Effects of the incorporation of Cr, Ni, Co, Ag, Al, Ni and Pt cations in titanate nanotubes (NTs) were examined on the NOx conversion. The structural and morphological characterizations evidenced that the ion-exchange reaction of Cr, Co, Ni and Al ions with the NTs produced catalysts with metals included in the interlayer regions of the trititanate NTs whereas an assembly of Ag and Pt nanoparticles were either on the nanotubes surface or inner diameters through an impregnation process. Understanding the role of the different metal cations intercalated or supported on the nanotubes, the optimal selective catalytic reduction of NOx by CO reaction (SCR) conditions was investigated by carrying out variations in the reaction temperature, SO2 and H2O poisoning and long-term stability runs. Pt nanoparticles on the NTs exhibited superior activity compared to the Cr, Co and Al intercalated in the nanotubes and even to the Ag and Ni counterparts. Resistance against SO2 poisoning was low on NiNT due to the trititanate phase transformation into TiO2 and also to sulfur deposits on Ni sites. However, the interaction between Pt2+ from PtOx and Ti4+ in the NTs favored the adsorption of both NOx and CO enhancing the catalytic performance.

Waste generated by the textile industry is one of the primary pollutants in aquatic environments. It is estimated that about 10 to 15% of the dyes used do not chemically interact with the fabric fibers, with a loss of this pollutant in the wastewater. One of the alternatives for pollutant removal is the adsorption process, which is viable compared to other separation methods. There is a range of materials that are used in adsorption processes. Among them, polysaccharides have numerous advantages regarding their use: they are non-toxic, abundant in nature, biodegradable, hydrophilic, and have several other properties. The study aimed to investigate a novel scaffold based on biopolymers and gallium-doped hydroxyapatite for dyes removal in an aqueous solution. The scaffold was characterized by X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy, and energy dispersive X-ray spectroscopy (SEM-EDS), swelling and adsorption tests. From the XRD, the gallium presence did not change the crystal structure of hydroxyapatite. The FTIR and TG spectra of the scaffold indicate that there were interactions between the precursor materials in the production of the same by shifting the characteristic bands and increasing thermal stability. SEM showed essential characteristics for the application of scaffolds in the adsorptive process through the presence of pores on the upper side and the inner surface of the scaffold. Open and interconnected pores with average diameters in the range of 60 mm on the upper and lateral face surface and 40 mm on the inside of the scaffold were observed. A more significant number of pores were observed inside, thus influencing the adsorption. In addition, EDS was possible to qualitatively prove the presence of precursor elements for the formation of the scaffold. It is concluded that the scaffolding was successful and showed excellent potential for removing Remazol Blue RGB and Remazol Red with adsorption of 341.41 ± 6.82 and 584.89 ± 23.39 mg/g, respectively.

In the original publication, there was a mistake in Figure 1 as published [...]

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