Photocatalytic/sorption-self-cleaning activity of cellulose decorated with TiO2 and M@TiO2 (M=Au, Ag) polymeric nanocomposites

Titanium oxide nanoparticles (TiO2 NPs) are a semiconductor material widely employed as photocatalysts for environmental remediation owing to its excellent properties. Nevertheless, collecting the nanomaterial once dispersed in the aqueous media is challenging, while the photocatalytic activity is limited mainly to the ultraviolet range of radiation. In this work, we have modified cellulose paper, a sustainable and green support, with a polymer nanocomposite comprising nylon-6 and different nanomaterials, i.e., anatase TiO2 nanoparticles (NPs) as well as TiO2 decorated with Ag and Au in form of NPs by means of a simple procedure. The immobilization of the nanocomposite on paper mediated the subsequent recovery of the substrate upon incubation. The presence of nylon-6 enables both the attachment of the NPs on the support as well as the isolation of the pollutant from the contaminated water due to the interactions with the target analyte, i.e., methyl orange (MO). Additionally, the presence of the mentioned polyamide within the substrate triggers the photocatalytic reaction under visible light radiation. The broadening in the range of the light towards the use of sunlight has been also evaluated via modification of the photocatalyst nanoparticles with noble metals such as silver and gold. The kinetic of degradation of MO upon sunlight exposure with the different polymeric nanocomposites followed a pseudo-first-order model, with k constant values of 0.070, 0.083 and 0.120 min-1 for TiO2, Ag@TiO2 and Au@TiO2 nanocomposites, respectively. The effect of the presence of the polymer on the substrate has been evaluated, observing an increase in the k constant upon addition of the polyamide from 0.036 to 0.069 min-1 for TiO2. The synergistic effect of sorption/degradation enables the regeneration of the substrates modified with the nanomaterials that can be reused several times, the relative standard deviation of k upon three subsequent photocatalytic cycles being in the range 15.7- 37.7%.