Treatment of bentazon herbicide solutions by vacuum membrane distillation

G Model

ARTICLE IN PRESS

JWPE-88; No. of Pages 6

Journal of Water Process Engineering xxx (2014) xxx.e1–xxx.e6

Contents lists available at ScienceDirect

Journal of Water Process Engineering journal homepage: www.elsevier.com/locate/jwpe

Treatment of bentazon herbicide solutions by vacuum membrane distillation Mohammad Peydayesh a , Pezhman Kazemi b , Alireza Bandegi a , Toraj Mohammadi a,∗ , Omid Bakhtiari c a Research Centre for Membrane Separation Processes, Faculty of Chemical Engineering, Iran University of Science and Technology (IUST), Narmak, Tehran, Iran b Department of Chemical Engineering, Islamic Azad University, South Tehran Branch, Tehran, Iran c Department of Chemical Engineering, Razi University, Kermanshah, Iran

a r t i c l e

i n f o

Article history: Received 7 May 2014 Received in revised form 8 October 2014 Accepted 6 November 2014 Available online xxx Keywords: Bentazon Vacuum membrane distillation Hydrophobic membrane Herbicides Modeling

a b s t r a c t Experimental investigations were carried out to treat bentazon solutions by the vacuum membrane distillation process (VMD). The effects of several parameters, including feed temperature, feed flow rate, vacuum pressure and initial bentazon feed concentration on flux quality and quantity were studied. The VMD process was found to be effective in the treatment of the bentazon solutions as the permeate was absolutely pure water. Results showed that increasing temperature and flow rate and decreasing vacuum pressure and bentazon concentration enhance permeate flux. Temperature and vacuum pressure were found to be the most important factors for permeate flux. Under the best conditions (a feed temperature of 60 ◦ C and a vacuum pressure of 30 mbar), a maximum permeate flux of 92.94 kg/m2 h was obtained. Also, a mathematical model describing the variation of bentazon concentration with time was developed and validated with the experimental results. © 2014 Elsevier Ltd. All rights reserved.

1. Introduction Due to the extensive application of agrochemicals in crop farms, orchards, fields and forest lands, the contamination of surface and ground water by herbicides has become a serious environmental problem in recent years [1]. The slow degradation of herbicides in the environment can lead to environmental contamination of water, soil, air, several types of crops and, indirectly, of humans [2]. Some of the chronic effects of these compounds are carcinogenesis, neurotoxicity, effects on reproduction and cell development effects, particularly in the early stages of life [3]. Herbicides are usually more soluble in water and less absorbed to soil than other pesticides; thus, they are more easily leached into ground water [4]. Bentazon (3-(1-methylethyl)-1H2,1,3-benzothiadiazin-4(3H)-one-2,2-dioxide) is one of the most commonly used herbicides in agriculture and gardening [5]. Various concentrations of bentazon are used by farmers, depending on plant and weed types, but the approximate bentazon concentration in aqueous solution lies in the range of 0.0025–0.0065 (v/v %). It is a selective post-emergence herbicide used to control broad

∗ Corresponding author. Tel.: +98 21 77 240 051; fax: +98 21 77 240 051. E-mail address: [email protected] (T. Mohammadi).

leaf weeds and sedges in beans, rice, corn, peanuts and mint [6]. It has been found that bentazon is one of the most important contaminants in terms of frequency of detection and maximum concentration in groundwater in 23 European countries [7]. The highest concentration of bentazon permitted by the world health organization (WHO) in drinking water is 30 ␮g/L [8], while for the United States Environmental Protection Agency (USEPA) the maximum acceptable bentazon concentration in drinking water is 300 ␮g/L [9]. Several procedures have been used for herbicides removal from water, such as photocatalytic degradation [10,11], combined photo-fenton and biological oxidation [12], aerobic degradation [13], nanofiltration membranes [14], ozonation [15] and adsorption [16]. The biological treatment methods are very slow and not effective enough for the treatment of herbicide wastes. Among others, physical or chemical treatments such as ozonation, nanofiltration and combustion are insufficient due to kinetic reasons since degradation remains partial [17]. Membrane distillation (MD), which is a thermally driven membrane process, can be employed as an ideal alternative to conventional processes. MD is an emerging membrane technology whose action depends on the vapor pressure gradient across the porous hydrophobic membrane. Since only volatile vapor molecules can transport across the membranes due to their hydrophobic nature, the more volatile components (here water)

http://dx.doi.org/10.1016/j.jwpe.2014.11.003 2214-7144/© 2014 Elsevier Ltd. All rights reserved.

Please cite this article in press as: M. Peydayesh, et al., Treatment of bentazon herbicide solutions by vacuum membrane distillation, J. Water Process Eng. (2014), http://dx.doi.org/10.1016/j.jwpe.2014.11.003

G Model

ARTICLE IN PRESS

JWPE-88; No. of Pages 6

M. Peydayesh et al. / Journal of Water Process Engineering xxx (2014) xxx.e1–xxx.e6

xxx.e2 Table 1 Structure and characteristics of bentazon. Common name

Formula

Sodium bentazon

C10 H12 N2 O3 S

Chemical structure

Molecule weight (g/mol)

Boiling point (◦ C)

240.3

395.709

in the hot feed vaporize at the liquid/vapor interface and diffuse across the dry membrane pores. The vapors can then be collected or condensed by different methods [18]. Some of the main features of MD which distinguish this process from conventional distillation process are that the process can operate at lower operating pressure and lower temperature than the boiling temperature of the feed solution, and it requires a smaller vapor–liquid interface which is developed by a hydrophobic membrane in MD as opposed to in conventional distillation which relies on high vapor velocities to establish a large vapor–liquid interface. Some of the crucial applications of MD are the treatment of wastewater in the textile industry [19,20], desalination, concentration of fruit juice and milk in the food industry and separation of alcohol–water mixtures [21]. In the current study, for the first time, MD processes were used for the treatment of herbicide solutions. The effects of several parameters, including feed temperature, feed flow rate, vacuum pressure and initial bentazon feed concentration on flux quality and quantity were studied. Also, a mathematical model describing the variation of bentazon concentration with time was developed and validated with the experimental results.

2. Experimental 2.1. Materials and methods Fig. 1. SEM images of PTFE membrane.

The herbicide bentazon was obtained from Gol Samme Gorgan Company, Iran. Some properties and chemical structures of the herbicide are given in Table 1. The herbicide solutions were prepared by dissolving certain amounts of bentazon in distilled water. For complete mixing, the solutions were mixed by magnetic stirring. Concentrations of the bentazon solutions were determined by UV–vis spectrophotometry (Shimadzu UV-1700) at 333 nm. A PTFE membrane was used in this work. The surface energy of PTFE is 9.1 kN/m so this material is highly hydrophobic. It also has a thermal conductivity as low as 0.22–0.45 W/m K and good chemical stability at the operating temperature of the MD process [22]. Morphology of the membranes was observed using a VEGA scanning electron microscope (TESCAN, USA). The SEM image of the membrane is shown in Fig. 1. The water permeate flux was determined before and after performing tests with the bentazon solutions. The permeate flux was calculated by the following equation:

J=

W S×t

2.2. Experimental system Experiments were carried out using a flat sheet PTFE membrane from Ningbo Changqi Co. (China). A cross-flow membrane module made from steel was used in the experiments (Fig. 2). Effective membrane area in the module was 16.61 cm2 . The membrane properties are reported in Table 2. Schematic representation of the VMD set-up is shown in Fig. 3.

(1)

where J is the permeate flux (kg/m2 h), W is the quantity of permeate (kg), S is the effective membrane area (m2 ) and t is the sampling time (h). Each experiment was repeated twice, in order to assess reproducibility of the results.

Fig. 2. Schematic diagram of membrane module.

Please cite this article in press as: M. Peydayesh, et al., Treatment of bentazon herbicide solutions by vacuum membrane distillation, J. Water Process Eng. (2014), http://dx.doi.org/10.1016/j.jwpe.2014.11.003

G Model

ARTICLE IN PRESS

JWPE-88; No. of Pages 6

M. Peydayesh et al. / Journal of Water Process Engineering xxx (2014) xxx.e1–xxx.e6 Table 2 Properties of the flat sheet PTFE membrane.

xxx.e3

flux. Performing a simple water mass balance over Region 1, as shown in Fig. 4, yields:

Type

CHQISTEX® e-PTFE

Pore size, ␮m Porosity, % Thickness, ␮m Contact angle,◦

0.22 80–95% 80 123 ± 2

dVt = −(Qw ) dt

(2)

where Vt is the solution volume in the feed tank, L, and Qw is the volumetric flow rate of water vapor leaving the membrane module, L/min. In this study, flow rate was used as a parameter because it is more directly related to the capacity of the system and hence it is a more suitable choice than velocity. Moreover, flow rate is easier to measure since a flowmeter can measure it directly. A mass balance on bentazon in the feed tank (Region 2 in Fig. 4) yields: dVt C = C2 Q2 − CQ1 dt

(3)

where C and C2 are the inlet and outlet concentration of bentazon, mg/L, respectively, Q2 and Q1 are the inlet and outlet volumetric flow rates of solution, L/min. The bentazon balance around the mixing zone (Region 3 in Fig. 4) results in the following equation: C2 =

Vt

3. Mathematical modeling Determining the bentazon concentration in the feed solution as a function of time, C(t), is important in order to calculate the water

(4)

Combining Eqs. (2)–(4) and rearranging gives:

Fig. 3. Schematic diagram of VMD set-up.

The feed was continuously fed to the membrane module from the feed tank, sufficiently large to keep the feed concentration nearly constant. The membrane flux was measured by collecting permeate in a condensation trap (liquid nitrogen). The temperature was considered constant within the module since the module was small and it was insulated. As shown in Fig. 3, a pump was used to recirculate feed solution and feed temperature was controlled within the required range using heating element and cooling water coil. The volume of the feed tank was very big compared with the permeation volume. Hence, variation of feed volume during the period of experimentation was negligible.

CQ1 Q1 − Qw

dC = CQw dt

(5)

Upon integration of Eqs. (2) and (5), Vt and C as a function of time can be calculated as: Vt = V0 − Qw t C(t) =

C0 V0 V0 − Qw t

(6) (7)

where V0 is the initial solution volume in the feed reservoir (3.5 L), and C0 is the initial concentration of bentazon in the feed reservoir, mg/L. Eq. (7) can be written in linearized form as: Qw 1 1 − t = C C0 C0 V0

(8)

A plot of 1/C vs. t should give a straight line with an intercept of 1/C0 and a slope of Qw /C0 V0 . The value of Qw can be used to determine the water mass flux Nw , kg/m2 s as follows: Nw =

Qw Af

(9)

where  is the water density and Af is the filtration area in the membrane module (16.61 cm2 ). 4. Results and discussion

Fig. 4. Control volume of the membrane module.

It must be mentioned that all data were recorded at steady state conditions. Before starting each experiment, the set-up was run for 15 min to become steady state in terms of temperature, flow rate and flux. It must be mentioned that the preliminary experiments (analyzing the permeate to determine the bentazon concentration) confirmed that the rejection (R) is 100%. It means that no bentazon passes through the membrane under the experimental conditions. In addition, changes in the absorption spectra of bentazon in the feed solution during the VMD process at different times were measured, as presented in Fig. 5. The increase of the absorption peaks of bentazon at 260 nm and 333 nm indicate that bentazon is being concentrated in the feed tank as time goes on. Also, it should be mentioned that no fouling was observed visually in the whole experiments.

Please cite this article in press as: M. Peydayesh, et al., Treatment of bentazon herbicide solutions by vacuum membrane distillation, J. Water Process Eng. (2014), http://dx.doi.org/10.1016/j.jwpe.2014.11.003

G Model

ARTICLE IN PRESS

JWPE-88; No. of Pages 6

M. Peydayesh et al. / Journal of Water Process Engineering xxx (2014) xxx.e1–xxx.e6

xxx.e4

0.6

(a)

0.034

0.5

0.4

y=-2.5408e-5.x+0.0335

0.032

270 min 0.030

210 min

0.3

1/C

Absorbance

330 min

150 min

0.028

0.2

90 min 0.1

0.026

0 min

0.0 250

0.024

300

350

400

450

0

100

300

Time (min)

Wavelength (nm) Fig. 5. UV–vis spectra changes of bentazon in the feed solution by time at T = 60 ◦ C.

(b) 0.034

110 100

T=40 °C T=50 °C T=60 °C

90

0.032

0.030

80

1/C

Flux (Kg/m2h)

200

70

0.028 60 50

T=40 °C T=50 °C T=60 °C

0.026

Model fit

40

0.024 30

0 5

10

15

20

25

30

35

4.1. Characterization with distilled water The module was initially characterized by measuring the water flux with distilled water as feed. As expected, water flux increases proportionally with the feed flow rate and with temperature (see Fig. 6). Higher flow rates increase heat transfer coefficient, and higher temperatures lead to higher vapor pressures at the feed side, and both phenomena result in increasing water flux [23]. 4.2. Model validation An experiment using a bentazon feed concentration of 30 mg/L, a feed circulation rate of 30 L/h, a feed bulk temperature of 60 ◦ C and a vacuum pressure of 30 mbar was performed in order to validate the mathematical model for assessment of water (vapor) flux. Bentazon concentration in the feed tank was measured at different periods of time. Plotting the obtained experimental data in accordance with Eq. (8) gave a straight line relationship (Fig. 6a). As mentioned previously, −Qw /C0 Q0 and 1/C0 are the slope and the intercept of this line, respectively. A value of 29.85 mg/L can be obtained from Fig. 7(a) for C0 , which is very close to the real initial feed concentration (30 mg/L). The high consistency between the experimental data and the predicted values implies that the

100

150

200

250

300

350

Time (min)

Q (L/h) Fig. 6. Permeate flux of pure water as functions of feed flow rate and temperature, Pv = 30 mbar.

50

Fig. 7. (a) A plot of 1/C vs. time at T = 60 ◦ C, Pv = 30 mbar, and Q = 30 L/h. (b) Effect of temperature on bentazon concentration at Q = 30 L/h; Pv = 30 mbar; C0 = 30 mg/L.

concentration polarization effect, which was not considered in the developed model, is not important in the concentration of bentazon solution via VMD at these experimental conditions [24].

4.3. Effect of feed temperature on water flux Feed temperature plays an important role in determining permeation flux performance in VMD. Bentazon concentration in the feed tank at different times and different temperatures are presented in Fig. 7(b). The slopes of the lines displayed in Fig. 7(b) were used to calculate water flux values, according to Eqs. (8) and (9), and the calculated fluxes are shown in Fig. 8. As can be observed from this figure, flux increases with increasing feed temperature, as expected. Increasing trans-membrane flux with increasing feed temperature in membrane distillation is due to the proportionality between the flux and the vapor pressure gradient across the membrane: J = CP

(10)

where C is a constant depending upon the membrane characteristics, and P is the vapor pressure gradient across the two

Please cite this article in press as: M. Peydayesh, et al., Treatment of bentazon herbicide solutions by vacuum membrane distillation, J. Water Process Eng. (2014), http://dx.doi.org/10.1016/j.jwpe.2014.11.003

G Model

ARTICLE IN PRESS

JWPE-88; No. of Pages 6

M. Peydayesh et al. / Journal of Water Process Engineering xxx (2014) xxx.e1–xxx.e6

100

xxx.e5

70

95

Experimental Model

65

Flux (Kg/m2 h)

Flux (Kg/m2 h)

90 85 80 75

60

55

50

70 45

65 60

40 35

40

45

50

55

60

65

5

10

15

20

T (°C) Fig. 8. Effect of feed temperature on water flux at Q = 30 L/h; Pv = 30 mbar; C0 = 30 mg/L.



35

78

(11)

where A, B and C are Antoine’s constant (8.07131, 1730.63 and 233.426 for water, respectively) and T and P are the related temperature (◦C) and pressure (mm Hg), respectively. By increasing feed temperature, the vapor pressure gradient across the membrane increases exponentially and, consequently, a proportional increase in trans-membrane flux can be observed [25]. Besides, feed viscosity decreases with increasing feed temperature, which is favorable to enhance the mass transfer coefficient [26–28]. The results also indicate that the predicted values of water flux using the developed model (Eq. (9)) closely agree with the measured values.

76

Flux (Kg/m2 h)

B P = exp A − T −C

30

Fig. 9. Effect of feed flow rate on water flux at T = 40 ◦ C; Pv = 30 mbar; C0 = 30 mg/L.

membrane sides. The vapor pressure is related to temperature by Antoine’s equation:



25

Q (L/h)

5

10

15

20

25

30

35

C (mg/L) Fig. 10. Effect of feed concentration on water flux at T = 40 ◦ C; Pv = 30 mbar; Q = 30 L/h.

70

60

2

The effect of bentazon feed concentration on permeation flux is presented in Fig. 10. As observed, at a constant feed temperature of 40 ◦ C, by increasing bentazon concentration from 10 to 30 mg/L, the distillate water flux decreases from 76.65 to 67.02 kg/m2 h. Thus an average of 12% flux decline is observed when bentazon concentration increases from 10 to 30 mg/L. This is due to the fact that water vapor pressure is the driving force of the MD process and is related to water activity. Therefore, by increasing feed concentration the water activity decreases and this decreases water flux due to decreasing the driving force. The concentration boundary layer is formed adjacent to the membrane surface due to the presence of bentazon in the feed. This concentration polarization

70

66

Flux (Kg/m h)

4.5. Effect of bentazon concentration on water flux

72

68

4.4. Effect of feed flow rate on water flux Fig. 8 shows the effect of feed flow rate on permeation flux. The results show that water flux increases with increasing of feed velocity. This may be related to the concentration and temperature polarization effects. Higher flow rate promotes more turbulence and eddies in the feed boundary layers next to the membrane surface leading to enhancement of heat transport from the bulk feed to the membrane surface, and results in higher water flux [29]. Moreover, reduction of concentration polarization with increasing feed velocity also enhances water flux, although as mentioned earlier the effect of temperature polarization is believed to be more significant than that of concentration polarization on water flux (Fig. 9) [27].

74

50

40

30

20 20

30

40

50

60

70

80

90

100

Pv (mbar) Fig. 11. Effect of vacuum pressure the water flux at T = 40 ◦ C; Q = 30 L/h; C0 = 30 mg/L. Pv = 30 mbar; Q = 30 L/h; C0 = 30 mg/L.

Please cite this article in press as: M. Peydayesh, et al., Treatment of bentazon herbicide solutions by vacuum membrane distillation, J. Water Process Eng. (2014), http://dx.doi.org/10.1016/j.jwpe.2014.11.003

G Model

ARTICLE IN PRESS

JWPE-88; No. of Pages 6 xxx.e6

M. Peydayesh et al. / Journal of Water Process Engineering xxx (2014) xxx.e1–xxx.e6

further reduces the vapor pressure of water at the feed-membrane interface, thereby reduces the driving force for evaporation [29]. 4.6. Effect of vacuum pressure on water flux Fig. 11 illustrates the effect of vacuum pressure on permeation flux. As can be observed, reduction of the downstream pressure increases permeate flux through the membrane. This is due to the fact that the driving force in MD process in general and in VMD in particular is the vapor pressure difference across both sides of the membrane pores. When a heated aqueous feed solution is brought into contact with one side of the membrane, the hydrophobic nature of the membrane prevents penetration of the liquid aqueous solution into the pores, resulting in the formation of a vapor–liquid interface at each pore entrance. The presence of a reasonably high vacuum on the permeate side of the membrane in VMD drastically reduces the amount of conductive heat loss from the aqueous solution [30]. Therefore, working at lower downstream pressure results in higher water flux [31,32]. 5. Conclusions An experimental study of the VMD process to treat bentazon solutions was carried out. The effects of the following parameters on water flux and rejection were studied: feed temperature, vacuum pressure, feed flow rate and bentazon feed concentration. For all the experiments, a commercial PTFE membrane with a pore size of 0.22 ␮m was employed. In all the investigated experiments, bentazon was not detected in the permeate. The results showed that by increasing feed temperature and feed flow rate and decreasing bentazon feed concentration and vacuum pressure, water flux through the membrane increases. The highest water flux of 92.94 kg/h m2 was obtained at 60 ◦ C. The results have shown that the developed mathematical model predictions agree well with the experimental data. References [1] J.M. Salman, V.O. Njoku, B.H. Hameed, Adsorption of pesticides from aqueous solution onto banana stalk activated carbon, Chem. Eng. J. 174 (2011) 41–48. ´ [2] A. Navalón, A. Prieto, L. Araujo, J. Luis Vılchez, Determination of oxadiazon residues by headspace solid-phase microextraction and gas chromatography–mass spectrometry, J. Chromatogr., A 946 (2002) 239–245. [3] R. Pourata, A.R. Khataee, S. Aber, N. Daneshvar, Removal of the herbicide bentazon from contaminated water in the presence of synthesized nanocrystalline TiO2 powders under irradiation of UV-C light, Desalination 249 (2009) 301–307. [4] Z. Liu, X. Yan, M. Drikas, D. Zhou, D. Wang, M. Yang, J. Qu, Removal of bentazone from micro-polluted water using MIEX resin: kinetics, equilibrium, and mechanism, J. Environ. Sci. 23 (2011) 381–387. [5] J.M. Salman, B.H. Hameed, Effect of preparation conditions of oil palm fronds activated carbon on adsorption of bentazon from aqueous solutions, J. Hazard. Mater. 175 (2010) 133–137. [6] E. Manuela Garrido, J.L. Costa Lima, C.M. Delerue-Matos, A. Maria Oliveira Brett, Electrochemical oxidation of bentazon at a glassy carbon electrode: application to the determination of a commercial herbicide, Talanta 46 (1998) 1131– 1135. ˜ ˜ [7] A.I. Canero, D. Becerra, J. Cornejo, M.C. Hermosín, Á. Albarrán, A. López-Pineiro, L. Cox, Transformation of organic wastes in soil: effect on bentazone behaviour, Sci. Total Environ. 433 (2012) 198–205.

[8] J.M. Salman, V.O. Njoku, B.H. Hameed, Bentazon and carbofuran adsorption onto date seed activated carbon: kinetics and equilibrium, Chem. Eng. J. 173 (2011) 361–368. [9] A. Omri, A. Wali, M. Benzina, Adsorption of bentazon on activated carbon prepared from Lawsonia inermis wood: equilibrium, kinetic and thermodynamic studies, Arabian J. Chem. (2012). [10] M. U˘gurlu, M.H. Karao˘glu, TiO2 supported on sepiolite: preparation, structural and thermal characterization and catalytic behaviour in photocatalytic treatment of phenol and lignin from olive mill wastewater, Chem. Eng. J. 166 (2011) 859–867. [11] J. Gong, C. Yang, W. Pu, J. Zhang, Liquid phase deposition of tungsten doped TiO2 films for visible light photoelectrocatalytic degradation of dodecylbenzenesulfonate, Chem. Eng. J. 167 (2011) 190–197. [12] H. Katsumata, T. Kobayashi, S. Kaneco, T. Suzuki, K. Ohta, Degradation of linuron by ultrasound combined with photo-Fenton treatment, Chem. Eng. J. 166 (2011) 468–473. [13] H.M.R. Murthy, H.K. Manonmani, Aerobic degradation of technical hexachlorocyclohexane by a defined microbial consortium, J. Hazard. Mater. 149 (2007) 18–25. [14] A.L. Ahmad, L.S. Tan, S.R.A. Shukor, Dimethoate and atrazine retention from aqueous solution by nanofiltration membranes, J. Hazard. Mater. 151 (2008) 71–77. [15] M.I. Maldonado, S. Malato, L.A. Pérez-Estrada, W. Gernjak, I. Oller, X. Doménech, J. Peral, Partial degradation of five pesticides and an industrial pollutant by ozonation in a pilot-plant scale reactor, J. Hazard. Mater. 138 (2006) 363–369. [16] A.a.H. Al-Muhtaseb, K.A. Ibrahim, A.B. Albadarin, O. Ali-khashman, G.M. Walker, M.N.M. Ahmad, Remediation of phenol-contaminated water by adsorption using poly(methyl methacrylate) (PMMA), Chem. Eng. J. 168 (2011) 691–699. [17] A.K. Abdessalem, N. Bellakhal, N. Oturan, M. Dachraoui, M.A. Oturan, Treatment of a mixture of three pesticides by photo- and electro-Fenton processes, Desalination 250 (2010) 450–455. [18] M. Khayet, K.C. Khulbe, T. Matsuura, Characterization of membranes for membrane distillation by atomic force microscopy and estimation of their water vapor transfer coefficients in vacuum membrane distillation process, J. Membr. Sci. 238 (2004) 199–211. [19] N.M. Mokhtar, W.J. Lau, A.F. Ismail, The potential of membrane distillation in recovering water from hot dyeing solution, J. Water Process Eng. 2 (2014) 71–78. [20] N.M. Mokhtar, W.J. Lau, B.C. Ng, A.F. Ismail, D. Veerasamy, Preparation and characterization of PVDF membranes incorporated with different additives for dyeing solution treatment using membrane distillation, Desalin. Water Treat. (2014) 1–14. [21] L. Mariah, C.A. Buckley, C.J. Brouckaert, E. Curcio, E. Drioli, D. Jaganyi, D. Ramjugernath, Membrane distillation of concentrated brines – role of water activities in the evaluation of driving force, J. Membr. Sci. 280 (2006) 937–947. [22] J. Zhang, N. Dow, M. Duke, E. Ostarcevic, J.-D. Li, S. Gray, Identification of material and physical features of membrane distillation membranes for high performance desalination, J. Membr. Sci. 349 (2010) 295–303. [23] A. Criscuoli, J. Zhong, A. Figoli, M.C. Carnevale, R. Huang, E. Drioli, Treatment of dye solutions by vacuum membrane distillation, Water Res. 42 (2008) 5031–5037. [24] F. Banat, S. Al-Asheh, M. Qtaishat, Treatment of waters colored with methylene blue dye by vacuum membrane distillation, Desalination 174 (2005) 87–96. [25] T.Y. Cath, V.D. Adams, A.E. Childress, Experimental study of desalination using direct contact membrane distillation: a new approach to flux enhancement, J. Membr. Sci. 228 (2004) 5–16. [26] M.N.A. Hawlader, R. Bahar, K.C. Ng, L.J.W. Stanley, Transport analysis of an air gap membrane distillation (AGMD) process, Desalin. Water Treat. 42 (2012) 333–346. [27] E.K. Summers, J.H.V. Lienhard, A novel solar-driven air gap membrane distillation system, Desalin. Water Treat. (2012) 1–8. [28] S. Tone, M. Demiya, K. Shinohara, T. Otake, Permeation of aromatic compounds in aqueous solutions through thin, dense cellulose acetate membranes, J. Membr. Sci. 17 (1984) 275–288. [29] A.K. Manna, M. Sen, A.R. Martin, P. Pal, Removal of arsenic from contaminated groundwater by solar-driven membrane distillation, Environ. Pollut. 158 (2010) 805–811. [30] B. Li, K.K. Sirkar, Novel membrane and device for vacuum membrane distillation-based desalination process, J. Membr. Sci. 257 (2005) 60–75. [31] K.W. Lawson, D.R. Lloyd, Review: membrane distillation, J. Membr. Sci. 124 (1997) 1. [32] M.S. El-Bourawi, R.M.Z. Ding, M. Khayet, A framework for better understanding the membrane distillation separation process, J. Membr. Sci. 285 (2006) 4.

Please cite this article in press as: M. Peydayesh, et al., Treatment of bentazon herbicide solutions by vacuum membrane distillation, J. Water Process Eng. (2014), http://dx.doi.org/10.1016/j.jwpe.2014.11.003