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Nanofiltration for the removal of norfloxacin from pharmaceutical effluent
Accepted Manuscript Title: Nanofiltration for the Removal of Norfloxacin from Pharmaceutical Effluent Authors: Dalva Inˆes de Souza, Eugˆenio Minetto Dottein, Alexandre Giacobbo, Marco Antˆonio Siqueira Rodrigues, Maria Norberta de Pinho, Andr´ea Moura Bernardes PII: DOI: Reference:
S2213-3437(18)30567-0 https://doi.org/10.1016/j.jece.2018.09.034 JECE 2655
To appear in: Received date: Revised date: Accepted date:
30-7-2018 17-9-2018 18-9-2018
Please cite this article as: de Souza DI, Dottein EM, Giacobbo A, Siqueira Rodrigues MA, de Pinho MN, Bernardes AM, Nanofiltration for the Removal of Norfloxacin from Pharmaceutical Effluent, Journal of Environmental Chemical Engineering (2018), https://doi.org/10.1016/j.jece.2018.09.034 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.
Nanofiltration for the Removal of Norfloxacin from Pharmaceutical Effluent
Dalva Inês de Souza 1, Eugênio Minetto Dottein 1, Alexandre Giacobbo 1, Marco Antônio Siqueira Rodrigues 2, Maria Norberta de Pinho 3, Andréa Moura Bernardes 1, * Programa de Pós-Graduação em Engenharia de Minas, Metalúrgica e de Materiais – PPGE3M, Universidade Federal do Rio Grande do Sul – UFRGS. Av. Bento Gonçalves, n. 9500, Porto Alegre/RS, Brazil. Tel: +555133089428 - Fax: +555133089427
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1
Instituto de Ciências Exatas e Tecnológicas – ICET, Universidade Feevale, Rodovia 239, n. 2755 – Vila Nova, Novo Hamburgo/RS, Brazil. Tel: +555135868800 2
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3
Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, n. 1, 1049-001, Lisbon, Portugal.
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*corresponding author: e-mail: [email protected]
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Abstract Conventional treatment processes have presented low efficiency in removing antibiotics from
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water and effluents, wherefore the development of processes and technologies to comply with this
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matter is highly important. Membrane separation processes may be applied in the obtainment of high-quality reuse water, fully or partly removing the pharmaceuticals. Thus, this paper aims to
effluent
simulating
a
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assess the performance of two nanofiltration membranes in removing norfloxacin from a synthetic pharmaceutical
wastewater.
Different
solution
concentrations,
transmembrane pressures and pH were evaluated. Both membranes presented high selectivity to
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norfloxacin, such that thfe rejection of this antibiotic remained between 87 and 99.5%. The pH had an effect on membranes' selectivity and permeability. The highest norfloxacin rejection and
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the lowest permeability were reached at pH 6.5, which may be related to electrostatic interactions between membrane surface and norfloxacin ionic species. Considering the elevated rejections obtained in this study (87–99.5%), the viability of nanofiltration stands out in removing
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norfloxacin from effluents.
Keywords: Nanofiltration; Norfloxacin; Antibiotic Removal; Pharmaceutical Effluent.
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1. Introduction The detection of contaminants of emerging concern in water bodies has increased in recent years, what is troubling, considering the levels in which they are found in the aquatic environment and the meaningful risks due to their potential toxicological effects [1]. In this sense, special attention has been given to the antibiotics, a class of contaminants of emerging concern, since they are responsible for causing bacterial resistance. The main sources, responsible for the contamination
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with these organic pollutants, are municipal wastewater and effluents from hospitals and the pharmaceutical industry, which, in general, are discharged without the appropriated treatment [2].
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In general, antibiotics are synthetic compounds that are not easily biodegradable. Among the antibiotics, norfloxacin (NOR) is one of the most consumed in Latin America [3], and consequently, it is one of the main antibiotics found in water bodies. NOR is a fluoroquinolone,
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and presents stability, structural complexity and antimicrobial activity, disturbing the conventional water and wastewater treatment processes [4-6]. Considering this approach, there is the need for
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investigation of other technologies for wastewater treatment. In this sense, taking into account
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their inherent characteristics, membranes technology may be used for the removal or concentration
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of antibiotics present in water and wastewater [7-9].
Bellona et al. [10] have conducted a research involving the operational and rejection performances
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of several nanofiltration membranes, such as NF 270, compared to a commonly employed reverse osmosis (ESPA2) membrane, at a water reclamation facility, in the removal of some nonionic,
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positive and negative pharmaceuticals, such as carbamazepine, sulfamethoxazole and atenolol, respectively. NF 270 membrane operated at specific double flux comparing to the flux of the
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ESPA2 membrane. NF 270 showed minimal flux declining and elevated water recovery (87–88%). It resulted in approximately 65% rejection of conductivity and approximately 83% rejection of total organic carbon (TOC). The rejections of atenolol, carbamazepine and sulfamethoxazole were 78.9 %, 88.0% and 98.0%, respectively. An economic analysis using data from pilot-scale testing
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and full-scale operation revealed significant cost savings using a low-pressure NF, such as the NF 270 membrane. Yangali-Quintanilla et al. [11] carried out a study with an aqueous cocktail of pharmaceuticals (neutral and ionic compounds), such as acetaminophen, carbamazepine, sulfamethoxazole, naproxen and others, using nanofiltration membranes (NF 90 and NF 200) and reverse osmosis membranes (BW30 LE and ESPA2). Tests were accomplished in bench, pilot and full scales to 2
obtain water reuse and concluded that tight nanofiltration polyamide membranes are an alternative to reverse osmosis (RO) [11], meaning that tight nanofiltration polyamide membranes, such as the NF 90, may be an effective barrier against pharmaceuticals, pesticides, endocrine disruptors and other organic contaminants. Some antibiotics, including norfloxacin, with high detection frequencies in effluents from Wastewater Treatment Plants (WWTP) in Dalian (China), were used in nanofiltration combined
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with ozone-based advanced oxidation processes. This research used a commercial NF membrane, NFX (Synder Filtration, Vacaville, CA, USA), similar to the NF 90 membrane. NFX has a
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polyamide layer skin and its molecular weight cut-off (MWCO) is in the range of 150 – 300 Da, NF 90 MWCO is approximately 200 Da. The rejections (>98 %) were high to all studied antibiotics. The study concluded that nanofiltration could remove antibiotics from the effluent, and UV/O3 process was able to further eliminate the antibiotics from the NF concentrate effectively
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[12].
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In the light of these considerations, the present study was conducted to assess the performance on
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productivity (permeation flux) and selectivity (evaluated with the rejection coefficient) of two
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nanofiltration membranes, NF 90 and NF 270, in removing norfloxacin from a pharmaceutical effluent. The effects of pH, concentration and operation pressure on rejection and permeation flux
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were assessed. In addition, the interactions solute/membranes in several conditions were
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investigated.
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2. Material and Methods 2.1 Feed Solutions
To simulate wastewater from the pharmaceutical industry and assess the mechanisms involved in
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nanofiltration, synthetic aqueous solutions with pure (99.9%) norfloxacin (NOR), obtained in a veterinarian clinic, were used. Table 1 shows data of the pharmaceutical used. Permeation and rejection experiments were carried out with NOR aqueous solutions, at a concentration range (5, 25 and 50 mg.L–1) found in pharmaceutical wastewater [13]. The influence of pH upon the rejection mechanisms was verified for 50 mg.L–1 NOR solutions at pH 6.5 (natural
3
pH), pH 2.4 (acidified with 1 M HCl) and pH 9.8 (adjusted with 1 M NaOH). All feed solutions were made with distilled/deionized water (conductivity ≤ 2 µS.cm–1).
Physicochemical characteristics
Norfloxacin
Molecular formulaa
C16H18FN3O3
Molecular weighta
319.331 Da
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pKab
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Table 1. Physicochemical characteristics of the pharmaceutical used (norfloxacin).
6.34; 8.57
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Structural formula a
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Stokes radius (nm)c
5.22
M
Diffusion coefficient (10–10.m2.s–1)c
0.47
From Kim et al. [14];
b
From Homayoonfal and Mehrnia [7];
c
Estimated from Stokes–Einstein equation using Wilke–Chang diffusion coefficient [15];
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a
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2.2 Membranes Characterization The permeation experiments were performed with two flat-sheet nanofiltration membranes, NF 270 and NF 90 (Filmtec – Minneapolis, MN). Concerning the filtration range, membranes have
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MWCO of approximately 200 Da for NF 90, considered a narrow band, and around 400 Da for NF 270, considered a broad brand [16]. The pore radius of the membranes were determined by Nghiem et al. [17] through permeation experiments with reference solutes: dextrose, xylose, erythritol, dioxane. According to the authors [17], the pore radii for the membranes NF 90 and NF 270 are 0.34 nm and 0.42 nm, respectively. These membranes have a thin film (skin) of
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polyamide over a layer of polysulfone on a polyester support layer. The skin is a mixture of aromatic and aliphatic polyamide with amine and carboxylates end groups [16]. The surface layer of polyamide membranes contains amine groups, H+ receptors, and carboxylic groups, H+ donors, which give it an amphoteric characteristic. The isoelectric point (IEP) is around 3.5 for NF 270 and 4.0 for NF 90 [18]. At pH lower than the IEP, membrane surface becomes cationic due to protonation of the amine group (NH3+). At pH higher than the IEP, membrane
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surface becomes anionic due to deprotonation of the carboxyl group (COO–). At the IEP, there is a balance of charges between the cationic and anionic sites of the polymer on the membrane
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surface, which remains neutral, a zwitterion (Z).
First, each membrane was compacted through recirculation of distilled and deionized water (conductivity ≤ 2 µS.cm–1) with the pressure of 25 bar for 3 hours. The purpose of this procedure
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was to prevent possible changes in the membranes’ structure with subsequent working pressures. Membranes were characterized in terms of their hydraulic permeability (Lpw), as described by
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Giacobbo et al. [19], at transmembrane pressures (ΔP) of 5, 7, 10, 15 bar, and regarding salts
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rejection (sodium chloride, calcium chloride and sodium sulfate) at 10 bar, using electrolyte
𝐶𝑓 −𝐶𝑝 𝐶𝑓
⌋ 100
Eq. (1)
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R (%) = ⌊
M
solutions at 2000 mg.L–1 concentration. The rejection coefficient (R) was defined as:
Where Cf is the average between final and initial feed solution concentration and Cp is the
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concentration of permeate. In all experiments, the temperature was 25 ± 1 °C, and feed flow rate was 3.3 L.min–1. This feed flow rate was chosen based on previous studies at the same cell [20]
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and corresponds to a tangential velocity of 0.96 m.s–1 and a Reynolds number close to 23,000. The choice was done in order to minimize the concentration polarization incidence. The setting time of every experiment was 30 minutes. Between the experiments, membrane washing was always carried out using distilled/deionized water and 0.1% NaOH solution with cycles of 30 minutes at
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30 °C and 25 °C until Lpw reached at least 90% of the initial Lpw obtained after compaction.
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2.3. Nanofiltration Permeation Experiments The permeation experiments were carried out with two flat cells of membrane surface area of 14.5 x 10–4 m2 each, and with feed flow rate of 3.3 L.min–1 in a lab-bench unit thoroughly described by Giacobbo et al. [21], shown in Figure 1. Experiments were performed in total recirculation mode, where the permeate and the retentate
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streams were recirculated to the feed tank to keep feed concentration constant. Thus, at steady state, the variation of the permeation flux (Jp) and of the solute rejection coefficients with ΔP were
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evaluated.
Experiments ran at 25 ± 1 °C, being the temperature regulated by an ultra-thermostatic bath (Nova Ética) attached to the feed tank. The stabilization time for each ΔP was 30 min. Permeate and feed samples of each ΔP were taken for analysis. All experiments of this research were conducted at
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ED
M
A
N
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least twice.
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Figure 1. Set up of the filtration unit. 1-Feed tank, 2-Heat exchanger, 3-Two-way valve, 4-Pump, 5-By-pass valve, 6-Manometers, 7-Membrane, 8-Permeation cell, 9-Permeate sample, 10Pressure-regulation valve, 11-Rotameter. Adapted from Giacobbo et al. [21]. Due to the possibility of hydrolysis occurrence in aqueous solution with the solution aging, all NOR solutions were prepared on the time of the experiment. Each membrane filtration experiment
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took a maximum of 4 hours, and each sample collected during the experiment, at each ΔP, was
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immediately taken to analysis.
2.4 Transport of Solute and Rejection by Membrane
The transport of the solute through the hydrodynamic model assumes NF membranes to have
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pores. For study purposes, the pores are considered cylindrical and with uniform radius. The ratio
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between solute radius (rs) and membrane pore radius (rp), defined as λ (= rs/rp), is an important
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factor to predict the solute rejection. In general, the solute Stokes radius is used to evaluate steric hindrance assuming rigid molecules with spherical shape. It can be calculated by Stokes-Einstein
M
equation [22]. The λ is used to estimate a distribution coefficient ɸ (=1–rs/rp)2. This coefficient is equal to the equilibrium partition at the entrance and exit on the membrane pore. When λ is larger
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than 1.0, it is predicted that rejection will be 100%, just governed by steric relationship and
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equilibrium partitioning behavior [23].
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2.5. Analytical Methods
Conductivity and pH were measured using an AKSO 8306 conductivity meter and a Tek PHS-3B pH meter, respectively. A Thermo Scientific HPLC system equipped with a Supelco Drug
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Discovery C-18 column (with diameter, length and pore size of 4.6 mm, 100 mm and 3 µm, respectively) and an UV–vis detector was used to measure the antibiotic concentrations in the feed and permeate. The detection wavelength was set at 277 nm. The mobile phase used for isocratic elution was methanol and acetic acid 5% v/v (40:60) which was delivered at 0.75 mL.min–1 through the column. A sample injection volume of 20 µL was used. The oven temperature was 30 °C. A calibration yielded standard curve, with coefficient of determination (R2) greater than
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0.999 within the range of experimental concentrations, was used (Figure S1). The analyzes were carried out immediately on the conclusion of each experiment.
3. Results and Discussion
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3.1. Membrane Characterization Regarding average water permeability (Lpw), the NF 270 and NF 90 membranes presented 17.38 and 6.86 kg.h–1.m–2.bar–1, respectively. In terms of rejection coefficient (R) to the referring salts,
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NF 270 membrane reached 52%, 71% and 98% for sodium chloride, calcium chloride and sodium sulfate, while NF 90 presented 90%, 97% and 99%, respectively. These results are in accordance
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with the ones reported in the other works [24-29].
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3.2. Effects of pH and ΔP on Permeation Flux and Rejection
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In Figure 2 are shown the permeation fluxes of 50 mg.L–1 NOR solutions at different values of pH
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and ΔP, while in Table 2 are displayed the solutions permeabilities (Lps) and the rejection to norfloxacin as a function of solution pH. As ΔP increases, the permeation flux of all solutions
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increases, as expected. In addition, it was also expected an increase in permeation flux by increasing the solution pH. According to Simon et al. [30], when pH solution changes, the pore size and the surface hydrophilicity of the polyamide NF membranes may change. The authors [30]
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stated that caustic cleaning led to a small increase in pore size and surface hydrophilicity of the NF 270 membrane, resulting in a notable increase in the permeability and salt passage. By contrast,
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the impact on the NF 90 membrane was negligible [30]. At this work, for the NF 270 membrane, taking into account the standard deviation of all experimental run repetitions, no significant difference was observed between the permeabilities to
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the pure water and to the NOR solutions with pH 2.4 and 9.8. On the other hand, for the NF 90 membrane, only the permeability to the NOR solution with pH 9.8 closed to the one achieved with pure water. Besides, for both membranes, the Lps mean values achieved with the NOR solution at pH 6.5 were always the lowest ones. In addition, at pH 6.5 were obtained the highest NOR rejections. This behavior was mainly expected with the most acid solution (pH 2.4). It occurs that, at pH 6.5, membranes present anionic surface charge, once the pH of the solution is higher than 8
the IEP of the membranes. NOR also presents amine and carboxyl groups and has two pKa values, pKa1 = 5.58 and pKa2 = 8.68. 300 NF 270
250
Lpw = 17.38 kg.h-1.m-2.bar-1
200
pH 2.4
150
pH 6.5
100
pH 9.8
Lps pH 2.4 = 14.57 kg.h-1.m-2.bar-1
50
Lps pH 6.5 = 11.57 kg.h-1.m-2.bar-1 Lps pH 9.8 = 15.22 kg.h-1.m-2.bar-1
0 0
5
10
15
20
N
200
150
M
Lpw = 8.72 kg.h-1.m-2.bar-1
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NF 90
Pure water pH 2.4
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100
50
pH 6.5
Lps pH 2.4 = 6.97 kg.h-1.m-2.bar-1
pH 9.8
Lps pH 6.5 = 6.66 kg.h-1.m-2.bar-1
0
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0
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Permeation flux (kg.h–1.m–2)
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Pressure (bar) b)
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Pure water
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Permeation flux (kg.h–1.m–2)
a)
5
Lps pH 9.8 = 8.38 kg.h-1.m-2.bar-1
10
15
20
Pressure (bar)
Figure 2. Permeation fluxes of 50 mg.L–1 NOR solution as a function of ΔP and solution pH. Operating conditions: feed flow rate of 3.3 L.min–1 and temperature of 25 °C. (a) NF 270
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membrane and (b) NF 90 membrane.
Table 2. Rejection and permeability results of 50 mg. L–1 NOR aqueous solution at different pH values. Operating conditions: ΔP = 5–12 bar; T = 25 °C; feed flow rate = 3.3 L.min–1. NF 270
NF 90
9
Solution pH
R (%)
2.4
Lps
Lps
(kg.h .m .bar )
Lpw-Lps (%)
R (%)
(kg.h .m .bar )
Lpw-Lps (%)
89.2 ± 2.92
14.57
16.2
98.3 ± 0.47
6.97
20.1
6.5
93.6 ± 1.47
11.57
33.4
99.5 ± 0.08
6.66
23.6
9.8
87.0 ± 0.87
15.22
12.4
98.0 ± 0.28
8.34
3.90
–1
–2
–1
–1
–2
–1
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Figure 3 presents the distribution of norfloxacin species in aqueous solution as a function of pH. Below the pKa1 NOR is mainly positive, above pKa2 it is predominantly negative and at the pKa, it is zwitterion (± neutral species), i.e., between pH 5.58 and 8.68, it is mainly presented in the
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neutral form.
At pH 6.5, the membranes are anionic and NOR speciation presents around 10.6% in the cationic form, around 88.7% in the neutral form (zwitterion) and 0.6% is NOR anionic (Figure 3). Thus, a
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strong attraction between the cationic solute and the negatively charged functional groups from
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the membrane surface may occur. This electrostatic attraction effect can generates concentration polarization and fouling, explaining the lowest solution permeability, when compared to the water pKa1
pKa2
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permeability (representing a reduction of 33.4 and 23.6% for NF 90 and NF 270, respectively) and
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to the other pH solutions. A higher rejection (99.6 and 93.6% for NF 90 and NF 270, respectively)
100 80
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Distribution of NOR species (%)
a)
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was also a consequence, as shown in Table 2.
60
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40 20 0
0
1
2
4
5
6
8
9
10
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Neutral specie (±)
Cationic specie 2+
O
O
O
0H-
0H
F
+
+
+
H3C
NOR cationic form
13
14
O
O
0H-
-
F O
OH
N H
12
Cationic specie 1+
F
N
11
Anionic specie (1-)
OH
H2N
7
pH
O
O
b) (a)
3
N
N
H
H 2N
H
+
pka = 5.58
+
H3C
NOR cationic form
N
N H2N
H3C
NOR neutral form
F
-
O H
-
+
pKa = 8.68
+
O
N
N HN H3C
NOR anionic form
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Figure 3. a) Distribution of norfloxacin species in aqueous solution as a function of pH, prediction calculated data from Chemicalize software [31], b) NOR species as a function of pH and pKa, Z=
3.3 Concentration and ΔP Effects on Permeation Flux and Rejection
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zwitterion, adapted from Barbosa et al. [32].
In Figure 4 are shown the permeation fluxes of NOR solutions at pH 6.5 with different solute
300 250
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NF 270
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Lpw = 17.38 kg.h-1.m-2.bar-1
M
200 150
Pure water 5 mg.L-1 25 mg.L-1
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100
Lps 5 = 13.53 kg.h-1.m-2.bar-1
50 mg.L-1
Lps 25 = 12.29 kg.h-1.m-2.bar-1
50
Lps 50 = 11.57 kg.h-1.m-2.bar-1
0
5
10
15
20
Pressure (bar)
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0
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Permeation flux (kg.h–1.m–2)
a)
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rejection to norfloxacin as a function of solute concentration.
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concentrations and ΔP, while in Table 3 are displayed the solutions permeabilities (Lps) and the
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b)
180
Permeation flux (kg.h–1.m–2)
150
NF 90 Lpw = 8.72 kg.h-1.m-2.bar-1
120 Pure water
90
5 mg.L-1
50 mg.L-1
Lps 5 = 7.54 kg.h-1.m-2.bar-1
30
Lps 25 = 7.18 kg.h-1.m-2.bar-1 Lps 50 = 6.66 kg.h-1.m-2.bar-1
0 5
10
15
20
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0
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25 mg.L-1
60
Pressure (bar)
Figure 4. Permeation fluxes as a function of ΔP and feed solution concentration. Operating
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conditions: feed flow rate of 3.3 L.min–1, temperature of 25 °C, and solution pH of 6.5. a)
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NF 270 membrane, b) NF 90 membrane.
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Regarding the different concentrations of NOR, the results show that, in general, the higher the
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concentration, the lower the permeation flux and the higher the rejection for both studied membranes (NF 270 and NF 90). The increase in the solute concentration necessarily leads to an
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increase in the osmotic pressure, reducing the effective transmembrane pressure and, consequently, the permeation flux. In addition, an increase in the solute concentration at the boundary layer adjacent to the membrane surface (in the retentate side) acts as an additional
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resistance to the solute passage, increasing the NOR rejection.
Table 3. Effects of NOR solution concentration on permeability and rejection. Operating conditions: ΔP = 5–12 bar; T = 25 °C; feed flow rate = 3.3 L.min–1; pH solution = 6.5.
NOR concentration (mg.L–1)
NF 270
NF 90 R
Lps
R
(kg.h–1.m–2.bar–1)
(%)
(kg.h–1.m–2.bar–1)
(%)
5
13.53
91.29 ± 3.21
7.54
98.85 ± 0.20
25
13.13
97.45 ± 0.39
7.18
98.86 ± 0.39
50
11.57
93.62 ± 1.48
6.66
99.45 ± 0.08
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Lps
12
As previously reported, at pH 6.5, the surface of both membranes is negatively charged, and, although at this pH the NOR is mostly neutral, the solution still presents about 10% of cationic species that may result in attraction between anionic sites from the membrane and cationic species of solute. When the concentration increases even more, it increases the density of species of solute near the membrane, hindering the mass transfer through it. Thereby, there is a tendency in increasing the rejection and diminishing the flux. For both membranes, the rejection increases and
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flux decreases probably due concentration polarization and reversible fouling, especially on NF 270 (the broader membrane). However, with the highest NOR concentration (50 mg.L–1), the NF 270 presented a lower rejection than the one achieved with 25 mg.L–1 solution. This behavior
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can be attributed to the fact that, in this case, the higher concentration polarization incidence (increase solute concentration near the membrane surface) facilitates the passage of NOR into the permeate, reducing the rejection coefficient.
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Regarding the NF 90 membrane, the results indicate that there is a prevalence of the stereo
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chemical exclusion as a function of pore size (sieve effect) or molecular exclusion as a function of the MWCO of the membrane (MWsolute > MWCONF90). NF 90 is a narrow-band membrane, and
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according to Bellona et al. [33], NF narrow-band membranes (MWCO ≤ 200 Da or Na+ > 90%
M
rejection) restrict the transport of solute across the membrane similarly to reverse osmosis
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membranes, that is, by limiting stereo chemical diffusion and exclusion. According to the literature data, the rp values for NF 90 and NF 270 are 0.34 nm and 0.42 nm, respectively, while the norfloxacin radius is 0.47 nm. The ratio between the radius of the neutral
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solute and the membrane pore radius (λ= rs/rp) is greater than 1.0 for both membranes, as shown in Table 4. When λ is greater than 1.0, the rejection should be 100%. On the contrary, at the present
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work, the NOR rejection ranged from 87% to 95.5% indicating that the rejection was membranedependent and affected by pH and electrostatic interactions and not just governed by steric relationship and equilibrium partitioning behavior. In fact, it is also important to consider that, although the stokes radius of Norfloxacin is slightly higher than pore radius, the membrane pore
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radius is a mean value, which mean that the membrane may exhibit pores larger than 0.47 nm if the average is 0.42 nm, which will also allow the transport through the membrane.
Table 4. Data related to NOR radius and membrane pores radius.
13
Solute radius – rs (nm)
NF 270
NF 90
pore radius – rp (nm)
λ= rs/rp
pore radius – rp (nm)
λ= rs/rp
0.42
1.12
0.34
1.38
0.47
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4. Conclusions Nanofiltration showed viability to concentrate norfloxacin present in wastewater, considering the higher rejections obtained at this work. The results showed that the NOR rejection ranged from 87
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to 95% and was dependent on the membrane and solution characteristics.
The solution chemistry (pH) may influence the dissociation of solute and the active groups of the membranes, leading to electrostatic interactions (repulsion or attraction) and, together with the
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concentration polarization, may decrease the permeation flux and increase or decrease the
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rejection. At this work, the highest rejection coefficients (> 94%) were obtained at pH 6.5, which
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is the pH of the wastewater to be treated, indicating that no pH correction would be necessary to
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Acknowledgements
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its treatment.
The authors thank the research support agencies (CYTED, FINEP, CNPq, CAPES, FAPERGS
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and SCIT/RS) for the financial support.
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Declarations of interest: none.
References
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[1] EU, Directive 39/EU of the European Parliament and of the Council of 12 August 2013 amending Directives 2000/60/EC and 2008/105/EC as regards priority substances in the field of water policy, Luxembourg: Official Journal of the European Union, 24 (2013). [2] S. Shanmuganathan, P. Loganathan, C. Kazner, M.A.H. Johir, S. Vigneswaran, Submerged membrane filtration adsorption hybrid system for the removal of organic micropollutants from a water reclamation plant reverse osmosis concentrate, Desalination, 401 (2017) 134-141.
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[3] V.J. Wirtz, A. Dreser, R. Gonzales, Trends in antibiotic utilization in eight Latin American countries, 1997-2007, Revista Panamericana de Salud Pública, 27 (2010) 219-225.
Environmental Science & Technology, 44 (2010) 3468-3473.
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[4] B. Li, T. Zhang, Biodegradation and Adsorption of Antibiotics in the Activated Sludge Process,
[5] N. Collado, S. Rodriguez-Mozaz, M. Gros, A. Rubirola, D. Barceló, J. Comas, I. Rodriguez-
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Roda, G. Buttiglieri, Pharmaceuticals occurrence in a WWTP with significant industrial
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contribution and its input into the river system, Environmental Pollution, 185 (2014) 202-212. [6] X.-m. Wang, B. Li, T. Zhang, X.-y. Li, Performance of nanofiltration membrane in rejecting
A
trace organic compounds: Experiment and model prediction, Desalination, 370 (2015) 7-16.
M
[7] M. Homayoonfal, M.R. Mehrnia, Amoxicillin separation from pharmaceutical solution by pH
ED
sensitive nanofiltration membranes, Separation and Purification Technology, 130 (2014) 74-83. [8] Y.-l. Liu, X.-m. Wang, H.-w. Yang, Y.F. Xie, Adsorption of pharmaceuticals onto isolated polyamide active layer of NF/RO membranes, Chemosphere, 200 (2018) 36-47.
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[9] M.A. Khansary, M. Mellat, S.H. Saadat, M. Fasihi-Ramandi, M. Kamali, R.A. Taheri, An enquiry on appropriate selection of polymers for preparation of polymeric nanosorbents and
CC E
nanofiltration/ultrafiltration membranes for hormone micropollutants removal from water effluents, Chemosphere, 168 (2017) 91-99. [10] C. Bellona, D. Heil, C. Yu, P. Fu, J.E. Drewes, The pros and cons of using nanofiltration in
A
lieu of reverse osmosis for indirect potable reuse applications, Separation and Purification Technology, 85 (2012) 69-76. [11] V. Yangali-Quintanilla, S.K. Maeng, T. Fujioka, M. Kennedy, G. Amy, Proposing nanofiltration as acceptable barrier for organic contaminants in water reuse, Journal of Membrane Science, 362 (2010) 334-345.
15
[12] P. Liu, H. Zhang, Y. Feng, F. Yang, J. Zhang, Removal of trace antibiotics from wastewater: A systematic study of nanofiltration combined with ozone-based advanced oxidation processes, Chemical Engineering Journal, 240 (2014) 211-220. [13] D.G.J. Larsson, Pollution from drug manufacturing: review and perspectives, Philosophical Transactions of the Royal Society B: Biological Sciences, 369 (2014) 20130571. [14] S. Kim, P.A. Thiessen, E.E. Bolton, J. Chen, G. Fu, A. Gindulyte, L. Han, J. He, S. He, B.A.
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Shoemaker, J. Wang, B. Yu, J. Zhang, S.H. Bryant, PubChem Substance and Compound databases, Nucleic Acids Research, 44 (2016) D1202-D1213.
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[15] F.-x. Kong, H.-w. Yang, Y.-q. Wu, X.-m. Wang, Y.F. Xie, Rejection of pharmaceuticals during forward osmosis and prediction by using the solution–diffusion model, Journal of Membrane Science, 476 (2015) 410-420.
Technical
Manual.
Form
No.
U
[16] Dow, Dow Water and Process Solutions - FILMTEC™ Reverse Osmosis Membranes 609-00071-0416,
in:
Available
on:
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http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_095b/0901b8038095b91d.pdf?fil
A
epath=/609-00071.pdf&fromPage=GetDoc, 2011, pp. 181.
M
[17] L.D. Nghiem, A.I. Schäfer, M. Elimelech, Removal of Natural Hormones by Nanofiltration
38 (2004) 1888-1896.
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Membranes: Measurement, Modeling, and Mechanisms, Environmental Science & Technology,
[18] L.D. Nghiem, A.I. Schäfer, M. Elimelech, Pharmaceutical Retention Mechanisms by
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Nanofiltration Membranes, Environmental Science & Technology, 39 (2005) 7698-7705. [19] A. Giacobbo, A.M. Bernardes, M.N. de Pinho, Nanofiltration for the Recovery of Low
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Molecular Weight Polysaccharides and Polyphenols from Winery Effluents, Separation Science and Technology, 48 (2013) 2524-2530. [20] A. Giacobbo, A. Moura Bernardes, M. Filipe Rosa, M. de Pinho, Concentration Polarization
A
in Ultrafiltration/Nanofiltration for the Recovery of Polyphenols from Winery Wastewaters, Membranes, 8 (2018). [21] A. Giacobbo, A. Meneguzzi, A.M. Bernardes, M.N. de Pinho, Pressure-driven membrane processes for the recovery of antioxidant compounds from winery effluents, Journal of Cleaner Production, 155 (2017) 172-178.
16
[22] A. Einstein, Investigations on the Theory of the Brownian Movement, Dover Publications, New York, 1956. [23] A.D. Shah, C.-H. Huang, J.-H. Kim, Mechanisms of antibiotic removal by nanofiltration membranes: Model development and application, Journal of Membrane Science, 389 (2012) 234244. [24] A. Azaïs, J. Mendret, S. Gassara, E. Petit, A. Deratani, S. Brosillon, Nanofiltration for
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wastewater reuse: Counteractive effects of fouling and matrice on the rejection of pharmaceutical active compounds, Separation and Purification Technology, 133 (2014) 313-327.
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[25] C.d.M. da Trindade, A. Giacobbo, V.G. Ferreira, M.A.S. Rodrigues, A.M. Bernardes, Membrane separation processes applied to the treatment of effluents from nanoceramic coating operations, Desalination and Water Treatment, 55 (2015) 1-11.
U
[26] D.I. De Souza, A. Giacobbo, M.A.S. Rodrigues, A.M. Bernardes, Evaluation of antibiotics removal from wastewater by nanofiltration, in: D.F. Lekkas (Ed.) Proceedings of 15th
N
International Conference on Environmental Science and Technology - CEST2017, Global NEST,
A
Rhodes, Grece, 2017.
M
[27] Á. Soriano, D. Gorri, A. Urtiaga, Membrane preconcentration as an efficient tool to reduce the energy consumption of perfluorohexanoic acid electrochemical treatment, Separation and
ED
Purification Technology, (2018).
[28] A.J.C. Semião, A.I. Schäfer, Removal of adsorbing estrogenic micropollutants by
(2013) 244-256.
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nanofiltration membranes. Part A—Experimental evidence, Journal of Membrane Science, 431
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[29] M. Giagnorio, S. Steffenino, L. Meucci, M.C. Zanetti, A. Tiraferri, Design and performance of a nanofiltration plant for the removal of chromium aimed at the production of safe potable water, Journal of Environmental Chemical Engineering, 6 (2018) 4467-4475.
A
[30] A. Simon, J.A. McDonald, S.J. Khan, W.E. Price, L.D. Nghiem, Effects of caustic cleaning on pore size of nanofiltration membranes and their rejection of trace organic chemicals, Journal of Membrane Science, 447 (2013) 153-162. [31] Chemicalize, Chemicalize was used for norfloxacin microspeciation in aqueous solution as a function of pH, February, 2018, https://chemicalize.com/ developed by ChemAxon (http://www.chemaxon.com), in, 2018.
17
[32] J. Barbosa, D. Barrón, E. Jiménez-Lozano, Electrophoretic behaviour of quinolones in capillary electrophoresis: Effect of pH and evaluation of ionization constants, Journal of Chromatography A, 839 (1999) 183-192. [33] C. Bellona, J.E. Drewes, P. Xu, G. Amy, Factors affecting the rejection of organic solutes
A
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PT
ED
M
A
N
U
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during NF/RO treatment—a literature review, Water Research, 38 (2004) 2795-2809.
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S2213-3437(18)30567-0 https://doi.org/10.1016/j.jece.2018.09.034 JECE 2655
To appear in: Received date: Revised date: Accepted date:
30-7-2018 17-9-2018 18-9-2018
Please cite this article as: de Souza DI, Dottein EM, Giacobbo A, Siqueira Rodrigues MA, de Pinho MN, Bernardes AM, Nanofiltration for the Removal of Norfloxacin from Pharmaceutical Effluent, Journal of Environmental Chemical Engineering (2018), https://doi.org/10.1016/j.jece.2018.09.034 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.
Nanofiltration for the Removal of Norfloxacin from Pharmaceutical Effluent
Dalva Inês de Souza 1, Eugênio Minetto Dottein 1, Alexandre Giacobbo 1, Marco Antônio Siqueira Rodrigues 2, Maria Norberta de Pinho 3, Andréa Moura Bernardes 1, * Programa de Pós-Graduação em Engenharia de Minas, Metalúrgica e de Materiais – PPGE3M, Universidade Federal do Rio Grande do Sul – UFRGS. Av. Bento Gonçalves, n. 9500, Porto Alegre/RS, Brazil. Tel: +555133089428 - Fax: +555133089427
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1
Instituto de Ciências Exatas e Tecnológicas – ICET, Universidade Feevale, Rodovia 239, n. 2755 – Vila Nova, Novo Hamburgo/RS, Brazil. Tel: +555135868800 2
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3
Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, n. 1, 1049-001, Lisbon, Portugal.
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*corresponding author: e-mail: [email protected]
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Abstract Conventional treatment processes have presented low efficiency in removing antibiotics from
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water and effluents, wherefore the development of processes and technologies to comply with this
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matter is highly important. Membrane separation processes may be applied in the obtainment of high-quality reuse water, fully or partly removing the pharmaceuticals. Thus, this paper aims to
effluent
simulating
a
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assess the performance of two nanofiltration membranes in removing norfloxacin from a synthetic pharmaceutical
wastewater.
Different
solution
concentrations,
transmembrane pressures and pH were evaluated. Both membranes presented high selectivity to
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norfloxacin, such that thfe rejection of this antibiotic remained between 87 and 99.5%. The pH had an effect on membranes' selectivity and permeability. The highest norfloxacin rejection and
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the lowest permeability were reached at pH 6.5, which may be related to electrostatic interactions between membrane surface and norfloxacin ionic species. Considering the elevated rejections obtained in this study (87–99.5%), the viability of nanofiltration stands out in removing
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norfloxacin from effluents.
Keywords: Nanofiltration; Norfloxacin; Antibiotic Removal; Pharmaceutical Effluent.
1
1. Introduction The detection of contaminants of emerging concern in water bodies has increased in recent years, what is troubling, considering the levels in which they are found in the aquatic environment and the meaningful risks due to their potential toxicological effects [1]. In this sense, special attention has been given to the antibiotics, a class of contaminants of emerging concern, since they are responsible for causing bacterial resistance. The main sources, responsible for the contamination
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with these organic pollutants, are municipal wastewater and effluents from hospitals and the pharmaceutical industry, which, in general, are discharged without the appropriated treatment [2].
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In general, antibiotics are synthetic compounds that are not easily biodegradable. Among the antibiotics, norfloxacin (NOR) is one of the most consumed in Latin America [3], and consequently, it is one of the main antibiotics found in water bodies. NOR is a fluoroquinolone,
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and presents stability, structural complexity and antimicrobial activity, disturbing the conventional water and wastewater treatment processes [4-6]. Considering this approach, there is the need for
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investigation of other technologies for wastewater treatment. In this sense, taking into account
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their inherent characteristics, membranes technology may be used for the removal or concentration
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of antibiotics present in water and wastewater [7-9].
Bellona et al. [10] have conducted a research involving the operational and rejection performances
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of several nanofiltration membranes, such as NF 270, compared to a commonly employed reverse osmosis (ESPA2) membrane, at a water reclamation facility, in the removal of some nonionic,
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positive and negative pharmaceuticals, such as carbamazepine, sulfamethoxazole and atenolol, respectively. NF 270 membrane operated at specific double flux comparing to the flux of the
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ESPA2 membrane. NF 270 showed minimal flux declining and elevated water recovery (87–88%). It resulted in approximately 65% rejection of conductivity and approximately 83% rejection of total organic carbon (TOC). The rejections of atenolol, carbamazepine and sulfamethoxazole were 78.9 %, 88.0% and 98.0%, respectively. An economic analysis using data from pilot-scale testing
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and full-scale operation revealed significant cost savings using a low-pressure NF, such as the NF 270 membrane. Yangali-Quintanilla et al. [11] carried out a study with an aqueous cocktail of pharmaceuticals (neutral and ionic compounds), such as acetaminophen, carbamazepine, sulfamethoxazole, naproxen and others, using nanofiltration membranes (NF 90 and NF 200) and reverse osmosis membranes (BW30 LE and ESPA2). Tests were accomplished in bench, pilot and full scales to 2
obtain water reuse and concluded that tight nanofiltration polyamide membranes are an alternative to reverse osmosis (RO) [11], meaning that tight nanofiltration polyamide membranes, such as the NF 90, may be an effective barrier against pharmaceuticals, pesticides, endocrine disruptors and other organic contaminants. Some antibiotics, including norfloxacin, with high detection frequencies in effluents from Wastewater Treatment Plants (WWTP) in Dalian (China), were used in nanofiltration combined
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with ozone-based advanced oxidation processes. This research used a commercial NF membrane, NFX (Synder Filtration, Vacaville, CA, USA), similar to the NF 90 membrane. NFX has a
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polyamide layer skin and its molecular weight cut-off (MWCO) is in the range of 150 – 300 Da, NF 90 MWCO is approximately 200 Da. The rejections (>98 %) were high to all studied antibiotics. The study concluded that nanofiltration could remove antibiotics from the effluent, and UV/O3 process was able to further eliminate the antibiotics from the NF concentrate effectively
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[12].
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In the light of these considerations, the present study was conducted to assess the performance on
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productivity (permeation flux) and selectivity (evaluated with the rejection coefficient) of two
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nanofiltration membranes, NF 90 and NF 270, in removing norfloxacin from a pharmaceutical effluent. The effects of pH, concentration and operation pressure on rejection and permeation flux
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were assessed. In addition, the interactions solute/membranes in several conditions were
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investigated.
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2. Material and Methods 2.1 Feed Solutions
To simulate wastewater from the pharmaceutical industry and assess the mechanisms involved in
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nanofiltration, synthetic aqueous solutions with pure (99.9%) norfloxacin (NOR), obtained in a veterinarian clinic, were used. Table 1 shows data of the pharmaceutical used. Permeation and rejection experiments were carried out with NOR aqueous solutions, at a concentration range (5, 25 and 50 mg.L–1) found in pharmaceutical wastewater [13]. The influence of pH upon the rejection mechanisms was verified for 50 mg.L–1 NOR solutions at pH 6.5 (natural
3
pH), pH 2.4 (acidified with 1 M HCl) and pH 9.8 (adjusted with 1 M NaOH). All feed solutions were made with distilled/deionized water (conductivity ≤ 2 µS.cm–1).
Physicochemical characteristics
Norfloxacin
Molecular formulaa
C16H18FN3O3
Molecular weighta
319.331 Da
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pKab
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Table 1. Physicochemical characteristics of the pharmaceutical used (norfloxacin).
6.34; 8.57
N
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Structural formula a
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Stokes radius (nm)c
5.22
M
Diffusion coefficient (10–10.m2.s–1)c
0.47
From Kim et al. [14];
b
From Homayoonfal and Mehrnia [7];
c
Estimated from Stokes–Einstein equation using Wilke–Chang diffusion coefficient [15];
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a
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2.2 Membranes Characterization The permeation experiments were performed with two flat-sheet nanofiltration membranes, NF 270 and NF 90 (Filmtec – Minneapolis, MN). Concerning the filtration range, membranes have
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MWCO of approximately 200 Da for NF 90, considered a narrow band, and around 400 Da for NF 270, considered a broad brand [16]. The pore radius of the membranes were determined by Nghiem et al. [17] through permeation experiments with reference solutes: dextrose, xylose, erythritol, dioxane. According to the authors [17], the pore radii for the membranes NF 90 and NF 270 are 0.34 nm and 0.42 nm, respectively. These membranes have a thin film (skin) of
4
polyamide over a layer of polysulfone on a polyester support layer. The skin is a mixture of aromatic and aliphatic polyamide with amine and carboxylates end groups [16]. The surface layer of polyamide membranes contains amine groups, H+ receptors, and carboxylic groups, H+ donors, which give it an amphoteric characteristic. The isoelectric point (IEP) is around 3.5 for NF 270 and 4.0 for NF 90 [18]. At pH lower than the IEP, membrane surface becomes cationic due to protonation of the amine group (NH3+). At pH higher than the IEP, membrane
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surface becomes anionic due to deprotonation of the carboxyl group (COO–). At the IEP, there is a balance of charges between the cationic and anionic sites of the polymer on the membrane
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surface, which remains neutral, a zwitterion (Z).
First, each membrane was compacted through recirculation of distilled and deionized water (conductivity ≤ 2 µS.cm–1) with the pressure of 25 bar for 3 hours. The purpose of this procedure
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was to prevent possible changes in the membranes’ structure with subsequent working pressures. Membranes were characterized in terms of their hydraulic permeability (Lpw), as described by
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Giacobbo et al. [19], at transmembrane pressures (ΔP) of 5, 7, 10, 15 bar, and regarding salts
A
rejection (sodium chloride, calcium chloride and sodium sulfate) at 10 bar, using electrolyte
𝐶𝑓 −𝐶𝑝 𝐶𝑓
⌋ 100
Eq. (1)
ED
R (%) = ⌊
M
solutions at 2000 mg.L–1 concentration. The rejection coefficient (R) was defined as:
Where Cf is the average between final and initial feed solution concentration and Cp is the
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concentration of permeate. In all experiments, the temperature was 25 ± 1 °C, and feed flow rate was 3.3 L.min–1. This feed flow rate was chosen based on previous studies at the same cell [20]
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and corresponds to a tangential velocity of 0.96 m.s–1 and a Reynolds number close to 23,000. The choice was done in order to minimize the concentration polarization incidence. The setting time of every experiment was 30 minutes. Between the experiments, membrane washing was always carried out using distilled/deionized water and 0.1% NaOH solution with cycles of 30 minutes at
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30 °C and 25 °C until Lpw reached at least 90% of the initial Lpw obtained after compaction.
5
2.3. Nanofiltration Permeation Experiments The permeation experiments were carried out with two flat cells of membrane surface area of 14.5 x 10–4 m2 each, and with feed flow rate of 3.3 L.min–1 in a lab-bench unit thoroughly described by Giacobbo et al. [21], shown in Figure 1. Experiments were performed in total recirculation mode, where the permeate and the retentate
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streams were recirculated to the feed tank to keep feed concentration constant. Thus, at steady state, the variation of the permeation flux (Jp) and of the solute rejection coefficients with ΔP were
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evaluated.
Experiments ran at 25 ± 1 °C, being the temperature regulated by an ultra-thermostatic bath (Nova Ética) attached to the feed tank. The stabilization time for each ΔP was 30 min. Permeate and feed samples of each ΔP were taken for analysis. All experiments of this research were conducted at
A
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PT
ED
M
A
N
U
least twice.
6
Figure 1. Set up of the filtration unit. 1-Feed tank, 2-Heat exchanger, 3-Two-way valve, 4-Pump, 5-By-pass valve, 6-Manometers, 7-Membrane, 8-Permeation cell, 9-Permeate sample, 10Pressure-regulation valve, 11-Rotameter. Adapted from Giacobbo et al. [21]. Due to the possibility of hydrolysis occurrence in aqueous solution with the solution aging, all NOR solutions were prepared on the time of the experiment. Each membrane filtration experiment
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took a maximum of 4 hours, and each sample collected during the experiment, at each ΔP, was
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immediately taken to analysis.
2.4 Transport of Solute and Rejection by Membrane
The transport of the solute through the hydrodynamic model assumes NF membranes to have
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pores. For study purposes, the pores are considered cylindrical and with uniform radius. The ratio
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between solute radius (rs) and membrane pore radius (rp), defined as λ (= rs/rp), is an important
A
factor to predict the solute rejection. In general, the solute Stokes radius is used to evaluate steric hindrance assuming rigid molecules with spherical shape. It can be calculated by Stokes-Einstein
M
equation [22]. The λ is used to estimate a distribution coefficient ɸ (=1–rs/rp)2. This coefficient is equal to the equilibrium partition at the entrance and exit on the membrane pore. When λ is larger
ED
than 1.0, it is predicted that rejection will be 100%, just governed by steric relationship and
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equilibrium partitioning behavior [23].
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2.5. Analytical Methods
Conductivity and pH were measured using an AKSO 8306 conductivity meter and a Tek PHS-3B pH meter, respectively. A Thermo Scientific HPLC system equipped with a Supelco Drug
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Discovery C-18 column (with diameter, length and pore size of 4.6 mm, 100 mm and 3 µm, respectively) and an UV–vis detector was used to measure the antibiotic concentrations in the feed and permeate. The detection wavelength was set at 277 nm. The mobile phase used for isocratic elution was methanol and acetic acid 5% v/v (40:60) which was delivered at 0.75 mL.min–1 through the column. A sample injection volume of 20 µL was used. The oven temperature was 30 °C. A calibration yielded standard curve, with coefficient of determination (R2) greater than
7
0.999 within the range of experimental concentrations, was used (Figure S1). The analyzes were carried out immediately on the conclusion of each experiment.
3. Results and Discussion
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3.1. Membrane Characterization Regarding average water permeability (Lpw), the NF 270 and NF 90 membranes presented 17.38 and 6.86 kg.h–1.m–2.bar–1, respectively. In terms of rejection coefficient (R) to the referring salts,
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NF 270 membrane reached 52%, 71% and 98% for sodium chloride, calcium chloride and sodium sulfate, while NF 90 presented 90%, 97% and 99%, respectively. These results are in accordance
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with the ones reported in the other works [24-29].
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3.2. Effects of pH and ΔP on Permeation Flux and Rejection
A
In Figure 2 are shown the permeation fluxes of 50 mg.L–1 NOR solutions at different values of pH
M
and ΔP, while in Table 2 are displayed the solutions permeabilities (Lps) and the rejection to norfloxacin as a function of solution pH. As ΔP increases, the permeation flux of all solutions
ED
increases, as expected. In addition, it was also expected an increase in permeation flux by increasing the solution pH. According to Simon et al. [30], when pH solution changes, the pore size and the surface hydrophilicity of the polyamide NF membranes may change. The authors [30]
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stated that caustic cleaning led to a small increase in pore size and surface hydrophilicity of the NF 270 membrane, resulting in a notable increase in the permeability and salt passage. By contrast,
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the impact on the NF 90 membrane was negligible [30]. At this work, for the NF 270 membrane, taking into account the standard deviation of all experimental run repetitions, no significant difference was observed between the permeabilities to
A
the pure water and to the NOR solutions with pH 2.4 and 9.8. On the other hand, for the NF 90 membrane, only the permeability to the NOR solution with pH 9.8 closed to the one achieved with pure water. Besides, for both membranes, the Lps mean values achieved with the NOR solution at pH 6.5 were always the lowest ones. In addition, at pH 6.5 were obtained the highest NOR rejections. This behavior was mainly expected with the most acid solution (pH 2.4). It occurs that, at pH 6.5, membranes present anionic surface charge, once the pH of the solution is higher than 8
the IEP of the membranes. NOR also presents amine and carboxyl groups and has two pKa values, pKa1 = 5.58 and pKa2 = 8.68. 300 NF 270
250
Lpw = 17.38 kg.h-1.m-2.bar-1
200
pH 2.4
150
pH 6.5
100
pH 9.8
Lps pH 2.4 = 14.57 kg.h-1.m-2.bar-1
50
Lps pH 6.5 = 11.57 kg.h-1.m-2.bar-1 Lps pH 9.8 = 15.22 kg.h-1.m-2.bar-1
0 0
5
10
15
20
N
200
150
M
Lpw = 8.72 kg.h-1.m-2.bar-1
A
NF 90
Pure water pH 2.4
ED
100
50
pH 6.5
Lps pH 2.4 = 6.97 kg.h-1.m-2.bar-1
pH 9.8
Lps pH 6.5 = 6.66 kg.h-1.m-2.bar-1
0
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0
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Permeation flux (kg.h–1.m–2)
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Pressure (bar) b)
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Pure water
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Permeation flux (kg.h–1.m–2)
a)
5
Lps pH 9.8 = 8.38 kg.h-1.m-2.bar-1
10
15
20
Pressure (bar)
Figure 2. Permeation fluxes of 50 mg.L–1 NOR solution as a function of ΔP and solution pH. Operating conditions: feed flow rate of 3.3 L.min–1 and temperature of 25 °C. (a) NF 270
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membrane and (b) NF 90 membrane.
Table 2. Rejection and permeability results of 50 mg. L–1 NOR aqueous solution at different pH values. Operating conditions: ΔP = 5–12 bar; T = 25 °C; feed flow rate = 3.3 L.min–1. NF 270
NF 90
9
Solution pH
R (%)
2.4
Lps
Lps
(kg.h .m .bar )
Lpw-Lps (%)
R (%)
(kg.h .m .bar )
Lpw-Lps (%)
89.2 ± 2.92
14.57
16.2
98.3 ± 0.47
6.97
20.1
6.5
93.6 ± 1.47
11.57
33.4
99.5 ± 0.08
6.66
23.6
9.8
87.0 ± 0.87
15.22
12.4
98.0 ± 0.28
8.34
3.90
–1
–2
–1
–1
–2
–1
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Figure 3 presents the distribution of norfloxacin species in aqueous solution as a function of pH. Below the pKa1 NOR is mainly positive, above pKa2 it is predominantly negative and at the pKa, it is zwitterion (± neutral species), i.e., between pH 5.58 and 8.68, it is mainly presented in the
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neutral form.
At pH 6.5, the membranes are anionic and NOR speciation presents around 10.6% in the cationic form, around 88.7% in the neutral form (zwitterion) and 0.6% is NOR anionic (Figure 3). Thus, a
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strong attraction between the cationic solute and the negatively charged functional groups from
N
the membrane surface may occur. This electrostatic attraction effect can generates concentration polarization and fouling, explaining the lowest solution permeability, when compared to the water pKa1
pKa2
A
permeability (representing a reduction of 33.4 and 23.6% for NF 90 and NF 270, respectively) and
M
to the other pH solutions. A higher rejection (99.6 and 93.6% for NF 90 and NF 270, respectively)
100 80
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Distribution of NOR species (%)
a)
ED
was also a consequence, as shown in Table 2.
60
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40 20 0
0
1
2
4
5
6
8
9
10
A
Neutral specie (±)
Cationic specie 2+
O
O
O
0H-
0H
F
+
+
+
H3C
NOR cationic form
13
14
O
O
0H-
-
F O
OH
N H
12
Cationic specie 1+
F
N
11
Anionic specie (1-)
OH
H2N
7
pH
O
O
b) (a)
3
N
N
H
H 2N
H
+
pka = 5.58
+
H3C
NOR cationic form
N
N H2N
H3C
NOR neutral form
F
-
O H
-
+
pKa = 8.68
+
O
N
N HN H3C
NOR anionic form
10
Figure 3. a) Distribution of norfloxacin species in aqueous solution as a function of pH, prediction calculated data from Chemicalize software [31], b) NOR species as a function of pH and pKa, Z=
3.3 Concentration and ΔP Effects on Permeation Flux and Rejection
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zwitterion, adapted from Barbosa et al. [32].
In Figure 4 are shown the permeation fluxes of NOR solutions at pH 6.5 with different solute
300 250
N
NF 270
A
Lpw = 17.38 kg.h-1.m-2.bar-1
M
200 150
Pure water 5 mg.L-1 25 mg.L-1
ED
100
Lps 5 = 13.53 kg.h-1.m-2.bar-1
50 mg.L-1
Lps 25 = 12.29 kg.h-1.m-2.bar-1
50
Lps 50 = 11.57 kg.h-1.m-2.bar-1
0
5
10
15
20
Pressure (bar)
A
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0
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Permeation flux (kg.h–1.m–2)
a)
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rejection to norfloxacin as a function of solute concentration.
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concentrations and ΔP, while in Table 3 are displayed the solutions permeabilities (Lps) and the
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b)
180
Permeation flux (kg.h–1.m–2)
150
NF 90 Lpw = 8.72 kg.h-1.m-2.bar-1
120 Pure water
90
5 mg.L-1
50 mg.L-1
Lps 5 = 7.54 kg.h-1.m-2.bar-1
30
Lps 25 = 7.18 kg.h-1.m-2.bar-1 Lps 50 = 6.66 kg.h-1.m-2.bar-1
0 5
10
15
20
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0
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25 mg.L-1
60
Pressure (bar)
Figure 4. Permeation fluxes as a function of ΔP and feed solution concentration. Operating
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conditions: feed flow rate of 3.3 L.min–1, temperature of 25 °C, and solution pH of 6.5. a)
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NF 270 membrane, b) NF 90 membrane.
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Regarding the different concentrations of NOR, the results show that, in general, the higher the
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concentration, the lower the permeation flux and the higher the rejection for both studied membranes (NF 270 and NF 90). The increase in the solute concentration necessarily leads to an
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increase in the osmotic pressure, reducing the effective transmembrane pressure and, consequently, the permeation flux. In addition, an increase in the solute concentration at the boundary layer adjacent to the membrane surface (in the retentate side) acts as an additional
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resistance to the solute passage, increasing the NOR rejection.
Table 3. Effects of NOR solution concentration on permeability and rejection. Operating conditions: ΔP = 5–12 bar; T = 25 °C; feed flow rate = 3.3 L.min–1; pH solution = 6.5.
NOR concentration (mg.L–1)
NF 270
NF 90 R
Lps
R
(kg.h–1.m–2.bar–1)
(%)
(kg.h–1.m–2.bar–1)
(%)
5
13.53
91.29 ± 3.21
7.54
98.85 ± 0.20
25
13.13
97.45 ± 0.39
7.18
98.86 ± 0.39
50
11.57
93.62 ± 1.48
6.66
99.45 ± 0.08
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Lps
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As previously reported, at pH 6.5, the surface of both membranes is negatively charged, and, although at this pH the NOR is mostly neutral, the solution still presents about 10% of cationic species that may result in attraction between anionic sites from the membrane and cationic species of solute. When the concentration increases even more, it increases the density of species of solute near the membrane, hindering the mass transfer through it. Thereby, there is a tendency in increasing the rejection and diminishing the flux. For both membranes, the rejection increases and
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flux decreases probably due concentration polarization and reversible fouling, especially on NF 270 (the broader membrane). However, with the highest NOR concentration (50 mg.L–1), the NF 270 presented a lower rejection than the one achieved with 25 mg.L–1 solution. This behavior
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can be attributed to the fact that, in this case, the higher concentration polarization incidence (increase solute concentration near the membrane surface) facilitates the passage of NOR into the permeate, reducing the rejection coefficient.
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Regarding the NF 90 membrane, the results indicate that there is a prevalence of the stereo
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chemical exclusion as a function of pore size (sieve effect) or molecular exclusion as a function of the MWCO of the membrane (MWsolute > MWCONF90). NF 90 is a narrow-band membrane, and
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according to Bellona et al. [33], NF narrow-band membranes (MWCO ≤ 200 Da or Na+ > 90%
M
rejection) restrict the transport of solute across the membrane similarly to reverse osmosis
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membranes, that is, by limiting stereo chemical diffusion and exclusion. According to the literature data, the rp values for NF 90 and NF 270 are 0.34 nm and 0.42 nm, respectively, while the norfloxacin radius is 0.47 nm. The ratio between the radius of the neutral
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solute and the membrane pore radius (λ= rs/rp) is greater than 1.0 for both membranes, as shown in Table 4. When λ is greater than 1.0, the rejection should be 100%. On the contrary, at the present
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work, the NOR rejection ranged from 87% to 95.5% indicating that the rejection was membranedependent and affected by pH and electrostatic interactions and not just governed by steric relationship and equilibrium partitioning behavior. In fact, it is also important to consider that, although the stokes radius of Norfloxacin is slightly higher than pore radius, the membrane pore
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radius is a mean value, which mean that the membrane may exhibit pores larger than 0.47 nm if the average is 0.42 nm, which will also allow the transport through the membrane.
Table 4. Data related to NOR radius and membrane pores radius.
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Solute radius – rs (nm)
NF 270
NF 90
pore radius – rp (nm)
λ= rs/rp
pore radius – rp (nm)
λ= rs/rp
0.42
1.12
0.34
1.38
0.47
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4. Conclusions Nanofiltration showed viability to concentrate norfloxacin present in wastewater, considering the higher rejections obtained at this work. The results showed that the NOR rejection ranged from 87
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to 95% and was dependent on the membrane and solution characteristics.
The solution chemistry (pH) may influence the dissociation of solute and the active groups of the membranes, leading to electrostatic interactions (repulsion or attraction) and, together with the
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concentration polarization, may decrease the permeation flux and increase or decrease the
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rejection. At this work, the highest rejection coefficients (> 94%) were obtained at pH 6.5, which
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is the pH of the wastewater to be treated, indicating that no pH correction would be necessary to
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Acknowledgements
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its treatment.
The authors thank the research support agencies (CYTED, FINEP, CNPq, CAPES, FAPERGS
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and SCIT/RS) for the financial support.
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Declarations of interest: none.
References
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[1] EU, Directive 39/EU of the European Parliament and of the Council of 12 August 2013 amending Directives 2000/60/EC and 2008/105/EC as regards priority substances in the field of water policy, Luxembourg: Official Journal of the European Union, 24 (2013). [2] S. Shanmuganathan, P. Loganathan, C. Kazner, M.A.H. Johir, S. Vigneswaran, Submerged membrane filtration adsorption hybrid system for the removal of organic micropollutants from a water reclamation plant reverse osmosis concentrate, Desalination, 401 (2017) 134-141.
IP T
[3] V.J. Wirtz, A. Dreser, R. Gonzales, Trends in antibiotic utilization in eight Latin American countries, 1997-2007, Revista Panamericana de Salud Pública, 27 (2010) 219-225.
Environmental Science & Technology, 44 (2010) 3468-3473.
SC R
[4] B. Li, T. Zhang, Biodegradation and Adsorption of Antibiotics in the Activated Sludge Process,
[5] N. Collado, S. Rodriguez-Mozaz, M. Gros, A. Rubirola, D. Barceló, J. Comas, I. Rodriguez-
U
Roda, G. Buttiglieri, Pharmaceuticals occurrence in a WWTP with significant industrial
N
contribution and its input into the river system, Environmental Pollution, 185 (2014) 202-212. [6] X.-m. Wang, B. Li, T. Zhang, X.-y. Li, Performance of nanofiltration membrane in rejecting
A
trace organic compounds: Experiment and model prediction, Desalination, 370 (2015) 7-16.
M
[7] M. Homayoonfal, M.R. Mehrnia, Amoxicillin separation from pharmaceutical solution by pH
ED
sensitive nanofiltration membranes, Separation and Purification Technology, 130 (2014) 74-83. [8] Y.-l. Liu, X.-m. Wang, H.-w. Yang, Y.F. Xie, Adsorption of pharmaceuticals onto isolated polyamide active layer of NF/RO membranes, Chemosphere, 200 (2018) 36-47.
PT
[9] M.A. Khansary, M. Mellat, S.H. Saadat, M. Fasihi-Ramandi, M. Kamali, R.A. Taheri, An enquiry on appropriate selection of polymers for preparation of polymeric nanosorbents and
CC E
nanofiltration/ultrafiltration membranes for hormone micropollutants removal from water effluents, Chemosphere, 168 (2017) 91-99. [10] C. Bellona, D. Heil, C. Yu, P. Fu, J.E. Drewes, The pros and cons of using nanofiltration in
A
lieu of reverse osmosis for indirect potable reuse applications, Separation and Purification Technology, 85 (2012) 69-76. [11] V. Yangali-Quintanilla, S.K. Maeng, T. Fujioka, M. Kennedy, G. Amy, Proposing nanofiltration as acceptable barrier for organic contaminants in water reuse, Journal of Membrane Science, 362 (2010) 334-345.
15
[12] P. Liu, H. Zhang, Y. Feng, F. Yang, J. Zhang, Removal of trace antibiotics from wastewater: A systematic study of nanofiltration combined with ozone-based advanced oxidation processes, Chemical Engineering Journal, 240 (2014) 211-220. [13] D.G.J. Larsson, Pollution from drug manufacturing: review and perspectives, Philosophical Transactions of the Royal Society B: Biological Sciences, 369 (2014) 20130571. [14] S. Kim, P.A. Thiessen, E.E. Bolton, J. Chen, G. Fu, A. Gindulyte, L. Han, J. He, S. He, B.A.
IP T
Shoemaker, J. Wang, B. Yu, J. Zhang, S.H. Bryant, PubChem Substance and Compound databases, Nucleic Acids Research, 44 (2016) D1202-D1213.
SC R
[15] F.-x. Kong, H.-w. Yang, Y.-q. Wu, X.-m. Wang, Y.F. Xie, Rejection of pharmaceuticals during forward osmosis and prediction by using the solution–diffusion model, Journal of Membrane Science, 476 (2015) 410-420.
Technical
Manual.
Form
No.
U
[16] Dow, Dow Water and Process Solutions - FILMTEC™ Reverse Osmosis Membranes 609-00071-0416,
in:
Available
on:
N
http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_095b/0901b8038095b91d.pdf?fil
A
epath=/609-00071.pdf&fromPage=GetDoc, 2011, pp. 181.
M
[17] L.D. Nghiem, A.I. Schäfer, M. Elimelech, Removal of Natural Hormones by Nanofiltration
38 (2004) 1888-1896.
ED
Membranes: Measurement, Modeling, and Mechanisms, Environmental Science & Technology,
[18] L.D. Nghiem, A.I. Schäfer, M. Elimelech, Pharmaceutical Retention Mechanisms by
PT
Nanofiltration Membranes, Environmental Science & Technology, 39 (2005) 7698-7705. [19] A. Giacobbo, A.M. Bernardes, M.N. de Pinho, Nanofiltration for the Recovery of Low
CC E
Molecular Weight Polysaccharides and Polyphenols from Winery Effluents, Separation Science and Technology, 48 (2013) 2524-2530. [20] A. Giacobbo, A. Moura Bernardes, M. Filipe Rosa, M. de Pinho, Concentration Polarization
A
in Ultrafiltration/Nanofiltration for the Recovery of Polyphenols from Winery Wastewaters, Membranes, 8 (2018). [21] A. Giacobbo, A. Meneguzzi, A.M. Bernardes, M.N. de Pinho, Pressure-driven membrane processes for the recovery of antioxidant compounds from winery effluents, Journal of Cleaner Production, 155 (2017) 172-178.
16
[22] A. Einstein, Investigations on the Theory of the Brownian Movement, Dover Publications, New York, 1956. [23] A.D. Shah, C.-H. Huang, J.-H. Kim, Mechanisms of antibiotic removal by nanofiltration membranes: Model development and application, Journal of Membrane Science, 389 (2012) 234244. [24] A. Azaïs, J. Mendret, S. Gassara, E. Petit, A. Deratani, S. Brosillon, Nanofiltration for
IP T
wastewater reuse: Counteractive effects of fouling and matrice on the rejection of pharmaceutical active compounds, Separation and Purification Technology, 133 (2014) 313-327.
SC R
[25] C.d.M. da Trindade, A. Giacobbo, V.G. Ferreira, M.A.S. Rodrigues, A.M. Bernardes, Membrane separation processes applied to the treatment of effluents from nanoceramic coating operations, Desalination and Water Treatment, 55 (2015) 1-11.
U
[26] D.I. De Souza, A. Giacobbo, M.A.S. Rodrigues, A.M. Bernardes, Evaluation of antibiotics removal from wastewater by nanofiltration, in: D.F. Lekkas (Ed.) Proceedings of 15th
N
International Conference on Environmental Science and Technology - CEST2017, Global NEST,
A
Rhodes, Grece, 2017.
M
[27] Á. Soriano, D. Gorri, A. Urtiaga, Membrane preconcentration as an efficient tool to reduce the energy consumption of perfluorohexanoic acid electrochemical treatment, Separation and
ED
Purification Technology, (2018).
[28] A.J.C. Semião, A.I. Schäfer, Removal of adsorbing estrogenic micropollutants by
(2013) 244-256.
PT
nanofiltration membranes. Part A—Experimental evidence, Journal of Membrane Science, 431
CC E
[29] M. Giagnorio, S. Steffenino, L. Meucci, M.C. Zanetti, A. Tiraferri, Design and performance of a nanofiltration plant for the removal of chromium aimed at the production of safe potable water, Journal of Environmental Chemical Engineering, 6 (2018) 4467-4475.
A
[30] A. Simon, J.A. McDonald, S.J. Khan, W.E. Price, L.D. Nghiem, Effects of caustic cleaning on pore size of nanofiltration membranes and their rejection of trace organic chemicals, Journal of Membrane Science, 447 (2013) 153-162. [31] Chemicalize, Chemicalize was used for norfloxacin microspeciation in aqueous solution as a function of pH, February, 2018, https://chemicalize.com/ developed by ChemAxon (http://www.chemaxon.com), in, 2018.
17
[32] J. Barbosa, D. Barrón, E. Jiménez-Lozano, Electrophoretic behaviour of quinolones in capillary electrophoresis: Effect of pH and evaluation of ionization constants, Journal of Chromatography A, 839 (1999) 183-192. [33] C. Bellona, J.E. Drewes, P. Xu, G. Amy, Factors affecting the rejection of organic solutes
A
CC E
PT
ED
M
A
N
U
SC R
IP T
during NF/RO treatment—a literature review, Water Research, 38 (2004) 2795-2809.
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