Spectrum bx 2

The FTIR spectra of raw and pretreated AOW were recorded using a Spectrum BX II (Perkin Elmer, Waltham, MA, USA) spectrometer in the range of 4000–400 cm⁻¹ on 1% KBr pellets with a spectral resolution of 2 cm⁻¹, in order to identify different functional groups and monitor changes occurring at the functional groups level during different conversion processes.

The surface functionalities of the lignin obtained from the [N11H(2OH)][LAC] pretreatment were measured using FTIR spectroscopy (Spectrum BXII, Perkin Elmer Inc., Waltham, MA, USA) with the universal attenuated total reflection (ATR) method. The spectra were recorded with an average accumulation of 16 scans in the 4000–600 cm⁻¹ interval range with a resolution of 4 cm⁻¹.

Then, 5 mL of distilled water, 1.5 mL of sodium carbonate solution (10%), 0.5 mL of extracted sample and 0.5 mL of Folin–Ciocalteu solution where pipette into a 15 mL centrifuge vail. After the samples were kept for 45 min at room temperature in the dark, they were measured at a wavelength of 765 nm (Spectrum BX II, Perkin Elmer, USA). The results have been expressed in gallic acid equivalent. The samples were created in triplicate [27 (link)].

The formation and decomposition of the carboxylate-type precursor were investigated by thermogravimetry (TG) and differential thermal analysis (DTA) using the SDT Q600 thermogravimeter, in air, up to 1000 °C, at 10 °C·min⁻¹ heating rate, using alumina standards. The FT-IR spectra were recorded on KBr pellets containing 1% samples using a Perkin Elmer Spectrum BX II spectrometer, while the XRD patterns were recorded at room temperature using a Bruker D8 Advance diffractometer with CuK_α1 radiation (λ = 1.54060 Å). The Ni/Zn/Co molar ratios were confirmed using Perkin Elmer ICP-OES Optima 5300 DV (Norwalk, CT, USA) after closed-vessel microwave-assisted aqua regia digestion using a Speedwave Xpert system (Berghof, Germany). The specific surface area (SSA) was obtained using the BET model from N₂ adsorption-desorption isotherms recorded at −196 °C by a Sorptomatic 1990 (Thermo Fisher Scientific) instrument. The UV–VIS absorption spectra were recorded using a JASCO V570 UV–VIS-NIR spectrophotometer, equipped with a JASCO ARN-475 absolute reflectivity measurement accessory.

The crystallinity and structure of the ferrite were investigated by X-ray diffraction recorded at room temperature, using a D8 Advance (Bruker, Germany) diffractometer, operating at 40 kV and 40 mA with CuKα radiation (λ = 1.54060 Å).
The formation of ferrite and SiO₂ matrix was monitored using a Spectrum BX II (Perkin Elmer, Waltham, MA, USA) Fourier transform infrared spectrometer on pellets containing 1% sample in KBr.
AFM was performed by a JSPM 4210 (JEOL, Tokio, Japan) scanning probe microscope using NSC15 cantilevers (diamond-coated silicon nitride tips) with a resonant frequency of 325 kHz and a force constant of 40 N/m in tapping mode. The samples were dispersed into ultrapure water and transferred on glass slides by vertical adsorption for 30 s, followed by natural drying. Areas of 2.5 µm × 2.5 µm to 1 µm × 1 µm of dried glass slides were scanned for three different macroscopic sites.
A cryogen-free VSM magnetometer (Cryogenic Ltd., London, UK) was used for the magnetic measurements. The M_S was measured in a high magnetic field up to 10 T, while the magnetic hysteresis loops were performed between −2 and 2 T, at 300 K on samples incorporated in epoxy resin.