*2.2. Methodology*

### 2.2.1. Synthesis and Characteristic of Si-PANI Sorbent

In situ polymerization of aniline was conducted directly on silica particles with the use of ammonium peroxydisulphate as an oxidation agen<sup>t</sup> at a temperature of 0–2 ◦C. The procedure was described in detail in our previous publications [7,28]. The deposition of polyaniline on silica particles was verified by Raman analysis using a Thermo Scientific DXR confocal Raman microscope with the Omnic 8 software (Thermo Fisher Scientific Madison, Madison, WI, USA). The parameters for analysis of PANI distribution were as follows: excitation laser wavelength 780 nm, filters 780 nm, registered wavenumber range from 200 to 2000 cm<sup>−</sup>1, laser power 10 mW and exposure time to 5 s per point.

Video images of silica and Si-PANI obtained with the use of confocal Raman microscope (50× magnification) were binarized and segmented using Fiji image processing and ImageJ software analysis [29,30]. The dimensions of analyzed beads were calculated on the basis of Feret diameter [31] using GrapPad Prism 5.0 (GrapPad Software, San Diego, CA, USA).

Si-PANI was deprotonated or protonated using 0.1 M methanolic solution of ammonia and HCl, respectively and the obtained sorbents were pre-washed with methanol (5 mL) and water (5 mL) to neutral pH of leakage.
