*2.6. Deionised Water Properties Measurements and Theoretical Calculation*

Deionised water, of pH 4, 7, and 9, kinematic viscosity and density changes with temperature were characterised at a temperature range from 20 ◦C to 60 ◦C, via an Anton Paar DMA 4500M density meter (Graz, Austria) of accuracy 5 × <sup>10</sup>−<sup>5</sup> g/cm3 and a PAC Herzog HVM 472 multirange viscometer device (Houston, TX, USA), respectively. Both of the aforementioned devices have built-in calibration systems that are initiated before starting the measurements. The variation in pH value, of the DIW's, with temperature was obtained from previously published results [32,33], for pH 7 and 9, and theoretically calculated for pH 4, for the same range of temperatures, using the following equation [34,35]:

$$\text{pH}\_{T} = \text{pH}\_{25} \cdot \text{C} + \text{[} (T - 25 \, ^\circ \text{C}) \times \text{solution temperature coefficient} \text{]} \tag{1}$$

where pH*T*, pH25 ◦<sup>C</sup> and *T* are the solution pH value for an examined temperature, the solution pH value at 25 ◦C, and the examined temperature in Celsius, respectively. The solution temperature coefficient of DIW of pH 4 was selected to be −0.004 pH/◦C, based on the extrapolation of the available data of the two previous DIW's (i.e., pH 7 and 9).
