Nova 3000e surface area analyzer

The bulk density of the samples was calculated as the mass-to-volume ratio, and the presented results are an average of three measurements. The porosity of the cryogels was evaluated by the method reported by Onwukamike et al. [23 (link)], according to the following equation:
where ρ_A is the bulk density and ρ_R is the real density calculated based on the mass fraction of alginate density (1.59 g/cm³). All measurements were performed in triplicate and presented as a mean value. The standard deviation was up to 10%.
The BET surface was measured by the nitrogen adsorption-desorption test which was performed by the means of Nova 3000e surface area analyzer (Quantachrome Instruments, Bointon Beach, FL, USA).

The morphology of the prepared samples was analyzed by FEI Quanta 200 FEG Scanning Electron Microscope (SEM) (FEI Company, Hillsboro, OR, USA) at an accelerating voltage of 5–10 kV. Prior to the SEM analysis, the cryogels were sputtered with gold (~7 nm). The bulk density of the samples was calculated as the mass-to-volume ratio, and the presented results are an average of three measurements. The specific surface area was analyzed by nitrogen adsorption-desorption test (Nova 3000e surface area analyzer, Quantachrome Instruments, Bointon Beach, FL, USA) and mercury porosimetry test (Carlo Erba Porosimeter 2000 equipped with the software Milestone 200, Carlo Erba, Washington, DC, USA). Before the measurements, the samples were degassed at 75 °C for 24 h. The presented results are the average values of 3 measurements; the standard deviation was within 10%.