## 3 Results and Discussion  
### Antibacterial Effect of the Employed Ionic Liquids  
The bacterial growth as a function of time in absence of the employed ionic liquids is shown in Figure 1. It is clearly seen, that the bacterial counts increase with time reaching a value of 10\({}^{6}\) after 24 h. Then different doses of ionic liquids were injected to investigate the influence of the employed ionic liquids on the inhibition of the growth of the planktonic bacteria. The effect of the ionic liquids [OH-EMIm]Cl and [EMIm]Cl on the growth of planktonic bacteria was investigated. Figure 2 shows the decay of bacterial counts by increasing the time at different concentrations of the ionic liquid [OH-EMIm]Cl. As shown in Figure 2, at a concentration of 25 ppm the bacterial counts are linearly decreased by time and a complete inhibition of the bacterial growth is achieved after 6 h of injection. By increasing the concentration of the ionic liquid, the degree of bacterial growth inhibition rises and the highest effect was achieved at a concentration of 100 ppm. After 1 hour of injection, only 100 colony/mL was estimated at a concentration of 100 ppm and a complete inhibition was reached after 3 h. The change in the inhibition efficiency of the bacterial growth in the presence  
Figure 1: The counts of aerobic bacteria in the absence of ionic liquids. of different concentration of [OH-EMIm]Cl is presented in Figure 3. The inhibition efficiency of the injected ionic liquids was determined using the following equation:  
\[IE\ (\%)=\frac{\mathit{Bacterial}_{c}-\mathit{Bacterial}_{c\ (inh)}}{\mathit{Bacterial}_{c}}\ \times\ 100\]  
where \(\mathit{Bacterial}_{c}\) and \(\mathit{Bacterial}_{(inh)}\) are the bacterial counts in absence and in the presence of the ionic liquid, respectively. As shown in Figure 3, the inhibition efficiency of the bacterial growth increased as the concentration of the ionic liquid increased. At a concentration of 25 ppm of [OH-EMIm]Clthe inhibition efficiency of the bacterial growth reached 90% in one hour and about 99.9% was attained after three hours. Figure 3: The inhibition efficiency of the bacterial growth in presence of different concentrations of [OH-EMIm]Cl. Figure 2: The decay of bacterial counts with time at different concentrations of the ionic liquid [OH-EMIm]Cl. However, at a concentration of 100 ppm an inhibition efficiency of about 99.99% was obtained in one hour. These results indicate the bactericidal effect of ionic liquid [OH-EMIm]Cl and the inhibition efficiency were dependent the ionic liquid concentration. In general, the antibacterial influence of the ionic liquids is attributed to the attraction of the ionic liquid species to the cell membrane causing its disruption [26]. Figure 4 shows the influence of the ionic liquid [EMIm]Cl on the planktonic bacterial growth. As in the case of [OH-EMIm]Cl, the presence of [EMIm]Cl led to a significant decrease in the bacterial counts with rates dependent on the concentration. However, higher concentrations of [EMIm]Cl are needed compared with those of [OH-EMIm]Cl to achieve comparable inhibition of the bacterial growth. Furthermore, a complete inhibition was not achieved with the duration of the investigation, up to 6 h, in the case of [EMIm]Cl. As shown in Figure 4, a step-like behavior was observed as the ionic liquid concentration increased. This was attributable to the relatively lower rate of the bacterial growth inhibition of the ionic liquid [EMIm]Cl compared to that of the ionic liquid [OH-EMIm]Cl. The inhibition efficiency of the bacterial growth in the presence of different concentrations of [EMIm]Cl as a function of time is displayed in Figure 5. In the presence of ionic liquid concentrations above 50 ppm, an inhibition efficiency close to 99.9% was obtained in one hour. At one and the same concentration, the inhibition efficiency of [OH-EMIm]Clwas significantly higher than that of [EMIm]Cl.