Treatment of synthetic dye baths by Fenton processes: evaluation of their environmental footprint through life cycle assessment

Abstract

Inorganic and organic constituents present in textile effluents have a noticeable effect on the performance of Fenton processes. However, studies have been focused on simple wastewater matrices that do not offer enough information to stakeholders to evaluate their real potential in large-scale facilities. Chemical auxiliaries, commonly present in textile wastewaters (NaCl = 30 g/L, Na₂CO₃ = 5 g/L, and CH₃COONa = 1 g/L), affect both the economic and environmental performance of the process because they increase the treatment time (from 0.5 to 24 h) and the consumption of H₂SO₄ (657%) and NaOH (148%) during conditioning steps. The life cycle assessment (LCA) performed with the IPCC-2013 method revealed that dyeing auxiliaries increase from 1.06 to 3.73 (252%) the emissions of carbon dioxide equivalent (CO₂-Eqv/m³). Electricity consumption can be considered an environmental hotspot because it represents 60% of the carbon footprint of the Fenton process. Also, the presence of auxiliaries is critical for the process because it results in the increase of the relative impact (between 50 and 80%) in all environmental categories considered by the ReCiPe-2008 method. Chemical auxiliaries increased the costs of the treatment process in 178% (US$2.22/m³) due to the higher energy consumption and the additional reagent requirements. It is worthwhile mentioning that the technical simplicity of the Fenton process and its low economic and environmental costs turn this process into an attractive alternative for the treatment of textile effluents in emerging economies.

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