Demonstration of a feasible energy-water-environment nexus: waste sulfur dioxide for water treatment.

Sulfur dioxide (SO2) mitigation and water treatment are two key aspects towards a sustainable environment, and simultaneous achievement of these two goals is extremely attractive. Inspired by the iron ion catalyzed auto-oxidation of aqueous SO2 (i.e., Fe(II)/sulfite process), that generates intermediary sulfate radical able to oxidize organic compounds, we propose a feasible energy-water-environment nexus by using waste SO2 to alleviate water contamination. As a demonstration, electrolysis is used to assist Fe(II)/sulfite (i.e., electro/Fe(II)/sulfite) process to enhance contaminant removals. Results showed 91% of 10 μM ibuprofen (a nonsteroidal anti-inflammatory drug) contaminant at neutral pH was removed, due to sulfate radical oxidation. Synergy mechanisms of electro/Fe(II)/sulfite process were revealed. Moreover, the electro/Fe(II)/sulfite process could effectively degrade contaminants in water bodies from fields, indicating its promising practical application. Energetic analysis indicated that electric treatment cost is 8.65 cent/m3, and is affordable by most water treatment plants. Possible procedures to realize the proposed energy-water-environment nexus were also suggested. The strategy proposed in this study adds new value to the waste produced in energy production and will create renewed interest considering its potential use towards environmental treatment.