(86e) Graphene Coated Nickel Foam - a Novel Electrode for Electroperoxone Treatment of Emerging Pharmaceutical Contaminants

Over the years, the presence of pharmaceutical contaminants in water has increased rampantly, causing endocrine disruption and chronic toxicity to human and aquatic life. Conventional treatment technologies are unable to take it to complete mineralization which has resulted in their occurrence in treated effluents. This has raised the need for a competent tertiary treatment process. Although there are several effective technologies such as the advanced oxidation processes, they have several disadvantages such as use of chemicals, sludge formation and/or generation of degradation by-products which necessitates post-treatment involving high costs. Others are hindered by their inability to be retro-fitted to an existing treatment plant. In this study, we use electroperoxone which overcomes most of these demerits. A novel electrode, ‘3D Graphene-coated Nickel Foam (GrNF)’ is explored for its performance in electroperoxone and electrolysis processes for the removal of ibuprofen, a non-steroidal anti-inflammatory drug and a model pharmaceutical contaminant. Firstly, a benchmark study comparing relative performance of the GrNF electrode, with a commonly used Reticulated Vitreous Carbon (RVC) electrode was carried out, for the removal of total organic carbon (TOC). In addition, we critically compared the performance of electroperoxone with two other common oxidation processes, viz. electrolysis and ozonation.

Typically, ^.OH radical generation (required for complete TOC mineralization) can be achieved only in the presence of Fe²⁺, ozone or a catalyst. Here, interestingly, we observed ^.OH radical generation during electrolysis using GrNF electrode, without the need for ozone, mechanisms for which will be discussed. Electrolysis using RVC electrode yielded a TOC removal of only 19%, while the use of GrNF electrode yielded a removal of 28% in 120 minutes. For the case of electroperoxone, complete mineralization of TOC is achieved within 120 minutes. In addition, optimization of H₂O₂ generation under conditions such as varying aeration rates, applied current, electrode surface area and solution pH was performed. We thus show that the enhanced performance of GrNF electrode over conventional ones such as RVC, along with capability of ^.OH radical generation in the absence of ozone, makes it an attractive electrode for use in electroperoxone.