Abstract
A waste-based alternative activated carbon (AAC) was produced from paper mill sludge under optimized conditions. Aiming its application in tertiary wastewater treatment, AAC was used for the removal of carbamazepine, sulfamethoxazole, and paroxetine from biologically treated municipal wastewater. Kinetic and equilibrium adsorption experiments were run under batch operation conditions. For comparison purposes, they were also performed in ultrapure water and using a high-performance commercial AC (CAC). Adsorption kinetics was fast for the three pharmaceuticals and similar onto AAC and CAC in either wastewater or ultrapure water. However, matrix effects were observed in the equilibrium results, being more remarkable for AAC. These effects were evidenced by Langmuir maximum adsorption capacities (qm, mgg-1): for AAC, the lowest and highest qm were 194 ± 10 (SMX) and 287 ± 9 (PAR), in ultrapure water, and 47 ± 1 (SMX) and 407 ± 14 (PAR), in wastewater, while for CAC, the lowest and highest qm were 118 ± 7 (SMX) and 190 ± 16 (PAR) in ultrapure water and 123 ± 5 (SMX) and 160 ± 7 (CBZ) in wastewater. It was found that the matrix pH played a key role in these differences by controlling the surface electrostatic interactions between pharmaceutical and AC. Overall, it was evidenced the need of adsorption results in real matrices and demonstrated that AAC is a promising option to be implemented in tertiary wastewater treatments for pharmaceuticals' removal. Graphical abstract Production of an alternative activated carbon (AC) comparing favourably with a commercial AC in the removal of neutral and positive pharmaceuticals from wastewater.
Highlights
In the European Union, from the 2.3 billion tonnes of waste that are produced annually, 10% include municipal waste and 90% industrial, agricultural and commercial-related wastes (Grace et al, 2016)
commercial activated carbons (AC) (CAC) presented a pHpzc of ~7, while the pHpzc of ~5 determined for activated carbon (AAC) indicated that it presented an acidic surface, which was confirmed by the determination of the acidic oxygen-containing functional groups by the Boehm’s titrations
From the scanning electron microscopy (SEM) images, it was observed that the AAC presented a high level of porosity, with an irregular surface and a well-defined presence of porous (Jaria et al, 2018); CAC presented some degree of porosity, but, for the same magnification, less roughness was observed in comparison with the AAC
Summary
In the European Union, from the 2.3 billion tonnes of waste that are produced annually, 10% include municipal waste and 90% industrial, agricultural and commercial-related wastes (Grace et al, 2016). Different wastes have been used as raw materials and subjected to diverse procedures aiming the production of alternative adsorbents for the removal of pharmaceuticals from water A full factorial design was carried out to determine the most favourable route to produce a powdered alternative activated carbon (AAC) with improved and promising properties (a high specific surface area (SBET) of 1627 m2 g-1 and very good responses in terms of adsorption percentage for pharmaceuticals of different classes). The present work aimed at assessing the practical utilization of the previously optimized powdered AAC in the tertiary treatment of wastewater for the removal of pharmaceuticals frequently found in aquatic environments, from different pharmacological classes and with distinct physico-chemical properties. The adsorption kinetics, equilibrium isotherms and adsorption capacity of AAC and CAC towards carbamazepine (CBZ), sulfamethoxazole (SMX) and paroxetine (PAR) from biologically treated wastewater were determined
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