Comparative organic pollutants removal efficiency and life cycle assessment of pyrolysis and solvent elution for industrial waste salt recycling

Managing industrial waste salt plays a vital role in environmental protection and resource utilization, with a focus on effective removal of organic pollutants and comprehensive life cycle assessment. This study focuses on waste salt produced by the pharmaceutical, pesticide, fluorochemical, and dyeing industries, assessing the efficiency of pyrolysis and solvent elution techniques in removing organic pollutants. Additionally, a life cycle assessment (LCA) was conducted to assess the environmental impacts associated with the two technologies. The findings reveal that pyrolysis significantly enhances the removal of organic pollutants, offering an average improvement of 19.37% over the solvent elution method. This improvement is particularly notable in the treatment of waste salt from agricultural and textile industries, where removal rates exceed 90%. Moreover, ammonium-based waste salts produced by the dyeing industry, due to their lower thermal stability and reduced pyrolysis yield, are more suitable for solvent elution. The LCA indicates that pyrolysis results in less overall environmental risk compared to the solvent elution process. In terms of carbon emission potential, pyrolysis technology emits less carbon dioxide equivalent (CO2 eq.), with a total of 1144 kg CO2 eq. emitted when processing one ton of waste salt. The environmental impact of pyrolysis is primarily attributed to the energy consumption during the pyrolysis and evaporation stages. In contrast, the environmental impacts of solvent elution are mainly related to the use of toxic eluents and the high energy consumption of the subsequent distillation to recover the solvent.