## 2 Materials and Methods
### Characterization of Methods  
The attenuated total reflectance (ATR) with the Fourier transform infrared (FTIR) spectra of all samples was recorded using the Bruker TENSOR 27 FTIR spectrophotometer (Ettlingen, Germany). There were 32 scans accumulated in the range of 600-4000 cm\({}^{-1}\). The spectrophotometer was equipped with a diamond crystal. Scanning electron micrographs were collected from Quanta 3D FEG (FEI) (Hillsboro, OR, USA). Prior to the analysis, the samples were coated with a 3-nm thick gold layer. Morphological analysis of the particles of the examined sorbents was carried out by the automated morphology particle size and shape analyzer (Morphologi G3, Malvern) microscope. Before the measurements, the particles of the analyzed samples were dispersed using a sample dispersion unit (SDU) with the following parameters: Injection pressure = 2.0 bar; injection time = 40 ms; settling time = 120 s. The measurements were performed on the 16 cm\({}^{2}\) area. Describing the size and shape of the three-dimensional (3D) particle is a complex issue, particularly in the case of nonspherical or irregular particles [41]. The analysis captures a two- dimensional (2D) image of a 3D particle and calculates various sizes and shape parameters from this 2D image. These parameters allow for quantifying characterization of the particle morphology [34]. The major axis (M\({}_{\text{Ax}}\)) of the 2D projection of the 3D particle passes through the centre of mass (P\({}_{\text{CoM}}\)) of the particle shape at an orientation corresponding to the minimum rotational energy of the shape. The length of the particle (P\({}_{\text{L}}\)) is defined as the longest line between two points on the perimeter of the 2D projection of a particle on the plane projected onto the major axis whereas the particle width (P\({}_{\text{W}}\)) is the longest line between two points on the perimeter of the particle projection projected onto the axis perpendicular to the major axis. Another way to describe the particle size is the circle equivalent diameter (CE\({}_{\text{diam}}\)), \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Kraft Lignin [g]** & **St [g]** & **EGDMA [g]** & **AIBN [g]** & **Yield [\%]** \\ \hline
0 & 4 & 3.8 & 0.18 & 74 \\
1 & 4 & 3.8 & 0.20 & 90 \\
2 & 4 & 3.8 & 0.22 & 83 \\
3 & 4 & 3.8 & 0.24 & 80 \\
4 & 4 & 3.8 & 0.26 & 81 \\
5 & 4 & 3.8 & 0.28 & 87 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Experimental parameters of microspheres synthesis. which is defined as the diameter of a circle with the same area (C\({}_{\rm A}\)) as the projected area of the particle image (P\({}_{\rm A}\)). This is a single number value that gets information about the size and allows comparing the size of two particles with different shapes. Very differently shaped particles may be characterized as identical using only CE\({}_{\rm diam}\) because they have similarly projected 2D areas. Thus, the information about particle shapes is required. Figure S1 presents the 2D sketch of the 3D particle and circles the equivalent idea. The important parameters used for describing the particle morphology are presented in Supplementary Information (SI) (S2.3. Characterization of Methods). The swellability of coefficient B was determined by the equilibrium swelling in acetone, methanol, acetonitrile, chloroform, toluene, THF, and water using the method proposed by [PERSON] and [PERSON] where B is expressed as [42]:  
\[\mathbf{B}=\frac{\boldsymbol{V_{s}}-\boldsymbol{V_{d}}}{\boldsymbol{V_{d}}} \,\times\,\mathbf{100}\% \tag{1}\]  
where \(V_{s}\) is the volume of the copolymer after swelling and \(V_{d}\) is the volume of the dry copolymer. Measurements were made using a semi-permeable membrane tube. One tenth g of the materials was added to the tubes. The tubes were placed in beakers with various solvents (10 mL). Each measurement lasted 30 min. After this time, the volume of materials was examined. The swelling coefficients were calculated according to formula B.