## 3 Results and Discussion
### Morphology of Egdma + St + lignin Microspheres  
Figure 5 shows the pictures of the obtained sorbents. The SEM pictures confirmed the spherical shape of molecules. For the free-lignin copolymer the highest circle equivalent diameter is observed. The increase of the lignin amount in the sample includes the reduction of diameter. The diameter reduction based on the added value of lignin was confirmed in Figure 5. The EgDMA + St copolymer  
Figure 4: Attenuated Total Reflectance/Fourier Transform Infrared spectra of lignin and copolymers. is characterized by the highest surface homogeneity, with the addition of lignin reducing this feature (more irregularity), which is visible on the surface of microspheres. The analysis of SEM images shows that the sorbent with the highest lignin content (5 g) contains agglomerates (Figure 5f). The sorbent with 4 g of lignin was chosen as the representative material for the carbonization process due to its homogeneous particles (Figure 5e). The exact quantitative description of the parameters was made using the optical microscopy measurements: Morphology G3 particle size and shape analyzer. The obtained results confirm the conclusions drawn from the SEM pictures. Table 3 shows the results of morphological characterization of sorbents. The microsphere diameter for EGDMA-St copolymers is approximately 130 \(\upmu\)m, while after adding lignin it decreases within 28-53 \(\upmu\)m. Analyzing the given parameters, it was found that the  
Figure 5: SEM images of the obtained microspheres. The scale bar is the same for all images. (**a**) EGDMA + St, (**b**) EGDMA + ST + 1L, (**c**) EGDMA + St + 2L, (**d**) EGDMA + St + 3L, (**e**) EGDMA + St + 4L, (**f**) EGDMA + St + 5L. free-lignin sorbent is characterized by the highest parameter of the circle equivalent diameter (CE\({}_{\text{diam}}\)), circularity (C), and elongation (E). The more lignin in the sample, the roughness increases or the value of the parameter indicates the solidity (S). The EGDMA + St + 5L copolymer has the highest elongation parameter, which indicates that this system is inhomogeneous. Although the system with 4 g of lignin is a polymer with a high content of biopolymer, it still retains a spherical form of the particle. This fact made the EGDMA + St + 4L sorbent the most promising material for the carbonization process. For the systems EGDMA + St + 4L-C (Figure 6a), EGDMA + St + 4L-P1 (Figure 6b), EGDMA + St + 4L-N (Figure 6c), and EGDMA + St + 4L-Ag (Figure 6d), the microspheres have retained their sphericity. For the rest of the systems, the microspheres have not kept their original spherical shape. The particles were stuck together and agglomerated. Figure 7 shows the distributions of diameters of the analyzed polymers. The particles of the sample EGDMA-St (without lignin) have a higher value of CE diameter. The presence of lignin in the polymers reduces the microspheres diameter. The morphological characterization of sorbents parameters is shown in Table 3. The material of the largest grain size is the initial material EGDMA + \begin{table}
\begin{tabular}{c c c c c} \hline  & **CE\({}_{\text{diam}}\) \(\pm\) SD [\(\mu\)m]** & **C \(\pm\) SD** & **E \(\pm\) SD** & **S \(\pm\) SD** \\ \hline EGDMA + St & 130.79 \(\pm\) 48.30 & 0.996 \(\pm\) 0.003 & 0.006 \(\pm\) 0.012 & 1.000 \(\pm\) 0.003 \\ EGDMA + St + 1L & 52.66 \(\pm\) 32.44 & 0.992 \(\pm\) 0.005 & 0.021 \(\pm\) 0.023 & 0.999 \(\pm\) 0.002 \\ EGDMA + St + 2L & 41.86 \(\pm\) 20.29 & 0.992 \(\pm\) 0.005 & 0.023 \(\pm\) 0.024 & 0.999 \(\pm\) 0.002 \\ EGDMA + St + 3L & 30.87 \(\pm\) 9.33 & 0.987 \(\pm\) 0.004 & 0.047 \(\pm\) 0.032 & 0.998 \(\pm\) 0.002 \\ EGDMA + St + 4L & 43.25 \(\pm\) 23.80 & 0.990 \(\pm\) 0.005 & 0.034 \(\pm\) 0.029 & 0.998 \(\pm\) 0.002 \\ EGDMA + St + 5L & 27.91 \(\pm\) 15.54 & 0.990 \(\pm\) 0.005 & 0.037 \(\pm\) 0.029 & 0.999 \(\pm\) 0.002 \\ \hline \end{tabular}
\end{table} 
Table 3: Morphological characterization of sorbents. Figure 6: Morphology of carbonized microspheres. The scale bar is the same for all images.