Abstract
In this work, a granular activated carbon (GAC) was produced using primary paper mill sludge (PS) as raw material and ammonium lignosulfonate (AL) as binder agent. PS is a residue from the pulp and paper industry and AL is a by-product of the cellulose pulp manufacture and the proposed production scheme contributes for their valorisation together with important savings in GAC precursors. The produced GAC (named PSA-PA) and a commercially available GAC (GACN), used as reference material, were physically and chemically characterized. Then, these materials were tested in batch experiments for the adsorption of carbamazepine (CBZ), sulfamethoxazole (SMX), and paroxetine (PAR) from ultra-pure water and wastewater. Even though GACN and PSA-PA possess very similar specific surface areas (SBET) (629 and 671 m2 g−1, respectively), PSA-PA displayed lower maximum adsorption capacities (qm) than GACN for the pharmaceuticals here studied (6 ± 1–44 ± 5 mg g−1 and 49 ± 6–106 ± 40 mg g−1, respectively). This may be related to the comparatively higher incidence of mesopores in GACN, which might have positively influenced its adsorptive performance. Moreover, the highest hydrophobic character and degree of aromaticity of GACN could also have contributed to its adsorption capacity. On the other hand, the performance of both GACs was significantly affected by the matrix in the case of CBZ and SMX, with lower qm in wastewater than in ultra-pure water. However, the adsorption of PAR was not affected by the matrix. Electrostatic interactions and pH effects might also have influenced the adsorption of the pharmaceutical compounds in wastewater.
Highlights
Activated carbons (ACs) are carbonaceous materials with high adsorption capacity towards a vast number of organic and inorganic compounds, such as pharmaceuticals, pesticides, personal care products, dyes and metals (Rodriguez-Narvaez et al, 2017).Commercial ACs, which are commonly produced from wood or coal, are available in powdered (PAC) or granular (GAC) formulations (Bandosz, 2006)
PSA-PA and GACN present a high value of total organic carbon (TOC), 72 ± 2% and 79.7 ± 0.8%, respectively, and a very low value of inorganic carbon (IC), 0.029 ± 0.003% and 0.0204 ± 0.0002%, respectively
The H/C ratio indicates that GACN possesses a higher degree of aromaticity than PSA-PA
Summary
Activated carbons (ACs) are carbonaceous materials with high adsorption capacity towards a vast number of organic and inorganic compounds, such as pharmaceuticals, pesticides, personal care products, dyes and metals (Rodriguez-Narvaez et al, 2017).Commercial ACs, which are commonly produced from wood or coal (bituminous and subbituminous varieties), are available in powdered (PAC) or granular (GAC) formulations (Bandosz, 2006). GAC and PAC are used in water treatment, both presenting advantageous features and drawbacks depending on specific applications. PAC has the main advantage of, generally, possessing higher specific surface area (SBET); it is usually applied in batch mode (due to inadequate particle size to be used in fixed-bed columns and difficult separation from the treated water in continuously stirred reactors). Wang and Wang, 2016; Yang et al, 2017) Both PAC and GAC possess a great potential for the adsorption of these contaminants; yet, the use of PAC in wastewater treatment is usually associated to increased implementation and application costs and so GAC is generally the preferred option (Yang et al, 2017)
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