2.5 Characterizations
Scanning electron microscopy (SEM) was performed on a Hitachi FE-SEM SU8200 instrument (Japan). Thermogravimetric analysis (TGA) was performed on a TGA 550 instrument (TA Instruments, USA) at 20-800°C under N2 atmosphere using a heating rate of 20°C/min. The FTIR spectra of the MD and OSMD samples were measured using Nicolet iS50 FT-IR (Thermo Scientific, USA). Spectra were taken from 4000 to 400 cm−1 and the resolution of the wavenumber was 2 cm−1. XPS of raw diatomite and OSMD was carried out by ESCALAB250Xi (Thermo Scientific, USA). The magnetization of the immobilized enzyme was carried out by Lake Shore VSM 7307 (Lake Shore, USA). N2 adsorption and desorption study was performed on the ASAP 2020Plus HD88 (Micromeritics, USA). Water contact angle measurement of the samples was measured with a KRUSS drop shape analyzer DSA 100 instrument at 25°C for the support and the injecting syringe as well.