2,4-Dichlorophenol Photodegradation by Novel Burtite-like Solid Solutions: Effect of Sn4 + and Al3 + Content on the Physicochemical Properties and Photocatalytic Performance

Abstract Nowadays, tailoring the physicochemical properties of novel photocatalysts is crucial for advanced environmental remediation technologies. Thus, in this work, novel solid solutions of burtite-like compounds with nominal Sn amounts of 5.3–27.8 mol % were synthesized. Materials were prepared by the co-precipitation method followed by a hydrothermal treatment. A material without tin was also prepared as a control, and all materials were characterized by X-ray powder diffraction, scanning electron microscopy, nitrogen adsorption–desorption at −196 °C, diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy. To verify their photocatalytic behavior, all samples were tested for the photocatalytic degradation of 2,4-dichlorophenol (a very toxic and recalcitrant pesticide) as a probe molecule. Aeroxide TiO2 P25 was also evaluated by means of comparison under the same experimental conditions. Results revealed that the amount of tin defined the crystalline phases found in the samples since compounds with low tin amounts (below 10%) produced mixtures of hydrocalumite, katoite, and burtite. On the other side, higher tin contents produced pure burtite-like phases. The obtained solid solutions were verified by cell parameter calculations and the absence of secondary crystalline phases. A new acicular morphology of burtite was obtained and assigned to the aluminum-rich solid solution. Photocatalytic experiments demonstrated that all synthesized materials were active under UV irradiation; however, the highest activity was achieved by the katoite/burtite composite (Al-B2), reaching an apparent DiPhe degradation of 54% after 30 min (estimated from UV–vis measurements), while TiO2 exhibited a degradation of 25%. Additionally, 75.5% mineralization was achieved after 2 h, while only 53.8% was attained with TiO2. The most active material was evaluated over six consecutive cycles, with photocatalytic activity dropping from 70% to 25% mineralization between the first and sixth runs due to a lixiviation process. Results demonstrated that burtite’s structure can be modified and its physicochemical characteristics can be adjusted to produce potential photocatalytic materials.