Fabrication of magnetic nickel incorporated carbon nanofibers for superfast adsorption of sulfadiazine: Performance and mechanisms exploration

https://doi.org/10.1016/j.jhazmat.2021.127219Get rights and content

Highlights

  • Magnetic nickel incorporated carbon nanofibers (Ni@CNF) were successfully fabricated.

  • The adsorption behaviors of SDZ on Ni@CNF were theoretically and experimentally studied.

  • Ni@CNF achieved adsorption capacity of 103.21 mg/g toward SDZ.

  • XPS and DFT calculations demonstrated that Ni atoms were active adsorption sites for SDZ removal.

Abstract

Herein, novel magnetic nickel incorporated carbon nanofibers (Ni@CNF) were successfully synthesized via electrostatic spinning method for sulfadiazine (SDZ) adsorption. We combined computational and experimental tools to clarify the distinct nature of SDZ on Ni@CNF. Extensive computations and characterizations of SDZ-Ni adsorption complexes evidenced that Ni atoms were indispensable for SDZ adsorption and increasing the number of Ni atoms in Ni@CNF significantly improved SDZ adsorption due to the lower adsorption energy (Ead). As we surmised, the adsorption capacity of Ni@CNF enhanced gradually with increasing the mass ratio of Ni in the composite. The as-prepared 9%Ni@CNF achieved removal efficiency of 98.9% for SDZ (2.5 mg/L) in 25 min, while the pure CNF hardly removed any SDZ under the identical conditions. The experimental data was better fitted by the Langmuir model with the maximum monolayer adsorption capacity of 103.21 mg/g at 318 K. Besides, the 9%Ni@CNF exhibited great applicability to various organic contaminants, and excellent stability and reusability over five consecutive cycles. Overall, for the first time, we provide the evidence that Ni atoms in the Ni@CNF plays a crucial role in SDZ adsorption, which can guide us for constructing nickle incorporated adsorbents with impressive adsorption capacity in environmental remediation.

Introduction

Sulfonamides are extensively used in human and animals. Large proportions of these compounds are discharged as parent compounds or metabolites into environment via urine and feces (Białk-Bielińska et al., 2011). Sulfadiazine (SDZ), a high soluble and chemical stable antibiotics, is commonly detected in a large-scale river system of China (Qin et al., 2020). The occurrence of SDZ in aquatic environment can cause antibiotic resistance, threatening to the ecological system and human health. Thus, searching efficient techniques to remove SDZ from environment is of great significance.

In general, advanced oxidation (Yang et al., 2021, Zhang et al., 2020, Zeng et al., 2020), membrane separation (Gao et al., 2021, Gao et al., 2021, Liu et al., 2017, Ji et al., 2009), and adsorption (Wang et al., 2020, Feng et al., 2021, Feng et al., 2021, Dai et al., 2021) are commonly used removal approaches for antibiotics. The advanced oxidation processes (AOP) technique can achieve a high removal efficiency, but a great deal of toxic degradation intermediates are produced as well (Kovalakova et al., 2021). With regard to the membrane technology, the high cost and membrane contamination limit its application. Conversely, adsorption has been appreciated and widely applied thanks to its high effectiveness, operation convenience and low cost. In this technique, developing high efficient, recyclable, environmental friendly adsorbents is crucial for efficient removal of SDZ. Metal-free carbon materials including activated carbon, carbon nanotubes, and carbon nanofibers, are the most attractive materials owing to their developed pore structure and chemical stability properties (Carabineiro et al., 2012). Unfortunately, most of carbon materials exhibits unsatisfactory adsorption capacity (Qe) and rate for SDZ. For instance, Fan et al. examined the adsorption behavior of SDZ on the biochar. The Qe value of biochar for SDZ was determined as 25.16 mg/g, and the adsorption process reached equilibrium in 1000 min (Fan et al., 2021). Manjunath et al. reported that the Qe of potassium hydroxide activated Prosopis juliflora activated carbon (KPAC) for SDZ, metronidazole, tetracycline were 18.48 mg/g, 25.06 mg/g, 28.81 mg/g, respectively (Manjunath et al., 2020). Zhang et al. reported that the Qe achieved by expanded graphite (EG) for SDZ was 16.59 mg/g at 298 K within 750 min (Zhang et al., 2017).

Carbon nanofibers (CNF), a highly microporous carbon material, have received massive attention due to its high porosity, small fiber diameter, high specific surface area, and abundant and shallow micro/mesopores (Wang et al., 2018, Qian et al., 2021). And CNF has been applied in the adsorption of formaldehyde (Buyukada-Kesici et al., 2021), benzene (Guo et al., 2016), toxic greenhouse gases (Tajer et al., 2021), metal ions (Yuan et al., 2019) and small dye molecules (Saharan et al., 2021). CNF is usually recycled by filtration or centrifugation after adsorption due to its non-magnetic property, which has the drawbacks of time-consuming, low recovery rate, and complex operation, greatly inhibiting its practical application. Therefor, it’s meaningful to explore novel hybrid CNF based adsorbents with high adsorption capacity and can be readily recycled from the aqueous phase.

As a essential transition metal element, nickel (Ni) shows fascinating merits of ferromagnetism at room temperature and excellent corrosion resistance. Nickel oxides and hydroxides (i.e., NiO, Ni(OH)2, NiFe2O4, NiFe LDH) possess outstanding features of low cost, excellent chemical and thermal stability, and environmental compatibility. Particularly, nickel species show strong adsorption affinity toward Congo red (Zheng et al., 2021, Zheng et al., 2017). It’s expected that the incorporation of Ni into/onto CNF can endow magnetism for convenient separation from aqueous solution and may improve its adsorption performance as well. Yet, to our best knowledge, there is rare research on study the adsorption performance of CNF reinforced with nickel for SDZ and examine the role of nickle atoms in the adsorption mechanism using density functional theory (DFT) calculations.

In this study, we first applied DFT calculations to simulate and evaluate the adsorption behaviors of SDZ on to the nickle incorporated CNF (Ni@CNF). Inspired by the computational results, Ni@CNF with different Ni contents were prepared via electrospinning method and applied for the SDZ removal from aqueous solutions. The morphology, crystalline structure, and physicochemical properties of the CNF and Ni@CNF were analyzed comprehensively. Factors affecting the adsorption performance were tested. Meanwhile, the adsorption kinetic and isotherms models were employed to examine the adsorption process. Furthermore, the reusability, stability, and applicability of the adsorbent was assessed, and the associated adsorption mechanism of SDZ by Ni@CNF was clarified as well. The present work not only highlights the novel application of Ni@CNF for SDZ adsorption but also provides clues for the design of nickle incorporated adsorbents.

Section snippets

Reagents

SDZ was obtained from Macklin®, and other reagents were obtained from Sinopharm Chemical Reagent Co., Ltd. (Beijing, China). All chemicals were analytical pure and utilized as received without any further purification. Ultrapure water (Veolia Water Solutions & Technologies) used in the study was obtained from an ultrapure water purification system.

Preparation and characterization of Ni@CNF

Ni@CNF was synthesized via electrospinning as illustrated in Fig. 1. Initially, 2.7 g of PAN were added to 25.0 g of DMF, and the resulting mixture

Adsorbents characterization

The morphologies of the pristine CNF and Ni@CNF were examined by SEM and TEM first. Fig. 2a–d illustrates the SEM images of CNF and 9%Ni@CNF. It can be clearly seen that CNF and 9%Ni@CNF maintains a network-like nanoarchitecture generated by the interactions of nanofibers with diameter of 150 nm. The Figure displays the high quality, smooth and uniform nature of CNF. In comparison, with the introduction of Ni2+ in the spinning solution, a plenty number of nickel particles can be found

Conclusions

This work initially evaluated the mechanism via DFT calculations, which provided us with clues and encouraged us to conduct further experiments. Magnetic nickel incorporated carbon nanofibers (Ni@CNF) with different mass ratios of Ni (3%Ni@CNF, 6%Ni@CNF, 9%Ni@CNF) were successfully prepared by electrostatic spinning method. Both the DFT calculations and experiments results showed that higher mass content of Ni in Ni@CNF resulted in higher adsorption capacity. The as-prepared 9%Ni@CNF achieved a

CRediT authorship contribution statement

Simeng Xia: Conceptualization, Investigation, Methodology, Writing – original draft. Lin Deng: Conceptualization, Writing – review & editing, Funding acquisition. Xia Liu: Computational analysis, Investigation. Lingfang Yang: Investigation, Methodology, Formal analysis. Xiuzhen Yang: Investigation, Methodology. Zhou Shi: Writing – review & editing, Funding acquisition. Yong Pei: Computational analysis, Writing – review & editing.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work was supported by the Natural Science Foundation of Hunan Province (2018JJ3062), National Key Research and Development Program of China (2019YFD1100102), National Natural Science Foundation of China (51878256).

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