Os herbicidas são uma classe importante de agroquímicos usados para o controle de plantas daninhas. Os herbicidas organoclorados apresentam alta toxicidade e persistência ambiental, aumentando o risco de contaminação do solo e da água. Os clorofenóis e seus derivados são contaminantes tóxicos do meio ambiente oriundos da degradação de agroquímicos. Nanopartículas de ferro metálico (Fe-NPs) têm sido utilizadas para a remoção e degradação de uma variedade de poluentes orgânicos, incluindo herbicidas e compostos organoclorados. O objetivo deste trabalho foi estudar a síntese de Fe-NPs e sua aplicação na degradação do 4-clorofenol (4-CP). Fe-NPs com tamanho médio de 113 nm compostas pela fase ?-Fe foram obtidas através da redução de borohidreto. As Fe-NPs foram misturadas com 500 ?M de 4-CP em vários valores de pH. A degradação do 4-CP foi confirmada pelo monitoramento da banda de absorção em 298 nm. Além disso, a produção de fenol foi seguida pela reação com monocloramina que produz uma solução de cor azul com absorção máxima a 680 nm. A diminuição da absorbância em 298 nm sugere degradação do 4-CP

Marques, Renata Pereira

Martins, Tainara Ferreira

Moreto, Jéferson Aparecido

Nunes, Eloiza da Silva

Portuguese

Brazilian Journals

Brazilian Applied Science Review  Braz. Ap. Sci. Rev, Curitiba, v. 4, n. 6, p. 4013-4021  nov./dez. 2020           ISSN 2595-3621  4013  Synthesis  and application of metallic iron nanoparticles on the 4-Chorophenol degradation  Síntese e aplicação de nanopartículas de ferro metálico na degradação do 4-clorofenol  DOI:10.34115/basrv4n6-055  Recebimento dos originais: 22/11/2020 Aceitação para publicação: 22/12/2020  Tainara Ferreira Martins Mestre em Agroquímica pelo IF Goiano Instituto Federal de Educação, Ciência e Tecnologia Goiano (IF Goiano) Endereço: Rodovia Sul Goiana km 01, Zona Rural, CEP: 75.901-970, Rio Verde, Goiás, Brazil E-mail: tainara.marfe@gmail.com  Renata Pereira Marques Doutora em Agronomia pela UNESP-Botucatu Polo de Inovação, Instituto Federal Goiano (IF Goiano) Endereço: Rodovia Sul Goiana Km 01, Zona Rural, CEP: 75.901-970, Rio Verde, Goiás, Brazil E-mail: renata.marques@ifgoiano.edu.br  Jéferson Aparecido Moreto Doutor em Engenharia e Ciência dos Materiais pela USP-São Carlos Universidade Federal do Triângulo Mineiro (UFTM) Endereço: Avenida Doutor Randolfo Borges Júnior, Univerdecidade, CEP: 38.064-200, Uberaba, Minas Gerais, Brazil E-mail: jeferson.moreto.uftm@gmail.com  Eloiza da Silva Nunes Doutora em Química pela UNESP-Araraquara Instituto Federal de Educação, Ciência e Tecnologia Goiano (IF Goiano) Endereço: Rodovia Sul Goiana km 01, Zona Rural, CEP: 75.901-970, Rio Verde, Goiás, Brazil. E-mail: eloiza.nunes@ifgoiano.edu.br  RESUMO  Os herbicidas são uma classe importante de agroquímicos usados para o controle de plantas daninhas. Os herbicidas organoclorados apresentam alta toxicidade e persistência ambiental, aumentando o risco de contaminação do solo e da água. Os clorofenóis e seus derivados são contaminantes tóxicos do meio ambiente oriundos da degradação de agroquímicos. Nanopartículas de ferro metálico (Fe-NPs) têm sido utilizadas para a remoção e degradação de uma variedade de poluentes orgânicos, incluindo herbicidas e compostos organoclorados. O objetivo deste trabalho foi estudar a síntese de Fe-NPs e sua aplicação na degradação do 4-clorofenol (4-CP). Fe-NPs com tamanho médio de 113 nm compostas pela fase α-Fe foram obtidas através da redução de borohidreto. As Fe-NPs foram misturadas com 500 μM de 4-CP em vários valores de pH. A degradação do 4-CP foi confirmada pelo monitoramento da banda de absorção em 298 nm. Além disso, a produção de fenol foi seguida pela reação com monocloramina que produz uma solução de cor azul com absorção máxima a 680 nm. A diminuição da absorbância em 298 nm sugere degradação do 4-CP.  Brazilian Applied Science Review  Braz. Ap. Sci. Rev, Curitiba, v. 4, n. 6, p. 4013-4021  nov./dez. 2020           ISSN 2595-3621  4014  Palavras-chave: Ferro zero valente, organoclorados, fenol, degradação.  ABSTRACT Herbicides are an important class of agrochemicals used for weed control. Organochloride herbicides show high toxicity and environmental persistence increasing the risk of soil and water contamination. Chlorophenols and their derivatives are toxic contaminants in the environment originated from degradation of agrochemicals. Metallic iron nanoparticles (Fe-NPs) have been used for removal and degradation of a range of organic pollutants, including herbicides and organochlorides compounds. The aim of this work was to study the synthesis of Fe-NPs and their application in 4-chlorophenol (4-CP) degradation. Fe-NPs with average size of 113 nm composed of α-Fe phase were obtained through borohydride reduction. The Fe-NPs were mixed with 500 μM of 4-CP at several pH values. The degradation of 4-CP was confirmed by monitoring the absorption band at 298 nm. Additionally, the phenol production was followed by reaction with monochloramine which produces a blue colored solution with maximum absorption at 680 nm. The decrease in absorbance in 298 nm suggest degradation of 4-CP.  Keywords: Zero valent iron, organochlorides, phenol, degradation.  1 INTRODUCTION The increasing number of human industrial and urban activities in the last decades led to accumulation of innumerous pollutants in natural hydric resources, such as pesticides, dyes and heavy metals (YONGLONG LU et al., 2015). As reported by Taghizade et al (TAGHIZADE et al., 2018) the residue of these pesticides may be dispersed on the soil, groundwater and drinking waters. This critical environmental impact has been subject in the development of new materials and protocols for water remediation. In this scenario, nanotechnology products have attracted the interest of researchers over the decades due to its distinctive physicochemical properties and applications (SADHASIVAM et al., 2020; FENGLIAN FU et al. 2014).  Nanomaterials have been successfully used in a variety of applications, such as environmental (YAN XU et al., 2017; FANG LUO et al. 2016), medicine (BINGJUN SUN et al., 2016) and agriculture (TOSCO et al., 2014). In particular, metallic nanomaterials, such as iron and nickel, are of interest for environmental remediation applications. In the nanoparticulate form, metallic iron displays high reactivity towards organic compounds reduction. These characteristics emerge from the small size and high surface to volume ratio. The metallic iron redox standard potential is about -0.44 V which renders this material excellent reduction power towards several classes of organic compounds, such as halogenated hydrocarbons. Several studies report on the dehalogenation of hidrocarbons by using Fe-NPs (RAYCHOUDHURY et al., 2013; O’CARROLL et al., 2013; YAN et al., 2010).  Organochlorides are classified as highly toxic pollutants and are persistent on soil and water. They are originated from synthetic chemical derivatives of industrial use. Among the chlorinated organic compounds, 4-chlorophenol (4-CP) is largely used in agrochemicals, dyes, and some drugs synthesis. Brazilian Applied Science Review  Braz. Ap. Sci. Rev, Curitiba, v. 4, n. 6, p. 4013-4021  nov./dez. 2020           ISSN 2595-3621  4015  The 4-CP present high toxicity and low biodegradability, is potentially carcinogenic and biocumulative. The presence of 4-CP in the environment endangers human health (HWANG et al., 2015). The removal of chlorophenols is of great importance for the protection of natural resources and represents a technological challenge. In this context, the use of Fe-NP has demonstrating promising results for degradation of recalcitrant contaminants (DORATHI et al., 2012). Here, we studied the synthesis of Fe-NPs and their application in 4-CP degradation. It is an innovative and applied work with great potential in the agricultural area.  2 EXPERIMENTAL 2.1 MATERIALS All chemicals were used as received. Iron (II) chloride tetrahydrate (99% Sigma), sodium borohydride (96% Fluka), 4-chlorophenol (98% Sigma), phenol (99% Synth), sodium hydroxide (Alfatec, 99%), ammonium chloride (Cromoline 99%), sodium hipochloride (12% Dinâmica), sodium nitroprusside (99% Sigma).  2.2 SYNTHESIS OF FE-NPS The Fe-NPs were prepared by reduction of Fe2+ with sodium borohydride (NaBH4). Briefly, 4 mmol of iron(II) chloride were dissolved with 40 mL of water purged with argon gas. Then, 12 mmol of NaBH4 dispersed in 3 mL of triglyme was injected into the reaction vessel. The precipitate was magnetically decanted and washed three times with purged deionized water. The as-prepared Fe-NP were stocked in 20 mL of purged water for further experiments.  For characterization studies the Fe-NPs were dried under argon atmosphere. The X-ray diffractograms were recorded in a Siemens D5005 system using Cu Kα radiation, operating at 40 kV in the 2ɵ range between 20° and 90°. The size and morphology of the Fe-NPs were investigated by using a JEOL model JSM-7500F scanning electron microscope (SEM), operated at an accelerating voltage of 2 kV.  2.3 DEGRADATION EXPERIMENTS For degradation experiments aliquots of 4-CP stock solution were taken and added to a 50 mL tube, diluted with water and the pH was adjusted with 1.0 molL-1 HCl or NaOH solution to 2, 3, 4, 5, 6, 7, 8, 9 and 10. Each contaminant solution was sparged with argon gas and then 5 mL of Fe-NPs dispersion was added with. The final volume was adjusted to 25 mL with deionized water and the concentration of 4-CP was set at 500 µmolL-1. The system was thoroughly purged with argon gas, closed Brazilian Applied Science Review  Braz. Ap. Sci. Rev, Curitiba, v. 4, n. 6, p. 4013-4021  nov./dez. 2020           ISSN 2595-3621  4016  and allowed to react during 6 and 24 h. After, the Fe-NPs was removed by magnetic separation and the supernatant collected for spectrophotometric analysis.   2.4 ANALYTICAL METHODS The as-collected supernatants from the samples described above were used for measuring the UV-Visible spectra in the range of 200 to 400 nm in order to quantify the remaining 4-CP present in the sample solutions. The concentration was determined by the standard addition method using a calibration curve of 4-CP with concentrations ranging from 2 to 2000 μmolL-1 containing fixed volume of samples and measuring the absorption center at 298 nm.  The assay procedure used for phenol determination was based on studies developed by Hwang et al. (HWANG et al., 2015). In a typical analysis, reagent A is prepared by diluting 1 mL of 10% hypochlorite and 66 mL of 0.5 molL-1 NaOH solution to 100 mL with deionized water. Reagent B was prepared so as to contain 4.78 gL-1 of NH4Cl and 0.3 gL-1 of sodium nitroprusside (Na₂[Fe(CN)₅NO] ·2H₂O) dissolved in deionized water. A solution namely reagent AB was prepared by mixing equal volumes of reagent A and B. The quantification procedure was as follow: 2.3 mL of sample supernatant and was completed with reagent AB to 5 mL, than allowed to react in the dark for 2 h. After the UV-VIS spectra was acquired in the range of 400 to 800 nm. A calibration curve was obtained by varying the concentration from 2 to 50 μmol L-1 and measuring the absorbance at the center of the band (680 nm) and used for phenol quantification.  3 RESULTS AND DISCUSSION 3.1 FE-NPS CHARACTERIZATION The Fe-NPs were prepared by chemical reduction of Fe2+ with sodium borohydride (NaBH₄) in aqueous solution. The as-produced solid presented black coloration and was highly magnetic in nature. Figure 1 (a) displays the SEM images of the Fe-NPs and Figure 1 (b) the XRD pattern of as-synthesized Fe-NPs. As shown by the SEM images, the most of particles were nanosized, presenting a roughly spherical morphology. The average size of 113 ± 66 nm was obtained, suggesting a high polydispersity in particle sizes.  The XRD pattern (see Figure 1(b)) agree with the α-Fe crystalline phase, and the diffracted peaks matched the interplanar distances marked by the Bragg indexes (110), (200) and (211). The broadening of the diffraction peaks is more likely due to low crystallinity of the particles as well due to the existence of small (around 10-20 nm) nanocrystals in the sample (NUNES et al., 2014).   Brazilian Applied Science Review  Braz. Ap. Sci. Rev, Curitiba, v. 4, n. 6, p. 4013-4021  nov./dez. 2020           ISSN 2595-3621  4017  Figure 1. SEM image (a) and XRD pattern of as-synthesized Fe-NPs (b).   3.2 DEGRADATION OF 4-CHLOROPHENOL STUDY The degradation of 4-CP in presence of Fe-NP was evaluated for different pH and reaction time. Figure 2 shows the UV-VIS spectra of samples supernatant at pH range of 2 to 10 taken after 24 h of incubation. The decrease of the absorbance in 298 nm suggests the 4-CP degradation was larger for acidic pH’s. The pH 4 was optimum for 4-CP degradation and the remaining concentration in the sample supernatant was 86 μmolL-1. In the presence of proton donors, the reductive dehalogenation of chlorinated organic substances is favored (ARRUDA et al., 2020). According to Raja et al [16], the Fe-NP acts as an electron donor which reacts with 4-CP promoting a reductive dechlorination, since the process is thermodynamic favored (RAJA et al., 2005).  Figure 2. UV-VIS spectra of samples supernatant produced from 4-CP degradation for 24 h at different pH values.   Brazilian Applied Science Review  Braz. Ap. Sci. Rev, Curitiba, v. 4, n. 6, p. 4013-4021  nov./dez. 2020           ISSN 2595-3621  4018  The reduction of 4-CP with Fe-NP leads to phenol, driven by an electron transfer process. In order to identify and quantify the phenol as degradation product, the indophenol reaction was applied. In this reaction the product between monochloramine and phenol is a blue dye, which can be spectrophotometrically determinate (HWANG et al., 2015). Figure 3 presents the UV-VIS spectra of samples produced from 4CP degradation at pH range 2 to 10 after incubation times for 6 and 24 h and after treatment with the indophenol reaction. The absorption maximum at 700 nm was in accordance to Hwang et al (HWANG et al., 2015), confirming the phenol production. As observed in Figure 3, the phenol concentration did not increased significantly with time, and remained at about 1 μmol L-1. This observation suggests that could have other degradation by products. Raja et al (RAJA et al., 2005) observed a similar behavior in a Fenton-mediated degradation study of 4-CP.  Figure 3. UV-VIS spectra of samples supernatant produced at different pH values after the indophenol assay for phenol identification. 6 h (a) and 24 h (b).    4 CONCLUSIONS The 4-CP degradation was confirmed by monitoring the absorption band at 298 nm. Additionally, the phenol production was followed by reaction with monochloramine which produces a blue colored solution with maximum absorption at 680 nm. The absorbance decreasing at 298 nm suggest the 4-CP degradation. The small increase of phenol concentration with time suggested that production of other byproducts may occur and be useful for remediation of contaminated water. However this issue requires more investigation.      Brazilian Applied Science Review  Braz. Ap. Sci. Rev, Curitiba, v. 4, n. 6, p. 4013-4021  nov./dez. 2020           ISSN 2595-3621  4019  ACKNOWLEDGEMENTS The authors gratefully acknowledge the Federal Institute Goiano – IF Goiano and Federal University of Triângulo Mineiro – UFTM for providing the laboratories facilities. This research was financially supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico(CNPq) and Fundação de Amparo à Pesquisa do Estado de Goiás (FAPEG).                              Brazilian Applied Science Review  Braz. Ap. Sci. Rev, Curitiba, v. 4, n. 6, p. 4013-4021  nov./dez. 2020           ISSN 2595-3621  4020  REFERENCES  ARRUDA, T. L. et al. Desalogenação Redutiva de Organoclorados utilizando Ferro Elementar. In: - XIV Congresso Brasileiro de Águas Subterrâneas, São Paulo, 2006. Anais.  available in: https://aguassubterraneas.abas.org/asubterraneas/article/view/22227. Acess in: 28 de Nov. 2020.   BINGJUN SUN et al. Core-matched encapsulation of an oleate prodrug into nanostructured lipid carriers with high drug loading capability to facilitate the oral delivery of docetaxel. Colloids and Surfaces B: Biointerfaces, v. 143, p. 47-55, 2016.  DORATHI, P. J. et al. Dechlorination of chlorophenols by zero valent iron impregnated silica, Journal of Environmental Sciences, v. 24, p. 765-773, 2012.  FANG LUO et al. Simultaneous removal of trichloroethylene and hexavalent chromium by green synthesized agarose-Fe nanoparticles hydrogel. Chemical Engineering Journal, v. 294, p. 290-297, 2016.  FENGLIAN FU et al. The use of zero-valent iron for groundwater remediation and wastewater treatment: A review. Journal of Hazardous Materials, v. 267, p. 194-205, 2014.  HWANG, Y. et al. Simple colorimetric assay for dehalogenation reactivity of nanoscale zero-valent iron using 4-chlorophenol. Applied Catalysis B: Environmental, v. 166–167, p. 18-24, 2015.  NUNES, E. S. et al. Characterization of tetraethylene glycol passivated iron nanoparticles. Applied Surface Science, v. 315, p.  337-345, 2014.  O’CARROLL, D. et al. Nanoscale zero valent iron and bimetallic particles for contaminated site remediation, Advances in Water Resources, v. 51, p. 104-122, 2013.  RAJA P. et al. Reductive/oxidative treatment with superior performance relative to oxidative treatment during the degradation of 4-chlorophenol. Applied Catalysis B: Environmental, v. 59, p. 249-257, 2005.  RAYCHOUDHURY, T. et al. Potential of zero valent iron nanoparticles for remediation of environmental organic contaminants in water: a review. Water Science and Technology, v. 68, p. 1425-1439, 2013.   SADHASIVAM, S. et al. Recent advancement in biogenic synthesis of iron nanoparticles. Journal of Molecular Structure, v. 1217, p. 128372, 2020.  TAGHIZADE FIROZJAEE, J. et al. Application of nanotechnology in pesticides removal from aqueous solutions – A review. Int. J. Nanosci. Nanotechnol., v. 14 , p. 43 –56, 2018.  TOSCO, T. et al. Nanoscale zerovalent iron particles for groundwater remediation: a review, Journal of Cleaner Production, v. 77, p. 10-21, 2014.  YAN XU et al. Ag nanoparticle-functionalized ZnO micro-flowers for enhanced photodegradation of herbicide derivatives. Chemical Physics Letters, v. 679, p. 119-126, 2017.  YAN, W. et al. Nanoscale zero-valent iron (nZVI): Aspects of the core-shell structure and reactions with inorganic species in water. Journal of Contaminant Hydrology, v. 118, p. 96-104, 2010. YONGLONG LU et al. Impacts of soil and water pollution on food safety and health risks in China. Environment International, v. 77, p. 5-15, 2015.   Brazilian Applied Science Review  Braz. Ap. Sci. Rev, Curitiba, v. 4, n. 6, p. 4013-4021  nov./dez. 2020           ISSN 2595-3621  4021  ANEXO  HIGHLIGHTS  § Fe-NPs were used for degradation of 4-chorophenol;  § Fe-NPs are composed by α-Fe phase and presented particles size of 113 ± 66 nm;  § Synthesized Fe-NPs showed good catalytic activity.   GRAPHICAL ABSTRACT  

Synthesis  and application of metallic iron nanoparticles on the 4-Chorophenol degradation / Síntese e aplicação de nanopartículas de ferro metálico na degradação do 4-clorofenol

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Synthesis and application of metallic iron nanoparticles on the 4-Chorophenol degradation / Síntese e aplicação de nanopartículas de ferro metálico na degradação do 4-clorofenol

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