# Reduction of Water Color in a Spinning Disc Reactor
## 3 Results
### Colored Water Treatment with Selected Adsorptive Materials in SD Experimental Setup
#### 3.1.2 Influence of Disc Rotational Speed on Discoloration for All Tested Adsorbents  
Testing ZnAILDH as an adsorbent in the SD setupThe influence of spinning disc speed when RR-dye-based colored water was treated with ZnAILDH (2 g/L) at four different constant water flow rates of 5.76, 6.00, 7.44 and 8.16 L/h is indicated in Figure 3a-c. As already mentioned above, the highest color removal, in this case, was recorded at 250 rpm and after a 55 min working time period and a low water flow rate (6 L/h).  
Figure 3: Disc rotational speed influence on RR-dye-based water color removal in an SD system with ZnAILDH at constant water flow rates: (**a**) 5.76 L/h, (**b**) 6.00 L/h, (**c**) 7.44 L/h.  
Testing TiO\({}_{2}\) as an adsorbent in the SD setup.The colored water absorbances measured when using TiO\({}_{2}\) to remove RR-dye-based water color at different spinning disc speeds, for different constant water flow rates, is presented in Figure 4, with the largest color removal value registered at 800 rpm.  
Figure 4: Disc rotational speed influence on RR-dye-based water color removal in an SD system with TiO\({}_{2}\) at constant liquid flow rates: (**a**) 5.76 L/h, (**b**) 6.00 L/h, (**c**) 7.44 L/h.  
.1.3 Application of Additional Fenton Oxidation on Colored Water Tested with ZnAILDH in the SD Setup  
In the SD experimental setup, the Fenton oxidation (FO) process in acidic conditions was used on the colored water utilizing different amounts of H2O2 (30%) activated by FeSO4 (stock solution of 0.34 mmol/L) and H2 SO4, which produces hydroxyl radicals (HO-), which are known to have stronger oxidative properties than H2O2. To ensure an acidic pH, H2 SO4 (concentrated and 1N solution) was added. The FO was applied in the working conditions corresponding to the highest color removal values for ZnAILDH, at 6 L/h and 250 rpm, and for TiO2 in the low electric power consumption conditions chosen both for the transport pump and for the motor that drives the disc (i.e., a low water flow rate of 6.00 L/h and disc rotational speed of 250 rpm). The data registered for the two different adsorptive materials in the SD setup in association with FO are presented in Figures 5 and 6, respectively, in comparison to the experimental data obtained in the simple SD configuration at the same working conditions (no FO applied). For ZnAILDH, Figure 5 indicates an increase in the water discoloration when FO was used in the SD configuration, with the maximum value of 62.54% color removal being obtained after a 50 min working time period. For TiO2, the data for the colored water treatment with FO in the SD system indicated a higher discoloration than for the simple SD process in the first 35 min of the working time period. Afterwards, similar discoloration values seemed to be obtained for both the FO in the SD and simple SD systems.  
Figure 5: Comparison of color removal for FO in SD and SD systems at 6 L/h water flow rate and 250 rpm with ZnAILDH as adsorbent.  
Figure 6: Comparison of color removal for FO in SD and SD systems at 6 L/h water flow rate and 250 rpm with TiO2 as adsorbent.