The FESEM images of the prepared Zn-AC at different magnifications are shown in Figure 1. It can be seen from Figure 1 that the Zn-AC has macro-pores with different size and round shape, and the external surface of ZnCl2 treated activated carbon (Zn-AC) is full of cavities. Although, the reason for the formation of the cavities on the chemically activated carbon is not clear, it seems that the cavities resulted from the evaporation of ZnCl2 used for activation during carbonization, leaving the space previously occupied by ZnCl2 as the activating agent (Kula et al. 2008; Timur et al. 2010). Since few numbers of macro-pores are present on the outer surface of an activated carbon, the great development of macro-pores is very important, because it has been reported in the literature (Pastor-Villegas et al. 2006) that macro-pore structure can serve as a passage for an adsorbate to reach meso and micro-pores of the activated carbon adsorbent. The pores and cavities of the Zn-AC provide good possibility for TC to be adsorbed, as demonstrated in the next sections. The amount of C, H, N, S, and O elements in the composition of the activated carbon is presented in Table 2. The specific surface area of the Zn-AC calculated according to BET method was found to be 224 m2 g−1. The XRD pattern of the Zn-AC is shown in Figure 2. The characteristic peaks of activated carbon observed at 2θ = 24° and 2θ = 42° correspond to the reflections of the (002) and (100) planes, respectively, confirming that the Zn-AC activated carbon is in an amorphous state (Jache et al. 2012; Shang et al. 2015).
Quantitative results of CHNS-O analysis of the Zn-AC