Abstract
ABSTRACT Pharmaceuticals as an increasing water contaminant pose major hazards to water quality and human health. Hydroxyapatite (HAp) has shown promise in the treatment of many contaminants, although it could be improved. The adsorption capacity of silver and titanium dioxide nanoparticles doped calcined HAp (AgNPs-TiO2NPs@calcined HAp) for acetaminophen (ACT) and Ibuprofen (IBP) was investigated in this study. Fourier Transform Infra-Red (FTIR) spectroscopy, scanning electron microscopy-energy dispersive X-ray (SEM-EDX), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) were used to characterise the AgNPs-TiO2NPs@calcined HAp. Both AgNPs and TiO2NPs absorbed maximally at 376 and 366 nm, respectively. The FTIR of AgNPs-TiO2NPs@calcined HAp revealed FTIR peaks at 1425, 925 and 590 cm−1 corresponding CO3 2- and PO4 3- characteristics of HAp, with XRD pattern revealing crystalline hexagonal-shaped HAp having a particle size of 31.72 ± 10.19 nm. The BET surface area and pore volume increased with doping to 446.11 ± 6.30 m2g−1 and 0.0167 ± 0.0024 cm3g−1, respectively while pore radius reduced slightly to 3.12 ± 0.08 Å indicating a microporous structure of the adsorbent. The surface of AgNPs-TiO2NPs@calcined HAp favoured adsorption of IBP and ACT at pH 2 and 9, respectively. Adsorption data of both drugs best fitted pseudo-second-order kinetics with equilibrium established at 50 and 60 min for ACT and IBP respectively. The adsorption ACT and IBP on AgNPs-TiO2NPs@calcined HAp followed an S-shaped pattern, with Langmuir and Freundlich isotherms best-representing removal of ACT and IBP, respectively. The adsorption capacities ( ranged from 20.72 to 76.92 mgg−1 for ACT and 114.97 to 188.00 mgg−1 for IBP. The adsorption process was exothermic (-ΔH) and spontaneous (-ΔG) with a decreased degree of randomness (-ΔS). The adsorption mechanism was physisorption for ACT and alternated between physisorption and chemisorption for IBP. The adsorptive performance of AgNPs-TiO2NPs@calcined HAp for ACT and IBP removal implies it is a better adsorbent than most previously reported in the literature.
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