Unary adsorption of sulfonamide antibiotics onto pozzolan-tyre ash based geopolymers: Isotherms, kinetics and mechanisms

• Published in: Chemical engineering research & design Vol. 206; pp. 440 - 452
• Main Authors: Tamaguelon, Hermann Dzoujo, Shikuku, Victor Odhiambo, Tome, Sylvain, Titini, Fidele Gallo, Ondiek, Pamela, Strothmann, Till, Getenga, Zachary, Janiak, Christoph, Etoh, Marie Annie, Dina, David Daniel Joh
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.06.2024
• Subjects: Adsorption; Geopolymers; Pozzolan; Sulfadimethoxine; Sulfamethoxazole; Tyre ash; Tyre ash; Sulfamethoxazole; Adsorption; Geopolymers; Pozzolan; Sulfadimethoxine
• ISSN: 0263-8762
• DOI: 10.1016/j.cherd.2024.05.009

In this contribution, geopolymer composites, GP0, GP5-TA and GP10-TA, were prepared by alkaline activation and substituting pozzolan (Pz) with 0, 5 and 10 wt% of tyre ash (TA), respectively. The geopolymers were characterized using standard methods (XRD, TGA, FTIR, BET, SEM, Boehm titration and methylene blue and iodine indices) and were applied for the abatement of two sulfonamides, sulfamethoxazole (SMX) and sulfadimethoxine (SDM) in single-solute solutions. The effects of pH, salinity, initial concentration and contact time were evaluated. The incorporation of 5 and 10% TA increased the specific surface area (SSA) of pristine geopolymer (GP0) from 13.62 to 21.48 and 29.70 m2.g−1, respectively. The equilibrium data was best described by the Sips isotherm model. Salinity significantly diminished the adsorption of SMX and SDM. In aqueous medium, the geopolymers exhibited higher adsorption capacity for SDM (log Kow, 1.17) relative to SMX (log Kow, 0.86). In contrast, in saline medium, SMX uptake was higher, suggesting a cation-mediated adsorption. Adsorption of SMX was uncharacteristically independent of pH, whereas SDM uptake was significantly pH-dependent. The GP5-TA geopolymer composite exhibited the highest adsorption capacity for SMX in a saline environment (46.69 mg.g−1) and for SDM in non-saline water (107.69 mg.g−1). Adsorption rate was described by the pseudo-second order kinetic law. Adsorption mechanism was multi-mechanistic involving hydrophobic, ion exchange and charge assisted hydrogen bonding and electrostatic interactions in the case of SDM. Future works should optimize the functional groups density of active sites especially for sulfonamides in saline waters. •Incorporating TA increased specific surface area and acidic functional groups.•Salinity diminished the adsorption of the antibiotics.•Sips model best predicted the equilibrium adsorption capacity.•Adsorption of SMX was independent of pH.•Adsorption mechanism was multi-mechanistic.