Application of a novel rGO-CuFeS2 composite catalyst conjugated to microwave irradiation for ultra-fast real textile wastewater treatment

https://doi.org/10.1016/j.jwpe.2020.101397Get rights and content

Abstract

The disposal of wastewater containing large amounts of dyes is a public health and environmental problem, due to its toxicity into the aquatic biota, the reduction in sunlight penetration, which consequently interference in photosynthetic activity. In the present study a new composite, based on the heterojunction of reduced graphene oxide (rGO) and chalcopyrite (CuFeS2), was developed to treat a real textile wastewater (RW). The efficiency of the composite assisted by microwave irradiation was evaluated to catalyze the decolorization and degradation of RW containing a high concentration of the azo Direct Black 22 (DB22). A small amount (0.5 w/w%) of rGO on CuFeS2 was enough to uplift the efficiency of decolorization to 74 % of DB22 and 97 % TOC in the RW, only in the first min of treatment, and 97 % and 99 %, respectively, at 6 min. The improvement in catalytic activity can be attributed to the dipolar polarization effect, hot spots and the generation of hydroxyl radicals. Additionally, a synergistic effect between the composite and microwave irradiation, assisted by hydrogen peroxide, reduced the RW phytotoxicity, improving the radicle length of Lactuca sativa three times (from 0.87 cm to 2.65 cm with the application of a single minute of treatment). The reduction in phytotoxicity led to an increase in the germination percentage from 36 % to 53 %. Finally, the use of MW irradiation coupled to a novel rGO-CuFeS2 composite, in presence of H2O2 under acid medium, provides a feasible and highly rapid method to treat RW, reducing its phytotoxicity.

Capsule: A novel rGO-CuFeS2 catalyst was developed and applied together with microwave irradiation for an ultra-fast degradation treatment (6 min) in real textile wastewater.

Introduction

Dyes are compounds used in the manufacturing of various products such as textiles, detergents, papers, food, cosmetics and paints. This versatility for industrial applications generates large amounts of dye contaminated effluents, which can cause environmental and public health problems. Dyes must be stable to the light, to washing processes and uniformly fixate to the substrate, being also difficult to treat. The high concentration of dyes in the discharged industrial wastewaters causes a decrease of the sunlight penetration in water and reduction of the solubility of gases in the aquatic environments, lead to the modification of the biota [[1], [2], [3], [4]]. Also, since these residues might be carcinogenic, an adequate treatment before discharged into the environment is of highest priority [5].

In the last years, advanced oxidation processes have been used as a safe and effective alternative for the treatment of complex and hazardous wastewaters [6]. The use of energy sources in these processes, such as ultrasound and ultraviolet light irradiation, improve degradation reaction rates. As a novel trend, the use of microwave (MW) irradiation is presented as a mild energy source, capable of providing thermal and non-thermal effects [7]. MW assisted reactions becomes an even more attractive method for degrading organic pollutants when combined with a catalyst containing excellent MW absorption properties, where synergistic effects can be observed. Furthermore, MW irradiation contribute with uniform heating and formation of hot spots, a specific form of energy absorption [8].

Previous studies have reported successful use of iron [9] and copper based [10] catalysts in MW assisted treatments. Chalcopyrite is a mineral that combines both Fe and Cu in a crystalline structure, such as CuFeS2. As a catalyst, it leads to the formation of non-selective hydroxyl radicals (radical dotOH), by accelerating H2O and H2O2 decomposition under acidic medium in short time frames, which already occurs by MW irradiation itself [8,9,[11], [12], [13], [14]]. Moreover, CuFeS2 presents low optical energy band gap of 0.5–0.6 eV, being very interesting for these applications [[15], [16], [17], [18], [19], [20]]. However, CuFeS2 presents small specific surface area, about 3 to 5 m2 g−1 [21], which can affect hot spots formation as well as the whole process. The hot spots are generated by the temperature difference at the reaction site and in the medium. This facilitates the destruction of complex chemical bonds, decreasing the activation energy and increasing the reaction rate [22].

An alternative to solve this problem consists on coupling of CuFeS2 to other material containing large pores and high surface area. An excellent material is reduced graphene oxide (rGO), due to its high electronic mobility and conductivity, high chemical stability and specific surface area, leading to greater adsorption capacity [[23], [24], [25]]. When combined with inorganic semiconductor catalysts, the different Fermi levels of the rGO and inorganic semiconductors generate a strong heterojunction electric field at the interfaces. The interfacial electric field promotes the rapid transfer of generated electrons to the surface of the rGO and, therefore, prolongs the life of the electron-hole generated pairs [23,24,26].

Many studies have described the combination of inorganic semiconductor catalysts and rGO, resulting in formation of the graphene-based composites with superior catalytic activity [18,[23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33]]. However, the preparation of rGO-CuFeS2 composite as well as its performance combined to MW irradiation towards textile wastewater treatment has not been reported yet. Therefore, rGO-CuFeS2 composites with different weight ratios of rGO and CuFeS2 were prepared. Its catalytic efficiencies were evaluated for degradation of real textile wastewater (RW) from a factory in Mar del Plata (Argentina), containing the azo dye Direct Black 22 (DB22), under different experimental conditions (pH, H2O2, concentration, composite amount) in coupling with MW irradiation, in order to obtain optimal reaction parameters. Finally, a phytotoxicity test of the treated RW to Lactuca sativa was applied.

Section snippets

Synthesis of rGO-CuFeS2 composite

Graphite oxide was synthesized from graphite flake (Sigma-Aldrich) by a modified Hummers method [34]. Exfoliation of graphite oxide to graphene oxide (GO) was achieved by sonication for particles dispersion. The obtained brown dispersion was then subjected to centrifugation to remove any unexfoliated graphite oxide. GO reduction was obtained by the addition of N2H4·H2O. The as-prepared GO solution was diluted in deionized water under ultrasonication and vigorous stirring. The product obtained

rGO-CuFeS2 characterization

XRD patterns of rGO, CuFeS2 and composites are shown in Fig. 1. A typical diffraction broad peak with low intensity appears at 26° for the rGO sample [23,32,40]. In addition, as it is present in a low proportion, only small shifts can be observed in the patterns obtained for the composites. The CuFeS2 presents characteristics peaks at 29.37, 48.97 and 48.68°, corresponding to those given in the reference pattern (ICDD PDF 35−0752), as in published research [[17], [18], [19],41].

Results obtained

Conclusions

In this work, a new rGO-CuFeS2 composite was synthesized and successfully applied to the treatment of RW under MW irradiation. The novelty of this work lies in the use of real textile wastewater, without a pretreatment, without additional carbon sources and undiluted, using an unprecedented composite for this application coupling microwave irradiation. MW energy is insufficient to produce the cleavage of chemical azo bonds of the DB22 dye present in the RW. However, MW energy in acidic medium

CRediT authorship contribution statement

Yasmin Vieira: Conceptualization, Formal analysis, Investigation, Methodology, Validation, Writing - original draft. María Belén Ceretta: Conceptualization, Formal analysis, Funding acquisition, Investigation, Methodology, Validation, Writing - original draft. Edson Luiz Foletto: Writing - review & editing. Erika Alejandra Wolski: Funding acquisition, Investigation, Methodology, Project administration, Supervision, Writing - original draft, Writing - review & editing. Siara Silvestri:

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

The authors are immensely grateful to Júlia da Silveira Salla for providing the CuFeS2 and the financial support provided by CNPq, CAPES/FAPERGS (Bolsista CAPES/BRASIL: 88887.195036/2018-00), CONICET (PIP 0101/2015), National University of Mar del Plata (15/G560-2019) and Montevideo Group by Graduate Student Scale Program scholarship (PEEPg). Maria Belén Ceretta is a fellow of CONICET.

References (63)

  • E. Yagmur et al.

    The relative performance of microwave regenerated activated carbons on the removal of phenolic pollutants

    J. Clean. Prod.

    (2017)
  • N. Wu et al.

    Design of chalcopyrite-type CuFeSe2 nanocrystals: Microstructure, magnetism, photoluminescence and sensing performances

    J. Solid State Chem.

    (2019)
  • K.M. Deen et al.

    On the use of a naturally-sourced CuFeS2 mineral concentrate for energy storage

    Electrochim. Acta

    (2019)
  • U. Rajaji et al.

    Graphene oxide encapsulated 3D porous chalcopyrite (CuFeS2) nanocomposite as an emerging electrocatalyst for agro-hazardous (methyl paraoxon) detection in vegetables

    Compos. Part B Eng.

    (2019)
  • P. Huang et al.

    Adsorption of chitosan on chalcopyrite and galena from aqueous suspensions

    Colloids Surfaces A Physicochem. Eng. Asp.

    (2012)
  • N. Remya et al.

    Current status of microwave application in wastewater treatment-a review

    Chem. Eng. J.

    (2011)
  • Y. Zhao et al.

    Enhanced photocatalytic properties of ZnO/reduced graphene oxide sheets (rGO) composites with controllable morphology and composition

    Appl. Surf. Sci.

    (2017)
  • S. Rabieh et al.

    Synthesis of hierarchical ZnO-reduced graphene oxide nanocomposites with enhanced adsorption-photocatalytic performance

    Mater. Lett.

    (2016)
  • E. Rokhsat et al.

    Improving the photocatalytic activity of graphene oxide/ZnO nanorod films by UV irradiation

    Appl. Surf. Sci.

    (2016)
  • S.H. Xia et al.

    Reduced graphene oxide modified flower-like BiOCOOH architectures with enhanced photocatalytic activity

    Mater. Lett.

    (2015)
  • F. Wang et al.

    Reduced graphene oxide-TiO2 nanocomposite with high photocatalystic activity for the degradation of rhodamine B

    J. Mol. Catal. A Chem.

    (2011)
  • J. Shen et al.

    Facile fabrication of magnetic reduced graphene oxide-ZnFe 2 O 4 composites with enhanced adsorption and photocatalytic activity

    Appl. Surf. Sci.

    (2015)
  • S. Guo et al.

    Graphene oxide-Fe2O3 hybrid material as highly efficient heterogeneous catalyst for degradation of organic contaminants

    Carbon

    (2013)
  • Y. Zhang et al.

    Biochar-supported reduced graphene oxide composite for adsorption and coadsorption of atrazine and lead ions

    Appl. Surf. Sci.

    (2018)
  • M. Zhou et al.

    Synthesis and enhanced photocatalytic performance of WO 3 nanorods @ graphene nanocomposites

    Mater. Lett.

    (2012)
  • S. Silvestri et al.

    Degradation of methylene blue using Zn2SnO4 catalysts prepared with pore- forming agents

    Mater. Res. Bull.

    (2019)
  • S. Silvestri et al.

    TiO2 supported on Salvinia molesta biochar for heterogeneous photocatalytic degradation of Acid Orange 7 dye

    J. Environ. Chem. Eng.

    (2019)
  • S. Silvestri et al.

    Synthesis of PPy-ZnO composite used as photocatalyst for the degradation of diclofenac under simulated solar irradiation

    J. Photochem. Photobiol. A: Chem.

    (2019)
  • M. Wojtoniszak et al.

    Synthesis, dispersion, and cytocompatibility of graphene oxide and reduced graphene oxide

    Colloids Surf. B Biointerfaces

    (2012)
  • E. Dutková et al.

    Mechanochemical synthesis, structural, magnetic, optical and electrooptical properties of CuFeS2 nanoparticles

    Adv. Powder Technol.

    (2018)
  • T. Wang et al.

    Lead-free double perovskite Cs2AgBiBr6/RGO composite for efficient visible light photocatalytic H2 evolution

    Appl. Catal. B Environ.

    (2020)
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