# Effect of Washing Temperature on Adsorption of Cationic Dyes by Raw Lignocellulosic Biomass
## 3 Results and Discussion  
### Characterization of Materials  
#### 3.1.1 Physical Characterization  
Characterization by Gas Adsorption-Desorption  
The nitrogen adsorption isotherms at 77 K for different biomasses (CC, CW, CH, MPC, MPW, and MPH) are shown in Figure 1, and the pore properties are detailed in Table 1. The adsorption and desorption isotherms for the various raw biosensors changed gradually as the temperature of the wash water decreased for both materials. All biomasses exhibited type V isotherms, according to the IUPAC classification [46; 47], which are characteristic of mesoporous adsorbents. These isotherms indicate low adsorbate/adsorbent interaction and the formation of multilayers at low pressure. For _Maclura pomifera_, the adsorption curves show that the volume of nitrogen adsorbed was significantly greater than that of wild carob, suggesting that _Maclura pomifera_ has a more developed structure. This is confirmed by the results presented in Table 1, which show the significant differences in the textural properties of the two biosorbents.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline
**Biomass** & \begin{tabular}{c} **S\({}_{\rm BET}\)** \\ **(m\({}^{2}\) g\({}^{-1}\))** \\ \end{tabular} & \begin{tabular}{c} **S\({}_{\rm Mic}\)** \\ **(m\({}^{2}\) g\({}^{-1}\))** \\ \end{tabular} & \begin{tabular}{c} **S\({}_{\rm Ext}\)** \\ **(m\({}^{2}\) g\({}^{-1}\))** \\ \end{tabular} & \begin{tabular}{c} **V\({}_{\rm tot}\)** \\ **(ccg\({}^{-1}\))** \\ \end{tabular} & \begin{tabular}{c} **V\({}_{\rm mic}\)** \\ **(ccg\({}^{-1}\))** \\ \end{tabular} & \
\begin{tabular}{c} _V\({}_{\rm mic}\)/V\({}_{\rm rot}\)** \\ **(\%)** \\ \end{tabular} &
\begin{tabular}{c} **D\({}_{\rm P}\) (nm)** \\ **(kJ mol\({}^{-1}\))** \\ \end{tabular} \\ \hline MPC & 237.3 & 166.2 & 71.1 & 0.347 & 0.089 & 24.42 & 6.13 & 4.25 \\ \hline MPW & 234.0 & 157.0 & 77 & 0.332 & 0.081 & 34.37 & 6.35 & 4.10 \\ \hline MPH & 182.4 & 129.8 & 52.6 & 0.215 & 0.074 & 28.60 & 6.34 & 4.10 \\ \hline CC & 79.4 & 61.2 & 18.2 & 0.103 & 0.029 & 28.15 & 5.95 & 4.37 \\ \hline CW & 46.2 & 32.6 & 13.6 & 0.069 & 0.018 & 26.12 & 6.19 & 4.20 \\ \hline CH & 38.0 & 26.7 & 11.3 & 0.061 & 0.017 & 28.07 & 5.31 & 4.90 \\ \hline \end{tabular}
\end{table}
Table 1: Textural characteristics of raw biosorbents by nitrogen gas adsorption.  
The results in Table 1 reveal considerable variability in the specific surface areas and associated pore volumes of the samples examined. The adsorbents derived from Maclura pomifera (MPC, MPW, and MPH) were more porous than those from carob (CC, CW, and CH). Notably, the temperature of the wash water negatively impacted the porosity of the biosorbents. This was likely due to structural degradation at higher temperatures. The data also confirmed the presence of highly developed mesoporosity in the different studied materials. The adsorption energy (E\({}_{0}\)) was comparable across the different examined samples.  
The BET specific surface area of our materials is significantly higher than that of many other biosorbents. Examples include pine cones [10], cockle shells [20], pine bark [48], and crab shell [49], which have specific surface areas of 55.8, 50.95, 26, and 13.4 m\({}^{2}\) g\({}^{-1}\), respectively.  
Characterization by Scanning Electron Microscopy (SEM)  
The microscopic scans of MPC, MPH, CC, and CH are shown in Figure 2, Figure 3, Figure 4, and Figure 5, respectively. Figures 4 and 5 show that, at different magnifications, wild carob possesses a conductive vessel structure perfectly wound into a cylindrical spring. Conversely, the SEM images of MPC and MPH display a smoother morphology, a relatively heterogeneous surface, and the presence of cavities. Observation of the pore structure indicated that washing with hot water affected the structure of the biosorbents. However, it should be noted that the obtained images show merely the surface cavities and the external openings of the macropores.  
Figure 1: N\({}_{2}\) physisorption isotherms of raw biosorbants.  
Figure 2: SEM image of MPC.