Data on the removal of Optilan Blue dye from aqueous media using starch-coated green synthesized magnetite nanoparticles

In this data article, we present supplementary data related to the research article entitled “Starch-coated green synthesized magnetite nanoparticles for removal of textile dye Optilan Blue from aqueous media” Stan et al., 2019. Data interpretations are included in the related research article Stan et al., 2019. The synthesized starch-coated Fe3O4 nanoparticles (ST-coated Fe3O4 NPs) were analyzed by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) to illustrate the shape and surface coating of nanoparticles. Moreover, the Brunauer-Emmett-Teller (BET) technique was used to evidence starch deposition on magnetite nanoparticles. The obtained nanocomposites were used for adsorption of Optilan Blue (OB) in batch conditions and the optimum agitation speed and point of zero charge (pHpzc) were established. After OB adsorption on ST-coated Fe3O4 NPs, the nanocomposites were analyzed by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). The stability of starch coated Fe3O4 NPs in the acidic as well as alkaline pH was also evidenced by FTIR spectroscopy. In addition, to test the stability of ST-coated Fe3O4 NPs, leaching experiments were carried out. The experimental data were compared with isotherm and kinetic models in order to determine the most suitable for fitting.

were analyzed by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) to illustrate the shape and surface coating of nanoparticles. Moreover, the Brunauer-Emmett-Teller (BET) technique was used to evidence starch deposition on magnetite nanoparticles. The obtained nanocomposites were used for adsorption of Optilan Blue (OB) in batch conditions and the optimum agitation speed and point of zero charge (pH pzc ) were established. After OB adsorption on STcoated Fe 3 O 4 NPs, the nanocomposites were analyzed by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR

Value of the data
The starch-coated green synthesized magnetite nanoparticles exhibit a relatively good ability for dye adsorption, show good stability, and can be easily removed from aqueous solutions by magnetic separation. The isotherms and kinetics fitting data will be useful for predicting and modeling the adsorption capacity and mechanism of OB removal by the ST-coated Fe 3 O 4 NPs. The data obtained show that ST-coated Fe 3 O 4 NPs can be used as efficient adsorbents for removal of the OB textile dye from aqueous media. used for dye removal in Table 2. Fig. 1 shows the SEM images of ST-coated Fe 3 O 4 NPs, and the HRTEM images of two nanocomposite samples are illustrated in Fig. 2. The nitrogen adsorptiondesorption isotherms and pore radius for Fe 3 O 4 sample before and after starch coating are depicted in Fig. 3.  TEM, XRD, FTIR and VSM analyses of nanocomposites after OB adsorption are presented in Figs. 4e8. FTIR analysis was employed to demonstrate the stability of adsorbents in the acidic as well as alkaline media and the spectroscopic evidences are shown in Fig. 9.
The effect of agitation speed on OB removal is presented in Fig. 10. The pH pzc values for all adsorbents are determined by the position where the resulting curves cut through the pH initial axis as observed in Fig. 11. Data from leaching experiments, carried out in order to establish complete magnetic separation and the total dissolved iron concentrations by ICP-OES analysis, are shown in Fig. 12. As illustrated in Fig. 13 and Fig. 14, adsorption isotherms and kinetics were modeled and fitted with experimental data in order to determine the interactions that occur between the adsorbent and adsorbate species, the adsorption rate by the adsorbent, and the adsorption mechanism of the solute onto an adsorbent.

Determination of pH pzc of ST-coated Fe 3 O 4 NPs
The pH drift method [11] was used to determine the pH at point of zero charge (pH zpc ) of the adsorbents under study. Over 12 mg of adsorbent, 20 mL of 0.01 M NaCl solution was added with the initially pH adjusted in the range of 2e12 by adding 0.5 N HCl or 5% NH 4 OH. The mixtures were left at room temperature for 48 h, after which the solid material was separated from the solution using an external magnet and the final pH value was measured.

Adsorption experiments
Optilan Blue adsorption on ST-coated Fe 3 O 4 NPs was performed under batch conditions. The effect of initial dye concentration, pH, temperature and adsorbent dosage on adsorption of OB on ST-coated Fe 3 O 4 NPs were determined. In addition, a study was conducted to determine the optimum agitation speed (100e500 rpm) at which the maximum dye adsorption was accomplished. The solution was adjusted with 0.5 N HCl or 5% NH 4 OH in order to achieve the desired pH. The adsorbent was separated using an external magnet and the residual dye was measured with a  UVeVis spectrophotometer, recording the absorbance at 629 nm. The obtained experimental data were fitted to different models in order to understand the adsorption behavior of OB on ST-coated Fe 3 O 4 NPs.
In addition, the stability of adsorbents in acidic (pH 2) and alkaline (pH 10) media was investigated.

Characterization and analysis
The surface morphology of nanocomposites was examined from SEM and HRTEM images. BET measurements were also conducted, and evidenced the deposition of starch on the surfaces of magnetite nanoparticles.  The stability of adsorbents was investigated in the acidic pH (2) as well as alkaline pH (10) by FTIR technique in order to underline the possible spectroscopic evidences.
After OB adsorption on ST-coated Fe 3 O 4 NPs, the dried samples were characterized by different techniques such as FTIR, XRD, TEM, and VSM.

Batch leaching test
For each leaching test, 10 mg of ST-coated Fe 3 O 4 NPs were mixed with 10 mL of water at pH 2 (HCl 0.1 M) in a 20 mL conical flask. The mixture was stirred with 500 rpm for 2 hours at different temperature (25 C, 35 C and 45 C). The nanoparticles were separated using an external magnet and the leachate samples were analyzed by a dual viewing inductively coupled plasma optical emission spectrometer (ICP-OES). The experiment was performed in triplicate.   Adsorption rate curves (pH 2, dye conc. 50 mg L À1 , 308 K and adsorbent dose 0.6 g L À1 ).