Integration of magnetic graphene oxide and office waste paper-derived fibrillated cellulose into a composite adsorbent for effective tetracycline elimination

Abstract

Utilizing office waste paper for environmental treatments has garnered significant interest from the research community, as it addresses both waste management and the development of low-cost sustainable adsorbents. In this study, a novel approach was developed by integrating office waste paper-derived fibrillated cellulose (PFC) with magnetic graphene oxide (M-GO) to develop a composite adsorbent for the removal of tetracycline (TC) from aqueous solutions. PFC was isolated via an alkali-acid treatment process; graphene oxide (GO) was synthesized using a modified Hummers' method and subsequently functionalized with magnetite nanoparticles to produce M-GO. The M-GO/PFC composite was then prepared using an ultrasound-assisted mixing technique, followed by lyophilization. Materials were characterized using Fourier-transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray (EDX) spectroscopy, N₂ adsorption-desorption isotherms, and vibrating sample magnetometry (VSM). The effects of solution pH, adsorbent dose, and ionic strength on TC removal by the composite adsorbent were systematically investigated. Adsorption kinetics was analyzed using the pseudo-first-order, pseudo-second-order, and Elovich models, suggested to fit well with the pseudo-second-order kinetic model with an initial rate of 18.09 mg g^-1 min^-1. Adsorption isotherms were evaluated using the Langmuir, Freundlich, Sips, and Temkin models, of which the Sips model best described the experimental data, yielding a maximum adsorption capacity of 130.11 mg g^-1. Recyclability testing was carried out through five successive adsorption-desorption cycles, indicating a stable adsorption performance of the composite adsorbent with 12.9% decrease between the first and the fifth cycle. These findings suggest that the M-GO/PFC composite is a promising and effective adsorbent for the removal of TC and potentially other water-soluble antibiotics from aqueous environments.

Fig. 1. FTIR spectra of (a) Gi, (b) GO, (c) Fe₃O₄, (d) PFC, (e) M-GO/PFC composite, and (f) M-GO/PFC composite after the TC adsorption.

Fig. 2. XRD patterns of (a) Gi, (b) GO, (c) Fe₃O₄, (d) PFC, and (e) M-GO/PFC composite.

Fig. 3. Raman spectra of (a) Gi, (b) GO, (c) PFC, and (d) M-GO/PFC composite.

Fig. 4. FE-SEM surface images of (a) GO, (c) PFC, (e) Fe₃O₄, and (f) M-GO/PFC composite; FE-SEM cross-section images of (b) GO and (d) PFC; (g) average PFC diameter distribution.

Fig. 5. Elemental maps of (a) C, (b) O, (c) Fe, and (d) M-GO/PFC composite; (e) EDX spectrum of M-GO/PFC composite.

Fig. 6. Magnetization hysteresis curves of Fe₃O₄ and M-GO/PFC composite.

Fig. 7. (a) Effect of solution pH on the TC adsorption capacity, and (b) the pH_pzc of M-GO/PFC composite adsorbent.

Fig. 8. Effect of adsorbent dose on the TC adsorption capacity.

Fig. 9. Effect of ionic strength on the TC adsorption capacity.

Fig. 10. Adsorption kinetic models for the TC adsorption onto the M-GO/PFC composite adsorbent.

Fig. 11. Adsorption isotherm models for the TC adsorption onto the M-GO/PFC composite adsorbent.

Fig. 12. Recyclability study of M-CO/PFC composite adsorbent.

Fig. 13. XPS of (a) survey spectrum, (b) C 1s, and (c) O 1s of M-GO/PFC composite before the TC adsorption; XPS of (d) survey spectrum, (e) C 1s, (f) O 1s, (g) Fe 2p, and (h) N 1s of M-GO/PFC composite after the TC adsorption.

Fig. 14. Proposed mechanism for the TC adsorption onto the M-GO/PFC composite adsorbent.