Avatar 360

The chemical structure of BC was analyzed using FTIR. The BC material was dried at 60 °C for 24 h. A small amount of BC material was evenly mixed with KBr particles and ground into a fine powder, then placed in the mold and pressed into a tablet. A Fourier infrared spectrometer (Avatar360, Thermo Nicolet, Madison, WI, USA) was used for spectral scanning in the range of 400–4000 cm⁻¹.
Deuterated formic acid-D₂ (D, 98%) (<5% D₂O) (Cambridge Isotope Laboratories, Inc., Tewksbury, MA, USA) was used as the deuterium solvent. The dried BC (10 mg) was dissolved in 500 μL of deuterated formic acid and transferred into an NMR tube, after complete dissolution at room temperature. The ¹H NMR of the BC was obtained using an NMR spectrometer (VANCE III600, Bruker, Karlsruhe, Germany). The NMR spectrum was analyzed using MestReNova software (14.2.0).
The BC material was fully dried at 60 °C and the C, H, and N contents were determined using elemental analysis (FLASH EA1112, Thermo Electron SPA, Waltham, MA, USA).

Fourier transform infrared (FTIR) spectra of the RCW before and after Cd accumulation were acquired using an FTIR spectrometer (Thermo Nicolet Avatar 360, Quebec City, QC, Canada). Two-milligram root samples were ground with 200 mg of potassium bromide (KBr, Damao Chemical Reagent Co., Ltd., Tianjin, China) in an agate mortar until KBr powder adhered to the mortar wall when the particle diameter was approximately 2 μM (diameter 13 mm). The functional groups involved in metal ion biosorption in the RCW were obtained within the range of 400–4000 cm⁻¹.

A field emission scanning electron microscope (FESEM) (Crossbeam 340, Zeiss, Birmingham, UK) was used to study the surface morphology and cross-sectional structure of the PAN/PPSU substrate as well as the TFC membrane at different magnifications. Fourier transmission Infrared spectroscope-attenuated total reflectance (FTIR-ATR) (Avatar 360, Thermo Nicolet, Thermo Fisher Scientific, Waltham, MA, USA) was utilized to identify the functional groups of the substrate and PA-selective layer. Each FTIR spectrum was collected between 4000 and 500 cm⁻¹ and the results were the average of 32 scans. The Omnic software was used to process acquired data. An atomic force microscope (AFM) (NX10, Park Systems, Suwon, Republic of Korea) was utilized to obtain the mean roughness of the membrane at a scan area of 10 μm × 10 μm. The surface hydrophilicity meanwhile was measured using a contact angle (CA) goniometer (OCA 15Pro, DataPhysics, Filderstadt, Germany). The volume of pure water dosing was fixed at 0.3 μL when it was dropped on a dried membrane surface.

The IR spectra were recorded on a Fourier-transform IR (FT–IR) spectrometer (Avatar360) that was equipped with an IR microscope (Continuum) (Thermofisher Scientific, MA). The 25 × 25 µm area was measured. Each spectrum was measured by a  1024-accumulation cycle at a spectral resolution of 4 cm⁻¹. A pellet of the fibrils, which was prepared via centrifugation was soaked in the buffer solution before it was sandwiched in two CaF₂ windows. The IR spectrum was measured for the pelleted particles while they were still wet. A reference sample containing the solvent was also measured at a spot that was in proximity to the pellet.