An electro-peroxone-based multi-pronged strategy for the treatment of ibuprofen and an emerging pharmaceutical wastewater using a novel graphene-coated nickel foam electrode

Abstract

Conventional treatment technologies are inefficient in mineralizing emerging contaminants such as pharmaceuticals and personal care products (PPCPs), leading to their presence even in treated effluents. Such contaminants dwell in the water bodies for long, causing endocrine disruption and chronic toxicity to human and aquatic life. In this study, a novel three-dimensional graphene-coated nickel foam (Gr-NF) is explored for its performance in electro-peroxone process for the removal of ibuprofen, a non-steroidal anti-inflammatory drug and a model pharmaceutical contaminant. Furthermore, a benchmark study comparing the relative performance of the Gr-NF electrode, with a commonly used Reticulated Vitreous Carbon (RVC) electrode was carried out. In addition, the performance of electro-peroxone with two other common oxidation processes, viz. electrolysis and ozonation were critically compared.The Gr-NF electrode was subjected to several material characterization techniques to understand its structural and chemical characteristics. Typically, •OH radical generation can be achieved only during electro-peroxone. Here, interestingly, we observed •OH generation even during electrolysis using the Gr-NF electrode. Mineralization capacity of Gr-NF was found to be about two times that of RVC. Moreover, 87.0% mineralization of ibuprofen was achieved within 60 minutes. Mechanisms for in situ•OH generation are proposed. Degradation by-products of ibuprofen, along with their mechanisms were studied. The Gr-NF-based electro-peroxone system was also investigated for the treatment of a real pharmaceutical wastewater where it showed promise as a multi-pronged treatment strategy, with 75.0% TOC mineralization within 8 h, 99.7% disinfection within 5 minutes, 85.9% of decolorization, 78.0% of TSS removal within 180 minutes, and 85.0% removal of turbidity within 5 h. The study proves the enhanced performance of Gr-NF electrode over conventional ones such as RVC, along with enhanced capability of •OH radical generation, which makes it an attractive electrode for use in electro-peroxone.