Microsoft Word - CAN-3183-PB Online Characterization and Application of Nanomaterials (2023) Volume 6 Issue 1 doi: 10.24294/can.v6i1.3183 1 Original Research Article Green synthesis and characterization of iron nanoparticle using ex- tracted bitter guard leaves used as methylene blue removal Thin Phyu Lin1, Kyu Kyu Khaing1, Aung Than Htwe1,2,*, May Thazin Oo1, Su Su Soe Nyunt1 1 Department of Chemistry, Mohnyin University, Mohnyin 01162, Kachin State, Myanmar. E-mail: aungthanhtwe76@gmail.com 2 Department of Chemistry, University of Yangon, Kamaryut 11041, Myanmar. ABSTRACT Zero-valent iron is a moderately reducing reagent that is both non-toxic and affordable. In the present work, iron nanoparticles were synthesized using bitter guard leaf extract (Momordica charantia L.) (BGL-Fe NP). Using leaf sam- ples from bitter protectant extract, iron nanoparticles were synthesized with secondary metabolites such as flavonoids and polyphenols acting as capping and reducing agents. Polyphenols reduce Fe2+/Fe3+ to nanovalent iron or iron nano- particles. Iron nanoparticles were synthesized by reducing iron chloride as a precursor with bitter protective leaf extract in an alkaline environment. The obtained BGL-Fe NPs were calcined for 4 h at various temperatures of 400 C, 500 C, and 600 C. The obtained samples were coded as BGL-Fe NPs-4, BGL-Fe NPs-5, and BGL-Fe NPs-6, respectively. The synthesized BGL-Fe NPs were systematically characterized by XRD, SEM, FTIR, UV-Vis and TG-DTA analysis. The obtained BGL-Fe NPs were then used as an adsorbent to remove the aqueous solution of basic methylene blue (MB) dye. MB concentration was monitored using UV-Vis spectroscopy. Keywords: Iron Nanoparticle; Characterization; Methylene Blue 1. Introduction Momordica charantia L., a member of the Cucurbitaceae family, is also known as bitter guard. Simple or alternating leaves measure 4– 10 cm long and have 3–6 deeply divided lobes. Tendrils can be un- branched or branched. Fruit has an irregular dehiscence as a fleshy capsule or is indehiscent. It is ovoidal, elliptical, or spindle-shaped, packed with flat seeds in pulp, typically with a ridged surface. The fruits are green when they are young and become orange or yellow as they ripen. Numerous studies have reported on the environmentally friendly production of iron nanoparticles using a variety of plant extracts. Iron nanoparticles (Fe NPs) have mostly been biosynthesised utilizing the extract of green tea, a readily available and affordable resource. Mak- ing use of green tea (Camellia sinensis) extract, which contains a num- ber of polyphenols, Hoag et al.[1] synthesized nZVI. The stable nano- particles were created at room temperature without the use of a surfac- tant or polymer. Plant polyphenols function as capping and reducing agents, producing stable, green, zero-valent iron particles with special characteristics. According to Ghanim et al.[2], dye pollutants are one of the prima- ry sources of environmental contamination in a wide range of sectors. There are several ways to clean up wastewater from all industries, in- ARTICLE INFO Received: 4 May 2023 Accepted: 20 May 2023 Available online: 4 June 2023 COPYRIGHT Copyright © 2023 by author(s). Characterization and Application of Nano- materials is published by EnPress Publisher LLC. This work is licensed under the Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0). https://creativecommons.org/licenses/by- nc/4.0/ 2 cluding textile industry effluent. Adsorption is the most often used technique among them since it is efficient and easy to apply[3,4]. In this study, bitter guard leave extracts were successfully used to prepare iron nanoparticles (BGL-Fe NPs). Polyphenols from bitter guard have been found to have capping and reducing properties. It designed an entirely novel synthetic method for sorbent here using green chemistry principles and eco-friendly, cost-effective, non- hazardous, and renewable materials. Modern methods, including XRD, FTIR, UV-visible, SEM, and TG-DTA, were used to analyze the properties of the prepared BGL-Fe NPs. Finally, the main objective of this study is to reveal the efficient adsorptive removal of organic waste, such as the cationic synthetic dye methylene blue, by the syn- thesized BGL-Fe NPs sorbent. 2. Materials and methodology 2.1 Collection and extraction The leaves of bitter guard (Momordica char- antia L.) were collected from Nammar Township, Kachin State, Myanmar, in December 2022. The samples were cut into small pieces and dried in the shade at room temperature for one week. The dried leaves samples were ground with a grinder and stored in airtight bottles. 2.2 Preparation of iron nanoparticle (BGL- Fe NPs) The iron nanoparticles (BGL-Fe NPs) were prepared by the co-precipitation method. Extracts were prepared by heating 20 g of bitter guard leaves powder in 200 mL of distilled water for 30 min at 85 C on a hot plate. The extract was fil- tered using filter paper. FeCl3·6H2O (3.381 g) was dissolved in 250 mL of distilled water and stirred continuously to obtain a 0.1 M Fe(III) solution. The bitter guard leave extract was mixed into a 0.1 M Fe(III) solution for 15 min. The color im- mediately changed after the addition of bitter guard leaves extract to the ferric chloride solution. And then, sodium hydroxide (1M) solution was added drop by drop into the iron(III) mixture solu- tion, which was carried out with constant stirring at 80 ºC until the solution reached pH 8. The color of the solution was changed from brown to red- dish-brown. The solution was continuously stirred at 80 C for 2 h. Then, the solution was centri- fuged at 3,000 rpm for 5 min. The synthesized BGL-Fe NPs were washed several times with dis- tilled water until neutral (pH 7) to remove any alkali metals. The obtained neutral BGL-Fe NPs were washed again with ethanol and dried for 3 h in the oven at 80 C. After that, the dried BGL-Fe NPs were calcinied in a muffle furnace at 400 C, 500 C, and 600 C for 4 h to achieve stable BGL- Fe NPs. This sample was coded BGL-Fe NPs-4 for 400 C, BGL-Fe NPs-5 for 500 C, and BGL- Fe NPs-6 for 600 C. All samples were crushed with a motor and pestle and sieved with a 40- mesh sieve. Finally, the sample was stored in a sealed bottle and placed in a dessicator for further use. The schematic diagram was described in Figure 1. Figure 1. Schematic diagram of preparation of iron nanopar- ticle (BGL-Fe NPs) using bitter guard extract. 2.3 Characterization of iron nanoparticle (BGL-Fe NPs) Green synthesized iron nanoparticles are characterized through different techniques such as XRD, FTIR, SEM, UV-Vis, and TG-DTA to elu- cidate their properties. X-ray diffraction studies were used to determine the prepared powdered samples (varistors) with the help of Rigaku Mul- tiflux X-ray diffractometer with Cu Kα (λ = 1.5418 Å) monochromatic radiation. The pow- dered samples were scanned from 10° to 80° with a scanned speed of 0.01°/sec. The applied voltage and current of the X-ray diffractometer were set to be 50 kV and 40 mA. The identification of func- tional groups was investigated by FT-IR with a 3 Perkin Elmer spectrum of 2,000. The analyses were carried out in the range of 400 cm–1–4,000 cm–1. Nanoparticles powder samples (varistors) were characterized with the assistance of (JEOL, Model No. JSM-5610 LV). Applied voltage and current of SEM were set to be 15 kV, 68 uA, and 94X magnification. 2.4 Adsorption experiment Adsorption by the batch technique was used to study methylene blue (MB) removal using BGL-Fe NPs. First, the accurate MB amount was dissolved in deionized water to make stock solu- tions of MB at a concentration of 50 mg/L. Then, the stock solutions were taken for dilution to make a daily solution. At 25 C, different adsor- bent volumes were mixed with 25 mL of MB so- lution in 100 mL Erlenmeyer flasks. The concen- tration of the solution, contact time, pH of the so- lution, and adsorbent dose are a few important parameters that affect the removal of MB. All concentrations of MB in aqueous solutions were analyzed by the ultraviolet-visible (UV-Vis) method at 668 nm using a GENESYS 10S (Ther- mo Scientific) UV-Vis spectrometer. removal efficiency (%) = 𝐶 –C 𝐶 × 100 % (1) where Ci and Cf are the initial and final concentra- tions of MB (mg/L). 3. Results and discussion 3.1 Characterization The identity of the synthesized iron nanopar- ticles was established using the following analyti- cal techniques: 3.1.1 XRD analysis The X-ray diffractogram of the synthesized BGL-Fe NPs, BGL-Fe NPs-4, BGL-Fe NPs-5, and BGL-Fe NPs-6 (Figure 2) shows the presence of characteristic peaks at 2 values of 30.17 and 57.34 corresponding to hematite (α-Fe2O3), whereas the peak at 35.45 corresponds to mag- netite (Fe3O4). In addition, the peaks at 28.50 correspond to Geothite (α-FeOOH) whereas a peak at 45.32 and 62.89 correspond to zerova- lent iron (α-Fe) phases. It is therefore confirmed that Fe NPs-JF contain zero-valent iron nanoparti- cles (nZVI) along with iron oxides and oxyhy- droxide[5,6]. Using Scherrer’s formula, which is provided below, and the peak broadening profile of the peak at all 2 values, the average crystallite size was estimated using the FWHM value of the most intense peak. d = 0.94λ βcosθ where λ is the wavelength (1.5418 Å) and β is the full width at half maximum (FWHM) of the cor- responding peak[7]. The average crystallite size of synthesized BGL-Fe NPs calculated from Sher- rer’s equation was 47.66 nm for BGL-Fe NPs, 10.55 nm for BGL-Fe NPs-4, 11.33 nm for BGL- Fe NPs-5, 15.72 nm for BGL-Fe NPs-6, respec- tively. Figure 2. XRD pattern of BGL-Fe NPs before and after cal- cination temperature. 3.1.2 FTIR analysis The potential extract functionalities that may have been the cause of the EDX-found carbon signature were determined using FTIR analysis. Several peaks were observed in the range of 1,000–3,400 cm–1. In Figure 3, the iron nanopar- ticles correspond to the vibrations of the Fe-O bonds. The bands at 3,021 cm–1, 1,636 cm–1, 1,440 cm–1, 870 cm–1, and 540 cm–1 were confirmed as OH, C=C, aliphatic C-H bending, C-H bending, FeO stretching. The absorption bands at around 540 cm–1 attributed to the FeO symmetrical 4 (A) (B) (C) Figure 3. Continued. 5 (D) Figure 3. FTIR spectra data of (A) BGL-Fe NPs; (B) BGL-Fe NPs-4; (C) BGL-Fe NPs-5; and (D) BGL-Fe NPs-6. stretching. The highest peaks at 3,359–3,361 cm−1 correspond to polyphenols, showing the greater abundance and noticeable presence of phenolic functional groups for the reduction of Fe3+ to Fe0. Other than that, the more available phenolic groups provide a favorable molecular arrangement for the delocalization of unpaired electrons. So, the leaf extract captured the property of successful scavenging of free radicals. The appearance of a peak at 3,359 cm–1 and a shift to 3,361 cm–1 indi- cate that the phenolic or amine groups of the leaves extract may be involved in the formation of Fe NPs. It can be concluded from the spectra that the polyphenols in the leaves extract were respon- sible for the reduction and stabilization of Fe NPs, which also agrees with the UV-visible analysis[7]. 3.1.3 SEM analysis The morphology and diameter distribution of BGL-Fe NPs are determined by SEM. The SEM images of BGL-Fe NPs are shown in Figure 4(A)–(D) at 10 kV acceleration voltage and 94x magnification. Analysis of SEM images of all na- noparticles of BGL-Fe NPs shows that the nano- particles are agglomerated and tend to form irreg- ular spherical particles on the surface. Aggregated nanoparticles have been shown to have rough sur- faces. Iron nanoparticles are in close contact with each other due to the magnetic properties of iron species. This may be due to the presence of dif- ferent polyphenols in the leaves extract, which can significantly affect the final morphology and size of iron nanoparticles. In Figure 5(A)–(D), size diameter distribu- tions were evaluated by measuring at least 200 particles from SEM micrograph. The results are obtained that the average diameters of the pre- pared nanoparticles are 12.11 μm for BGL-Fe NPs, 12.23 μm for BGL-Fe NPs-4, 16.59 μm for BGL- Fe NPs-5, and 12.53 μm for BGL-Fe NPs-6, re- spectively. According to the size diameter distri- bution histograms, the significant size of BGL-Fe NPs-5 increased among the samples. It indicates that the produced BGL-Fe NPs possess a narrow size distribution. Figure 4. SEM spectra data of (A) BGL-Fe NPs; (B) BGL-Fe NPs-4; (C) BGL-Fe NPs-5; and (D) BGL-Fe NPs-6 and Particle size diameter distribution. 6 Figure 5. Particle size diameter distribution of (A) BGL-Fe NPs; (B) BGL-Fe NPs-4; (C) BGL-Fe NPs-5; and (D) BGL-Fe NPs-6. 3.1.4 UV-Vis analysis UV-vis absorption spectra of iron nanoparti- cles are represented in Figure 6. As seen in Fig- ure 6, the absorption spectra of BGL-Fe NPs na- noparticle peaks were detected at 229 nm and 274 nm for BGL-Fe NPs, 264 nm for BGL-Fe NPs-4, 263 nm for BGL-Fe NPs-5, and 361 nm for BGL- Fe NPs-6, respectively. Therefore, a sharp and relatively narrow absorption between about 229 nm was observed. The absorption spectrum of bitter guard –Fe0 showed a maximum in the range of 216–300 nm, which is identical to the characteristic absorption peak for the reported metallic iron[8]. Figure 6. UV-visible absorbance spectra of BGL-Fe NPs using leaves extract. As seen in Figure 7, BGL-Fe NPs samples give an optical band gap value that shows 4.03 eV for BGL-Fe NPs, 3.98 eV for BGL-Fe NPs-4, 3.83 eV for BGL-Fe NPs-5, and 3.70 eV for BGL-Fe NPs-6, respectively. Due to charge tran- sitions, the absorption decreases and the optical band gap increases. The BGL-Fe NPs prepared in this study are expected to be more useful in pho- tonic and electronic devices. Figure 7. Plots of h Vs (αh)1/2 of BGL-Fe NPs using leaves extract. 3.1.5 TG-DTA analysis The thermogram profiles of the prepared BGL-Fe NPs samples are shown in Figure 8. The thermogram of BGL-Fe NP samples exhibits three 7 stages of noticeable weight loss between 37 °C and 600 °C. The first stage in the temperature range is 37.09 °C to 230 °C, with 20.42% weight loss for BGL-Fe NPs. There is a loss of moisture. In the second stage, the temperature range be- tween 230 °C and 300 °C was observed to cause 10.15% of weight loss for BGL-Fe NPs. This is due to the dehydration of water molecules. One exothermic peak was seen at 291.30 °C in both samples. The third stage is the loss in weight of 2.28% for BGL-Fe NPs, which was observed to take place within the temperature range of 300 °C to 600 °C due to the combustion of some residue. The thermogram of BGL-Fe NPs-4, BGL-Fe NPs-5, and BGL-Fe NPs-6 samples in Figure 8 shows one phase of weight loss between 38 °C and 300 °C. In this temperature range, it was found that the weight loss of 4.14% for BGL-Fe NPs-4, 1.54% for BGL-Fe NPs-5, and 1.47% for BGL-Fe NPs-6, respectively. In this stage, weight loss may be loss of surface water or OH groups adsorbed on the surface of the iron oxide. The broad endothermic peak was observed between 53 °C and 73 °C. This occurrence is due to the oxidation product of FeO. According to the TGDTA analysis, it was demonstrated that there is no appreciable weight loss at 300 °C above, indicating that the prepared samples are thermally stable. Figure 8. TG-DTA thermogram of Fe NPs-L. 3.2 Investigation of the removal percent of methylene blue by iron nanoparticles 3.2.1 Effect of concentration The effect of color concentration of meth- ylene blue dye solution on the adsorption of BGL- Fe NPs, BGL-Fe NPs-4, BGL-Fe NPs-5, and BGL-Fe NPs-6 was studied under the optimized conditions of time and dosage of adsorbents. The concentrations varied from 50 to 250 ppm. Figure 9 showed that the effect of the initial concentra- tion of methylene blue (MB) solution on the ad- sorption of BGL-Fe NPs, BGL-Fe NPs-4, BGL- Fe NPs-5, and BGL-Fe NPs-6. According to Fig- ure 9, it was found that the percent removal was decreased from about 97.52% to 62.73% for all iron nanoparticles. These indicated that the initial MB concentration of Fe BGL-Fe NPs-6 was more effective than that of BGL-Fe NPs. Higher the removal percentages were observed for lower concentrations of MB for BGL-Fe NPs-6. Figure 9. Effect of the initial concentration on the MB sorp- tion process depending on the phase contact time 3 h: BGL- Fe NPs (dosage 0.4 g, pH 7, shaking speed 250 rpm, tem- perature 25 ℃). 3.2.2 Effect of pH Figure 10 shows that the lowest removal ef- ficiency of 78.154% of BGL-Fe NPs, BGL-Fe NPs-4, BGL-Fe NPs-5, and BGL-Fe NPs-6 was recorded at pH = 5 (highly acidic medium). At low pH values, the presence of excess H+ ions on the surface of Fe NPs can compete with the MB cations for adsorption sites, causing an electrostat- ic repulsion[9]. A further increase in pH from 5 to 9 resulted in an enhancement of MB removal effi- ciency from 78.154% to 81.186% for Fe NPs-L (400 °C) and from 80.092% to 82.982% for Fe NPs-F (500 °C). The increase in negatively charged sites (due to OH–) resulting in electrostat- ic attraction and compounds with the cationic dye 8 may be responsible for the finding[10]. An increase in pH value from 5 to 9 resulted in a decrease in MB removal efficiency from 81.16% to 78.154% of BGL-Fe NPs, and 81.468% to 80.092% in BGL-Fe NPs-4, respectively. This result may be due to the corrosion or hydrolysis of Fe0 in alka- line solutions (e.g., pH around 10), leading to the production of iron ions and ferric iron precipitated as iron oxide/hydroxide[11]. These reactions can be described by the following equations (Equations (2)–(4)): Fe0  Fe2+ + 2ē (2) 2Fe0 + O2 + 2H2O  2Fe2+ + 4OH– (3) Fe0 + H2O  Fe2+ + H2 + 2OH– (4) The corrosive results of the BGL-Fe NPs formation might cover the surface of the nanopar- ticles, which hindered electron transport from Fe0 to MB[12]; as a result, the adsorption process slowed down. Similar to this, Fan et al.[13] showed that dye removal by BGL-Fe NPs particles was inefficient under excessively basic or acidic con- ditions but performed in a mildly acidic range. According to Sun et al.[11], the net surface charge of n BGL-Fe NPs particles turned positive when the solution pH was lower than the point of zero charge (pHZPC) of 8.0, which attracted the anionic dye. On the other hand, the adsorbent surface be- comes negatively charged when the solution pH approaches pHZPC, which strengthens the attrac- tion mechanism with cations. Figure 10. Effect of pH on the MB sorption process depend- ing on the phase contact time 3 h: BGL-Fe NPs (dosage 0.4 g, initial concentration 50 ppm, shaking speed 250 rpm, temper- ature 25 °C). 3.2.3 Effect of dosage The efficiency of BGL-Fe NPs, BGL-Fe NPs-4, BGL-Fe NPs-5, and BGL-Fe NPs-6 sorbents in removing MB from a 50 ppm MB so- lution was determined by monitoring the contact time. In the investigations, the color intensities of aliquots were spectrophotometrically measured at specified times using a batch approach. The dos- age, as seen in Figure 11, varied from 0.1 to 0.5 g. The proportion of each adsorbent decreased after 0.4 g, but during the 3 h period, BGL-Fe NPs-6 sorbent removed the highest MB among BGL-Fe NPs, BGL-Fe NPs-4, and BGL-Fe NPs-5 sorbents. Figure 11. Effect of dosage on the MB sorption process de- pending on the phase contact time 3 h: BGL-Fe NPs (initial concentration 50 ppm, pH 7, shaking speed 250 rpm, temper- ature 25 °C). 3.2.4 Effect of time The MB removal efficiency of BGL-Fe NPs, BGL-Fe NPs-4, BGL-Fe NPs-5, and BGL-Fe NPs-6 sorbents was tested against 50 ppm ferric chloride solution by measuring the contact time. The experiments were performed using the batch method, where the color intensity of the aliquots was monitored spectrophotometrically at certain time intervals. Figure 12 showed that the time varied from 1 to 5 h. From Figure 12, it has been observed that the maximum removal of MB dye was achieved at 3 h of reaction with 81.82% BGL-Fe NPs, BGL-Fe NPs-4, BGL-Fe NPs-5, and BGL-Fe NPs-6. From the results, it can be observed that there was decreased in the percent- age of each adsorbent after 3 h, whereas BGL-Fe NPs-6 sorbent was more removal percent of MB than Fe NPs sorbent for investigation time periods. 9 Figure 12. Effect of contact time on the MB sorption process of BGL-Fe NPs (dosage 0.4 g, initial concentration 50 ppm, pH 7, shaking speed 250 rpm, temperature 25 °C). 3.2.5 Effect of temperature Temperature plays an important role in influ- encing the removal efficiency of a MB adsorption process of Fe NPs. The effect of reaction tempera- ture (25, 30, 35, 40 and 45 C) on the removal efficiency using Fe NPs is described in Figure 13. Here, the efficiency of BGL-Fe NPs-4 for MB removal was 98.96, 89.16, 86.38, 81.38, and 77.86% at 25, 30, 35, 40, and 45 C. It is shown that the removal of MB from BGL-Fe NPs-4 was an endothermic process. However, the MB re- moval efficiency of BGL-Fe NPs at 25, 30, 35, 40, and 45 °C was 85.30, 84.95, 84.12, 83.45, and 83.11%. It was suggested that BGL-Fe NPs were less effective than BGL-Fe NPs-6 in removing the MB because the surface of BGL-Fe NP-6 was more covered by iron oxide and iron hydroxide. Thus, the removal efficiency can be improved by increasing the temperature because it promotes the collisions of MB molecules, which in turn leads to more activation energy[14]. Increasing the solution temperature can improve the adsorption efficiency[15,16]: (a) increases the solubility and mobility of MB in the solution, which increases the intra-particle diffusion; (b) reduce the amount of dissolved oxygen in the solution, prevent the oxidation of iron nanoparticles; (c) increase the activation energy, create new adsorption sites, and form a complex reaction surface; and (d) facili- tates the production of a swelling effect within the internal structure of the absorbent, which facili- tates the penetration of molecules into the pores[17]. Figure 13. Effect of contact time on the MB sorption process of BGL-Fe NPs (dosage 0.4 g, initial concentration 50 ppm, pH 7, shaking speed 250 rpm, temperature 25 °C). 4. Conclusion In this research, iron nanoparticles synthe- sized from aqueous bitter guard leave extracts were characterized by modern methods such as XRD, FTIR, SEM, UV-Vis, and TG-DTA. Iron nanoparticles rich in iron oxide/oxhydroxide can be easily prepared using aqueous extracts of bitter guard leaves as reducing and capping agents at different calcination temperatures of 400, 500, and 600 °C for 4 h. Particle morphology and size were investigated using SEM and XRD tech- niques. SEM microscopy of all prepared Fe NPs showed agglomerated clusters. The crystallite size of BGL-Fe NPs was observed to vary from 10.55 nm to 47.66 nm before and after annealing tem- perature. FT IR measurements confirmed the at- tachment of compounds in the extract to iron na- noparticles. Functional groups of phenolic com- pounds can contribute to the formation of metal nanoparticles. From the FT IR spectral data of all BGL-Fe NPs, a strong stretching absorption band of the Fe-O bond at 543.05 cm–1 was observed. According to the results, the functional groups successfully synthesized BGL-Fe NPs. The product of BGL-Fe NPs was confirmed by change of colour and the UV-Vis spectra sur- face Plasmon resonance center at 229 nm. From UV-visible data, the band edge-absorption peak of all Fe NPs is found to be between about 229 nm and 247 nm, and the band gap values are in the range of 4.06 eV to 4.28 eV for Fe NPs-L with changes the calcination temperature. The absorp- tion decreases, and the optical band gap increases due to charge transfer transitions. 10 In TG-DTA thermogram, the total weight loss (%) shows about 32.85% in BGL-Fe NPs before calcination. After calcination, the total weight loss changes in the range between 4.14% and 1.14% for BGL-Fe NPs (400 °C, 500 °C, and 600 °C). It is found that the total weight loss of BGL-Fe NPs after calcination is lower than that of BGL-Fe NPs before calcination. TG-DTA analy- sis demonstrated that there is no appreciable weight loss at 300 C above, indicating that all Fe NPs samples are thermally stable. The prepared BGL-Fe NPs showed promis- ing prospects for MB removal. The removal effi- ciency was found to depend on the test conditions. The optimum removal occurred at pH 7 and 25 C with 0.4 g Fe NP. In addition, the removal effi- ciency increased rapidly after 1 h and then in- creased more slowly, followed by an equilibrium period after 3 h. The removal percentage of BGL- Fe NPs prepared by methylene blue indicator was about 81.18% to 96.53% of the BGL-Fe NPs sample. This study provides convincing evidence that stabilized nanoparticles of BGL-Fe NPs can be used to remove MB from a cationic dye solution, potentially leading to an innovative treatment method that is likely to be more cost-effective and less disruptive to the environment. Author contributions Conceptualization, TPL and ATH; method- ology, TPL; software, ATH; validation, KKK, MTO and SSSN; formal analysis, TPL; investiga- tion, TPL; resources, TPL; data curation, ATH; writing—original draft preparation, MTO, SSSN and ATH; writing—review and editing, ATH; visualization, MTO and KKK; supervision, ATH; project administration, ATH; funding acquisition, ATH. All authors have read and agreed to the published version of the manuscript. Conflict of interest The authors declare no conflict of interest. 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