Peroxymonosulfate activation by recycling of discarded cigarette filters: Selective degradation of contaminants

https://doi.org/10.1016/j.jtice.2021.11.006Get rights and content

Highlights

  • UCF is made from discarded cigarette filters and is environmentally friendly.

  • UCF exhibited superior performance towards peroxymonosulfate activation.

  • UCF collection a wide range, large abandonment but small usage.

  • UCF has a porous flocculent appearance, where trapped heteroatoms also provide active sites.

  • Both radicals and non-radical pathways coexist in the system.

Abstract

Background

The conversion of waste biomass into multi-hole carbon materials is an effective way in recent years. A new type of biochar was prepared by one-step calcination method by utilizing used cigarette filter (UCF) as raw material. In addition, we investigated the catalytic degradation properties of UCF, as well as the degradation mechanism.

Methods

The catalytic degradation properties of the material were verified by degradation experiments. The morphology of the material, and the microstructural state, were analyzed by SEM (Scanning Electron Microscope) and HRTEM (High Resolution Transmission Electron Microscopy). Using Raman, XRD (X-ray diffraction), BET, XPS (X-ray photoelectron spectroscopy) studied the structure and chemical composition of the material. The degradation mechanism was analyzed by quenching experiments and EPR (Electron Paramagnetic Resonance), XPS.

Significant findings

The first, UCF completely removed 0.01 g L−1 Rhodamine B within 80 min. And, degradation rate of Rhodamine B is as high as 95% within 20 min. Some defects were observed, and the dominant microporous structures and high specific surface area were present. The heteroatom in the UCF effectively activated the sp2-hybridized carbon crystal lattice, leading to the creation of more activation sites in UCF. Different carbide temperatures also affected the degree of material graphitization, and UCF (700 °C) had rich defects and larger porous structures. Besides, Electron paramagnetic resonance and quenching experiments showed that UCF degradation systems acted via free and non-radical pathways. The mechanism of catalytic degradation and the reasonable source of heterogeneous atoms at the catalytic site were also proposed. The use of the discarded cigarette filter as a low-cost catalyst for persulfate has great potential.

Introduction

In recent years, organic pollution in the water environment has become increasingly serious e.g., dyes [1]. These organic compounds are non-biodegradable; thus, we always struggle to handle them with traditional primitive technology. Advanced oxidation processes (AOPs) are a widely applicable technology for treating refractory wastewater [2]. A particular example is persulfate-based AOPs, the persulfate produces highly oxidized SO4•−that can better handle contaminants [3]. In metal-driven persulfate activation processes, leaching of metal leads to secondary water pollution, which results in high cost and energy input [4]. Therefore, environmentally friendly non-metallic catalysts need to be developed and studied [5].

Carbon-based materials are widely developed due to their higher cost performance, adjustable electronic structure, and little damage to the environment [6]. The doping of heteroatom is an effective method to activate the sp2-hybridized carbon crystal lattice [7]. Most doped heteroatoms are more electronegative than carbon and accelerate electronic transport between catalyst and persulfate [8]. It was found that the peroxymonosulfate (PMS) activation performance improved when oxygen-containing functional groups (C=O) were introduced into our material, due to the improved conductivity of the material [9]. Using appropriate carbon materials is important, because they save costs and bring about environmentally friendly changes.

When we choose the catalytic material, we always consider its economic factors and the sustainability in the environment, so biomass is a very promising choice of biochar material [10]. Biocarbon mostly use wood, shell, and plant materials [11] to produce solid-state substances, but problems are present, such as excessive using, recycling difficulty, and the use of seasonal plant materials. Such problems hinder the extensive application of biocarbon materials in practice (Text S1) .

Massive amounts of discarded cigarette filters (CFs) pollute the environment, and finding suitable ways to recycle the discarded cigarette butts has become a worldwide problem. The material used to make the CF is fiber acetate; it shows good interception of filtration. We previously confirmed that the degradation of black 5 dyes using discarded CFs achieved good results [12]. During smoking, CF can introduce miscellaneous atoms into the carbon network and increase the defects of biocarbon materials. These advantages of CF show that the use of waste CF will solve problems, and it has good application prospects. However, the applications to PMS activation have not been reported.

This study presents a method for simply recycling discarded CFs for the preparation of used CF (UCF) catalysts. We synthesized porous carbon networks (UCF) through one-step thermal polymerization. In addition, we selected Rhodamine B, a biodegradable organic matter in the textile industry, as the target pollutant of pollution degradation, to evaluate the degradation effect of PMS system on pollution. Then, we discussed the material characterization and mechanism and explained the UCF active sites. The conversion of the main active substances between UCF and new cigarette filter (NCF) was verified by combining quenching experiments and electron paramagnetic resonance spectroscopy. Moreover, in the system where UCF activates PMS, we found the free radical and non-free radical. Recycling used cigarette filter has become a feasible method for advanced water treatment, thereby providing a new direction for PMS activation and utilization of waste biological carbon materials. Moreover, a favorable reference for the sustainable development of the environment is provided.

Section snippets

Chemicals

Rhodamine B (RhB), all reagents and peroxymonosulfate were purchased in Aladdin (China), and all raw material was purchased without further purification. All the used cigarette filter (UCF) were collected in Shanghai University of Electric Power's campus. New cigarette filter was Haomao brand.

Material synthesis

The collected discarded cigarettes are stripped off and then material was sent in an oven dried at 105 °C for 24 h. The obtained precursor was carbonized under N2 at 700 °C, with the aim to protect the

Characterizations of UCF

The materials’ morphologies of NCF and UCF were obtained by SEM, and the test results in the reaction are shown in Fig. 1. The pristine CF (Fig. 1a,b) exhibited a huge and complex structure, and its surface had a smooth texture and constructed by flattened walls. In contrast, the morphology of UCF showed a dramatic change. As shown in Fig. 1c,d, UCF exhibited bumpy and highly interpenetrated network structures. There are still no transformations that have been found in a few areas. Possibly,

Conclusion

A simple method for recovering CF was proposed and obtained porous carbon material NCF and UCF. Recycling CF was used for creating biocarbon materials through comparison and characterization. UCF with high porosity could efficiently degrade organic pollutants, which not only had good catalytic properties, but also was environmentally friendly. Pollutants was completely degraded within 80 min, and the degradation rate also reached 95% at 20 min in UCF system. UCF graded 0.01 g L−1 RhB within

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.

Acknowledgments

The study was supported by the Science and Technology Commission of Shanghai Municipality (21ZR1425200, 19DZ2271100).

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      In the field of environmental engineering, CB recycling by-products are mainly applied in water and sewage treatment following the idea of “cleaning the environment by recycling waste”. Some examples are oil/water separation, removal of phosphates and organic matter, diclofenac, lead (Kurmus and Mohajerani, 2020; Huang et al., 2022), heavy metals (Zhang et al., 2021a), tobacco-specific carcinogens (Zhang et al., 2021b) and antibiotics (Wang et al., 2022). Another use of recycled CB is to turn its cellulose acetate into hot melt adhesives to solve environmental problems caused by waste from petroleum derivatives (Kim et al., 2021).

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