Solar-Powered Remediation of Carcinogenic Chromium(VI) and Methylene Blue Using Ferromagnetic Ni12P5 and Porous Ni12P5-rGO Nanostructures

Abstract

This study explores the potential of magnetic nickel phosphide (Ni₁₂P₅) and its porous reduced graphene oxide nanocomposite (Ni₁₂P₅-rGO) as photocatalysts for environmental remediation. A vibrating-sample magnetometer (VSM) was used to study the magnetic properties, resulting in the hysteresis loop indicating the ferromagnetic nature of the material. The materials were tested for their ability to reduce hexavalent chromium Cr(VI), a toxic pollutant, to the less harmful trivalent chromium Cr(III) under natural sunlight, using formic acid as a hole scavenger. The Ni₁₂P₅ and Ni₁₂P₅-rGO catalysts achieved complete Cr(VI) reduction in 160 and 130 min, respectively. Additionally, the photocatalytic degradation of methylene blue, a model organic pollutant, was investigated. The catalysts degraded 78.33% and 82.98% of a 10 mg/L methylene blue solution within 220 min. A mechanism for both the Cr(VI) reduction and methylene blue degradation processes is proposed. Reactive species trapping experiments were conducted to identify the primary active species, such as superoxide radical ($$), hydroxyl radical ($$), and photogenerated holes (h⁺), involved in the methylene blue degradation pathway.