Development of Palygorskite-CaIn2S4 composite for rapid Cr(VI) reduction under visible light

Using natural minerals to eliminate harmful Cr(VI) under sustainable sunshine has significant potential. Herein, Palygorskite nanorods were utilized as carriers for the in-situ synthesis of CaIn₂S₄ photocatalysts through a simple one-pot thermal process, enabling the efficient reduction of Cr(VI). With a Palygorskite to CaIn₂S₄ mass ratio of 5 %, the conversion rate of Cr(VI) reached 98 % after 60 min of visible-light exposure, with a remarkable reaction rate of 0.0633 min⁻¹. The effective integration of CaIn₂S₄ with Palygorskite led to a more uniform dispersion of CaIn₂S₄, exposing more reactive sites. Moreover, the establishment of a heterojunction between CaIn₂S₄ and Palygorskite facilitated the transport of photogenerated electrons from CaIn₂S₄, enhancing the efficiency of charge separation. These factors contribute to the improved photocatalytic performance. Additionally, the developed composite photocatalysts demonstrated excellent stability under light exposure and could be reused efficiently. Trapping tests on active substances revealed that e⁻ played key roles in the Cr(VI) reduction. This research suggests the potential of using natural minerals to fabricate composite photocatalysts capable of effectively removing pollutants from the environment using solar energy.