Treatment of methylene blue wastewater with nano-PbCrO4 photocatalyst prepared from chromite ore processing residue

Chromite ore processing residue (COPR) is an environmental threat due to its content of Cr (Ⅵ) which is a highly toxic substance. However, some metallic elements in COPR can create the intrinsic values of COPR. In this study, the nano-lead chromate (PbCrO4) was prepared by the chemical precipitation method for the water-soluble Cr (VI) leachate obtained by the simple water washing of COPR and the use of methylene blue (MB) degradation. Results demonstrated that the prepared lead chromate had good photocatalytic performance and stability. The degradation rate of MB was 76.78% with the conditions of the initial pH was 6, the initial concentration was 10 mg/L, the reaction time was 80 min, and the photocatalyst dosage was 1.0 g/L. Moreover, recycling results displayed that the degradation rate remained at 62.91% after five cycles which means it can be recycled. Meanwhile, the concentration of Cr (VI) in COPR decreased from 34.7 to 1.4 mg/L which is below the national emission standard of China (GB 5085.3–2007), that is 5 mg/L, achieving harmless treatment of COPR. Consequently, this study provides a new tactic for the resource utilization of COPR, and implements the governance concept of “waste control by turning waste into treasure”.