Removal of pharmaceuticals from municipal wastewater by adsorption onto pyrolyzed pulp mill sludge

R.N. Coimbra; V. Calisto; C.I.A. Ferreira; V.I. Esteves; M. Otero

doi:10.1016/j.arabjc.2015.12.001

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Original article

12 (

); 3611-3620

doi:

10.1016/j.arabjc.2015.12.001

Removal of pharmaceuticals from municipal wastewater by adsorption onto pyrolyzed pulp mill sludge

R.N. Coimbra^{^a}, V. Calisto^{^b}, C.I.A. Ferreira^{^b}, V.I. Esteves^{^b}, M. Otero^{^a,⁎}

a Department of Applied Chemistry and Physics, Institute of Environment, Natural Resources and Biodiversity (IMARENABIO), University of León, León 24071, Spain

b Department of Chemistry and CESAM (Centre for Environmental and Marine Studies), University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal

⁎Corresponding author. marta.otero@unileon.es (M. Otero)

Received: 2015-8-22, Accepted: 2015-12-1, Published: 2015-12-01

Disclaimer:
This article was originally published by Elsevier and was migrated to Scientific Scholar after the change of Publisher.

Peer review under responsibility of King Saud University.

Abstract

A charcoal was produced from primary pulp mill sludge and then used for the adsorptive removal of diclofenac, salicylic acid, ibuprofen and acetaminophen. A main aim was to assess the utilization of this material for the tertiary treatment of sewage. For this purpose, the adsorption of the selected pharmaceuticals from the secondary effluent of a sewage treatment plant (STP) was compared with their adsorption from ultrapure water. Differences in the adsorption kinetics and equilibrium were evident between the four pharmaceuticals considered. However, differences between the adsorption from the two aqueous matrixes considered were negligible. It was hypothesized that synergetic microorganism removal compensated the competitive effects in wastewater.

Keywords

Paper sludge

Pyrolysis

Wastewater treatment

Emerging contaminants

Pain reliever

Sorption

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1 Introduction

The pulp and paper industry is a strategic economic sector in Europe that largely contributes to the European Union (EU) financial growth and job creation (CEPI, 2013). However, a main counterpart is that pulp and paper production processes are very demanding in terms of energy and water and this industry is considered one of the most polluting in the world (Ince et al., 2011). As a consequence of the high water consumption, large wastewater volumes are generated by the pulp and paper industry. This wastewater must be treated before discharge in order to accomplish with environmental regulations (Pokhrel and Viraraghavan, 2004). Therefore sludge from wastewater treatment is an unavoidable waste for the pulp and paper industry. Elliott and Mahmood (2005) estimated that around 50 kg of dry sludge result from the production of a tonne of paper, of which approximately 70% is primary sludge and 30% is secondary sludge. Thermal valorization may be considered a viable management choice for such wastes given that landfilling has been prohibited at the EU and that alternatives such as agriculture application or composting are not viable due to the composition of sludge from the pulp and paper industry (Méndez et al., 2009).

Among thermal valorization options for the pulp and paper wastes it is pyrolysis, also called destructive distillation (Monte et al., 2009). It involves the heating of the organic waste in the absence of oxygen yielding a mixture of gaseous and liquid fuels, with a solid inert residue (char). Yang et al. (2013) reported that gas, liquid (bio-oil) and char and gas yields were 11, 10 (27.9 daf, wt%) and 79 wt%, respectively, and that the bio-oil, with a higher heating value (HHV) of 36.5 MJ kg⁻¹ and low oxygen content, supplied heat enough to power a diesel engine. Then, Ridout et al. (2015) proved that the bio-oil yield could be increased by fast pyrolysis. However, in practice, pyrolysis is not a preferred management option for paper industry wastes (Monte et al., 2009). Adding some value to the solid residue (char) from pyrolysis would undoubtedly boost this waste-to-energy management choice. The practical utilization of char as adsorbent for wastewater treatment is a way to do it. In this sense, chars from different paper waste materials have been used to adsorb trace metals (Méndez et al., 2009) and pharmaceuticals (Calisto et al., 2014) from water.

Traditionally, pharmaceuticals were not considered as environmental pollutants, but at present they constitute a group of great concern among emerging contaminants (ECs). Pharmaceuticals were designed to cause a physiological response and their presence in the environment may affect non-target individuals and species, which has raised alarms for possible impacts on human health (Santos et al., 2010). The way that ECs enter the environment depends on their pattern of usage and mode of application but, in the case of pharmaceuticals coming from human use and/or excretion, municipal sewage treatment plants (STPs) are important sources in the aquatic environment (Farré et al., 2008). Actually, STPs were conceived to reduce the concentration of legislated parameters, such as chemical oxygen demand (COD), biological oxygen demand (BOD), total suspended solids (TST) and nutrients but not emerging contaminants (ECs), such as pharmaceuticals. However, it is expected that in the nearer future more strict legislation will come out on the discharge of pharmaceuticals. In fact, pharmaceuticals have been included in the first observation list of the Water Framework Directive (WFD). Removal of these pollutants at STPs could be attained by the inclusion of a tertiary treatment before discharge. Among the several treatment options, adsorptive processes have been pointed to have large potential for the removal of ECs from water as they do not imply the generation of transformation products (Bolong et al., 2009; Priac et al., 2014). Furthermore, adsorptive treatments are advantageous from a practical point of view, due to their convenience incorporation into current water treatment processes (Domínguez et al., 2011).

In this context, research on the adsorptive removal of ECs and, namely, pharmaceuticals from water has largely increased in the last years. However, most of the published works report the adsorption of this sort of pollutants onto different adsorbents from distilled or ultrapure water but not from real wastewater. However, a main issue for the applicability of any adsorbent in tertiary treatment is the study of its utilization for pharmaceuticals adsorption from real wastewater. Therefore, this work aimed to assess the utilization of pyrolyzed paper mill sludge for the removal of pharmaceuticals from wastewater by comparing their adsorption from the secondary effluent of a STP with their adsorption from ultrapure water. For this purpose, the selected pharmaceuticals were pain relievers, namely diclofenac, ibuprofen, salicylic acid and acetaminophen. These pharmaceuticals belong to the anti-inflammatory and/or analgesic groups and among the most commonly used of all medications in the world and, consequently, also among the most frequently found drugs in STP effluents and natural waters.

2 Materials and methods

2.1

2.1 Adsorbent materials

Primary sludge (PS) was collected from a mill that employs the kraft elemental chlorine free (ECF) pulp production process, which operates exclusively with eucalyptus wood (Eucalyptus globulus). PS, which is produced at an average rate of 20 kg per ton of air-dried pulp, results from fibers rejected after the cooking/digestion pulping step and losses of fibers and other solids which occur when liquid effluents are involved (for example, washing and bleaching). After collection, PS was dried at room temperature and then subjected to oven drying at 60 °C, blade milled and pyrolyzed in a Nüve muffle (MF 106, Turkey). The pyrolysis was carried out at 800 °C under N₂ saturated atmosphere (N₂ flow of 0.5 dm³ min⁻¹) during 150 min. The pyrolysis of PS to obtain PS800-150 was meticulously described by Calisto et al. (2014), and a summary of the main properties of this char is displayed in Table 1. A detailed characterization of PS800-150, namely total organic carbon, FTIR, ¹³C and ¹H solid state NMR and SEM analysis may be found elsewhere (Calisto et al., 2014).

Table 1 Main properties of primary sludge from the paper industry before (PS) and after pyrolysis (PS800-150) (adapted from Calisto et al. (2014)).

	PS	PS800-150
Proximate analysis (wt%)
Moisture content	1.57	3.16
Ash	55.31	61.25
Volatile Matter (VM)	36.09	20.77
Fixed Carbon (FC)	8.60	17.98
VM/FC	4.2	1.2

Ultimate analysis (wt%)
C	14.83	27.05
H	1.26	0.82
N	0.40	0.33
S	0.29	0.82
O	27.91	9.73

Physical properties
Apparent density (g cm⁻³)	NM	0.52
S_BET (m² g⁻¹)	NM	209.12
V_p (cm³ g⁻¹)	NM	0.13
W₀ (cm³ g⁻¹)	NM	0.078
L (nm)	NM	1.30
D (nm)	NM	0.84

Note: Proximate analysis and ultimate analysis are presented on a dry basis (with the exception of the moisture content). Fixed carbon (proximate analysis) and oxygen (ultimate analysis) were calculated by difference. The following abbreviations have been used: Not measured (nm), surface area (S_BET), total pore volume (V_p), total micropore volume (W₀), average micropore width (L) and average pore diameter (D).

2.2

2.2 Chemicals and analytic methods

Diclofenac sodium (⩾99%), salicylic acid (⩾99%) and acetaminophen (⩾99%) were purchased from Sigma–Aldrich (Steinheim, Germany) while ibuprofen sodium (⩾98%) was purchased from Fluka. Main properties of these compounds are depicted in Table 2.

Table 2 Physico-chemical properties of the pharmaceuticals used in this study.

Pharmaceutical (formula)	M_w (g mol⁻¹)	S_w^a (mg L⁻¹)	pKa	log K_ow	PSA (A²)	HBAC
Diclofenac Sodium (C₁₄H₁₀Cl₂NNaO₂)	318.13	50,000	4	0.57	52.2	3
Salicylic acid (C₇H₆O₃)	138.12	2240	2.97	2.26	57.5	3
Ibuprofen Sodium (C₃H₁₇NaO₂)	228.26	100,000	4.91	3.8	40.1	2
Acetaminophen (C₈H₉NO₂)	151.17	14,000	9.48	0.46	49.3	2

Source: ChemSpider

PSA = Polar Surface Area.

HBAC = Hydrogen Bound Acceptor Count.

a S_w = water solubility (25 °C).

The target pharmaceuticals were analyzed by a Jasco HPLC apparatus equipped with a PU-980 pump, a detector UV–Vis Barspec, a phenomenex C18 column (5 μm, 110 Å, 250 × 4.6 mm), a Rheodyne injector and a 50 μL loop. The wavelengths of detection were 276.5, 220, 236 and 246 for diclofenac, ibuprofen, salicylic acid and acetaminophen, respectively. The mobile phase consisted of a mixture of acetonitrile:water:orthophosphoric acid (70:30:0.1, v/v/v) for the analysis of diclofenac and salicylic acid, a mixture of methanol:water:orthophosphoric acid (75:25:0.3) for the analysis of ibuprofen and a mixture of acetonitrile:water (30:70, v/v) for the analysis of acetaminophen. HPLC quality acetonitrile (CH₃CN) from LabScan, orthophosphoric acid (H₃PO₄) from Panreac and ultrapure water obtained by a Millipore System were used for the preparation of the mobile phase. Before use, each mixture was passed through a Millipore 0.45 μm pore size filter and degasified in an ultrasound bath during 30 min. For the chromatographic determination of concentration, four replicated injections were carried out under a mobile phase flow rate of 1 mL min⁻¹.

2.3

2.3 Wastewater from a municipal STP

Aiming the practical utilization of pyrolyzed primary pulp mill sludge in tertiary wastewater treatment, adsorption of pharmaceuticals from real wastewater was tested. Thus, for this work, the secondary effluent was collected from the STP of León (Spain). This secondary effluent is directly discharged at the Bernesga river, a tributary of the Esla river that is 77 km long and goes through the town of León. This STP consists of primary and secondary stage treatments. The primary stage comprises the following treatments: screening, sand removal, fat removal and primary clarification. Then, the secondary stage involves a plug-flow activated sludge with nitrification/denitrification followed by secondary clarification. The plant was designed to treat the wastewater of 330,000 equivalent inhabitants and has an inflow of 123,000 m³ day⁻¹ with a hydraulic retention time (HRT) of about 6 h.

Wastewater quality parameters, namely pH, conductivity, total suspended solids (TSS), biological oxygen demand at five days (BOD₅), chemical oxygen demand (DQO), NTK, N-NH₄, N-NO₃, N-NO₂, total P-PO₄, were determined by using Standard Methods (APHA-AWWA-WPCF, 2001). Obtained results are given in Table 3.

Table 3 Main properties of the STP secondary effluent used in this work.

Parameter
pH	7.6 ± 0.1
Conductivity (μS cm⁻¹)	612 ± 3
TSS (mg L⁻¹)	22 ± 1
BOD₅ (mg L⁻¹)	21 ± 2
COD (mg L⁻¹)	47 ± 3
NTK (mg L⁻¹)	17 ± 2
N-NH₄ (mg L⁻¹)	13.1 ± 0.4
N-NO₃ (mg L⁻¹)	1.7 ± 0.2
N-NO₂ (mg L⁻¹)	0.5 ± 0.1
Total P-PO₄ (mg L⁻¹)	1.8 ± 0.1

Note: Each ± stands for standard deviation of three analytical replications.

2.4

2.4 Adsorption experiments

Adsorption experiments were performed using a batch experimental approach. For each pharmaceutical, adsorption kinetic experiments were first carried out in order to determine the time necessary to attain equilibria (t_eq). Then equilibrium experiments were done to determine the corresponding adsorption isotherm. All experiments were carried out by shaking (250 rpm) a known mass of PS800-150 together with 100 mL of wastewater in 250 mL Erlenmeyer flasks. Initial concentration of each target pharmaceutical in wastewater was 100 ± 1 mg L⁻¹. All experiments were done in triplicate and at a constant temperature of 25 ± 2 °C by means of a thermostatically regulated incubator. Triplicate control experiments, with no adsorbent, were run in parallel with adsorption experiments in order to verify whether the concentration of the target pharmaceutical was stable throughout the duration of the experiments.

In the kinetic experiments, Erlenmeyer flasks were progressively withdrawn from the shaker after pre-set time intervals. Then, from each flask, three aliquots were taken, filtered and chromatographically analyzed to determine the concentration of the target pharmaceutical. The amount of each pharmaceutical adsorbed onto PS800-150 at each time, q_t (mg g⁻¹), was calculated by a mass balance relationship as follows:

(1)

q_{t} = (C_{0} - C_{t}) \frac{V}{W}

where C₀ (mg L⁻¹) is the initial liquid-phase concentration of pharmaceutical, C_t (mg L⁻¹) is the liquid-phase concentration of pharmaceutical at a time t (min), V is the volume of the solution (L) and W is the mass (g) of PS800-150.

For equilibrium experiments, Erlenmeyer flasks were shaken during 1000 min in order to guarantee the equilibrium, as inferred from kinetic results. Then, from each flask, three aliquots were taken, filtered and chromatographically analyzed to determine the equilibrium concentration (C_e, mg L⁻¹) of the target pharmaceutical. The amount of each pharmaceutical adsorbed onto PS800-150 at the equilibrium, q_e (mg g⁻¹) was calculated by the following mass balance relationship:

(2)

q_{e} = (C_{0} - C_{e}) \frac{V}{W}

For comparison purposes in terms of capacity, equilibrium experiments were also carried out following the same procedure but using ultrapure water as aqueous matrix.

2.5

2.5 Modeling of adsorption results

The experimental kinetic results were fitted with the pseudo first-order (Lagergren, 1898) and the pseudo second-order (Ho and McKay, 1999) equations. Both the pseudo-first order (Eq. (3)) and the pseudo-second order (Eq. (4)) are empirical rate equations based on the overall sorption rate:

(3)

q_{t} = q_{e} (1 - e^{- k_{1} t})

(4)

q_{t} = \frac{q_{e}^{2} k_{2} t}{1 + q_{e} k_{2} t}

where k₁ (min⁻¹) and k₂ (mg g⁻¹ min) are the pseudo-first and the pseudo-second order rate constants, respectively.

In order to describe the adsorption equilibrium results, different non-linear models were tried. First of all, fittings to the main two parameter isotherms, namely the Freundlich isotherm (Freundlich, 1906) and the Langmuir isotherm (Langmuir, 1918), which are described by Eqs. (5) and (6), were determined. Then, the Sips isotherm (Sips, 1948), which is a combined form of Langmuir and Freundlich and a three parameter model, as described by Eq. (7), was also tried.

(5)

q_{e} = K_{F} C_{e}^{1 / n}

(6)

q_{e} = \frac{Q_{m} K_{L} C_{e}}{1 + K_{L} C_{e}}

(7)

q_{e} = \frac{Q_{m} K_{LF} C_{e}^{1 / n}}{1 + K_{LF} C_{e}^{1 / n}}

where K_F is the Freundlich adsorption constant (mg g⁻¹ (mg L⁻¹)^−1/ⁿ); n is the degree of non-linearity; Q_m is the maximum adsorption capacity (mg g⁻¹); K_L (L mg⁻¹) and K_LF (mg g⁻¹ (mg L⁻¹)^−1/ⁿ) are the Langmuir and Langmuir–Freundlich affinity coefficients, respectively.

3 Results and discussion

The parameters analyzed on the secondary effluent used in this work (Table 3) showed typical values of a municipal STP effluent and accomplished with European regulations on the discharge of this sort of effluents (35 mg L⁻¹ TSS, 25 mg L⁻¹ BOD₅ and 125 mg L⁻¹ COD as established by the EU Council Directive 91/271/EEC).

The kinetic experimental data on the adsorption of diclofenac, ibuprofen, salicylic acid and acetaminophen from the secondary effluent of a STP and from ultrapure water are shown in Figs. 1 and 2, respectively, together with fittings to the pseudo-first order and the pseudo-second order kinetic equations. Parameters determined from these fittings are depicted in Table 4.

Kinetic results on the removal of (a) diclofenac, (b) salicylic acid, (c) ibuprofen, and (d) acetaminophen from a secondary effluent of a STP by adsorption onto PS800-150. Experimental results throughout time are shown together with the corresponding fittings to the pseudo-first and to the pseudo-second order kinetic equations. Note: error bars stand for standard deviation of three experimental replications.

Kinetic results on the removal of (a) diclofenac, (b) salicylic acid, (c) ibuprofen, and (d) acetaminophen from ultrapure water by adsorption onto PS800-150. Experimental results throughout time are shown together with the corresponding fittings to the pseudo-first and to the pseudo-second order kinetic equations. Note: error bars stand for standard deviation of three experimental replications.

Table 4 Kinetic parameters obtained from the fittings of experimental results on the adsorption of each pharmaceutical to the pseudo-first and to the pseudo-second order equations.

	Pharmaceuticals
	Diclofenac		Salicylic acid		Ibuprofen		Acetaminophen
	STP-SE	UP-W	STP-SE	UP-W	STP-SE	UP-W	STP-SE	UP-W
Pseudo-first order
k₁ (min⁻¹)	0.235 ± 0.130	0.153 ± 0.017	0.207 ± 0.038	0.129 ± 0.025	0.198 ± 0.033	0.138 ± 0.022	0.052 ± 0.005	0.061 ± 0.004
q_e (mg g⁻¹)	19.94 ± 0.02	22.77 ± 0.31	7.94 ± 0.15	8.01 ± 0.22	12.19 ± 0.19	12.68 ± 0.27	12.64 ± 0.31	12.53 ± 0.21
R²	0.9971	0.9883	0.9861	0.9712	0.9832	0.9720	0.9774	0.9883
S_xy	0.36	0.82	0.36	0.52	0.53	0.71	0.66	0.47

Pseudo-second order
k₂ (g mg⁻¹ min⁻¹)	0.042 ± 0.003	0.015 ± 0.000	0.063 ± 0.015	0.027 ± 0.005	0.038 ± 0.006	0.021 ± 0.003	0.006 ± 0.001	0.007 ± 0.001
q_e (mg g⁻¹)	20.30 ± 0.06	23.64 ± 0.05	8.13 ± 0.11	8.36 ± 0.15	12.60 ± 0.13	13.26 ± 0.16	13.50 ± 0.23	13.31 ± 0.17
R²	0.9996	0.9998	0.9944	0.9912	0.9956	0.9940	0.9914	0.9948
S_xy	0.13	0.11	0.23	0.29	0.27	0.33	0.41	0.31

Note: Each ± stands for standard deviation of three experimental replications.

As it may be seen in Fig. 1, under identical experimental conditions, when the equilibrium is reached, the adsorbed mass of each pharmaceutical on PS800-150 from the secondary effluent was different. Clearly, the drug showing the lowest adsorbed mass is salicylic acid. Furthermore, it is evident that the adsorption of acetaminophen is slower than that of the rest of drugs. Mostly, experimental results are better fitted by the pseudo-second order equation than by the first order one, which is confirmed by the R² and S_yx values in Table 4. The kinetic constant k₂ decreases from salicylic acid > diclofenac > ibuprofen > acetaminophen. Furthermore, the k₂ corresponding to the adsorption of acetaminophen is an order of magnitude lower than the k₂ determined for the adsorption of the other pharmaceuticals here considered. On the other hand, the fitted q_e for the adsorption of salicylic acid is an order of magnitude lower than for the rest of drugs.

Kinetic results on the adsorption of the considered pharmaceuticals from ultrapure water are given in Fig. 2. As for the adsorption from the secondary effluent, fittings to the pseudo-second order equation are better than those to the pseudo-first order one; salicylic acid was the one showing the lowest adsorbed equilibrium concentration (q_e), which was an order of magnitude lower than for the rest of pharmaceuticals; and the adsorption of acetaminophen was the slowest one with a k₂ an order of magnitude lower than for the rest of drugs. From ultrapure water, the kinetic constant k₂ also decreases from salicylic acid > diclofenac > ibuprofen > acetaminophen. When comparing the adsorption kinetics of each pharmaceutical from wastewater (Fig. 1) with its adsorption from ultrapure water (Fig. 2), differences are not especially relevant as confirmed by the pseudo-second order kinetic parameters in Table 4. Equilibrium was attained quite quickly from either the STP secondary effluent or ultrapure water, for all the pharmaceuticals equilibrium being attained within 200 min. In any case, under the experimental conditions here used, the kinetic constant k₂ was slightly higher (diclofenac, salicylic acid, ibuprofen) or equal (acetaminophen) for the adsorption from the secondary STP effluent than from ultrapure water. On the other hand, the adsorbed concentration in the equilibrium (q_e) was slightly higher (diclofenac, ibuprofen) or equivalent (salicylic acid, acetaminophen) from ultrapure than from the secondary STP effluent.

The equilibrium experimental data on the adsorption of diclofenac, ibuprofen, salicylic acid and acetaminophen from the secondary STP effluent and from ultrapure water are shown in Figs. 3 and 4, respectively, together with fittings to the isotherm models considered. Parameters determined from these fittings are depicted in Table 5.

Equilibrium results on the removal of (a) diclofenac, (b) salicylic acid, (c) ibuprofen, and (d) acetaminophen from a secondary effluent of a STP by adsorption onto PS800-150. Experimental results are shown together with fittings to the Freundlich, to the Langmuir and to the Sips isotherm models. Note: error bars stand for standard deviation of three experimental replications.

Equilibrium results on the removal of (a) diclofenac, (b) salicylic acid, (c) ibuprofen, and (d) acetaminophen from ultrapure water by adsorption onto PS800-150. Experimental results are shown together with fittings to the Freundlich, to the Langmuir and to the Sips isotherm models. Note: error bars stand for standard deviation of three experimental replications.

Table 5 Isotherm parameters obtained from the fittings of experimental results on the adsorption of each pharmaceutical from the secondary effluent of a STP (STP-SE) or from ultrapure water (UP-W).

	Pharmaceuticals
	Diclofenac		Salicylic acid		Ibuprofen		Acetaminophen
	STP-SE	UP-W	STP-SE	UP-W	STP-SE	UP-W	STP-SE	UP-W
Freundlich
K_F (mg g⁻¹ (mg L⁻¹)^−1/ⁿ)	3.07 ± 0.31	3.70 ± 0.36	0.50 ± 0.04	0.90 ± 0.05	2.55 ± 0.29	4.91 ± 0.29	2.86 ± 0.38	3.95 ± 0.31
n	2.32 ± 0.14	2.41 ± 1.40	1.62 ± 0.04	1.97 ± 0.05	2.76 ± 0.22	4.36 ± 0.31	2.73 ± 0.27	3.66 ± 0.28
R²	0.9744	0.9805	0.9949	0.9954	0.9617	0.9534	0.9438	0.9720
S_yx	1.10	1.18	0.19	0.17	0.731	0.77	1.07	0.73

Langmuir
Q_m (mg g⁻¹)	23.38 ± 1.28	26.69 ± 1.53	15.12 ± 1.06	12.08 ± 1.99	12.93 ± 0.45	12.66 ± 0.30	15.53 ± 0.71	12.33 ± 0.65
K_L (L mg⁻¹)	0.058 ± 0.009	0.060 ± 0.012	0.013 ± 0.002	0.025 ± 0.005	0.098 ± 0.014	0.359 ± 0.046	0.077 ± 0.012	0.265 ± 0.077
R²	0.9714	0.9643	0.9875	0.9622	0.9739	0.9580	0.9721	0.9303
S_yx	1.16	1.61	0.29	0.48	0.60	0.73	0.76	1.15

Sips
Q_m (mg g⁻¹)	34.84 ± 8.44	53.16 ± 22.62			16.05 ± 2.30	15.36 ± 1.05	16.79 ± 2.25	19.74 ± 4.55
K_LF (mg g⁻¹ (mg L⁻¹)^−1/ⁿ)	0.069 ± 0.012	0.062 ± 0.022			0.118 ± 0.017	0.372 ± 0.035	0.092 ± 0.021	0.230 ± 0.063
n	1.49 ± 0.21	1.77 ± 0.29			1.38 ± 0.22	1.69 ± 0.20	1.15 ± 0.21	2.15 ± 0.379
R²	0.9852	0.9845			0.9824	0.9851	0.9734	0.9846
S_yx	0.88	1.10			0.52	0.45	0.77	0.57

Note: Each ± stands for standard deviation of three experimental replications.

The equilibrium isotherms obtained for the adsorption of the pharmaceuticals from the STP effluent (Fig. 3) show some differences regarding the adsorption capacity and shape of isotherm. The adsorption capacity decreases from diclofenac > ibuprofen ≈ acetaminophen > salicylic acid. These capacity differences must be related to the drugs properties, among which S_w and log K_ow seem to have been especially determinant (Calisto et al., 2015). With respect to the isotherm, fittings to the Sips model are the most accurate for diclofenac, ibuprofen and acetaminophen. However, for salicylic acid, ambiguous fittings to the Sips isotherm were obtained, while both the Langmuir and, especially, the Freundlich isotherm models fitted experimental results. These observations are confirmed by parameters in Table 5, which make evident differences between the capacity and the isotherm model fittings.

As shown in Fig. 4, the adsorption equilibrium of pharmaceuticals from ultrapure water mostly resembles their adsorption from the STP secondary effluent. The equilibrium capacity also decreases from diclofenac > ibuprofen ≈ acetaminophen > salicylic acid and the Sips isotherm model is the one that better fits experimental results, except for salicylic acid. In this last case, the best fittings were obtained by the Freundlich isotherm model. Parameters in Table 5 support these remarks, as it may be seen by the Q_m and the R² and S_yx obtained for each pharmaceutical.

When comparing the equilibrium isotherms obtained for the adsorption of the considered pharmaceuticals from the STP secondary effluent and ultrapure water, differences are not outstanding. Focusing on the Sips isotherm model parameters (Table 5) for comparing the adsorption of diclofenac, ibuprofen and acetaminophen, several remarks may be made. First, considering the associated deviations, the Q_m values determined for the adsorption from the STP effluent and from ultrapure water are equivalent. In the case of the K_LF, which is usually related to the affinity of the adsorbent toward the adsorbate, each pharmaceutical showed a different pattern. Equal K_LF were determined for diclofenac while higher values were determined in ultrapure water than in the STP secondary effluent for ibuprofen and acetaminophen. Therefore, it may be inferred that the adsorption affinity for these last pharmaceuticals may be affected by the complex matrix of the STP effluent. Finally, the shape of the adsorption isotherms revealed a favorable process, with n > 1, which points to the fact that the adsorbents are efficient not only removing high but also low concentrations of these pharmaceuticals. In any case, higher n values were determined for the adsorption of these pharmaceuticals from ultrapure water than from the STP effluent. With respect to salicylic acid, the Freundlich isotherm parameters in Table 5 will be used for the comparison of its adsorption from the two different aqueous matrixes. In terms of adsorption affinity, a higher salicylic acid adsorption coefficient K_F was obtained for the adsorption from ultrapure water. In the case of n, it was larger than 1 either from ultrapure water or from the STP secondary effluent, but a larger value was determined for the adsorption from ultrapure water. Therefore, some matrix effects must have affected the salicylic acid adsorption from the STP effluent. In any case, as it was for the rest of the pharmaceuticals, the adsorption capacity remained the same from both ultrapure water and the STP secondary effluent, which is a key issue for the application of the charcoal here produced for an adsorptive tertiary treatment of wastewater.

Our results differ from those by Sotelo et al. (2012), who determined the adsorption isotherms of diclofenac and isoproturon using three carbonaceous materials (activated carbon, multiwalled carbon nanotubes and carbon nanofibers), found that the single adsorption capacity of these drugs was higher in ultrapure water than in real wastewater. Similarly, Kovalova et al. (2013) determined the adsorption isotherm and batch kinetic data using two powdered activated carbons to assess the removal of the pharmaceuticals 5-fluorouracil (5-Fu) and cytarabine (CytR) from ultrapure water and from a wastewater treatment plant effluent. These authors (Sotelo et al., 2012; Kovalova et al., 2013) found that the presence of organic matter in wastewater lowered the pharmaceuticals adsorption uptake. Using natural organic matter (NOM), Saravia and Frimmel (2008) showed that its presence slightly reduced the adsorption of pharmaceuticals, namely carbamazepine, clofibric, diclofenac, and iohexol on activated carbon. On the contrary, Méndez-Díaz et al. (2012) found that an increased adsorption capacity of phthalic acid (PA) from wastewater than from ultrapure water occurred onto two different activated carbons, which was attributed to the action of microorganisms in wastewater. In fact, Combarros et al. (2014) proved that the formation of bacterial biofilm on the surface of a commercial activated carbon increased the adsorptive removal of salicylic acid from water. In fact, it is possible that the synergetic microorganism action may have compensated the competitive effect of organic matter so that the removal capacity remains the same when using the produced charcoal for the removal of diclofenac, salicylic acid, ibuprofen and acetaminophen. It must be highlighted that, it was verified in this work that the pharmaceuticals concentration in controls (ultrapure or STP secondary effluent, in the absence of charcoal) remained constant throughout the duration of all the experiments.

Unfortunately, no other than the here referred works have been found in the literature on the comparative kinetics or isotherms in ultrapure and wastewater for the adsorption of pharmaceuticals. Therefore, it is not possible to further contrast our findings with results by other authors and with other adsorbent materials. From our point of view, this sort of study is essential for the application of any adsorbent in the tertiary treatment of wastewater.

4 Conclusions

A charcoal, obtained by the pyrolysis of primary pulp mill sludge, was proved to be able to adsorb diclofenac, salicylic acid, ibuprofen and acetaminophen either from ultrapure or from an STP secondary effluent. Adsorption equilibrium of these pharmaceuticals was attained within 200 min in all cases, the kinetics being described by the pseudo-second order equation. Both from ultrapure water and from the STP secondary effluent, the kinetic constant k₂ decreased from salicylic acid > diclofenac > ibuprofen > acetaminophen. Equilibrium results were appropriately described by the Sips isotherm model, except for salicylic acid, adsorption equilibrium of which was better described by the Freundlich isotherm. Both from ultrapure water and from the STP secondary effluent, the adsorption capacity decreased from diclofenac > ibuprofen ≈ acetaminophen > salicylic acid. For each of these pharmaceuticals, neither the removal velocity nor the capacity decreased when using the produced charcoal in a real wastewater matrix with respect to its utilization in ultrapure water. Competitive effects of substances present in wastewater may have been compensated by the synergetic removal of pharmaceuticals by microorganisms.

Acknowledgments

Vânia Calisto and Catarina I.A. Ferreira thank the Portuguese Science Foundation (FCT) for their postdoctoral (SFRH/BPD/78645/2011) and PhD grants (SFRH/BD/88965/2012), respectively. Marta Otero acknowledges financial support from the Spanish Ministry of Economy and Competitiveness, State Secretariat for Research, Development and Innovation (RYC-2010-05634). European Funds through COMPETE and by National Funds through the FCT within project PEst-C/MAR/LA0017/2013 are acknowledged. Authors also thank the kind collaboration of Eng Pedro Sarmento from RAIZ – Instituto de Investigação da Floresta e do Papel.

References

APHA-AWWA-WPCF, . Standard Methods for the Examination of Water and Wastewater (20th ed.). Washington DC, USA: American Public Health Association; 2001.
Bolong N., Ismail A.F., Salim M.R., Matsuurad T., . A review of the effects of emerging contaminants in wastewater and options for their removal. Desalination. 2009;239:229-246.
[Google Scholar]
Calisto V., Ferreira C.I.A., Santos S.M., Gil M.V., Otero M., Esteves V.I., . Production of adsorbents by pyrolysis of paper mill sludge and application on the removal of citalopram from water. Bioresource Technol.. 2014;166:335-344.
[Google Scholar]
Calisto V., Ferreira C.I.A., Oliveira J.A.B.P., Otero M., Esteves V.I., . Adsorptive removal of pharmaceuticals from water by commercial and waste-based carbons. J. Environ. Manage.. 2015;152:83-90.
[Google Scholar]
CEPI, 2013. Confederation of European Paper Industries (CEPI). CEPI’S Online Sustainability Report. <http://www.cepi-sustainability.eu/> (last accessed on the 15th of January 2015).
Combarros R.G., Rosas I., Lavín A.G., Rendueles M., Díaz M., . Influence of biofilm on activated carbon on the adsorption and biodegradation of salicylic acid in wastewater. Water Air Soil Poll.. 2014;225:1858-1869.
[Google Scholar]
Domínguez J.R., González T., Palo P., Cuerda-Correa E., . Removal of common pharmaceuticals present in surface waters by Amberlite XAD-7 acrylic-ester-resin: influence of pH and presence of other drugs. Desalination. 2011;269:231-238.
[Google Scholar]
Elliott A., Mahmood T., . Survey benchmarks generation, management of solid residues. Pulp Pap.. 2005;79:49-55.
[Google Scholar]
Farré M., Pérez S., Kantiani L., Barceló D., . Fate and toxicity of emerging pollutants, their metabolites and transformation products in the aquatic environment. Trends Anal. Chem.. 2008;27:991-1007.
[Google Scholar]
Freundlich H., . Über die adsorption in Lösungen. Z. Phys. Chem.. 1906;57:385-470.
[Google Scholar]
Ho I.S., McKay G., . Pseudo-second order model for sorption processes. Process Biochem.. 1999;34:451-465.
[Google Scholar]
Ince, B.K., Cetecioglu, Z., Ince, O., 2011. Pollution Prevention in the Pulp and Paper Industries, Environmental Management in Practice, Dr. Elzbieta Broniewicz (Ed.), ISBN: 978-953-307-358-3, InTech, DOI: 10.5772/23709. <http://www.intechopen.com/books/environmental-management-in-practice/pollution-prevention-in-the-pulp-and-paper-industries> (last accessed on the 19th of November 2015).
Kovalova L., Knappe D.R.U., Lehnberg K., Kazner C., Hollender J., . Removal of highly polar micropollutants from wastewater by powder activated carbon. Environ. Sci. Poll. Res.. 2013;20:3607-3615.
[Google Scholar]
Lagergren S., . Zur theorie der sogenannten adsorption gelöster stoffe. Kungliga Svenska Vetenskapsakademiens. Handlingar. 1898;24:1-39.
[Google Scholar]
Langmuir I., . The adsorption of gases on plane surfaces of glass, mica and platinum. J. Am. Chem. Soc.. 1918;40:1361-1403.
[Google Scholar]
Méndez A., Fidalgo J.M., Guerrero F., Gascó G., . Characterization and pyrolysis behaviour of different paper mill waste materials. J. Anal. Appl. Pyrol.. 2009;86:66-73.
[Google Scholar]
Méndez-Díaz J.D., Abdel daiem M.M., Rivera-Utrilla J., Sánchez-Polo M., Bautista-Toledo I., . Adsorption/bioadsorption of phthalic acid, an organic micropollutant present in landfill leachates, on activated carbons. J. Colloid Interface Sci.. 2012;369:358-365.
[Google Scholar]
Monte M.C., Fuente E., Blanco A., Negro C., . Waste management from pulp and paper production in the European Union. Waste Manage.. 2009;29:293-308.
[Google Scholar]
Pokhrel D., Viraraghavan T., . Treatment of pulp and paper mill wastewater- a review. Sci. Total Environ.. 2004;333:37-58.
[Google Scholar]
Priac A., Morin-Crini N., Druart C., Gavoille S., Bradu C., Lagarrigue C., Torri G., Winterton P., Crini G., . Alkylphenol and alkylphenol polyethoxylates in water and wastewater: a review of options for their elimination. Arab. J. Chem. 2014
[CrossRef] [Google Scholar]
Ridout A.J., Carrier M., Görgens J., . Fast pyrolysis of low and high ash paper waste sludge: influence of reactor temperature and pellet size. J. Anal. Appl. Pyrol.. 2015;111:64-75.
[Google Scholar]
Santos L.H.M.L.M., Araujo A.N., Fachinia A., Pena A., Delerue-Matos C., Montenegro M.C.B.S.M., . Review. Ecotoxicological aspects related to the presence of pharmaceuticals in the aquatic environment. J. Hazard Mater.. 2010;175:45-95.
[Google Scholar]
Saravia F., Frimmel F.H., . Role of NOM in the performance of adsorption-membrane hybrid systems applied for the removal of pharmaceuticals. Desalination. 2008;224:168-171.
[Google Scholar]
Sips R., . Combined form of Langmuir and Freundlich equations. J. Chem. Phys.. 1948;16:490-495.
[Google Scholar]
Sotelo J.L., Rodríguez A.R., Mateos M.M., Hernández S.D., Torrellas S.A., Rodríguez J.G., . Adsorption of pharmaceutical compounds and an endocrine disruptor from aqueous solutions by carbon materials. J. Environ. Sci. Health – Part B. Pestic. Food Contam. Agric. Wastes. 2012;47:640-652.
[Google Scholar]
Yang Y., Brammer J.G., Ouadi M., Samanya J., Hornung A., Xu H.M., Li Y., . Characterisation of waste derived intermediate pyrolysis oils for use as diesel engine fuels. Fuel. 2013;103:247-257.
[Google Scholar]

Introduction

Materials and methods

Adsorbent materials
Chemicals and analytic methods
Wastewater from a municipal STP
Adsorption experiments
Modeling of adsorption results

Results and discussion

Conclusions

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[1] APHA-AWWA-WPCF, . Standard Methods for the Examination of Water and Wastewater (20th ed.). Washington DC, USA: American Public Health Association; 2001.

[2] Bolong N., Ismail A.F., Salim M.R., Matsuurad T., . A review of the effects of emerging contaminants in wastewater and options for their removal. Desalination. 2009;239:229-246.
[Google Scholar]

[3] Calisto V., Ferreira C.I.A., Santos S.M., Gil M.V., Otero M., Esteves V.I., . Production of adsorbents by pyrolysis of paper mill sludge and application on the removal of citalopram from water. Bioresource Technol.. 2014;166:335-344.
[Google Scholar]

[4] Calisto V., Ferreira C.I.A., Oliveira J.A.B.P., Otero M., Esteves V.I., . Adsorptive removal of pharmaceuticals from water by commercial and waste-based carbons. J. Environ. Manage.. 2015;152:83-90.
[Google Scholar]

[5] CEPI, 2013. Confederation of European Paper Industries (CEPI). CEPI’S Online Sustainability Report. <http://www.cepi-sustainability.eu/> (last accessed on the 15th of January 2015).

[6] Combarros R.G., Rosas I., Lavín A.G., Rendueles M., Díaz M., . Influence of biofilm on activated carbon on the adsorption and biodegradation of salicylic acid in wastewater. Water Air Soil Poll.. 2014;225:1858-1869.
[Google Scholar]

[7] Domínguez J.R., González T., Palo P., Cuerda-Correa E., . Removal of common pharmaceuticals present in surface waters by Amberlite XAD-7 acrylic-ester-resin: influence of pH and presence of other drugs. Desalination. 2011;269:231-238.
[Google Scholar]

[8] Elliott A., Mahmood T., . Survey benchmarks generation, management of solid residues. Pulp Pap.. 2005;79:49-55.
[Google Scholar]

[9] Farré M., Pérez S., Kantiani L., Barceló D., . Fate and toxicity of emerging pollutants, their metabolites and transformation products in the aquatic environment. Trends Anal. Chem.. 2008;27:991-1007.
[Google Scholar]

[10] Freundlich H., . Über die adsorption in Lösungen. Z. Phys. Chem.. 1906;57:385-470.
[Google Scholar]

[11] Ho I.S., McKay G., . Pseudo-second order model for sorption processes. Process Biochem.. 1999;34:451-465.
[Google Scholar]

[12] Ince, B.K., Cetecioglu, Z., Ince, O., 2011. Pollution Prevention in the Pulp and Paper Industries, Environmental Management in Practice, Dr. Elzbieta Broniewicz (Ed.), ISBN: 978-953-307-358-3, InTech, DOI: 10.5772/23709. <http://www.intechopen.com/books/environmental-management-in-practice/pollution-prevention-in-the-pulp-and-paper-industries> (last accessed on the 19th of November 2015).

[13] Kovalova L., Knappe D.R.U., Lehnberg K., Kazner C., Hollender J., . Removal of highly polar micropollutants from wastewater by powder activated carbon. Environ. Sci. Poll. Res.. 2013;20:3607-3615.
[Google Scholar]

[14] Lagergren S., . Zur theorie der sogenannten adsorption gelöster stoffe. Kungliga Svenska Vetenskapsakademiens. Handlingar. 1898;24:1-39.
[Google Scholar]

[15] Langmuir I., . The adsorption of gases on plane surfaces of glass, mica and platinum. J. Am. Chem. Soc.. 1918;40:1361-1403.
[Google Scholar]

[16] Méndez A., Fidalgo J.M., Guerrero F., Gascó G., . Characterization and pyrolysis behaviour of different paper mill waste materials. J. Anal. Appl. Pyrol.. 2009;86:66-73.
[Google Scholar]

[17] Méndez-Díaz J.D., Abdel daiem M.M., Rivera-Utrilla J., Sánchez-Polo M., Bautista-Toledo I., . Adsorption/bioadsorption of phthalic acid, an organic micropollutant present in landfill leachates, on activated carbons. J. Colloid Interface Sci.. 2012;369:358-365.
[Google Scholar]

[18] Monte M.C., Fuente E., Blanco A., Negro C., . Waste management from pulp and paper production in the European Union. Waste Manage.. 2009;29:293-308.
[Google Scholar]

[19] Pokhrel D., Viraraghavan T., . Treatment of pulp and paper mill wastewater- a review. Sci. Total Environ.. 2004;333:37-58.
[Google Scholar]

[20] Priac A., Morin-Crini N., Druart C., Gavoille S., Bradu C., Lagarrigue C., Torri G., Winterton P., Crini G., . Alkylphenol and alkylphenol polyethoxylates in water and wastewater: a review of options for their elimination. Arab. J. Chem. 2014
[CrossRef] [Google Scholar]

[21] Ridout A.J., Carrier M., Görgens J., . Fast pyrolysis of low and high ash paper waste sludge: influence of reactor temperature and pellet size. J. Anal. Appl. Pyrol.. 2015;111:64-75.
[Google Scholar]

[22] Santos L.H.M.L.M., Araujo A.N., Fachinia A., Pena A., Delerue-Matos C., Montenegro M.C.B.S.M., . Review. Ecotoxicological aspects related to the presence of pharmaceuticals in the aquatic environment. J. Hazard Mater.. 2010;175:45-95.
[Google Scholar]

[23] Saravia F., Frimmel F.H., . Role of NOM in the performance of adsorption-membrane hybrid systems applied for the removal of pharmaceuticals. Desalination. 2008;224:168-171.
[Google Scholar]

[24] Sips R., . Combined form of Langmuir and Freundlich equations. J. Chem. Phys.. 1948;16:490-495.
[Google Scholar]

[25] Sotelo J.L., Rodríguez A.R., Mateos M.M., Hernández S.D., Torrellas S.A., Rodríguez J.G., . Adsorption of pharmaceutical compounds and an endocrine disruptor from aqueous solutions by carbon materials. J. Environ. Sci. Health – Part B. Pestic. Food Contam. Agric. Wastes. 2012;47:640-652.
[Google Scholar]

[26] Yang Y., Brammer J.G., Ouadi M., Samanya J., Hornung A., Xu H.M., Li Y., . Characterisation of waste derived intermediate pyrolysis oils for use as diesel engine fuels. Fuel. 2013;103:247-257.
[Google Scholar]

Removal of pharmaceuticals from municipal wastewater by adsorption onto pyrolyzed pulp mill sludge

Abstract

Keywords

Paper sludge

Pyrolysis

Wastewater treatment

Emerging contaminants

Pain reliever

Sorption

1 Introduction

2 Materials and methods

2.1 Adsorbent materials

2.2 Chemicals and analytic methods

2.3 Wastewater from a municipal STP

2.4 Adsorption experiments

2.5 Modeling of adsorption results

3 Results and discussion

4 Conclusions

Acknowledgments

References

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