## 3 Results and Discussion
### Adsorption and Catalytic Oxidation Performance of CoPc@s-BC  
The prepared series of CoPc@s-BC were aimed at being functional nanocomposites for the decoloration of dye wastewater. The total decoloration includes the adsorption of dye molecules and the subsequent catalytic oxidation process [40]. The performances of the prepared CoPc@s-BC nanocomposites were firstly evaluated based on their adsorption behavior towards reactive red X-3B dye wastewater (Figure 6). For pure BC, only 0.05 umol of the dye molecules were adsorbed after a dynamic equilibrium, reached in 240 min. CoPc@BC had a much higher adsorption capacity than pure BC--0.2 umol of dye was adsorbed by CoPc@BC under the same experimental conditions. The adsorption capacities of all the spacer-attached nanocomposites were higher when compared with CoPc@BC. After dynamic equilibrium was reached, the amounts of the adsorbed dye by CoPc@DT-BC, CoPc@TT-BC, CoPc@TP-BC and CoPc@PH-BC were 37%, 54%, 67% and 17% higher than that of CoPc@BC, respectively. As illustrated in Figure 5, the contents of immobilized CoPc for CoPc@DT-BC, CoPc@TT-BC, CoPc@TP-BC and CoPc@PH-BC were 27%, 21%, 15% and 7% higher than that of CoPc@BC, respectively. By comparing these statistics, it is easy to deduce that the enhancement of adsorption capacity was mainly caused by the incorporation of spacers. The incorporation of spacers caused CoPc to immobilize onto BC in a more dispersed way, which effectively increased the number of contact opportunities between CoPc and the dye molecules; furthermore, the diffusion limitation of dye molecules to CoPc was effectively reduced. These effects were correlated with the spacer length. CoPc@TP-BC has a longer spacer than CoPc@DT-BC and CoPc@TT-BC, and its adsorption capacity was  
Figure 5: Effect of the glutaraldehyde concentration on the immobilized CoPc and residual spacer content for (**a**) DT-attached BC; (**b**) TT-attached BC; (**c**) TP-attached BC; and (**d**) PH-attached BC, T = 25 \({}^{\circ}\)C, reaction time = 2 h.  
much higher. However, it is possible that when the spacer was too long, a CoPc might have attached onto BC through multiple-bonding, and the peripheral amino groups on CoPc (which was necessary for proton acceptance) [40] may have been excessively consumed; thus the adsorption capacity may have been reduced to some extent. The CoPc@PH-BC has the longest incorporated spacer, while its adsorption capacity was relatively lower than others. To determine the adsorption rate of CoPc@s-BC, the adsorption curves in Figure 6 were regressed using a linear function (within 90 min); the parameters, including the slope and correlation ratio, are presented in Table 2. The amount of adsorbed dye as a function of adsorption time showed a linear trend; all correlation ratios (r) for the CoPc@s-BC nanocomposites were >0.99. The incorporation of spacers greatly facilitated the contact between the CoPc and the dye molecules--all of the CoPc@s-BC had higher adsorption rates than CoPc@BC. The adsorption rate of CoPc@TP-BC reached 0.385 \(\upmu\)mol/min, which was more than two times higher than that of CoPc@BC (0.172 \(\upmu\)mol/min). One of the main concerns for this study was to evaluate the effects of the spacers, especially the spacer length, on the catalytic activity of the CoPc catalyst. All series of CoPc@s-BC were employed for the catalytic oxidation of reactive red X-3B dye wastewater, with H\({}_{2}\)O\({}_{2}\) as an oxidant. The investigation of the influence of spacers on the catalytic oxidation rate revealed similar results to that of adsorption behavior. A control experiment was firstly conducted. H\({}_{2}\)O\({}_{2}\) alone showed almost no decoloration activity--it was difficult to decompose reactive red X-3B with H\({}_{2}\)O\({}_{2}\) without CoPc@s-BC (Figure 7). All of the prepared CoPc@s-BC nanocomposites are able to catalytic decolorize dye wastewater, and the decoloration rate was correlation with the spacer length (Figure 7, inset).