# TiO2 Modified Geopolymers for the Photocatalytic Dye Decomposition
## 4 Conclusions  
In this work, the different types of industrial TiO\({}_{2}\) powder were incorporated into the parent geopolymer matrix (GP-P25, GP-CG100 and GP-CG300). The successful incorporation of TiO\({}_{2}\) into the parent geopolymer matrix was demonstrated by the SEM analysis, and the elemental analysis revealed its homogeneous distribution within a sample and its comparable content over different samples. The photo-catalytic activity of materials, corrected by the possible absorption and decomposition of the dye, caused by porous geopolymer structures and UV illumination, respectively, was evaluated based on the Rhodamine B dye decomposition. The GP-CG100 and GP-P25 photocatalysts exhibited a higher photocatalytic activity (\(\approx\)19%) than the GP-CG300 material (11%). While the addition of CG100 and P25 TiO\({}_{2}\) powder leads to an increase in the anatase content of GP-CG100 and GP-P25 materials, the anatase content in GP-CG300 is comparable with the parent GP (see powder XRD). Furthermore, since CG300 has a significantly smaller particle size and higher surface area than the others, the properties of the TiO\({}_{2}\) powder used could affect its interaction with the geopolymer matrix during preparation, which could also influence the photocatalytic performance of the resultant materials. Additionally, the repeated cycles show the good stability of the GP-CG100 photocatalyst. This metkaolin-based geopolymer, with additional TiO\({}_{2}\), represents an alternative environmentally friendly material with an enhanced purifying ability.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Sample** & **k (min\({}^{-1}\))** & **R\({}^{2}\)** \\ \hline P25 & 0.27 & 0.981 \\ \hline GC100 & 0.033 & 0.998 \\ \hline GC300 & 0.029 & 0.999 \\ \hline MM-GP-P25 (parent GP + 3 wt.% of P25) & 0.0012 & 0.990 \\ \hline GP-P25 & 0.0018 & 0.997 \\ \hline GP-CG100 & 0.0017 & 0.996 \\ \hline GP-CG300 & 0.0010 & 0.984 \\ \hline \hline \end{tabular}
\end{table}
Table 5: The pseudo-first-order rate constants for the photodecomposition of the RhB dye.  
**Author Contributions:** Conceptualization, P.K. ([PERSON]) and I.P.; formal analysis, K.M.; investigation, M.N., P.K. ([PERSON]), I.P., K.M., E.C. and K.K.; writing--original draft preparation, M.N., T.H. and P.K. ([PERSON]); writing--review and editing, M.N., P.K. ([PERSON]) and E.C.; supervision, P.K. ([PERSON]). All authors have read and agreed to the published version of the manuscript.  
**Funding:** The financial support from the Grant Agency of Czech Republic (GA CR), project No. 19-11814S is greatly appreciated. The financial support of the Ministry of Education, Youth and Sports of the Czech Republic via projects NANOBIO (Reg. No. CZ.02.1.01/0.0/0.0/17_048/0007421) is acknowledged by [PERSON] and [PERSON]. This work was carried out thanks to the support of the long-term project for the conceptual development of the research organization No. 67985891 and the grant of Specific University Research--grant No. A1_FCHT_2021_006.  
**Data Availability Statement:** Not applicable.  
**Conflicts of Interest:** The authors declare no conflict of interest.  
**Figure A1. The schematic illustration of photocatalysts preparation.**  
**Figure A2. The representative EDS spectra (**a**) for the corresponding SEM image (cutand polished GP-P25 sample) (**b**).**