Accelerating Surface Photoreactions Using MoS 2 -FeS 2 Nanoadsorbents: Photoreduction of Cr(VI) to Cr(III) and Photodegradation of Methylene Blue.

Nanocubic MoS ₂ -FeS ₂ , as a photocatalyst, was synthesized with high catalytic active edges and high specific surface areas with the capability of absorbing visible light. The results showed that the photocatalytic efficiency of nanocubic MoS ₂ -FeS ₂ for adsorption/degradation of methylene blue (MB) as well as the reduction of Cr(VI) was high. The adsorption process was found to follow a kinetic model of a pseudo-second-order kind ( Q _e.cal = 464 mg g ^-1 ) along with an isotherm described by the Langmuir model with Q _e.cal = 340 mg g ^-1 . The photodegradation process was achieved by holes. It was found that the photodegradation rate constant of MB by MoS ₂ -FeS ₂ (0.203 min ^-1 ) was about 22 times higher than that of MoS ₂ (0.0091 min ^-1 ). The percent apparent quantum yield for photoreduction of Cr(VI) to Cr(III) using MoS ₂ -FeS ₂ (5.7%) was about 33 times higher than utilizing MoS ₂ (0.1709%). Therefore, the synergistically prolonged visible-light harvesting as well as the photocarrier diffusion length proved that MoS ₂ -FeS ₂ nanotubes can effectively be utilized in environmental pollutant's remediation.