## 3 Results and Discussion  
### The Physicochemical Characterization of WRB, GWRB, and Hwrb  
Figure 1 shows the SEM micrographs of waste bricks before and after the deposition of goethite and hematite. As shown in Figure 1a, the WRB exhibited a relative compact appearance with certain grains. After the incorporation of goethite and hematite (Figure 1b,c), the main surface properties of WRB were maintained. Furthermore, new small particles were appeared on the surface of WRB, which revealed the heterogeneity of the iron deposit on the bricks. Table 2 shows the chemical analysis, specific surface area and amount of coated iron oxides on WRB, GWRB, and HWR. The XRF results showed that the main constituent of three bricks was SiO\({}_{2}\), in addition to smaller amount of other oxides, such as Al\({}_{2}\)O\({}_{3}\), iron oxide, CaO, and MgO. These results were consistent with the results reported by others [17]. Furthermore, after the incorporation of goethite and hematite, the main composition nearly unchanged except the slight variations of the oxide contents, which indicated the main structure of brick was not changed. After the digestion by acid, the results showed that the iron content on the GWRB and HWRB is higher than that of WRB. After the calculation, the amount of coated iron on the surface of GWRB and HWRB was 4.28 and 3.41 mg/g, respectively. These results were corresponding to the conclusion shown in the data of XRF. However, after the incorporation of  
geothetic and hematite, the specific surface area of GWRB and HWRB decreased from 17.46 to 8.2 and 2.2 m\({}^{2}\)/g, respectively.  
Figure 1: The SEM images of waste red brick (WRB; **a**), goethite coated waste res brick (GWRB; **b**), and hematite coated waste res brick (HWRB; **c**).  
The XRD results of GWRB and HWRB are shown in Figure 2. The two diagrams obtained for uncoated and coated brick are almost identical and characteristic of quartz. However, the XRD pattern of GWRB shows several well-defined characteristic peaks of (110), (120), (111), (121), and (151) [25], suggesting the existence the goethite structure on the surface of GWRB. The goethite was coated successfully proved by the increase of (110) characteristic peak and the intensity of all other peaks in GWRB. In the same way, the powder XRD pattern of HWRB appears the characteristic peaks of (012), (110), and (024) [26]. The increase of the intensity peaks in this case is associated with the increase quantity of deposited iron oxides on the surface of bricks.  
The FTIR of WRB, GWRB, and HWRB were illustrated in Figure 3. For all three bricks, the bands at 3439, 1090, 820, and 590 cm\({}^{-1}\) could be ascribed to the stretching vibrations of Si-OH, the asymmetric vibrations and symmetric vibrations of Si-O-Si, the symmetric vibrations of Fe-O-Fe, respectively [27; 28]. Compared with results in the WRB, the main peaks of GWRB and HWRB were nearly unchanged, indicating that the incorporation of iron species did not change the main structure of the bricks. However, the intensity peak of Fe-O-Fe increased after the incorporation, suggested that the content of iron oxide on the surface of waste bricks increased.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Sorbents**} & \multicolumn{3}{c}{**Chemical Analysis (Weight \%, X-ray Fluorescence (XRF))**} & \multirow{2}{*}{**Specific Surface**} & \multirow{2}{*}{**Fe Content**} \\ \cline{2-2} \cline{5-7}  & **Si\({}_{2}\)O** & & & & & & \\ \hline WRB & 70.37 & 15.87 & 4.12 & 1.33 & 2.03 & 5.69 & 17.46 & - \\ GWRB & 71.22 & 15.47 & 5.17 & 1.73 & 1.77 & 6.32 & 8.20 & 4.28 \\ HWRB & 69.58 & 15.32 & 5.20 & 1.56 & 1.95 & 7.54 & 2.20 & 3.41 \\ \hline \hline \end{tabular}
\end{table}
Table 2: The chemical analysis, specific surface area and amount of coated iron on the surface of adsorbents.  
Figure 2: The X-ray diffraction patterns of GWRB (**a**) and HWRB (**b**).