Microspheres based on black sand mineral as a photocatalyst for photocatalytic hydrogen production under UV light

Abstract

Frequently, black sand from coastal deposits is a magnetic ore with a complex structure that is composed principally by iron, titanium and silica oxides, and metals such as vanadium, chromium, nickel, strontium, etc. This material could be used in oxidation/reduction processes as a photocatalyst doped naturally. However, its surface area low and the mass transfer constraints caused by the cluster formation in bulk reaction due to its magnetic character, limits the photocatalytic performance. Microspheres of black sand have been prepared by a simple associating method with alginate-Na and calcined under oxidizing atmosphere at 1100 °C. These have been characterized by XRF spectroscopy, scanning electron microscopy/energy dispersive X-ray spectroscopy, Brunauer-Emmett-Teller surface area analysis, XRD diffraction, N₂ adsorption/desorption measurements, FT-IR spectroscopy, differential thermal thermogravimetric analysis, and UV-Vis spectrophotometry. The catalytic activity for photocatalytic hydrogen production from EDTA solutions under UV light irradiation, using the response surface methodology in order to determine the optimum conditions of the process, has been tested. At calcination temperature, rounded microspheres with rough surface, have had apparent density different from the raw material and although the specific surface of the microspheres decreased owing to surface sintering, the chemical composition has been similar compared with the starting material. Due to their buoyancy in the suspension, the hydrogen production due to the contact between photons that entered into suspension and the as-prepared microspheres, has been favored.