Environmental Life Cycle Assessment of marine sediment decontamination by citric acid enhanced-microwave heating

The potential ability of microwave heating (MWH) for the remediation of marine sediments affected by severe hydrocarbon (HC) contamination was investigated. Decontamination effectiveness and environmental sustainability through a comparative Life Cycle Assessment (LCA) were addressed. Main results revealed that the application of a 650-W MWH treatment resulted in a rapid (15 min) HC removal. A citric acid (CA) dose of 0.1 M led to enhanced-HC removals of 76.9, 96.5 and 99.7% after 5, 10 and 15 min of MW irradiation, respectively. The increase in CA dose to 0.2 M resulted in a shorter successful remediation time of 10 min. The exponential kinetic model adopted showed a good correlation with the experimental data with R2values in the 0.913–0.987 range. The nature of the MW treatment was shown to differently influence the HC fraction concentration after the irradiation process. Achieved HC removals in such a short remediation time are hardly possible by other clean-up techniques, making the studied treatment a potential excellent choice. Removal mechanisms, which allowed the enhanced-MWH to operate as a highly effective multi-step technique (pure thermal desorption + chemical washing), undoubtedly represent a key factor in the whole remediation process. The LCA highlighted that the MW technology is the most environmentally sustainable alternative for sediment decontamination applications, with a total damage, which was 75.74% lower than that associated with the EK (0.0503 pt).