Abstract
Carbon nanodots (CNDs)-embedded pullulan (PUL) nanofibers were developed and successfully applied for sulfathiazole (STZ) removal from wastewater streams for the first time. The CNDs were incorporated into PUL at 0.0%, 1.0%, 2.0%, and 3.0% (w/w) to produce M1, M2, M3, and M4 nanofibers (PUL-NFs), respectively. The produced PUL-NFs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), thermal gravimetric analysis (TGA) and Differential scanning calorimetry (DSC) and applied for STZ removal from aqueous solutions through pH, kinetics, and equilibrium batch sorption trials. A pH range of 4.0–6.0 was observed to be optimal for maximum STZ removal. Pseudo-second order, intraparticle diffusion, and Elovich models were suitably fitted to kinetics adsorption data (R2 = 0.82–0.99), whereas Dubinin–Radushkevich, Freundlich, and Langmuir isotherms were fitted to equilibrium adsorption data (R2 = 0.88–0.99). STZ adsorption capacity of PUL-NFs improved as the amount of embedded CNDs increased. Maximum STZ adsorption capacities of the synthesized PUL-NFs were in the order of: M4 > M3 > M2 > M1 (133.68, 124.27, 93.09, and 35.04 mg g−1, respectively). Lewis acid–base reaction and π-π electron donor–acceptor interactions were the key STZ removal mechanisms under an acidic environment, whereas H-bonding and diffusion were key under a basic environment. Therefore, CNDs-embedded PUL-NFs could be employed as an environmentally friendly, efficient, and non-toxic adsorbent to remove STZ from wastewater streams.
Highlights
Introduction30% of antibiotics are metabolized and absorbed in the targeted organism of the body and the remaining active compounds are excreted as microcontaminants in soil and water ecosystems
The pharmaceutical industry has developed over 250 essential antibiotics for better public health and life quality with an annual consumption of more than 63 tons [1,2].30% of antibiotics are metabolized and absorbed in the targeted organism of the body and the remaining active compounds are excreted as microcontaminants in soil and water ecosystems
To avoid further agglomeration of carbon nanodots (CNDs) in the PUL NFs, no more (>3%) CNDs were added in the PUL solution
Summary
30% of antibiotics are metabolized and absorbed in the targeted organism of the body and the remaining active compounds are excreted as microcontaminants in soil and water ecosystems. This huge amount of excreted antibiotics, released mainly from the wastewater discharge of hospitals, veterinary farms, and municipal effluents [3], are introduced into surface and drinking water [4,5]. Sulfathiazole (STZ) is one of the commonly used topical antimicrobials, with short-acting sulfonamide antibiotics, generally used in vaginal and urinary tract infections. The structure of STZ (C9 H9 N3 O2 S2 ) contains a Membranes 2022, 12, 228 vaginal and urinary tract infections. The structure of STZ (C9H9N3O2S2) contains a heterocyclic (1,3-thiazole) compound with awith
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