Synthesis of Zn/Cu metal ion modified natural palygorskite clay - TiO2 nanocomposites for the photocatalytic outdoor and indoor air purification

Abstract In this work, natural palygorskite clay was coupled with TiO2 (anatase) nanocrystals to obtain nanocomposites, in order to be tested as photocatalysts for outdoor and indoor air de-pollution. Three types of palygorskite, i.e., untreated (P) and metal treated, namely Zn-modified (Zn-P) and Cu-modified (Cu-P) palygorskite, were firstly synthesized. Afterward, these three kinds of samples were loaded with 70 wt% TiO2 nanoparticles, using hydrothermal treatment with titanium isopropoxide, abbreviated as P-TiO2, Zn-P-TiO2 and Cu-P-TiO2 nanocomposites, respectively. The nanostructure of all samples was gingerly characterized using a series of spectroscopic and microscopy techniques, including XRD, XPS, ATR-FTIR, TEM, BET and DRS. The photocatalytic performance of the nanocomposites to the decomposition of air pollutants was evaluated in the oxidation of NOx and acetaldehyde under both UV and visible light illumination, while a direct comparison to the corresponding photocatalytic performance of the reference TiO2 photocatalyst (P25) was also made. The results showed that the nanocomposites can be significantly more effective than P25 in the oxidation of NOx under UV light (∼3 times higher) and acetaldehyde under visible light (∼2 times higher). The recorded activities, as well as the lower TiO2 demand, make the palygorskite-based nanocomposites very promising catalysts for both outdoor (NOx) and indoor (acetaldehyde) air purification.