Photocatalytic Reduction of Cr(VI) with a PVA–Titanyl Hybrid Photocatalyst in a Plane Photoreactor

Poly(vinyl alcohol) is one of the commonly used polymeric matrices for the fabrication of photocatalysts due to its ability to form hybrid photocatalysts with titanium compounds. However, it has several limitations, including low strength and solubility in aqueous media. In the present work, poly(vinyl alcohol) was modified with the cross-linking agent TiOSO₄ to form a photocatalyst for Cr(VI) reduction, followed by Cr(III) precipitation. The photocatalyst was well characterized using SEM, IR, UPS, and XPS to describe its structure and the photoreduction mechanism that occurs due to the reversible transition between Ti(IV) and Ti(III) in the polymeric matrix. The formation of new Ti(III) states significantly increases light absorption, which is why the photocatalyst can be used for flow-mode water treatment. The photocatalytic flow plane reactor for Cr(VI) photoreduction was tested at different Cr(VI) concentrations from 5 to 400 mg·L^–1, at different wavelengths of 350, 400, and 500 nm, and in the pH range from 0.5 to 9.0. The Cr(III) solution obtained after photoreduction was used for pigment preparation. This work demonstrates the potential of the new photocatalyst for the efficient photoreduction of Cr(VI) in a flow-mode in-plane photoreactor.