# Graphene Oxide Adsorption Enhanced by Attapulgite to Remove Pb (II) from Aqueous Solution
## 3 Results and Discussion  
### Characterization  
The SEM and TEM images of ATP, GO, and the prepared GO are shown in Figure 2. Figure 2a shows that the purified ATP exhibited a rod-like morphology and a typical fibrous structure and easily aggregated to form clusters. Figure 2b indicates that the GO exhibited a layer structure that was folded at the edges. In addition, many layers were stacked together because the chemical bond between GO layers easily led to aggregation. Figure 2c shows that ATP was uniformly intercalated on the GO surface. The presence of ATP changed the stacking behavior of pure GO, and the presence of GO resulted in the uniform distribution of ATP. The weakening of aggregate stacking and the appearance of homogenization and uniformity increased the surface area of the as-prepared GO considerably, thus producing more adsorption sites to aid in the removal of heavy metals. The results indicated that the ATP and GO were very well mixed. Figure 2d shows that GO exhibited a transparent, thin film structure and that folds were found on the edges, in agreement with the SEM results. It can be observed from the comparison of the TEM images of GO in Figure 2e that ATP was present and uniformly distributed on the GO surface, further indicating successful fabrication of the as-prepared GO composite. That is, a simple hydrothermal reaction can be used to prepare the as-prepared GO composite adsorbent.  
Figure 3 shows the FTIR spectra of GO, ATP, and the as-prepared GO. In the FTIR spectrum of GO, the peaks at 1110 cm\({}^{-1}\), 1400 cm\({}^{-1}\), and 1629 cm\({}^{-1}\) correspond to the C-O-C vibration, C-OH vibration, and C-C vibration, respectively, in the sp\({}^{2}\) hybridized carbon skeleton; the peaks at 1732 cm\({}^{-1}\) and 3149 cm\({}^{-1}\) correspond to the C-O and O-H vibrations in -COOH, further revealing the presence of carboxyl, epoxide, and hydroxyl groups in GO [31]. The FTIR spectrum of ATP indicates that the appearance of the broad peak at 3550 cm\({}^{-1}\)-3616 cm\({}^{-1}\) was due to the stretching vibrations of (Al)O-H and (Mg)O-H, which, however, shifted to lower wavenumbers in the FTIR spectrum of the as-prepared GO, suggesting the existence of hydrogen bonding between ATP and GO. The absorption peaks at 729 cm\({}^{-1}\) and 796 cm\({}^{-1}\) in the FTIR spectra of ATP and the as-prepared GO are attributed to the stretching vibration of Si-O. Evidently, the Si-O in ATP was transferred to the as-prepared GO [32]. Thus, ATP was successfully intercalated onto the GO surface, forming a novel adsorbent for heavy metals.  
Figure 2: Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of (**a**) ATP, (**b**) GO, (**c**) as-prepared GO and TEM images of (**d**) GO and (**e**) as-prepared GO.  
The main chemical compositions are SiO\({}_{2}\), MgO, Al\({}_{2}\)O\({}_{3}\), and contain a certain amount of Fe\({}_{2}\)O\({}_{3}\), CaO, K\({}_{2}\)O, MnO, Na\({}_{2}\)O, and TiO\({}_{2}\), which vary from places of origin [33]. Figure 4 shows the XPS spectra of GO and the prepared GO. By comparing the XPS spectrum of GO with that of the as-prepared GO, the peaks of Mg 2p, Al 2p, and Si 2p appeared at 54 eV, 78 eV, and 104 eV, respectively, in the spectrum of the as-prepared GO, indicating that ATP, a material rich in magnesium aluminum phyllosilicate, can form a composite adsorbent with GO. The elemental compositions of GO revealed the presence of C and O; however, for the as-prepared GO, in addition to C and O, the presence of Mg, Al, Si, Ca, and Fe further suggests that the reaction combined ATP and GO, thus forming a novel composite adsorption material.