

10

Fig. 9. Desorption percentage of Mo using sodium hydrocide.

A

CC E

PT

ED

M

A

N

U

Adsorption condition: Initial concentration of Mo: 300 mg/L, solvent volume: 300 mL, adsorbent: 1.8 g, temperature: 25℃, contact time: 24 hr, agitation speed: 100 rpm Desorption condition: : Initial concentration of sodium hydroxide : 1 and 100 mmol/L, solvent volume: 50 mL, temperature: 25℃, contact time: 24 hr, agitation speed: 100 rpm

35

Table 1 Langmuir and Freundlich constants for the adsorption of Mo.

Langmuir constants

Freundlich constants

KL

(mg/g)

(L/mg)

WB

80.6

0.02

0.985

WB200

33.4

0.08

0.992

WB1000

84.0

0.02

1/n

KF

r

0.69

0.911

1.14

0.30

0.989

0.71

5.13

0.970

N

1.14

U

SC R

r

IP T

qm

A

Sample

A

CC E

PT

ED

M

0.991

36

Table 2 Thermodynamic parameters for the adsorption of Mo.

ΔG (kJ/mol) ΔH

ΔS

(kJ/mol)

(J/(mol K))

at temperature

22.7

61.6

WB1000

11.6

41.2

ED PT CC E A

37

323K

-7.2

-8.5

-9.2

-16.8

-18.3

-20.0

-11.4

-12.3

-13.3

U

WB200

N

28.6

A

10.6

M

WB

298K

SC R

278K

IP T

Samples

Table 3 Pseudo-first and second-order model constants for the adsorption of Mo.

qe,exp qe,cal

(h-1)

(mg/g)

k2

qe,cal

(g/mg/h)

(mg/g)

r

r

28.1

0.07

22.7

0.999

WB200

17.2

0.06

14.2

0.998

WB1000

36.7

0.07

6.4×10-3

30.4

0.988

8.6×10-3

18.8

0.981

4.2×10-3

40.2

0.986

A

N

U

WB

IP T

k1

M

(mg/g)

SC R

Sample

A

CC E

PT

ED

31.4

38

0.998