# TiO2 Modified Geopolymers for the Photocatalytic Dye Decomposition
## 3 Results and Discussion  
### Characterization of the Studied Materials  
The chemical composition (the average of the three measurements) of the raw materials (Mefisto L05 and BFS) is shown in Table 1. The chemical composition of the clay material Mefisto L05 agrees with the data of the supplier, CLUZ a.s., (Nove Straseci). This material has a high content of silica and alumina (52.34 and 41.54 wt.%, respectively). The main components of BFS are calcium oxide (39.78 wt.%), silica (20.79 wt.%), alumina (7.36 wt.%) and sulfur trioxide (10.11 wt.%). The results of particle-size distribution presented in Table 2 demonstrate that the clay material Mefisto L05 has very fine particles, with sizes below 25 \(\upmu\)m (d\({}_{50}\) = 3.94 \(\upmu\)m). In comparison, BFS has larger particles, with sizes below 45 \(\upmu\)m (d\({}_{50}\) = 5.01 \(\upmu\)m). The results of the chemical analysis (XRF) of TiO\({}_{2}\) powder, presented in Table 3, show the difference between the manufacturing in Precheza a.s. and Evonik Industries AG. Based on the residual content of Cl (0.12 wt.% in P25), it was confirmed that TiO\({}_{2}\) P25 is produced by a TiCl\({}_{4}\) vapor-fed flame pyrolysis process [55]. On the other hand, CG100 and CG300 contain a residual amount of SO\({}_{3}\) (1.36 and 1.22 wt.% in CG100 and CG300, respectively), which proves their manufacture by a sulfate technology [56]. The total content of TiO\({}_{2}\) in CG100, CG300 and P25 is 93.49, 91.19 and 97.62 wt.%, respectively. The lowest LOI was observed for P25, which could be caused by the method of manufacturing. Powder X-ray diffraction patterns of the starting TiO\({}_{2}\) are shown in Figure 1. Pure CG100 and CG300 contain only anatase, P25 contains approximately 87 wt.% of anatase and 13 wt.% of rutile, which agrees with the data of the producers. Crystallite sizes computed by the Scherrer equation are 18 nm, 6 nm and 20 nm for GC100, GC300 and P25, respectively, which is in good agreement with the average size of the particles provided by the producers (see Table 4). We have also characterized the TiO\({}_{2}\) particle-size distribution that could occur in a water colloid during sample preparation by dynamic light scattering. It is clear from Figure 2 that TiO\({}_{2}\) forms agglomerates with the average particle size in the ranges of 150-350 nm and 720-1700 nm, depending on the TiO\({}_{2}\) powder type. These results are comparable with the literature data where the authors dispersed TiO\({}_{2}\) in water--see, e.g., [57; 58]. To determine the content and distribution of TiO\({}_{2}\) in the incorporated samples, two different routes were followed. The first was an analysis of a cut and polished piece in four different places of the identical cut. The elemental analysis shows a comparable content of titanium in all samples treated with the different types of titanium dioxides and its homogeneous distribution within the sample (see Table 2 and also Figure 2 in Appendix A for the representative EDS spectra and SEM image and Table 6). The other route was an analysis of milled materials as an alternative (more relevant to our experiment) pre-analysis preparation. To avoid the problem of the electron penetration depth being comparable to grain size, the ratio of the analyte signal (Ti) to the cumulative signal of (Al+Si) was used for seven different grains. This proved the homogeneity of Ti dispersion over the different grains (see Figure 3) and at the same time the comparable Ti content in the different incorporated samples. Furthermore, Figure 4 shows the representative SEM image for GP-P25, with the average particle size of this sample being \(\approx\) 500-600 nm. Agglomerates of P25 TiO\({}_{2}\) powder with the average particle size \(\approx\) 1\(\upmu\)m, present in a water  
Figure 1: Powder X-ray diffraction patterns of the starting TiO\({}_{2}\). Figure 2: The distribution of the hydrodynamic diameter of the three types of industrial TiO\({}_{2}\) powder during dispersion in water.