Comparative study on the removal of organic pollutants by magnetic composite and pre-magnetized zero-valent iron activated persulfate
Graphical abstract
Introduction
Over the past few years, a series of reports have demonstrated the enhanced removal of heavy metals or organic pollutants via zero-valent iron (ZVI) coupled with a weak magnetic field (WMF) (Wu et al., 2018, 2020a). As extension of this research “boom”, using pre-magnetized ZVI (Pre-ZVI) to activate persulfate (PS) for organic pollutant removal has been drawing increasing attention, because the performance of Pre-ZVI is superior to that of pristine ZVI (Li et al., 2015; Pan et al., 2018; Xu et al., 2016; Zhang et al., 2019). However, the lifetime of the “magnetic memory” of Pre-ZVI (under the influence of the earth's magnetic field) is critical to practical applications. While a handful of studies explored the effects of different pre-magnetization methods on the removal of target pollutants, long-term observations of the lifetime of magnetic memory were scarcely reported (Huang et al., 2018; Pan et al., 2018; Wu et al., 2020a).
In addition to the activation of PS via ZVI (including using Pre-ZVI), attempts to activate PS using carbon-bearing materials continue to be reported, suggesting that this is also a viable activation method (Cheng et al., 2019; Dong et al., 2019; Zhang et al., 2021). Waste carbon-bearing stuff is ubiquitous in the environment, and it will be of great environmental significance if we can make full use of it for PS activation. Lignocellulose is a sustainable alternative to diminishing fossil resources and the most abundant renewable biomass resources in natural environment (Guan et al., 2020). Over the past decades, online shopping has become a popular lifestyle, accompanied by the rapid development of the logistics industry. Due to the extensive use of packaging carton worldwide (Clomburg et al., 2017; Wang et al., 2020), massive quantities of them are discarded in urban areas every day, causing an increasing burden for municipal solid waste (MSW) disposal. Our previous study successfully fabricated C/Fe composites via a three-step process from waste cartons; the composites exhibited good adsorption of selected dyes (Wu et al., 2020b). The present study seeks to discover whether these types of composites prepared from waste cartons can be efficiently applied to activate PS, and to compare their performance with that of Pre-ZVI activated PS (Pre-ZVI/PS).
In this study, considering the potential value of waste cartons and the previous fabrication process, we attempted to prepare MC via a one-step hydrothermal process from waste cartons for valorization, and to use that composite to activate PS (MC/PS) for treating organic pollutants. The objectives of this research are to (i) compare the removal efficiencies of MB for both MC/PS and Pre-ZVI/PS; (ii) scrutinize the property of the MC to further unravel the internal reaction mechanism; (iii) identify the transformation products of MB by liquid chromatography tandem mass spectrometry (LC-MS/MS). The novelty lies in MB removal by MC/PS from waste cartons and the findings of magnetic memory decay over 30 days in the Pre-ZVI/PS treatment. This study aims to propose a new environmentally friendly and low-cost advanced oxidation process (AOP) for wastewater treatment, which could be adopted for the highly efficient removal of organic pollutants.
Section snippets
Chemicals
Commercial-grade iron (CAS No. 7439-89-6, ≥99 %, reduced, powder (fine)) was purchased from Sigma-Aldrich Co., Ltd (Germany). Methylene blue (CAS No. 61-73-4) was purchased from Tianjin Guangfu Fine Chemical Research Institution (Tianjin, China). Methanol (CAS No. 67-56-1) and tert-butanol (CAS No. 75-65-0) were purchased from Fuchen (Tianjin) Chemical Reagents Co., Ltd (China). Sodium persulfate (CAS NO. 7775-27-1) and the other reagents used in this study were obtained from Xilong Scientific
BET
An automatic specific surface area analyzer (ASAP, 2020; Micromeritics, USA) was used to determine the BET surface area of the composite from the nitrogen adsorption isotherm at −196 °C. The BET parameters are shown in Table 1. The BET specific surface area of the present composite was less than that obtained via our previous three-step process (Wu et al., 2020b). Atta-Obeng et al. (2017) indicated that lignin cannot be easily hydrothermally carbonized until 350 °C. We speculate that this may
Conclusion
In this study, we fabricated a MC from waste cartons via one-step hydrothermal conversion, and compared its performance for the activating of PS against that of Pre-ZVI. Both MC/PS and Pre-ZVI/PS treatments could be efficient ways of removing MB. The MB removal efficiency of the Pre-ZVI/PS process reached nearly 90 %, while that of the MC/PS process approached 100 %. After two cycles of magnetic separation, the MC/PS system still achieved rapid and effective decoloration and COD removal for MB.
Author contribution
Yang Wu: Conceptualization, Methodology, Software, Validation, Project administration, Writing - review & editing, Funding acquisition. Xin Fang: Methodology, Writing - original draft, Formal analysis. Xiang-Tian Yang: Methodology, Writing - original draft. Chung-Yu Guan: Supervision, Validation, Writing - review & editing. Xin-Ru Sun: Software. Hong-Yu Wu: Software. Anyi Hu: Methodology, Funding acquisition. Li-Feng Lin: Resources. Qing-Qing Xiao: Resources.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence this publication.
Acknowledgements
This work was supported by Open Fund of the Key Laboratory of Urban Pollutant Conversion, Chinese Academy of Sciences (KLUPC-KF-2020-3), the Anhui Provincial Natural Science Foundation (grant number 1908085ME170), the National Science Foundation of China (grant number 31870475), and Domestic Visiting Project for Youth Talent in Universities of Anhui Province in 2021 (gxgnfx2021160). We are grateful to Ms. Jiani Wang for the XRD measurements.
References (47)
- et al.
Physico-chemical characterization of carbons produced from technical lignin by sub-critical hydrothermal carbonization
Biomass Bioenergy
(2017) - et al.
Photodegradation of methyl violet 6B and methylene blue using tin-oxide nanoparticles (synthesized via a green route)
J. Photochem. Photobiol., A
(2016) - et al.
High-efficiency and selective adsorption of organic pollutants by magnetic CoFe2O4/graphene oxide adsorbents: experimental and molecular dynamics simulation study
Separ. Purif. Technol.
(2020) - et al.
Insights into the mechanism of nonradical reactions of persulfate activated by carbon nanotubes: activation performance and structure-function relationship
Water Res.
(2019) - et al.
Enhanced persulfate degradation of PAH-contaminated sediments using magnetic carbon microspheres as the catalyst substrate
Process Saf. Environ.
(2019) - et al.
Occurrence of radical and nonradical pathways from carbocatalysts for aqueous and nonaqueous catalytic oxidation
Appl. Catal. B Environ.
(2016) - et al.
The adsorption of basic dye (Alizarin red S) from aqueous solution onto activated carbon/γ-Fe2O3 nano-composite: kinetic and equilibrium studies
Mater. Sci. Semicond. Process.
(2015) - et al.
Methylene blue discoloration by heated persulfate in aqueous solution
Chem. Eng. J.
(2012) - et al.
Efficient activation of persulfate by a magnetic recyclable rape straw biochar catalyst for the degradation of tetracycline hydrochloride in water
Sci. Total Environ.
(2021) - et al.
Pre-magnetization by weak magnetic field enhancing Fe0-Fenton process for wastewater treatment
Chem. Eng. J.
(2018)