Microwave plasma torch synthesis of Zn Al oxides as adsorbent and photocatalyst for organic compounds removal

摘要： Zn-Al based oxides were synthesized using a microwave plasma torch (MPT) in which the precursors were introduced into the reaction chamber either upstream or downstream of the inlet, respectively. Zn\Al layered doubled oxide (LDO) samples with a layer-by-layer structure obtained from the downstream path exhibited high adsorption capacity for anionic species, i.e., acid red 27 (AR27) and methyl orange (MO) dyes through hydrogen bonding and electrostatic interaction. The adsorption behavior follows a pseudo-second-order model and the Langmuir isotherm, suggesting that chemisorption of adsorbate on the adsorbent surface plays a significant role. Zn\Al oxide (ZAO) powders prepared from the upstream path show high crystallinity, enabling them to photocatalytically degrade methyl blue (MB) dye solution under UV and visible light irradiation. The crystallization mechanisms for ZAO and LDO prepared by the MPT method were also proposed in this study. In summary, the MPT process is a facile, rapid, scalable, and cost-effective method for synthesizing of Zn\Al based materials for many practical applications.