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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 36.5MJkg 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 pyrol- ysis 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 (Me´ ndez et al., 2009) and pharmaceuticals (Calisto et al., 2014) from water. Traditionally, pharmaceuticals were not considered as environmen- tal 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 environ- ment 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 (Farre´ et al., 2008). Actually, STPs were conceived to reduce the concentra- tion 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 transforma- tion 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 (Domı´ nguez 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, sal- icylic acid and acetaminophen. These pharmaceuticals belong to the anti-inflammatory and/or analgesic groups and among the most com- monly used of all medications in the world and, consequently, also among the most frequently found drugs in STP effluents and natural waters.
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 dry- ing at 60 C, blade milled and pyrolyzed in a Nu¨ ve muffle (MF 106, Turkey). The pyrolysis was carried out at 800 CunderN 2 saturated atmosphere (N 2 flow of 0.5 dm 3 min 1 ) during 150 min. The pyrolysis of PS to obtain PS800-150 was meticu- lously 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, 13 C and 1 H solid state NMR and SEM analysis may be found elsewhere (Calisto et al., 2014).
2.2. Chemicals and analytic methods
Diclofenac sodium ( P 99%), salicylic acid ( P 99%) and aceta- minophen ( P 99%) were purchased from Sigma–Aldrich (Steinheim, Germany) while ibuprofen sodium ( P 98%) was purchased from Fluka. Main properties of these compounds are depicted in Table 2. 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 l m, 110A˚ , 250 4.6 mm), a Rheodyne injector and a 50 l L loop. The wavelengths of detection were 276.5, 220, 236 and 246 for diclofenac, ibuprofen, salicylic acid and acetaminophen,
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 36.09
61.25 20.77 17.98
Volatile Matter (VM) Fixed Carbon (FC)
8.60
VM/FC
4.2
1.2
Ultimate analysis (wt%) C
14.83
27.05
H N
1.26 0.40 0.29
0.82 0.33 0.82 9.73
S
O
27.91
Physical properties Apparent density (g cm 3 )
NM NM NM NM NM NM
0.52
2 g 1 )
S BET (m V p (cm W 0 (cm L (nm) D (nm)
209.12
3 g 1 )
0.13
3 g 1 )
0.078
1.30 0.84
2. Materials and methods
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 ( W 0 ), average micropore width ( L ) and average pore diameter ( D ).
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
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