Green synthesis of BT-Fe3O4 nanocomposite using Camellia sinensis leaves extract Characterization NP

Abstract

Keywords: Adsorption; Black-tea; green synthesis; Magnetite nanocomposite; Nonylphenol ethoxylat

Introduction

According to results of the research conducted by the World Wide Fund for Nature (WWF) and Eurostat, worldwide chemical production has been increasing

exponentially since 1903. In 2017, 97.8 million tons of these chemicals were reported to be harmful to the environment and health [1]. Nonylphenol ethoxylates (NPEO) are

*Corresponding author. *E-mail address: yagmuruysal@gmail.com This paper was recommended for publication in revised form by Regional Editor Nergis Arsu Published by Yıldız Technical University Press, İstanbul, Turkey Copyright 2021, Yıldız Technical University. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/).

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produced approx. 400,000 tons of year worldwide. NPEOs are one of the commonly used nonionic surfactants, and consist of a hydrophobic structure with a hydroxyl group, a phenol ring and a linear nonyl chain in the para position [2]. The increasing industrial demand for NPEOs and their usage in anthropogenic activities have increased their emergence as a contaminant in drainage mud and garbage dump sites due to waste evacuation, water treatment plants, and random dumping [3, 4]. NPEO has been detected in streams at concentration switching from 2.5 to 97.6 μg/L [5] and risk coefficient greater than 1.0 indicating that may pose significant ecotoxicological risks [6]. Nonylphenol (NP) in the medium originates from the degradation of nonylphenol ethoxylates (NPEOs) [7]. According to previous studies, the average NP concentration in sewage sludge used for soil improvement was determined as 24.907 mg/kg [8]. It has been determined that NP concentration in wastewater treatment plants is measured as 0.79 μg/L and this value can reach up to 0.1-1.2 mg/L around contaminated rivers and septic systems [9]. Various studies have shown that NPs can mimic natural estrogens withal the estrogen receiver, thus inhibiting the activity of the hormone, bioaccumulating in aquatic organisms, altering the endogenous levels of steroids, diabetes, reproductive system, and is associated with obesity [4, 10-13]. Consequently, numerous countries have restricted the use of NPEO surface-active agents [14]. The current policy on NP in the European Commission is to ban its use within the European Union through the 2003/53/EC Directive. [15]. Many technologies such as biological, physical, and biotechnological methods have been applied to separate or treat NPEOs from wastewater. Combined methods for adsorption and enhanced oxidation processes (ie. photocatalysis) are attractive as they get the benefit of synergistic impacts [2, 16]. It has been viewed that adsorption is one of the very effective, economic, and effortless methods for contaminant removal. However, the transmission of complexes into the solid phase owing to adsorption can beget a seconder contaminant in water. This issue could be intercepted by adopting an alternative way such as nanomaterials based photo-catalysis [17-19]. Nevertheless, there are few studies on the synthesis of nanomaterials that meet all these criteria. Therefore, green synthesis methods that are environmentally, economically, and technically feasible are needed instead of traditional methods [20]. Nanomaterials produced using herbal phytochemicals notably decrease environmental contaminants, aid economically viable and sustainable neat and green chemistry technologies [21]. The selection of green synthesis routes may conduct significant benefits over the traditional process. For example, traditional processes tend to produce waste (liquid or solid), which often signals the use of costly chemicals and additional investments in the treatment of these pollutants [22-25]. Plant-based nanomaterial synthesis is preferred as

it can be produced from a large number of different natural substances, and powerful biomolecular reducing agents can be obtained from a variety of plants [26]. It has been reported that plants contain a wide variety of antioxidants and secondary metabolites, and these biomolecules work in harmony to inhibit cellular components [27, 28]. Plant extracts contain reducing and stabilizing agents for the synthesis of magnetite nanoparticles such as phenols, carboxylic acid, and amino acids [29, 30]. Black teas within the Camellia sinensis family grow in temperate and tropical areas. The rich source of polyphenols in the structure of black tea leaves acts as a reducing agent in the synthesis of metal nanoparticles [31]. The fundamental goal of this paper is to investigate the potential of green synthesized BT-Fe3O4 composite to adsorb environmentally harmful nonylphenol ethoxylates as adsorbent material. The novelty of this study is to obtain a new magnetite composite material using Black Tea leaves (an eco-friendly stabilizing matter for the synthesis of magnetite materials) so combine these properties in a single substance. Also to our knowledge, preparation, and application of BT-Fe3O4 for NPEO removal in solutions have not yet been studied. Experimental studies were conducted as follows: (1) Characterization of green synthesized BT-Fe3O4 to control the chemical species on the surface of the nanomaterial and the changes in its structure before and after NP adsorption; (2) Batch adsorption experiments performed to optimize various parameters such as pH, nano-dose, initial NPEO concentration and contact time; and (3) Kinetic studies to examine the stability of the adsorption isotherm and the adsorption process.

Materials

NPEO stock solution (1000 mg/L) was prepared from nonylphenol ethoxylate (Acar Chemistry). All chemicals such as NH4OH, FeCl3.6H2O, FeCl2.4H2O, HCI and NaOH (Merck) used in the synthesis of magnetite nano-composites and required for experiments were analytical reagents. Green Synthesis of Magnetite Nanomaterials From Black Tea (Camellia Sinensis) Extract First, the purchased black tea leaves were washed several times with distilled water, to remove dust and dirty and dried. Then tea extract was prepared by boiling 30g/0.5L of the leaves of that plant at 80°C for 1h. After precipitation for 1 h, the extract was filtered. Then a magnetite nanopar-ticle (Fe3O4) solution was prepared by adding 6.1278 g of solid FeCl3.4H2O and 3.0121 g of solid FeCl2.6H2O into 100 mL of deionized water under N2 medium. When the solution temperature reached to 85°C, 25 mL of 25% purity ammonia (NH3) solution was stirred for 2 min. to

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be a homogeneous mixture. Then tea extract was added and the reaction was stirring out in nitrogen for during 30 min and cooled to room temperature. At this time, a black precipitate formed, evidencing the formation of BT-Fe3O4 particles. The BT-Fe3O4 nanoparticles formed were washed several times with distilled water and separated with neodymium magnet [32, 33]. Instrumental Analyzes High-performance liquid chromatography (HPLCShimadzu LC-20AD) equipped with a fluorescence detector was used for measuring of NPEO concentrations. The morphology and size of the resulted BT-Fe3O4 particles were characterized by Field Emission Scanning Electron Microscopy (FE-SEM). Fourier Transformed Infrared Spectroscopy (FT-IR) was realized by FT-IR-410. Batch Studies Batch studies were performed in an orbital shaker with a constant speed of 200 rpm in 100mL flasks. After th at, NPEO solutions were centrifuged (4000 rpm), and the solutions of NPEO in the supernatant solutions were analyzed by using an HPLC. The main process parameters considered were pH (3.0, 5.0, 7.0, 9.0, 11.0), initial NPEO concentration (10, 20, 40, 60, 80 mg/L), nanoparticle dose (1, 2, 4, 6, 8 g/L), and contact time (10, 20, 40, 60, 90 min). For the accuracy of the results obtained, the experiments were repeated twice and their average result reported. The r emoval p ercentage ( %) o f N PEO w as c alculated for as follows each run by using Equation (1)

where C₀ (mg/L) and Ce (mg/L) are the initial and balance concentrations of NPEO.

Results And Discussion Structure Analysis Of Bt-Fe3o4

SEM surface analyses of the BT-Fe3O4 particles before and after the adsorption were used to identify synthesized particles, and were shown in Fig. 1(a-b). Before the adsorption process, nanocomposite particles had an irregular and rough surface (Fig 1a). In Figure 1b, it was observed that after adsorption of NPEO removal, the nanoparticles generally exhibited rough surface morphology and flocculation was dominant. The FTIR spectrum of the nanoparticles produced was also shown in Fig. 2. For raw Fe3O4 spectrum, the peaks at 1593.15 cm−1 and 549.93 cm−1 belonged to the C=C stretching and Fe stretching vibrations, respectively [34]. Before the adsorption process, for BT-Fe3O4, the peaks at 3126.37-2989.71 cm-1 correspond to the stretching vibration of C-H (aliphatic) bending. The peaks at 1605.50 and 1401.63 cm-1 show C=C (aromatic), and C-N bonds, respectively. The peak at 1060.15 cm-1 corresponds to C-O bonds. As shown in Fig. 2, the adsorption peaks at 549.93 cm-1, 1060.15 cm-1 and 1401.63 cm-1 were related with the Fe3O4 nanoparticles coated with black tea. After the adsorption process, the peak at 3369.84 cm-1 for BT-Fe3O4 related to the tension vibration of O-H.

Figure 1. SEM analyses of BT-Fe3O4 before (a) and after adsorption (b) with adsorbed NPEO.

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Adsorption Studies

Effect of PH on the Process The effect of different pH val ues (3.0-11.0 ran ge) on the adsorption processes was given in Fig. 3. According to experimental studies to determine the pH effect on the adsorption process up to 90 min, it was determined that NPEO removal efficiency decreased wi th increasing after p H 7.0. Th is re duction is no t a hi gh re duction. The adsorbent has a high removal efficiency pot ential in the pH range of 3.0-7.0. There was only a slight decrease in removal efficiency at pH 9.0 and above. The maximum NPEO removal efficiency was obtained at pH 4.0 as 74%. Maximum adsorption yield at low pHs can be described as the interplay between the dipole of phenol function in NPEO and the positively charged BT-Fe3O4 surfaces [37]. In addition, low pH which is full of hydrogen ions in NPEO solution, and the effect of the propelling force of dense aromatic bonds (π-π) have led to an increase in hydrogen bond adsorption efficiency [38]. However, in alkaline conditions, the surface of BT-Fe3O4 particles is negatively charged and repulsion takes place between Bt-Fe3O4 and NPEO molecules, and the adsorption efficiency decreases [39]. When the obtained pH results were evaluated, as the adsorbent structure could degrade at low pH [40] and the removal efficiency was almost the same between pH 3.0 and pH 7.0,

Kinetic Models

The impact of time on the removal efficiency of NPEO by BT-Fe3O4 was investigated at various reaction times (10– 90 min). Figure 6 shows that removal efficiency does not change significantly with time. A removal efficiency in the range of 60–70% has been achieved in the first 10 minutes

Kinetic studies are significant for the estimate of optimum conditions in the full-scale adsorption processes [49]. Three different kinetic models were used to determine the time-dependent variation of NPEO adsorption on BT-Fe3O4 and its adsorption rate. In order to study the mechanism of

Isotherm Models

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Table 1. Comparison of the maximum efficiency and adsorption capacities of NPEO on various adsorbents Adsorbent

Pamam-Mnp

Distilled water: 70% Drinking water: 67% Well water: 63% Treated wastewater: 65%

Table 2. The isotherm models and their constants Langmuir Model

qe: amount adsorbed, b: Langmuir constant, Ce: equilibrium concentration qm: monolayer adsorption capacity, Kf and n: Freundlich constants, R: constant, T: temperature, bT and AT: Tempkin isotherm constant, A and B: Harkins-Jura constants.

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Figure 7. The isotherm modeling results of NPEO adsorption by BT-Fe3O4.

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Figure 8. The kinetic modeling results of NPEO adsorption by BT-Fe3O4.

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Table 3. The kinetic models and their constants Pseudo-First Order Kinetic Model k1

the adsorption process, kinetic experiments were carried out at 25°C with a nano-dose of 1 g/L and 10 mg/L NPEO concentration. The adsorption capacities were determined for the adsorption process of 10-90 min. The kinetic parameters and correlation coefficients (R2) were summarized in Table 3 and Fig. 8 (a, b, and c).

Statistical Analysis

The empirical results obtained to explain the statistical significance of the proposed adsorption processes were analyzed using ANOVA (Table 4). ANOVA results are directly related to high F-value and low p-value [50]. F-values of the model as 1014.188 and 372729.78 implies the model is significant for pH and BT-Fe3O4 nano-dose, respectively. The probability that such a large F-value will occur due to noise is only 0.01%. P values smaller than 0.0500 showed that the model terms are meaningful. In this instance, pH and BT-Fe3O4 nano-dose are statistically important parameters. Values larger than 0.1000 showed the models are meaningless and the NPEO concentration is a meaningless parameter.

Conclusion

Black tea leaves and Fe3O4 particles were exposed to a green synthesize by chemical co-precipitation method

to obtain BT-Fe3O4 nanoparticles, and these BT-Fe3O4 particles were applied as an efficient adsorbent for the removal of NPEO from a solution. It showed that the kinetic and isotherm models in NPEO removal fit the so-called second-order kinetic and Freundlich models. These models indicated that the process can occur by chemisorption and occur as a multilayer process. The ideal conditions in this paper were defined as pH 7.0, the contact time of 60 min, NPEO concentration of 10 mg/L, and adsorbent dose of 1.0 g/L. Moreover, the extract of black tea leaves was an efficient candidate for the green synthesis of magnetite nanoparticles. The results of this study showed that BT-Fe3O4 particles eco-friendly, cheap-cost particles for the treatment of NPEO from water and wastewater.

Data Availability Statement

The authors confirm that the data that supports the findings of this study are available within the article. Raw data that support the finding of this study are available from the corresponding author, upon reasonable request.

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Conflict Of Interest

The author declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Ethics

There are no ethical issues with the publication of this manuscript.

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