## 3 Results and Discussion
### Removal of Basic Blue Properties
#### 3.2.3 Effect of Removal Temperatures  
The removal process of BB-41, by different solids, was found to be an endothermic process or an exothermic process and the removal efficiency values depended on the temperature values [33; 61; 62].  
Figure 5: Effect of the initial concentrations (C\({}_{\rm i}\)) of BB-41 on the removal percentage (%) and the removed amount (mg/g) using (a, a’) Med-WB and (b, b’) Jed-WB.  
Figure 6: Effect of the used WB mass on the removal percentage of BB-41, (**a**) Med-WB and (**b**) Jed-WB.  
The effect of the temperature has to be examined case by case. In this study, the amount of removed BB-41 was improved by increasing the temperature values for the Med-WB and Jed-WB. A maximum of 60 mg/g was reached for Med-WB, while, a lesser value of 35 mg/g were achieved in the case of the Jed-WB at the same temperature of 60 \({}^{\circ}\)C. These findings confirmed that the removal process was an endothermic process and the temperature effect was noticed clearly for Med-WB rather than for Jed-WB.  
The thermodynamic parameters, such as standard Gibbs energy change (\(\Delta\)G\({}^{\circ}\)), enthalpy change (\(\Delta\)H\({}^{\circ}\)), and entropy change (\(\Delta\)S\({}^{\circ}\)) are summarized in Table 3 and were determined as reported in a previous work [19]. These parameters provide further details on the spontaneity, feasibility, and sorbate-sorbent interactions during the of BB-41 removal process.  
The negative vales of \(\Delta\)G\({}^{\circ}\) increased as temperature increased from 303 to 333 K, suggesting an improved feasibility and spontaneity of the BB-41-waste brick system at elevated temperatures. The increase of \(\Delta\)G\({}^{\circ}\) for Med-WB was more important compared to the BB-41-jed-W. This difference could be related to the distribution of the removal sites on the waste surfaces. The positive value of \(\Delta\)S\({}^{\circ}\) showed that the removal process of BB-41 onto waste bricks was enhanced due to an increase in the degree of disorderliness at the sorbate-sorbent interface [63]. The values of \(\Delta\)S\({}^{\circ}\) were higher in the case of Med-W compared to the Jed-W, due to the higher amount of BB-41 accompanied with the higher mobility of the removed molecules on the surface [64]. The positive value of the heat of adsorption, \(\Delta\)H\({}^{\circ}\), indicated that the process of adsorption was endothermic in nature, hence the amount of BB-41 removed by the waste bricks in the aqueous solution was favored at a higher temperature. This is in agreement with the results listed in Table 3. The value of \(\Delta\)H\({}^{\circ}\) indicates the mechanism of adsorption to be either physisorption, when \(\Delta\)H\({}^{\circ}\) is between 2.1 to 20.9 kJ mol\({}^{-1}\), or chemisorption, when \(\Delta\)H\({}^{\circ}\) is between 80 to 200 kJ mol\({}^{-1}\)[65; 66]. From Table 3, the estimated value of \(\Delta\)H\({}^{\circ}\) lies between 51 to 135 kJ mol\({}^{-1}\), suggesting that the mechanism of interaction between BB-41 and waste bricks in water is mainly governed by the ion exchange process and the chemisorption process [67].