Magnetic Activated Carbon from ZnCl[sub.2] and FeCl[sub.3] Coactivation of Lotus Seedpod: One-Pot Preparation, Characterization, and Catalytic Activity towards Robust Degradation of Acid Orange 10

Lotus seedpods (LSPs) are an abundant and underutilized agricultural residue discarded from lotus seed production. In this study, ZnCl[sub.2] and FeCl[sub.3] coactivation of LSP for one-pot preparation of magnetic activated carbon (MAC) was explored for the first time. X-ray diffraction (XRD) results showed that Fe[sub.3]O[sub.4], Fe[sup.0], and ZnO crystals were formed in the LSP-derived carbon matrix. Notably, transmission electron microscopy (TEM) images showed that the shapes of these components consisted of not only nanoparticles but also nanowires. Fe and Zn contents in MAC determined by atomic absorption spectroscopy (AAS) were 6.89 and 3.94 wt%, respectively. Moreover, S[sub.BET] and V[sub.total] of MAC prepared by coactivation with ZnCl[sub.2] and FeCl[sub.3] were 1080m[sup.2]/g and 0.51cm[sup.3]/g, which were much higher than those prepared by single activation with FeCl[sub.3] (274m[sup.2]/g and 0.14cm[sup.3]/g) or ZnCl[sub.2] (369m[sup.2]/g and 0.21cm[sup.3]/g). MAC was subsequently applied as an oxidation catalyst for Fenton-like degradation of acid orange 10 (AO10). As a result, 0.20g/L MAC could partially remove AO10 (100ppm) with an adsorption capacity of 78.4mg/g at pH 3.0. When 350ppm H[sub.2]O[sub.2] was further added, AO10 was decolorized rapidly, nearly complete within 30min, and 66% of the COD was removed in 120min. The potent catalytic performance of MAC might come from the synergistic effect of Fe[sup.0] and Fe[sub.3]O[sub.4] nanocrystals in the porous carbon support. MAC also demonstrated effective stability and reusability after five consecutive cycles, when total AO10 removal at 20min of H[sub.2]O[sub.2] addition slightly decreased from 93.9±0.9% to 86.3±0.8% and minimal iron leaching of 1.14 to 1.19mg/L was detected. Interestingly, the MAC catalyst with a saturation magnetization of 3.6emu/g was easily separated from the treated mixture for the next cycle. Overall, these findings demonstrate that magnetic activated carbon prepared from ZnCl[sub.2] and FeCl[sub.3] coactivation of lotus seedpod waste can be a low-cost catalyst for rapid degradation of acid orange 10.